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Cast Steel Stop Check Valves


Stop Check Valves are as essential to safe operation of a boiler plant as safety valves or other safety devices attached to the boiler. The valves are intended to perform four important functions in boiler steam piping.


First: to act as an automatic non-return valve by preventing a backflow of steam from the main steam header to the boiler.


Second: to assist in cutting out a boiler, when ceasing to fire. In this case, the disc automatically closes and prevents header pressure from entering the boiler.


Third: To assist in bringing a boiler into service after a shutdown. This operation requires considerable care when performed manually, but is accomplished automatically by a stop check valve, without pressure fluctuations or disturbance of the water level.


Fourth: To act as a "safety first" valve by preventing backflow of steam from the header or for shutdown for inspection or repairs, should an attendant accidently open the valve.


When more than one boiler is connected to the main steam header, a stop check valve should be installed in the pipeline between each boiler and the header.


The valve should always be placed so that the pressure in the boiler is under the disc. Straightway valves may be used in horizontal or vertical lines for upward flow. Angle valves may be used for upward horizontal or horizontal downward flow.


Notes


Cylindrical-Shaped Disc is the only moving part. It is especially designed to produce maximum lift at minimum velocities. There are no wing guides to cause "spinning" with resultant rapid wear.


Long Throttling Lip on the disc retards flow when seating position is approached. Disc chattering is prevented, and wiredrawing of seating surfaces is reduced.


Removable Liner guides the disc throughout the full travel. Being entirely independent of the body, it is not subject to distortion by expansion strains.


Piston Ring adds to dashpot's ability to avoid rapid disc movement and where pulsations are extremely severe, two piston rings can be installed.


Easy Regrinding Tap Bosses on top of the disc permit inserting nipples or eye bolts to facilitate quick removal of the disc for grinding.


Large Port Areas in the liner produce only a minimum of pressure drop through the valve and assure unrestricted movement of the disc.