what causes a hydraulic pump to get hot quotation

Is your hydraulic pump getting excessively hot during normal operation? Pumps do generate heat when running, however they are designed with specific heat parameters in mind. Overheating is an abnormal condition that leads to destructive issues such as thinning of hydraulic fluid, which leads to reduced lubrication, metal-on-metal contact of moving parts. And accelerated pump wear and failure.

Therefore it is never a good idea to ignore a pump that is exceeding its heat parameters under normal load. There are a number of factors that contribute to an excess buildup of heat and in this article, we’ll explain some of these issues.

Hydraulic fluid viscosity refers to the thickness or “resistance to pouring” of your hydraulic fluid. This is very important to the correct operation of your pump. The fluid not only transmits the power that moves your drives and actuators. It also lubricates internal components and removes heat from the system. Hydraulic fluid is designed to operate at a specific temperature range. As it heats, it becomes thinner and eventually it will lose the ability to lubricate moving parts. The increased friction may cause the pump to heat up, and naturally increased wear will be taking place when this is happening. On the other hand, hydraulic fluid that is too thick flows less efficiently within the system, which also results in heat buildup.

Fluid that is contaminated with dirt, debris, water and other impurities may cause heat build up in a few ways. Blocked fluid filters, pipes and strainers place undue load on the pump or even lead to pressure drops on the back side of filters that cause cavitation.

Low fluid levels can result in a condition in which not enough flow is reaching the critical hydraulic components and moving parts. This is known as oil starvation and just like running your car without oil, it will increase metal-on-metal friction and lead to increased heat and wear. Oil starvation can also be caused by clogged hydraulic filters, incorrect fluid reservoir design.

Cavitation is the rapid formation and implosion of air cavities in the hydraulic fluid. When these air cavities collapse under pressure, they generate a lot of heat. In fact, temperatures can reach up to 2700 degrees C at the point of implosion! Not only does cavitation compromise the lubrication properties of the oil, the excessive heat that is generated is extremely damaging to the hydraulic pump and the system as a whole. Attacking hoses and seals and causing metal components to expand and wear.

This happens when air makes its way into the system via air leaks at points like pump seals, and pipe fittings. And what happens next in a hydraulic system? Compression! Air generates heat when compressed, which naturally leads to an increase in temperature if left untreated. In extreme circumstances it can also lead to ‘hydraulic dieseling’ whereby compressed air bubbles actually explode in the same process that powers diesel engines. This is not good and leads to degradation of the fluid and damage to system components through loss of lubrication and burning of seals.

As pumps wear, the internal leakage or “slippage” increases. Essentially, fluid is able to make its way past tight fitting components, which reduces the efficiency of the pump, but in addition, as this occurs, fluid moves from a high pressure to a low pressure without doing any mechanical work, since according to the laws of physics energy cannot be destroyed, it is instead converted into heat.

A build-up of excessive heat is a symptom of hydraulic pump problems, but it is far from the only signal that there may be something wrong. There are other important warning signs that you should pay attention to. These include unusual noises, pressure problems and flow problems. Each of these symptoms provide clues about any potential pump problems that need to be addressed - so it’s important to familiarise yourself with all of these issues. To help, we’ve created a downloadable troubleshooting guide containing more information about each of these issues. So that you can keep your system up and running and avoid unplanned downtime. Download ithere.

Hydraulic pumps generate heat while they run. However, hydraulic fluid temperature should never exceed180 degreesF (82 degrees C) under normal working conditions. If your hydraulic pump temperature rises above this, then that is a sign that your pump is likely overheating. One of the most common causes of hydraulic system failure is a hydraulic pump that runs too hot or overheats.

When a hydraulic pump runs at a too-high temperature for too long, it can ultimately lead to pump failure. Once a hydraulic pump begins to fail, it can potentially damage the entire hydraulic system by sending contaminants and debris into the system that can damage its other components.

In addition, when some hydraulic fluids are subject to high temperatures, they can thin and lose their viscosity. When hydraulic fluid is too thin, it is much more likely to leak, and fluid that has lost its viscosity cannot lubricate your pump properly. Extremely hot fluid can also damage pump seals, further increasing the chance of a pump leak.

Some hydraulic fluids thicken and oxidize when exposed to high heat instead of thinning. When hydraulic fluids are too thick, they can restrict flow throughout the entire hydraulic system, which leads to your system heating up even further.

The sooner you determine why your hydraulic pump is running hot and repair the cause of the problem, the less likely your hydraulic system will develop irreversible damage or fail completely.

Hydraulic pumps overheat for many reasons. Just a few of the most common causes of hydraulic pump overheating include: Contaminated hydraulic fluid. When fluid has debris and dirt, contaminant particles can quickly build up on hydraulic system filters, leading to filter clogs. Your pump has to work harder to pump fluid through clogged filters, which leads to overheating.

Aeration. Air leaks at seals and fittings on your hydraulic system components can lead to air entering your system and forming bubbles in your fluid. Air bubbles generate heat when your system compresses them and then pass this heat into the surrounding fluid, overheating it.

Low reservoir fluid. Since your hydraulic system releases some of the heat it creates into reservoir fluid, a low reservoir fluid level can contribute to overheating.

Blocked or damaged heat exchanger. This component is also an important part of your hydraulic pump"s cooling system. If it is blocked or damaged, then it cannot help remove heat from your pump properly.

Once your hydraulic pump beings overheating, you need to find the cause of the problem and repair it. That way, your pump can begin operating within its ideal temperature range again.

If your pump overheats due to fluid contamination, then either remove all contaminants from existing fluid or remove the current contaminated fluid from the system and add fresh fluid. Be sure to filter all fresh hydraulic fluid before you add it to your system because even this fresh fluid can contain contaminants. Also, replace your fluid filters on a regular basis to prevent the overheating that can occur when these filters become blocked with debris.

If air has entered your system through leaky seals and fittings, then have a hydraulic system repair expert inspect and replace or tighten these fittings. Have a hydraulic system repair expert also look at heat exchanger damage to determine if the exchanger needs repairing or replacing.

Finally, be sure to check your system"s reservoir fluid level on a regular basis. Add new fluid when necessary to help this reservoir perform its important task of helping to keep your pump cool.

Your hydraulic pump should always operate within its ideal temperature range. If your pump is running hot, then contact the hydraulic pump experts at Quad Fluid Dynamics, Inc., forhydraulic pump diagnosis and repairtoday.

Hot hydraulic fluid can be one of the causes of an overheating final drive motor. If your hydraulic fluid is running at a higher than normal temperature then it can cause problems for your entire hydraulic system. In this Shop Talk Blog post, we are going to talk about what can cause hydraulic fluid to overheat.

Another potential source of problems is a relief valve. If a relief valve fails or is out of adjustment, it can affect the system pressure. Changes in system pressure, as we just discussed, can also affect the temperature of the hydraulic fluid.

If you use the wrong type of hydraulic fluid for your machine, that, too, can cause the fluid to overheat. If that’s the case, then you need to replace the hydraulic fluid to fully address the problem.

If the oil cooler gets dirty or becomes plugged, that can also cause hydraulic fluid to run too hot. The solution to this problem is to take some time to clean off the oil cooler fins. Another potential source of problems is the cooling fan. If it is damaged, or if the fan belt isn’t at a right tension, then it can be the source of hot hydraulic fluid.

Another source of overheating lies in the level of your hydraulic fluid. If your reservoir is low on hydraulic fluid, that can cause the fluid that is in the system to overheat. However, that points to another problem: a leak somewhere. Don’t just top off the hydraulic fluid level, but also check for leaks that could be responsible for a low level of fluid.

If your hydraulic system is running too hot, then you need to track down the source of the problem. Hot hydraulic fluid will lead to damage and is a sign that something is wrong and needs to be addressed. If left unaddressed, then expensive issues and unnecessary downtime are bound to be the results.

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Whether you have a welded rod cylinder or telescopic cylinder, chances are you already know how destructive cylinder issues like fluid leaks can be. While leaks are known to cause cylinder issues, system overheating can be less obvious but just as pervasive. Hydraulic system overheating problems can be caused by different factors, including high heat hydraulic oil temperatures as well as system design pressure issues.

Hydraulic system heat contamination issues can be caused by different factors. With heat loading issues occurring from different sources, it is important to determine the correct cause of overheating for your hydraulic system. Common causes of hydraulic system overheating include:

Hydraulic fluid temperatures should stay within operating norms. Elevated or hot hydraulic oil can increase the chance of a system breakdown. High heat on hydraulic oil can increase oxidation, decreasing the oil’s performance and ability to maintain proper temperatures.

Higher hydraulic fluid temperatures can also create low viscosity issues. Maintaining normal viscosity levels allows your hydraulic system to function without added concerns about pump and valve wear and damage due to low viscosity.

Lack of fluid flow throughout your hydraulic system can cause motor issues as well as pump malfunctions and failure. Damage to your motor or pumps can require repair or component replacement.

When systems have component repair or replacement, there can often be incorrect upgrades or adjustments that adversely affect your system’s operating temperature.

Pressure issues can cause lack of fluid flow through your system. Pressure drop can occur due to lack of fluid flow through your system, resulting in higher operating temperatures and overheating.

While system damage from heat load can occur at any time, there are ways you can reduce and minimize system overheating. Troubleshooting tips for preventing hydraulic system overheating include:

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You can use multiple different upgrades and tuning methods on hydraulic systems. Many users will invest in upgrades that promise more flow and speed. The issue with these upgrades is that they"re not always fit for the hydraulic systems they"re applied to.

Since everything needs to stay in balance, you must make sure your upgrades match the entirety of your hydraulic system. For example, a higher flow pump can help give increased capabilities to a hydraulic system, but did you also check to see if the system"s hoses and piping can handle that increase in flow?

The increased flow can hit your smaller hoses hard and require more pressure just to get through them. This goes for any part of the hydraulic system that isn"t readily capable of handling more flow.

If a component becomes a flow throttle, the increase in pressure at the site can cause an overall pressure drop in the system. Also, the energy required to force flow will directly translate to an increase in heat, which lowers the systems efficiency and effectiveness.

When you make upgrades, also ascertain if you need to change other components. In the example of the higher flow pump, you can simply increase your hose size, and that makes all the difference.

Motors will get hotter is they are converting more power as a percentage of the power input will be lost as heat. More power in, more heat out. You should not run most components with normal hydraulic fluid over 70-80 degrees C as it will lose its lubricating properties and will the damage it causes is exponential.

In addition to the motor are: 2 pumps and a purge valve in the working circuit, a cooler supplied by the purge valve and the pump case drains and a reservoir and header tank. The case drain from the motor returns direct to the reservoir tank.

The working oil temperature has not exceeded 40 degC. The motor overheats before the working oil temperature reaches a temperature at which the cooler will have an effect. Oil temperatures in the case drain line are in the region of 80 - 90 degC once the motor casing reaches 100 degC. Case drain temperatures also show no signs of plateauing. RE: Hydraulic Motor Overheating

The system does not feature motor casing flushing (only a case drain), this is suggested by the motor OEM when motor speeds of 1800RPM are exceeded.What is the motor manufacturer? Is there datasheet available? RE: Hydraulic Motor Overheating

Thanks for the reply. The motor manufacturer is Parker and it is a F12-250 frame size motor. See below link for product literature, see page 67 for information detailing a recomendation for case flushing above 1800 RPM.

The datasheet invites you to ask Parker for more specific efficiency information for your particular frame size - please do this and then post the graphs for this forum. Somebody here will be able to show you how to interpret the graphs and estimate whether or not you need to flush the motor case. Also let us know what oil you are using because this may have a bearing on the matter.

Actually, you already know that you do need to flush the motor case because of the temperatures you are experiencing. The datasheet suggests you don"t need flushing but 1600 rpm is very like 1800 rpm and your working pressure is quite high. It"s not so black and white as 1799 rpm means flushing is NOT required and 1801 rpm means flushing IS required. It may be the case that the particular build up of manufacturing tolerances has meant you received a motor which is a bit tight (internal friction is a little high - resulting in more power loss but also resulting in a smallish case drain flow - so there isn"t enough case flow to take away the waste power - and that is why you are getting such a high case temperature).

According to the datasheet you are allowed to go up to 90 deg C for a motor with NBR seals (115 deg C for a motor with Viton seals) but, personally, I would prefer not to run at these temperatures for the following reasons:

Oil temperatures above 60 deg C can result in scalding/scarring if any escaping fluid contacts the skin (below this temperature getting soaked with the oil is just irritating, above this temperature it constitutes an injury).

The oxidation rate of the oil is very temperature dependant, doubling for every 10 deg C increase in temperature. Having very hot oil shortens its service life.

The very hot oil in the case will have a low viscosity and this will rapidly decrease the service life of the motor bearings. In a bent axis motor the shaft bearings work very hard.

I think you"ve taken the brochure wording a little bit too literally. The wording states that continuous operation "may require case flushing" and the limits are those which flushing is "usually required". Given you"re at 1600 rpm versus 1800rpm for the "usual" limit, then it would appear that the vendor has covered himself.

The amount of heat generated will be approximately the power input times (1-efficiency). There are equations in the first part of the book to work this put which needs flow as well as pressure. Given that there are no cooling vanes, whilst a lot of the heat will escape via the hydraulic fluid, enough will reomain to heat up the casing quite quickly as you"ve discovered.

I have received efficiency graphs from Parker for the 250 size motor, I have however been unable to upload them on to this thread. Reading the graphs I have estimated a volumetric flow efficiency of 97%, a mechanical efficiency of 97% and total efficiency of 94%. This does however seem a little high? From this and the pumps theoretical power output (174kW) I have estimated that 11kW of heat will be generated. What I am now trying to calculate is how much heat will be removed through discharge of fluid from the motor and how much will be left in the motor casing through convective heat transfer. Or perhaps I am going about this in the wrong way?

I fully appreciate that the Parker manual uses terms such as "may" and "usually" and that it is very much application specific. And It is clear that a flushing system is required. I would however like to apply some theory behind the application to ensure that my seniors are confident that this application is being investigated and justified thoroughly. What steps would you advise to follow once efficiency has been calculated to calculate heat dissipated by the fluid and heat remaining in the casing?

Looks like you"re nearly there. Measure temp in versus temp out of the hydraulic fluid x flow x thermal capacity and you have a good guess as to heat being carried away by the fluid. What"s left is basicaly heating the case up, so even if it"s 1kW, that 1kW into a relatively small thing with not much heat loss capacity other than convection - which won"t be much. You could get really scientific and apply some sort of water cooling blanket to calcualte the heat being generated in the casing and then show that without additional cooling the motor would simply continue to heat up.

If you had a 175 kW electrical motor and no fan on it then it would also get red hot. Electrical motor efficicieny at that size is about the same. Would you think that you could install an electrical motor that big and not cool it? Ok it doesn"t have fluid taking some of the heat away, but even so...

Here’s the quick and dirty calculation of drain oil temperature (there’s too many unknowns in the actual performance of your particular motor and too little precision in your efficiency data to warrant doing a more sophisticated calculation).

Your motor is 250 cc/rev and running at 1600 rpm so your theoretical input flow would be 400 L/min. But your volumetric efficiency is 97% so your actual input flow will be 400/0.97 = 412 L/min and we can assume that the extra 12 L/min you needed becomes your case drain flow. (You could quite easily measure your case drain flow using a measuring flask and a stopwatch.)

This case drain oil came from your 300 bar supply so will be warm because it will have reduced its pressure to 0 bar by passing through the clearances in the motor. Assume a temperature rise of 6.8 deg C per 100 bar which means your case drain oil “source” is now 20.4 deg hotter than the supply.

The theoretical shaft output power from your remaining 400 L/min at 300 bar should be 200 kW but your mechanical efficiency is 97% so you lose 3% of 200 kW, i.e., 6 kW. This heat has to be carried away by your 12 L/min case drain flow.

The specific heat capacity of a typical mineral oil is 1.67 J/g/K and the typical density is 0.88 g/cc. Your flow of 12 L/min is 200 cc/sec so that’s 176 g/sec. Your heat input is 6 kW, i.e., 6000 J/sec so the energy input to the oil is 34 J/g. The temperature rise because of this energy input will be 34/1.67 = 20.4 deg C (yes, it’s the same as the temperature rise from the pressure drop but that’s because both of your efficiencies are numerically equal).

Your case drain oil will be approximately 41 deg C hotter than your input flow. If your cooler doesn’t come on until the bulk oil temperature reaches 60 deg C then that’s you breaking the 100 deg C mark.

As I stated earlier, this is a horribly simplistic calculation because no account is taken of: the compressibility of the oil, heat taken away from the motor by the outlet [return] flow, conduction through whatever the motor is bolted to, convection from the motor case etc. All I wanted to do was show you how the numbers stack up.

If you were to apply some motor case flushing flow this would be taken from the low pressure side of the circuit (say 20 bar) which would be from the output side of the motor. So let’s assume a bulk oil temperature of 60 deg C and the temperature of the motor supply oil would be about the same. Call the motor outlet temp 62 deg C so that will give you a flushing flow inlet temp of about 64 deg C. A flushing flow of, say, 20 L/min at this 64 deg C would add to your case drain “source” flow of 12 L/min at 80.4 deg C to give you 32 L/min at ~70 deg C. This combined flow now has to absorb the 6 kW wasted mechanical power; the resulting temperature rise will be ~7.6 deg C and your case drain oil would be coming out of the motor at just under 80 deg C.

If you added a separate hot oil shuttle valve to your motor circuit with an adjustable throttle valve on the shuttle outlet you could vary the amount of flushing flow until you brought the case drain exit oil temperature back into line. Do check, however, that your boost pump has enough capacity to do this – if you take too much flow off the motor outlet circuit then the boost pressure may drop too low for the pump’s comfort. Alternately, you could redirect some of the flow from your existing purge valve if it is close enough to the motor. Remember that increasing the case flushing flow will decrease the flow through your cooler so its cooling performance will be reduced. Is it possible that you could redirect the motor case drain flow through the cooler as well (as long as the motor case and pump case can take the cooler back pressure)? If you could do this the cooler performance would increase because of the greater flow and the greater average temperature difference.

Since actual heat transfer (24.48 kW) is significantly greater than the calculated heat generated through volumetric inefficiencies (6.96 kW), this would suggest that there is a problem within the hydraulic motor and the motor should be replaced.

Your colleague seems to be taking everything as conservative. You say the Vol eff is 97%, so flow is less. Also density will be lower at higher temp, say 0.8. This gives 0.16kg/sec. Can"t you measure actual case drain flow then weigh it??

Reference the following point: "This case drain oil came from your 300 bar supply so will be warm because it will have reduced its pressure to 0 bar by passing through the clearances in the motor. Assume a temperature rise of 6.8 deg C per 100 bar which means your case drain oil “source” is now 20.4 deg hotter than the supply."

Can you confirm how you estimated the 6.8 deg C per 100 bar. I have been trying to understand the relationship between reducing pressure and a temperature increase. Or how can I estimate the heat generated through a pressure reduction, do i need to know delta T to calculate this?

Suppose you had a flow of 60 L/min at 100 bar, the [theoretical] power you would need to pump this would be: 60 x 100 / 600 = 10 kW. If you then let this source of pressurised oil de-pressurise by passing over a jet (or some other clearance passage within a hydraulic component) then no “real” work will have been done and the original power input of 10 kW will all be converted to heat.

60 L/min = 1 Litre/sec = 0.88 kg/sec (assuming that the fluid density is 880 kg/m³). Your input power of 10 kW is 10 kJ/sec so you will be putting 10 kJ/sec into 0.88 kg/sec, i.e., 10 kJ into 0.88 kg. This equates to 11.36 kJ/kg.

The specific heat capacity of the oil is typically 1.67 kJ/kg/K so the temperature rise will be 11.36/1.67 = 6.8 K for a 100 bar pressure drop. If the pressure drop were higher the energy input would be higher and the temperature rise would be higher. Similary a lower pressure drop creates a lower temperature rise. To be more specific the temperature rise is 0.068 K/bar.

I’ve used real numbers in this example, but you should be able to see that the flow rate is actually of no consequence. If the flow had been 120 L/min then the input power would have been 20 kW … but this would have been dissipated into 1.76 kg/sec so the specific energy input would still have been 11.36 kJ/kg.

Feel free to fiddle with the numbers to take account of fluid compressibility, changes of density with temperature and pressure, changes of specific heat capacity with temperature and pressure etc. but I don’t believe it’s worth the effort.

If your motor is new then you can think of it behaving just like a rebuilt engine that hasn"t fully run in yet. It will be "tight" so there will be a poor mechanical efficiency and a good volumetric efficiency. The overall efficiency may still be good [this is a measure of the motor"s abilty to convert the hydraulic input power (pressure x flow) into mechanical output power (torque x shaft speed)]. The [poorish] mechanical efficiency means that some of the mechanical power is lost inside the motor - but the [high] volumetric efficiency means that there isn"t much leakage flow available to take the wasted power away - hence your high case drain temperature.

Overheating isa frequent problemwithin hydraulic systems that may be determined by specific components. Thisinternal problem lies within the pump and causes a hydraulic system to overheat in the following ways:

Contaminated hydraulic fluid is a common cause for a Hydraulic system to overheat. This can occur when the container is not sealed properly which causes dust, dirt,debris,or moisture to contaminate the fluid.With hydraulic systems running at higher pressures and more efficiently than ever before, it is important tomonitorthe cleanliness of one’s hydraulic fluid. Reducing contamination can decrease damage andwillallowoneto get the most out oftheirequipment.

Wrong valve calibration could resultin pressure difficulties which can cause a hydraulic system to overheat. The main cause of this is when a facility’s plant design changes and maintenance recalibrate the pressure relief valves for the updated operating pressure. If maintenance adjusts the pressure,and it stilldoes notsolve the problem, the pressure relief valve may have to be replaced entirely. Erosion to a valve is a common occurrence as dirt and debris settle and collectthroughout time. Maintaining the correct pressure will help your system keep up with production and not slow down.

Aeration in a hydraulic system can bea common issueand is caused by an outside air leak in the suction line.The pressure used in the suction line of hydraulic systems is below atmospheric pressure, so oilcannotleak out, but air can leak in.This will occur when there are loose, leaky seals and fittings which will allowtheair to seep in.Aeration can have severalnegative effectson top of overheatingsuch as increasedpump cavitation, excessive noise, and loss of horsepower.Some symptoms of Aeration may include foaming of the fluid, irregular movements, and banging and or loud clicking noises as the hydraulic system compresses and decompresses.

A blocked heat exchanger is significant toheating one’s hydraulic system, while cooling it down is just as important.Aninfrared thermometer isan effective wayto checkthe temperatureof a heat exchanger. Theadjustments can be made according tothedesign of theflow rateof oil.Make sure to replace the fluid fitterslocatedin the pumpon a regular basis to ensure theywill not get blocked andoverheat.

Oil Type plays a critical role inany hydraulic system. The wrong oil will not only affect the performance of the system but also cut down the lifespan of the machine. Theoil Viscositydeterminesthe maximum and minimum temperatures in which a hydraulic system can safelyoperate.Thin oils have a lowviscosity andflow more easily at low temperaturesthanthicker oils that have a higherviscosity.If the oil is too thin it can cause internal friction whichcreates heat and cancausethe system to overheat.

Low reservoir fluid is a common cause ofoverheating in hydraulic systems as itreleasesbuilt-upheatfrom the machineintothe fluid. Not having enough reservoir fluid cancontribute tocavitation andultimate damage to the pump.

Hydraulic pump failure candamage the entire hydraulic system.When a pump fails,debris, dirt, and grime kick out downstreamand can affect theoil,filter,valves, fluid, and actuator.Contactour KICK@$$ hydraulic system repair professionalsat Allied Hydraulic to avoid these problems.

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 hydraulic pumps on construction equipment are critical components of the machines and even though they are often designed to work under vigorous and intense conditions, no pump will last forever. Discovering a problematic pump can be complicated as the effects might seem to originate in other connected parts, and, if failures are gradual, the cascading effects of a pump failure can spread throughout a machine.

To help in your diagnosis — and with a small dash of preventive maintenance — we’ve put together this basic, short list of common pump problems and their causes.

Not every hydraulic pump on a machine is simple to inspect, but this Volvo main hydraulic pump on a EC220B-LC excavator sits behind a quick access door so an operator can check it often.

A failing hydraulic pump can be a long and subtle process, a sudden and catastrophic calamity, and all shades in-between, but often a perceptive operator will notice the signs of a pump failure in advance. It might take a few minutes of stopping and inspecting, but knowing what to watch for and taking the time to inspect your hydraulic pumps can often pay off in the long run and lead to fast and simple fixes, instead of prolonged and labor-intensive downtimes.

A hydraulic pump is often secured behind a door or guard or integrated deeply into the body of a machine, but taking the time to inspect the pump for the presence of oil (or oil and dirt clumping) can lead to the early discovery of problems. If the issue is simply a loose connection, a quick tightening can often stop a small issue from growing.

Since a hydraulic pump has both seals to prevent fluid from exiting the pump and also fluid from prematurely entering from one chamber to the next, failing seals can be both internal and external. Spotting an exterior leak is, of course, simpler, but being aware of where seals exist inside the pump can also help you diagnose a failing internal seal.

The most frequently noticed indication of a failing pump is often the start of a new sound coming from the hydraulic pump. An experienced operator will often immediately know and recognize a pump that is indicating issues through sounds, but for many it can be harder to pinpoint.

A problem with a pump can cause it to simply become louder in its operations, develop a whining sound, or even create a knocking sound. The sounds can indicate a number of problems, but often the cause is either cavitation or aeration in the pump.

Over long spans of work and under intense conditions, a hydraulic pump will often heat up, but excessive heating is often a sign of internal issues in the hydraulic pump. Checking a hydraulic pump for excess heat should always be done with safety in mind and with a secure machine and proper protective equipment. Periodically ensuring a hydraulic pump isn’t overheating allows an operator to discover if the pump is under undue strain and on a path to failure.

Overheating in a hydraulic pump can also cause fluid to thin, cause internal components to more rapidly degrade, and introduce dangerous working conditions to the machine. Overheating in a pump is both a sign of current trouble and a cause of other growing problems.

Unexpected and non-fluid movement of parts can be caused by issues with the hydraulic pump, but since the culprit can be a number of other parts in the system, diagnosing pump issues from these movements isn’t always simple. Still, if you do notice non-uniform movements in your machine, taking time to rule out the hydraulic pump is important.

A main hydraulic pump, like this one from a Komatsu PC400LC-6 excavator, comes with a working life and will need to be replaced or rebuilt at some time. This one is fresh from an H&R Recon and Rebuild shop and is headed to a customer.

Knowing some of the common causes of hydraulic pump failures is a proven way of proactively discovering developing issues and correcting them before they become disastrous to the pump and the machine.

The internals of a hydraulic pump are designed to work with fluid that meets exacting specifications. When hydraulic fluid is contaminated it can lead to issues developing in the pump, force the pump to work harder, and cause the pump to work erratically. One common culprit for contamination is water, and it can quickly lead to increased corrosion, changes in viscosity that lead to inefficiencies, and the inability to properly regulate heat in the pump.

Other debris, either introduced from outside or from the degradation of internal elements, can also lead to issues in the pump and signal failing seals or other parts.

A hydraulic pump is often containing a high level of pressure and as this pressure exerts force on seals in the pump, the seals can begin to leak or fail. Even minor leaks in seals can lead to loss of fluid and create issues in the system. Leaks can be both external and internal. For an internal leak, fluid will move from one part of the pump to another in unintended ways and force inefficiencies into the pump as it has to work harder to compensate.

While many hydraulic pumps are built to stand up to tough and continuous working conditions, every hydraulic pump is designed with an upper limit. Every time a hydraulic pump is subjected to overpressuring and overloading beyond what the manufacturer has specified, the pump is more prone to damage.

All hydraulic oil has a defined amount of air dissolved in it, but increases to this amount can lead to inefficiencies in the pump and force the pump to work harder or erratically. An increase in air can also happen inside the pump and create similar problems. Even though the pump and hydraulic system have mechanisms in place to regulate air in the system, if excess air is introduced the system should be returned to a balanced system before prolonged use of the pump.

The hydraulic system on a construction equipment machine is designed to work within defined parameters. Operating a machine with too little oil or too much oil for even the briefest amount of time can cause the pump to overwork, lead to increases in working temperatures, or create conditions for non-uniform movement. The exact type of oil used — matched to the machine and the working environment — can also impact how the hydraulic pump operates.

A simple and well-practiced maintenance plan can help prevent issues from developing and even discover issues early, leading to shorter and less costly downtimes.

The operator’s guide of your machine will define the hydraulic oil change schedule and adhering to that schedule can extend the life of your hydraulic pump. When oil is changed, take time to examine the spent oil for signs of debris

The operator’s guide of your machine will indicate the correct oil to use in your machine, but operators should also be aware of the conditions they are working under and be mindful if oil should be updated to match those conditions.

Keeping a pump on a hard-working machine looking new every day is nearly impossible, but routinely peeling back dirt, grime, and oil can help catch issues early.

No one wants to take a machine out of work for cleaning, but keeping the machine clean and ensuring pumps are not covered in mud, dirt, or other debris can allow them to be inspected more easily and avoid contamination and overheating.

The hydraulic hoses connected to a hydraulic pump can wear out over time and ensuring they are well-maintained can help you avoid the introduction of debris and even catastrophic issues in the case of sudden failures.

If a hydraulic pump fails on your machine, taking time to ensure you properly diagnose why and how the failure occurred will help you avoid repeating the failure with your replacement pump. Even if the pump failed simply from prolonged use and age, taking time to confirm that can lead to insights about how to extend the life of the next pump.

A hydraulic pump on an excavator, wheel loader, dozer, or articulated truck can be an often ignored component of the machine — until it starts to act up and cause issues. If problems have brought a pump to the forefront of your mind, hopefully, this short guide has helped simplify your pump problem solving.

If you find yourself in need of a replacement hydraulic pump, our Parts Specialists are always here to help. As a supplier of new, used, and rebuilt hydraulic pumps and with our deep inventory of parts, our Parts Specialists can often find the perfect solution to get a customer back up and running quickly. Simplify your search and give them a call.

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The look and design of a hydraulic pump is customized to fit the machine and the available space. This main hydraulic pump is freshly reconditioned from a Kobelco SK160LC-VI excavator.

Hydraulic pumps come in a wide range of shapes and sizes. This large Volvo main hydraulic pump requires assistive overhead cranes and forklifts to move around the warehouse.

This article is part of the H&R Construction Equipment Parts How To series, designed to give readers and viewers a brief glimpse of the work of our Recon and Rebuild team or to provide basic maintenance and help tips. Whether you’re rolling up your sleeves and about to get your hands greasy or you’re just looking for a better understanding of a part, please practice proper safety protocols and understand this is only a basic guide. Consult a trained professional before performing any unfamiliar tasks.

Everyone knows that contamination can be catastrophic to a hydraulic system. But heat can also be detrimental to hydraulic fluid and the components within that system.

Heat contamination reduces oil viscosity, which in turn reduces the fluid’s ability to lubricate components. This thinning of the oil causes surface-on-surface wear. Without proper viscosity levels, as components rub against each other — such as a wear plate and the slippers on a piston pump — they wear at accelerated rates.

This wearing also softens metals, which in turn increases the rate of wear. For example, anywhere there’s metal rubbing on and near to other pieces of metal (even if it’s two different materials such as bronze or stainless) as the metal heats up, it becomes softer and it wears away more quickly. This problem is exacerbated if other forms of contamination are present.

Additionally, heat can break down system seals. As they break down, flecks of rubber can enter the system, causing internal contamination. And, if a seal fails, external contamination will easily enter through cylinder rods.

Heat enters a hydraulic system in multiple ways. One culprit is ambient heat. For example, you may have a blast furnace dipping molten metal into a ladle. It is imperative that the hydraulic actuators and the oil used within them are designed for that type of environment.

Another thing to be aware of is internally generated heat; this often is generated from piston pumps, inefficient gear pumps or friction created by other internal components. For example, while useful in specific applications, low-speed, high-torque motors may only have a 60-70% efficiency rating. This means 30 to 40% of the system energy is wasted as pure heat. This internal heat reduces lubrication, increasing friction and reducing lubricity. This may eventually cause the motor to wear out.

So how to do you filter out or remove heat from a system? First, you should try to design a system that doesn’t create it in the first place. Second, in regular maintenance, always keep an eye on the reservoir levels. You should have three times the pump capacity available in the reservoir. Ensure also that the reservoir is clean and not near heat sources (such as direct sunlight or machines that generate heat).

Finally, if there is any device that could be considered a heat filter, it would be a cooler or heat exchanger, which uses water or air to bring hydraulic fluid temperature down. Several types exist.

The first is a shell and tube heat exchanger, in which coolant water flows through internal system ports and tubing while the warmer hydraulic fluid circulates through others. The heat is transferred from one fluid to the other, thus bringing the overall fluid temperature down.

Air coolers can also be used. While not as effective, they are sufficient and often easier to use. These use a fan and radiator-type cooler, and often can be driven by hydraulic motors, simply to force cold air over the hot fluid inside.

In many factories, the hydraulic pump is the heart of the operation — and hydraulic pump failure can cause huge problems. But why do hydraulic pumps break? In order to avoid hydraulic pump failure, it’s helpful to know what some hydraulic pump failure causes are.

Before getting into the reasons hydraulic pumps break, it’s important to know the signs that your hydraulic pump is broken or in danger of breaking. Some of these signs include:

Noisy System:All mechanical systems make some noise, and hydraulic systems are no exception. But if you are hearing very loud banging or knocking, there’s a good chance that your system is experiencing aeration or cavitation, which could lead to pump failure.

High Temperature:If your hydraulic system is exceeding the recommended temperature level of 82 degrees Celsius, this could be due to a buildup of debris in the filters preventing the system from dissipating heat. This is a problem you will want to address quickly, as high heat can damage your system.

Slow System:If your system isn’t operating as quickly as it’s supposed to, you definitely have a problem. A slow hydraulic system means a loss of flow, which typically means internal leakage.

The major cause of hydraulic pump failure is called fluid contamination. This is an invasion of the hydraulic fluid by foreign materials. Hydraulic pumps and valves are only designed to carry hydraulic fluid, and anything else in them will damage the system, especially since this foreign debris may remain in the system and continue to damage the valves and pipes.

Aeration:Air in the hydraulic fluid can create problems when put under pressure by the pump. When this happens, they can implode and dislodge debris, causing contamination and raising the temperature inside the pump.

Cavitation:Cavitation is a situation where the hydraulic fluid doesn’t fully take up the space in the pump because of unusually high fluid viscosity, an intake line that is too long or an overfast pump, among other reasons. It can lead to problems similar as aeration.

Excessive Heat:An overheated hydraulic system can cause some massive problems for your hydraulic system. It can damage seals, degrade the hydraulic fluid and otherwise compromise the system.

Overpressurization:Hydraulic pump systems are very sensitive and should only operate under specific conditions, including precise pressure levels. Exceeding recommended pressure levels puts undue pressure and wear on the system and can cause it to fail more quickly.

The best way to avoid hydraulic system failure is to keep your system clean. Remember: fluid contamination is the main precursor to hydraulic system failure, so keeping those contaminants out of your system is your best chance to maintain healthy hydraulics. This means high-quality filters in your system that you inspect regularly and change when necessary.

The other major way to keep your hydraulic system up and running is by keeping the components cool. An overheated system can result in real problems, and you may not notice the effects until it is too late. You’ll also want to make sure your system is operating under the right pressure specifications.

A well-maintained hydraulic system can last a long time and be extremely efficient. Although there are many problems that can occur with a hydraulic system, most can be avoided with proper care, and the benefits of having a good hydraulic system for your business can be great — well worth taking good care of your system.

Part of that care is taking quick action when necessary. If you suspect that there is a problem with one or more components of your hydraulic system, the best thing to do is have a professional inspect it and repair any faulty parts that are failing or at risk of failing. The longer you let a hydraulic system problem go without addressing it, the worse the failure will be when it does happen.

Global Electronic Services has factory-trained, certified technicians who are well-versed in hydraulic systems and hydraulic problems. If you’re delaying repairing your hydraulics because you’re afraid of taking them offline, you should know that Global Electronic Services can complete your repair in a matter of days. For more information, call 877-249-1701 or contact Global Electronic Services online.

Be sure to visit us online at gesrepair.com or call us at 1-877-249-1701 to learn more about our services. We’re proud to offer Surplus, Complete Repair and Maintenance on all types of Industrial Electronics, Servo Motors, AC and DC Motors, Hydraulics and Pneumatics. Please subscribe to our YouTube page and Like Us on Facebook! Thank you!

Heat is a form of energy associated with the motion of atoms or molecules in solids and capable of being transmitted through solid and fluid media by conduction, through fluid media by convection and through empty space by radiation.

For our use in hydraulic applications, we need to translate the definition above into a more workable statement that will help us better understand the physics behind this phenomenon called heat. Something like “Anytime fluid flows from a high pressure to a lower pressure, without producing mechanical work output, heat is generated.”

The use of flow controls, proportional, reducing, relief, reducing/relieving, counterbalance and servo valves all create a pressure drop in order to do their job.

Incorrect sizing of fluid conductors can cause the generation of heat. For example, with ½ inch OD pipe, a flow rate of 10 GPM generates heat at the rate of about 25 BTU/FT-HR. Doubling the flow rate to 20 GPM increases heat generation 8 times to about 200 BTU/FT-HR. Here are some rules of thumb when sizing hydraulic conductor velocities:

As pumps wear, the internal leakage or “slippage” increases. On fixed displacement pumps this leakage flows from the high-pressure outlet back through the pump to the low-pressure inlet. In a pressure compensated pump this flow is forced out through the case drain. As this occurs fluid is taken from a high pressure to a low pressure without doing any mechanical work thereby creating heat.

Pulsating accumulators may develop high pressures on the gas side. This heat can transmit back into the oil raising the temperature and creating a hot spot in your hydraulic system.

When a load is lifted hydraulically, potential energy is stored in the load. Release of the load usually involves non-regenerative throttling, which generates heat.

Heat has many detrimental effects on the hydraulic system components. But the most detrimental effect of heat is the breakdown of the oil. Oil temperatures should be maintained at 120°F for optimum performance, and should never be allowed to exceed 150°F. At high temperatures, oxidation of the oil is accelerated. This oxidation shortens the fluid’s useful life by producing acids and sludge, which corrode metal parts. These acids and sludge clog valve orifices and cause rapid deterioration of moving components. The chemical properties of many hydraulic fluids can change dramatically by repeated heating/cooling cycles to extreme temperatures. This change or breakdown of the hydraulic media can be extremely detrimental to hydraulic components, especially pumping equipment. Another effect of heat is the lowering of the oil’s viscosity and its ability to lubricate the moving parts of the pump and related hydraulic equipment effectively.

A = the surface area of the reservoir in sq. ft. The surface area of the bottom of the reservoir can only be used in the calculations if the tank sits 6.0 inches off of the ground.

This can be accomplished by adding a solenoid vented relief valve on fixed displacement pumps and a solenoid vented control on pressure compensated pumps. This will remove the high-pressure component of the definition above.

Heat exchanges can be used to remove the excess heat in a hydraulic system. The implementation of heat exchangers has many variables that need to be taken into account. Rules of thumb when sizing a heat exchanger are as follows:

Multiply the input horsepower (motor hp) by the percentage listed above that best describes the system parameters. For example, if your system is a simple circuit with fluid motors and has an electrical motor input horsepower of 30hp: 30hp X 0.31 = 9.3hp

The tank needs to dissipate at least 9.3 horsepower or the system will overheat. Another rule to keep in mind is if your system pressure is above 1000 PSI and your tank is sized for 3 times or less pump output you WILL need a heat exchanger.

There are many more aspects of thermal characteristics within a hydraulic system than this paper was meant to cover. With this information, you should be able to make educated decisions when working with an existing system or new design in order to combat heat generation. With this information you should also feel comfortable calling a specialist to discuss ways to minimize the heat you may experience in your system. When in doubt, consult your local fluid power professional

Note: “Tech Tips” offered by Flodraulic Group or its companies are presented as a convenience to those who may wish to use them and are not presented as an alternative to formal fluid power education or professional system design assistance.

When a hydraulic system fails, finding the source of the problem can be a challenge. Though hydraulic systems primarily consist of a sump, motor, pump, valves, actuators and hydraulic fluid, any of these parts could be the source of failure. That"s not to mention the additional potential for failure through human error and faulty maintenance practices. If your system fails, you need to know why it fails, how to find the failure and how to keep it running smoothly in the future, all while keeping personnel safe.

It"s often easy to tell when a hydraulic system fails — symptoms can include high temperatures, low pressure readings and slow or erratic operation are glaring problems. But what are the most common causes of hydraulic systems failures? We can trace most hydraulic issues back to a few common causes, listed below.

Air and water contamination are the leading causes of hydraulic failure, accounting for 80 to 90% of hydraulic failures. Faulty pumps, system breaches or temperature issues often cause both types of contamination.

Air contamination is the entrance of air into a hydraulic system and consists of two types — aeration and cavitation. Both can cause severe damage to the hydraulic system over time by wearing down the pump and surrounding components, contaminating hydraulic fluids and even overheating the system. Although we are not pump manufacturers, we know it is essential to be aware of these types of contamination and how to identify their symptoms.

Cavitation:Hydraulic oil consists of about 9% dissolved air, which the pump can pull out and implode, causing pump problems and damage to the pump and to other components in a hydraulic system over time. You can identify this problem if your hydraulic pump is making a whining noise.

Aeration:Aeration occurs when air enters the pump cavity from an outside source. Usually, loose connections or leaks in the system cause this issue. Aeration also creates a sound when the pump is running, which sounds like knocking.

Water contamination is also a common problem in hydraulic systems, often caused by system leaks or condensation due to temperature changes. Water can degrade hydraulic components over time through oxidation and freeze damage. A milky appearance in hydraulic fluid can help you identify water contamination.

Fluid oxidization: Extreme heat can cause hydraulic fluid to oxidize and thicken. This fluid thickening can cause buildups in the system that restrict flow, but can also further reduce the ability of the system to dissipate heat.

Fluid thickening:Low temperatures increase the viscosity of hydraulic oil, making it harder for the oil to reach the pump. Putting systems under load before the oil reaches 70 degrees or more can damage the system through cavitation.

Fluid levels and quality can affect hydraulic system performance. Low fluid levels and inappropriate filtration can result in air contamination, while fluid contamination can cause temperature problems. Leaks can further exacerbate both issues.

Using the correct type of fluid is also essential, as certain hydraulic oils are compatible with specific applications. There are even oil options that offer higher resistance to temperature-related problems. Some oils even offer anti-wear and anti-foam additives to help prevent against wear and air contamination, respectively.

Human error is the base cause of many hydraulic system problems. Some of the most common errors that may result in your hydraulic pump not building pressure include the following.

Faulty installations: Improper installation of any component in a hydraulic system can result in severe errors. For example, the pump shaft may be rotating in the wrong direction, negatively affecting pressure buildup, or pipes may be incorrectly fitted, resulting in leaks.

Incompatible parts: An inexperienced installer may put mismatched components together, resulting in functional failures. For example, a pump may have a motor that runs beyond its maximum drive speed.

Improper maintenance or usage:Using systems outside their operational capabilities or failing to perform regular maintenance are some of the most common causes of hydraulic system damage, but are easy to rectify through updated maintenance policies and training.

The sources of system failures can be tricky to identify, but some hydraulic troubleshooting steps can help narrow down the options. So how do you troubleshoot a hydraulic system? Here are some of the fundamentals.

Check the pump: Take the pump assembly apart and assess all parts to ensure that they are functional and installed correctly. The most common problem areas include the pump shaft, coupling and filter.

Check the fluids:Check the level, color and viscosity of the hydraulic oil to ensure it meets specifications and has not become contaminated. Low hydraulic fluid symptoms include pressure or power loss. When in doubt, drain and replace the fluids.

Check the seals: Look for evidence of any fluid leakage around your hydraulic system"s seals, especially the shaft seal. Leakage can indicate worn-out or blown seals that can cause malfunctions with pumps, motors and control valves.

Check the filters: Ensure filters are clear of plugs and blockages. Common clogged hydraulic filter symptoms include sluggish operation and noisy operation.

Check valves and lines: Observe all lines for potential leaks, and tighten every connection point. Also, check the relief valve for any signs of damage.

Run the system: When you have completed all these essential checks, turn on the system and monitor it for pressure and temperature fluctuations, as well as abnormal sounds. If all seems well, check your pressure sensor for potential failure.

Hydraulic system issues are inevitable at some point. However, simple steps can help you avoid these issues and increase the longevity of your hydraulic system. On top of effective troubleshooting, you can preve