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Lord of the O-rings Nigel Sanger, Technical Manager at JG Speedfit, explains why O-rings ensure the smooth performance of a push-fit plumbing system and advises how installers can select a high quality and reliable product DOMESTIC PIPES are often exposed to extreme conditions, including environmental, chemical and temperature changes. Moreover, the variable properties of water present numerous challenges when designing plumbing systems. Adverse weather conditions are a key reason behind pipe failure. As water expands when it freezes, forming a plug within the pipe and as this process continues, the expanding ice plug raises the pressure within the remaining pipework, causing it to burst. Heating up water will also cause it to expand, increasing pressure within the system. Worth noting also is that liquid has a higher boiling point as pressure rises. A sealed heating system typically runs at around 2 bar, subsequently raising the boiling point to around 120oC. While plastic offers excellent thermal resistance, O-rings must also withstand the forces resulting from expansion and raised pressure within the pipework. Used to create a seal within the pipe connection, they prevent any risk of leakage from the water inside, ensuring the smooth running of plumbing systems. Ensuring the right choice of O-ring material can help provide a more reliable product which is less prone to wear and tear. Strength and pressures It is safe to assume that not all O-rings are the same. While there are standard ASTM, ISO and DIN procedures for conducting tests on rubber materials, industry requirements differ depending on the conditions the O-ring is likely to face, these include high and low temperatures, pressure, the type of liquid the pipework will carry and life expectancy. One way to understand the strength of the O-ring is by looking at the internal pressures they have been designed to work under. For example, EPDM rubber O-rings used by JG Speedfit are rated at 12 bar when used with cold water. As a comparison this is about 5 or 6 times the air pressure in a typical car tyre, which is between 2 to 2.5 bar, and more comparable to the pressure within a lorry tyre, which can approach 10 bar. Nobody would exceed their recommended tyre pressure by a factor of five, yet on JG Speedfit’s internal laboratory tests the O-ring is often subjected to fluid pressure tests at 60bar without any failures. Most O-ring failures occur during installation, with factors such as sharp-edged pipes cutting or displacing the O-ring, and while it is the O-ring that has been damaged, the reasons for failure are primarily due to poor installation or understanding of the product. When a badly scored pipe is inserted into the fitting, this can be the cause of system failure and leakages. The scoring damage acts as a miniature trench under the O-ring creating recesses where water can collect. Push-fit fittings utilising O-rings can sometimes suffer from high insertion forces, which can be tiring and eventually lead to pipes not being fully inserted into the fitting. The JG Speedfit Twist and Lock fitting, however, has been cleverly designed to minimise insertion force, while the unique Twist & Lock technology then ensures the security of the connection. Another important approval to be aware of is from the Water Regulations Advisory Scheme, also known as WRAS. O-rings receive WRAS Material Approval if they demonstrate that the material doesn’t contaminate the water, therefore satisfying the requirement of regulations and bylaws. Additionally, product reliability can be assured if they’re sourced in the UK from a leading manufacturer. The quality of an O-ring is not something most people would consider when installing a plumbing system into a home, however it is becoming more important for installers to ensure that the materials they are using are tested to the highest standard. Not only can it provide an installer with a better finish, it also contributes to the confidence that the end user has in a system which won’t burst and cause inconvenience. For more information about JG Speedfit’s manufacturing qualities, visit speedfit.co.uk • 24 Spring 2017


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