Blackmer 1” Pump Bypass The Blackmer 1” cylinder filling pumps feature a dual purpose built-in bypass valve. The valve is designed to provide both the back-to-tank bypass function and the emergency internal relief function. For most applications, no external bypass valve is required for pump installation. This internal valve arrangement has one, sometimes critical, shortcoming. Because the bypass is 100% closed while the pump is off, there is no provision for the removal of the inevitable vapor formation in the pump housing and ancillary piping. At times, this makes liquid transfer and filling impossible without blowing the filling hose down before starting the pump to attain a solid stream of liquid for the pump. Valve A is an internal valve that is normally closed while the pump is off. Opening this valve and allowing sufficient time before starting the pump may eliminate most of the trapped vapor if the inlet piping is sloped upward to the tank. Valve B is the hose end valve that is always closed while the pump is off. The practice of opening this valve to blow off the entrapped vapor to atmosphere is hazardous and does not resolve the vapor problem.
Valve C is the internal bypass valve which is closed 100% while the pump is off. This valve only opens after the pump set pressure is exceeded.
Bypass To Storage
A
Adding an external bypass with internal bleed orifice at “X”, will allow the liquid to “lift” the vapor out of the pump as it forms. New bypasses have bleed orifices as standard.
X C
Inlet
B
Discharge
Normal Operation
Back-to-Tank Bypassing
Pressure Relief
Valve is completely closed during normal operation with discharge line open.
Discharge pressure exceeding the valve setting opens valve to second stage, returning all or part of pump flow back to supply tank.
If back-to tank line is closed, valve opens to third stage, passing flow back to inlet side of pump.
881 HERSEY STREET ST. PAUL, MN 55114 PHONE (651) 646-1177 FAX (651) 646-1676
IN MINNESOTA 1-800-652-9072 OUT-OF-STATE 1-800-328-9222