Feed Check Valve and Steam Stop Valve
Feed Check Valve is used to supply high pressure feed water to boiler.Steam Stop Valve regulates the steam supply to use.
Steam Stop Valve
The steam stop valve is located on the highest part of the steam space. It regulates the steam supply to use. The steam stop valve can be operated manually or automatically.
Figure : Steam Stop Valve
Feed Check Valve
- The feed check valve is fitted to the boiler, slightly below the working level in the boiler. It is used to supply high pressure feed water to boiler. It also prevents the returning of feed water from the boiler if feed pump fails to work.
- The feed check valve is located in the feed line near the boiler, between the feedwater heater and the feed stop valve. It is a one-way valve, and one of its purposes is to prevent the feedwater from returning through the feed line once it has entered the boiler.
- The cross-sectional view is of a simple feed check valve of a type used aboard ship.
- The body (G) of the valve is made of bronze or cast steel. The feedwater enters the valve through the feed line from the feedwater heater at (A) end flows downward and then turns up against the bottom of the movable disc (B) which acts as a plug to close the opening. When the pressure of the entering feedwater against the bottom of the disc becomes greater than the pressure within the boiler pushing downward on the top, the disc lifts.
- This leaves an opening through which the feedwater flows to discharge at (D) to the stop valve and boiler.
- When the incoming pressure drops below the boiler pressure, the pressure on the top of the disc becomes greater, causing the disc to drop, close the opening and prevent the water in the boiler from flowing backwards into the feed line.
- The bottom end of the valve stem (C), which is threaded in the valve yoke (F), is not attached to the disc (B). When the valve wheel (E) is turned clockwise (to the right) the stem screws downward until the bottom end of the valve stem is against the top of the disc. With the stem in this position the disc cannot be raised by the incoming water pressure, due to the valve stem holding it on its seat. This is closed position; no water can enter boiler.