Check Valve Installation and Benefits

Check Valve Installation and Benefits

A check valve is a type of valve that allows fluids to flow in one direction but closes automatically to prevent flow in the opposite direction (backflow). Check valves are used in a wide variety of locations, but the focus of the discussion in this tutorial will be the installation of check valves at the steam trap outlet side.

If you are looking for more details, kindly visit our website.

Questions are often asked about the need and purpose of check valves, such as:

• Is it always necessary to install a check valve downstream of a steam trap?
• Does installation of a check valve prevent water hammer?

Let’s discuss these two points in detail.

Is it always necessary to install a check valve downstream of a steam trap?

Check valves become indispensable if there is a risk of condensate backflow. For instance, when a trap discharges into a common condensate collection line, there's a potential risk of backflow from condensate discharged from other traps. Therefore, to prevent this, a check valve should be installed as a rule. Preventing this backflow is crucial as it can reduce process heating efficiency and damage steam traps. Conversely, when there’s a single downward sloping pipe which isn't submerged at any point, the risk of backflow is minimal, making a check valve unnecessary.

Single Dedicated Line

If the trap uses gravity to drain through a downward sloping dedicated line that releases to the atmosphere without being submerged, the risk of backflow is almost null, and thus, installing a check valve is generally unnecessary.

Note: Exchange circumstances like piping configuration after the steam trap can lead to backflow, especially in the open lines if the equipment switches to vacuum or positive pressure due to a too-small vent or pipe rise causing unwanted return line pressure. In these cases, installing a check valve can be helpful.

Common Collection Line

When the trap outlet piping is connected to a common condensate collection line, condensate discharged from operating equipment may backflow into equipment that is out of service unless a check valve is installed at the trap's outlet.

If a check valve is installed, even if the trap's outlet piping is connected to a common collection line, the condensate discharged from operating equipment will not backflow into equipment that is out of service. Hence, installing a check valve assures no interruption in equipment functionality.

Does installation of a check valve prevent water hammer?

Different mechanisms generate water hammer. A principal cause of it in condensate recovery lines is condensate flowing back down in vertical rises. Installing a check valve at these points effectively prevents water hammer caused by backflow.

Water hammer caused by condensate backflow in vertical rises of condensate recovery lines

If the condensate discharge piping on a pump with intermittent operation (such as the TLV PowerTrap® series or a motorized pump with ON-OFF control) has a long horizontal run followed by a vertical rise, any condensate that falls back down the vertical rise becomes backflow. This backflow may collide with newly discharged condensate, causing water hammer. Similarly, in scenarios where a PowerTrap® discharges high-temperature condensate, a combination of flash steam and backflow could lead to water hammer.

Installing a check valve at critical points within the system, for example, at the beginning of a vertical rise, can help prevent water hammer.

Check valves can also help prevent water hammer caused by a pulsating flow of low-temperature condensate in condensate transport piping.

For more information on water hammer, please visit the water hammer tutorial.

Check Valve Restrictions

When high pressure hot condensate gets discharged through a steam trap to lower pressure, flash steam is generated. If this flash steam flows into a return line containing sub-cooled condensate at a much lower temperature, an instant collapse (condensing) of the flash steam will occur as it gives off its latent heat to the condensate, potentially causing water hammer. In such a situation, installing a check valve won't be effective.

Check valves prevent backflow but not back pressure. Discharging low pressure condensate into a higher pressure line is impossible. Even if a check valve is installed after a steam trap, condensate will not flow if the pressure upstream of the trap is lower than the downstream (return) side.

Furthermore, if a check valve is installed at the outlet of a trap operating under a markedly large differential pressure, the check valve itself becomes a resistance point; therefore, careful calculation of the pressure drop is necessary.

For more details, please visit BSTV.

Contact us to discuss your requirements of pipeline check valve manufacturer. Our experienced sales team can help you identify the options that best suit your needs.

Additional reading:
MOOG Patented Cover Plate & Belleville Washer