The non-return valve (also known as a ‘check’ or ‘reverse flow’ valve) is often an overlooked component in a steam and condensate system.
With a very simple function and a compact and robust construction, the check valve plays a critical part in allowing a piped system to operate correctly where multiple pressures and flows connect.
Often, check valves are fitted to outlets of pumps, inlets to manifolds and piping arrangements, connections to tanks and vessels, and sometimes are even used as vacuum-breakers. Without such a device, issues may arise from the undesirable side effects of back-flow and/or over-pressurisation into other parts of the system, leading to safety and operational problems.
The following steps can be taken to ensure the lifespan of this critical component:
A check valve is frequently installed in a pipeline at ‘line size’, e.g. a 50mm valve is installed in a 50mm pipe. However, a check valve is a type of control valve, so it is vital it is correctly sized for the role and flow. An ‘oversized’ valve will not open fully and will ‘clatter’. The seat and spring will wear out very quickly resulting in broken parts. An ‘undersized’ valve will result in a high-pressure drop which can constrict steam or condensate flow and waste pumping energy.
There is more than one type of check valve mechanism. Different designs are suited to different duties and applications and it is once again important to ensure the correct type is used for the best results, longevity and reliability. For instance: a spring-loaded RK-type valve can be used in any orientation including downward flows, whereas a hinged CB-type (counterbalance) check valve cannot. However, a CB-type check valve has a smaller pressure drop across it making it ideal for low-pressure applications.
Sometimes a check valve is installed where poor pipework layout can change the way the valve or system behaves, e.g. it can be placed at the top or bottom of a rising vertical pipe. Is the valve meant to hold back a head of water to protect other components upstream of it? Is the valve spring and seal of the correct type and strength to ensure this will happen?
In essence, this simple device is more important than you might have thought. It can make the difference between an efficient, safe pressurised steam and condensate system, or not.
This simple guide to Check Valves is not a substitute for expert advice. Make sure your system is operating correctly – contact us today.
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