Confidential – Major Marine Equipment OEM

Leakage in hydraulic valve block

A major marine equipment OEM experienced recurring leakage from hydraulic valve blocks during classification and FAT testing. After earlier investigations had not isolated the failure mechanism, HydTec reproduced the fault under controlled conditions, conducted a systematic root cause analysis, and verified a reliable, repeatable corrective action.

Test verification Repair Troubleshooting Root cause investigation

Challenge

Recurring leakage appeared during classification and FAT testing, particularly when the hydraulic blocks reached elevated operating temperatures. Since earlier inspections had not identified a clear defect, the fault needed to be reproduced under controlled conditions before its underlying cause could be established.

Delivery

HydTec designed and built a dedicated test setup, reproduced the leakage and conducted a structured investigation covering sealing surfaces, threaded holes, valve interfaces, dimensional accuracy, surface condition and the integrity of the base material. A corrective machining method was subsequently developed and verified through repeated pressure testing.

Results

The root cause was traced to oil migration beneath the protective surface coating. Surface-grinding the affected blocks to remove the coating restored leak-tight performance. The same method was subsequently applied to several additional blocks and confirmed through repeatable testing.

GO TO RESULTS

V14 manifold hydraulic valve block with mounted solenoid valve, pressure sensors, and fittings, packaged in bubble wrap with a manufacturer nameplate

Initiation

Workbench setup showing hydraulic manifold blocks alongside surface roughness testing equipment and calibration documentation.

Initial assessment

The customer had experienced recurring leakage from hydraulic valve blocks during FAT and classification testing. Earlier inspections had not established a clear cause, and the leakage became most evident when the blocks reached elevated operating temperatures.

HydTec was engaged as an independent hydraulic specialist to investigate the issue. One of the affected blocks was supplied for examination, and the work began by developing a test setup capable of reproducing the reported symptoms under controlled workshop conditions.

Communication

HydTec maintained continuous technical communication with the customer and the other relevant technical stakeholders throughout the assignment. Findings, test results, observations and proposed corrective actions were discussed regularly by telephone and through digital meetings.

This close dialogue allowed the involved parties to follow the investigation, understand the significance of each test and agree on the next steps as potential causes were systematically evaluated and eliminated.

Process

Industrial hydraulic control valve assembly with metal cylinders, hoses, wiring, and a handheld diagnostic tool on a workbench.

Design & Engineering

As no suitable test arrangement was available, HydTec first designed and built a dedicated test bench capable of operating the hydraulic block under controlled pressure and temperature conditions.

The test setup made it possible to reproduce the leakage observed during the customer’s FAT and classification testing. Establishing a repeatable fault condition was essential before the root cause investigation could proceed.

Once the reported symptoms had been confirmed, HydTec developed a structured test programme covering the block’s sealing interfaces, threaded holes, valve components, machined bores, surface condition and base material.

Manufacturing

HydTec measured the surface roughness and polished the sealing surfaces to determine whether the surface finish affected the leakage. The threaded holes were pressure-tested to verify their integrity and exclude them as possible leakage paths.

The block was also examined for cracks, porosity and other material defects. Valves and O-rings were inspected for deformation, damage or dimensional deviations that could affect sealing performance.

The available 3D drawings were reviewed, and the relevant bores and machined interfaces were measured to confirm that the block had been manufactured within the required dimensions.

After the most likely mechanical, dimensional and sealing-related causes had been eliminated, attention turned to the protective surface coating. The affected surfaces were ground to remove the coating, after which the block was pressure-tested again.

The treated block remained leak-tight. The investigation concluded that hydraulic oil had migrated beneath the surface coating, creating a leakage path that was not visible during conventional inspection.

After eliminating the most likely mechanical and sealing-related causes, we decided to surface-grind the blocks to remove the electro-zinc coating. After this treatment, the blocks became leak-tight. The conclusion was that oil had migrated beneath the surface coating, even though this was not an obvious or expected failure mode.

A dark metal hydraulic manifold block with numerous threaded ports and a large central cartridge valve bore on top. Ports are labeled with codes such as TP-CP, TP-LP, TP-P, TP-CS, C-PSLP, C-PSCS, and V1.5–V1.7. The block rests on a blue ESD-safe mat in a workshop setting.

Results

Installation & commissioning

Following the first successful result, the same surface-grinding method was applied to several additional affected blocks. Each block was subsequently tested under controlled conditions to verify that the leakage had been eliminated before release.

The repeated results demonstrated that the corrective method could be applied consistently to blocks exhibiting the same symptoms.

Follow up & support

HydTec continued the technical dialogue during the follow-up phase and communicated the verified findings and corrective method to the customer.

The documented investigation and repeatable repair procedure now provide a practical basis for assessing and treating additional hydraulic blocks if similar symptoms occur in the future.

Leakage in hydraulic valve block