MID-H-251-Process and Utility Piping Design Requirements

7/13/2019 MID-H-251-Process and Utility Piping Design Requirements

1/22

PDVSA N TITLE

REV. DATE DESCRIPTION PAG. REV. APPD. APPD.

APPD.BY DATEDATE

VOLUME 13II

PDVSA, 1983

H251 PROCESS AND UTILITY PIPING DESIGN

REQUIREMENTS

FOR APPROVAL

Alexis Arvalo Jess E. RojasDEC. 98 DEC. 98

ENGINEERING SPECIFICATION

FEB.89

DEC. 98 Y.K.

J.S.

1

0

GENERAL REVISION 21

33

A.A.

J.G.

J.E.R.

E.S.

ENGINEERING DESIGN MANUAL

ESPECIALISTAS

APPD.BY
http://especialistas/h-251.pdfhttp://especialistas/h-251.pdf


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PROCESS AND UTILITY PIPINGDESIGN REQUIREMENTS

DEC. 981

PDVSA H251

Pgina 1

.Men Principal Indice manual Indice volumen Indice norma

Index

1 GENERAL 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.1 Scope 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.2 References 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.3 Regulations 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2 DESIGN 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.1 Piping Layouts 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.2 Clearances 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.3 Materials 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.4 Design Pressures and Temperatures 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.5 Corrosion Allowance 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3 DESIGN DETAILS 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.1 Line and Connection Sizes 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.2 Material Specification Changes 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.3 Flanges 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.4 Screwed Nipples 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.5 Valves 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.6 End Closures 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.7 Blinds 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.8 Bypasses 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4 GENERAL INSTALLATION REQUIREMENTS 8. . . . . . . . . . . . . . . . . .

4.1 Provisions for Expansion and Flexibility 8. . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.2 Supports and Anchors 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.3 Joints and Connections 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.4 Branch Connections 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.5 Valve Installations 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.6 Centrifugal Pump Piping Installations 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.7 Vents and Drains 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5 REQUIREMENTS FOR INDIVIDUAL PIPING SYSTEMS 15. . . . . . . . .

5.1 Requirements for Process Piping Systems 15. . . . . . . . . . . . . . . . . . . . . . . . .5.2 Requirements for Steam Systems 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.3 Requirements for Water and Air Systems 16. . . . . . . . . . . . . . . . . . . . . . . . . . .

5.4 Utility Outlets 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.5 Drainage and Sewage Systems 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.6 Firewater Protection System 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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1 GENERAL

1.1 Scope

1.1.1 This specification covers general requirements for the design of process andutility piping systems and supplements the requirements of the ASME CodeB31.3, Process Piping, under which the piping systems are to be designed.

1.1.2 The number and extent of piping systems to be provided in the plant shall be asindicated on the Piping and Instrument (P&I) diagrams and plant drawings.

1.1.3 Requirements indicated on Piping and Instrument (P&I) diagrams prevail over thisspecification.

1.1.4 This specification does not cover design requirements for liquid transportation orgas transmission pipeline systems outside battery limits.

1.2 References

Latest editions of the following Engineering Specifications and codes form integralpart of this specification, to the extend indicated herein:

1.2.1 Petrleos de Venezuela S.A. (PDVSA)

H221 Piping Materials

H231 Piping Fabrication Requirements

HG251 Pipe Supports Design CriteriaManual de Ingeniera de Riesgos

1.2.2 American Society of Mechanical Engineers (ASME)

B31.3 Process Piping

1.3 Regulations

Should there be any conflict between Venezuelan laws, standards andregulations, this specification and ASME standards, the order of prevalences shallbe as follows:

1. Venezuelan laws, standards and regulations

2. This specification

3. ASME B31.3.

2 DESIGN

2.1 Piping Layouts

2.1.1 All piping shall be routed for the shortest and economical run. Layout shall besufficient flexible to offset thermal effects, in order to avoid:
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a. Failure for excessive thermal expansion stress

b. Flanged joint leakage

c. Excessive loads to connected equipment

2.1.2 Generally all lines, inside battery limits of process units, shall be run on overheadpipe supports. Exceptions are fire water lines and drain lines. New pipe racks shallhave 10 percent of available width unused for future lines.

2.1.3 Lines that cannot be run overhead shall be run on sleepers.

2.1.4 The use of pipe trenches within units shall be avoided.

2.1.5 Lines outside battery limits generally shall be run at grade on sleepers except in

areas adjacent to units where vehicular and pedestrian access is required. forvertical clearance, see paragraph 2.2.1.

2.1.6 Large, thin walled lines in nonflammable service, such as cooling water lines,may be buried and continuously supported on sand cushions.

2.1.7 Piping insulated for Hot Serviceover 3 inches and larger nominal diameter shallnot be supported directly on structural steel or on a round smooth bar welded tostructural steel, and shall be provided with pipe shoes or saddles, with the bottomof the pipe 75 mm (3 inches) above the top of supporting structural steel. Pipeshoes or saddles shall be of sufficient length to handle any possible lineexpansion.

All piping over 3 inches nominal diameter with operating temperature 121C (250F) and over supported directly on concrete sleepers shall be provided with pipeshoes or saddles, with the bottom of the pipe 75 mm (3 inches) above the top ofsupporting concrete. Pipe shoes and saddles shall be of sufficient length to handleany possible line expansion.

2.1.8 Bare pipes shall rest directly on structural steel provided a smooth round steel bar(1/2 or 3/4 inch diameter) be welded on structural steel in order to minimizecontact area and corrosion.

2.1.9 Where possible, all lines shall be run at levels which would enable them to be

supported on structural steel at a common elevation.In process areas, specific elevations shall be selected for lines running north andsouth and other specific elevations for lines running east and west. Theseelevations shall be used throughout the unit, except where pockets must beavoided.

2.1.10 All piping and accessories shall be arranged to facilitate support.

2.1.11 Piping arrangement shall be planned for ease of equipment removal forinspection, servicing and/or maintenance.
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Piping and structures shall be arranged to permit mobile lifting equipment to

approach process equipment and make lifts without obstruction.2.1.12 Maintenance areas shall be clear of piping insofar as possible.

2.1.13 Control valves, relief valves, etc. shall be accessible from platforms or grade andgrouped at main operating levels.

2.1.14 Deflections over 1/2 inch are not permitted in all lines.

2.1.15 All process and utility piping entering battery limits shall be provided with a blockvalve. Piping leaving battery limits shall be provided with block valve with theOwners representative approval only.

2.1.16 Buried pipe shall be externally coated, and provided with cathodic protection if

required.2.1.17 Where a drain valve is required, bottom of pipe (BOP) shall be above ground or

base level so a plug can be easylly installed and/or removed. A 100 mm (4inches) minimum clearance is recommended.

2.2 Clearances

2.2.1 Clearance for equipment, structures, platforms, piping and its supports shall bein accordance with Appendix I.

2.2.2 To permit access for the removal or maintenance of a pipe line, a minimum sideclearance of 25 mm (1 inch) shall be provided between parallel lines, outside of

insulation or between flange and pipe (insulation).

Thermal movements shall be taken into consideration in determining sideclearances.

Clearance for maintenance personnel shall be allowed for removal of interior linesin multiple pipe line racks.

2.2.3 The lowest point of all flanges or insulation on lines run in trenches shall be aminimum of 75 mm (3 inches) above the floor of the trench.

The minimum horizontal walkway clearance between piping and mechanicalequipment shall be 915 mm (36 ft).

2.3 Materials

Materials of construction for individual piping systems and specific operatingconditions shall conform to the requirements of Engineering SpecificationPipingMaterials,PDVSA H221.

2.4 Design Pressures and Temperatures

2.4.1 The design pressures and temperatures to be used as a basis for the design ofpiping systems and the selection of standard piping material components shall be
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in accordance with the requirements of the ASME Code B31.3, with the maximum

operating conditions shown on the applicable P&I diagrams.2.4.2 Piping shall be designed for the maximum expected severe coincidental of

conditions of pressure and temperature during normal operation, arrived on thebasis of the following considerations:

a. Design pressure of the equipment to which it is connected.

b. Set pressure of the safety valve which protects the system.

c. Discharge piping of a centrifugal pump not protected by a safety valve shallbe designed for the higher value of:

1. Maximum suction pressure plus normal differential pressure.

2. Normal suction pressure plus maximum differential pressure.

d. All systems operating below atmospheric pressure shall be designed for fullvacuum.

e. All piping leaving the battery limits shall be designed for a closed valve at thebattery limits of destination plant or off site installation.

f. The design pressure shall apply from the source to the last valve beforeentering equipment at a lower pressure.

2.5 Corrosion Allowance

Minimum corrosion allowances as listed in Engineering Specification PipingMaterials, PDVSA H221 shall be provided in all process and utility pipingsystems.

3 DESIGN DETAILS

3.1 Line and Connection Sizes

3.1.1 Allowable pipe sizes in inches are: 1/2, 3/4, 1, 1 1/2, 2, 3, 4, 6, 8, 10, 12, 14, 16,18, 20, 24 and larger, in 6inch increments.

3.1.2 In general, the minimum pipe sizes shall be 1/2 inch for utility lines; 1 inch forprocess lines; no size limitations for instrument connections and steam tracinglines; 4 inches for underground sewer lines; and 1 1/2 inches for other than sewerunderground lines.

3.2 Material Specification Changes

3.2.1 When a piping system of one material Line Spec is connected to a piping systemof a higher rated material Line Spec, the connecting piping system shall be
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constructed of the higher rated material Line Spec up to and including the first

valve in the connecting piping system.a. The higher rated material Line Spec shall be used up to and including the

valve on the bypass around equipment or pressure reducing valves.

b. Block valves after the reducing valves shall be of the higher rated materialLine Spec.

3.2.2 Where vessels have higher design ratings than the connecting lines, the valvesat the vessels shall equal the pressure rating of the vessels if the valves arenormally closed during operation.

3.2.3 Drilled holes in orifice flanges shall be upward in gas or vapor lines, and lateral

in liquid lines. Other orientations require Owners representative approval.

3.3 Flanges

3.3.1 The use of flanges in piping shall be limited to connections at flanged equipment,valves and appurtenances as indicated on P&I diagrams.

3.3.2 Flanges shall also be provided in cases such as:

Where frequent dismantling of piping is required.

Where plastic, nonmetallic or internally coated piping systems cannot bewelded or otherwise joined except by flanges.

To provide clearance for dismantling of equipment such as pumps,compressors, reactors, etc.

Where is not permitted to fabricate welding pipe.

Where it is not feasible to weld piping sections of dissimilar materials, e. g.Carbon Steel to Cast Iron, Carbon Steel to FRP, etc.

3.4 Screwed Nipples

3.4.1 All carbon steel and ferritic alloy steel screwed nipples shall be of Schedule 80minimum thickness.

a. Close nipples shall not be used.

3.4.2 Austenitic stainless steel and nonferrous alloy screwed nipples shall beSchedule 40S minimum thickness.

3.5 Valves

3.5.1 Valves shall be provided of the type and number shown on the P&I diagrams.

3.5.2 Double block valve and bleeder installations shall be provided as shown on theP&I diagrams where necessary to avoid product contamination, or a hazardouscondition.


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3.5.3 The type of valve shall be in accordance with Engineering Specification, Piping

Materials,PDVSA H221.3.5.4 Facetoface dimensions of gate, globe, check, ball, and plug valves shall be in

accordance with ASME B16.10.

3.5.5 Block valves shall in general be gate, ball, butterfly or plug valves.

3.5.6 Globe valves in sizes 3 inches and larger shall be used only when throttling isrequired.

3.5.7 Plug or ball valves shall be used (when operating temperature is within acceptablelimits) in lieu of gate valves for services where solids may collect to prevent theseating of the wedge.

3.5.8 Gear operators (manual) shall be supplied for gate and globe valves (which areoperated more than four times a year), ball and plug valves, and firesafe butterflyvalves in the following sizes and larger:

VALVE TYPE AND SIZE (NPD)

ASME Primary Gate or Globe Ball or Plug Firesafe Butterfly (3)ASME Primary

Rating, Class in. mm in. mm in. mm

150 (1) 14 350 8 200 8 200

300 (2) 10 250 8 200 6 150

400 8 200 6 150 4 100

600 8 200 6 150 4 100

900 6 150 4 100

1500 4 100 3 80

2500 3 80 3 80

NOTES

(1) Includes ASME Class 125 and 250 cast iron.

(2) Includes ASME Class 300 ductile iron.

(3) This valve type not generally available above ASME Class 600.

a. The valve is to be used in service conditions which require that it be openedor closed as quickly as possible in the event of equipment malfunction oroperation failure.

b. The valves for which gearing is to be supplied shall be indicated on theapplicable P&I diagrams.

3.5.9 For ASME Class 600 and over, valves shall be provided with pressure equalizingbypass globe valve, as indicated in Appendix II, when the operating differential
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pressure across the closed valve approximately equal the pressure rating of the

valve at the operating temperature.3.5.10 The valves for which bypasses are to be furnished shall be indicated on the

applicable P&I diagrams.

3.5.11 Integral valve bypass shall not be used unless absolutely required due to designlimitations. If used, it shall be globe valves only.

3.5.12 The bypass valve and the related bypass piping shall be of the same piping classas the principal valve.

a. Check valves shall be suitable for installation in horizontal or vertical lines wherea reversal of flow may occur.

3.5.13 Stem positions of all valves shall be indicated on the drawings, preferably notbelow the horizontal.

3.5.14 Pipe lines containing hazardous solutions (i.e. acids, caustic, etc.) shall not havevalve stems below the horizontal.

3.6 End Closures

3.6.1 Only with the approval of Owners representative, welded end closures shall bewelding caps for all process service lines and for all other services with designpressures over 1,02 bar (14,7 psi) (gauge) or in vacumm service.

3.6.2 Flat plate closures may be for piping over 12 inches size and with a design

pressure between 0 bar (gauge) and 1,01 bar (14,7 psi) (gauge) innonflammable services.

3.7 Blinds

3.7.1 Blinds shall be supplied only to the extent required for normal operations and asshown on the P&I diagrams.

3.7.2 Blinds (spacers and spectacles) shall normally be installed on all process lines atbattery limits and where required to facilitate testing, inspections or maintenanceof equipment.

3.8 Bypasses 3.8.1 Bypasses around equipment and control valves shall be supplied only to the

extent required for normal operation and as shown in the P&I diagrams.

4 GENERAL INSTALLATION REQUIREMENTS

4.1 Provisions for Expansion and Flexibility

4.1.1 Provisions for thermal expansion and contraction shall be made in all lines inaccordance with the requirements of the ASME Code B31.3.


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4.1.2 Provisions for expansion shall normally be made with pipe loops. Cold strains

shall be avoided and may be used with the approval of Owner s representativeonly.

4.1.3 All piping systems shall be designed so that the loads and moments applied at theflanges of mechanical equipment shall not exceed the permissible reactions onthe equipment nozzles, as indicated by suppliers and/or standards.

4.2 Supports and Anchors

4.2.1 All piping shall be supported and shall be provided with anchors, sway braces orvibration dampeners to prevent excessive expansion forces on equipment andexcessive vibration.

4.2.2 Piping at valves and mechanical equipment, such as pumps, requiring periodicmaintenance shall be supported so that the valves and equipment can beremoved with a minimum necessity of installing temporary pipe supports.

4.2.3 Piping supports shall be designed as part of the piping system in accordance withthe objective and procedures outlined in PDVSA HG251.

4.3 Joints and Connections

4.3.1 Joining in all piping systems equal or larger than 2 inches pipe size shall beaccomplished by butt welding.

4.3.2 Joining in piping 11/2 inches diameter and under shall be accomplished bysocket welding preferably. Screwed connections shall require Ownersrepresentative approval.

4.3.3 Unless otherwise indicated on project specifications, flanged connections shall beused to connect all piping, vessels, equipment, instruments, relief and safetyvalves, etc. (see subtitle 3.3.).

4.3.4 Steel flanges used for the attachment to flat faced cast iron flanges shall be flatfaced.

4.4 Branch Connections

4.4.1 Welded pipe to pipe connections shall be designed so that the angle ofintersection between the branch and the run shall not be less than 45.

4.4.2 Integrally reinforced branch welding fittings which abut the outside surface of therun wall, in sizes 4 in. NPS (100 mm) and larger, are not permitted under any ofthe following conditions:

a. The d/D ratio (branch diameter/header diameter) exceeds 0.8.
http://www.intevep.pdv.com/santphttp://www.intevep.pdv.com/santphttp://www.intevep.pdv.com/santphttp://www.intevep.pdv.com/santp/mid/indice_mid.htmhttp://www.intevep.pdv.com/santp/mid/vol13-2/indice_vol13-2.htmhttp://hg-251.pdf/http://hg-251.pdf/http://hg-251.pdf/http://hg-251.pdf/http://hg-251.pdf/http://hg-251.pdf/http://hg-251.pdf/http://www.intevep.pdv.com/santp/mid/vol13-2/indice_vol13-2.htmhttp://www.intevep.pdv.com/santp/mid/indice_mid.htmhttp://www.intevep.pdv.com/santp


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b. The run piping wall thickness is less than schedule 40.

c. The run piping wall thickness is less than 0.75 in. (19 mm) where outsidediameter exceeds 36 inches (900 mm).

4.4.3 Pad reinforced branch connections are not permitted when the piping designtemperature is 427C (800 F) or greater.

4.4.4 If padtype reinforcement is used for full size branch connections, it shall be of thecompleteencirclement type.

4.4.5 Fabricated branch connections. Branch connections shall be directly joined to theheader with full penetration weld. All branch connections to headers 16 in.(400mm) diameter and larger shall be visually inspected, both internally and externally.

Reinforcing pads (when required) shall be added as a subsequent fabrication stepafter visual inspection. Vent shall be 1/8 in. (3.2 mm) drilled hole.

4.4.6 Connections 11/2 inches NPS (40 mm) or smaller shall be welded to run pipingby using a coupling, or a schedule 160 or greater nipple, or an integrally reinforcedbranch welding fitting. 2 inches NPS and smaller branch connections shall beprovided with a block valve close to the header.

4.5 Valve Installations

4.5.1 Frequently operated valves and unfrequently operated valves required foremergency operations, on which the centerline of the stem is more than 2,3 mabove the pavement or platform levels, shall be provided with remote operatingdevices, like an impact type chain wheel. Clamp type chain wheel is permitted forgear operated valves only. Extended stems or fixed ladders, stairs or platformsare also permitted for easing operation provided do not obstruct walkways andpassageways.

a. Chain wheels shall not be used on screwed valves.

b. Chains shall hang to within 915 mm of the operation level and they shall beattached to columns or walls so as not to obstruct passageways.

4.5.2 Other unfrequently used valves which are more than 2,3 m above the pavement

or platform level shall be installed so they the can be reached from a portableladder or mobile platform.

4.5.3 Frequently operated valves in trenches shall be provided with extension stemsextending to within 100 mm (4 inches) below the cover plate if the hand wheelsare more than 305 mm (12 inches) below the cover plate.

4.5.4 Valves at towers shall be located directly against or close to the tower nozzlesunless physical interference would prevent proper operation of the valves. Valvesshall not be located inside vessel skirts.


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4.5.5 All valve outlet ends in process and steam services which do not connect to a

piping system shall be provided with an appropriate end closure.a. Threaded ends shall use a plug.

b. Socket weld ends shall use a nipple and a screwed cap.

c. Flanged ends shall use a blind flange.

4.5.6 Gate or globe valves which normally operate open shall be installed so stem is inhorizontal position.

4.5.7 Block valves shall be provided on 11/2 inches or smaller branch connections ata maximum distance of 230 mm (9 inches) from header, in utility services likeinstrument and service air; service, crude and makeup water; steam and

condensate.

4.5.8 Instruments gate or globe valves shall be installed so stem is in horizontal position.

4.6 Centrifugal Pump Piping Installations

4.6.1 Discharge and suction valves shall be arranged per Fig. 1.

4.6.2 Check valve installation in the pump discharge line shall be per Fig. 1and thefollowing:

a. A single check valve shall be installed if there is any possibility of a reverseof flow.

4.6.3 Combined stop/check valves may be used in water service under ASME Class300 rating.

4.6.4 Valve sizing shall be as follows:

a. Check valves and discharge block valves shall be linesize. However, if thedischarge line is two or more sizes larger than the pump discharge nozzle,the valves may be the next standard size smaller.

b. Suction valves shall be linesize. However, a size reduction to one sizelarger than the nominal size of the pump suction nozzle may be used if:

1. The result is a lower total installed cost, and.2. The effect on NPSH is tolerable at design and alternate operating

conditions.

4.6.5 Suction valve ratings shall be as follows:

a. With a single pump in the line, the suction valve shall have apressuretemperature rating equal to the suction line rating.

b. When two or more pumps are manifolded, the suction valves and anycomponents between the valves and the pumps shall have a


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pressuretemperature rating of not less than 3/4 the maximum discharge

pressure of the pump at normal operating temperature.4.6.6 Pressure Relief (PR) valve installation for mechanical seal protection. When two

or more pumps are manifolded and the failure pressure of the pump mechanicalseal is less than the pump casing design pressure, a PR valve shall be providebetween the suction valve and the pump. The PR valve shall be set to open nohigher than the seal rated pressure and shall be sized for a flow equivalent to 10%of pump design flow plus the flow through any drilled check valve or bypass line.

4.6.7 Discharge from the PR valve shall be piped to the pump suction source upstreamof the suction valve.

4.6.8 Length of suction line.

For pumps taking suction from drumless condensers, the length of the slopedhorizontalsuction line under the condenser must be minimized to avoid localvapor lock caused by velocity loss.

4.6.9 Minimum sloping of suction line.

If vapors may be present in the suction line, it shall be sloped not less than 1:50downward, from the vessel toward the pump.

If it is impracticable to slope the line due to layout considerations, alternate pipingarrangements, to avoid high point vapor traps, shall be approved by the Owner srepresentative.

4.6.10 Reducers in horizontal suction shall be eccentric and shall be installed as shownin Fig. 1, to avoid pocketing of vapors in the horizontal line.

4.6.11 Strainer installation:

a. Temporary strainer shall be installed per Fig. 1unless permanent strainershave been specified.

b. Piping layout shall permit insertion and removal of the temporary strainerwithout disturbing equipment alignment. Pipe fittings such as Tees, Ys,or fabricated piping spool pieces are acceptable for this purpose.

c.The design and location of permanent strainer shall permit cleaning withoutremoving the strainer body.

4.6.12 Suction liner for double suction pumps shall not be installed with a horizontalelbow closer than 5 pipe diameters of straight run pipe to the pump suction nozzle.

WARMUP FACILITIES

4.6.13 Piping shall be installed per Fig. 1, details A or B as applicable, to provide acontinuous flow of fluid through the pump and piping when a pump is idle oroutofservice, for either of the following conditions:


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a. If the pumping temperature exceeds 230 C (450 F).

b. If the ambient temperature may be at, or below, the pour point of the processfluid.

4.6.14 Warmup facilities for other than coking and slurry service shall be installed perFig. 1Detail A and the following:

a. The drilled check valve shall have the hole sized to provide a flow of 3 to 5%of normal pump flow, but the hole shall not be less than 6,3 mm (1/4 in)diameter.

b. If a high differential pressure precludes meeting the 3 to 5% flow limitationper subparagraph a. above, or as an alternative to a drilled check valve, a

bypass with a flow restrictor is acceptable on pumps with discharge nozzles2 in. NPS (50 mm) diameter and larger.

4.6.15 A drilled check valve or bypass piping per Fig. 1Detail A shall be installed whenthe pump is designed for automatic startup and when the daily mean temperaturemay fall below the temperature for acceptable operating viscosity.

LOW FLOW PROTECTION

4.6.16 A low flow protection system shall be installed for pumps expected to operate forextended periods of time at less than 20% of their best efficiency point (BEP) flowrating. The low flow protection system shall be designed to assure continuous

pump operation at flows exceeding 20% of BEP flow rating.The low flow protection system shall either be piped back to the pump suctionsource; or through a cooler and back to the pump suction. Alternative systemdesign shall be submitted to the Owners Engineer for approval.

Boiler feed water pumps. An automatic, combined lowflowbypass/check valveshall be provided for each pump (in lieu of an unvalved orificed bypass).

4.6.17 External Forces and Moments

Forces and moments caused by piping on pump nozzles or couplings shall becalculated by Piping Engineer. Considerations shall be taken for specialconditions like not operation periods, thermal expansions, types of baseplate andsteamout. Reactions and moments shall not exceed permissible values asindicated in applicable pump codes or standards, or pump manufacturer.

Deviations permitting higher loads require approval of the Owner srepresentative. Such approval will be based on proof submitted by the pumpvendor or manufacturer that the specified pump nozzle or coupling deflection willnot be exceeded.

For inline pumps, piping forces shall be determined with the pump considered asa rigid, but unanchored segment of the piping system.


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DEC. 981

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4.7 Vents and Drains

4.7.1 Vents and drains shall be provided in accordance with P&I diagrams.

4.7.2 In general, venting and draining shall be accomplished through vessel and/orequipment connections.

a. Vessel vents and drains may be located in overhead or bottom piping,provided no valves or blinds are located between the vent or drainconnections and the vessels.

4.7.3 Plugged vents (valves omitted) shall be provided on high points of pipe sectionsand on high points of 6and larger inverted Ushaped pipe sections when thesections are to be hydrostatically tested.

a. High point vents shall not be required when one or more of the followingconditions exists:

Inverted Ushaped piping to be hydrostatically tested is 4and smaller.

Piping system is pneumatically tested.

Piping system receives only service tests(i.e. cooling water supply and returnsystems, plant and instrument air, lube and seal oil systems, steam tracing, andpotable water systems).

Piping system is hydrostatically tested at atmospheric pressure (i.e. storagetanks, mixing tanks, and associated piping).

An accessible flanged joint exists at the highest point in the system to be tested.

4.7.4 Valved drains shall also be provided on low points of all pipelines

4.7.5 Drains emptying into open receptacles shall terminate 50 mm above the top of thedrain receptable and the discharge shall be visible from the location of the drainvalve.

4.7.6 Unless otherwise noted on piping drawings or P&I diagrams, the minimum sizeof vent and drain connections shall be 3/4 inch. For hydrostatic tests, 3/4 inch and11/2 inches drains shall be provided for 10 inches lines NPS and smaller, and12 inch lines NPS and greater, respectively.

4.7.7 The minimum vent and drain connection sizes for vessels shall be in a accordancewith Appendix III.

4.7.8 No permanent drains or vents shall be provided in hydrogen carrying lines. Anyvents or drains installed for hydrostatic testing shall have valves removed andconnections plugged and weld sealed after testing.

4.7.9 A 3/4 inch drain shall be installed upstream of each control valve, between blockvalve and control valve.


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4.7.10 When a piping spool is between a check and a block valves, the spool shall be

provided with a valved drain.

5 REQUIREMENTS FOR INDIVIDUAL PIPING SYSTEMS

5.1 Requirements for Process Piping Systems

5.1.1 Sample connections and sample coolers shall be supplied to the extent shown onthe P&I diagrams. Avoid long dead legs.

5.1.2 All sample connections shall normally be 3/4 inch.

5.1.3 For pipe in a horizontal or inclined plane, the sample connection shall be locatedat the side of the pipe unless otherwise indicated on the P&I diagrams.

5.1.4 Unless otherwise indicated on the P&I diagrams, the piping systems for pumpingout towers and equipment shall be a part of the regular process piping of the unit.

5.1.5 Relief valves which discharge to atmosphere through discharge piping shall havethe pipe extend at least 3 meters (10 ft) above any platform or working area withina 7,6 meter (21,5 ft) radius of the point of discharge.

5.1.6 Relief valves shall be connected to flare or other disposal system only when soindicated on the applicable P&I diagrams.

5.1.7 Relief valves have a minimum of piping between the protected line or equipment

and the valve inlet and shall be accessible.5.1.8 The low point of the relief valve outlet piping when discharging to the atmosphere

shall be provided with a 6 mm minimum weephole.

5.1.9 Relief headers shall be continuously sloped to knockout drums. Slope shall beindicated on P&I diagrams.

5.2 Requirements for Steam Systems

5.2.1 Steam piping systems shall be supplied to the extend shown on the utility flowdiagrams and normally shall include systems for the distribution of steam required

for process operations, steam turbines, service steam, steam tracing, andequipment steamout.

5.2.2 All branch connections from steam headers shall be taken off the top of theheader.

5.2.3 Single block valves shall be provided in branches, adjacent to the headers, to theextent shown in the steam P&I diagrams.

5.2.4 Single block and check valves shall be provided adjacent to the point of injectionof steam into any process stream


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5.2.5 Single block valves shall be supplied adjacent to the header in the inlet line to each

steam turbine and adjacent to the discharge header in the outlet line unless thedischarge is to atmosphere of surface condenser.

5.2.6 Steam relief valves shall discharge to atmosphere through discharge pipingextending at least 3 meters (10 ft) above any platform or working area within 7,6m (21,5 ft) radius of the point of discharge.

5.2.7 The low point of the relief valve outlet piping shall be provided with a 6 mm (1/4in) minimum weephole when discharging to the atmosphere.

5.2.8 All steam lines shall be designed to avoid unnecessary traps.

5.2.9 Where traps cannot be avoided, steam traps with drains shall be designed into the

piping to remove condensate.

5.2.10 Traps which discharge to a high pressure condensate system generally beprovided with a bypass with glove valve and two block valves.

5.2.11 Traps which discharge to a low pressure condensate or discharge to the open airwill have no bypass.

5.2.12 Before each steam trap inlet, a free blow type drain valve shall be installed indirection of flow.

5.2.13 Traps inside battery units shall generally discharge to a condensate return systemor sewer.

5.2.14 Traps outside battery limits shall discharge to a suitable location, such as a ditch,flash pots or as defined on the P&I diagrams.

5.2.15 Steam traps discharging into a overhead condensate system or closed systemshall be provided with a check valve unless the steam trap acts as a nonreturnvalve.

5.2.16 Steam traps shall be protected by a Ytype strainer installed before the trap ora builtin strainer, independently of selfcontained strainer trap.

5.2.17 A steam trap shall be accessible for removing or maintenance.

5.2.18 Steam tracing shall be provided in accordance with Engineering SpecificationSteam Tracing Piping Requirements,PDVSA HD201.

5.3 Requirements for Water and Air Systems

5.3.1 All process cooling water line shall be installed so that the equipment being cooledwill remain full of water in the event of shutdown of the cooling water pumps.

5.3.2 Shutoff valves in supply branches shall be located as close to the main header lineas possible.


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5.3.3 And instrument air piping system and a plant air system shall be provided as

shown on the P&I diagrams.5.3.4 Air supply lines shall be provided with drip legs and blowdown connections.

5.4 Utility Outlets

5.4.1 Valved utility service outlets for steam, water and air (service stations, flush,steamout, etc.) shall be provided where shown on utility flow diagrams anddrawings.

5.4.2 Areas to be served by the utility flow outlets shall be within reach of hose 15 meterslong.

5.4.3 The utility outlet connections shall be grouped together as much as possible in thesame sequence namely, air, steam, water, nitrogen. The size shall be 1 inch.

5.5 Drainage and Sewage Systems

5.5.1 Separate drainage and sewage systems shall be designed in accordance withEngineering Specification Underground Piping for Drainage Systems DesignRequirements,PDVSA HE251.

5.6 Firewater Protection System

5.6.1 All firewater protection systems shall be designed in accordance with PDVSAManual de Ingeniera de Riesgos.


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Pgina 18


APENDIX I

MINIMUM OVERHEAD CLEARANCES

ITEM MINIMUM CLEARAN-CES*

ROADS, ACCESSWAY AND CRANEWAYS:

HEADROOM FOR PRIMARY ACCESS ROAD (WHEREMAJOR MAINTENANCE VEHICLES ARE EXPECTEDTO PASS)

6400 mm (210)

PUMP MAINTENANCE ACCESSWAY HEADROOM 3650mm (120)

PROCESS AREA CRANEWAY HEADROOM 5335 mm (176)

PUMP MAINTENANCE ACCESSWAY HORIZONTALCLEARANCE, NOT NECESSARILY IN A STRAIGHTLINE

3050 mm (100)

CLEARANCE FROM EDGE OF ROAD TOPLATFORMS, EQUIPMENT, PIPE, ETC.

1525 mm (50)

NORMAL OVERHEAD, INSIDE BATTERY LIMIT 4880 mm (160)

PLANT ROADS, OUTSIDE BATTERY LIMIT,CLEARANCE

6100 mm (200)

RAILROADS:

HEADROOM FROM TOP OF RAIL 6550 mm (216)

CLEARANCE FROM TRACK CENTERLINE TOOBSTRUCTION (ANY)

2590 mm (86)

MAINTENANCE PASSAGEWAYS AND WALKWAYS:

HORIZONTAL CLEARANCE, NOT NECESSARILY IN ASTRAIGHT LINE

915 mm (30)

HEADROOM (EXCEPT FOR HANDWHEELS, WHICHMAY BE 66(1980 mm)

2290mm (76)

CLEARANCE UNDER PIPEWAY:

ACCESS FOR VEHICULAR EQUIPMENT 3650 mm (120) ACCESS FOR PORTABLE SERVICE EQUIPMENT 3050 mm (100)

PIPE ON SLEEPERS:

CLEARANCE, BOTTOM OF PIPE TO FINISHEDGRADE, UNLESS OTHERWISE SPECIFIED INPROJECT SPECIFICATIONS

305 mm (10)


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ITEM MINIMUM CLEARAN-

CES*

EQUIPMENT:

MINIMUM MAINTENANCE SPACE REQUIREDBETWEEN SHELLS OF EXCHANGERS OR OTHEREQUIPMENT ARRANGED IN PAIRS

915 mm ( 30)

MINIMUM MAINTENANCE SPACE REQUIRED TOSTRUCTURAL MEMBER OR PIPE

305 mm (10)

FIRED EQUIPMENT:

CLEARANCE FROM EDGE OF ROADS TO SHELL

3050 mm (100)

PIPE (ABOVE GROUND):

CLEARANCE BETWEEN OUTSIDE DIAMETER OF

FLANGE AND OUTSIDE DIAMETER OF PIPE OR

INSULATION

CLEARANCE BETWEEN OUTSIDE DIAMETER OF

PIPE OR INSULATION AND STRUCTURAL MEMBER

CLEARANCE IS DEFINED AS THE CLEAR SPACE

BETWEEN EXTREME PROJECTIONS.

25 mm

25 mm

(01)

(01)


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APPENDIX II

BYPASS VALVES GLOBE

(Pipe Size In Inches)

GATE VALVE RATING AND BYPASS GLOBE VALVE SIZE

SIZE 150 300 400 600 900 CLASS

CLASS CLASS CLASS CLASS and Over

NONE NA

4 3/4

6 3/4 3/4

8 3/4 3/4

10 1 1

12 1 1 1

14 to 20 1 1 1

24 1 1 1


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Fig 1. TYPICAL SCHEMATIC PIPING AND VALVES ARRANGEMET

WARMUP

(Note 3)Top orSideTakeoff

min.distance

BYPASS

FLOWRESTRICTOR(Note 4)

DischargeSuction

(Note 2)RESTRICTORFLOW

distancemin.

WARMUP

(Note 2)RESTRICTOR

distancemin.

FLOW

Suction

1NPS

distancemin.

Discharge

DRILLED

VALVECHECK

BYPASSAlternativeto DRILLEDCHECK VALVE

PI

SeeDetail A

and

Detail Bfor wzrmup

facilities

Pump

Flanges

Lateral

Alternate Location of Incraser

Discharge Valve

Low Point Drain (Note 1)

Increaser, if required

Vent, Drain or Gage Connection

Casing Vent, if especified

AlternateDischarge Piping

(Horizontal)Alternate

(Horizontal)Discharge Piping

DrainReducer shall beeccentric andinstalled as shown

Alternate Locationfor Reducer

Casing Drain, if specifiedPump Flange

Parallel Pump)Lateral (FromLateral (To

Parallel Pump)

Lateral

Alternate Location of Reducer

Suction ValveSpool of Reducer

Strainer (Note 2)

Vent, Drain, or Gage Connection

PR Valve (Note 3)

Strainer (Note 2)

(Vertical)Suction Piping Discharge Piping(Vertical)

Notes:

(1) A low point drain is not required if the check valve is drilled and a casing drain is provided.(2) Temporary or Permanent Strainer. Alternative location for Permanent Strainer, as required, will be specified.(3) PR Valve location, if required for pump casing or mechanical seal protection.

Notes:DETAILS A & B: (1) Line flexibility shall be provided for thermal expansion between pump lines and warmup and bypass lines.

(2) Flow Restrictors sized to provided a flow of 3 to 5% of normal pump flow, but not less than 1/4 in. diam.

(2) Flow Restrictors sized to provide a flow as specified.

DETAIL B only: (1) Lines sized for a max, velocity of 6 ft/sec., but not less than 1 in. NPS

in.mm 15

1/2 NPS 3/4 NPS20

1 NPS25

1/4 diam.6.3 1:8 m/s

6 ft/sec11.98 kg/m0.1 lb/gal

3

Acceptable Metric Equivalents

Documents

MID-H-251-Process and Utility Piping Design Requirements