All the piping materials received at site will be inspected, upon receipt on the project site. Any discrepancies / damages should be notified and reported to the supplier for further action.
Materials found not suitable for site use will be removed from site immediately. All construction/inspection/testing works shall be carried out in accordance with project specifications.
Sewerage piping installation work shall be carried out by the site plumbing staff under the guidance of plumbing Engineer and shall further be checked and approved by MEP project manager.
MEP engineer and supervisor shall co-ordinate regarding location of installation i.e. clearance with other services.
Future disconnection and relocation shall be done as per the shop drawings which are to be coordinate and approved by the civil project manager & MEP manager and civil construction manager as applicable.
List of materials:
- HDPE Pipes
- HDPE fittings: Elbows, tees (20mm to 200 mm)
- Rubber clamps
- GI Nuts & Bolts
List of plant & equipment used for the sewer system piping work:
- Measuring tape
- Tool Box
- Measuring Tape
- Hack Saw
- Spirit Level
- Roller/Plate Compactor
- HDPE Butt Weld/Electro Fusion Weld Machine
Health, Safety and Environmental Requirements
A lifting permit to be obtained prior to Unloading of pipes. Ensure the crane and the operator is having third party certificate. Ensure all lifting appliances are load tested. Barricade the area, place suitable sign boards.
Use necessary PPEs while unloading the pipes and accessories.
A qualified rigger shall control the operation of the crane. Advice the operatives to be away from the load. Control the movement by using tag lines at both ends of the pipes.
If fork lift is in use, keep two sentries at two sides while unloading takes place.
No personnel shall be allowed to be in the truck while loading/unloading takes place. No personnel shall be allowed to pass through the lifting load.
Do mechanical handling as far as possible. Reduce the load to be handled manually. Rotate personnel who are handling load manually. Training on ergonomics of manual handling to be provided to operatives engaged in manual handling. Ensure that safe lifting technique is strictly observed by operatives. Operatives shall always use suitable PPE for the assigned job.
Obtain Excavation permit before commencement of job. Ensure the Back hoe loader and the operator is having third party certificate.
Conduct a tool box meeting with Foreman, operator and workers. Hard barricade the area keeping 1.5 meter from the edge of the excavation.
No vehicular movement is allowed within 1.5 meter distance from the edges of excavation. Ensure a qualified banksman controls the excavator. Excavated soil should not be stored at the edges. Provide minimum two ladders for access and egress. No personnel should be allowed within the radial arm distance of the back hoe loader. Provide necessary side wall protection if necessary. Check for any toxic gases in the excavated area.
Operation of HDPE Fusion Welding Machine
- TOOL BOX TALK with foremen and workers before start.
- Use Personal protective equipment (PPE) specific to the HDPE pipe work such as heavy duty hand gloves,
- Personnel should be trained on fusion welding of HDPE pipes.
- Hot work permit to be obtained
- Ensure Fusion welding machine is inspected prior to use by a competent person.
- Keep suitable fire extinguishers near the working place.
- Ensure no hydraulic fluid leakage from the control system of the fusion welding machine.
- Ensure pressure and temperature gauges are serviceable.
- Extreme care should be taken while laying of pipes inside the trench.
- Fingers to be well clear from the pipes while joining.
- Use only industrial electrical sockets while carrying out electrofusion welding.
- Ensure the welding machine and electrical systems are not in contact with water inside excavation.
Working inside sewage man hole- Confined space:
- Confined space entry procedure to be followed while working in underground sewage pit:
- Obtain confined space entry permit.
- Ensure personnel are trained for confined space entry procedure.
- Conduct a tool box meeting prior to commencement of job.
- Ensure the atmosphere inside the confined space is tested for presence of any toxic/flammable gases.
- Ensure the oxygen level inside the space is between 19.5% and 23.5%.
- All emergency rescue equipment shall be in place.
- Provide sufficient lighting, exhaust fan, etc.
- An emergency rescue team shall be available in the area and communication system should be there.
- Do not use any gasoline/diesel driven equipment in the sewage man hole.
Handling and Storage of HDPE Pipes
Care should be taken to avoid impact with any solid object (i.e. other pipes, ground stone, truck side etc.) by using straps to load and unload the pipes quickly and efficiently thus avoiding damage to the pipes.
Flexible slings or straps should be used combined with a mobile crane for unloading of pipes.
Caution: Hooks must not be used at the pipe end to lift the pipes, nor should the pipe be lifted by passing a rope or sling through the pipe.
Fittings are delivered from the factory and must be stored in a shaded area, protected from direct sunlight, until they are ready for use.
These may be stored in the open for long periods provided they are on soft ground or cradles.
During storage ensure that the surface on which the pipes lie is smooth.
Pipes are not exposed to sharp edges or linear loads while using excavator crane etc.
The recommendation for maximum storage height (h) for HDPE pipes is as per table given below
PIPE PRESSURE CLASS
It is preferable to unload pipes alongside the trench directly from the truck. If the trench is ready, string out the pipes on the opposite side to the excavated earth.
Pipes must not be stored on rocks.
Sewerage Piping Installation Sequence of Work
Mark the routing of pipe work according to approved shop drawings to start the excavation works. All horizontal drainage piping shall be installed with 1% slope unless otherwise indicated.
The trench shall be excavated by a Hand/Back hoe Loader, after the area of excavation is identified.
Formation of the trench must consist of stable, uniform and smooth soil devoid of irregularities for direct laying of pipes, the width of the trench should not be less than the pipe diameter, plus 300mm from each side, and not wider than the pipe dia. Plus 600mm from each side. The depth of the trench shall be 150mm below the pipe invert level where a layer of 20 MPA. Concrete is laid with on average depth of 75 mm to maintain the 150mm below invert level of the pipe (wherever applicable).
The excavated material shall be placed on one side of the trench leaving the other side clear for pipe handling, and the bed of the trench should be smoothened out evenly to provide a uniform support for the pipe.
While excavating 2 number of labors should be present with the excavating machine to avoid any damages that can occur while excavating to any of the underground services.
Electro fusion jointing procedure
Squarely cut pipe ends to be jointed.
Clean dirt etc. off approximately 500 mm of pipe ends using clean cloth.
Using the mechanical scraping tools, remove the entire surface of the pipe uniformly to a depth of 0.2 – 0.4mm, preferably as a continuous scarf over the area identified i.e. in excess of the insertion depth.
Do not touch scraped area.
Fit coupler to end of single or movable pipe. With central register against pipe end mark depth of penetration.
Remove coupler and refit onto end of fixed pipe With central register positioned against pipe end mark depth of penetration
Loosely fit retraining clamp, to fixed pipe.
Position single/moveable pipe end into coupler
Ensuring that coupler is central in clamp and pipes are inserted to the depth of penetration mark, fully tighten the clamp.
Rotate coupler slightly to check that pipes are not misaligned.
Connect leads to terminal on coupler.
Check fusion time indicated on label and input this on control box timer.
Press control box start button and ensure that fusion cycle completes.
On completion of the heating cycle.
The melt indicators should have risen if there is no apparent movement of the melt indicator, the joint should be cut out and make a new joint.
Allow cooling time indicated on label.
Remove leads and restraining clamp.
Lower the pipe into trench using straps or slings from an excavator boom if no separate equipment is available.
Sewer System Leak Testing
The piping system to be tested shall be closed by plugging and blanking all openings in the system in an approved manner .
Suitable plugs are inserted at the lower end of the drain or sewer and at the head of any connections.
A suitable bend together with a vertical length of pipe is fitted at the head of the sewer or drain to provide the necessary test head.
The system is then filled with water.
A test pressure of 1.50m head above the crown of the pipe is applied at the higher end of the drainage or sewer system ensuring that the resultant head at the lower end does not exceed 4.0m where gradients are steep, it may be necessary to test in sections to avoid exceeding this figure.
The sewer or drain under test should be left filled with water for minimum 2 hours, to ensure that all piping and joints are not leak.
During the water test, precautions should be taken to prevent any movement of the drain or sewer.
All ends shall be plugged after completion of test to protect from debris.
After successful testing & inspection of pipe work, covering of pipe work can proceed as per approved drawing details.
Back Filling the Underground Sewerage Piping
Backfilling shall take place immediately after the entire test has been approved by the Engineers.
The excavated material shall be used as backfilling material and backfilling material shall be uniformly wetted with water.
Backfilling shall be done in layers that do not exceed 300mm of well compacted layer which the compaction will be done by a plate compactor for the said layer; each layer of backfilling shall proceed after the Engineers approval for the compacted layer is given for the previous layer.
Inspection, Testing and Commissioning
Check materials are as per approved material submittal.
Ensure that there are no hard protrusions and large stones on the bedding and bedding is acceptable to proceed with pipe lying.
Check the size of pipe is as per approved drawing before laying in any section.
Make sure that the levels and slope of installed pipes are as per approved shop drawing.
Check that all joints are made properly and are clean.
Before backfilling check that pipes have been hydro tested for leaks.
Check that all open ends have been closed for protection from construction debris.
Inspect and check that concrete encasement has been provided on pipes having less than 1 meter cover.
Check that backfilling has been carried out as per approved drawing details.