Industry / Machine
Shearing machine (sheet-metal cutter)
Maker / Model
Aizawa Tekkosho ADH625
Serial No.
20E08
Years in service
Approx. 20 years
Hydraulic oil
Grade No. 42 / 57 L

The Problem & Background

The customer operates a shearing machine (sheet-metal cutter, Aizawa Tekkosho ADH625) that has been running for roughly 20 years. Over the years, an oil leak had developed from its horizontally mounted hydraulic cylinder.

"We want to stop the oil leak from the cylinder" was the request, but the fundamental fix — replacing the oil seal — came with serious obstacles:

  • The oil seal is not a standard part — a matching seal has to be sourced or custom-made.
  • Replacement costs at least 100,000 yen — on top of parts, the teardown and reassembly labor is significant.
  • The cylinder has minor scoring, so the exact leak point can't be pinpointed — it is hard to determine precisely where the oil is escaping.
Horizontal hydraulic cylinder where the oil leak occurred
The horizontal hydraulic cylinder where the leak occurred (paper placed underneath to check for drips)

Product Adopted: "Hydraulic Seal" — Just Add It to the Oil

The solution was "Hydraulic Seal (RP-61821)", a hydraulic-oil leak stopper and additive. There is no need to disassemble the cylinder or pump: you simply add it to the oil tank and let it circulate during normal operation — a field-completable repair.

It penetrates seals and O-rings that have hardened and shrunk with age, restoring flexibility and elasticity, and forms a polymer oil film over fine scratches on metal surfaces to seal the leak path. That makes it well suited to exactly this kind of case — where the leak point can't be identified and the seal is a costly custom part.

Adding Hydraulic Seal to the hydraulic oil tank
Adding Hydraulic Seal to the hydraulic oil tank

Application & Progress

Here is how the leak responded, from application to stopping:

  1. 16:15Added 210 ml of Hydraulic Seal (3%) to the hydraulic oil tank.
  2. 16:16–16:31Ran for about 15 minutes. Oil began to seep, and 3 drops of leakage were observed over the 15 minutes.
  3. 16:35–16:45After wiping away the leak, ran for another 10 minutes. The seepage was noticeably reduced, but the oil contained air bubbles and only 1 drop leaked.
  4. 16:48Final check. After cycling the machine a few more times, a slight trace of seepage remained but the leak had stopped.

Analysis

Because this cylinder is mounted horizontally, the oil film does not form evenly and air is easily drawn in from the upper side. As a result, the oil may have contained air bubbles during the work.

In addition, a shearing machine is not normally run continuously at high speed. The continuous operation this time may also have contributed to the bubbles.