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Storing, Jointing and Laying of HDPE Pipes

Storing HDPE pipes

 

HDPE Water Pipes manufactured as per IS 4984:2016 (Supersedes IS 4984:1995) are UV protected due to carbon black added during the manufacturing process and hence may be stored in open or covered area.

HDPE pipes for other application, which may not have been manufactured by adding carbon black, are not UV resistant. Such HDPE Pipes are prone to damage under direct sunlight and these HDPE pipes should stored in covered area protected from direct sunlight.   

 

Jointing of HDPE Pipes

 

HDPE Pipes are joined using the following popular techniques:

 

  • Butt fusion welding

  • Electrofusion welding

  • Compression Fittings

  • Flanged Joints

 

The principle of fusion welding is to heat the two HDPE pipe surfaces to a designated temperature and then fuse them together by application of sufficient force. This force causes the melted materials to flow and mix, there by resulting in fusion.

 

Butt Fusion Welding

 

HDPE pipes and HDPE fittings, to be joined by butt fusion welding preferably be of the same wall thickness. The HDPE pipe surfaces to be joined shall be dry and dust free and shall be scraped before fusion to remove surface material.

 

  1. The HDPE pipes surfaces to be joined are clamped on the butt fusion welding machine.

  2. These HDPE Pipe surfaces are then scraped using the scrapping tool so as to remove any unevenness in the surface.

  3. The surfaces of both HDPE Pipes are then cleaned to remove any dust or external material.

  4. The heating plate is then placed in between the HDPE Pipe surfaces and the surfaces are then pushed onto the plate for heating to a specific temperature.

  5. Upon heating, the material of the HDPE Pipe surfaces melt.

  6. The heating plate is then removed and both the HDPE pipe surfaces are then pushed onto each other.

  7. The melted material of both the HDPE pipe surfaces fuses together to make a seamless joint.

  8. Sufficient cooling time should be given to the joint otherwise the joint may fail under pressure.

 

The reference video to illustrate this HDPE Pipe jointing procedure is given below:

 

     

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Electrofusion Welding

 

Electro fusion is a heat fusion process where a coupling or fitting containing a resistance wire is used to join the pipes and fittings. The jointing areas, that meets the pipe surface and the inside the fittings are overlapped and the resistance wires inside the fitting are heated by electric Current. During heating, fitting and pipe materials melt, expand and fuse together. Heating and cooling cycles are automatically controlled by the bar code arrangement on the fittings and machinery used. Electro fusion is the only heat fusion procedure that does not require longitudinal movement of the joinable surfaces. It is frequently used where both pipes lengths are constrained, such as for repairs or tie-in joints in the trench. Joints between dissimilar polyethylene grades and different wall thicknesses can also be made using electro fusion, as the procedure readily accommodates polyethylene grades with different melt flow rates and is independent of the pipe wall thickness.

 

The reference video to illustrate this HDPE Pipe jointing procedure is given below:

 

 

Compression Fittings

 

Compression fittings are detachable joints and are made of metal or plastics like polypropylene or a combination of both. Compression fittings form a tight seal by applying a compressive force to the pipe and pipe fitting. The fitting is compressed against the pipe with a force sufficient to eliminate all space remaining in the joint, thus preventing the fluid from leaking. It is critically important to the integrity of the fitting that excessive force is avoided in tightening the nut. If the fitting is over tightened, the gripper (clip ring) will deform and cause leaks. Over tightening is the most common cause of leaks in compression fittings. As a general rule, a compression fitting should be ‘finger tight’ and then tightened one turn with a wrench. The fitting should then be tested, and if slight weeping is observed, the fitting should be slowly tightened a bit more until the weeping stops.

 

For HDPE Coil pipes, of small diameters (upto 110 mm) where the working pressure do not exceed 1.6 MPa, jointing by polypropylene (PP) compression fittings is generally recommended over fusion jointing.

 

The reference video to illustrate this HDPE Pipe jointing procedure is given below:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Flanged Joints

 

Flanged joints are used for jointing HDPE pipes to valves and vessels and large size metal pipes, and where pipes of other material are to be joined with HDPE pipes. Flanged HDPE Pipes are made by inserting Metal / HDPE Slip on flanges on both the ends of the HDPE Pipe and then jointing HDPE Stub Ends at both the ends of the HDPE pipe using butt fusion welding.  

HDPE Pipe Laying

 

HDPE pipe line may be laid alongside of the trench and jointed there and then shall be lowered into the trench. Most Government departments recommend trench depth of 1.5 Meters. When the pipe is joined before lowering in trench, its temperature may be more than the surface temperature and hence the pipe may have expanded in length, hence when its lowered in trench, sufficient cooling time should be given as the HDPE pipe may contract according to its surrounding soil temperature, before connecting it to an anchored joint.

 

While laying in rocky areas, suitable sand bedding should be provided around the pipe and compacted.

 

The trench depth and width shall be as per Fig. 12 Table 3 of IS 7634 Part 2.

 

For any details or clarification, please feel free to drop us an email. We will be more than happy to provide any guidance required. 

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Akshat Engineers Private Limited

E-315, Lal Kothi Scheme,

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Jaipur - 302015 (Rajasthan, India)

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