VACUUM & PRESSURE TESTING
FOR MAINTENANCE SHAFTS
SMS Maintenance Shafts (MS) are injection moulded in Polypropylene (PP) and the sockets and spigots are not capable of being jointed with solvent cement. The socket/spigot joints use elastomeric seals and it is recommended that vacuum testing be used in preference to pressure testing to ensure the riser does not disengage at the base/riser joint.
Vacuum Testing – Chambers
When vacuum testing the lockable cap and lid is used to seal against vacuum at the top of the shaft. Apply a test vacuum (negative pressure) as specified by the Regulatory authority. Observe all safety practices and requirements during the vacuum test.
Pressure Testing
Method 1:
To avoid the riser pipe disengaging from the base unit when under pressure apply a counterweight to the cap and lid at the top of the riser to stop any disengagement of the riser pipe at the riser connection to the maintenance shaft.
Method 2:
SMS supply a ‘Split pipe ring’ and ‘Flange Collar’ to fit the riser pipe adjacent to the base unit to lock the riser pipe into the embedment material and avoid any disengagement. The assembly is simple and is outlined as follows:
- Solvent Weld the supplied split pipe ring to the PVC riser 110mm from the bottom of the Riser Pipe (End being fitted to the maintenance shaft) See Figure 1 below.
- Fit the riser pipe to the maintenance shaft and back fill as specified to the height of the split pipe ring.
- Slide the ‘Flange Collar’ down the pipe until it stops at the welded split ring (see Figure 2) and install a lockable cap and lid to seal the assembly.
- Complete embedment of the riser ensuring adequate fill and compaction under the Flange Collar.
- The pressure test can now be undertaken as is specified and the riser pipe will be securely held in position by the weight of the embedment material on the Flange Collar.
- Observe all safety practices and requirements during the pressure test.
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Split pipe ring solvent cemented to riser
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Flange collar fitted to riser pipe |