what causes hydraulic pump whine factory

Pump cavitation is first and foremost caused by insufficient flow. This happens when the volume of fluid being supplied doesn’t meet the demands of the hydraulic circuit, and the pressure at the suction end of the pump isn’t sufficient. This leads to the absolute pressure falling below the vapor pressure of the liquid, which leads to air bubbles being formed. These tiny bubbles implode as they pass through the system, creating shockwaves and causing pump vibrations.

The process of these bubbles forming and collapsing is done with a great deal of force, and leads to eventual metal erosion inside the pump. The mechanical damage caused by cavitation can have irreversible impacts on system components and may possibly lead to complete failure. Cavitation happens only on the suction side of the pump, and may be caused by a series of different malfunctions, including:

Cavitation is typically characterised as a high-pitched whining or screeching sound, and in some extreme cases, can present itself as a loud rattling sound. Whilst these hydraulic pump whine noises are generally the most obvious telltale signs of cavitation, other symptoms to look out for also include:

By design, hydraulic pumps contain a miniscule amount of air which allows space for the hydraulic fluid to heat up and expand. However, too much air in the pump can cause serious issues – this is known as aeration.

Aeration in a hydraulic pump occurs when there is an air leak in the suction line. When outside air enters the pump through a damaged connector, loose pump seal, pipe fitting, or any other damage, it gets drawn into the pump’s hydraulic fluid supply. This unwanted air quickly gets dissolved into the hydraulic fluid and leads to contamination.

Contaminated hydraulic fluid can have serious implications for the system, as the excess air means that it cannot conduct heat as efficiently and can cause the fluid to foam. This can lead to overheating and in some cases, a substantial decrease in power. Aeration may happen on both sides of the pump, and has several causes including:

Similar to cavitation, aeration is usually indicated by a sudden change in noise, which can sometimes make it difficult to differentiate between the two causes However, aeration tends to produce a more erratic low-pitched ‘rumbling’ or ‘rattling sound, as opposed to the more consistent whining noise of cavitation.

Every hydraulic pump makes some noise. If all is well with a pump, then this noise stays more or less the same. However, if something goes wrong with the pump or its connected system parts, then you may start to hear sounds that you haven"t heard before.

The fluid that flows through your system needs to move at a smooth and even rate. The pump has to deliver the fluid at a specific flow for things to work.

If something prevents the fluid from achieving and maintaining its optimum flow, then your pump may start to make unusual noises. For example, you may hear a high-pitched whine coming from the pump. This can be a constant or intermittent sound.

If your pump whines constantly, then you may have a cavitation problem. Here, the pump can"t deliver its fluid at the right volume or rate. There isn"t enough fluid coming through the pump"s suction line.

In some cases, this is a sign that your pump"s motor is on the wrong setting. So, the pump itself is working at the wrong speed to create the right flow.

A hydraulic pump might get noisy if one of its parts or connections has a problem. A faulty or failing pressure control, bearing, valve, seal, or coupling can make a noise you haven"t heard before.

In some cases, you may hear vibrating clunks as your pump works if you have a problem with a connecting pipe. A loose seal or connector might allow the pipe to move. It then passes vibrations along to the pump itself.

While some noise problems are easy to fix, some are a sign that your pump is close to the end of its working life. Sometimes, this is due to natural wear, usage, and age. However, in some cases, minor problems cause more widespread damage if you don"t fix them quickly.

For example, if you"ve had cavitation problems for a while, then your system may not have been getting the lubrication it needs; it may have overheated regularly. Even if you fix the cavitation issue, you may be left with a damaged pump that needs a more significant repair, rebuild, or replacement.

So, while new sounds or an increase in operating noise don"t necessarily mean that you have a serious pump problem, you should investigate any unusual noise. Typically, this is a sign that something isn"t working right.

A minor problem in your system could go on to cause significant damage. For an expert diagnosis, contact Quad Fluid Dynamics, Inc. Ourhydraulic pump repair and rebuild servicewill get your pump running smoothly and efficiently again.

Excessive or erratic hydraulic pump noise is a symptom of malfunction that could cause damage or accelerated wear if not addressed quickly and correctly. While it’s never nice to hear strange noises emitted from your pump, different forms of noise, which are related to different faults can provide valuable clues that can help you to diagnose your problem and get it fixed before it turns into something major.

So it pays to know what different pump noises mean and with practice you can quickly distinguish between the normal operating sounds and signs that something is wrong. In this article, we’ll talk about what causes some of these sounds, so you can identify them.

A constant hissing sound is indicative of a relief valve that is set too low or is stuck open and is continually releasing pressure. An erratic whistling sound is a symptom that a relief valve is set incorrectly or is damaged. It is common for pump settings to be changed carelessly or inadvertently - sometimes to overcome other issues with the hydraulic system - sometimes due to a lack of understanding of the correct operating conditions, so include this in your regular checks. In addition to noise problems, relief valve damage can be accompanied by slamming of actuators, stalls and excessive heat generation.

Noise issues are just one symptom that gives you a clue when things go wrong with your hydraulic pump. There are several other issues to know and understand, which could help you to identify pump problems quicker. Which means you can sort them out sooner - potentially saving big money down the road. These include heat problems, pressure problems and flow problems.

Abnormal noise in hydraulic systems is often caused by aeration or cavitation. Aeration occurs when air contaminates the hydraulic fluid. Air in the hydraulic fluid makes an alarming banging or knocking noise when it compresses and decompresses, as it circulates through the system.

Other symptoms include foaming of the fluid and erratic actuator movement. Aeration accelerates degradation of the fluid and causes damage to system components through loss of lubrication, overheating and burning of seals.

Air usually enters the hydraulic system through the pump’s inlet. For this reason, it is important to make sure pump intake lines are in good condition and all clamps and fittings are tight. Flexible intake lines can become porous with age; therefore, replace old or suspect intake lines. If the fluid level in the reservoir is low, a vortex can develop, allowing air to enter the pump intake.

Check the fluid level in the reservoir, and if low, fill to the correct level. In some systems, air can enter the pump through its shaft seal. Check the condition of the pump shaft seal and if it is leaking, replace it.

Cavitation occurs when the volume of fluid demanded by any part of a hydraulic circuit exceeds the volume of fluid being supplied. This causes the absolute pressure in that part of the circuit to fall below the vapor pressure of the hydraulic fluid. This results in the formation of vapor cavities within the fluid, which implode when compressed, causing a characteristic knocking noise.

The consequences of cavitation in a hydraulic system can be serious. Cavitation causes metal erosion, which damages hydraulic components and contaminates the fluid. In extreme cases, cavitation can cause mechanical failure of system components.

While cavitation can occur just about anywhere within a hydraulic circuit, it commonly occurs at the pump. A clogged inlet strainer or restricted intake line will cause the fluid in the intake line to vaporize. If the pump has an inlet strainer or filter, it is important for it not to become clogged. If a gate-type isolation valve is fitted to the intake line, it must be fully open.

This type of isolation device is prone to vibrating closed. The intake line between the reservoir and pump should not be restricted. Flexible intake lines are prone to collapsing with age; therefore, replace old or suspect intake lines.

Fluid temperatures above 180°F (82°C) can damage seals and accelerate degradation of the fluid. This means that the operation of any hydraulic system at temperatures above 180°F is detrimental and should be avoided. Fluid temperature is too high when viscosity falls below the optimum value for the system’s components. The temperature at which this occurs is dependent on the viscosity grade of the fluid in the system and can be well below 180°F.

High fluid temperature can be caused by anything that either reduces the system’s capacity to dissipate heat or increases its heat load. Hydraulic systems dissipate heat through the reservoir. Therefore, the reservoir fluid level should be monitored and maintained at the correct level. Check that there are no obstructions to airflow around the reservoir, such as a build up of dirt or debris.

It is important to inspect the heat exchanger and ensure that the core is not blocked. The ability of the heat exchanger to dissipate heat is dependent on the flow rate of both the hydraulic fluid and the cooling air or water circulating through the exchanger. Therefore, check the performance of all cooling circuit components and replace as necessary.

Air generates heat when compressed. This means that aeration increases the heat load on the hydraulic system. As already explained, cavitation is the formation of vapor cavities within the fluid. These cavities generate heat when compressed. Like aeration, cavitation increases heat load. Therefore, inspect the system for possible causes of aeration and cavitation.

In addition to damaging seals and reducing the service life of the hydraulic fluid, high fluid temperature can cause damage to system components through inadequate lubrication as a result of excessive thinning of the oil film (low viscosity). To prevent damage caused by high fluid temperature, a fluid temperature alarm should be installed in the system and all high temperature indications investigated and rectified immediately.

A reduction in machine performance is often the first indication that there is something wrong with a hydraulic system. This usually manifests itself in longer cycle times or slow operation. It is important to remember that in a hydraulic system, flow determines actuator speed and response. Therefore, a loss of speed indicates a loss of flow.

Flow can escape from a hydraulic circuit through external or internal leakage. External leakage such as a burst hose is usually obvious and therefore easy to find. Internal leakage can occur in the pump, valves or actuators, and unless you are gifted with X-ray vision, is more difficult to isolate.

As previously noted, where there is internal leakage there is a pressure drop, and where there is a pressure drop heat is generated. This makes an infrared thermometer a useful tool for identifying components with abnormal internal leakage. However, temperature measurement is not always conclusive in isolating internal leakage and in these cases the use of a hydraulic flow-tester will be required.

Proactively monitoring noise, fluid temperature and cycle times is an effective way to detect conditions that can lead to costly component failures and unscheduled downtime of hydraulic equipment. In most cases, informed observation is all that is required.

Many industrialized countries have regulations restricting noise levels in the workplace. The high-power density and corresponding high noise emission of hydraulic components cause industrial hydraulic systems to be the target of efforts to reduce mean noise levels.

The pump is the dominant source of noise in hydraulic systems. It transmits structure-borne and fluid-borne noise into the system and radiates air-borne noise.

All positive-displacement hydraulic pumps have a specific number of pumping chambers, which operate in a continuous cycle of opening to be filled (inlet), closing to prevent back flow, opening to expel contents (outlet) and closing to prevent back flow.

The pump also creates structure-borne noise by producing vibration in any component it is mechanically linked to, for example, the tank lid. The transfer of fluid- and structure-induced vibration to the adjacent air mass results in air-borne noise.

While fluid-borne noise caused by pressure pulsation can be minimized through hydraulic pump design, it cannot be completely eliminated. In large hydraulic systems or noise-sensitive applications, the propagation of fluid-borne noise can be reduced by the installation of a silencer.

Structure-borne noise created by the vibrating mass of the power unit (the hydraulic pump and its prime mover) can be minimized through the elimination of sound bridges between the power unit and tank, and the power unit and valves.

The magnitude of noise radiating from an object is proportional to its area and inversely proportional to its mass. Reducing an object’s surface area or increasing its mass can therefore reduce its noise radiation. For example, constructing the hydraulic reservoir from thicker plates, which increases its mass, will reduce its noise radiation.

Air-borne noise can be reduced by mounting the hydraulic pump inside the tank. For full effectiveness, a clearance of half a meter between the pump and the sides of tank is required. The mounting arrangement must also incorporate decoupling between the power unit and tank to insulate against structure-borne noise. The obvious disadvantage to this is the access for maintenance and adjustment is restricted.

Another source of noise in hydraulic systems derives from the storage and subsequent release of energy in the hydraulic fluid. Hydraulic fluid is not perfectly rigid, and the compression of the fluid results in energy storage, similar to the potential energy stored in a compressed spring.

The ratio of a fluid’s decrease in volume as a result of a pressure increase is given by its bulk modulus of elasticity. The bulk modulus for hydrocarbon-based hydraulic fluids is approximately 250,000 PSI, (17,240 bar) which results in a volume change of around 0.4 percent per 1,000 PSI (70 bar).

Although hydrocarbon-based hydraulic fluids compress 0.4 to 0.5 percent by volume per 1,000 PSI, in an actual applications compression should be calculated at 1 percent per 1,000 PSI. This compensates for the elasticity of the cylinder and conductors and variations in the volume of air entrained in the fluid.

Storage and release of energy in the fluid also occurs during a phenomenon know as “water hammer.” Water hammer is the term used to describe the effect that occurs when the velocity of the fluid moving through a pipe suddenly changes. This change causes a pressure wave to propagate within the pipe.

Returning to the traffic crash analogy – the slower the car is traveling upon hitting the wall, the less damage that occurs. In hydraulics, the most efficient way to do this, on paper at least, is to increase the diameter of the pipe, which reduces fluid velocity for a given flow rate.

The alternative is to control deceleration of the fluid column by choking the valve switching time to the point where the pump’s pressure compensator and/or system relief valve reacts fast enough to reduce flow rate through the pipe and therefore the velocity of the fluid column.

Hydraulic pumps are at the core of many essential factory operations. Unfortunately, there are numerous pitfalls to plan for, mitigate, and overcome to keep them running. Keeping up on routine maintenance is important, but the best way factory techs can avail themselves of costly, frustrating breakdowns is to understand the various catalysts for hydraulic pump failure.

The simplest way to identify the cause of pump failure is to thoroughly inspect and dissect the aftermath of the problem. In most cases, the cause of failure will be evident by the nature of the catalyst(s). Here are eight of the most common problems, some of their defining features, and how they ultimately come to fruition.

1. Fluid contamination is one of the biggest causes of hydraulic pump damage and involves debris mixing with the liquid. This debris causes friction, leading to extenuated wear on the pump itself. The result is inefficiency, culminating in malfunction.

2. Fluid viscosity issues occur when the hydraulic fluid within a pump breaks down over time. Viscosity that’s too high leads to cavitation (another catalyst for damage). Subsequently, if a tech changes and replaces fluid with a viscosity that’s too low, heat and friction become concerns.

3. Over-pressurization occurs because of excessive load on the pump itself, resulting in red-line operation that’s both unsafe and damaging. Hydraulic pumps operating under high duress for extended periods of time will likely experience component wear and premature failure, usually in spectacular fashion.

4. Excess heat can be a product of poor fluid viscosity or environmental factors. This issue is rarely a singular catalyst for pump breakdown, but it exacerbates other factors or masks other issues, such as fluid contamination.

5. Implosion invariably results in extreme failure for hydraulic pumps and is a major safety hazard. Implosion occurs when air bubbles within a hydraulic pump collapse, causing an overload of pressure to the pump that generates an intense shock.

6. Aeration occurs when hydraulic fluid traps air bubbles. The pump subjects the bubbles to pressure, causing high heat and over-pressurization when the bubbles collapse. Aeration at extreme levels leads to implosion.

7. Pump aeration pertains to air not in the hydraulic fluid, but air introduced through unsealed joints or shafts. This air quickly causes pressure instability affecting crucial parts of the pump. This can quickly lead to breakdowns — generally marked by a whine or other high-pitched sound.

8. Cavitation is a symptom of uncontrolled pump speeds, which fail to allow hydraulic fluid to completely fill the pump. It results in destabilized pressure, heat, and excess wear. Cavitation is often marked by the same type of whine or squeal as pump aeration.

Because the factors causing each of these problems differ in nature, it’s best to fully evaluate a damaged hydraulic pump to determine if more than one issue is responsible.

Maintenance is the best approach for ensuring safe, efficient hydraulic pump function. But routine service is just the start. Identifying common issues plaguing your hydraulic pumps will lead to a better quality of targeted maintenance — for example, if you pinpoint a heat issue related to viscosity, that issue may be resolved by opting for a different fluid weight.

Every piece of information learned about your pumps can translate into better care, leading to longer uptimes, fewer issues, and fundamentally better maintenance.

Having trouble identifying the catalysts for your hydraulic pump’s issues? Let the professionals at Global Electronic Services take a look! Contact us for all your industrial electronic, servo motor, AC and DC motor, hydraulic, and pneumatic needs — and don’t forget to like and follow us on Facebook!

The pump is the most expensive and critical component in any hydraulic system—it works by first creating a vacuum at the pump inlet, which generates atmospheric pressure. Liquid from the reservoir tank is then propelled through the inlet line to the pump, past a hydraulic filter or strainer, and into the hydraulic system. On a macro-level, the mechanical energy of the pump’s gears is transferred through fluid “flow” and used to power the attached hydraulic machinery.

Although hydraulic systems can be used in many everyday objects, they’re usually best suited for products that require high-power density or systems with changing load requirements. This simple yet elegant design offers exceptional consistency and speed compared to other driving mechanisms. Hydraulic systems are widely used across industries because they are reliable, easy to maintain, long-lasting, and safe. But despite their many advantages, hydraulic systems still require some degree of maintenance. The following guide explains what can make a hydraulic pump fail, as well as tips for extending its useful lifespan as much as possible.

Fluid contamination is the leading cause of pump failure and usually happens when particulates circulate through the system via a breather valve or cylinder rod, or as a result of repairs, welding slag, sealant, or refilling. Once contaminants enter the system, they can degrade parts, create buildup, change the fluid’s physical and chemical properties, corrode equipment, and lower the system’s overall efficiency.

Hydraulic pumps are designed to work within a specific pressure range. If pressures exceed the pump’s rating, it will likely overburden the pump, cause damage, and eventually halt operations completely. If the pressure changes are extreme, it could even cause an explosion.

Joints and shafts must be completely sealed for the hydraulic pump to work properly. If air gets trapped inside the system, bubbles can cause pressure and temperature fluctuations, which eventually will cause the pump to break down. Usually the first sign there’s air in the pump is a high-pitched whine.

Cavitation occurs when the pump speed is inconsistent, creating air bubbles that rapidly form and then collapse. When this happens, the pump won’t completely fill with fluid, which destabilizes pressure in the system and produces the same type of high-pitched squeal as pump aeration. A blocked pipe, clogged filter, or poor system design can all cause cavitation.

Hydraulic systems need high-quality cooling and lubrication oil with the right mineral content and viscosity. Purity is particularly important for high-pressure systems that operate with larger loads.

The best way to prevent hydraulic pump failure is to inspect and maintain your hydraulic system. Hydraulic filters and strainers will help you avoid fluid contamination, which in turn will stabilize the temperature and pressure inside the system. Filters remove particulates that are smaller than 50 microns, and strainers work tangentially to remove contaminants larger than 50 microns. Various options are available for both filters and strainers using different ratings, mesh sizes, and materials.

After they’re installed, filters and strainers need to be routinely checked and cleaned. Operators should familiarize themselves with their hydraulic system to identify any aberrant conditions as soon as possible, if problems should arise. If you maintain your hydraulic system, it will work more efficiently, necessitate fewer repairs, require less downtime, and last as long as possible.

With over 60 years of experience manufacturing high-quality suction filters, suction strainers, gauges, and diffusers for hydraulic systems, the experts at DOMS Incorporated have the expertise to keep your operation in peak condition. We’ve worked closely with organizations from many industries, including construction, forestry, mining, energy development, industrial manufacturing, aircraft equipment manufacturing, plant processing, and more.

The high-pitched mechanical tones of a tortured hydraulic system are often traced back to squealing hydraulic cylinders. A regimented troubleshooting procedure then makes haste to eliminate the noisome wail and determine whether more is going on here. Ask the right questions before jumping in, though, and avoid an unproductive repair experience. Does the squealing happen at all flow rates? Is stroke speed contributing to the problem? It’s this process of elimination that will get the gear mobile again, so let’s get our own system-diagnosing brains moving.

Aeration is a common factor in this situation. Aeration is simply a leak, one that usually occurs on the suction side of the mechanism. The resulting leak causes an erratic whine or squealing noise to propagate along the frame of the mobile gear, but it usually tracks back to the cylinder. Of course, as with any diligent system analysis process, the initial cause doesn’t always bring the story to a fast end. There’s the cause of the aeration to discover. Again, it’s a Sherlockian process of elimination that works best. Replace parts if necessary, but begin with cheaper replacements. The rod and piston seals make a fine start point, but this issue may not even be a mechanical problem, so what ails the cylinder?

If the cylinder is tested and found to be in optimal working condition, then what about checking the oil? Hydraulic fluid is vulnerable to atmospheric contamination, so a potential leak may originate at another point on the system but be carried into the cylinder. The oil foams or takes on the consistency of a soapy scum. The cylinder compresses, as it should, but the typically non-compressible oil squeezes the tiny air bubbles until they heat and release energy as that alarming shriek. Corrective actions at this point suggest an initial look at the oil, followed by an inspection of the couplings that hook the cylinder to the mobile vehicle. Now, if these tests don’t yield fruit, then and only then is it time to cause a stoppage by taking the cylinder back to the bench for further testing.

There’s a law that engineers find very useful when a troubleshooting protocol is active. It’s called Occam’s Razor. Basically, it states that the simplest answer is usually the correct one, so begin with obvious problems before making an impulsive decision to disassemble a squealing hydraulic cylinder. Look for aeration in the oil before replacing seals or the entire unit.

The challenge with hydraulic pumps is that they are often neglected until something goes wrong. You wouldn’t be blamed for not knowing how often you need to service your hydraulic pump or how often it needs maintenance. However, some common signs indicate when your pump needs to be rebuilt instead of just serviced. If any of the following statements apply to your pump, then it’s time for a rebuild.

The noise could be from the internal parts rubbing together or from hydraulic fluid rushing through the system. Perhaps it is worn out or there is too much load on the pump. A worn-out pump will have higher internal friction than a new pump, causing extra noise. In addition, a worn or damaged pump may not be able to handle a high load without heating up. This will make it vibrate more and increase pump noise. If you hear humming or grinding noises from your pump, it is important to investigate the cause immediately because the cause could be very serious.

First, you should check the fluid level when your machine is off. If the fluid level is below the normal mark, the pump may not be returning all the fluid to the tank. If you notice that the fluid level is at the top while the machine is off, it could be that the pump is not drawing enough fluid. If the pump is operating normally and the fluid level is low, there may be a leak in the system.

A hydraulic pump is enclosed, and many of the internal parts are made of metal. The metal parts are subject to corrosion and some wear. This means that your pump can leak hydraulic fluid from time to time. When fluid leaks from the pump, it will smell, and there will be a puddle of fluid on the floor, where the pump is located. A bad smell coming your hydraulic fluid can be an indication of dirty, contaminated oil and failure of the internal pump components.

When a pump is new, it uses some of the fluid in the system to build up pressure. As the pump ages, it uses more fluid. If the pump is running but the pressure is lower than normal, it could be a sign that the pump is worn out. When you are operating your machine and the pressure drops, it is best to stop the machine and investigate. If the pressure is high, but well below normal, it could be that the pump is not drawing enough fluid and the pressure is high because there is too little fluid in the system.

Whatever the reason, if your pump is worn out, it is time to rebuild it. A worn-out pump will not be able to do the job it was designed to do. It may be unable to provide the necessary pressure or flow rate, or it may just fail when you need it most. When your pump is worn out, you need to have it rebuilt or replaced. A worn-out pump is also a safety hazard because it may not be able to handle the necessary pressure or flow rate.

In any hydraulic system, the hydraulic pump is usually the most expensive component and if it fails the whole system can be rendered inactive. Hydraulic pumps are extremely sensitive to contaminants and have the highest reliability risk. When a hydraulic pump starts to fail, it can force contaminants and debris further down the system and if this is not intercepted by an effective filter, the debris can then cause damage to other components. With this in mind, it is worth knowing the warning signs of common hydraulic problems and the precautions or actions that should be taken to prevent the lost work time and expense resulting from pump failure. As experts in hydraulic pump repairs, we at CJ Plant reveal the common causes of hydraulic pump failure.

In any mechanical system, components will be subject to wear and tear throughout their working life and will eventually wear out. Poor quality components will obviously have a shorter lifespan and should, therefore, be avoided, but there are a number of system failures common to all models of hydraulic pump that can easily be prevented if users are vigilant and pay attention to the operation of the system they are using. There are three common hydraulic pump failure symptoms that operators should be aware of that can be an indication of impending hydraulic pump failure:

If the hydraulic pump is making a whining noise or producing banging or knocking sounds, it can be assign of aeration or cavitation inside the pump. As the piston operates, pressure inside the pump drops and the resulting higher atmospheric pressure in the reservoir pushes hydraulic fluid along the inlet line into the pump. Anything that reduces this inlet flow can cause dissolved air in the oil to be drawn out forming air bubbles. When these reach an area of high pressure, the bubbles will implode under pressure and the resulting shockwaves will produce a high pitched whining sound. This can be assign of a damaged or blocked suction strainer or a plugged breather cap. High temperature in the fluid can also cause air to be released or low temperature can increase viscosity and slow fluid entering the pump so fluid temperature should be monitored closely. While not a common problem in the UK, systems operating high above sea level can also suffer from insufficient fluid entering the inlet due to atmospheric pressure being too low to push it through. Air from outside entering the system will result in aeration and will result in a knocking or rattling sound in the pump. As the pressure inside the system is lower than outside, any leaks in the suction line or the cylinder seal will cause air to enter the system. Poorly tightened connections on the suction line can also result in this problem. If this is suspected apply a layer of oil over any suspected location for a leak. If a hole appears in the oil as air is drawn in, the leak has been located. The noise will subside momentarily as this happens if aeration is the cause of the sound. If a leak is not located, check the reservoir. If the fluid level is too low, air can also been drawn in here or if the fluid entering the reservoir is dropping from a height it can cause bubbles to form as the fluid splashes which again can then enter the system. Any foaming of the fluid in the reservoir is another sign of aeration as the air exiting the system will cause foam to form.

Hydraulic fluid in a working system should never be above a temperature of eighty two degrees Celsius. A temperature exceeding this can be an indication of a malfunctioning heat exchanger or an overheating final drive motor. Cooler fins and the cooling fan should be cleaned and inspected for any damage, along with the fan belt, Any change in the pressure in the system from the manufactures settings will lead to an increase in temperature, along with other problems. Pressure levels should be checked in case deliberate or accidental adjustment of pressure has been carried out and relief valves checked in case they are damaged or incorrectly adjusted, as this can also lead to a change in system pressure and subsequent overheating. A lowered level of hydraulic fluid in the reservoir can also lead to overheating. if this is the case, the level of fluid should be topped up and the reservoir checked for any leaks that could be leading to this. All filters should checked for build up of debris or blockage as this can also affect pressure in the case of internal filters or cause insufficient flow of air in cooling systems. It is also worth considering the use of an offline filter

If your hydraulic system is running slower than usual, or showing increased cycle times, this is an indication of a drop in pressure within the system which can then lead to a subsequent overheating. This can be an indication of a leak in the system. If it is an external leak, it will usually be easy to locate and repair. However, if no external leak is visible it could be a sign of an internal leak in the gear pump or actuators and a hydraulic flow tester should be employed to test for this and locate the leak for repair.

While using good quality hydraulic fluid and implementing good contamination control systems can avoid many problems, sometimes the worst can still happen. If any of the above indicators are observed, they should not be ignored and the source of the problem located and repaired before they cause further damage. The implosion of air bubbles during cavitation can cause internal wear on the pump and dislodge debris or metallic fragments that can travel through the system, causing wear and erosion to components. These can then lead to further system failure. Aeration can lead to lowered lubrication inside the pump, leading to friction between metal components and the pump seizing up. This can not only damage the pump but also alter the pressure in the system, causing overheating and damage to other components.  Overheating can lower the viscosity of hydraulic fluid, lowering its ability to lubricate and degrading it and shortening its lifespan and causing heat damage to seals, leading to leaks.

Any one of these issues can lead to a cascade effect, causing damage to multiple parts of the overall system and resulting in lost work hours and revenue and expensive repairs. If your equipment is displaying any of these symptoms, call CJ Plant maintenance today. We understand that when your equipment is malfunctioning or damaged you need fast and efficient diagnosis and thorough professional repairs as soon as possible. We carry out hydraulic pump repair and plant maintenance to customers throughout the UK and offer free collection, wherever you are located if we cannot perform repairs on site. We will thoroughly inspect your faulty equipment and offer a full evaluation and no obligation quote for repair. After repair we will return your equipment fully restored to OEM standards with a written twelve month warranty. For further information on the services we provide, please contact us, we will be happy to help.

A steel mill reported a strange noise at one of several hydraulic motors driving a roll on a rolling mill. The hydraulic power supply was in the basement of the steel mill.

The hydraulic motors on all the driven rolls were bent-axis piston motors with a manifold block mounted on the motor containing two cross post reliefs. The control valves were mounted on valve stands in the basement along with the main pumps. The noise was only on one unit at the roll.

Maintenance told me that one hydraulic motor was “gurgling” on start up. After a few minutes it would quite down and seem fine. However, each time the mill was stopped for more than a few minutes, it would happen again. They replaced the motor but still had the same problem. One mechanic thought it might be caused by a new hose they had installed before the noise problem, but it looked like a good assembly. There was no sign of oil leaking from any plumbing connections to the motor, which could allow air to enter when the unit was shut down.

Noise is undesirable because it can cause additional load on hydraulic components leading to premature failure, additional system cost, operator fatigue and potential hearing loss. The U.S. Department of Labor’s Occupational Safety and Health Administration (OSHA) states that exposure to 85 dB(A) of noise for more than eight hours per day can result in permanent noise-induced hearing loss (NIHL)1.

Noise is known to cause many issues with components in hydraulic systems but in particular steel tube assemblies are known to be very susceptible to vibration failure.

Vibration can travel through the system via the fluid and/or metal components transmitting to all parts of the equipment. Noise travels easily through the metal components such as pumps, valves, cylinders, steel tubes and elbow fittings but can also travel through the steel wire reinforcement in the hose.

A quick and easy solution that some designers have discovered to eliminate noise in power steering systems, hydrostatic pumps, pump outlets, motor inlet/outlet and PTOs is to utilize thermoplastic fiber reinforced hose. This hose is constructed using a variety of smooth bore polymer inner cores for a high degree of chemical compatibility, high strength fibers, and a polymer jacket. Fiber braided thermoplastic hose is available in pressure ratings from 500 psi to 7500 psi.

Parker"s Parflex Division is contacted at least once a month by companies looking to bring the noise down below audible noise level (vibration). Through years of studying noise and its effects on hydraulic systems, as well as, working closely with our customers to reduce application-specific noise, Parflex has developed an extensive line of thermoplastic hoses with a high degree of dampening effects.

Parflex 510D, 518D, 520Nand 53DM are most suited for reducing noise and have a working pressure range of 1500 to 5000 psi at a 4:1 design factor. Hose selection tools and application engineering expertise are available through Parflex for your equipment hydraulic design needs.

Air that enters a hydraulic system can cause many problems that could subsequently lead to system failure. Here FPE Seals discusses how to spot these potential problems and why it is so important that air is bled from a system as soon as it is detected.

Essentially, hydraulic pumps are not designed to pump air because when compressed air generates heat. When air contaminates a hydraulic fluid, usually via the pump’s inlet, aeration, cavitation, or foaming can occur.

Aeration is bad news, as it degrades the hydraulic fluid causing damage to the components of the system due to loss of lubrication, resulting in overheating and burning of the seals. Overheating is particularly dangerous as dieseling can occur when the hydraulic cylinder oil mixes with the air, causing an explosion under compression.

Cavitation, brought on by the rapid changes of pressure in the fluid, causes small vapour-filled bubbles to contaminate the system, which implode when compressed. Ultimately this leads to metal erosion, which harms the system’s components and contaminates the fluid.

Abnormal noise is often a tell-tale sign that there is trapped air in a hydraulic system. As air circulates through the system it compresses and decompresses, creating a banging or knocking noise.

It is also important that displacement hydraulic cylinders are bled before installation as any air trapped in the system would work like a gas shock absorber. For this reason, displacement cylinders have a breather at the top, to disperse any air.

And lastly, when testing a new cylinder, it is important to check for potential air contamination, as this can result in blowing the dirt wiper and the hydraulic seal out of its housing extruding past the rod.