Today's topic also features heat, or more correctly - temperature and the effect is has on static pressure.
It's also another fascinating and instructive troubleshooting story, as told by one of our members, Joachim Renner:
"Our company supplied eight double-acting hydraulic cylinders for an auxiliary function on a tunnelling machine. The cylinders had the following dimensions:

Piston diameter 140 mm, Rod diameter 90 mm, Stroke 600 mm

During machine commissioning we got a complaint that none of the hydraulic cylinders were holding pressure.
All cylinders had been tested prior to delivery, and in spite of this it was plausible one cylinder had failed - but not all eight.
All the hydraulic cylinders were removed and returned to us. Each was pressure tested first.
And no defect was detected in any cylinder.

So we sent them back to our client - with test reports.
After a couple of days I got a call from a very unhappy customer. All of the hydraulic cylinders were still holding pressure.
What could I do?"

By Brendan Casey