How to comply with spacing design requirements, codes and standards

Plans isolated on white.With the launch of the new WSAA code (WSA PS 324) governing casing spacers it may be surprising to hear that it is not uncommon to find a contractor resorting to the use of make-shift spacers to centralise their pipe during installation.

Contractors throughout Australia are often caught-out using hand-made wooden skids as a shortcut, for they have either forgotten to order a spacing product, or have overlooked the importance of spacers altogether.

Apart from complying with the WSAA code, choosing a well-designed spacer system for pipeline installations is an important element in maintaining the integrity of the pipe, as well as reducing delays, costs and reputational damage.

According to Jason Linaker at Kwik-ZIP, not only do home-made spacers fail to abide by the code, they are simply too risky.

“If the pipe annulus is to be grouted, hand-made spacers can inhibit grout path flow. They are unsuitable for gravity sewers and fly in the face of any design which specifies proper spacers.

“Make-shift wooden spacers may rot over time and leave behind a void in the grout seal.

“Wood also has a very high coefficient of friction, resulting in much higher running forces on long installations, and excessive abrasive wear to the runners, potentially resulting in complete failure of the spacer,” said Mr Linaker.  

Other challenges when attempting to comply with spacing codes

  • Strength: First and foremost, contractors find it difficult to find a spacer strong enough for their particular installation that doesn’t have to be specifically designed and custom-made.
  • AS/NZS 4020:1999: Another test for suitability in the case of water main use, is how the spacer material reacts when coming into contact with potable water, and what harmful contaminants may be released into the water. As such, if a spacer is to be used in-line on a potable water service, it should be certified as compliant with AS 4020.
  • Corrosion: Corrosion is the next problem, and finding a spacer that has no corrosive parts is a challenge.  Fabricated metallic spacers are subject to corrosion and can impart corrosive damage to the pipeline.  In some cases metallic spacers can damage the pipe, particularly if the carrier pipe is a non metallic composite pipe such as fiberglass or PVC.
  • Diameter : Finding an ‘off the shelf’ solution that suits the right ID/OD combination is also a challenge, especially if the pipe diameter changes at different points.

How Kwik-ZIP can help

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According to Mr Linaker, kwik-ZIP spacers help contractors comply with the relevant standards and provide a hassle-free and beneficial alternative to home-made spacers.

“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 effluent once the sewer becomes active.

“If grade correction is necessary, kwik-ZIP spacers can be installed with varying runner heights within discrete spacers to re-align the carrier pipe.

“In other types of infrastructure, the spacers help contractors comply with the design specifications in a simple, versatile and cost effective way as they don’t have to custom-make a specific spacer or have a workshop manufacture steel spacers.

Mr Linaker said that because kwik-ZIP systems are made from a high grade thermoplastic and therefore corrosive-free, they are resistant to installations involving water, including seawater.

For full details of PRODUCT SPECIFICATION WSA PS – 324 CASING SPACERS, click here (p118).