Trinity Highway INGAL SS180 M, Assembly Manual

Page: 34 / 65

trinityhighway.com 33 Revision A November 2019
Counterbalance Valve
1. Purpose
The counterbalance valve allows free flow of hydraulic oil into and out of the cylinder but blocks
the flow when there is no pump pressure. The counterbalance valve locks the system when
the pump is not running.
Caution:
When the system is stopped at an intermediate angle, there will be
pressure on the oil in the hoses between the counterbalance valve and cylinder.
This pressure is supporting the load of the folding bay. ALWAYS make sure the
TMA is completely folded or unfolded before loosening a hose fitting or servicing
any check valve. This will minimize the chance of injury from an uncontrolled falling
load or spray of high-pressure oil. Never stand underneath the TMA when
performing any service or component check.
2. Repairing Counterbalance Valve
A. Symptoms
If the TMA exhibits a slow drifting of the folding bay when the pump is not running, one of
the following may be true:
1) The counterbalance valve has become blocked by foreign debris in the oil (hydraulic)
line.
2) The piston ring seal inside the cylinder has been compromised.
B. Repair procedure
1) Blocked Cartridge
a. Ensure the system is completely folded or unfolded.
b. Remove the Cartridge from the valve body, being cautious of oil spray from
residual pressure in the system.
c. Clean the Cartridge using compressed air, making sure to direct the air away from
anyone’s face. Avoid breathing the oil mist that this process may create.
d. Reinsert the Cartridge as they were before disassembly.
2) Piston ring seal
a. Refer to the following section on the Hydraulic Cylinder.
Important:
If the counterbalance valve has failed in some other way, do not
attempt to repair it. Replace it with a new valve by contacting Trinity Highway
Customer Service Department (p. 3).