Maintaining integrity with spacer best practices

Adopting best practices for the selection and use of casing spacers will help maintain the integrity of a pipe for a durable installation. The Water Services Association of Australia (WSAA) product specification WSA PS-324 provides a useful guide to best practices that all trenchless contractors should follow.

WSA PS-324 covers the correct protection of carrier pipes when installed inside casings and provides details of best practices and various requirements for spacers. These include the use of materials, abrasion resistance, requirements for wear pads, runner height flexibility, and minimum runner spacing around the pipe.

Jason Linaker, creator of the Australian-owned kwik-ZIP HDX series spacer, which has been successfully appraised by WSAA against PS-324, said that following best practices is important when installing pipes.

“Although spacers are usually only a small part of the overall pipe installation process, following specifications and best practices as set out by WSAA can significantly increase the life expectancy of the carrier pipe by keeping it free from corrosion, carrier pipe damage and long term integrity of the grout envelope.”

Spacer best practices

The best practices for casing spacers outlined in WSA PS-324 include:

  • Cased crossings for gravity sewers need to be grouted and casing spacers should be placed at intervals not exceeding 1m to ensure that correct grade is maintained
  • Correct grade and alignment in graded sewer lines is more easily achieved if the casing spacer is of a type that allows for different height runners at the top of the spacer versus the bottom of the spacer
  • If the carrier pipe is being grouted into the casing, the interval of the casing spacer design may be increased. However, consideration needs to be given to the potential for upward forces on the casing spacer due to flotation of the carrier pipe during the grouting process
  • The outside diameter (OD) of the casing spacer should be at least 10mm less than the smallest inside diameter (ID) of the encasement pipe to minimise the potential for jamming. Internal protrusions such as weld beads should also be taken into account

“kwik-ZIP spacers help contractors meet WSAA requirements and best practices for all pipe installations,” Mr Linaker said.  

“HDX Series spacers are made from a high-grade thermoplastic material and have integrated rubber pads for slip resistance, ensuring they will not deteriorate over time which could leave voids in the grout envelope. If grouting isn’t used, they will continue to support the weight of the pipe and won’t move or wear.”

kwik-Zip spacers also have a flexible design, allowing various runner heights to be used for different pipe/casing combinations.

“The flexibility of the spacers’ design reduces the potential for jamming, and helps in cases where grade correction is necessary as they can be installed at varying runner heights within discrete spacers to re-align the carrier pipe,” Mr Linaker said.

“In gravity sewer installations, kwik-ZIP spacers keep the pipe on grade with a predictable response to grout flotation forces.  

“kwik-ZIP’s runners provide robust support so contractors can have confidence in the fact that there will be no pooling of waste fluid once the sewer becomes active.”

A one stop solution

Due to kwik-Zip spacers having a flexible design, contractors only need to purchase one product group across the whole job site. This cuts down on confusion about which product to use where, and speeds up installation.

On-site assembly is easy and no specialist skills are required.

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