Hydraulic Cylinder Piston Failure

[Dppm]

Hi Guys,

I work for a forklift truck manufacturer. We are using a hydraulic spring cylinder to apply a park brake. When the piston side of the cylinder is pressurised the park brake is released, and when pressure is removed, the spring retracts the cylinder, pulling the park brake cables to apply a drum brake.

The problem is that we are seeing failures with the piston inside the cylinder. The front flange of the piston, in front of the seal is bending and shearing off.

We considered that is may be due to the dieseling effect but there are no signs of burning on the seal. It may be a massive pressure spike, but we don't know what could cause such a spike? The cylinder is rated for 200 bar so the actual pressure required to cause the failure must be much higher. We measured the pressures and have seen it top out at around 205 bar. Any ideas what could be causing this to happen?

P.S. See attached image showing the face - marked in red - that is failing.

Thanks in advance.

 

[LittleInch]

Nothing attached which makes it difficult to comment.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[73lafuite]

Hello,
If you have a tight circuit when you open the brake: so a reed valve or something like that and your piston goes to a stop when you open the brake. So you should know that the pressure increases by 10bar when the temperature increases by 1°C. If the temperature increases by 20°C then the pressure increases by 200bar. If you already had 200bar then you arrive at 400bar.

 

[btrueblood]

Dieseling? Is this a pneumatic cylinder or hydraulic as you stated in your post?

Is the piston attached to a rod? If not, and the piston is not well guided with good rub rings, the canting moment of the spring may be causing the piston to cock (rotate) and rub on one side...