By Anzar Hasan, chief inspector
Hydraulic presses are commonly used for forging, clinching, moulding, blanking, punching, deep drawing and metal forming operations. There are different types of such presses depending on the application and a broad spectrum of capacity ranges beginning from small presses to several thousand tons of compressive force.
At a recent inspection visit by a BPC Risk Assessment Engineer at a steel plant which manufactures steel balls for ball and sag mills, he made some serious discoveries.
The mill was shut down due to business reasons. There were two hydraulic presses of about 350 tons capacity that were idle but appeared in good condition on visual inspection. Due to changes in plant personnel, not much information was initially provided on the condition of the presses. Also, there was no nameplate on either of the presses. Although the estimated replacement value of the presses was around $500K each, the BI could exceed $1.0M. It was important to probe into the maintenance and testing of the presses. On consistent request, the following was discovered:
One press was built in the UK in 1952. The other press was built in Russia around 1950. The UK built press had severe cracks in the bed, of which some were so large that the maintenance foreman stated they were visible by naked eye. One of the cracks had progressively extended almost around the circumference in December 2014 and was repaired by welding. (Please note that cast iron cannot be welded for safe operation.)
The Russian press had severe oil leaks from the seals. The seals were replaced but the leakage continued to the extent that the oil was collected in a container when the press was in operation and put back into the reservoir of the press. It was reported that the bed of the crack was distorted (concave formation) and could not be repaired.
Both the presses had greatly exceeded their useful life and were not repairable. Additionally, the parts for the presses were no longer available. A major cracking/breaking of either press would have resulted in catastrophic failure and extended damage to adjacent located equipment as well as extended business loss for several months. Both of the presses were continuously operated in the condition described.
At the closing conference, the recommendation to management was to take both presses out of service and replace. The national engineering manager stated that the capital budget for replacement of the presses had not been approved by corporate management for over two years.
Based on our findings, XLCatlin proceeded to suspend insurance on the presses before getting hit with a large loss. Two days later we received an email from the national engineering manager that corporate approved the budget for replacement of the presses and thanked us for the loss prevention and assistance provided by BPC.
It is critical to evaluate the operation, maintenance and testing of hydraulic presses irrespective of the size as the associated business loss could be very large.
The following are some areas that should be evaluated:
- Non-destructive testing of stress areas of the presses. Highly stressed press parts can create stress risers. Loss experience demonstrates cracking frequently originates at the stress riser
- Make it a practice to review NDT reports and complete repairs
- Review spare components available at the plant or through manufacturer and suppliers
- Pay close attention to presses that could be vintage and have exceeded their useful life indicative with outages, maintenance and repair history
- Periodic oil sampling and spectrometric analysis
- Alignment schedule of the presses.
- Cast iron parts cannot be successfully weld repaired. It is sometimes possible to affect a temporary cold mechanical repair of cast iron. If any repairs are carried out involving welding or cold repairs, the repair procedures should be closely examined