Graco 3A1334E Manual De Usuario

The pump operation is similar to most double acting 
reciprocating pumps. The pump only comes to a com-
plete stop on the up stroke. The pump will stroke 
through on the down stroke due to the inlet check relief 
passage. 

Excess pressure due to downstream thermal expansion 
causes the air motor/pump to run backwards (down-
ward). Fluid pressure is relieved through the inlet check 
relief passage as the pump piston moves downward. Air 
pressure is simultaneously relieved through the air inlet 
passage. The pump piston moves downward exposing 
the pump cylinder relief passage at the bottom of the 
stroke. Additional excess pressure is then relieved 
through both the inlet check relief passage and the 
pump cylinder relief passage.

Pressure is relieved at the pump through the pump inlet 
relief passage. The pump will not change over on the 
bottom of the stroke as a result of relieving excess pres-
sure due to the positioning of the pump cylinder groove 
with respect to the air motor pilot valve. 

NOTE: 

•

The air supply does not have to be turned off to 
enable thermal relief activation.

•

The Thermal Induced Pressure Relief design fea-
ture of the pump will cause the pump to dive on the 
downstroke when a dispensing valve is closed. 

Fluids subjected to heat in confined spaces, including 
hoses, can create a rise in pressure due to the 
thermal expansion. Over-pressurization can result in 
equipment rupture and serious injury.

Oil pumps have a built-in, thermal induced, pressure 
relief as shown in F

. 4. To ensure system pressure 

will automatically bleed excess thermal induced 
system pressure through the pump and back to the 
oil reservoir:

•

Always use a relieving air pressure regulator to 
allow the pump/motor to run backwards. The regu-
lator bleeds excess air pressure.

•

There should not be any obstructions between air 
inlet of pump and regulator.

•

There should not be any obstructions between the 
downstream plumbing and pump outlet such as 
closed ball valves or check valves.

•

There should not be any obstructions between the 
pump inlet and fluid container such as closed ball 
valves or check valves.

•

Only use Graco designed suction tubes for in-drum 
or in-tank applications.

•

Only use Graco designed suction tubes with a 
built-in relief device for wall mount applications. 

•

Always use an inlet screen to prevent debris from 
plugging relief passages from entering the pump. 

- Do not operate the pump with out an inlet screen. 

•

Periodically inspect the inlet screen for plugging. 
Graco recommends inspecting the inlet screen 
every time the container is changed out.

. 4 a = Pump cylinder relief passage 

b = Inlet check relief passage 

a

b