Report of Committee on Chemicals and Explosives - NFPA...ardousChemicals Data, NFPA No. 49 -- 1966. " Part VI has been submitted to ballot of the Sectional Committee on Prop- erties

124 C O M M I T T E E ON C H E M I C A L S AND E X P L O S I V E S

Report of Committee on Chemicals and Explosives

Correlating Committee

Dr. Rober t W. Van Dolah, Chairman, Explosives Research Center, Bureau of Mines, U. S. Department of the Interior,

4800 Forbes Ave., Pittsburgh, Pa. 15213

Ches te r !. Babcockt , Secretary, National Fire Protection Assn., 60 Batterymareh St., Boston, Mass. 02110

Char les W. Bahme , Northridge, Calif.

W. H. Doyle, Factory Insurance Assn.

T h o m a s E. Duke, Fire Prevention & Engi- necring Bureau of Texas.

Dr. Richard Y. Le Vine, Olin Mathie~n Chemical Corp.

I t e n r y T. R i t t m a n , Institute of Makers of Explosives.

Ru~meH H. Scott, Battelle-Northwest.

SCOPE: Tiffs committee serves as a policy-making and correlating group to administer and process reports of the various sectional committees dealing with chemicals and exploeives.

Sectional Committee on Electrical Equipment in Chemical Atmospheres

Dr. Richard Y. Le Vine, Chairman, Olin Mathieson Chemical Corp., 460 Park Avenue, New York, N. Y. 10022

Ches ter I. Babcockt . ,Secretary, National Fire Protection Association, 60 Batterymarch Street, Boston. Ma~. 02110

Samue l P. Axe, American Petroleum In- stitute. (Alternate to Robert P. Howell.)

Wil l iam J. Bradford, Esso Research and Engineering Co.

Har lan Bratvold, ' Underwriters' Laborato- ries, Inc. (Alternate to W. C. Westerberg.)

Clyde L. Brown, U. S. Dept. of the Interior. T h o m a s E. Duke, Fire Prevention & Engi-

neering Bureau of Texas. Reynold J . Green, Manufacturing Chem-

ists' Assn., Inc. Willis F. Il ickes, Instrument Society of

America. (Alternate to F. L. Maltby.) Rober t P. Ilowell, American Petroleum

Institute. George O. I l u n t , Jr . , Manufacturing

Chemists' Assn., Inc. (Alternate to R. J. Green.)

A. E. Krawcek, National Electrical Manu- facturers Assn.

Paul C. L a m b , Lever Brothers Co.

Frederick L. Maltby, Instrument Society of America.

Lewis C. Mat thews , Compre~ed Gas Aun., Inc.

J o h n E. Rofierson, Procter & Gamble Co.

R. F. Sch~vab, Factory Insurance A~ss. (Alternate to F. J. Zeleny.)

Wil l iam C. Weaterber~, Underwriters' Laboratories, Inc.

Frederick J. Zeleny, Panel No. 14, National Electrical Code Committee and Factor3' Insurance Assn.

ScoPE: (1) To develop data on the properties of chemicals enabling proper selection of electrical ectuipment for use in atmospheres containing flammable gases, vapors or dusts; (2) to make recommendations for the prevention of liras and explosions through the use of intrinsically safe, continuously purged, pressurized, explosion-proof, or dust ignition-proof electrical equipment when installed in such chemical atmospheres.

tNon-voting.

IV

C O M M I T T E E ON C H E M I C A L S AND E X P L O S I V E S

125

Sectional Committee on Properties of Hazardous Chemicals

T h o m a s E. Duke, Chairman, Fire Prevention & [',nginecring Bureau of Texas, 520 Mercantile Securities Bldg.,

Dallas, Texas 75201

Chester !. Babcockt , Secretary, National Fire Protection Association, 60 Batterymarch Street, Boston, Mass. 02110

Douglas R. Abbey, I)on Mills, Ont., Canada. charles W. Bahme , Northridge, Calif. u . thur G. Baker, Mutual Fire Assn. of

New England. ~fatbew M. Braidech, American Chemical

Society. R. E. Dufour, Underwriters' Laboratories,

IBC. william E. G r u b e r t , Conference of Special

Risk Underwriters. paul D. l lal ley, American Petroleum In-

stitute. joseph A. I l ough ton , Liberty Mutual Ins.

Co.

Rober t W. Kiefer, Union Carbide Corp. Dr. Richard Y. Le Vine, Manufacturing

Chemists' Assn., Inc. Rudolph Schmid t , J r . , American Insur-

ance Assn. Russell H. Scott, Battelle-Northwest. Char les J. Shukes, Illinois Inspection &

Rating Bureau. Char les B. Smi th , U. S. Coast Guard. Wil l iam H. Van A r n u m , Western Electric

Company, Inc. Dr. Rober t W. Van Dolah, U. S. Depb.rt-

ment of the Interior.

ScorE: To compile information on hazardous chemicals and develop recommended fire lLz~srd ratings of chemicals.

Sectional Committee on Storage, Handling, and Transportation of Hazardous Chemicals

Will iam H. Doyle, Chairman, Factory Insurance Association, &5 Woodland St., Hartford, Conn. 06102

Chester I. Babcockt , Secretary, National Fire Protection Association, 60 Batterymarch Street, Boston, Mass. 02110

C a p u t . l lewle t t R. Bishop, National Cargo reau, Inc.

Win. J. Bradford, American Petroleum In- stitute.

A. C. Clark, Manufacturing Chemists' Assn.

Reynold J . Green, Manufacturing Chemists' .~n . . Inc.

Batt. Chief J a m e s M. } l am m ack , Fire Marshals Assn. of North America.

Jmeph A. l loul lh ton , Liberty Mutual Fire Ins. Co.

P. E. Johnson , Factory Mutual Eoginecr- ing Corporation.

Robert W. Kiefer, Union Carbide Corp. Dr. Richard Y. Le Vine, Olin Mathieson

Chemical Corp. Capt. E. D. Lindell , National Cargo Bu-

reau, Inc. (Alternate to Capt. Hewlett R. Bishop.)

S. 11. MacPherson, Fire Marshals Assn. of North America.

Frankl in J . McClain, Factory Insurance Assn. (Alternate to W. H. Doyle.)

Dr. W. G. McKenna , Bureau of Explosives. Roy Peteracn, American Assn. of Port Au-

thorities. Samue l J . Porter , Arlington, Va. Eric Schackleton, Cnderwriters' Labora-

Wries of Canada. I f e r m a n H. Spaeth , Pacific Fire Rating

Bureau. A r t h u r Splefielman, American Insurance

Assn. Donald S t romquis t , Manufacturing Chem-

ists' Assn.. Inc. (Alternate to A. C. Clark.) Paul T. T r u i t t , National Plant Food Insti-

tute. Dr. Rober t W. Van Dolah, U. S. Dept.

of the Interior.

SCOPE: To develop and maintain current codes for classes of hazardous chemicals and codes fur specific chemicals when these are warranted by virtue of widespread distribution or special I~ards.

tNon-voting.

126 C O M M I T T E E ON C H E M I C A L S A N D E X P L O S I V E S

A. R i c h a r d A l b r e c h t , Manufacturing Chemists' Assn., Inc.

Dr. G l e n n H. D a m o n , U. S. Dept. of the Interior,

B a t t . Ch ie f J a m e s M. H a m m a c k , Fire Marshals Assn. of North America.

A. S. Hil l , Sporting Arms and Ammunition Manufacturers ' Institute.

H. L. J o n e s , Munitions Carriers Conference, Inc.

Dr. W. G. McKenna, Bureau of Explosives.

Sectional Committee on Explosives

" "Henry T. R l t t m a n , Chairman, E. I. duPont de Nemours & Co., 6502 Nemours Bldg., Wilmington, Del. 19898

(Rep. Institute of Makers of Explosives)

C h e s t e r I. B a b c o c k t ; Secretary, National Fire Protection Association, 60 Bat terymarch Street, Boston, Mass. 02110

R. W. Obe rho l t z e r , Inst i tute of Makers of Explosives.

Samuel J. Porter, Gulf Oil Corp~ James D. Reilly, American , Mining

Congress. Lawrason Rigl~s III, American Mining

Congress. R. F. Schwab, Factory Insurance Assn. Major Carroll E. Shaw, Fire Marshals

Assn. of North America. Dr. R o b e r t W. Van Do lah , U. S. "Depart.

ment of the Interior,

ScopE: To develop and maintain current codes for explosives and related materials.

The report of the Committee on Chemicals and Explosives is in nine parts:

Part I, prepared by the Sectional Committee on Explosives, proposes tentative adoption of a draft of a Standard on Recom- mended Separation Distances of Ammonium Nitrate and Blasting Agents from Explosives or Blasting Agents, NFPA No.o 492-PT.

Part I has been submitted to ballot of the Sectional Committee on Ex- plosives, which consists oJ 14 voting members, of whom /2 have voted affirmatively. Messrs. McKenna and Reilly have not returned: ballots.

Part I has also been submitted to ballot of the Correlating Committee, which consists of 7 voting members, of whom all have voted affirmatively.

Part II, prepared by the Sectional Committee on Explosives, proposes adoption of amendments of the Code for the Manu- facture, Transportation, Storage, and Use of Explosives and Blast- ing Agents, NFPA No. 495-1965.

Part II has been submitted io ballot of the Sectional Committee on Ex- plosives, which consists of 14 voting members, of'whom 12 have voted affirmatively. Messrs. Oberholtzer and Reilly have not returned ballots.

Part H has also been submitted to ballot of the Correlating Committee, which consists of 7 voting members, of whom all have voted affirmatively.

127 C O M M I T T E E ON C H E M I C A L S AND E X P L O S I V E S

part III, prepared by the Sectional Committee on Explosives,

~ roposes adoption of amendments of the Standard for the Storage d Handling of Cellulose Nitrate Motion Picture Film, NFPA No.

0 ~ 1962.

part 1II has been submitted to ballot of the Sectional Committee on Ex- plosives, which consists of 14 voting members, of whom 11 have voted affirmatively. Mes'srs. .]ones, Oberholtzer and Reilly have not returned ballots.

Part l l I has .also been submitted to ballot oJ the Correlating Committee, which consists of 7 voting members, of whom all have voted affirmatively.

par t IV, prepared by the Sectional Committee on Explosives, proposes reconfirmation of the Standard for the Storage, Handling and Use of Pyroxylin Plastics in Factories Making Articles There- from, NFPA No. 42 - - 1962.

Part IV has been submitted to ballot of the Sectional Committee on Ex- plosives, which consists of 14 voting members, of whom I2 have voted affirmatively. Messrs. Oberholtzer and ReiUy have not returned ballots.

Part IV has also been submitted to ballot of the Correlating Committee, which consists of 7 voting members, of whom all'have voted affirmatively.

Part V, prepared by the Sect ional Committee on Explosives, proposes reconfirmation of the Standard for the Storage, Handling and Use of Pyroxylin Plastic in Warehouses and Wholesale, Jobbing and Retail Stores, NFPA No. 4 3 - - 1962.

Part V has been submitted to ballot oJ the Sectional Committee on Ex- plosives, which consists of 14 voting members, of whom 72 have voted affirmatively. Messrs. Oberholtzer and Reilly have not returned ballots.

Part V has also been submitted to letter ballot of the Correlating Com- mittee, which consists oJ 7 voting members, of whom idl have voted affirmatively.

Part VI, prepared by ihe Sectional CommiRse on Properties of Hazardous Chemicals, proposes adoption of amendments of Haz- ardousChemicals Data, NFPA No. 49 - - 1966. "

Part VI has been submitted to ballot of the Sectional Committee on Prop- erties of Hazardous Chemicals, which consists of 17 voting memberi, of whom 15 have voted affirmatively. Messrs. Abbey and Ki~er have not returned ballots.

Part VI has also been submitted to ballot of the Correlating Committee, which consists oJ 7 voting members, oJ whom all have voted affirmatively.

128 COMMITTEE ON CHEMICALS AND EXPI. ,OSIV~.S

Part VII, prepared by the Sectional Committee on Storage Handling and Transportation of raazaraous ~nemicals, propo~s~'s adoption of amendments of the Code for the Storage of Ammonium Nitrate, NFPA No. 490 - - 1965. ._

Part VII has been submitted to ballot of the Sectional Committee on Storage, Handling and Transportation of Hazardous. Chemicals, which consists of 19 voting members, of whom 14 have voted affirmatively on all items. Mr. Spiegelman voted affirmatively except on Item 7; he voted nega. tively on Item 7. Mr. MacPherson voted affirmatively "on all items except Item 6; he did not return a ballot on Item 6. Mr. Spaeth voted affirmatively on Item 6; he did not return a ballot on the other items. Messrs. BradJord and Kiefer did not return ballots on any items.

Part VII has also been submitted to letter ballot of the Correlating Com- mittee, which consists of 7 voting members, of whom all have voted affirma. tively on all except item 6.

Part VIII, prepared by the Sectional Committee on Elec- trical Equipment in Chemical Atmospheres, proposes official adoption of an amended draft of the Tentative Standard. for Purged and Ventilated Enclosures for Electrical Equipment in Hazardous Locations, NFPA No. 496-T - - 1966.

Part VII I has been submitted to ballot of the Sectional Committee on Electrical Equipment in Chemical Atmospheres, which consists of 13 voting members, of whom 11 voted affirmatively and I voted negatively (Krawcek). Mr. Bradford did not return his ballot.

Part VII I was also submitted to ballot of the Correlating Committee, which consists of 7 members, of whom all have voted affirmatively.

Part IX, prepared by the Sectional Committee on Electrical Equipment in Chemical Atmospheres, proposes tentative adop- 'tion of the draft of a Standard for Intrinsically Safe Process Control Equipment for Use in Hazardous Locations, NFPA No. 493-PT.

Part I X has .been submitted to ballot of the Sectional Committee on Elec- trical Equipment in Chemical Atmospheres, which consists of 13 voting members, of whom l l have voted affirmatively. Messrs. Bradford and Matthews did not return ballots.

Part I X has also been submitted to ballot of the Correlating Committee, which consistsof 7 voting members, of whom all have voted affirmatively.

DERIVATION OF TABLE

129 492-3

P a r t - I

P R O P O S E D T E N T A T I V E R E C O M M E N D E D .

sEPARATION DISTANCES OF AMMONIUM NITRATE AND BLASTING AGENTS FROM EXPLOSIVr~S OR

BLASTING AGENTS NFPA No. 4 9 2 - P T - - 1967

1. D E R I V A T I O N O F T H E T A B L E

11. A test p rogram sponsored by industry with cooperat ion of the Manufactur ing Chemists' Association and the Institute of Makers of Explosives and conducted by the Bureau of Mines I developed data on the relative sensitivity of a m m o n i u m nitrate (AN) and ammonium nitrate-fuel oil (ANFO) to sympathetic detonation. These data were applied to the existing American Table of Distances for Storage of Explosives 2 to develop the following table of recommended separation distances for a m m o n i u m nitrate and blasting agents a from stores of high explosives or blasting agents.

12. The American Table of Distances for barr icaded storage of explosives l~as been proven adequatc through the years, and no data were developed in the test programs that would suggest tha t this table should be modified for explosives. On the other hand, a factor of 2 has been suggested in the past for increasing the distances listed in the American Table of Distances when the magazines are unbarricaded. The results, employing two charge sizes of AN and one charge size of A N F O , gave ratios of barr icaded to unbarr icaded distances of 4.2 to 7.4, for an average of about 6 which was taken as the appropr ia te factor. Thus, unbarr icaded stores of AN or A N F O not in bullet-resistant magazines should have 6 times the separation distances as barr icaded stores.

IReport of Investigations 6746, Sympathetic Detonation of Ammonium Nitrate and Ammonium Nitrate-Fuel Oil, by R. W. VanDolah, F. C. Gibson and J. N. Murphy.

Report of Investigations 6903, Further Studies on Sympathetic Detonation, by R. W. VanDolah, F. C. Gibson and J. N. Murphy.

2American Table of Distances for Storage of Explosives, Pamphlet 2, Institute of Makers of Explosives, Rev. Sept. 30, 1955. Also printed in Appendix A of NFPA No. 495, Code for the Manufacturing, Transportation, Storage, and Use of Explosives and Blasting Agents.

3For a definition of "blasting agent" and regulations for reasonable safety in the manufacture, storage, transportation and use of blasting agents, see NFPA No. 495, Code for the Manufacture, Transportation, Storage and Use of Ex-

• plosives and Blasting Agents.

130 492-4 S E P A R A T I O N AN & A N F O F R O M A N F O OR E X P L O S I V E s

13. The relative sensitivity of AN and ANFO to dynamite was ob. tained by examining the relative K factors for 50 percent propa. gation distances when the cube root of the weight was employed in the usual equation: , ,

S = KWS/3 This equation allowed comparison of 1,600-pound dynamite ae. ceptors with 5,400-pound AN and ANFO acceptors; results from these large charges are believed to be the most reliable available. The ratio of K factors for dynamite and AN was 6.27 which was rounded to 6; the ratio for dynamite and ANFO was 1.6. These factors were applied to the American Table of Distances by thus reducing the distance for barricaded ammonium nitrate to 1/6 the corresponding distance for explosives in the American Table of Distances and for ANFO to 6/10. '~'

14. One point should be emphasized; the distances in the table are for separation of stores only. No change should be made in the American Table of Distances with respect to inhabited buildings, passenger railways, and public highways, as the blast effect from ANFO is not importantly less than for high explosives, but the blast effect from AN is about one-half that from high explosives. The blast effect is little modified by the presence of barricades, but the factor of 2 suggested in the American Table of Distances for separation of ,stores from inhabited buildings, passenger railways, and public highways for Unbarricaded stores provides an addi- tional safety factor and should be retained.

t

131 TABLE OF SEPARATION DISTANCES 492--5

TABLE OF _RECOMMENDED SEPARATION DISTANCES OF AM- MONIUM NITRATE AND BLASTING AGENTS FROM EXPLOSIVES

OR BLASTING AGENTS l" '

" - - -Donor Weight Minimum Separation Distance . oJ Receptor when Barricadea n (ft.) Minimum Thickness of

Pounds Pounds Amnionium . . . . . Artificial Barricade# Over Not Over Nitrate s Blasting Agent ~ (in.)

100 300 600

1,000

100 • 3

300 4 600 5

t ,000 6 1,600 -, 7

i l 14 18 - . 22 25

12 12 12 12 12

1,600 2,000 3,000 4,000 6,000

2,000 3,000

• • 4,000 6,000 8,000

. 8

9 :'10

11 12

29 32 36 40 43

12 15 15 15 20

8,000: ". 10,000 " 10,000. 12,000

1 2 , 0 0 0 " 1 6 , 0 0 0 16,000 '20,000 20,000 25,000

13 14 1 5 16 18

47 50 54 58 65

20 20 25 25 25

25,000 30,000 30,000 ' '35,000"; 35,000.,- 40,000.. 40,000 45,000 45,000 50,000

19" 20

, 21 22 23

:68 72 ," .76 . .. ,. 79

..83

30 30 30 35 35

50,000 55,000 55,000 60,000 60,000 .70,000 70,000 80,000 80,000 90,000

24 25 26

.. 28 30

86 90 94

101 108

'35 35 40 40 40

90,000 100,000 100,000 . 120,000 120,000 140,000. 140,000 160,000 160,000 180,000

32 34 37 40 44

115 122 133 144 158

40 50 50 50 50

180,000 200,000 200,000 220,000 220,000 250,000 250,000 275,000 275,000 300,000

48 52 56 60 64

173 187

202 216 230

50 60 60 60 60

132 492-6 SEPARATION AN & ANFO FROM ANFO OR EXPLOSIVES

Notes to Table o f Recommended Separation. Distances of Ammonium Nitrate and Blasting Agents from

Explosives or Blasting" Agents

NOTE 1 - - Recommended separation distances to prevent explosion of ammonium nitrate and ammonium nitrate based blasting agents by propagation from nearby stores of high explosives or blasting agents referred to in the Table as the "donor". Ammonium nitrate, by itself, is not considered to be a donor when applying this Table. If stores of ammonium nitrate are located within the sympathetic detonation distance of explosives or blasting agents, one-half the mass of the ammonium nitrate should be included in the mass of the donor. These distances allow for the possibility of high velocity metal fragments from mixers, hoppers, truck bodies, sheet metal structures, metal containers, and the like which may enclose the "donor".

These distances apply to the separation of stores only. The American Table of Distances shall be used in determining separation distances from inhabited buildings, passenger railways and public highways.

NOTE 2 - - When the ammonium nitrate and/or blasting agent is notbarricaded, the distances shown in the Table shall be multiplied by six. Where storage is in bullet-resistant magazines* recommended for explosives or where the storage is protected by a bullet-resistant wall, distances and barricade thicknesses in excess of those prescribed in the American Table of Distances are not required.

NOTE 3 - - The distances in the table apply to ammonium nitrate that passes the insensitivity test prescribed in the definition of ammonium nitrate fertilizer promulgated by the National Plant Food Instituter; and ammoniu m nitrate failing to pass said test shall be stored at separation distances "determined by competent persons and approved by the authority having jurisdiction..

NOTE 4 - - These distances apply to nitro-carbo-nitrates and blasting agents which pass the insensitivity test prescribed in the ICC regulations.

NOTE 5 - - Earth, or sand dikes, or enclosures filled with the prescribed minimum thickness of earth or sand are acceptable artificial barricades. Natural barricades, such as hills or timber of sufficient density that the surrounding exposures which require protection cannot be seen from the "donor" when the trees are bare of leaves, are also acceptable.

NOTE 6 - - When the ammonium nitrate must be counted in determining the distances to be maintained from inhabited buildings, passenger .railways and public highways, it may be counted at ~ its actual weight because its blast effect is lower.

*For construction of bullet-resistant magazines see Chapter 3 of NFPA No. 495, Code for the Manufacture, Transportation, Storage, and Use of Explosives and Blasting Agents.

tDefinition and Test Procedures for Ammonium Nitrate Fertilizer, National Plant Food Institute, November 1964.

G U I D E T O U S E O F T A B L E

133 492-7

2. G U I D E T O USE OF T A B L E OF REi3OMMENDED SEP- ARATION DISTANCES OF A M M O N I U M N I T R A T E AND B L A S T I N G A G E N T S FROM E X P L O S I V E S OR BLASTING AGENTS

21. Sketch location of all potential donor and acceptor materials together with the maximum mass of material to be allowed in that vicinity. (Potential donors are high explosives and blasting agents. Potential receptors are high "explosives, blasting agents, and ammonium hitrate.)

22. Consider each clonor mass separately in combination with each receptor mass. If the masses are closer than table allowance (distances measured from the center of mass), the combined masses become a new potential donor of weight equal to their total mass, and distance measured to their center of mass.

Calculation of distance'from.combined masses: :

Let M2, M3 .... Mn be donor masses to be combined. Mt is a potential receptor mass. D12 is distance from MI to M~. D , is distance from M1 to M3, etc.

Find distance [D1(2,8, . . . . . )] from combined masses to Ma

M2 X D12 + M3 X DI3....+M,~ X Dr. Dl(2,a,....n) =

M~ + M8 .... + M , (1)

23. In determining the distances separating highways, railroads, and inhabited buildings from potential explosions (as prescribed in the American Table of Distances), the sum of all masses which may propagate (i.e., lie at distances less than prescribed in the Table) from either individual or combined donor masses are included. How- ever, when the ammonium nitrate must 'be included, only 50 percent of its weight shall be used b~cause of its reduced blast effects.

24. When all or part of a potential receptor comprises Explosives Class A as defined in ICC regulations, storage in bullet-resistant magazines is required. Safe distances to stores in bullet-resistant magazines may be obtained from the intermagazine distances prescribed in the Americ~in Table of Distances.

25. Barricades must not have line-of-sight openings between potential donors and receptors which permit blast or missiles to move directly between masses.


D I s

F ;Ola ~,s

I I

q¢.

A N g O M ~ ¢ (Ma)

I I L.J

,p, ota, q A ~ , a

C ' ~ ' , ) , \..

' r "1 IOrHE~ Sro~A¢¢ I

w~o, lrv(/.t~) , ! I

V. ".

F i g u r e 1.

. 2

Example 1 ANFO Mix P l an t (Figure 1)

MI 100,000 lbs. Fertilizer AN Prills (maximum) M~ " .2 ,500 lbs. ANFO (maximum) M~ 80,000 lbs. ANFO (maximum)

Dx2 30 ft. ""

D2a 40 ft.

Dis. 70 ft. No other stores on site; no barricade exists.

Distance Potent ia l Potent ia l On Site

Donor Receptor (ft.) M~ (2,500 lbs.) MI 30 M~ (2,500 lbs.) Ma . 40 M8 (80,000 lbs.) M] 70 Ms (80,000 lbs.) M~ 40

Table Distance, - Pro pa- M i n i m u m - gat~on

Requi red (ft.) Possible? 9 X 6 = 54 Yes

32 X 6 = 192 Yes 28 "X 6 -- 168 " Yes

101 X 6 = 606 Yes

GUIDE TO USE OF TABLE 135

4 9 2 - 9

Conclusion: The maximum amount of blasting agent to be considered for public pro-

tection at this site is sum of all masses, reducing Fertilizer AN mass by 50 percent as indicated in Paragraph 23.

100,000 X 50% = 50,000 ~. 2,500

80,000

132,500 pounds

Example 2 ANFO Mix Plant (Figure 1)

Mt 100,000 lbs. Ferti l izer AN Prills (maximum) M2 2,500 lbs. A N F O (maximum)" Ma 80,000 lbs. A N F O (maximum)

DI~ 30 ft. " D2a 40 ft. Dla 70 ft.

No other stores on site; a 4-foot-thick ear th barricade exists at B (Figure 1).

Distance Potential Potential On Site

Donor Receptor (ft.) M2 (2,500 lbs.) Mt 30 M~ (2,500 lbs.) M~ 40 M3 (80,000 lbs.) M, 70 M8 (80,000 lbs.) M2 40 Combined M2:1- Ma

(82,500 lbs.) Ml 69*

Conclusion:

Tab le Dis tance, P r o p a - M i n i m u m gaUon

Required (ft.) Possible? 9 No

6 X 32 = 192 Yes 28 No

6 X 101 = 606 Yes

30 No

The inaximum amount of blasting agent to be considered for public protection at this site is the sum of M2 plus M3 or 82,500 pounds.

*Compute distance to center of mass by equat ion 1 :

2,500 X 30 -t- 80,000 X 70 = 69 feet

2,500 + 80,000


Example 3

M1 M~ M3

Dtz D2a Dr3

ANFO Mix Plant and Warehouse (Figure 1)

200,000 lbs. Fertilizer AN Prills (maximum) 90,000 ibs. ANFO storage (maximum) 50,000 lbs. ANFO (maximum)

25 ft. 50 ft. 75 ft.

No other stores on site; a 4-foot-thick earth barricade exists at B (Figure 1).

Distance Table Distance, Propa- Potential Potential On Site Minimum gauon

Donor Receptor (ft.) Required (ft.) Pnssiblel/ M~ (90,000 lbs.) Mt 25 30 ' Yes ~ M~ Ma 50 108 X 6 = 648 Yes M3 (50,000 lbs.) M~ 50 83 X 6 = 498 Yes Ma Ml 75 23 No Combined M~ + Ma

(140,000 lbs.) Ml" 43* 37 No

Conclusion: Note that while the combined ANFO masses give a "no" answer for propa-

gation to the prills, the nearest ANFO mass gives a "yes". Therefore, the maximum amount of blasting agent to be considered for public protection must include one-half the prill mass (240,000 pounds).

*Compute distance to center of mass by equation 1 -

90,000 X 25 + 50,000 X 75 = 43 feet

90,000 + 50,000

137 GUIDE TO USE OF TABLE 4 9 2 - 1 1

Example 4

MI

M~ Ms M4

DI2

D~3 D~3

ANFO Mix P l a n t wi th Explosives Storage Nearby (Figure 1)

200,000 lbs. Fertilizer AN (maximum) 2,500 lbs. ANFO (maximum)

80,000 lbs. ANFO (maximum) 100,000 lbs. Dynamite and ANFO mixed storage in approved

bullet-resistant magazine

30 ft. Ds4 300 ft. 40 ft. D~, 330 ft. 70 ft. Dl~ 360 ft.

A 5-foot-thick earth barricade exists at B ; explgsives magazine is unbarricadecl.

Potential Potential Donor Receptor

M~ MI Ms Ma M3 Ml Ms M~ M~ + M3 M1 M2 (2,500 lbs.) M~ Ms (80,000 lbs.) M4 M~ + Ma (82,500 lbs.) M4 M~ (100,000 lbs.) M3 M~ Mt Combined

Mi + Ma + M4 (182,500 lbs.)

Distance Table Distance, Propa- Site Minimum gaUon

O(ft. ) n Requi red (~.) Possible?

30 9 No 40 6 X 32 = 192 Yes 70 28 No 40 6 X 101 = 606 Yes 69** 30 N O

330 *2 X 49 = 98 No 300 *2 X 165 = 330 Yes 340** *2 X 170 = 340 Yes 300 6 X 115 = 690 Yes 360 32 No

Mi 230** 48 No

*American Table of Distances applies if all or part of stores are Class A ex- ~,losives in approved bullet-resistant magazine.

Compute distance to center of mass by equation 1.

Gondusion: Propagation between ANFO and magazine is possible. Hence the maximum

amount to be considered for public protection is M2 + M3 + M~ = 182,500 pounds.

\ Note that an adequate barricade between the magazine and ANFO masses

will reduce the maximum amount to be considered for public protection to M~ or 100,000 pounds.

138 492-12 SEPARATION AN & ANFO FROM. ANFO OR EXPLOSIVEs

Example 5

MI Mz M,

D2a Dts

ANFO Mix Plant and Warehouse (Figure 2)

200,000 lbs. Fertilizer AN Prills (maximum) 60,000 lbs. ANFO storage (maximum) 80,000 lbs. ANFO (maximum)

30 ft. 30 fL 30 ft.

No other stores on site; 5-foot-thick earth barricade at B.

Potential Donor

M2 (60,000 lbs.) M2 Mi (80,000 lbs.) Ms Combined Ms '+ Ma

(140,000 lbs.)

Distance Table Distance, Projpa. Potential On Site Minimum gation Receptor (ft.) Required (ft.) Possible?

M t 30 25 No Ma 30 6 X 90 -- 540 Yes M ! ' 30 28 No M~ 30 6 )< 101 = 606 Yes

Ml 30* , 37 Yes

Conclusion: In this example the combined masses M~ + Ms may shoot the prills although

the separate masses will not. Hence the maximum amount of blasting agent to be considered for public protection at this site is the total of t~ M I + M 2 + M a = 240,000 pounds.

*Compute distance to center of mass by equation l : 60,000 X 30 + 80,000 X 30

= 30 feet 60,000 + 80,000

GUIDE TO USE OF TABLE 139

492--13

" Fe ~ r t~/T eR !r!!J!}!!!l :~ llill N

(.1 tA ' ' ° .!U ....

: . . . D ~ s _

• " Figure 2". "

~b

140 CE-6 AMENDMENTS TO NFPA NO. 495

Part li Proposed Amendments of Code for

the Manufacture, Transportation, Storage and Use of Explosives and Blasting Agents

"' , N F P A N o . 4 9 5 - - 1 9 6 5

1 . . l n ' 121 add ti~e /ollowing definition: ~'.. WAXXR GZLS, OR SLURRY EXPLOSIVES. These' comprise a wide

variety of materials used for blasting. They all contain substantial proportions of water and high proportions of ammonium nitrate, some of which is in solution 'in the water. Two broad classes of water gels are (a) those which .are sensitized by a material classed as an explosive, such as TNT or smokeless powder, and (:b) those which contain no ingredient classified as an explosive; these are sensitized with metals such as aluminum or with other fuels. Water gels may be premixed at an explosives plant or mixed at the site immediately before~delivery into the bore hole.

2. In 222, next to. last line, change "explosive-actuated" to "propellant-actuated." 3. Renumber 433, 434, and 435 as 434, 435, and 436, and add new 433, 433a, and 433b as ]ollows :

433. Every motor vehicle transporting any quantity of Class A or Class B explosives shall, at all times, be attended by a driver or other attendant of the motor carrier. This attendant shall have been made aware of the class of the explosive material in the vehicle and of i~ts inherent dangers, and shall have been instructed in the measures and procedures to be followed in order to protect the public from those dangers. He shall have been made familiar with the vehicle he is assigned to attend, and shall be trained, supplied with the necessary means, and autho- rized to move the vehicle when required.

a. For the purpose of this section, a motor vehicle shall be deemed "attended" only when the driver or other attendant is physically on or in the vehicle, or has the vehicle within his field of vision and can reach it quickly and without any kind of in- terference; "attended" also means that the driver or attendant is awake, alert and not engaged in other duties or activities which may divert his attention from the vehicle, except for necessary communication with public officers, or representatives of the carrier, shipper or consignee, or except for necessary absence from the vehicle to obtain food or to provide for his physical comfort.

141 COMMITTEE ON CHEMIC.h.LS AND EXPLOSIVES CE-7

b. However, an explosive-laden vehicle may be left unat- tended if parked within a securely fenced or walled area with all gates or entrances locked where parking of such vehicle is otherwise permissible, or at a magazine site established solely for the purpose of storing explosives.

4. In 721 .delete "including mobile equipment,"

5. In 721a, 721b, 722c, 723, 731a, 732b, and 735 change "oxi- dizer" to "ammonium nitrate."

6. Amend 721b to read: b. Minimum intra-plant-separation distances between mixing

units and the ,ammonium nitrate storage ~/reas and blasting agent- storage areas shall be in conformity with the Table of Recommended Separation Distances o f Ammonium Nitrate and Blasting Agents h'om Explosives or Blasting Agents.*

* See Appenc~ A.

7. In 724 change "ingredients, composition or packaging" to ,,]ormulation."

In 724c:.. c/~ange "should",.. to ."shall"

In 725 change "should" to "shall" in both places.

10. In 731a amend the second sentence to read: The mass of blasting agents and one-half the mass of am-

monium nitrate shall .be included when computing the total quantity of explosives f o r determining distance requirements.

11. Amend the first sentence o/731c to read: c. Semi.-trailer or full-trailer vans used for highwa3, or on-

site transportation of the blasting agents are satisfactory for temporarily storing these materials, provided they are located in accordance with the American Table of Distances* with respect to inhabited buildings, passenger railways, and public highways and according .to the Table of Recommended Separa- tion Distances of Ammonium. Nitrate and Blast!ng Agents from Explosives or Blasting Agents* with respect to one another.

* See Apl~ndix A.

142 C E - 8 AMENDMENTS TO NFPA. NO. 495,.

12. Amend 732a to read: a. Warehouses used for the storage of blasting agents Shall

,be located in accordance with the provisions of the American Table of Distances* with respect to inhabited buildings, Pas- senger railways and public highways, and according to the Table of Recommended Separation Distances of Ammoniual Nitrate and Blasting Agents from Explosives or Blasting Agents, with respect to one another.

* See Appendix A.

13. Amend 732b to read: b. If both blasting agents and ammonium nitrate are handled

or stored within the distance limitations prescribed through See. tion 72=1, one-half the mass of the ammonium.nitrate shall be added to the mass of the blasting .agent when computing the total quantity of explosi~,es for determining the proper distance for compliance with the American Table of Distances.*

* See Appendix A.

14. In 734, line 5, change "chlorates, nitrites or similar ma. terials" to "chlorates or nitrites."

15. Renumber present Chapter 8 as ChapterO and make ap. propriate changes in re]erences to this chapter in 311 and 418.

. . J

16. Add new Chapter 8: :.

C H A P T E R 8. W A T E R GELS, OR SLURRY E X P L O S I V E S

81. GENERAL PROVISIONS ": ,

811. Unless otherwise set forth, in this Chapter, water gels shall be transported, stored,, and used in 'the :same manner as explosives or blasting agents in accordanc~ with the classification of the product. •

82. PREMIXED-'WATER GELS " "" 82 I. Premixed water gels cont~tinii~g a substanc.e in itself

classified as an explosive shall b e classified as an explosive and manufactured, transported, stored, and used as specified for explosives in this Code.

143 COMMITTEE ON CHEMICALS AND EXPLOSIVES C E - 9

822. Premixed water gels containin no substance in itself classified as an explosive and which are 1p-sensitive as defined in Section 121 under Blasting Agent sl. 1 be classified as an explosive ana manulacturecl, .transportec stored 'and' used as specified for explosives in this Code.

823. Premixed water gels containing no substance in itself classifiedas an explosive and which are not cap-sensitive as de- lined in Section 121 under Blasting Agent shall be classified as blasting agents and manufactured, transported, stored and used as specified for blasting agents in this Code.

83. O~-Sx~-Mx~D WAT.Va~ GELS ~ ' ' 831. Ingredients for on-site-mixed w~ter gels shall be stored

as set forth in this section. a. Ingredients in themselves classified as Class A or Class B

explosives shall be stored in conformity with Chapter 3. b. Ingredients, other than ammonium nitrate, not in them-

selves classified as explosives, Shall be:stor&l in warehouse s which' shall be noncombustible or fire-resistive.

c. Prilled, grained, or granulated ammonium nitrate shall be stored in accordance with NFPA 490, Code for the Storage of Ammonium Nitrate. If ammonium nitrate is stored in the vicinity of explosives or blasting agents, the separation distances specified in Appendix A12 of this Code shall be observed.

d. Liquid ammonium nitrate soltttions shall be stored in tank cars, tank trucks, or permanent tanks in a location approved by the authority having jurisdiction. Spills or leaks which may contaminate combustible materials shall be cleaned up immediately.

832. If electric power is used, it may be furnished by cable from an outside source or by a self-contained motor generator. In the case of a self-contained power source, it shall be located at the end of the storage container opposite that at which .the blasting agent is discharged. It shall have adequate capacity for the loads to be expected and be equipped with suitable overload protection devices.

833. Electric wiring carrying voltages greater than 12 volts shall be in armored cable or in conduit and~ if dry ingredients are employed, the wiring shall conform to the requirements of Class II, Division 2 of the National Electrical Code, NFPA No. 70.* The materials protecting the electric wiring must be of such composition that they will not be chemically attacked by the ingredients being processed.

144 CE-10 AMENDMENTS TO .NFPA NO. 495

834. 'Mixing equipmen,t for on-site-mixed water gels Shall comply with the requirements of this section.

~t. All electric motors, electrically operated proportioning devices, etc., shall be electrically bonded. -

b. All electric motors, electrically operated proportioning devices, etc., used for dry ingredien,ts shall conform to the require. merits of Class II, Division 2 of the National Electrical Code, NFPA No. 70.*

c. The entire loading and mixing equipment shall be cleaned periodically to insure against accumulations of ingredients.

* See ~qpendix A.

17. Add new 912 as ]oUows: 912. The provisions of this chapter do not apply to in-process

storage and intra-plant ,transportation during manufacture of small arms ammunition, small arms .primers, and smokeless propellants.

"L "'

145 COMMITTEE ON CHEMICALS AND EXPLOSIVES CE-11

f

18. Add new Appendix A12 as JoUows: A12. Table of Recommended Separation Distances of Am-

monium Nitrate and Blasting Agents from Explosives or Blasting Agents* ;x

Donor Weight ( ~

Minimum Separation Minimum Thickness Distance of Receptor • of Artificial

When Barricaded" Barricades 5. (feet) (incheS)

poUNDS oVER

POUNDS A.MJ~ONI'UM " BLASTI~'G NOT O V E R NITRATE ~ A G E ~ '4

100 300 600

1,000

100 300 600

1,000 1,600

A ~

3 4 5

.6 7

11 14 18, 22 25-

12 13 12 12 12

1,600 2,000 3,000 4,000 6,000

2,000 3,000 4,ooo 6,000 8,o00

8 9

10 '~. 11 12

29 32 36' 40 43

12 15 15 IS 2O

8,000 10,000 12,000 16,000 20,000

lO,OOo 12,000 16,000 20,000 25,000

13 14 15 16 t8

47. SO 54 58 65

• 20 20 25 25 25

25,000 30,000 35,000 40,000 45,000

30,000 35,000 40,000 45,000 50,000

19 . 20 21 2,2 23

68 72 76 79 83

30 30

' 30 35

"35

5O,OO0 55,000 60,000 70,000 80,000

55,000 60,000 70,000 80,000 90,000

24 25 26 28 30

86 O0 94

101 108

3$ 35 4O 4O 4O

90,000 100,000 100,000 120,000 120,000 140,000 140,000 160,000 160,000 180,000

32 34 37 40 44

115 122 133 144, 158

40 50 50, 50 SO

180,000 200,000 20O,000 220,0O0 220,000 • 250,000 250,000 275,000 275,000 300,000

48 52 56 60 64

173 187. 202 216 230

50 60

6O 60

* This Table appears in 'Recommended Separation Distances of Ammonium Nitrate and Blasting Agents from Explosives or Blasting Agents, adopted as an NFPA Tentative Standard (No. 492-T) in 1967. For a discussion of the derivation of the Table and examples of how it is applied to actual storage

146 CE-12 A M E N D M E N T S T O N F P A NO. 495

Notes to Table of R e c o m m e n d e d Separation Distances of A m m o n i u m Nitrate and Blast ing Agents from Explos ives or

Blasting A g e n t s

NoTs 1 - Recommended separation distances' 'to prevent ex. plosion of ammonium nitrate .and ammonium nitrate-based blasting agents by propagation from nearby stores of high ex~ plosi~,es or blasting agents referred to in the Table as the "do- nor" Ammonium nitrate, by itself, is not considered to be a

donor when applying this T a b l e . If stores of. ammonium nitrate are located within the sympathetic detonation oistance oI ex. plosives or blasting agents, one-half the mess of the ammonit~ nitrate should be included in the mass of the donor. These dis. tances allow for the possibility of high velocity metal fragments from mixers, hoppers, truck bodies, sheet metal structures, metal containers, and th-e"like, which may enclose the "donor." These distances apply to the separation of stores only. The American Table of Distances shall be used in determining separation dis. tances from inhabited buildings, passenger .railways and public highways.

NOTZ 2 - - W h e n the ammonium nitrate and/or blasting agent is not barricaded, the distances shown in the Table shall be multiplied by six. Where storage is in bullet-resistafft magazines* recommended for explosives, or where the storage is protected by a bullet-resistant wall, distances and barricade thick. nesses in excess of those prescribed in the American Table of Distances (See A l l ) are not required.

NOTE 3 - The distances in the Table apply to ammonium nitrate that passes the insensitivity test prescribed in the definition of ammonium nitrate fertilizer promulgated by the National Plant Food Institute ; t and ammonium nitrate failing to pass said test shall be stored at separation distances determined by competent persons and approved by the authority having jurisdiction. :. .,

NOTZ: 4 - - T h e s e distances ,apply to nitro-carbo-nitrates and blasting agents which pass the insensitivity test prescribed in the ICC regulations. ' --

NOTE 5 - - Earth, or. sand dikes or enclosures filled with the prescribed minimum thickness of earth or sand are acceptable artificial barricades. Natural barricades, such as hills Or timber

* For construction of bullet-resistant magazines, see Chapter 3. t Definition and Test Procedures for Ammonium Nitrate Fertilizer, National

Plant Food Institute, November 1964. .-_

147 COMMITTEE ON CHEMICALS "AND EXPLOSIVES CE-13

of sufficient densi,ty that the surrounding exposures which require protection cannot be seen from t.he "donor" when the trees re bare of leaves, are also acceptable.

Nar~ 6 - - W h e n the ammonium nitrate must be counted in de- _ . . - ° . •

termining the distances t o be maintained from inhabited build-

~n~ S, passenger railways and publichighways, it may be counted

(one-half its actual weight because its blast, effect is lower.

19. A m e n d A 4 6 to r e a d : - ~:

A46. "Safety Recommendations for Sensitized Ammonium Nitrate Blasting Agents," Bur'eau of Mifies, U. S. Department of Interior, Information Circular 8179, 1963.

i •

", : • -

148 CE-14 A M E N D M E N T S TO N F P A NO. 40

Part I I I

*' Proposed Amendments of Standard for the StOrage and Handling of

Cellulose Nitrate Mot ion Picture Film

NFPA N 0 . 4 0 - - 1962 ~

1. Amend paragraph I of Foreioord to read: 1. Motion picture film for many years was manufactured

with a supporting film base of cellulose nitrate ,(commonly called nitrocellulose). Since about 1951, no cellulose nitrate film base of any kind has been manufactured in the United States.

2. Amend paragraph 5 of Foreword to read: 5. In recent years motion picture film has been produced

having a "safety" base of cellulose acetate or other slow-burning esters or polyesters. The fire hazard characteristics of all these materials are roughly similar to those of ordinary paper of similar thickness and form. Unlike cellulose nitrate, they do not produce oxides of nitrogen when burning. This standard does not apply to the storage and handling of "safety-base" film.

3. Renumber paragraphs 6 and 7 of Foreword to be 7 and 8, and insert new paragraph 6 as follows:

6. Safety film is damaged by heat at a lower temperature than is required to destroy paper records. For this reason, "safety" film that has permanent value requires special protection to prevent damage by heat from an exposing fire. See NFPA No. 232, Protection of Records, for protection of "safety" film.

149 C O M M I T T E E ON C H E M I C A L S AND E X P L O S I V E S CE-15

f

. , : Part IV

Proposed Reconfirmation of Standard for the Storage, Handling and Use of

Pyroxylin Plastics in Factories Making Articles Therefrom

"' NFPA No. 4 2 - 1962

The" committee recommends Reconfirmation of the Standard for the Storage, Handling and Use of Pyroxylin Plastics in Fac- tories Making Articles Therefrom (NFPA No. 42 - - 1962) in compliance with Paragraph 91 of the NFPA Regulations Gov. eming Technical Committees. No .changes in technical content are proposed. If favorable action is taken, a few editorial-changes will be made in the text to up.date references.'

Part V b , •

Proposed Reconfirmation of Standard for the Storage, Handling and Use of

Pyroxylin Plastic in Warehouses, Wholesale and Retail Stores.

NFPA No. 4 3 " ~ 1962

The committee recommends Reconfirmation of the Standard for the Storage, Handling and Use of Pyroxylin Plastic in Warehouses, Wholesale and Retail Stores (NFPA No. 43 - - 1962) in compliance with Paragraph 91 of the NF'PA Regula- tions Governing Technical Committees. " No changes in technical content are proposed. If favorable action is taken, a few editorial changes .will be made in the text to up-date references.

150 CE-16 AMENDMENTS TO NFPA NO. 49 ':

Part V!

Proposed Amendments of Hazardous Chemica|s Data

NFPA No. 4 9 - - - 1 9 6 6 .."

I. Add the foUowing paragraph to Explanatory after the discussion of Full Protective Clothing: :

Special Protective Cloth ing . As used in this standard, special protective clothing refers to clothing specially designed to protect against a specific hazard. Special protective clothing is recommended for those chenficals with a health hazard rating of 4.

~. Add the following sentence to the Health /t defiTiition in Ex- planatory: ~

Only special protective clothing des!gned to protect "against the specific hazard should be worn.

3. Change "full protective clothing" to "special protective clothing" in the protective clothing recommendations for chemicals with health hazard ratings of ~.

~. Add "in themselves" to the first sentence of the "Reactivity I/' definition in Explanatory. The amended first sentence is to read:

Materials which in thelnselves are readily capable of detonation or of explosive decomposition or explosi~,e reaction at normal temperatures.and pressures.

5. Add "in themselves" to the first:sentence of the "Reactivity 3" definition in Explanato~:y.. The amended sentence is to read:

Materials which in themselves'are c'apable of detonation or of explosive decomposition or of explosive reaction but which require a strong initiating source or which must be heated undcr confinement before initiation.

6. Add the following paragraph to the present statement on "Elec- trical Equipment" in Explanatory"

Specific reference to the National Electrical Code requirements for special electrical equipment is made for those liquids Imving flash points below 140 ° F. I t should be remembered that if a liquid with a flash point at or above 140 ° F. is heated above its flash point, there may be isolated instances of locatiolis containing flammable atmospheres. Electrical installations in such locations should be in accordance with Article 501 of the National

151 C O M M I T T E E ON C H E M I C A L S AND E X P L O S I V E S CE-:17

l~lectrical Code, and electrical equipment should be suitable for use in atmospheres containing flammable mixtures of the vapor.

7 Delete from "Remarks" of liquids with flash points at or above i"~0 ° F. references to special electrical equipment and electrical installations for flammable atmospheres. ,

8. Make the following editorial changes: (a) Change "poison" and "poisonous" to "toxic" wherever

they appear. (b) Move ICC classification of tetraethyl lead and tetramethyl

lead from Life,Hazard to Usual:Shipping Containers: (c) Delete from Life Hazi~rd bf Chlorine:."Used as such in

World War' I." (d) Change "Ether" to "Ethyl Ether" and "Dibutyl Ether"

to "Butyl Ether."

9. Add the loll'owing chemical data:

ALDRIN (Insecticide) CI~HaCle ~

DESCRIPTION: Brown to White 'crystalline solid. ' Solutions Dry

FIRE AND EXPLOSION HAZARDS: The dry powder will not burn but if heated to decomposition it emits highly toxic fumes of hydrogen chloride and chlorinated breakdown product§. Com- mercial solutions may contain flammable or combustible liquids; flash points, approximately 150 ° F. or higher.

LIFE HAZARD: Toxic by skin contact, inhalation or swalldwing. Solutions containing 10°-/o or over are rapidly absorbed by the skin. Spray mists are extremely hazardous. Fornmlations containing less than 10% may be fatal by skin contact, inhalation or swallowing. Wear full protective clothing. Threshold limit value 0.25 milligrams per cubic meter.

FIRE FIGHTING PHASES: For liquid formulations use water spray, carbon dioxide, dry chemical or foam. Wear complete protective clothing.

USUAL SHIPPING CONTAINERS: 1- and 5-gallon cans; 45-gallon drums. Solutions containing more than 60% aldrin and dry formulations containing more than 65% aldrin are classed as Class B poisons (ICC).

152 CE-18 A M E N D M E N T S TO N F P A NO. 4 9

STORAGE: Protect against physical damage. Outside or detached storage is preferable. Inside storage of liquid formulatio~ should be in a standard flammable liquids storage room or cabinet.

REMARKS: See Chemical Handbook of Economic Poisons, 19~ Revision (Bulletin 476), U.S. Department of Health, Educe'. tion and Welfare, Public Health Service.

x

ALUMINUM CHLORIDE (Anhydrous) AICl3

DESCRIPTION: Orange to yellow through gray to white powder. Melting point, 381 ° F . Has odor of hydr~)- gen chloride, formed by reaction with moisture'in the air.

FIRE AND EXPLOSION HAZARDS: Not explosive or combustible but may react slowly in a fire. Violent reaction will result if streams of water hit large quantities, because of formation of hydrogen chloride.

LIFE HAZARD: Will cause burns on contact with skin and eyes. Severe respiratory irritant. Wear full protectiye clothing.

FIRE FIGHTING PHASES: Attack fires in adjacent materials with dry chemical or foam. Do not use hose streams in vicinity of aluminum chloride. Wear full protective clothing.

USUAL SHIPPING CONTAINERS: Glass bottles, _metal pails and drums containing up to 550 pounds; large bulk containers of rubberized fabric.

STORAGE: Should be in a cool, dry area protected from rain and direct sunshine. Storage in sprinklered buildings is not recommended.

REMARKS: Chemical Safety Data Sheet SD-62 (Manufacturing Chemists' Association, Inc.)

BDEEN:2p TYlLo: HcLo::~s?,Ef: , ~ / : O ; lngent l iquid. ' ~ i

FIRE AND EXPLOSION HAZAaDS: Combustible liquid; will react vigorously with oxidizing materials. Flash point. 162 ° F. Liquid density, 1.2.

' 1 5 3 COMMITTEE ON CHEMICALS AND EXPLOSIVES CE-19

t

LIFI~ HAZARD: Vapors highly irritating to eyes and nose. Liquid is corrosive to skin. Dangerous when heated, generates toxic fumes (phosgene).

FIRE FIGHTING PHASES: Will react energetically with water or steam with production of heat , toxic and corrosive fumes. Wear full protective clothing. Use water spray sparingly, foam, carbon dioxide or dry chemical.

UsuAL SHIPPING CONTAINERS: Bottles and carboys, tank cars.

STOaAGE: Protect against physical damage. Do not store with oxidizing ma.terials. Outside or detached storage is preferable.

REMARKS: See Flammable and Combustible Liquids Code (NFPA No. 30), National Electrical Code (NFPA No. 70), Guide to Precautionary Labeling of Hazardous Chemicals (Manual L-I), Manufacturing Chemists' Association, Inc.

BENZYL CHLORIDE cGHscH2CI / ~ x DESCRIPTION: Colorless to slightly yellow liquid with

pungent, aromatic, irritating odor.

FIRE AND EXPLOSION HAZARDS: Combustible liquid. Flash point, 153 ° F. Lower flalnmable limit, 1.1%. Ignition temperature, 1,161 ° F. Liquid is heavier than water (specific gravity, 1.10).

Unstabilized benzyl chloride readily undergoes a condensa- tion reaction with liberation of heat and hydrogen chloride in the presence of copper, aluminum, iron, zinc, magnesium, tin and various other metals which act as catalysts. If the reaction takes place in a container, there is the possibility of violent rupture of the container.

LIVE HAZ~.RD: Eye, skin and respiratOry irritant. Threshold limit value, 1 part per million. Wear self-contained breathing apparatus.

FIRE FIGHTING PHASES : Use water spray, dry chemical, or carbon dioxide. Flush spills with large quantities of cold water and ventilate the area to remove vapors. Wear self-contained breathing apparatus.

USUAL SHIPPING CONTAINERS: Glass bottles or carboys, nickel drums up to 55 gallons, nickel tank trucks and tank cars. Stabilized benzyl chloride only: steel drums, nickelclad tank trucks and tank cars.


STORAGE: Protect against physical damage. Outside or detached storage is preferable. Inside storage should be in a cool, dry, well-ventilated room of fire-resistive construction. Do not store with flammable or oxidizing materials.

REMARKS: See National Electrical Code ,(NFPA N 0. 70), Fire Hazard Properties of l'lammable Liquids, Gases and Volatile Solids (NFPA No. 325M), and Chemical Safety 'Data Sheet SD-69 (,X,[anufacturing Chemists' Association, Inc.).

BORON TRIFLUORIDE BF3 DESCRIPTION: A colorless gas with a pungent, irritat-

ing odor. Fumes strongly in nmist air to form fluo- boric and boric acids, and the particulates in the fume may reduce visib!lity when a large volume of gas escapes.

FIRE AND EXPLOSION HAZARDS: Nonflammable gas. Recom- mended as an effective extinguishing agent for magnesium fires in heat-treating furnaces.

! .

LIF'E HAZARD: Extremely irritating to eyes and respiratory, tract. Corrosive to skin. Wear full protective clothing. Gas density,

• 2.3. Threshold limit value, 1 part per million.

FIRE FIGHTING PHASES.: Wear full protective clothing. Do not apply water: directly to leaks frdm cylinders because it will increase the rate of.evaporation.. A fog-type spray .may be used to react with imd help eliminate the gas and particulates.

USUAL SHIPPING CONTAINERS :" Pressure cylinders.

STORAGE: Protect cylinders against physical damage. Store out- doors or in a well-ventilated area in a noncombustible structure.

REMARKS: Refer to Standard for the Storage, Handling and Processing of ~Iagnesium (NFPA' No. 48), Section 1246, for use of boron trifluoride as a fire extinguishing agent.

n-BUTYLAMINE C~HgNH~ • X ~ , DESCRIPTION: Colorless, volatile liquid with ammonia-

like •odor.

FIRE AND EXPLOSION HAZARDS: Flammable liquid. Vapor forms explosive mixtures with air. Flammable limits, 1.7% and 9.8%. Flash point, 10 ° F. Ignition temperature, 594 ° F.

155 C O M M I T T E E O N C H E M I C A L S A N D E X P L O S I V E S CE-21

Boiling point, 172 ° F. Liquid is lighter thafi water (specific gravity, 0.74). Vapor is heavier t h a n a i r (vapor-air density at 1000 F., 1.5) and may travel a considerable distance to a source of ignition and flash back. Liquid is miscible with water, alcohol and ether.

I,IFE HAZARD: Moderately toxic. Eye, skin and respiratory irritant. Threshold limit value, 5 parts per mil~'on. Wear goggles and self-contained breathing apparatus. .,

FIRE FIGHTING PHASES: Water may be ineffective: Use "alcohol" foam, dry chemical or carbon dioxide. Wear goggles and self- contained breathing apparatus.

USUAL SHIPPING CONTAINERs: 1-gallon cans; 5- and 55-gallon drums; tank cars.

S~ORAGE: P r o t e c t a g a i n s t playsical damage. Separate from oxidizing materials and sources of heat. Outside or detached storage is preferable. Inside storage should be. in a s tandard flammable liquids storage room or cabinet.

REd,ARKS: Electrical installations in Class I hazardous locations, as defined in Article 500 of the National Electrical Code, should be in accordance with Article 501 of the Code; and electrical equipment should be suitable for use ~ atmospheres c?ntaining butylamine vapors. See Flammable and Combustible Liquids Code (NFPA No. 30), Fire Hazard Properties of Flammable Liquids, Gases and Volatile Solids (NFPA No. 325M), and National Electrical Code (NFPA No. 70)..

CHLOROPICRIN CCI3NO~ " / ~ x

DESCRIPTION: Colorless, oily liquid with a very in- tense and penetrating odor which causes a pro- notmced secretion of tears.

FIRE AND EXPLOSION I~AZARDS: Noncombustible liquid. Boiling point, 233 ° F. Specific gravity, 1.65. Liquid is not soluble in water. It shows some reactivity when heated under confinement and this might become hazardous if the equipment per- mite high pressure build-up.

LIFE HAZARD: Very toxic. Chloropicrin is a pronounced irritant to all body surfaces. In addition to skin irritation, it causes eye watering, vomiting, bronchitis and pulmonary edema. Short exposures may cause fatal lung damage. Entry into contaminated areas should be attempted only with special protective clothing. Threshold limit value, 0.I parts per million.


FIRE FIGHTING PHASES: Wear special protective clothing. Water may be used for fighting a fire in an area where chloropicrin is stored.

USUAL SHIPPING CONTAINERS: Metal drums containing a maximum of 30 gallons. One-pound glass bottles in hermetically sealed metal cans packed inside wood or fiberboard boxes.

STORAGE: Protect against physical damage. Outside or detached storage is preferred. Inside storage should be in a well- ventilated room.

DIETHYLAMINE (C2Hs)~NH " ~

DESCRIPTION: Colorless, alkaline liquid with an ammonia-like odor.'

FIRE AND EXPLOSION HAZARDS: Flammable liquid. Vapor forms explosive mixture with air./Flammable limits, 1.8% and 10.1% Flash point, less than 0 ° F . Ignition temperature, 594 ° F. Liquid is lighter than .water (specific gravity, 0..7) but soluble in water in all proportions. Vapor-air density at 100 ° F., 1.8; therefore, vapors may travel a considerable distance to a source of ignition and flash back.

LIFE HAZARD: A se~cere respiratory irritant and ~ corrosive to the eyes and skin.' Wear self-contained breathing apparatus and eye and skin protection. Threshold limit value, 25 parts per million.

FIRE FIGHTING PHASES: Soluble in water. Use carbon dioxide, dry chemical, or "alcohol" foam. Water may be ineffective (see Explanatory). Wear self-contained breathing apparatus.

USUAL SHIPPING CONTAINERS: Glass bottles, 1-to 5-gallon cans; 55-gallon steel drums; tank cars.

STORAGE : Protect against physical damage. Outside or detached storage is preferable. Inside storage should be in a standard flammable liquids storage room or cabinet.

REMARKS: Electrical installations in Class I hazardous locations, as defined in Article 500 of the National Electrical Code, should be in accordance with Article 501 of the Code; and electrical equipment should be suitable for use in atmospheres containing diethylamine vapom. See Flammable and Com- bustible Liquids Code (NFPA No. 30), National Electrical Code (NFPA No. 70), Static Electricity (NFPA No. 77) and Fire Hazard Properties of Flammable Liquids, Gases and Volatile Solids (NFPA No. 325M).

157 COMMITTEE ON CHEMICALS AND EXPLOSIVES CE--23

j ,4 -DINITROCHLOROBENZENE C,H3(N02)~CI

DESCRIPTION: Colorless or yellow needles, which may be fused solid.

FIRE AND EXPLOSION HAZARDS : Combustible. Flash point, 382 ° F. Flammable limits, 1.9% and 22%. Explosion hazard. Has been known to detonate at about 300 ° F. It can be detonated by shock or heat under confinement that will-permit high pressure buildup.

LIFE HAZARD: Highly toxic by ingestion, inhalation or skin ab- sorption. Skin sensitizer. Wear full protective clothing.

FIRE FIGHTING PHASES: Use extreme caution in approaching a fire as the material may explode when exposed to heat or flame. No attempt should be-made to fight fires except for remote manual activation of installed fire extinguishing equipment, or with unmanned fixed turrets and hose nozzles. The surrounding area should be evacuated. For rescue operations, wear full protective clothing.

USUAL SHIPPING CONTAINERS: Drums and tank cars.

STORAGE: Protect against physical damage. Keep away from heat and sources of ignition or acute fire hazard areas. Storage area should be equipped with an automatic sprinkler system if within a building.

REMARKS: See Fire Hazard Properties of Flammable Liquids, Gases and Volatile Solids (NFPA No. 325M).

ENDRIN C~HsOC16

DESCRIPTION: When pure, endrin is a white crystalline solid. Technical grades are light tan color. -Melting point, below 392 ° F.; above this temperature it decomposes. Not soluble in water, soluble in aromatic hydrocarbons, esters and ketones.

Solutions Dry

FIRE AND EXPLOSION HAZARDS: The dry powder will not burn but will decompose when heated beyond 392 ° F., emitt ing highly toxic fumes of hydrogen chloride and chlorinated decomposition products. Comnmrcial solutions contain flammable liquids whose flash points may be as low as 80 ° F. (oc). Therefore, flammability rating of s01utiolis depends on the rating of the solvent.

158 .CE-24 AMENDMENTS TO NFPA NO. 49

LiFE I-[AZARD: Toxic by skin contact, inhalation or ingestion. Causes dizziness, weakness of legs, nausea and abdominal pains. Solutions of over 2.5% endrin are rapidly absorbed by the skin. Wear full protective clothing. Threshold limit value, 0.1 nlilligram per cubic meter. "

FIRE FIGHTING PHASES: For solutions, use water spray, carbon dioxide, dry chemical or foam. Wear full protective clothing.

USUAL SHIPPING CONTAINERS: Dry powder: 25-gallon fiber drums. Solutions: 1- and 5-gallon cans; 45-gallon drunks. Solutions containing 10.2% or more of endrin and dry fornlula- tions of 25% or more are classed as Class B Poisons (ICC).

STORAGE: Protect against physical damage. Solutions should be in outside or detached storage. Inside storage should be in a standard flammable liquids storage room or cabinet.

REMARKS: See Chenfical Handbook of Economic Poisons, 19fi4 Revision (Bulletin 476), U.S. Department of Health, Educa- tion and Welfare, Public Health Service.

E P I C H L O R O H Y D R I N C3H5OC1

DESCRIPTION: Colorless, mobile liquid; irritating chloroform-like odor.

FIRE AND EXPLOSION HAZARDS: Vapors form explosive mixtures with air. Flash point, 105 ° F. Liquid is slightly heavier than water (density 1.17). Epichlorohydrin and its derivatives which contain the epoxide group may polymerize exothermieaUy in the presence of catalysts such as acids, basses, and certain salts, or react with compounds having a labile hydrogen atom, including water. These reactions can genera~ enough heat and pressure to overflow vessels or. cause explosions.

LIFE HAZARD: It is estimated that ingestion of one gram of this material could be a fatal dose. Vapors should be avoided. They are irritating to the skin and the lungs, and painful to the eyes and nose, a n d may cause other harmful effects as well. Threshold limit value, 5 parts per million. Wear full protective clothing.

FIRE FIGHTING PHASES: Use water, foam, carbon dioxide or dry chemical. When heated to decomposition, epichlorohydrin emits highly toxic' fumes of phosgene. Wear full protective clothing.

USUAL SHIPPING CONTAINEItS: Drums or tank cars. Epichloro- hydrin is a Class B Poison (ICC).

159 COMMITTEE ON CHEMICALS AND EXPLOSIVES C E - 2 5

S~oRAGE: Protect against physical damage. Separate from all acids, bases, and' anhydrous metal halides. Detached storage is preferred. Store in cool, well-ventilated building, free from combustible material. Protect against contamination.

RsMARKS: Electrical equipment in Class I hazardous locations as defined in Article 500 of the National Electrical Code should be in accordance with Article 501 of the Code; and electrical equipment should.be suitable for use in atmospheres containing epichlorohydrin' vapors. See National Electrical Code (NFPA No. 70) and Flammable an d Combustible Liquids Code (NFPA No. 30).

FORMIC ACID HCOOH DESCRIPTION: C o l o r l e s s , fuming liquid, pungent,

penetrating odor. General technical product is a 90% water solution. . .

FIRE AND EXPLOSION HAZARDS: Strong reducing agen~ wi th moderate fire hazard. ]~lash point, 156 ° F. (90% solution, 122 ° F.). Combustible liquid. Ignition temperature, 1,114 ° F. (90% solution, 813 ° F.). Flammable limits, 18% and 57%. Boiling point, 213 ° F. Freezing point, 47 ° F. Liquid is heavier than water (specific gravity, .1.2) and is completely soluble in water.

LIFE HAZARD: Acute irritant (constituent in stings of ants, bees, and nettles), highly toxic (inhalation) ori very short exposure. Dangerously caustic to skin, producing superficial blisters and painful "burns" bn contact. Readily dehydrated by con- centrated sulfuric acid to produce carbon monoxide. A tentative threshold, limit value of 5 parts per million suggested in 1965. Wear full protective clothing.

FIRE FIGHTING PHASES: Use water, "alcohol" foam, dry chemical, carbon dioxide or other inert gas. Water spray may be used effectively to "sweep Out" vapors and clear area in event of non-fire spillage or leak accidents. Wear complete protective clothing.

USUAL SHIPPING CONTAINERS:. Stainless steel drums or protected glass carboys. ICC wa'rn.ing requirement: White label (corrosive liquid).

~TORAGE: Protect against freezing and physical damage. Store in a well-ventilated place, avoid exposure to sources of heat (solar, etc.); separate storage from sulfuric acid. Outside or detached storage is preferred for stock supplies.

150 CE-26 A M E N D M E N T S T O N F P A N O . 49.

REMARKS: Electrical equipment in Class I hazardous locations, a s defined in Article 500 of the National Electrical Code,

should be installed in accordance with Article 501 of the Code; and electrical equipment should be suitable for use in atmospheres containing formic acid vapors. See National Elec- trical Code (NFPA No. 70), and Flammable and Combustible Liquids Code (NFPA No. 30).

ISOPROPYL ETHER (CH3j~CI-[OCH(CH3)~. ' , 4 ~

DESCRIPTION: Colorless, volatile liquid with ethereal odor.

-FIRE AND EXPLOSION HAZARDS: t lammabh liquid. Flammable limits, 1.4% and 7.9% and flammable mixtures with "air are formed readily at 'room temperatures.. Flash point, minus 18 ° F. (ce). Boiling point, 155 ° F. Ignition temperature, 830 ° F. Vapor-air density at 100 ° F. is 1.47. Vapor is heavier than air

, and may travel a considerable distance to a source of ignitioa and flash back. Unstable peroxides may form on long standing .in contact with air and these may explodespontaneously or when heated.

LIFE HAZARD : The main action is anesthetic and high concentrations of the vapor in air can cause unconsciousness. Threshold limit value, 500 parts per million.

FIRE FIGHTING PHASES: Isopropyl ether is lighter than water and only slightly soluble in water; water may spread a spill fire. Use "alcohol" foam, carbon dioxide or dry chemical. '~,

USUAL SHIPPING CONTAINERS: Glass bottles, steel drums and cans.

STORAGE: Protect against physical damage. Detached outside storage is preferred. Inside storage should be in a standard flammable liquids storage room or cabinet. Isolate from other combustible materials. Avoid direct sunlight. Protect against !, static electricity and lightning. For large quantity storage rooms, protect with automatic spr.inkler systems and total flooding carbon dioxide systems. The reactivity hazard may be increased to 3 on long standing, due to peroxide formation.

REMARKS: Electrical equipment in Class I hazardous locations, as defined by Article 500 of the National Electrical Code, should be installed in accordance with Article 501 of the Code; and electrical equipment should be suitable for use in atmospheres of isopropyl ether. See National Electrical Code (NFPA No. 70) and Flammable and Combustible Liquids Code (NFPA No. 30).


METHYL CHLORIDE CH3CI X / ~

DESCRIPTION : Colorless gas with faintly sweet ethereal odor.

F I R E AND EXPLOSION HAZARDS: Flammable gas. Forms flammable mixtures with air. Flamnmble linfits, 10.7% and 17.4%. Ignition .temperature, 1,170 ° F. •Vapor heavier than air (vapor density, 1.8).

LIFE HAZARD: Inhalation of high concentrations of methyl chloride causes serious central nervous system damage, linger- ing illness and sometimes death. Because methyl chloride has so little odor and only a mild narcotic action, persons may be exposed to considerable concentrations without being aware of the danger. The onset of symptoms of poisoning, such as dizziness, headache, optical difficulties, nausea and vomiting, may be delayed for many hours. Threshold !imit value of methyl chloride, 100 parts per million. Wear self-contained breathing apparatus.

FIRE FIGHTING PHASES: Stop flow of gas. Use water to keep containers cool. Do not extinguish unless necessary to effect an immediate shutoff of flow. Dry chemical and carbon dioxide may be used to extinguish methyl chloride fires. Wear self-contained breathing apparatus.

USUAL SHIPPING CONTAINERS: Shipped as a liquid under pressure in cylinders and tank cars.

STORAGE: Protect against physical damage. Store in cool, well- ventilated area of noncombustible construction, away from sources of ignition.

REMARKS: Electrical installations in Class I hazardous locations, as defined in Article 500 of the National Electrical Code, should be in accordance with Article 501 of the Cods; and electrical equipment should be suitable for Use in atmospheres contaia- ing methyl chloride gas. Sec National Electrical Code (NFPA No. 70) and Chemical Safety Data Sheet SD-40 (Manufactur- ing Chemists' Association, Iac.).

METHYL PARATHION (CH30)2P(S)OCeH4NO~

DESCRIPTION: A white crystalline solid or powder. Commercial methyl parathion is a liquid consisting of 80% methyl Solid parathion-and 20% xylene.

Xylene Solution


FIRE AND EXPLOSION HAZARDS: F lash point of.commercial product, 115 ° F. (oc). Decomposes at temperatures above ambient and may develop sufficient internal pressure to cause the container to rupture violently. It can react with oxidizing materials.

LIFE HAZARD: Very toxic and can be fatal by skin contact, inhalation, or ingestion; rapidly absorbed through skin; repeated exposure may, without symptoms, be increasingly hazardous. There is no threshold limit value listed, but it .closely ap- proaches that of parathion (0.1 milligranl per cubic lneter).

W h e n heated, it emits highly toxic fumes. Wear special pro: tective clothing. ..

FIRE FIGHTING PI~ASES: Dangerous exposure to persons fighting fires. Use water spray. High-pressure water streams may scatter material from broken containers, increasing contamination hazards. Wear special protective clothing.

USUAL SHIPPING CONTAINERS: Drunls.

STORAGE: Protect against physical damage. Do not store at high ambient temperatures (at 120 ° F. some decomposition occurs with resulting pressure increase). Store in areas where any

"spillage from containers will not endanger workers or contaminate other storage. Separate from oxidizing materials and avoid storage near combustibles.

• - . , A

OXYGEN (LIQUID)" DESCRIPTION: A blue liquid (blue solid,when frozen).

FIRE" AND EXPLOSION HAZ~.RDS: Nonflammable itself, but pro- motes combustion ill proportion to the concentration of oxygen present. Can cause spontaneous fires in contact with combustible materials, especially when the oxygen is under high pressure. Liquid oxygen foE'ms explosive mixtures with organic and other readily oxidizable materials.

LIFE HAZARD:The liquid call cause severe "frost-bite" or "burn" to the skin or other bodily tissues. Gaseous oxygen from the liquid is absorbed readily in clothing and ally source of ignition may cause flash burning. Ill gaseous form, no hazard, except that of irritation of IIIUCOUS membranes is likely if 100% oxygen is inhaled continuously for more than a few hours. Smoking in oxygen-enriched atmospheres is extremely hazardous.

163 C O M M I T T E E ON C H E M I C A L S AND E X P L O S I V E S CE-29

FIRE FIGHTING PHASES: Use water to cool tanks exposed to fire in order to prevent pressure rupture of the containers, which would disastrously magnify the fire: Wear special clothing that will not ignite on contact with liquid oxygen and that is designed to preyent liqui d oxygen from coming in contact with the skin.

When the fire results from a leak or flow of liquid oxygen onto wood, paper, waste or another similar material, the first thing to do is stop the flow if possible. For small spills, or after the leak or flow of liquid oxygen has been stopped, use enough water to put the fire out quickly. When the fire involves liquid oxygen and liquid fuels, control it as follows:

(a) When liquid oxygen leaks or flows into large quantities of fuel, shut off the flow of liquid oxygen, and put the remaining fuel fire out with extinguishing agents suitable for use on Class B fires. When fuel leaks or flows into large quantities of liquid oxygen, shut off the flow of fuel.

(b) When fuel and liquid oxygen are mixed or mixing but are not yet burning, isolate the aria from sources of ignition and get out quickly, allowing the oxygen to evaporate. When large pools of water-soluble fuel are present, use water to dilute the fuel and to reduce the intensity of the fire. This method canno,t be used with fuels which do not mix with water. Appropriate extinguishing agents may be used to put out fuel fires after the oxygen has evaporated.

USUAL SHIPPING CONTAINERS: Dewar flasks and tank trucks.

STORAGE: Protect ~gainst physical damage. Isolate from coin- bustible gas installations and combustible materials by adequate distance or by gas-tight fire-resistive barriers. Protect against overheating. Outside storage of liquid oxygen tanks is recommended.

REMARKS: See Standard for Nonflammable Medical Gas Systems (NFPA No. 565) and Standard for the Installation of Bulk Oxygen Systems at Consumer Sites (NFPA No. 566).

l

SULFUR MONOCHLORIDE $2C12

DESCRIPTION: Amber to yellowish-red, ~ 0ily, fuming liquid with a penetrating odor.

FIRE ANW EXPI~OSION HAZARDS: Combustible. Flash point, 245 ° F. Autoignition temperature, 453 ° F.

164 CE-30 A M E N D M E N T S T O N F P A NO. 49

LIFE HAZARD: Causes burns. Vapors irritating. Avoid contact of liquid and vapors with eyes, skin or clothing.

FIRE FIGHTING PHASES i Use water spray, carbon dioxide or dry chemical. Wear lself-contained breathing apparatus and goggles. Decomposes on contact with water to produce heat and toxic and corrosive fumes.

USUAL SHIPPING CONTAINERS: Metal drums, tank cars and tank trucks.

STOOGE: Keep containers well closed and upright, away from heat. Do not allow water to get into container as this material reacts violently with water when in a closed vessel. Provisions should be made for washing down spills with large quantities of water. Vapor-tight electrical equipment is recommended to reduce corrosion.

REMARKS: See Fire Hazard Properties of Flammable Liquids, Gases and Volatile Solids (NFPA No. 325N[) and Chemical Safety D a t a Sheet SD-77 (Manufacturing Chemists' Asso- ciation, Inc.).

T ITANIUM TETRACHLORIDE TiCI~

DESCRIPTION: Colorless to light-yellow liquid, fumes in moist air.

FIRE AND EXPLOSION HAZARDS: Corrosive liquid; will react vigorously with water . Boiling point, 278 ° F. Specificgrayity, 1.7.

LIFE HAZARD: Vapors highly irritating to eyes and nose. Vapors irritating to skin. Liberates heat and hydrochloric acid on contact with moisture. Threshold limit value not established (TLV for HCI, 5 parts per million).

FIRE FIGHTING PHASES: Will react with hot water. Soluble in cool water. Wear full protective clothing. Use water spray if necessary to keep containers cool.

USUAL SHIPPING CONTAINERS :Glass bottles and carboys, wooden • boxes containing sof t l ead tubes inside steel tubes. N[etal

drums and tank cars.

STOOGE: Protect against physical damage. Outside or detached storage is preferable . . . . .

165 C O M M I T T E E ON C H E M I C A L s A N D E X P L O S I V E S CE-31

I0. Add the following synonyms:

I-AMINO BUTANE See n-BUTYLAMINE

BENZENE CARBONYL CHLORIDE See BENZOYL CHLOmVE

CHLOROBENZALDEHYDE See BENZOYL CHLORIDE

CHLORODINITROBENZENE See 2~4-DINITROCHLOROBENZENE

I ' C H L O R O ' 2 , 4 " D I N I T R O B E N Z E N E

See 2~4-DINITROCHLOROBENZENE

I - C H L O R O - 2 , $ - E P O X Y P R O P A N E

See EPICHLOROHYDRIN

CHLOROMETHANE See METHYL CHLORIDE

CHLOROMETHYLOXIRANE See EPICHLOROHYD.RIN

CHLOROPROPYLENE OXIDE See EFICHLOROHYDRIN

a lpha -CHLOROTOLUENE See BENZYL CHLORIDE

CHLOROTOLUOL See BENZYL C~LORIDE

CHLORPICRIN See CHLOROPICRIN 1

DIISOPROPYL ETHER See ISOPROPYL ETHER

DINITROCHLORBENZOL See 2,4-DINITROCHLOROBENZENE

EPI See EPICHLOROHYDRIN

HHDN " ' - See ALDRIN

LOX See OXYOEN (LIQUID)

METHANOIC ACID See FORMIC ACID

NITROCHLOROFORM See CHLOROPICRIN

N I T R O T R I C H L O R O M E T H A N E See .CHLOROPICRIN

OCTALENE See ALDRIN

PICFUME • See CHLOROPICRIN

T R I C H L O R O N I T R O M E T H A N E See CHLOROPICRIN


PART VII PROPOSED AMENDMENTS O1:

CODE FOR THE

sTORAGE OF AMMONIUM-NITRATE "NFPA No. 490---1965

1. In the last sentence of the second paragraph of the Fore. word add " w i t h abou t ha l f t he b las t ef fect of explosives ." The amended sentence will read: " A m m o n i u m n i t r a t e is capable of u n d e r g o i n g de tona t ion w i th abou t ha l f t h e blast effect of explosives , i f hea t ed u n d e r conf inement t h a t per- mi t s h igh p r e s s u r e build-up, or is s u b j e c t e d to s t r o n g shocks,

- such as those f r o m an explos ive ."

2. Add the following sentence to the end of the.second paragraph of the Foreword: " T h e sens i t iv i ty of a m m o n i u m n i t r a t e to de tona t ion increases a t e leva ted t e m p e r a t u r e s . "

3. Insert the following paragraph between the ihird and fourth paragraphs of the Foreword:

Recent test data on ammonium nitrate are included in the U.S. Bureau of Mines Report of Investigations 6746, Sympathetic Detona- tion of Ammonium Nitrate and Ammonium Nitrate Fuel Oil; Report of Investigations 6903, Further Studies of Sympathetic Detonation; and Report of Investigations 6773, Explosion Hazards of Ammonium Nitrate Under Fire Exposure. On the basis of these repol~ts a Table of Distances of Ammonium Nitrate and Blasting Agents from Blast- ing Agents or Explosives has been developed. The table is included in Appendix A of Code for the Manufacture, Stoi'age, Transportation and Use of Explosives and Blasting Agents, NFPA No. 495.

$. In the last paragraph of the Foreword insert " a g a i n s t fire and explos ion ." The amended paragraph will read:

• d

With proper precautions" against fire and explosion, ammonium nitrate can be stored safely at the plant, in distributors' warehouses, or on the farm.

5. Add the following new Section ~,Z/,:

424. The a m m o n i u m n i t r a t e s t o r age bins o r piles shall be c lear ly identified by s igns r e ad ing " A M M O N I U M NI- T R A T E " wi th le t t e r s a t leas t 2 inches high.


6. Amend the first sentence of Section 511 to read:

511. Ammonium nitrate shall be in a separate building or shall be separated by approved type fire walls of not less than one hour fire-resistance rating from storage of organic chemicals, acids or other corrosive liquids, materials that may require blasting during processing or handling, compressed flammable g a s e s . . . (no change in rest of sentence).

7. Amend Section 522 to read:

522. Explosives and blasting agents shall not be stored in the same building or on the premises with ammonium nitrate unless proper distances are maintained in accordance with t he Table o f Distances of Ammonium Nitrate and Blasting Agents from ,Blasting Agents or. Explosives.*

7 ,

8. Add new Article 67 and Section 671 "as follows':

67. Control of Access 671. Provisions shall be made to prevent Unauthorized

personnel f rom entering the ammonium nitrat e storage area.

- ' . . . . . . . . . : r ~ - ,

*Printed in Appendix A of Code for the Manufacture, Storage, Transportation" and "Use of Explosives and Blasting Agents, NFPA No. 495. -.- -. ,.

• . " i ' .

168 C O N T E N T S 496-3

Part VIII

Proposed Standard for Purged Enclosures for Electrical

-Equipment in Hazardous Locations

NFPA NO. 496--1967

Contents

C h a p t e r 1. General Provisions

11. Object and. Scope 4 9 6 - 5

12.. Equipment and Locations Covered ........ : ............... '496- 5

13. Degree of Hazard ....... . ......................................... ..... 496- 5

14. Definitions . . . . . 496- 5

Chap te r 2 .

2i. 22.

23.

24.

25.

!ns t rument and O t h e r Small EnclOsures

Scop~ ......... i.'.~.~:. ................ ...:...~.' ............. ' .......... ".'.: ....... 496- 7

General Requirements .............................................. 496- 7

Specific Requirements for Type Z Purging " 3~96- 9

Specific Requirements for Type Y Purging ' 496-11

Specific Requirements for Type X Purging " 496-12

Chapter 3 . Control R o o m s

31. Scope .................................................................. : ....... 496-16

32. Control Room ...... . ................... i ............. ~ ......... '~....:.. 496-16

33. Considerations Relating to Positive Pressure Ventilation .................................................................. 496-16

34. Requirements for Positive Pressure Air Systems ...... 496-17

Chapter 4. Electrical Power Equipment Enclosures

41. Scope ........................................................ : ............ : ...... 496-19

42. Requirements for Purged Equipment .................... 496-19

43. Requirements for Ventilated Equipment .............. 496-21

GENERAL PROVISIONS 169

496-5

CHAPTER 1. GENERAL PROVISIONS

11. Object and Scope

111. The Object of this Standard is tO provide information for

~ e design of purged enclosures for the purpose" of eliminating or ducing within the enclosure a Class I hazardous location classifi-

cation, as defined in Article 500 of the National Electrical Code, NFPA No. 70. By this" means, equipment Which is not otherwise ~cceptable for hazardous locations may be utilized inaccordance ~¢ith the National Electrical Code.

12. Equipment and Locations Covered

121. This'Standard applies to instruments, control rooms, motors, motor controllers, switchgear, and similar equipment.

122. This Standard applies to locations where flammable gases or vapors may be present_ in a i r in Concentrations sufficient for the locations to be classified as hazardous.

13. Degree of Hazard

131. There are two degrees of hazard: 1, normally hazardous (Division 1), and 2, hazardous only under abnormal conditions (Division 2).

132. The degree of hazard may be safe!y reduced (Division~ 1 to Division 2), or may be eliminated (Division 1: or Division 2 to nonhazardous) by purging, provided the installations: are properly designed, installed, and maintained.

133. Electrical equipment should be located in the area having as low a degree of hazard classification as practicable.

14. Definitions

141. In this Standard the following terms are used as defined below:

Division 1 LOCATIONS are those (1) in which hazardous concentrations of flammable gases or vapors exist continuously, intermit- tently, or periodically under normal operating conditions; (2) in which hazardous concentrations of such gases or vapors may exist frequently because of repair or maintenance operations or because of leakage; or (3) in which breakdown or faulty operation of equipment or processes which might release hazardous concentra-

170 496-6 P U R G E D E N C L O S U R E S

tions of flammable gases or vapors might also cause simultaneous failure of electrical equipment.

Division 2 LOCATXONS are those (1) in which volatile flammable liquids or flammable gases are handled, processed or used, but in which the hazardous liquids, vapors or gases will normally be confined within closed containers or closed systems from which they can escape only in case of accidental rupture or breakdown of such containers or systems, or in case of abnormal operation of equip. ment; (2) in which hazardous concentrations of gases or vapors are normally prevented by positive mechanical ventilation, but which might become hazardous through failure or abnormal operation of the ventilating equipment; or (3) which are adjacent to Division 1 locations, and to. which h~ardous concentrations of gases or vapors might occasionally be communicated Unless such communication is prevented by adequate positive=pressure ventilation from a source of clean air, and effective safeguards against ventilation failure are provided.

PURGING is the process of. supplying an enclosure with clean air or an inert gas at sufficiefit flow and positive pressure ;to reduce to an acceptably safe level the concentration of any flammable gases or vapors initially present, and to maintain this safe' level by positive pressure with or without continuous flow.

TYPE X PU/~GINO reduces the classification within a~ enclosure from Division 1 to nonhazardous.

~TYPE Y PURGING reduces the classifi~cation With!n an enclosure from Division 1 to Division 2 . , "

TYPE Z PURGING reduces the classification within an enclosure from Division 2 to nonhazardous.

I

INSTRUMENTS 171

496-7

C H A P T E R 2. I N S T R U M E N T AND OTHER SMALL ENCLOSURES

21. Scope

211. Chapter 2 applies to enclosures with a gross internal volume not exceeding 10 cubic feet. For larger enclosures see 'Chapters 3 and 4.

22. G e n e r a l Requirements "

221. The enclosure shall be o f such noncombustible material and construction that is not likely to be broken under conditions to which it is likely to be subjected, :

222. Any window in a purged enclosure shall,be tempered glass at least. ~ inch thick, shatterproof glass or other shatterproof material. .

223. I f hazardous vapors or gases have collected within the enclosure, either because the enclosure has been opened or the purge has failed, then the enclosure must be purged.

2231. Once the enclosure has been purged of hazardous concentrations, it is not obligatory to maintain any given flow rate. I t is 0nly necessary that positive-pressur e be maintained within the enclosure.

224. Since the intent is to purge an enclosure to r e d u c e t h e concentration of hazardous vapors or gases to an acceptably safe level, compartments within the main enclosure or adjacent enclosures connected to the main enclosure must be considered separately.

2241. They may be adequately vented to the main enclosure.

2241a. An internal enclosure or an adjacent enclosure that is being considered as part of and purged with the main enclosure must have nonrestricted "top and bottom vents, common to the purged main enclosure, having a minimum size for each vent of 1 square inch per 400 cubic iflches of the volume of the internal or adjacent enclosure.

NOTE: In order for any internal or adjacent enclosure to be automatically purged as the main enclosure is purged, adequate vents must

172 496-8 PURGED E N C L O S U R E S

be provided to permit air circulation between it and the' main enclosure. The area required to provide adequate venting will obviously depend upon the internal or adjacent enclosure. It is considered that meeting this requirement will prevent the formation of unpurged pockets of gas within the enclosure. It is not intended to imply that internal or adjacent enclosures not meeting these venting requirements are prohibited but that such enclosures must be provided with their own purging gas connections.

2242. They may be separately purged.

2243. Equipment contained therein may be protected by other approved means.

225. I f the enclosure is opened or if a failure occurs within the purging system pressure may not be adequate to exclude the entrance of flammable vapors or gases. Suitable preca/ltions such as indicators, interlocks, ete., must be provided to safeguard the instal. lation . . . .

226. The purging supply'shaU be essentially free of dust and liquids, which can plug small openings. I t shall contain no more than trace amounts of flammable vapors or gases.

2261. Air of fiormal instrument quality is acceptable as are other suitable supplies such as inert gas.

NOTE: Ordinary" plant compressed air is usually not suitable.

2262. The compressor suction line should preferably not pass through any area having hazardous atmospheres. The compressor intake must be located in a nonhazardous area.

2263. I f the compressor suction line.passes through a hazardous area, it must be of noncombustible material suitably protected against mechanical damage and corrosion.

2264. The compressor suction line must be designed to pre. vent leaks which might permit hazardous vapors to be drawn into the compressor.

227. When double purging is used, i.e., a room ventilated to make it Division 2 and containing a device with open contacts protected by purging, the two sources of air must be independent or automatic shutdown must be provided. •

INSTRUMENTS 173

496-9

23. Specific Requirements for T y p e Z Purging

NOTE: Type Z purging reduces the classification within an enclosure from Division 2 to nonhazardous. A hazard is created under Type Z conditions only if the purge should fail at the same time the area which is normally nonhazardous becomes hazardous. Because of this, it is not considered essential to remove power from the equipment upon failure of the purge but onl.y that adequate warning .must be provided to prevent continuing operation without purge protectmn.

231. Before power is turned on, at least four enclosure volumes of purge gas must have passed through the enclosure while main- raining an internal enclosure pressure of at least 0.1 inch of water.

NoTs: Any time the enclose/re has been opened or the purging gas removed, there exists the possibility that explosive .gases or vapors have accumulated within the enclosure. For enclosures effectively divided by internal parts into two o r more separate spaces a greater purge volume may be advisable.

2311. EXC~PTION: Power may be turned on immediately if a pressure of at least 0.1 inch of water exists and if the atmosphere within the enclosure is known to be nonhazardous.

232. The enclosure must be maintained under a positive pressure of not less than 0.1 inch of water when the power is on.

NOTE: The reason for requiting that a positive pressure be maintained is to prevent flammable vapors or gases from being forced into the enclosure by external air velocities.

233. Under normal operation the external enclosure temperature or the temperature of the egress air shall not exceed 80 percent of the ignition temperature ( °C) of the vapor or gas involved as determined by Method of Test for Autogenous Ignition Tempera- tures o f Petroleum Products, A S T M D286.

NoT~-: In the event that an external enclosure temperature in excess of the jgnition temperature of the gas or vapor involved existed, it is obvious the purging cannot lJrevent an explosion; therefore, it is essen- tlal that-excessive surface temperature be prevented.

234. Safety interlocks to remove power upon failure of purging supply are n o t required.

235. Acceptable installations are shown in Figures No. 1, 2, and 3.

236. An alarm or indication of purge system failure must be provided. The device may be mechanical , pneumatic or electric, and the signal may be audible or visual.

2361. I f electrical, it must meet the requiremehts for its loca- a0n.

174 496-10 PURGED ENCLOSUREs

Warni . , I Nameplate Enclosure

Restrictions may or ..~ may not be provided ....,v' .~ as desired provided ~. basic requirements ~ .[ ~ Flow are met. l ' Indicator

/ Purging _ _ ~ ) Supply

F x o u ~ I

Warning Nameplate~_~_

Pressure II Alarm o r ' ~ J ] . Indicator - ( ~

Purging Supply

I I"nclostlre

Fmu~ 2

Ai, " / ~ \

P,essure Ga~ [I

~Varniag Nameplate

Enclosure

Restriction B

Passages in " 8 " not smaller than passages in "A"

Restriction A

Supply

FXoURB 3 Acceptable installations for Types Y and Z purging

2362. To avoid plugging when a pneumatic device is used, any restrictions between the pneumatic device and the enclosure shall have passages no smaller than the smallest passage before the pneumatic device.

2363. If a pneumatic indicator is used, no valve between the device and the enclosure shall be permitted. ~

2364. The pressure or flow device must be capable of indicat. ing (or actuating an alarm) when the purging pressure o r flow is inadequate to maintain a static pressure within the enclosure of at least 0.1 inch of water.

237. A red warning nameplate must be mounted on the enclosure. The nameplate shall be mounted in a prominent location

175 IN STRUMENTS 496-11

f

and be visible before the enclosure is opened. I t shall state: Enclosure shall not be opened unless area is known to be nonhazardous or unless the power has been removed from all devices within the enclosure. Power shall-not be restored after enclosure has been opened until enclosure has been purged for X minutes.

NoTE : The manufacturer is to recommend purge conditions and flow rate necessary to pass at least four enclosure volumes in the stated time X.

238. The maximu m operat ing temperature of any internal surface exposed to the atmosphere within the enclosure shall not exceed 80 percent of the ignition temperature (°C) of the gases or vapors involved, as determined by A S T M D286, except that :

2381. I f any temperature exists over 80 percent of the ignition temperature of the g~es or vapors involved , then

(a) The warning nameplate shall contain a statement that such conditions exist and that power must be removed for X minutes (period to be determined and specified by the manufacturer to be sufficient to permit unit to cool to safe limit) before the door is opened unless the area is demonstrated to be nonhazardous at the time, or :

(b) The hot component may be separately housed,so that the surface temperature of its housing is below safe limits. This housing shall be purged or sealed and provided with a warning nameplate stating that.its cover may not be removed for X minutes (period to be determined and specified by the manufac turer to be sufficient to' permit unit to. cool to safe limit) unless the area is demonstrated to be n0nhaza/,dous a t the time.

24. Specific Requirements for. Type" Y Purging

NOTE: Type Y purging reduces the classification within an ericlosure from Division 1 to Division 2. The equipment that can be included within the enclosure under Type Y conditions must be suitable for Division 2. This requires that it does not normally contain a source of ignition. Thus, a hazard is created within the enclosure only upon failure of the purging system simultaneously with a failure of the internal equipment causing it to produce a source of ignition. Therefore, it is not considered essential that on failure of the purging system the power be automatically removed from the equipment but that a warning be provided to prevent continuing operation without purge protection.

241. All requirements in 231 to and including 237 must be met.

242. Equipment shall conform to the requirements for Division 2 locations. ,

NoTe: The requirement for equipment to be used in Division 2 Iota- tions is that it should not normally contain a source of ignition. Such sources of ignition may be make-and-break contacts or high surface temperatures in contact with the atmosphere which may become hazardous.

176 496-12 PURGED ENCLOSURES

243. Specific requirements are:

2431. Make-and-break or sliding contacts shall be either ira. mersed in oil, or enclosed within a chamber hermetically sealed against the entrance of gases or vapors, or in circuits which under normal conditions do not release sufficient energy to ignite a specific hazardous atmosphere mixture.

NOTE: Examples of contacts normally operating at energy levels which would not cause ignition are: slide-wire and switching contacts in thermocouple circuits, resistance thermometer, strain gauge and pH electrode, etc.

2432. The maximum opera t ing temperature of ' any surface exposed to the atmosphere within t he enclosure +shall not exceed 80 percent of the ignition temperature (°C) of the gases or vapors involved, as determined by A S T M D286.

2433. I f any temperature exists over 80 percent of the igni. tion temperature (°C) of the gases or vapors involved, the surface having this temperature shall be enclosed within a chamber hermetically sealed against the entrance of gases or vapors.

NOTE: Internal temperatures above the ignition temperature of the gas or vapor involved, such as vacuum tube filaments, are .hermetically sealed to prevent them from normally coming in contact with the atmosphere which may become hazardous. It is essential, that in such enclosures the surface of the glas-~ envelope, which does come in contact with the atmosphere, not have.a temperature in. excess of 80 percent of the ignition temperature of the gas or vapor involved.

NOTZ: If the conditions specified under 242 and 243 are met, the equipment can be located in a Division 2 location in a general ptirpose enclosure without purging.

25. Specific Requirements for Type X Purging

NOTE: Type X purging reduces the classification within an enclosure from Division 1 to nonhazardous. Because the probability of a hazardous concentration of gas or vapor external to the enclosure is high and the enclosure normally contains a source of ignition, it is essential that any disruption of the purging will result in the removal of power from the equipment. Also, it is essential that the enclosure be tight enough to prevent escape of molten metal particles or sparks.

251. •A timing device must be incorporated to prevent power from being applied until after the elapse of a time sufficient to permit at least four enclosure volumes of purge gas (ten for motors) to have passed through the enclosure• while maintaining an internal pressure of at least 0.1 inch of water. The timing device must meet the requirements of its location.

177 IN STRUMENTS 4 9 6 - 1 3

NOTE: The manufacturer is to recommend purge conditions and flow rate necessary to pass four enclosure volumes in a stated time.

252. The enclosure must be +maintained under a positive pressure of not less than 0.1 inch of water when the power is on.

253. A device must be incorporated to-remove potential automatically from all circuits within the enclosure not suitable for Divi- sion 1 upon failure of the purging supply. (Refer to 257.)

254. A door switch must be provided to remove potential automatically from all circuits within the enclosure riot suitable for Division 1 if the enclosure can be readily opened without the use of a key or tools. The door switch, even though located within the enclosure, must be suitable for Division 1+-locations.

NOTE: It is considered essential that any door or other opening which can be opened by untrained people without tools be protected with door interlock switches. Consistent with the practice which has been established with explosionproof enclosures," it is considered that the commonly displayed warning nameplate is adequate protection for the enclosure that can only be opened by the use of suitable tools.

255. The maximum operating temperature of any +surface exposed to the atmosphere within the enclosure shall not exceed 80 percent of the ignition temperature (°C) of the gases or vapors involved, as determined by ASTM D286.

2551. If any temperature exists over 80 percent of the ignition temperature (°C) of the gases or vapors involved, the surface having this temperature shall be enclosed within a chamber hermetically sealed against the entrance of gases or vapors.

NOTE: Because the source of ignition caused by high temperature is not immediately removed by cutting off power to the equipment, it is considered essential that no surface temperature approaching the ignition temperature of the gas or vapor involved should be permitted to come ia contact with the internal enclosure atmosphere.

2552. Equipment such as motors, transformers and other equipment which may be overloaded shall be provided with appropriate devices to detect any increase in. temperature of the equipment beyond design limits and t o de-energize the equipment automatically.

256. Acceptable installations are shown in Figures No. 4, 5, and 6.

257. The power cutoff switch provided to remove power upon failure of the purging system shall-be either flow or pressure actuated.

Enclosure

• Restriction Pressure Optional ' / . f ]

. Actuated Cut-off Restrictions may; ( Switch or may not'be- ~ _

'provided as desired provided .

Purging Supply ~

Enclo6urn

Warning ~

F,OURE 4

-- -- Restriction B . --

~ . ~ " Flow Passages \ Actuated in "B" ! J Cut-off not "'- "

Switch smaller. than

• pas. in "A"

Restriction A . . . .

P ; ing ,_ - Purling. !., "Supply ~ 1.. _ Supply

FIouRB 5

Acceptable installations for Type X purging

Enclosure Safe

Warning. ~ _. ~ ! " N~m~inte - -~ '~L__~ ] Air

] I Pressure Plugged F~lure

Pressure Actuated Cut-off Switch

-. Cutting Off on Low or .High Conditions.

FmuP.s 6

,- 7 . • arebaSJCmetrequirement~

C 0 t~ C

0

179 I N S T R U M E N T S 4 9 6 - 1 5

2571. I t must conform to the requirements of its location.

2572. To avoid plugging when a pneumatic device is used, any restrictions between the device and the enclosure shall have passages no smaller than the smallest passage before the device.

2573. I f a pneumatic device is used, no valve .between the device and the enclosure shall be permitted.

2574. The pressure or flow device of Figure 4 and Figure 5 must be capable of cutting off power when the purging pressure or flow is inadequate to maintain a static pressure within the enclosure of at least 0.1 inch of water.

2575. The pressure device of Figure 6 must be capable of cutting off power if pressure exceeds, or falls below a predetermined safe range.

258. A red warning nameplate must be mounted o n t h e instrument. The nameplate shall be mounted in a prominent location and be visible before the enclosure is opened. I t shall state:

Enclosure shall not be opened or any cover removed .unless area is known to b e nonhazardous or unless the power has been removed from all devices within the enclosure. Power shall not be restored after enclosure has been opened until enclosure has been purged for X minutes.

NOTE: The manufacturer is to recommend purge conditions and flow rate necessary to pass at least four enclosure volumes in the stated time X.

. j •

180 496-16 PURGED E N C L O S U R E S

CHAPTER 3. CONTROL ROOMS

31. Scope

311. These requirements apply to buildings or portions of build. ings, commonly referred to as control rooms, when located close to areas which may contain flammable atmospheres.

32. Control Room

321. Control rooms commonly house one or more of the follow. ing facilities:

Process control instruments and panels. Data processing equipment. ~ Communicatmns equipment. Electrical lighting and electrical power equipment and controls. Emergency power-producing equipment to serve lighting and con-

trol devices. Lunch, restroom and locker facilities for operating personnel. Offices for process supervisors and technical personnel. Maintenance facilities for calibration and repair of process in.

struments and control devices. Heating and ventilating equipment.

322. In processes which can create hazardous atmospheres, the control rooms may serve as a separated location for devices capable of releasing sufficient electrical or thermal energy to cause ignition.

323. If the control room is located in a hazardous area, it must be designed to prevent the entry of flammable liquids and flammable atmospheres. To prevent the entrance of flammable liquids may require differences in elevation and/or the use of dikes, etc. To prevent the entry of flammable atmospheres positive pressure ventilation from a source of clean air may be used and the equipment in the building need not be housed in special enclosures for safe operation.

33. Considerations Relating to Positive Pressure Ventilation

331. Factors to be considered in designing a control room suitable for safe operation in hazardous atmospheres are:

The number of people to be housed. The type of equipment to be housed.

181 CONTROL ROOMS 496-17

f

The location of the control room in relation to the process units, including the location of relief valves and vent stacks, and the direction of the prevailing .wind.

3311. The source of air f o r purging control rooms shall be free of hazardous concbntrations of flammable vapors and gases, contaminants and any other foreign matter. Air filtering may be desirable. ,,

Norg: The source of air must be determined from the nature of the process and the physical layout. Ordinarily air can be taken from an area to one side of a process area where there is a minimum chance of flammable vapors being found. The elevation of the fan suction de- pen& on the density of the flammable gases or vapors under handling temperatures and adverse atmospheric conditions. For a control room in the center of a process, ducting may be necessary. Ducting must be constructed of noncombustible material. The fan suction line must be free of leaks and given suitable protection from mechanical damage and corrosion to prevent hazardous concentrations of flammables from being admitted to the control room.

3312.' A minimum number of doors should b'e provided so that positive pressures can be maintained, while at the same time the number of doors should be adequate for safe exit.

3313. The air system should be designed to provide positive- pressure ventilation for all areas of the room. ,

3314. Monitoring devices such as gas analyzers or similar devices m a y be needed tO detect' flammable vapors and gases and give suitable warning. ~ ':

34. Requirements for Positive Pressure Air Systems

341. The positive pressure ,air system shall:

(a) be capable of maintaining a pressure of at least 0.1 inch of water in the control room with all openings closed, and

(b) be capable of providing a minimum outward velocity of 60 feet per minute through all openings. All doors and windows capable of being opened shall be considered as open, and an allowance for other openings shall be included.

3411. The positive pressure air system may include heating, ventilating and air conditioning equipment plus any auxiliary equipment found necessary to comply with the above.

342. If there is an air-consuming device in the control room, sufficient air must be supplied to handle its needs plus the needs of the positive pressure air system requirements or the air must be taken from a separate source.

182 496-18 PURGED'ENCLOSUREs

343. I f Type X purgiiag is required~' all powe r to "the control room must be automat ica l lyshut down upon air system failure. Cutting off power to the control room 'may shut down the process, and this fact must be considered. For ,Types Y and Z purging, shutdown of power to the control room is not required,

' 3 4 4 . The positive pressure air system failure should be sensed by the discharge pressure of air from the fan and be signaled by a visible or audible alarm. ,.:

NOTE: Velocity pressure switches, static pressure sensing devices and plenum chambers with orifices to provide sufficient pressure to be sensed have been used. Electrical interlocks on the fan motors are not adequate in the event the fan belt slips, the fan impeller becomes loose on the shaft or if the fan rotation is backwards."

345. Provisions must "be made to energize the" control room safely after an air system interruptiim. Such provisions are:

, 3451., Check with a , f lammable ,vapor indicator to .determine when it is safe to energi/e the control room.

3452. Provide a switch, motor and disconnect for t h e fan suitable for the area as it w6uld be classified in the "absence of positive pressure ventilation.

3453. ' An enforced purge wherein an interlock system requires proof of purging for a set period of time prior to energization should be considered if warranted by the conditions.

3454. The electrical power for the air system fan must be taken off the power line ahead of any disconnects that must be energized to return power to the control room.

POWER EQUIPMENT ENCLOSURES 183

496-19

CHAPTER 4. POWER EQUIPMENT ENCLOSURES

41. Scope

411. Chapter 4 applies to equipment enclosures .exceeding 10 cubic feet in volume but not.control rooms. For enclosures with a volume of ]0 cubit feet or less see Chapter 2; for control rooms see Chapter 3.

412. For purposes of purging, electrical power equipment can be divided into two groups:

4121. PURGED EQUIPMm~T. Equipment, such as switchgear and motor controllers, which does not require air flow for heat dissipation, .but which requires pressurization to prevent entrance of flammable gases or vapors.

4122. VENTILATED EQUmMENT. Equipment, such as motors, which requires air flow for heat dissipation.

42. Requirements for Purged Equipment 421. ThE enclosure shall be :of 'substantial noncombustible

construction and reasonably ,tight. Gaskets are permissible .. . .

422. T h e source o f air shall be free of hazardous c0ncentra- tions of flammable vapors and gases, contaminants and any other foreign matter . . . .

423. Piping for air or inert gas supply (if used) should be protected against mechanical damage.

424. Whether the type of purging is X, y or Z, before power is turned on at least ten enclosure volumes of purge gas must have passed throug h the enclosure while internal enclosure pressur~ .of 0.1 inch of water or more is inaintained. This pressure shall be maintained continuously , except that:

4241, In the cases of Y and Z purging, power may be turned on immediately if a pressure of at least 0.1 inch of water exists and if the atmosphere within the enclosure is known to be nonhazardous.

425. Under normal operating conditions the external enclosure temperature or the temperature of the egress air shall not exceed 80 percent of the ignition temperature (°C) of the vapor or gas involved as determined by Method of Test for Autogenous Ignition Temperatures of Petroleum Products, ASTM D286.

184 496-20 P U R G E D E N C L O S U R E S

426. In the case of loss of pressurization, power to the equi,,

• * rt:

ment shall be removed immediately in the case of X purging, unl~[- immediate interruption of power would result m a condition rno'~ hazardous than that created by failure to remove the power imme, diately. In this case an audible as well as visual alarm suitable for the area shall be energized. In the cases of Y and Z purging, loss of .pressurization shall energize an audible as well as a ,visual alarm. Removal of power is not mandatory in the cases of Y and Z purging failures.

427. A red warning nameplate must be mounted on the enclosure. The nameplate shall be mounted in a prominent location and be visible before the enclosure is opened. I t shall state:

Enclosure shall not be opened unless area is known to be nonhazardous or unless the power has been removed from all devices within the enclosure. Power shall not be restored after enclosure has been opened until enclosure has been purged for X minutes.

NOT~.: There should be a flow rate to pass at least ten enclosure volumes in the stated time X.

428. T h e maximum operating temperature of any internal surface exposed to the atmosphere within the enclosure shall not exceed 80 percent of the ignition temperature (°C) of the gases or Vapors involved, as determined by ASTM D286, except that:

4281. I f any temperature exists over 80 percent of the ignition temperature of the gases or vapors involved, t h e n

(a) The warning nameplate, shall contain a statement that such conditions exist and that power must be removed for X minutes (period to be determined and specified by the manufacturer to be sufficient to permit unit to cool to safe limit) before the door is opened unlessthe area is demonstrated to be nonhazardous at the time, or:

(b) The hot component may be separately housed so that the surface temperature of its housing is below safe limits. This housing shall be purged or sealed and provide d with a warning nameplate stating that its cover may not be removed for X minutes (period to be determined and specified by the manufacturer to be sufficient to permit unit to cool to safe limit) unless the area is: demonstrated to be nonhazardous at the time.

4282. For Type X purging, equipment such as motors, transformers and other equipment which may be overloaded shall be provided with appropriate devices to detect any increase in tempera-

P O W E R E Q U I P M E N T E N C L O S U R E S

185 496-21

i

t~t~ of the equipment beyond design limits and to de-energize the L~luiprnent automatically.

43. Requirements for Ventilated Equipment

431. The enclosure shall be noncombustible construction with -essary openings limited to minimum practical size and kept

I lec . as airtight as possible.

432. The enclosure shall be purged by at least ten (10) air changes before the electrical equipment is energized. The auxiliary air equipment must be suitable for the location.

433. The enclosure shall be constantly maintained at a pressure of at least 0.1 inch of water above the surrounding atmosphere during operation of the equipment.

434. The source of air for ventilation shall be free of hazard- 0us concentrations of flammable vapors and gases, contaminants and any other foreign matter. Air filtering may be desirable.

435. Air discharge from the enclosure shall be to an area classified nonhazardous or Division 2.

436. The flow of air should be as uniform as possible within the enclosure so as to avoid, or at least minimize, air pockets.

437. The flow of air must be adequate to keep the equipment adequately cooled depending on the operating design requirements. The air required for cooling will be more than that required for purging.

438. The maximum operating temperature of any surface exposed to the atmosphere shall not exceed 80 percent of the ignition temperature (°C) of the gases or vapors involved, as determined by ASTM D286.

439. The electrical circuits of the equipment within the enclosure shall be interlocked with the ventilating equipment so that:

(a) The equipment cannot be energized until the purging cycle has been completed.

(b) The equipment will automatically shut down when t h e ventilating equipment stops unless shutting down the equipment can produce unsafe conditions; then an audible as well as a visible signal should be sounded so corrective steps can be taken.

186 GENERAL PROVISIONS- 493-5

Part nX Proposed Tentative Standard for

Intrinsically Safe Process Control Equipment for .Use in

Hazardous Locations NFPA No. 493-PT

C H A P T E R 1. GENERAL PROVISIONS

11. Object and Scope

111. The object of this standard is to provide information for the design and evaluation of equipment depending for safety on limitation of energy to be used in hazardous locations as defined in Article 500 of the National Electrical Code. It is not' an instruc. tion manual for untrained persons but~-is intended to promote uniformity of practice among those skilled in the art.

12. Equipment and Locations Covered

121. This standard applies to locations where flammable gases or vapors may be present in air in concentrations sufficient for the location to be classified as hazardous.

122. This standard applies to process control equipment including instruments for measurement, recording and/or control of process variables and to auxiliary devices used therewith such as primary elements, converters, transducers and valve operators.

13. Location Of Equipment

131. Electrical equipment should be located in an area having as low a degree of hazard classification as practicable.

132. There are two types of hazardous locations: those normally hazardous (Division 1), and those hazardous only under abnormal conditions (Division 2).

133. In evaluating safety all interconnected units must be considered. Even though most elements of a process control loop can be (and should be) located in a Division 2 or non-hazardous location they must still be examined to be sure that even under fault conditions they cannot feed dangerous energy to the elements in the hazardous area.

134. Apparatus operated from normal 120 volt line power must have the line power-operated portion of the circuit and appropriate

INTRINSICALLY SAFE EQUIPMENT 187,

energy limiting, components located outside of the Division 1 hazardous location, have them mounted in explosionproof enclosures, or otherwise protected.

135. Battery-operated appar'atus must have the battery and energy limiting ~omponents located outside the Division 1 location, have them mounted in' an explosionproof enclosure; have current limiting means as an integral part of the battery, or be so constructed that a direct short circuit of the battery is virtually impossible.

14. Definitions

141. "INTRINSICALLY SAFI~ EQUIPMENT AND WIRING is equipment and wiring that is incapable of releasing sufficient electrical or thermal energy under normal or abnormal conditions to cause ignition of a specific hazardous atmospheric mixture in its most easily ignited concentration. This equipment is suitable for use in Division 1 locations.

142. NONINCENDIV'E EQUIPMENT is equipment that in its normal operating condition would not ignite a specific hazardous atmosphere in its most 'easily ignited c0ncentration. The circuits may include sliding or make-and-break contacts releasing insufficient energy to cause ignition. Circuits not containing sliding or make- and-break contacts may operate at energy,levels potentially capable of causing ignition. This equipment is suitable for use in Division 2 locations.

143. DIvisioN 1 LOCATIONS are those (1) in which hazardous concentrations of flammable gases or vapors exist continuously, in- termittently, or periodically under normal operating conditions; (2) in which hazardous concentrations of such gases or vapors may exist frequently because of repair or maintenance operations or because of leakage; or (3) in which breakdown or faulty operation of equipment or processes which might release hazardous concentrations of flammable gases or vapors might also cause simultaneous failure of electrical equipment.

144. DivisioN 2 LOCATIONS are those (1) in which volatile flammable liquids or flammable gases are handled, processed or used, but in which the hazardous liquids, vapors or gases will normally be confined within closed containers or closed systems from which they can escape only in case of accidental rupture or breakdown of such containers or systems, or in case of abnormal operation of equipment; (2) in which hazardous concentrations of gases or vapors are normally prevented by positive mechanical ventilation, but which might become hazardous through failure or abnormal operation of the ventilating equipment; or (3) which are

]188 GENERAL P R O V I S I O N S " ' . - 493-7

adjacent to Division 1 .locations, and tO which hazardous concentra. tions of gases or, vapors might occasionally be communicated Unless such communication is prevented by adequate positive-pressure yen. tilation from a source of clean air, and effective safeguards against ~,entilation failure are provided. , •

145: MINIMUM IGNITION ENERGY. is the smallest amount of energy that can cause ignition-of a specific gaseous mixture at normal room temperature and pressure. Tests made at high voltage by discharging capacitors through pointed electrodes give the lowest energy measurements; such data are believed to approach the true minimum ignition energy.. The ignition energy will decrease as temperature or 'pressure 'or both are iricreased.. " - '

146. A FAULT is any .abnormal condition which, alone or in • combination with others; may affect the electlical charac'teristics of the circuit. : ~

1461. An obvious fault is one which would be indicated by an audible or visible signal, abnormal meter reading; or some mal- functioning of the equipment necessitating..correction before pro- ceeding with further operation of t h e equipment. ~ , ~

1462.' A nonobvioiJs fault is one Which woul(t n o t b e ex;ident to the user in the normal operation of the"equip'ment.

i

I t "

493 -8 INTRINSICALLY .SAFE EQUIPMENT ]t89

CHAPTER 2. FUNDAMENTAL CONSIDERATIONS

21. General : .

211. T o b e intrin'sically safe two conditions, must be met. (a) The-energy available 'in ,the hazardous area must be low

enough under normal conditions so that it is incapable of igniting the specified hazardous atmospheric mixture due to arcing or increased f e m p e r a t t i r e . . "

(b) The energy available iri the hazardous area must be low enough under abnormal conditions i.e, with assumed fault conditions, so that it is incapable of igniting the specified, hazardous atmospheric mixture due to arcing or increased temperature. :.

212. Intrinsically safe apparatus must be incapable of causing ignition with the following combination of. conditions: -.

(a) Line voltage is at maximum value. (b) All adjustmen~ are at most unfavorable settings. (c) Field wiring is subject to shorting, opening and grounding. (d) The most unfavorable combination of component failures

and internal circuit faults has occurred as outlined below. '-

22. Number of Faults

221. The equipment must be incapable of causing ignition with three concurrent faults. Failure of the field wiring is counted as one obvious fault.

Exception: For equipment having normally operating contacts in the Division 1 location, failure of field wiring is not counted as one of the faults.

Exception: Only two concurrent obvious faults need be considered.

222. If one fault "may cause failure of other components, the combination shall be considered as a single fault.

190 E V A L U A T I O N 493-9

CHAPTER 3.. EVALUATION

3L The Three Steps of the Evaluation Procedure

311.. Circuit analysis to determine the effect of each possible fault and combination of faults in accordance with 22. This may be.done either theoretically or empirically. In the theoretical approach, circuit analysis consists of assuming vari'ous fault conditions and calculating resulting voltages and currents. Alternatively, in the empirical approach, faults are actually created and the. resulting voltages and currents are measured.

312.' Determination of possibility of ignition under "normal conditions and under the worst fault conditions found in 311. This may be done in either of .two ways:

(ai Testing the circuit by .opening, closing and short circuiting field leads in the presence of an explos!ve mixture. See Chapter 4.

(b) Comparing the measured values of current, voltage and asso- ciated inductances and capacitances with the results of previous tests. See 'Chapter 5.

313. Review of construction details to be sure that circuit analysis is valid. See Chapter 6.

I ~ . ~ , " . "

493-10 INTRINSICALLY SAFE EQUIPMENT 191

C H A P T E R 4. TES T APPARATUS AND PROCED U RE

41. General

41!. The test consists of simulating'the effect Of opening, closing and short circuiting that part of the field w!ring to be loca ted in the hazardous area. To provide a margin of safety over actual field conditions, specialized apparatus with contacts designed to have maximum effectiveness is used rather than the contacts used in the field• The contacts are operated in a chamber filled with the most readily ignited mixture of a suitable test gas with air. Fault conditions are simulated during the test. Various methods are used to add a further factor of safety. .

42. Test Apparatus 421. The device consists of an explosion chamber of about 250

cubic centimeters volume; in which eii'cuit-making-and-breaking sparks are produced in the presence of the prescribed test. gas. Gomponents of the contact arrangement are a brass disc with 2 slots and 4 tungsten wires of 0.2 mm diameter, which slide over the disc. The free length of the tungsten wii'es is 11 ram. The driving, spindle, to which the tungsten wires are attached, makes 80 revolutions a minute. The spindle on which the brass disc 5s mounted revolves in the opposite direction• The ratio of the speeds of the drivingspindle to the other spindle is 50 to 12. The spindles are insulated from one another and from the housing. The explosion chamber must withstand pressures up to 15 kg/cm 2 gage.

Figure I; Test "apparatus for' evaluating intrinsically Safe-circuits. Measurements are in millimeters.

192 T E S T APPARATUS AND PROCEDURE 493-11

NOTE: This is the apparatus described in VDE 0170/0171d/2.65. but with a brass instead of a cadmium disc. (See Figure 1.) With a brass disc the apparatus gives results comparable with those obtained with break flash apparatus and intermittent break apparatus described in British Standard 1259 (1958) as amended, and to the results obtained With the two types of apparatus described in Subject 35 of Un-

• derwriters' Laboratories Inc., but it: does it with one reliable and convenient unit. Any test apparatus using fine wires gives trouble at currents approaching 10 amperes. 'For such testing heavier wires or a different type of apparatus ma~, be needed.

43. Gas Mixtures

431. For purposes o f intrinsic safety hazardous • materials are divided into three groups designated by the name of the character. istic material as Pentane Group, Ethylene Group, and Hydrogen Group.

NOTE: These groups roughly but not precisely follow the explosion. proof Groups D, C and B. The Appendix contains lists of chemicals

• under the-Pentane, Ethylene, and Hydrogen Groups. These groupings were originally used by the British authorities. "

4311. For the Pentane Group the test mixture 'shal l be 3 .9~ 0.2% pentane in air, or 5.25 ± 0 . 2 5 % propane in air.

4312. For the Ethylene Group the test mixture shall be 7.8 ___0.3% ethylene in air.

4313. For the H y d r o g e n Group the test mixture shall be 21 ___ 1% hydrogen i n air.

44. Check of Test Appara tus

441. Before the experimental test of a circuit is" made it must be ascertained that sparks with adequate ignition probability can be produced with the testing device. This is done by trying the device in a reference circuit. This consists of a source of direct voltage (internal resistance less than 1 ohm) with 24-volt terminal voltage,

an air-cored coil wi th an inductance of 95 millihenries a n d a low- inductive current-limiting resistor. The testing device is so connected into the reference circuit that the tungs tenwi re electrodes are positive. For the test With the propane-air mix tu re the current should be 160 milliamperes, with the ethylene-air mixture 110 milliamperes, and with the hydrogen-air mixture 70 milliamperes. The testing device meets requirements if with 10 minutes of operation (approximately 3000 sparks) ~t least one ignition occurs.

#VDE 0170/0171d/2.65 is the West German "SlSecifieations for Intrin- sically Safe Apparatus," published by Verband Deutscher Electrotechniker (VDE) e.V. VDE is an organization similar to :the Institute of Electrical

and Elect/dnics Engineers, I ~ : ' " "

493-12 INTRINSICALLY SAFE EQUIPMENT

1'93

45. Test Conditions

451. Tests shall be carried out with 110% of the rated supply voltage and in addition either

4511. At approximately 1.5 times the actual current by shunting each current limiting resistor with a resistor of double its value, or

4512. At both increased current and voltage by increasiflg the 110% supply voltage by a factor of 1.25.

452. Tests shall be carried out using the most easily ignited inixture.

453. Tests shall be run for each DC condition for 1 ~ minutes (approximately 500 sparks) at each polarity and shall not produce ignition. " ' "

454. Tests shall, be run for each AC conditibn for 6 minutes (2,000 sparks) and shall not produce ignition. :

194 COMPARISON PROCEDURE 493-13

CHAPTER 5. COMPARISON PROCEDURE

51. General

511. Apparatus having energy levels under normal and abnor. mal conditions well below the known ignition limits, and conform. ing to fault criteria more stringent than for testing, is considered intrinsically safe without actual ignition test. This method is pri- marily applicable to the simpler circuits. Transients in complex circuits are not readily analyzed. Such circuits are therefore best evaluated by actual test.

52. Ignition Limits

521. The following ignition limits have been established using the most easily ignited mixture and using circuits, components and contact conditions shown to be efficient in producing ignition. They represent actual data, and include no safety factor other than that inherent in the improbability of such conditions occurring in actual practice. Some circuits operating beyond these limits can be shown by ignition testing to be safe.

NOTE: The higher voltage lines in Figures 3-7 (shown dotted) have been sketched in, assuming similarity with Figure 2, for which data are completely known. Though admittedly imprecise, these are considered adequately accurate for use with the recommended factor of four on current.

5211. Reslstance-Inductance Circuits (a) Figure 2, applying to inductive and resistive circuits only,

shows combinations of inductance, voltage and current only, which will not ignite Pentane Group gases or vapors.

(b) Figure 3, applying to inductive and resistive circuits, shows combinations of inductance, voltage and current, which will not ignite Ethylene Group gases or vapors.

(c) Figure 4, applying to inductive and resistive circuits only, shows combinations of inductance, voltage and current, which will not ignite Hydrogen Group gases or vapors.

5212. Resistance-Capacitance Circuits (a) Figure 5, applying to capacitive and resistive circuits,

shows combinations of capacitance, voltage and current, which will not ignite Pentane Group gases or vapors.

(b) Figure 6, applying to capacitive and resistive circuits, shows combinations of capacitance, voltage and current, which will not ignite Ethylene Group gases or vapors.

Continued on page 17

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198 COMPARISON PROCEDURE 493-17

(c) Figure 7, applying to capacitive and resistive circuits, shows combinations of capacitance, voltage and current, which will not ignite Hydrogen Group gases or vapors.

53. Maximum Voltage and Current Levels

531. Maximum voltage and current levels in intrinsically safe circuits approved without ignition testing are listed in Table 1 as a percentage of the current determined from Figures 2, 3 and 4, or of the voltage determined from Figures 5, 6 and 7 for ,given circuit constants. Higher voltage and current levels are permissible if their safety is demonstrated by test.

Table 1 Normal Conditions- Abnormal Conditions

25 percent 50 percent

532. Normal conditions include: (a) Maximum supply voltage and extreme environmental

conditions within the stated ratings of the equipment, and (b) Shorting, opening or. grounding of connecting wiring in

the intrinsically safe portion of the circuit not supplied as an integral part of the'equipment I being analyzed.

' 533. Abnormal conditions include the "number of faults specified in Article 22. The circuit is intrinsically safe if this number of faults cannot raise the voltage or current above the levels specified in Section 531.

Exception: If two of the faults are highly improbable (see ." Article 63)~ they will not be assumed to fail concurrently.

534. Faults shall include opening or shorting of electrical conductors and components (including resistors, capacitors, vacuum tubes, etc.) o1: insulation breakdown in any portion of the circuit.

Exception: Possible shorts between insulated conductors in any portion of the circuit separated by suitable barriers or secured in place in such a manner as to maintain a space between the insulated conductors shall be considered as a combination of three faults.


C H A P T E R 6. C O N S T R U C T I O N D E T A I L S

61. General Principles

611. In evaluating intrinsic safety it is assumed that any component or structure can and will fail. Safety depends on a muhi- plicity of elements and the improbability of simultaneous failures o r

on such construction of one element that the probability of failure is negligible or that it can fail only in a safe direction. For example, a transformer having the primary and the secondary wound on separate legs of a ,grounded core would be accepted on the basis that the probability of a failure that would put line power on the secondary leads is negligible.

62. Elements Assumed Not to Fail in Fault Analysis

621. A transformer which will pass a high potential test, primary to secondary, of twice rated voltage plus 1,000 volts for one minute after operation for six hours (or until burnout, whichever occurs first) at rated voltage with all secondaries short circuited.

NOTE: Tl~e transformer may or may not burn out. during test. Primary or secondary may short circuit to shield and to core. The transformer shall not ignite during test. Suitable constructions include:

a. High temperature insulation between primary and secondary. b. Separation of windings. c. Sufficient internal impedance to limit current and minimize "over-

heating.

622. ,Wire wound resistors wound o n a ceramic core and with ceramic covering operating at not more. than' 50 percent of normal rating and subject to the follow!ng test:

6221. The resistance of each resistor is measured. Each_res~.stor in turn is connected to a variable alternating current source of supply. The supply voltage is gradually increased until the outside middle surface of resistor attains a temperature of 600 C plus or minus 15 C. -After the resistors are operated at this vol tage for a period of 3 hours, the supply circuit is disconnected, the resistors cooled to room temperature, and the resistance measured. The resistance of the resistors shall not decrease more than 25 percent at the completion of the tests when the resistors have cooled to room temperature. Four samples of each resistor shall be subjected to this test.

623. Wire wound resistors with wire embedded in a plastic operating at not more than 50 percent of normal rating if resistor will stand 5 times fault current for 3 hours with not more than 10 percent decrease in resistance after cooling to roomtempera tu re .

200 CONSTRUCTION DETAILS 493-19

624. Deposited metal or carbon film on a nonconducting, noncombustible core operating at not more than 50 percent of normal rating if resistor will stand 5 times fault current for 3 hours with not more than 10 percent decrease in resistance after cooling to room temperature.

625. Wiring intermingle d within apparatus and thus mechani. cally protected when all wires are fully insulated for the maximum voltage of any circuit. (Does not permit an insulated wire in contact with a bare live part.)

626. Spacings J Measured along surface or through air unless otherwise stated.

6261. Bare live parts in secondary circuits 100 volt amperes or less and not over 150 volts, spaced at least 1/16 inch (150-300 volts, 1/8 inch) from other uninsulated live parts or from m&al either isolated or grounded.

6262. The 1/16 inch spacing referred to in 6261 may be reduced to 3/64 inch when live and other parts are reliably secured as on a suitable printed 'circuit board. (See UL 796, Printed- Wiring Boards)

6263. The spacings referred to in 6261 may be reduced to 1/32 inch if the parts are in.sulated with a suitable plastic or

resin such as epoxy.

627. Two carbon-type resistors in series if the circuit is incapable of causing ignition with half the resistance of one of these resistors.

628. Two capacitors in series that can withstand a dielectric strength test of twice rated voltage plus 1000 volts and the circuit is incapable of causing ignition with half the impedance of one of these capacitors.

629. Two Zener diodes if either one alone can dissipate twice the available power. The Zener diodes shall be of a type which will short under abnormal conditions such as. the application of high voltage to the diodes.

63. Element Failures Assumed Highly Improbable in Fault Analysis (See Section 533)

631. Any device listed in Sections 621-625 inclusive and Sub- sections 6262 and 6263 but not subjected to the tests specified therein.

NOTE: If one 100-ohm resistor meeting the requirements of 622 would

~3-2o I N T R I N S I C A L L Y S A F E E Q U I P M E N T

201 /

make a device incapable of causing ignition, two 100-ohm resistors in series meeting the requirements of 631 would do likewise. The resistor per 622 has a negligible failure probability; two resistors per 631 each singly having a low probability of failure, have a negligible probability of f-ailing simultaneously.

64. Manufacturers' Testing

641. Manufacturers shall employ screening tests on critical components and shall subject the completed process control equipment to a short-time operational test.

65. Marking

651. In addition to the markings required for the particular classification of the equipment, the intrinsically safe equipment or circuit shall be marked "Intrinsically Safe" and with tee hazardous location class and group for which it is found acceptable.

J

652. The cover shall carry a warning label, "Any substitution of components may impair the intrinsic safety of the equipment. See Instruction Manual."

653. Battery-powered equipment shall be marked to indicate the type, voltage, and size of batteries to be used in the equipment.

202 APPENDIX 493-21

A P P E N D I X

M i n i m u m Igni t ion Energy Group ings of Chemicals (These groupings were original ly used by the British authorities)

methane ethane propane'" . ~' butane l:ientane hexane

. benzene toluene xylene

Pentane Group (See 4311)

Hydrocarbons ALKANE

heptane nonane

• cyclobutane ' cyclohexane methylcyelohexane • deca.hydronaphtha!ene

BENZENOm

butene styrene cyclohexane

MIXED HYDROCARBONS

turpentine naphtha coal tar naphtha kerosine petroleum

• " ethylbenzene trimethylbenzene - naphthalene

ALKENE

Compounds Containing Oxygen OXIDES

carbon monoxide methoxyethanol ethoxyethanol

d

ALCOHOLS AND

methanol ethanol propanol butanol pentanol hexanol octanol

ethyldigol butyldigol dibutyl ether

PHENOLS

nonanol cyclohexanol . methylcyclohexanol diacetone alcohol phenol cresol


formaldehyde acetaldehyde octaldehyde paraformaldehyde

ALDEHYDES

paraldehyde benzaldehyde metaldehyde

KETONES

acetones ethyl methyl ketone propyl methyl ketone ' • butyl methyl ketone

amyl methyl ketone acetylacetone cyclohexanone

ESTERS

methyl formate butyl acetate ethyl formate amyl acetate methyl acetate methyl acetoacetate ethyl acetate diethyl oxalate

Compounds Containing Halogens

COMPOUNDS WITHOUT OXYGEN

chloromethane , dichloropmpane chloroethane chlorobenzene hromoethane benzyl chloride chlor0propane dichlorobenzene chlorobutane allyl chloride bromobutane dichloroethylene dichloroethane . , ; .. "

COMPOUNDS WITH OXYGEN

acetyl chloride

Compounds Containing Nitrogen AMINES

methylamine dimethylamine trimethylamine diethylamine triethylamine propylamlne butylamine cyclohexylamine

ethanolamine diethylaminoethanol diaminoethane aniline dimethylaniline amphetamine toluidine py~idine

AMIDES

formdimetl~ylamide

204 APPENDIX 493.23

NITRO-COMPOUNDS

nitrobenzene

Ethylene Group (See 4312)

cyclopropane ethylene

Hydrocarbons

butadiene

Oxides (including ethers & heterocyclics)

dimethyl ether epoxypropane ethyl methyl ether dioxolane diethyl ether trioxan dipropyl ether dioxan ethylene oxide tetrahydrofurfuryl alcohol

Compounds Containing Nitrogen

acrylonitrile isopropylnitrate

Hydrogen Group (See 4313)

hydrogen town gas blue water gas coke-oven gas

Documents

Report of Committee on Chemicals and Explosives - NFPA...ardousChemicals Data, NFPA No. 49 -- 1966. " Part VI has been submitted to ballot of the Sectional Committee on Prop- erties