Locate and identify the check valve on the machine. It may be necessary to follow a hydraulic hose from a pump or control valve to locate the check valve. Identify the direction of flow of the valve. The valve will have an "A" and a "B" port or an arrow showing the direction of flow. Determine from the machine drawings the direction of flow of the hydraulic fluid. Ensure the valve is installed in the correct direction of the flow.
Determine from the machine drawings the working pressure of the system. Remove the hydraulic hose at the inlet or "A" side of the check valve. Attach a 5,000 psi gauge using the correct adapter to the inlet hose of the valve. Cap off the exposed "A" port of the valve using the correct JIC cap or plug. Start the equipment and activate the circuit on which the check valve is located. Compare the reading from the gauge to the machine drawings to determine if the circuit has the correct working pressure. If the working pressure is not correct, then repairs must be made before proceeding with the tests.
Remove the gauge and adapter and reconnect the hose to the "A" or inlet side of the check valve. Remove the "B" or outlet side of the check valve hydraulic hose. Attach a 5,000 psi gauge to the "B" or outlet side of the check valve using the correct adapter. Plug the return line on the "B" side of the valve with the correct JIC plug. Start the equipment and activate the circuit on which the check valve is located. Read the gauge and compare the reading to the machine drawings. If the pressure reading is the same as the reading from Step 2 or the machine drawings, then the check valve is unrestricted in the direction of flow. If the reading is significantly less than the reading from Step 2 or close to zero, then the check valve is either bad or installed backward.
Remove the pressure gauge and adapter from the "B" or outlet side of the check valve. Remove the valve from the machine and reinstall it in a reversed direction. Attach the inlet or pressure hose to the "B" or outlet side of the check valve. Install a 5,000 psi gauge to the "A" or inlet side of the check valve using the correct adapter. Plug the return hose on the "B" side of the valve using the correct JIC plug. Start the equipment and activate the control circuit. The pressure reading should be zero if the check valve is operating correctly.
Remove all plugs, caps and adapters from the equipment. Install the check valve by attaching the pressure hose to the "A" or inlet side of the check valve. Attach the return hose to the "B" or outlet side of the check valve. Start the equipment and check for leaks.
Follow Section 1 to determine if the basic functioning of the pilot operated check valve is working. Determine from the machine drawings the operating pressure of the pilot control line. Locate the pilot control line. Some machines have a manifold with multiple valves and hoses. The pilot hose may be attached to this manifold and not the valve. It may be necessary to find the hose by following the line from another component.
Remove the pilot control line at the fitting and attach a 5,000 psi gauge using the correct adapter. Start the equipment and activate the pilot control circuit. Compare the reading of the gauge to the machine drawings. If the gauge reads zero or is significantly lower than the operating pressure, then there is a problem with the control circuit that must be repaired before testing can continue.
Remove the gauge and adapter from the pilot circuit and reattach the pilot control hose. Remove the "A" or inlet hose of the check valve and cap the hose off using the correct JIC fitting. Attach a 5,000 psi gauge to the "A" or inlet side of the check valve using the correct adapters. Start the equipment and activate the pilot control circuit. The valve operates correctly when the pilot control circuit is activated and the check ball is released from its seat allowing flow from the "B" to the "A" port. The pressure reading on the gauge will be determined by the reverse flow pressure of the machine, often much less than the operating pressure.
Remove all plugs, caps or adapters. Reconnect all hoses to the correct ports. Start the equipment and check for leaks after all repairs have been completed.