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Postweld Heat Treatment of Equipment IP 18-4-1

Handling Alkaline Solutions Page 1 of 3

(This practice is appropriate for attachment to Inquiry or Purchase Document) Rev. 2 June 2000

THIS INFORMATION FORAUTHORIZED COMPANY USE ONLYEXXON RESEARCH AND ENGINEERING COMPANY FLORHAM PARK, N.J.

INTERNATIONALPRACTICE

SCOPE

I 1.1 This practice addresses the need for, and performance of, postweld heat treatment for the prevention ofalkaline embrittlement of all welded carbon steel equipment.

I 1.2 An asterisk () indicates that a decision by the Purchaser is required or that additional information isfurnished by the Purchaser.

SUMMARY OF ADDITIONAL REQUIREMENTS

I 2.1 Table 1lists the codes and standard, which shall be used with this practice.

TABLE 1

CODES AND STANDARD

ASME Codes

Section VIII Pressure Vessels, Division 1

B31.3 Process Piping

API Standard

945 Avoiding Environmental Cracking in Amine Units

DEFINITIONS

I 3.1 Metal temperature used herein for the purpose of determining postweld heat treatment (PWHT)requirements, shall take into account all heat sources, e.g., process, heat tracing, solar radiation, and alloperating conditions including transient conditions such as steaming out.

I 3.2 Alkaline solutions referred to herein shall be specified as:

a. Caustics defined as all alkali metal hydroxides such as sodium hydroxide and potassium hydroxide

b. Amines defined as solutions for acid gas absorption or removal of acidic components (i.e., H2S, CO2)

from hydrocarbons and hydrogen streams. These include monoethanolamine (MEA), diethanolamine(DEA), methyl diethanolamine (MDEA) and FLEXSORB amines.

c. Potassium carbonate.

d. Ammonium carbonate/bicarbonate defined as the mixture formed from ammonia and CO2 in process

stream.

EQUIPMENT SUBJECT TO HEAT TREATMENT

S 4.1 The following equipment for handling of caustic solutions shall be postweld heat treated:

a. All equipment provided with heat tracing, with the exception of piping that is heat traced for winterizationpurposes using temperature controlled electrical tracing that will not cause the pipe metal temperature toincrease beyond the limits shown in Figure 1 in the event of controller or tracing malfunction.

b. All equipment containing heating coils not provided with high temperature alarms.

c. All equipment for handling solutions which have coincident metal temperature and concentration perFigure 1.

I 4.2 Postweld heat treatment is not required forequipment handling caustic solutions in concentrations of

1.5% (by weight) or less, or when solutions of any concentration are at atmospheric temperatures.

I 4.3 All equipment handling potassium carbonate, except Catacarb solution or FLEXSORB HP solventeach containing vanadium inhibitor, having a concentration greater than 2% (by weight) shall be postweldheat treated if:

a. The metal temperature exceeds 200F (93C), or

b. The equipment contains a heating coil not provided with high temperature alarms.

If the potassium carbonate solution will be generated in situ from potassium hydroxide, then the equipmentshall be postweld heat treated per the guidelines for caustic given in Par. 4.1.

Changes shown by

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IP 18-4-1 Postweld Heat Treatment of EquipmentPage 2 of 3 Handling Alkaline Solutions

Rev. 2 June 2000 (This practice is appropriate for attachment to Inquiry or Purchase Document)

THIS INFORMATION FORAUTHORIZED COMPANY USE ONLYEXXON RESEARCH AND ENGINEERING COMPANY FLORHAM PARK, N.J.

INTERNATIONAL

PRACTICE

FIGURE 1CAUSTIC SOLUTIONS REQUIRING POSTWELD HEAT TREATMENT

Postweld Heat Treatment Required

Postweld Heat Treatment Not Required

MetalTemperatureF

MetalTemperatureC

Wt% Caustic

50403020100

18085

80

75

70

65

60

50

55

170

160

150

140

130

120

0

180401a

R 4.4 Amine treating. All equipment handling amine solutions such as MEA, MDEA, DEA and FLEXSORBamines, in concentrations greater than 2% (by weight) shall be postweld heat treated, with the followingexemption:

a. Atmospheric storage tanks are exempt from this requirement if metal temperature does not exceed100F (38C), and:

1. The tank does not contain a heating coil, or

2. The tank contains a heating coil and is provided with a high temperature alarm set at 100F

(38C) or less.

R 4.5 Coker and cracker light ends equipment handling ammonium carbonate/bicarbonate mixtures, excludingpiping, shall be postweld heat treated regardless of metal temperature.

I 4.6 This practice shall apply for equipment that may be exposed to alkaline solutions as a result of operationalupsets.

PROCEDURES

I 5.1 For all equipment except field fabricated tanks and piping , the postweld heat treatment procedure

outlined in the ASME Code Section VIII, Par. UW-40, UW-49, and UCS-56, shall be followed, except asspecified below:

a. All thicknesses shall be heat treated and the minimum heat treating temperature shall be 1100F

(595C).

b. The holding time at the minimum postweld heat treatment temperature shall be 1 hour/inch,

minimum of 1 hour.

c. If government codes and regulations require higher postweld heat treating temperatures or longerholding times for appropriate thicknesses, they shall govern.

R 5.2 PWHT is required for equipment handling both wet H2S and amine solutions, and the minimum PWHT

temperature shall be 1150F (621C).

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Postweld Heat Treatment of Equipment IP 18-4-1

Handling Alkaline Solutions Page 3 of 3

(This practice is appropriate for attachment to Inquiry or Purchase Document) Rev. 2 June 2000

THIS INFORMATION FORAUTHORIZED COMPANY USE ONLYEXXON RESEARCH AND ENGINEERING COMPANY FLORHAM PARK, N.J.

INTERNATIONALPRACTICE

I 5.3 For large field fabricated tanks, where it is impractical to perform the postweld heat treatment required byPar. 5.1, lower temperatures may be employed provided the minimum holding time is increased to:

a. 4 hours and 4 hours/inch for a 50F (28C) reduction in temperature, or

b. 10 hours and 10 hours/inch for a 100F (56C) reduction in temperature.

The requirements of Par. 5.1 shall be met in all other respects. Procedures shall be approved by the

Owner's Engineer, and a copy of continually recorded PWHT temperatures shall be provided to the Owner'sEngineer.

R 5.4 Heat treating with manually controlled flames or torches (flame PWHT) is not permitted.

I 5.5 For piping, the postweld heat treatment procedure outlined in ASME B31.3, Par. 331.1 and 331.2, shall be

followed. The exemptions provided in Table 331.1.1 based on nominal wall thickness are not permitted.Socket welded and seal welded threaded connections for all pipe sizes shall also be postweld heat treated.The holding time at the minimum postweld heat treatment temperature shall be 1 hour/inch, minimum of1 hour.

S 5.6 Attachment of clips, brackets, or other devices requiring welding directly to the inside or outside of

vessel or piping walls after postweld heat treatment is not permitted unless the heat treatment is repeated onthe equipment or material after welding.

Revision Memo9/68 Original Issue of Basic Practice

6/71 Revision 1

6/72 Revision 2

6/78 Revision 3

6/82 Revision 4

1/86 Revision 5

9/88 Revision 6

12/93 Revision 7

6/94 Revision 0 - Original Issue of International Practice

3/98 Revision 1

6/00 Revision 2Par. 2.1 added the word Standard to take into account the changes made to Table 1. Table 1 added API 945 as areferenced standard. Par. 4.1a revised paragraph to exempt PWHT for lines electrically heat traced for winterization.Pars. 5.1b and 5.5 changed the minimum PWHT holding time from 45 minutes to 1 hour per API 945 guidelines.

Exxon Research and Engineering Company, 1998, 2000

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