Recently I have worked on a vessel where all mooring equipment was hydraulically powered and due age of the vessel we have encountered a lot of trouble with the system (pipe failure, pipe damage, hydraulic hoses and connection failure, pumps’ failures etc.). Apart from this, the vessel was equipped with hydraulically driven cargo cranes which gave us a lot of headache during cargo operation due their age, condition and lack of proper maintenance.
However, the majority of vessel engineers are not familiar with the correct techniques for maintaining hydraulic systems, which is despite the fact that improper maintenance of hydraulic systems is the leading cause of component and system failure. Two different aspects of concern make up the fundamental basis for performing appropriate maintenance on a hydraulic system. The first area is preventative maintenance, which is essential to the success of any maintenance program, regardless of whether it’s for hydraulics or any other piece of equipment for which we rely on its dependability. The second component is corrective maintenance, which, if it is not carried out according to the established protocols, can frequently result in the failure of additional hydraulic components.
As in any other occupational field, knowledge is power and every marine engineer must be proficient in understanding the basic principles of a hydraulic diagram, how is it working, the meaning of hydraulic symbols and the components application and function in the hydraulic system.
Unfortunately, most of the shipping companies don’t spend money for training their engineers in maintenance and troubleshooting of the hydraulic systems. Moreover, the schools and colleges teach their students only general stuff about hydraulic systems, hence the lack of maintenance and troubleshooting knowledge.
Troubleshooting a hydraulic system would take less time and cost less money if we concentrated on reducing the likelihood of system failure in the first place. Instead of selecting not to account for the possibility of hydraulic system failure as the usual, we routinely account for the possibility of such failure. Preventive maintenance of a hydraulic system is very basic and simple and if followed properly can eliminate most hydraulic component failure.
Here on this post I will describe the best maintenance practices for main components of hydraulic systems, practices based on my experience and knowledge which I hope that will help you to learn and understand the importance of these systems preventive maintenance.
The hydraulic reservoirs are used to store a volume of oil, dissipate heat from the fluid and remove contamination from the system. In the below video you can learn about their purpose.
As part of maintenance of the hydraulic reservoirs, I would like to emphasize that if any of the following conditions are met…
- System has been opened for major work
- Oil analysis states excessive contamination
- Hydraulic pump fails
…the best best practices are as follow:
- It is necessary to clean the region under and all around the reservoir in addition to the reservoir’s exterior.
- Remove the oil from the reservoir using a filter pump and place it in a fresh container that has never been used to store any other kind of fluid.
- Clean the insides of the reservoir by opening the reservoir and cleaning the reservoir with a “Lint Free” rag.
- After that, pour clean hydraulic fluid into the reservoir, and then drain the remaining fluid from the system.
For the reservoir air breather which has been mentioned in the above video, it is not recommended that a standard screen breather be utilized in an unhealthy or hazardous environment. Because of the possibility of introducing impurities into a hydraulic system, it is recommended to utilize a filtered air breather with a value of 10 micron.
As part of maintenance of the hydraulic reservoirs air breather, I would like to emphasize that the frequency of maintenance is preferred to be based on historical trending of oil samples rather than based on manufacturer’s recommendation.
The best practice is to remove and throw away the filter and never cleaned, washed and reused.
The hydraulic fluid filters are of a two types on a hydraulic system:
- pressure filter which comes in collapsible and non-collapsible type and where the latter is preferred.
- return filter which typically has a bypass, which will allow contaminated oil to bypass the filter before indicating the filter needs to be changed.
Same as hydraulic reservoirs air breather, as part of maintenance of the hydraulic filters, I would like to emphasize that the frequency of maintenance is preferred to be based on historical trending of oil samples rather than based on manufacturer’s recommendation and the best practices are as follow:
- Utilizing a cleaning solution and a set of clean rags, thoroughly scrub the filter housing or cover.
- Using clean hands, remove the old filter from the filter housing, then place the new filter inside the housing or screw it into place. NEVER allow your hand to touch a filter cartridge. Open the plastic bag and insert the filter without touching the filter with your hand.
With regard to the hydraulic pumps a marine engineers needs to know the type of pump they have in the system and how operates in their systems (e.g. what is the flow and pressure of the pump during a given operating cycle). Because of this information, a marine engineer is able to swiftly solve a system issue and identify potential trends in pump failure.
The pumps must be checked daily, when in service, for any abnormal noises, vibrations and overheating and if and when it is possible for proper flow and pressure.
The best maintenance practices is to check and record flow and pressure during specific operating cycles; review graphs of pressure and flow and check for excessive fluctuation of the hydraulic system (usually the maker designate the fluctuation allowed).
It is important to note that hydraulic pumps are very sensitive to impurities and their inner working parts are mainly made of brass. Therefore, any kind of system oil contamination must be avoided as will interfere with pump working performance and lifetime.
The hydraulic hoses are designed to to allow fluid to flow from one component to another and they are a vital part of keeping hydraulics systems moving. Any type of hydraulic hoses are required to meet stringent standards to accustom pressure points, loads, and also their position demanded. To perform heavy-duty functions, some engineering elements are assumed to confront the forces within and be flexible enough to bend or reach diverging angles.
It is simple to detect problems with your hydraulic hose assemblies if you check the hoses on a monthly basis. These problems could lead to more serious concerns in the future. A marine engineer must ensure that fluid designed temperature and pressure are not exceeded and all system’s safety features and protections are fully operational. Do not disregard the leakages because the presence of any external leakage indicates that something is wrong. Hydraulic oil is expensive on its own, but if there is a significant leak, additional costs will be incurred due to fines from the Environmental Protection Agency as well as the expense of cleaning up the spill. The fact that a machine operator or technician could easily slip and fall on the remnants of a leaky hydraulic system is another significant cause for concern regarding the level of safety that is there. When threaded pipe couplings, valve seals, and flexible hoses burst or vibrate loose, not only does pressurized hydraulic fluid create a significant risk of fire, but so does pressurized hydraulic fluid.
A marine engineer must learn to identify potential hazards, like cracks, abrasions in the cover, tight bends or twisting. The cover protects the reinforcements (wire or fabric) from weather and any other environmental hazards. If the wire or fabric is exposed, water and debris can adversely affect the reinforcement by either rusting the wire or, in the case of fabric, allowing water to wick into the system and get behind the coupling where it can cause damage.
Hoses are a relatively insignificant component of hydraulic equipment and machinery, as you are aware; nonetheless, if they are not properly maintained, they may be the source of some of the most significant issues as well as major injuries.
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Source and Bibliography:
- YouTube video training credit – Marine Online; Lunchbox Sessions; Donaldson Hydraulic; Al Sikander Parts