The Spirax Sarco BCV31 is a pneumatically operated control valve for the blowdown of steam boilers. It is normally used with a controller as part of an automatic TDS control system, though it can also be used for other high pressure drop, low flowrate applications.
The flowrate is adjusted by limiting the spindle stroke to regulate the number of orifices that are uncovered.
The valve, which is specially designed to minimise seat erosion and ensure consistent tight shut-off, is supplied adjusted to its low flowrate setting of 10 mm.
It can be adjusted to give 15 mm stroke for medium flowrates, or to 20 mm stroke for high flowrates. The actuator has a mechanical stroke indicator and incorporates a rolling diaphragm.
A ¼ " BSP plug at the base of the valve may be removed to allow a sample cooler to be fitted (available from Spirax Sarco).
The BCV31 requires a regulated and filtered air supply (¼" NPT), which should be free of oil and water, and a solenoid valve, (available from Spirax Sarco).
The valve is spring loaded to the closed position (spring retract), and is also held closed by the boiler pressure. When the solenoid valve opens, air is admitted to the actuator causing the valve to open to the selected stroke.