TSE DP20-4H, Owner'S Manual

Page: 44 / 242

High Pressure Relief Valve (HPRV) and charge check
All MP1 pumps are equipped with a combination high pressure relief and charge check valve. The high-
pressure relief function is a dissipative (with heat generation) pressure control valve for the purpose of
limiting excessive system pressures. The charge check function acts to replenish the low-pressure side of
the working loop with charge oil. Each side of the transmission loop has a dedicated HPRV valve that is
non-adjustable with a factory set pressure. When system pressure exceeds the factory setting of the
valve, oil is passed from the high pressure system loop, into the charge gallery, and into the low pressure
system loop via the charge check.
The pump order code allows for different pressure settings to be used at each system port. The system
pressure order code for pumps with only HPRV is a reflection of the HPRV setting.
HPRV´s are factory set at a low flow condition. Any application or operating condition which leads to
elevated HPRV flow will cause a pressure rise with flow above a valve setting. Consult factory for
application review. Excessive operation of the HPRV will generate heat in the closed loop and may cause
damage to the internal components of the pump.
P400353
High Pressure
Low Pressure
Bypass Function
The HPRV valve also provides a loop bypass function when each of the two HPRV internal hex plugs are
mechanically backed out 3 full turns. Engaging the bypass function mechanically connects both A & B
sides of the working loop to the common charge gallery. The bypass function allows a machine or load to
be moved without rotating the pump shaft or prime mover.
C
Caution
Excessive speeds and extended load/vehicle movement must be avoided. The load or vehicle should be
moved not more than 20 % of maximum speed and for a duration not exceeding 3 minutes. Damage to
drive motor(s) is possible. When the bypass function is no longer needed care should be taken to reseat
the HPRV internal hex plugs to the normal operating position.
Service Manual
MP1
Operation
10 | © Danfoss | July 2017 AX00000244en-US0103