A steady pressure gauge can show acceptable operation while short pressure peaks occur when a valve shifts or a cylinder stops. Those peaks can affect hoses, seals, mountings and the power unit. They should be investigated at the actual load and speed, not guessed from pump relief settings.
A gauge needle is too slow for some events
A cylinder may run at a steady pressure and still see a short peak when a directional valve shifts, an end stop is reached or a load changes direction. A mechanical gauge can average or miss a fast event. A rated electronic transducer with suitable sampling and an agreed test procedure can reveal the pressure-time trace. The sensor must be connected at the relevant location: a pump-outlet trace may differ from pressure trapped at a cylinder port.
Parker’s hydraulic cylinder application guidance calls for checking forces, speed and cushioning together; its filter handbook also distinguishes transient from average flow when sizing components. During commissioning, place rated sensors at relevant ports and record pressure with enough time resolution for the switching event. Correlate the trace with command, cylinder position, load and oil temperature. Review any peak against the pressure rating of every affected component and the approved circuit. Test planning and sensor installation belong to qualified personnel because changing a port connection can create a hazardous leak.
Tie the trace to machine events
Record valve command, position or limit-switch state, load and oil temperature alongside both cylinder-port pressures. Then the engineer can identify whether a peak occurs at acceleration, deceleration, cushion engagement or a sudden structural contact. Compare the observed maximum and duration with ratings for the cylinder, hoses, fittings, valves and sensors. A relief setting is only one part of that review, because a closed valve or an overrunning load can create a local pressure condition not visible at the pump.
A gate-stop trace
A gate cylinder reaches its upper limit and the controller removes the open command. A slow gauge shows an ordinary operating pressure, yet a fast transducer at the cylinder port records a sharp, short peak at the same moment the limit switch changes state. That correlation points toward valve timing or a mechanical stop event rather than a continuously overloaded pump. Repeat the test at the agreed water-level and load cases, then review the peak against local component ratings. The trace should be saved with the acceptance record so future maintenance can distinguish an original commissioning behavior from a new fault.
Turn the test into an acceptance record
Choose the worst credible operating states in advance: empty and loaded moves, both directions, start and stop, and any emergency stop required by the project. Use a sampling rate that resolves the switching event and calibrate the sensors. Record the raw trace and the approved acceptance limits, rather than only writing “no abnormal pressure.” If a peak exceeds a limit, investigate valve timing, cushioning, line restriction and structural stops before changing a component rating by assumption.
Checks to put on the drawing or test plan
- Capture traces at pump outlet and both cylinder ports for critical moves.
- Repeat the test with representative load and oil temperature.
- Compare measured peaks with component and connection ratings.
Failure mode to avoid: A relief-valve setting alone does not prove that every remote chamber remains below its rating during deceleration.
Information to request before approval
- Operating sequence and expected load cases.
- Schematic with sensor and test-point positions.
- Component pressure ratings and test acceptance criteria.
For a related explanation, see pressure test point placement.
Referencias técnicas: Parker Application Engineering Guide; Parker Handbook of Hydraulic Filtration. The cited manuals and product data describe their makers’ equipment; this article is independent engineering guidance and does not assign their ratings to Yongjian products.