Procedure For Installation Of Buried Carbon Steel Piping

This article is about PROCEDURE FOR INSTALLATION OF BURIED CARBON STEEL PIPING and focusing to the engineers, technicians and supervisors. You will find lot of documents related to this article. Just navigate our website ww.paktechpoint.com  and find more articles. Please! Do not forget to subscribe our You tube channel also. Thanks in Advance.

Installation Procedure Of Buried Carbon Steel Piping

MATERIAL SELECTION

Piping Materials allowed for UG Metallic pressure piping per ASME B31.3 is one of the approved line classes shown below with various materials for services shown:

1)  12LC0U is Cement-lined steel pipe and fittings (may be used for non-acidic water and oily water service) in 4-inch NPS or larger  below ground,  where plastic pipe is not permitted.

2)     12LE0U is Fusion Bonded Epoxy-lined carbon steel piping to be used as alternative to cement-lined piping in 2-inch NPS or larger.

3)     12BD0U is 90/10 Copper Nickel pipe and fittings is used in pipe sizes up to 4-inch NPS for corrosive waters.

Receiving

Receiving is defined as taking delivery of piping material with relevant voucher as per bill of material. QA/QC Engineer shall segregate and tag materials rejected during inspection with “rejected” mark prior to repairing or returning to warehouse, so that they can be identified easily.

Material Verification

Before shop fabrication and installation, the piping materials shall be checked as following:

1)      Transit damage

2)      Dust on pipe, conditions of fitting and flange

3)      Corrosion presence

4)      Material Storage

5)      Material Identification: The specification and grade of the piping material shall be checked against the material list on the isometric drawing and/or on the available material voucher.

Material Identification Marking

1)              Each piping spool shall be plainly marked with a spool number using paint.

2)             All piping spool shall be marked by proper method, which does not result in harmful contamination and sharp discontinuities, and which will identify the material until it is installed.

Traceability of Material Identification

1)             Identification marks or color coding on piping material shall be maintained until piping is fabricated and installed. However the basic material for carbon steel pipes and fitting such as API 5L Gr.B,A105 and A234
WPB may not be marked or color coded after painting.

2)             If identification marks are obliterated, Contractor shall rewrite these identification marks.

Welding joint Identification

The identification marks for welding joint shall be located 50-70 mm away from the weld seam and all welding joints shall be written by each welder.

Spool Identification

The size of identification lettering shall be sufficiently large so that finding is easily achieved. The minimum size of identification lettering shall be at least 10mm.

FABRICATION

1         Cutting

1.1        Contractor will use gas cutting machine for non-galvanized carbon steel materials. The cutting flame shall be so adjusted and manipulated as to avoid cutting beyond the prescribed lines. The thermal cutting ends shall be ground to bright metal to ensure complete removal of surface contamination. The roughness of gas cut surfaces and occasional notches on edges shall be removed by machining or grinding. Cut surfaces and edges shall be left free of slag.

1.2        Cutting shall be performed perpendicularly to the piping component centerline unless otherwise indicated on the drawing. Cutting shall be made with suitable allowance taken into account for shape of connection and shrinkage due to cutting and welding. Contours of all weld preparation shall be smooth without any rough edges.

1.3        Before cutting, suitable material trace-ability and mark-up of cutting limits shall be done on each part of materials to be cut. Special care shall be taken to remove internal burrs resulting from cutting, specially on pipes equal to or less than 2 inch in diameter. Cut surface shall be free from defects and laminations.

2         Threading

2.1        Screwed connection shall only be used where permitted in the relevant piping materials class.

2.2        Screwed threads shall be clean cut with no burrs, no stripping. Ends shall be reamed to remove burrs. Threaded parts shall be fitted by progressive and tight screwing.

                     1)             By inserting a Appropriate PTEE tape for design temperature up to 1400 C (Except where seal-welding is
required).

                     2)             Without inserting any foreign material above this temperature, unless suitable sealant product has been specially selected.

2.3        Excessive wrench marking on pipes or fitting shall be cause for rejection.

2.4        Seal welds are not applied on assembly.

3         Alignment, Fit-up and Tack Weld 

3.1        After end preparation, the alignment, fit-up and tack weld activities shall be carried out for the purpose of exact pipe spool fabrication.

3.2        Parts are to be joined by welding may be fitted, aligned and retained in position during the welding operation by using of bars, jacks, clamps or temporary attachments in order to avoid deformation and minimize strains during tack.

3.3        Tack weld used to secure alignment shall be removed completely, when they have served their purpose, or their stopping and starting ends shall be properly prepared by grinding or either suitable means so that they may be satisfactorily incorporated into the field weld.

3.4        Tack welds shall be done by quality welders. When tack welds are not become part of the finished weld, these shall be checked carefully.

3.5        Allowable offset are as follows. Provision of ASME B31.3 para.328. 4.2, 4.3 and fit-up scheme as per SATIP. Concentricity of adjacent parts, and alignment of internal surface shall be 1.5mm (1/6”). Where parts with internal diameters differing by more than 1.5mm are joined concentrically, the inside of the smaller bore shall be tapered to match the large bore within 1.5mm. This tapering shall not result in a wall thickness less than the minimum design thickness plus corrosion allowance.

4         Fabrication Tolerances 

Contractor is responsible for ensuring that fabricated piping conforms to applicable code, Specification, Drawing and purchase order requirements. He is responsible for the fabricated dimensions that agree with piping drawings. Unless otherwise specified, dimensional tolerance shall conform to the acceptance of SATIP criteria.

5         Final Check 

5.1        After completion of spooling fabrication, Contractor field engineer shall check all kinds of spool information (material trace-ability, welding joint mark, welder qualified number, spool number, etc…).

5.2        Finaldimension, orientation, cleanliness and end protection shall be checked.

5.3        All piping and fittings after fabrication shall be cleaned thoroughly with compressed air and/or rotary wire brushes to remove all sand, looser rust and other foreign matter.

5.4        Protection cover such as plastic cap, wood cap etc shall strictly protected the pipe end and flange face.

5.5        Spool Inspection Contractor field engineer and QA/QC engineer shall inspect spool status before transport to spool stockyard area for the following items.

1)             Spool dimension check.

2)             Special identification pertaining line number and spool number, etc.

3)             Color coding and trace-ability check, if need.

4)             NDT and PWHT completion status check.

After spool inspection, the spool controller shall be record the result of inspection on the spool control log and getting
signature from field engineer and QA/QC engineer to release the spool to field.

6         Transportation and Storage

6.1        Fabricated spool shall be transported to the spool storage yard by trailer and cargo truck and they shall be arranged on the basis of each material, area & system at the spool storage yard, which prepared by Contractor before work start.

6.2        When spool are moved to storage yard, spool controller shall record and maintain all the information including present location for each spool. Storage spool location map shall be done.

6.3        Storage yard shall be organized to maintain and handle simply all the fabricated spools with proper handling equipment (Hydraulic crane, Folk lift & vehicles).

6.4        Contractor shall prepare timber for spool storage.

6.5        Piping material will be withdrawn from the storage areas as the installation requirements occur.

6.6  Residual  piping material, especially short cut pipe shall be stored at the designated area with material ID marking. Contractor shall make endeavor to reuse the short cut pipe over than 200mm long if possible. All scrap shall be temporary
kept in same containers and segregated by type of materials, for future weighting and final reconciliation. Also, Subcontractor shall follow the “Material Control Procedure”.

INSTALLATION OF CARBON STEEL PIPING

6.1         General

1        All construction and installation works shall be executed according to design drawing, applicable code, standard, project specification, referenced procedure and general practice for above ground and underground work.

2        All welding work shall be performed in accordance with welding procedure specification (WPS), General welding procedure, and by qualified welder / welding operator.

3        All inspection / test shall be performed in accor dance with SATIP.

4        Modification to pipe routing may be necessary to avoid interference. Details of all modification shall be reflected on “As-Built” record drawings.

5        Prior to erection, the interior of all piping components shall be thoroughly cleaned of loose scale, sand blasting grits or sand and all other foreign matter by appropriate method.

6        Rigging of pipe components shall be performed in a good manner that will not cause any damage to the surface of the components.

7        Prior to the assembly of the component parts of the piping system, each prefabricated piece, straight length of pipe, or fitting shall be visually checked for dirt, rubbish, grease, loose scale, etc., and cleaned when necessary.

8        Orifice plate, rupture discs and permanent pressure gauges shall not be installed until the pressure test completed.

9        Piping shall be installed in a manner that resultant force on the equipment will be kept to minimum and particular care shall be taken at connection joint of pump, compressor and other mechanical equipment at which piping resultant force could cause misalignment.

10    Straight run pipe shall not be pulled through the pipe racks and pipe sleeper.

11    All piping opening shall be sealed before, during and after erection to prevent the ingress of moisture and foreign matter. Flanged or threaded ends shall be sealed with tape, Plastic cover or plywood, etc. This also includes open pipe
ends of piping being erected in pipe rack equipment in the plant.

12    Weld joint shall be inspected by Contractor’s QC Inspector. If the result of inspection is unacceptable, the joint shall be rejected and/or repaired and re-inspected in accordance with welding procedure specification and General welding procedure.

WELDING OF CARBON STEEL PIPING

1         Welding shall be performed in accordance with SAES-W-011 and approved “Weld control procedure”.

2         Repair welding shall be performed in accordance with approved “Welding Repair Procedure” and approved WPS.

3         Visual inspection after welding shall be performed in accordance with para. 17.5.1 SAES W-011.

4         Welding of Attachments

4.1        Material for Permanent Attachments Lugs, brackets, stiffeners and other permanent attachment welded directly to pressure-bearing components shall be same materials or equivalent.

4.2        Requirement for Welding of Permanent Attachments Welding of both internal and external permanent attachment welded directly to pressure retaining materials shall be performed by qualified welders and qualified welding procedure. The material of attachments is compatible to the component material to which is attached.

5         Welding Consumable Control 

5.1        All electrodes, filler wire and fluxes shall be controlled in accordance with “Welding material control procedure”.

5.2        Electrodes, filler wires and fluxes shall be kept clean, dry and properly stored according to manufacturer’s  recommendations.

5.3        No electrodes, filler wires or fluxes that are damage, damp, greasy or oxidized shall be used.

5.4        Consumables storage warehouse shall include a temperature and humidity controlled welding consumable and flux store, including holding and drying ovens.

5.5        Welding materials shall be controlled and issued by Welding Material Controller.

Welding Material Controller shall record the issued and returned status of welding materials in the Welding Material Issue Card every time.

NON-DESTRUCTIVE EXAMINATION (NDE)

1         Before non-destructive examination, all welded joint shall be visually inspected by QC inspector.

2         NDT shall be performed in accordance with “ NDT Procedure” provided by NDT Company.

HEAT TREATMENT

1         Preheat treatment shall be performed in accordance with SAES-W-011.

2         PWHT shall be performed in accordance with SAES-W-011 and approved “PWHT Procedure”.

BURIED PIPING

1     Excavation

1.1    The construction site shall be surveyed and set out by establishing grid lines and level of the work. The limits and elevation shall be in accordance with the approved construction drawings.

1.2    All necessary temporary works such as safety barriers, fences, safety nets, coverings and/or screen shall be provided to protect personnel and adjacent property from injury or damage caused by earthwork operation. Excavated material shall be properly stockpiled in designated area for subsequent re-use as filling material or shall be disposed off in accordance with local and national laws and regulations. The floor of all excavated areas and fill platforms shall be leveled off to provide a clean,
unobstructed work area.

2     Installation in the Trench

2.1    Installation of buried piping shall be followed the requirement of SAES-L-450

2.2    Prior to backfilling and during lowering, the piping shall be supported inside the trench with a maximum allowable unsupported length of three meters. Any voids below the pipe shall be carefully backfilled..

2.3 The pipe is embedded in clean sand with no stones (above and below pipe 200 mm) in a manner that will not damage the coating.

2.4   Detailed cleaning of piping in trenches is established and the following is checked daily:

1)             Pipes are internally cleaned by air blowing.

2)             Prefabricated spools have all foreign material removed from ID.

3)             Piping ends are covered daily after inspection.

2.5   Pipe handling including equipment used for handling is Company approved and good practice is in effect as follows:

1)             Piping is not rolled/dropped into trenches during unloading.

2)             Material is stacked properly to protect pipe and coatings.

3)             Slings are nylon or similar and wire rope slings are not used.

4)             Metal hooks are padded to prevent contact damage to coating

5)             Bevel protectors & end covers are undamaged and kept closed.

2.6  Insulating Gaskets/Kits are used for dissimilar metals connections; examples: a stainless steel flange to carbon steel flange, or a Cu-Ni flange to carbon steel flange, the potential for galvanic corrosion shall be determined in consultation with the Materials Engineering Unit of Consulting Services Department.

2.7 For UG pressure piping flanged connections, coated bolting materials are required to be installed as follows:

1)             ASTM A193-B7/ASTM A194-2H with ceramic-fluoropolymer coating (per 09-SAMSS-107).
Note: ASTM A320 Grade L7M bolts and Grade 7M nuts can also be used (SAES-L-109, Para. 5.2).  

2)             DURABOLT (Al-Khobar, KSA) brand can be used exclusively for SA work, but if DURABOLT is
not available, the following corrosion protection alternatives are used:

• Corrosion-resistant alloy bolting

• Painting exposed portions of the bolts and sealing the gap between flange faces

• Encapsulating the flange connection with heat shrinkable tubing.

3     Backfilling

3.1    QC has to ensure that all required testing was completed prior to backfill

3.2    The remainder of the backfill is placed in a manner that does not disturb the layer of clean sand around the pipe (sand pad). Select and approved Backfill does not contain rock larger than 50 mm size.

3.3  All rubbish and unsuitable materials inside the excavated pit will be removed.

3.4    Each layer will then be compacted and tested in accordance with ASTM D438 prior to placing the next layer. In-situ field density will be carried out by Sand Replacement Method and calculated of compacted material shall be more than 90%.

CORROSION PROTECTION

1.     UG metallic (CS) piping is protected against soil-side corrosion by both external coating & cathodic protection (CP) as
follows:

1.1    Coating systems are specified in SAES-H-002, Section 5.

1)             Buried CS lines are externally coated (APCS 104, APCS 105,APCS 113A/C for 4” and
smaller diameters)

2)             ALL buried line coatings are 100% holiday tested before burial

1.2    CP systems are specified in SAES-X-400 and SAES-X-600.

  (NOTE: SS & Cu-Ni do not require CP per SAES-L-133, Section 7)

3. PRESSURE TEST 

1     Hydro testing is performed as follows for UG Pressure piping designed to ASME B31.3 and applicable SA Line classes. Ensure that installation planning covers backfilling of lines for test purposes

1)             Fully  buried lines require a chart recorder and 24 hour test

2)             Partially buried lines require joint exposure (test times vary for services)

3)             Fully exposed lines require joint exposure (test times for testing)

2.  Pressure testing of plant piping shall be in accordance with SAES-L-150. .

4.        INSPECTION AND TEST

1     Notification

The schedule of the Inspection and test shall be informed to the QC by using “Request for inspection/test “ form in accordance with SATIP.

2     Inspection and Test

Inspection and test shall be performed and recorded in accordance with SATIP.

3     Holiday Test

3.1    Referenced Documents

ASTM Standard  A742/742M Specification for Steel Sheet, Metallic Coated Polymer Pre-coated Steel Pipe.

3.2    These test methods cover the apparatus and procedure for detecting holidays in pipeline type coatings.

3.3    Validity of Holiday test machine calibration : 1 year

3.4    Method A is designed to detect holidays such as pinhole and voids in thin-film coatings from 0.0254 to 0.254 mm (1 to 10 mils) in thickness using ordinary tap water and an applied voltage of less than 100V
dc. It is effective on film up to 0.508 mm (20 mils) thickness if a wetting agent is used with the water. It should be noted, however, that this method will not detect thin spot in the coating, even those as thin as 0.635 mm ( 25 mils). This may be considered to be a nondestructive test because of the relatively low voltage.

Method B is designed to detect holidays such as pinhole voids in pipeline coatings; but because of the higher applied voltages, it can also be used to detect thin spot in the coating. This method can be used on any thickness of pipeline coating and utilizes applied voltage between 900 and 20000V dc. This method is considered destructive because the high voltages involved generally destroy the coating thin spots.

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