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This page is dedicated to providing you some common but commonly over looked facts about the fluid power equipment common to all industry. While not all problems are covered here, this will serve as a guild to basic troubleshooting and system analysis.
Common problems in today's hydraulic systems include but are not limited to: Filtration, faulty and worn seals, faulty and worn valves, faulty accumulators. We will examine each of these in more detail in the paragraphs to follow.
Filtration: Almost all hydraulic systems are equipped with some type of filtration system. Even the most primitive systems allow for filtration at some level. As you might expect the systems filtration is commonly overlooked when problems occur. As the system itself may be doing its job and not be the originator of problems, lack of proper maintenance could be causing the system to act in an abnormal way. Dirty filters or strainers could cause a system to act sluggishly, jerky, or not at all. Dirty filters, on the pressure side of a pumping unit, will normally go into a bypass mode at a predetermined differential pressure across the filter. While filters have this safety feature many suction strainers do not. Sluggish operation is usually not noticed on systems who's operating pressures are substantially higher than the bypass pressure. On systems who's operating pressures are close to the by-pass pressures of the filter, dirty filters could cause a reduction it total flow rate therefore allowing sluggish operation of the system. As all common hydraulic pumps are positive displacement internal slippage will allow for some change in output flow rate.
Jerky and delayed operation is another problem commonly associated with the lack of proper filtration. For many of the same reasons given for sluggish operation jerky operation can also be associated.
For a system to operate at normal efficiency an allow for proper movement of system valves proper filtration is a must. Close tolerance servo, proportional, and directional control valves will not allow for practical sizes greater than a predetermined number. Spools can become stuck in the valve body and not operate at all.
Bottom line here is "take care of your filtration system and it will take care of you".
Faulty or worn seals: Hydraulic problems can also exist in faulty or worn seals. This may or may not mean fluid on the floor. Fluid running out on the floor is obvious but abnormal operation with no leaking fluid is not so obvious. Many of today's valves, pumps, and operating mechanisms have internal seals that could become faulty and leak by with no external warning other than a system that does not operate properly.
For example, pumps have shaft seals that may be on the inlet side of the pump flow and may leak by. This will cause aeration of the system which will cause a noisy pump and jerky operating mechanisms with no fluid leakage because the low pressure area is on the inside of the pump. Linear actuators have piston seals on the inside of the piston that could leak by allowing fluid to flow to the other side of the actuator causing the actuator to move slower than usual but will show no external signs of fluid leakage.
Of course these are only a couple, among thousands, of scenarios that could take place. Proper analysis of system operation is dependent on your individual system.
Faulty accumulators: Another mechanism commonly associated with hydraulic systems are accumulators. While these systems are normally very reliable and provide years of trouble free service they can be the source of abnormal operation. The accumulator provides hydraulic fluid, under pressure, to the system for instantaneous operating requirements.
While there are many kinds of accumulators, of different types, most of them not working properly cause sluggish operation. Many industrial hydraulic systems do a specific function through a given cycle time. As accumulators fail and do not work properly these cycle times will increase. The system may perform all of the normal functions but not in the time allotted. This could be due to a low charge, improper charging techniques, leaking piston seals, and a variety of other problems.
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