BLACKMER SNP1.25, Installation, Operation And Maintenance Instructions

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104-A00 Page 7/16
OPERATION
PUMP RELIEF VALVE
Hazardous pressure
can cause personal
injury or property
damage
An external bypass valve and/or an
internal relief valve MUST be installed in
the system to protect the pump from
excessive pressure.
Hazardous pressure
can cause personal
injury or property
damage
.
Incorrect bypass valve or internal relief
valve settings can cause pump
component failure, personal injury, and
property damage.
WARNING
Internal bypassing of liquid elevates liquid temperature.
Only use the internal relief valve for brief periods and at
differential pressures below 125 psi (8.6 bar). For
extended periods or higher pressures, internal bypass
port must be plugged and the liquid returned back to the
source.
1.25 – 2.5’ size SNP pumps are offered with an optional relief
valve assembly which is bolted onto the pump casing. The
valve may be used as an internal relief valve, or as an
external bypass, piped back to the storage tank (see Figure
4). Its purpose is to protect the pump or pumping system
from excessive pressure. The valve is not meant to be used
for prolonged recirculation. If the optional Blackmer relief
valve is not fitted, an external bypass valve MUST be fitted.
The 3“ SNP is fitted with an internal pressure relief valve that
bypasses internally back to the suction side of the pump.
When pumping highly volatile liquids under a high suction lift,
and cavitation or starving of the pump exists, partial closing
of the discharge valve will result in excessive noise in the
relief valve. Plumbing the relief valve so flow is directed back
to the storage tank or adding an external back-to-tank bypass
valve is recommended when operating under these
conditions.
Figure 4 – Relief Valve
RELIEF VALVE SETTING AND ADJUSTMENT
The relief valve pressure setting is marked on a metal tag
attached to the valve cover. Set the relief valve at least 15 -
20 psi (1.0 - 1.4 Bar) higher than the operating pressure, or
the external bypass valve setting (if equipped).
Hazardous pressure
can cause personal
injury or property
damage
Incorrect settings of the pressure relief
valve can cause pump component
failure, personal injury, and property
damage.
Hazardous or toxic
fluids can cause
serious injury.
Relief valve cap is exposed to pumpage
and will contain some fluid
DO NOT remove the R /V Cap OR adjust the relief valve
pressure setting while the pump is in operation.
1. To INCREASE the pressure setting, remove the relief
valve cap (1), loosen the locknut (3), and turn the
adjusting screw
inwar d, or clockwise. Replace the valve
cap.
2. To DECREASE the pressure settin g, remove the relief
valve cap (1), loosen the locknut (3), and turn the
adjusting screw
outwar d, or counterclockwise. Replace
the valve cap.
Refer to the individual Blackmer pump parts lists for various
spring pressure ranges. Unless specified otherwise, pumps
are supplied from the factory with the relief valve adjusted to
the mid-point of the spring range.