Information

How highly do you value your sewer assests?

Pipelines form an integral part of an authorities sewer asset and are in constant need of repair or modification to suit the needs of growing communities.

To cut in a junction or repair a damaged pipe is an expensive process, tying up machinery and labour, and has a real impact on the community in terms of disruption to services and traffic.

For these reasons any repair or modification must be permanent to prevent duplications of effort and to conserve scant resources.

Once the sewer trench is open a quick repair is highly desirable, and in conditions that are muddy, unsanitary and often carried out in confined spaces the repair must be effective and long lasting, requiring a minimum of technical expertise and equipment.

There exist on the market several brands of pipe repair couplers of various quality and the discerning engineer needs to be aware of the wide variations in performance of these products.

Key issues

Elastomers:

The elastomeric materials used in pipe couplers are grouped into two performance orientated categories in AS/NZS 4327. These being:

• Type A – Plasticised PVC, and
• Type B – Vulcanised Rubber

The performance of these two materials varies dramatically over time. Internationally the overwhelming trend is for local bodies to specify exclusively Type B elastomers. This choice is made simple due to the long term advantages Type B elastomers offer over plasticised PVC.

Stress Relaxation

A coupler achieves and maintains an effective seal by resisting compression under stress, thus imparting an interface pressure against the pipe surface. Over time all materials will relax under this pressure and the seal effectiveness will be diminished. The elastomers ability to resist this relaxation determines the overall amount of time it will retain an effective seal.

The attached chart graphically illustrates the performance differences between the two types of elastomers. It is important to note that the accepted minimum long term interface pressure required to prevent root intrusion into pipe systems is .35 mPa as shown.

PVC materials typically relax at a rate of 15% per decade, compared to 6% relaxation per decade of Type B. It can be seen that from the same initial contact pressure, the higher rate of relaxation of the PVC material means the joint drops below .35mPa after a in as little as 1000hrs, whereas Type B elastomers retain an effective barrier against root intrusion for well over 100 years.

This clearly demonstrates that whereas Type A elastomers quickly deteriorate, in as little as 1 year, Type B Elastomers will maintain an effective seal for over 100 years.

For this reason FlexSeal couplers use only Type B Elastomers!

Stainless Steel:

Stainless steel, like any metal is subject to corrosion. Ground conditions can provide varying aggressive environments and be devastating on some grades of Stainless Steel. Tests conducted by SA Water show that #304 stainless steel is highly susceptible to corrosion, whereas #316 is highly resistant, and remains almost unscathed in conditions that completely destroy #304.

For this reason all FlexSeal metal components are #316 Stainless Steel.

Superior Design

The best materials are limited without careful attention to design. FlexSeal couplers incorporate several innovative design features which ensure superior performance and longer effective life.

Couplers can be supplied with or without shear bands dependant on the application.

• Shear Bands – FlexSeal Standard couplers are recommended for Civil & Local Authority applications and incorporate a wide shear resistant band around the outside of the coupler. This assists in maintaining pipe alignment and protects of the elastomeric membrane from tears under load. These features reduce the chance of blockages by ensuring pipes stay aligned and eliminating pipe lipping
• High Torque Tensioners ensure a minimum of stress relaxation occurs and are designed to enable simple tightening. The design sets the bolt at the perfect angle adjacent to the tangent of the coupling and optimises the conversion of torque applied to tension in the clamping band, and hence maximises the sealing pressure for a given torque

FlexSeal couplers provide the local authority with a simple to install, long lasting and effective repair coupling which will preserve the integrity of the sewer asset. Installers can be confident that a repair, once completed will last the life of the pipe system.

FlexSeal are cost effective and available in a wide range of sizes, with reducing bushes to allow connection from almost any pipe material to any other material in all the commonly used diameters.