Nozzle Check valves which are also called axial flow check are very important for non-return fluid purpose with non-slamming and fast closing

characteristics. They are mostly installed downstream of rotating equipment to protect the expensive mechanical equipment from possible damages due to

back flow. Although they are costly option compared to other alternatives like swing and dual plate check valves but can save a lot through safe protection

of costly rotating equipment and lower pressure drop. These valves are widely used in different sectors of water and pump station and even in oil industry such as top site offshore

platforms, subsea, refineries, pipelines, LNG and petrochemical plants.

?Advantages and design considerations

?Eliminates Water Hammer:

short axial disk travel to the seat, spring assisted design in addition to low mass disk make nozzle check (Non slam check valves )as a fast-closing valve which is an advantage in critical lines with fast reversing flow. Fast closing response reduces the possibility of equipment damage due to back flow and provides good protection for expensive mechanical facilities. Low static pressure behind the disk

in venturi area makes a pressure differential over the disk causing easy opening of the disk as well.? The quick and close avoid the shock waves and pressure spikes associated with slamming shut.

Low pressure drop and high flow capacity

?High pressure drop means higher wearing and erosion in the valve as well as more expensive，while pumps or compressors selection to provide higher head and lower friction loss. The pressure drop for the valve is low and less than 0.1barg normally. Inaddition, smooth flow through the valve as a result of venturi effect associated with nozzle design (bore reduction) avoids flow turbulences, minimizes erosion problems, maximizes flow capacity as well as easy opening of the disk.

Non slamming

Although disk closing speed is fast, the disk closing action does not produce slamming against seat due to short stroke and spring assisted design which minimizes water hammer and valve slam in the liquid services. Water or liquid hammer is a possible operation problem in which a pressure wave is caused by the fluid service due to sudden closing or slamming of the valve. That can create noise, vibration and (Or) piping collapse due to additional piping loads. so normally the non slam check valves are also called silent check valves.