Section 5 — Piping

IPE-EP-5-5-1

IPE Engineering Practice IPE-EP-5-5-1

Document number: IPE-EP-5-5-1 · Section: 5 — Piping

CoInafsletcatilo nA Prouinbta E nEgningeeirninege Prriancgtic Pesractices Piping Fabrication 7.1.4 The tolerances on linear dimensions of spool pieces composed of piping components with intervening pipe shall not exceed: 1/8 inch for NPS 10 and smaller, 3/16 inch for NPS 12 through NPS 24, and 1/4 inch for greater than NPS 24. Tolerances shall not be cumulative. 7.1.5 (*)For spool pieces composed entirely of piping components with no intervening pipe, the sum of the tolerances on linear dimensions for the components could exceed the requirement of above. In such cases, the following procedure shall be used to meet the tolerances on linear dimensions: 1) The fabricator shall first make every reasonable effort to meet the requirement of the previous paragraph using piping components from their stock. 2) (*)If piping components cannot be found in–stock such that the requirement of the previous paragraph is met, the fabricator shall adjust the linear dimensions of adjacent spool pieces such that the assembly will meet the requirements of the previous paragraph. In cases where adjustments are made to the linear dimensions of adjacent spool pieces in accordance with this paragraph, spool drawings shall list these adjustments in the notes. 3) (*)In cases where the procedures in the two previous paragraphs cannot be used to meet the requirement of the previous paragraph and a tight tolerance must be maintained, piping components may be machined. Such cases require review and approval by the Owner’s Engineer. However, in no case shall flange faces be machined in order to meet tolerance on linear dimensions. 7.2 Heating of pipe to satisfy the dimensional tolerances specified above shall conform to the following requirements: 1. Only carbon and low alloy steels (P–1, P–4, and P–5) materials may be heated to facilitate fabrication. 4) Pipe that has not been postweld heat treated may be heated for minor corrections in fit. Under no circumstances, however, may pipe materials be quenched to correct alignment. 5) (*)Unless otherwise specified by the Owner’s Engineer, the maximum temperature used to correct alignment is 1200°F. 6) (*)Pipe that has been postweld heat treated shall not be heated to correct misalignment without approval of the Owner’s Engineer. If approval is given, heating shall be done with electric resistance heaters. After any heating to correct misalignment, hardness shall not exceed 225 HB in any part of the heated area. Heating shall be done over a 24 inch length, minimum. Heaters shall be fully insulated. Insulation shall extend a minimum distance of 24 inches on either side of the heaters. Insulation shall not be removed until all of the pipe has cooled to below 600°F. 7.3 The ends of piping components to be joined shall be aligned as accurately as is practicable within existing commercial tolerances on diameter, wall thickness, and out–of–roundness. Where the internal misalignment between piping components exceeds 1/16 inch, the component with the wall extending internally shall be trimmed in accordance with the Applicable ASME Piping Code. This misalignment tolerance is not permitted in piping to and from reciprocating compressors (through the second change in direction) or in piping with Severe Cyclic Conditions as defined in ASME B31.3. For such services, the inside diameter of the pipe should be machined or ground to a close tolerance and the root pass should be welded by the tungsten inert gas process. 7.4 The maximum allowable gap between reinforcing pads and the curvature of the pipe shall not exceed 1/8 inch.

CoInafsletcatilo nA Prouinbta E nEgningeeirninege Prriancgtic Pesractices Piping Fabrication 9.4.4 Rotary Draw Cold Bending is performed on a bending machine which utilizes a forming die, ball or plug mandrel (when required), pressure die and wiper die. The bending of material takes place at ambient temperature. The following requirements for Rotary Draw Cold Bending shall be followed: 9.4.4.1 The wall thickness shall be tested prior to shipment by the pipe supplier to assure the estimated thickness after bending will not be less than the minimum required wall thickness calculated for pressure and temperature. 9.4.4.2 (*)Upon completion of the ending and trimming, the substantial removal of the lubricant shall be achieved through the use of steam or hot water. Other methods shall be approved by Owner’s Engineer. 9.4.4.3 The following tolerances on linear dimensions shall be met. Dimensions taken from the center of bends to the ends: 1. Specified Tangent Lengths: • ± 1/8 inch for specified tangent lengths up to 5 feet • ± 1/4 inch for specified tangent lengths more than 5 feet 2. Centerline Radius: • ± 1/2 inch for centerline radius up to 24 inches • ± 1 inch for centerline radius more than 24 inches 3. Degree of Bend Tolerance: • ± 1 degree 4. Center to Center Tolerance for 180 degree bends: • ± 1/4 inch 5. Roundness of end: • ± 1% when tangent length is at least 1-1/2 D • ± 2% when tangent length is less than 1-1/2 D 6. Center–to–Center Dimension on Offset Bends: • ± 1/4 inch for 1 inch OD to 6-5/8 inch OD pipe or tubing • ± 1/2 inch for pipe or tubing greater than 6-5/8 inch OD 9.4.5 Pipe bends with the following defects will be rejected: 1. The pipe wall thickness at the thinnest point after bending, less corrosion allowance, shall not be less than the calculated thickness required for pressure and temperature. 2. Wrinkles and bulges after bending and heat treatment. 3. Cracks and/or laminations. 4. Dimples or craters ≥ corrosion allowance. 9.4.6 Bends of ferritic materials shall have a radius measured to the centerline of the pipe of at least five times the nominal pipe diameter. Bends in NPS 14 and larger standard wall and lighter pipe shall have a radius of at least six times the nominal pipe diameter.

CoInafsletcatilo nA Prouinbta E nEgningeeirninege Prriancgtic Pesractices Piping Fabrication 10.4 Reinforcement for pipe–to–pipe branch connections shall be designed in accordance with the Applicable ASME Piping Code. All reinforcement pads for pressure openings, or each segment of built–up type reinforcement pads for pressure openings, shall be provided with one NPT 1/4 inch hole for testing and venting. Reinforcing pads for structural attachments and trunnions shall be provided with one NPT 1/4 inch hole in each segment for venting. The vent shall not be at apex of curvature. Each reinforcing pad or each segment thereof shall be tested at 15 psig with dry air and a soap solution before hydrotest. 10.5 Fabricated branch connections other than welding tees or those shown in Figure 3 shall not be used for Severe Cyclic Conditions as defined in ASME B31.3 or in vibratory service (e.g. reciprocating compressor or pump). 10.6 Fabrication details for couplings shall be in accordance with Figure 4. 10.7 Fabrication details for branch welded–on fittings (weldolets) shall be in accordance with Figure 5. 10.8 Full–sized or reduced branches at angles other than 90 degrees shall not be employed except when required because of flow and pressure drop considerations (for example, in flare lines). The angle between the branch and the run of the header shall not be less than 45 degrees. It is preferred that the centerline of the branch intersect the centerline of the header. Exception: where flow conditions control and the Owner’s Engineer has given prior approval, the branch may intersect the header in a tangential or semitangential direction, provided the angle between the branch and the run of the header is not less than 60 degrees and the intersecting surfaces form a welding angle of not less than 45 degrees. 10.9 (*)Ribs and gussets shall not be used for pressure strengthening of branch connections without prior approval of the Owner’s Engineer. Use of ribs, gussets, clamps, and plates to provide strength for external and thermal loads may be considered with prior approval of the Owner’s Engineer. 10.10 Socket–welded branch connections shall not be used in service where crevice corrosion or erosion is likely to occur. 10.11 (*)Branch connections in “Pulsation Bottles” for reciprocating compressors shall be made by the use of welded–in contour inserts, extruded welding tees, or other methods that produce connections that have equal (or better) capability to withstand vibration and pulsation. All designs must be approved by Owner’s Engineer. Bottles with multiple nozzles which connect to compressor cylinders shall be shipped with only one of these nozzles welded in. The other nozzle(s) shall be shipped loose for field fit–up between the compressor and the bottle. 10.12 Where a line with a lower rating connects to pipe or equipment with a higher rating, the line shall have the higher pressure rating: up to and including the first block valve, control valve or check valve, or up to and including the second valve and the bleed valve when double block valves are used, and up to and including the block valve and check valve when both a block valve and check valve are used. For alloy lines, the alloy material may terminate with the first block valve, which shall be alloy. 10.13 All small piping connections less than or equal to NPS 1–1/2 shall be fabricated using a minimum length of pipe between the takeoff point and valve, and without the use of elbows between the valve and takeoff point.

CoInafsletcatilo nA Prouinbta E nEgningeeirninege Prriancgtic Pesractices Piping Fabrication 15.5 The clear distance between centerlines of adjacent girth butt welds shall not be less than six times the pipe wall thickness, or 3 inch, whichever is greater. 15.6 The clear distance between attachment welds for adjacent branch connection fittings shall be based on the criteria stipulated in PFl Standard ES–7. 15.7 Longitudinal seams in adjoining lengths of welded pipe shall be staggered and shall be so located as to clear openings and external attachments. Clearance and stagger shall not be less than ten times the nominal pipe wall thickness. Longitudinal seam welds shall be located in the top quadrant of the pipe when practicable. 15.8 When a field transition butt weld between carbon steel pipe and alloy or non–ferrous alloy pipe is required, a 12 inch long section of carbon steel pipe of the required diameter and wall thickness shall be shop welded to the alloy steel or non–ferrous pipe so that a similar material weld can be made in the field. 15.9 When field welds are added in lines which pass through building walls and roofs, column lines of structures, foundations, platforms, or grade elevation, the welds shall be located at least 12 inches outside of or above such structural items when practical. 15.10 Tack welding butt joints for completion at a later date shall be in accordance with EP 5–5–2. 15.11 All piping sections to be lined with castable refractory, shall either be match marked and provided with truing rings per section 8.0 prior to the installation of lining, or the lining shall terminate 8 inches from the pipe end to facilitate field fitup and welding. Hammering or deforming fully lined pipe (i.e., lined to the end of the pipe) to effect joint fitup with other pipe is not acceptable. 15.12 Sizes of fillet welds for attaching socket–welding components and slip–on flanges shall be not less than shown in the Applicable ASME B31 Piping Code, except that: 1. The weld shall be at least a two–pass weld. 2. The external fillet weld attaching the hub of the slip–on flange to the pipe shall have a weld leg dimension the larger of the nominal thickness of the pipe or 1/4 inch. 3. The internal fillet weld attaching the slip–on flange to the pipe shall have a weld leg dimension equal to the nominal thickness of the pipe. 15.13 Internal welds of piping which is to be internally coated (with “Scotch–Kote” or similar material) shall be ground smooth and flush with the ID of the pipe. If this cannot be done, GTAW root pass welding using an argon gas back purge shall be used, and the root pass shall be as flat or smooth as possible. 15.14 Excessive weld projections, as determined using the Applicable ASME Piping Code, on accessible joints shall be removed by grinding. Welds having excessive projections on inaccessible joints shall be cut and rewelded. 15.15 Field welded piping “tie–ins” for low alloy steels (P–4, P–5A, P–5B, P–5C), stainless steels (P–7, P–8), and all compressor piping shall have the root pass welded with GTAW with the backside of the weld purged with argon gas. 15.16 Seal welding requirements are covered in EP 5–5–3.

CoInafsletcatilo nA Prouinbta E nEgningeeirninege Prriancgtic Pesractices Piping Fabrication 2. All welds made to branch contour inserts (sweep–o–lets). 3. All circumferential, longitudinal, and helical (spiral) groove welds in piping subject to Pneumatic Leak Test per ASME B31.3 paragraph 345.5 or a Hydrostatic–Pneumatic Leak Test per ASME B31.3 paragraph 345.6, see EP 5–5–3 for leak testing requirements. 4. All circumferential, longitudinal, and helical (spiral) groove welds in piping subject to an Alternative Leak Test per ASME B31.3, paragraph 345.9, see EP 5–5–3 for leak testing requirements. 18.2.5 When the minimum percentage of welds subject to radiographic examination is less that 100% per Table 5, the welds to be examined by random radiography shall be identified by the piping fabrication inspector. The piping fabrication inspector is defined in the ASME Piping Code (for example, see paragraph 340.4 in ASME B31.3). The method of selection shall be based on the following: 1. All personnel involved in the fabrication and welding of piping shall have no prior knowledge that a weld is to be radiographed until after completion of the weld. 2. Each welder’s output shall be nominally examined to the frequency stipulated in Table 5. The welds selected for radiographic examination shall be evenly distributed taking into account the different weld procedures and pipe sizes of welds made by each welder. 3. At least one weld for each weld procedure specification (WPS) made by each welder shall be radiographed. 4. Welds that are examined to the 100% radiography requirements of Table 5 shall not be included in the weld count used to establish the required random radiography percentages in this table. 18.2.6 In addition to the requirements in Table 5, for weld categories that require less than 100% radiographic examination, fabricated piping with a diameter greater than or equal to NPS 24 shall be examined by spot radiography in accordance with the following criteria: 1. All circumferential (girth) weld seams in pipe NPS 24 and larger shall be examined in one location. 2. All circumferential weld seams in pipe larger than NPS 36 shall be examined in two locations. 3. (*)The location of the spot radiograph shall be randomly selected or designated to a specific location by the Inspector. 4. The film length for each spot radiograph shall be 10 inches. 5. The Acceptance Criteria for spot radiographs shall be per Table 5. 6. (*)Ultrasonic examination may be substituted for spot radiography when approved by the Refinery Inspection Authority. the required examination area shall encompass a minimum of 10 inches of the weld seam. 18.2.7 The sequence of radiographic examination for final acceptance of piping welds which require post weld heat treatment (PWHT) shall be in accordance with the following: 1. For piping systems constructed of carbon steel that have a wall thickness that is less than or equal to 0.75 inches, radiographic examination may be performed before or after the final PWHT. 2. For piping systems constructed of carbon steel with a wall thickness that exceeds 0.75 inches and all other alloy materials which require PWHT, radiographic examination shall be performed after the final PWHT.

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