Page 149 - ParkerQuickCouplingCatalog38002010

Quick Coupling Division
8145 Lewis Road • Minneapolis, MN 55427
www.parker.com/quickcouplings E-2
Valves
E
Valves
Introduction
Multiple Hydraulic System Applications
Parker Check Valves are unidirectional flow control devices
used primarily in hydraulic systems to eliminate potential
damage caused by fluid back pressure. Offered in many con-
figurations, Parker can satisfy most hydraulic system applica-
tions. Parker's in-line style check valves are available in a
variety of sizes, pressure ratings, flow capacities and
crack pressures.
H1, HM1 and PV Series Pressure / Vacuum Relief Valves are
used to create and maintain a positive pressure in hydraulic
tanks and reservoirs. These pressurized reservoir valves
provide the following benefits:
• Prevents pump cavitation by assuring a positive
supply of oil at the pump inlet
• Minimizes the tank breathing of outside, moist,
contaminated air
• Filters all incoming air
As oil is drawn from the reservoir and pumped to the circuit, a
vacuum is created in the reservoir. The vacuum relief valve
opens to allow filtered air to enter. As oil is pumped back into
the reservoir, air pressure builds. Additionally, as the oil
heats, the pressure inside the reservoir increases. When the
pressure exceeds the relief valve setting, the excess pressure
is vented to atmosphere. Normally, the pressure will fluctuate
between zero and the pressure relief setting without opening
either valve. This can significantly reduce the breathing of
outside air and minimize the chance for moisture and con-
tamination to enter.
TH Series Thermal Bypass Valves ensure efficient equipment
operation at any temperature. These valves are ideally suited
for hydrostatic drive circuits which require fast warm-up,
controlled fluid temperatures and low return line back
pressure. When installed in a return line of a hydraulic circuit
that utilizes an oil cooler, this valve will modulate fluid temper-
ature by either shifting return line flow through the cooler, or
bypassing directly to the reservoir. An integral pressure relief
function automatically releases excess pressure to the
reservoir if the cooler becomes restricted and the inlet
pressure becomes excessive.