Many of our customers rely on the use of steam as a source of energy in their industrial chemical processes. While steam is ideal for powering countless industrial processes, the resulting condensate needs to be removed from the steam line as quickly as possible after its formation. Otherwise, lingering condensate can cause water hammer and other problems. Allowing it to pool inside the piping where a pressure drop could cause it to flash (the abrupt vaporization of a liquid). This can result in cavitation, erosion, excessive noise and valve failure.
Steam traps are constructed within the system in order to contain steam and remove the condensate as it is formed. When these two primary goals of a steam condensate system are done correctly, gravity will be your friend, and the condensate will flow downhill.
The Check Valve’s Role
Once removed, the condensate is usually captured and recycled back into the system. A properly selected and installed quick-closing check valve is essential in order to eliminate reverse flow and minimize the effects of flashing.
Check valves, which control the flow of fluid (gas or liquid) in one direction, are opened by the velocity of the forward-moving fluid. Depending on the type of check valve, they close when the flow slows, stops, or reverses, preventing the fluid from flowing in the reverse direction. Check this out if you’d like a run-down on the different types of check valves.
Of the various types of check valves, silent check valves are the ones we want to talk about when it comes to steam condensate systems. Silent check valves use a spring-loaded disc that closes when the flow velocity reaches zero and before it reverses. This eliminates the noise and vibration caused by swing check valves when the reverse flow slams them closed.
Consulting an expert when installing a steam trap is recommended, and it will help to eliminate any potential problems. Here are some tips for using check valves in steam condensate systems:
Check valves should be installed to prevent backflow and siphoning of condensate from the return main equipment.
Gravity rules. Condensate needs to be able to flow downhill from the process to the steam trap.
Verify that the pressure ratings of the valves being used are sufficient for the pressure that will be produced by the system.
Installing strainers that will collect any dirt or scale will extend the life of the check valves.
An additional check valve may also be installed at the lowest temperature point of a system as a vacuum breaker if needed. When done correctly, it will open to the air rather than the return line within the system so as to not pull in any condensate.
The check valve should be installed after the steam trap.
Correct sizing of check valves is essential for steam service. Over-sizing increases the risk of erosion. It’s important to know the pressure, temperature and expected flow rate when sizing silent check valves for steam condensate systems.