Pressure Test in The Workshop: On-Site Record Of Propeller Cap Fin Hydrostatic Test

Inside the marine propeller workshop, the three-station hydrostatic test area is in a bustling state. Master Li, 35 years old, wearing anti-slip gloves, bends down to steadily fix the newly finished precision-machined cap fin on the test fixture table. The pointer of the digital pressure gauge in front of him has not yet moved, and a "pressure" test related to navigation safety is about to begin. As a key flow-guiding component of the propeller, the sealing performance and structural strength of the cap fin directly affect the propulsion efficiency, and the hydrostatic test is an indispensable checkpoint before leaving the factory.

"First check the gasket, then verify the test parameters," Master Li says while tightening the fixing bolts around the fixture one by one with a torque wrench. The rubber gasket fits tightly with the cap fin interface without any gaps. His young apprentice beside him has already connected the test pipeline to the water inlet of the cap fin, holding the process card to confirm the parameters: "Master, this batch of cap fins is suitable for 5,000-ton cargo ships. The test pressure is 1.2MPa, and the pressure holding time is 30 minutes. Is that correct?" Master Li nods and presses the start button.

The high-pressure water pump starts to operate, and water flows into the cap fin through the pipeline. The pointer of the digital pressure gauge rises slowly: 1.0MPa, 1.1MPa, 1.2MPa. When the value stabilizes at the standard line, Master Li quickly closes the water inlet valve and turns on the pressure holding switch. He takes out a high-intensity flashlight, approaches the welds and curved joints of the cap fin to inspect carefully, and wipes the interface with a tissue. "The biggest concern in hydrostatic testing is 'invisible leakage'-even a tiny wet mark on the tissue means the cap fin has to be sent back for rework," he says.

During the pressure holding period, the data from the workshop's temperature and humidity meter and pressure gauge are synchronized to the central control system in real time. Master Li records the values every 5 minutes. Master Wang at the adjacent station, who has just finished testing the previous batch, is marking the qualified cap fins with the test date and serial number using a special marker pen. "Last year, the pressure of a batch of cap fins dropped slightly at the 20th minute of pressure holding. After investigation, it was found to be caused by tiny sand holes during casting. Now the control has been tightened in every process," he explains.

Thirty minutes later, the pointer of the pressure gauge remains completely still. Master Li releases the pressure relief valve, and the water flows out smoothly. He takes off the cap fin, checks that there is no residual water stain on the inner wall, and signs his name on the process card. Sunlight filters through the workshop's skylight and falls on the metallic cap fins. These components, which have passed the "pressure" test, are about to be sent to the shipyard to be assembled with propellers, building the first line of defense for the safe navigation of ships. In the workshop, the next cap fin to be tested has been steadily placed on the fixture table, and the testing work continues in an orderly manner.