Q: What are the most common things apart from pressure or speed that can cause a pump to fail?
A: The most common things that cause a pump to fail fall into three categories; Cavitation, Contamination, and Heat.
Cavitation: This is caused by a lack of oil flowing into the inlet port. It will damage the pump, and reduce flow. If you see foamy oil, it is a good indication of cavitation. Increasing the size of the inlet line or reducing flow can help with cavitation problems. Removing any elbows, bends, or filters on the inlet line can also help. Lastly, making sure that the oil reservoir is above the pump may also be beneficial.
Contamination: Contamination will not only cause damage to the pump, but may also plug valves, reliefs, etc. in the system. It is important to have the proper filtration in the system, including changing filters regularly.
Heat: Any Hydraulic system will generate heat. It is important to deal with that heat so that the oil temperature does not rise high enough to cause damage to seals, valves, etc. Having a properly sized oil reservoir (or oil cooler if necessary) is important in order to avoid excessive heat buildup in the system.
Lastly, make sure to refer to your manual for the proper pressure/speed limits. Exceeding those limits will damage a pump, and cause it to fail prematurely.