TPi May 2015

Dismantling joints in the 21 st century By Engineered Piping Products Ltd, UK

T ired of leaking dismantling joints/pipe misalignment couplings? Tired of the cost you have to pay for them? Tired of the length of time it takes to install and remove them? There is an alternative solution – rubber expansion joints. This article will try to describe all the advantages and disadvantages of both systems.

Conventional dismantling joints customer advantages and disadvantages

where corrosion is a huge issue and most of the time clients will insist on all metal surfaces in contact with seawater to be in Duplex or Super Duplex materials? A very expensive option!

advantage – Couplings can absorb up to 10mm expansion and contraction, flange adapters up to 5mm, which allows for movement on bridge crossings, in chambers and pump stations. disadvantage – What about greater movements, such as 20mm axial extension and compression just for installation between flanges? Or misalignment between the flange faces? advantage – The standard finish for all products is black Rilsan Nylon 11, which is highly resistant to impact, corrosion, abrasion and chemical attack. However, other coatings such as shop coat, hot dip galvanising, zinc spray and epoxy coating can be supplied as required. disadvantage – Coating can be easily damaged during fitting due to poor working/installation practices. What about heavily chlorinated seawater environments such as the Middle East,

advantage – Flange adapters are often used to permit dismantling of valves in flanged pipe systems.

disadvantage – Have you ever tried remove this coupling or dismantling joint? Especially when the coupling has been there for a few years! advantage – Couplings can offer up to 6° of angular deflection, flange adapters 3° – to allow for the connection of misaligned pipes; take up ground settlement at structures; and to lay pipes to large radius bends. disadvantage – What about thermal movements, and extra ground settlement such as in desert environments like the Middle East? Desert sand is always on the move, even years later. Also consider pump surge, and the high forces to move these joints under operation/pressure. Product design benefits 1 – simple to fit Simple installation in any weather and trench conditions, even underwater? Questionable? 2 – long life expectancy Elastomeric sealing gaskets are designed to have at least a 50-year lifespan. Very questionable? Rubber degrades 1 Shore A per year of its life under operation and exposure to weather conditions. Depending on the grade of rubber it will probably start out around 65 to 70 Shore A. When it reaches 80 to 85 Shore A in hardness it should be changed, so this

Conventional dismantling joints

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