Underground Piping and Conduit

Welded / Brazed Pipe

670221. Air Products Piping Specifications include 28-670221.
670222. Pipe to specification, proper grade, wall thickness, fittings, etc.
670223. Consider critical piping components such as schedule 80 pipe or non-standard materials (CrMo, Monel, etc.) on process piping and whether Positive Material Inspection (PMI) is required by the specifications. This type of materials testing may also be performed on valve seats, etc. and could be required on certain types of processes, such as HYCO plants.
670224. Pipe protective coating
        1. Applied in accordance with Air Products Construction Engineering Specifications.
        2. Coated pipe to be handled with lifting devices such as wide nylon slings or insulated tongs of appropriate strength to prevent damage to the pipe coating. Bare cables or chains shall not be used.

1. Pre-cleaned process lines placed under nitrogen purge (5 psig) to preserve cleanliness after it is in place, back filled, and pressure tested. Oxygen lines must be purged down to specified dew point prior to bottling up line. A pressure gauge shall be placed on the line to ensure nitrogen pressure is maintained on the pipe.
2. No internally varnished, lacquered pipe to be purchased for underground oxygen process.

1. Welding and brazing procedures formally approved by Air Products Quality Group.
2. Welders and braziers qualified in accordance with approved procedures. Qualifications available for each welder and brazier for each procedure that they are qualified.

1. Municipal inspection prior to back fill, if applicable.
2. If bottom of trench is uneven, sand shall be used to assure continuous bearing on bottom of pipe.

1. All pipe stub ups in concrete or soil are plumb on location and elevation (± 1/8”).
2. Flanges, elbows, etc., are more accurately installed after pipe is back filled to allow for settlement and accurate elevation placement

Non Metallic Pipe (HDPE)

1. AP material specification on hand.
2. Verify material received is as specified.
3. Installation:
   1. Certification of fusion operator by manufacturer or authorized distributor.
   2. Heat fusion joining method shall be in strict accordance with pipe manufacturer recommendations. Calibration certification of fusion equipment shall be provided.

Cast / Ductile Iron (Mechanical Joint) Pipe

1. AP material specifications on hand.
2. Verify that the material received is as specified…
3. Protective Coating
   1. Materials purchased with coating in accordance with AP Construction Engineering Specification 28-670221 (from factory).
   2. All tie rods, flange hardware, etc., are to be protectively coated after installation and tested prior to back fill in accordance with the specifications.
4. Check the type of mechanical joint, and that they comply with specifications, and have proper gaskets.
5. Hydrants, hose reels, houses, valve indicator, valve boxes, and all miscellaneous hardware hoses, etc., for houses in need to be in accordance with AP Construction Engineering Specification 28-670221
6. Tie rods and concrete thrust blocks installed on all fittings as indicated on drawings or specifications. Check rod material and thrust block size prior to backfill and pressure test.
7. Hydrants to be installed, anchored and stone added for drainage, as specified by APCI Std. 326263A. Check to see if the erection of a hydrant house or hose storage cabinet is required after backfilling.
8. Back filling shall not consist of rocks or stones; rather it shall be the excavated material or borrow sand. It shall be placed in layers not to exceed 9” and compacted.

Pressure Testing

1. All joints to be exposed, with back fill between joints to anchor pipe during testing. Check all tie rods and thrust blocks in place prior to test.
2. Local city, county, or state inspector requested to witness test, if necessary. Fire Marshall may ask to witness test. Project Engineering shall provide table of municipal inspection requirements.
3. Method established to measure amount of water loss per joint during test.
4. Test form filled out and signed off by all persons witnessing test.
5. System flushed – water hammer created to test thrust blocks, etc.

Storm, Process, Sanitary Drainage

1. Catch basins/ manholes/ oil-water separators on location and elevation in accordance with drawings. Pipe inverts are critical to proper function of gravity systems.
2. Verify that the material is as specified whether, concrete, cast iron, HDPE, etc.
3. Verify that the joint material is correct –mortar, neoprene, fusion welding, etc.
4. Installation
   1. Develop gradient and work from lower invert/ catch basin to higher invert/ catch basin.
   2. Use sand bed to assure smooth gradient

1. Clean out required if trapped lateral exceeds 3′ from branch.
2. Traps on drains cannot exceed 2′ vertical drop from drain elevation.

General

1. Check integrity of Cathodic protection exothermic welding, wiring, and test box, if installed.
2. Locate by manual pothole excavation all existing underground electrical and pipelines in area of new undergrounds.
3. As-built made prior to back fill showing all interferences, pipe location, pipe depth, etc.
4. Compaction/ density reports issued by testing laboratory in area adjacent to or under foundations.

Conduit

1. Rigid Polyvinyl Chloride (PVC) conduit is to be Schedule 40, 90 Deg. C with bends being made using heater box bending equipment in accordance with manufacturer recommendations.
2. Underground high voltage conduits shall be concrete encased. Refer to contract drawings. Red dye shall be mixed or spread on top of concrete per specification. Warning tape shall also be installed in accordance with drawings and specifications.
3. Verify all risers are the specified material. In most cases they will be rigid galvanized steel. In some cases (e.g. single phase per conduit) PVC is specified to avoid inducing current into conduit.
4. Once cables are installed and testing is complete, all conduit openings to be sealed with joint compound.
5. All open-ended conduits to be kept capped during installation. If the electrical contractor differs from the underground contractor, the electrical contractor shall be responsible to verify all underground conduits are free from debris and water prior to any cable installation. Verify by pulling a swab (pig) or mandrel through the conduits.
6. Embeds and stub ups on location are plumb, braced, and able to continue run with second phase contractor. Thread a 10-foot section on and plumb while encasing or backfilling to ensure plumb.
7. Do not relocate conduit runs without Design Engineering approval, especially high voltage conduit.
8. Backfill with sand and clay mix per Air Products Fabrication and Erection Specification  28-620304 for multi-bundle banks of conduits.  Concrete (2000 psi) with red dye is acceptable option.
9. Continuity checks of all conduits upon completion using mandrels per Air Products Fabrication and Erection Specification 28-620304.
10. All grounding grids shall be Biddle Tested and documented. No more than 5 ohms to ground allowable.  Refer to Specification 28-620300 for grounding test requirements.
11. All grounding cad weld connections checked using one-pound hammer test. Burndy compression connections are acceptable for aboveground connections.
12. In areas of high foundation concentration, foundations must be placed prior to conduit to avoid damage to conduit, especially augured foundations.
13. All PVC conduit banks installed below grade that are specified on contract drawings as “concrete encased” shall be rigid schedule 40 PVC conduit and encased in a concrete envelope. Minimum dimensions for concrete envelopes shall be 2” between conduits and 3” inches between conduits and earth. Concrete encased conduit must have red dye.
14. All conduits under roadways will be concrete encased.
15. All underground runs of nonmetallic conduit in duct banks, whether direct buried or concrete encased, shall be rigidly supported to maintain horizontal and vertical spacing using plastic conduit spacers located at 7′ intervals for conduit support and spacing. The bottom of the trench shall support the base of each spacer, either by direct contact or indirectly with leveling shims.
16. Prior to back fill or concrete placement, get municipal inspection as necessary.
17. Ensure all concrete pull boxes and motor control pits are watertight and conduit penetrations are grounded.
18. Verify accurate location of conduits for entry into switchgear.

QC Documentation

1. Some tests require an AP sourced testing company. The construction home office shall write the PO with assistance from the field, to ensure insurance requirements are met.  Include in the QC, qualifying certifications of the lab and of the technicians performing work.
2. Holiday Spark Test results.
3. Approved welding procedure specification (WPS)/ Procedure Qualifications Record (PQR)
4. Welder and brazier qualification records.
5. X-ray reader sheets, and x-ray technician certifications.
6. Non-Destructive Test (NDT) service reports for x-rays and dye-penetrate test
7. Holiday spark testing logs.
8. Pressure testing (all sections).
9. Back filling density test reports with certification of equipment and technician.
10. Water and air test records for gravity drain systems.
11. Potable water disinfectant test records
12. As-built information/drawings.
13. Biddle Test reports on ground grid.
14. As-built information
15. Conduit mandrel continuity checks.
16. Local inspection reports and final acceptance.
17. Pipe cleaning inspection reports.