why is my hydraulic pump overheating price

Overheating ranks No. 2 in the list of most common problems with hydraulic equipment. Unlike leaks, which rank No. 1, the causes of overheating and its remedies are often not well understood by maintenance personnel

Heating of hydraulic fluid in operation is caused by inefficiencies. Inefficiencies result in losses of input power, which are converted to heat. A hydraulic system’s heat load is equal to the total power lost (PL) through inefficiencies and can be expressed as:

If the total input power lost to heat is greater than the heat dissipated, the hydraulic system will eventually overheat. Installed cooling capacity typically ranges between 25 and 40 percent of input power, depending on the type of hydraulic system.

How hot is too hot? Hydraulic fluid temperatures above 180°F (82°C) damage most seal compounds and accelerate degradation of the oil. While the operation of any hydraulic system at temperatures above 180°F should be avoided, fluid temperature is too high when viscosity falls below the optimum value for the hydraulic system’s components. This can occur well below 180°F, depending on the fluid’s viscosity grade.

To achieve stable fluid temperature, a hydraulic system’s capacity to dissipate heat must exceed its heat load. For example, a system with continuous input power of 100 kW and an efficiency of 80 percent needs to be capable of dissipating a heat load of at least 20 kW. Assuming this system has a designed cooling capacity of 25 kW, anything that increases heat load above 25 kW or reduces the cooling system’s capacity below 25 kW will cause the system to overheat.

Consider this example. I was recently asked to investigate and solve an overheating problem in a mobile application. The hydraulic system was comprised of a diesel-hydraulic power unit, which was being used to power a pipe-cutting saw. The saw was designed for sub-sea use and was connected to the hydraulic power unit on the surface via a 710-foot umbilical. The operating requirements for the saw were 24 GPM at 3,000 PSI.

The hydraulic power unit had a continuous power rating of 37 kW and was fitted with an air-blast heat exchanger. The exchanger was capable of dissipating 10 kW of heat under ambient conditions or 27 percent of available input power (10/37 x 100 = 27). The performance of all cooling circuit components were checked and found to be operating within design limits.

At this point it, was clear that the overheating problem was being caused by excessive heat load. Concerned about the length of the umbilical, I calculated its pressure drop. The theoretical pressure drop across 710 feet of ¾-inch pressure hose at 24 GPM is 800 PSI. The pressure drop across the same length of 1-inch return hose is 200 PSI. The theoretical heat load produced by the pressure drop across the umbilical of 1,000 PSI (800 + 200 = 1,000) was 10.35 kW. This meant that the heat load of the umbilical was 0.35 kW more than the heat dissipation capacity of the hydraulic system’s heat exchanger. This, when combined with the system’s normal heat load (inefficiencies) was causing the hydraulic system to overheat.

Hydraulic systems dissipate heat through the reservoir. Therefore, check the reservoir fluid level and if low, fill to the correct level. Check that there are no obstructions to airflow around the reservoir, such as a buildup of dirt or debris.

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 and temperature of both the hydraulic fluid and the cooling air or water circulating through the exchanger. Check the performance of all cooling circuit components and replace as necessary.

An infrared thermometer can be used to check the performance of a heat exchanger, provided the design flow-rate of hydraulic fluid through the exchanger is known. To do this, measure the temperature of the oil entering and exiting the exchanger and substitute the values in the following formula:

For example, if the measured temperature drop across the exchanger is 4ºC and the design oil flow-rate is 90 L/min, the exchanger is dissipating 10 kW of heat. Relating this to a system with a continuous input power of 100 kW, the exchanger is dissipating 10 percent of input power. If the system is overheating, it means that either there is a problem in the cooling circuit or the capacity of the exchanger is insufficient for the ambient operating conditions.

On the other hand, if the measured temperature drop across the exchanger is 10ºC and the design oil flow-rate is 90 L/min, the exchanger is dissipating 26 kW of heat. Relating this to a system with a continuous input power of 100 kW, the exchanger is dissipating 26 percent of input power. If the system is overheating, this means that the efficiency of the system has fallen below 74 percent.

Where there is a pressure drop, heat is generated. This means that any component in the system that has abnormal, internal leakage will increase the heat load on the system and can cause the system to overheat. This could be anything from a cylinder that is leaking high-pressure fluid past its piston seal, to an incorrectly adjusted relief valve. Identify and change-out any heat-generating components.

A common cause of heat generation in closed center circuits is the setting of relief valves below, or too close to, the pressure setting of the variable-displacement pump’s pressure compensator. This prevents system pressure from reaching the setting of the pressure compensator. Instead of pump displacement reducing to zero, the pump continues to produce flow, which passes over the relief valve, generating heat. To prevent this problem in closed center circuits, the pressure setting of the relief valve(s) should be 250 PSI above the pressure setting of the pump’s pressure compensator (Figure 1).

Continuing to operate a hydraulic system when the fluid is over-temperature is similar to operating an internal combustion engine with high coolant temperature. Damage is guaranteed. Therefore, whenever a hydraulic system starts to overheat, shut it down, identify the cause and fix it.

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.

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.

When hydraulic oil is getting overheated, there could be several common causes that also cause the system to overheat. First, it is crucial to understand the type of hydraulic system you are using to begin troubleshooting why the system is overheating.

The first cause of hydraulic oil overheating is when the hydraulic equipment system parts and components are nearing the end of their useful lifespans. As they degrade, due to increased internal leakage, they have to work harder to maintain the desired system pressure.

For example, your hydraulic pump is wearing out and needs to be replaced. Due to internal wear pressurised fluid escapes from the high pressure side to the low pressure side generating heat increasing the temperature of the hydraulic fluid and causing circuit overheating.

It is understood that you may want to make system upgrades or changes to customize the system to reflect your specific needs. However, when you do not consider the entire system, it can cause the system to work hard, give off more heat, and increase hydraulic oil temperatures, leading to circuit overheating.

For instance, you may want to increase the fluid flow rate through the system. However, you did not account for the size of hoses and tubing to accommodate the higher flow rates. As a result, the system has to work hard to force the increased flow rates through incompatible hoses and tubes, resulting in more heat generation and fluid overheating.

Tweaking your hydraulic system is perfectly acceptable to optimize its performance. However, where many people go wrong is they only adjust one part of the system and fail to think about how the adjustment will impact other parts of the system.

For example, suppose you make an adjustment to the pump compensator and increase the pressure yet fail to also make a similar adjustment to the relief valve. In this instance the relief valve will blow off more frequently generating more heat and therefore increasing the circuit fluid temperature.

Every component in a hydraulic system imposes a load on the pump, this is referred to as the pressure drop across the particular component. The figure will vary depending upon the flow rate and the energy lost from the fluid due to the pressure drop is converted into heat. If the overall pressure drop across all the components in the circuit unexpectedly increases so the heat generated across the circuit will also increase.

If the fluid is not cooled to compensate for this the fluid temperature continues to increase as the other parts and components generate excessive heat.

If there is dirt, sludge, debris, or water in the hydraulic fluid, the system will generate more heat as it attempts to compensate for the contaminants and push the fluid through the system. Therefore, it is always vital to check your fluid for contamination and change it and or improve fluid filtration when required.

After troubleshooting overheating problems, if you have determined it is not due to the four common causes mentioned above, then there are two general ways you can resolve fluid overheating problems. You can either increase the reservoir capacity to dissipate heat or decrease the amount of heat being generated by the system.

Another way to increase the heat dissipation is to inspect the current heat exchangers, if they are being used, and make the appropriate adjustments. In some cases, you may want to install additional heat exchangers to help reduce the fluid temperature.

To find hydraulic parts, components, and accessories to help you resolve hydraulic oil overheating problems, or if you require assistance in troubleshooting system overheating, please feel free to contact White House Products, Ltd. at +44 (0) 1475 742500 today!

?I get e-mails like this all the time. I never find time to read them. I decided to read Issue #30 and I couldn"t put it down. I"ll make time from now on.?

?I just love this newsletter. As a Hydraulics Instructor for Eaton, I make copies and distribute them to my students as I address various topics. Please keep "em coming.?

Hyundai hydraulic pumps are integral parts of excavators. The company is the third largest manufacturer in the world. As one of the leading brands, Hyundai has been popularized after producing high quality and durable products over time.

An excavator Hyundai hydraulic pump can overheat for a variety of reasons. The most common cause is actually running the pump at too low of an RPM. When the pump is not turning fast enough, it can’t move the oil through the system quickly enough and it starts to overheat. Another common cause is a blockage in the system somewhere. This could be a blockage in the suction line, return line, or even in the pump itself. If there is a blockage, the oil can’t flow properly and it will start to overheat.

If your excavator Hyundai hydraulic pump is overheating, there are a few things you can do to try and fix the problem. First, check the RPM of the pump. If it is running too low, increase it until it is running at the proper speed. Next, check for any blockages in the system. If you find one, clean it out and see if that fixes the problem. Finally, if neither of those two things works, you may need to replace the pump itself.

There are many potential causes of an excavator Hyundai hydraulic pump overheating. The most common cause is a loss of hydraulic fluid due to a leak in the system. Other causes can include a build-up of dirt and debris in the system, or a problem with the pump itself.

If you suspect that your excavator’s hydraulic pump is overheating, the first step is to check for leaks. If you find a leak, make sure to repair it as soon as possible. If there is no leak, then you will need to clean out the system to remove any dirt or debris that may be causing the problem.

If you are still having problems with your excavator’s hydraulic pump overheating, it may be necessary to replace the pump itself. This is a more complex repair, so it is best to consult with a qualified mechanic or dealer before proceeding.

There are several potential causes of an excavator Hyundai hydraulic pump overheating, but the most common cause is simply because the pump isn’t getting enough oil. This can happen for a variety of reasons, such as a leaking oil line or an incorrect amount of oil being used. Another potential cause is that the pump isn’t getting enough cooling water, which can be caused by a clogged water filter or an insufficient water supply. Whatever the cause, it’s important to get the problem fixed as soon as possible to avoid damage to the pump.

The Hyundai hydraulic pump is located in the engine bay of the excavator. It is responsible for providing hydraulic pressure to the excavator’s hydraulic system. If the pump overheats, it can cause damage to the hydraulic system and potentially lead to a loss of excavator performance. There are a few things that you can do to prevent the pump from overheating:

– Inspect the pump regularly for any potential leaks. Leaks can cause the fluid level to drop and also allow air to enter the system, which can cause problems.

If you’re noticing that the Hyundai hydraulic pump on your excavator is overheating, there are a few things you can do to prevent it. First, make sure that the pump is getting enough oil. If the pump isn’t properly lubricated, it will overheat. You should also check the cooling system to make sure it’s working properly. If the pump is still overheating, you may need to replace the seals or bearings.

If you have an excavator Hyundai, you may have experienced your hydraulic pump overheating. This can be a major problem, as it can lead to damaged equipment and even injuries. However, there are a few things you can do to help prevent this from happening. make sure that your excavator is properly ventilated. Second, check the fluid levels in your hydraulic system regularly. Third, use aHydraulic Pump Overheating Prevention Kit. By following these simple tips, you can help ensure that your hydraulic pump doesn’t overheat and cause damage to your equipment or yourself.

Whether it"s your construction vehicle or another piece of heavy machinery, the failure of a hydraulic pump can mean the failure of a project. However, before a hydraulic pump fails, it will often give a lot of warning signs first. Don"t ignore these signs of a failing hydraulic pump.

Hydraulic pumps make noise as they operate. You will grow accustomed to whatever noise you hear, which can help when the noises start to change. If you hear unusual noises, you may have a problem. At no time should your hydraulic system create banging or rattling noises.

A major cause of noise is aeration, which is what happens air becomes trapped within the system. Noises can also occur because the pump isn"t getting enough fluid. When there"s a lack of fluid, corrosion can take place which will contaminate the little fluid still in the system.

As that fluid circulates it can cause damage to every part of a hydraulic system. If you"re hearing odd noises from your hydraulic pump, then cease operating your heavy equipment or vehicle. You need to have the pump looked at to determine if you should repair or replace it.

Any leaking of hydraulic fluids should give you some concern. In larger hydraulic equipment, leaking is sometimes considered inevitable. However, when heavy equipment and vehicles show signs of leaking, you should immediately do what you can to mitigate the issue.

A leak that occurs inside or around the pump should prompt you to seek a repair. Equally, if you see signs of leaking outside the vehicle, then you can assume an interior leak has taken a turn for the worse. With a leak, the hydraulic system cannot maintain pressure, which can lead to issues with performance or outright system failure.

Sometimes, the leak doesn"t begin with the pump itself, but rather with a loose seal or a break in a line. Even when this is the case, the leak can lead to poor pump performance. Starting the investigation from the pump can often help to spot an issue with some other hydraulic component.

If your hydraulic system overheats, there"s a good chance a buildup of dirt and debris is causing the issue. Your hydraulic pump will have a hard time dissipating heat if the filters become clogged. The inability to release heat will cause temperatures to rise even higher.

As the heat increases, so does the temperature of the fluid. Hot fluid can weaken seals and degrade a lot faster than it should. Both those outcomes can mean further trouble for your hydraulic pump.

A bad hydraulic pump will lead to poor or sluggish performance. All the aforementioned issues can lead to a hydraulic pump that isn"t performing as it should. Nevertheless, even if you don"t experience any other issues, the drop in performance is a key sign you need to have your hydraulic pump repaired or replaced.

If your equipment depends on a functioning hydraulic system, you must stay diligent about keeping that system healthy. Monitor your hydraulic system and pay attention to any signs that something isn"t working as it should. Routine maintenance of your hydraulic system will help to keep its performance intact while also helping you find potential issues before they become problems.

Often, protecting the viability of your hydraulic pump only requires that you keep up with changing the fluid and replacing smaller components when necessary. You can often save a hydraulic pump with an issue by having it repaired or rebuilt by a professional service.

AtCarolina Hose & Hydraulics, we specialize in high-quality hydraulic components for heavy equipment and vehicles. Contact us for any of your hydraulic pump concerns immediately.

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.

We recently received a question about what causes a hydraulic system to overheat. There are several reasons for why a system may be overheating, so in this tip of the week, we take a closer look at some of the more common causes and how to troubleshoot them.

Plugged oil cooler: Check the oil temperature going in and out of the air cooler. There should be a significant delta temperature (6 degrees Celsius or so). If not, verify there is oil flow through the cooler. If there is no oil flow through the cooler, disconnect the in and out piping and blow out the piping. Check the air temperature before and after the cooler. Again, there should be a delta temperature. If not, take compressed air and blow out the dust from the fins. You can also take a fin comb (or a regular hair comb) and straighten out the fins. Lastly, check the fan. If the fan is clutch driven, there may be a problem with the clutch. Possibly replace the fan with one designed to move more air.

Pressure relief valve (PRV): Check the system PRV. If the PRV has failed or is failing, it may be letting oil dump back to the reservoir without going through the cooler. This will cause the oil to heat up.

Pressure compensated variable volume pump: If you have a pressure compensated variable volume pump, someone may have increased system pressure. If the pump compensator has been adjusted past the main PRV setting, this will cause the pump to dump wasted flow at the max pressure setting, inducing heat into the system.

Oil reservoir size: The oil reservoir should be sized to 3-5 times the gallons per minute (gpm) of the pump. If needed, increase reservoir size to lengthen oil residence time and promote heat release.

Pressure drop: Pressure drop is another heat generator. If not sized correctly, it often takes too much pressure to push the oil through all the valves, pipes, hoses, elbows, bends, and filters. This wasted energy shows up as heat and may be avoided by reviewing component size and reducing the number of bends in the piping. Flow capacity can be increased dramatically by increasing one hose size, resulting in less heat.

Cooling loop:Sometimes, you can fix the issue by adding an extra cooling loop to the hydraulic reservoir. Make sure to size the cooler correctly to achieve maximum heat removal.

Hope this tip of the week was helpful, and if you experience overheating issues with your hydraulic system, you can reach out to your local ExxonMobil distributor or representative to help further troubleshoot the issue.

Remember that hydraulic system running at 145 F last fall? The one you didn’t worry about with cooler weather on the way? In the middle of summer, it could be operating even hotter—if it hasn’t already shut down. That’s because any industrial hydraulic system that runs higher than 140 F is too hot. The resulting problems are costly:

Fluid power specialist Al Smiley of GPM Hydraulic Consulting, Monroe, GA, has dealt with countless hydraulic systems in industrial operations throughout the past 20 years. We asked him for ways to troubleshoot hot-running systems.

“First things first,” said Smiley, “it’s important to keep in mind that all hydraulic systems generate a certain amount of heat.” Approximately 25% of the input electrical horsepower will be used to overcome heat losses in a system. Whenever oil is ported back to the reservoir, and no useful work is done, heat will be generated.

The tolerances inside pumps and valves normally permit a small amount of oil to continuously bypass a system’s internal components, causing the fluid temperature to rise. When oil flows through the lines, several resistance points are encountered. For example, flow-control, proportional, and servo valves control the flow by restricting it. When oil flows through those valves, a pressure drop occurs. This means a higher pressure will exist at the inlet port than at the outlet port. Any time oil flows from a higher to a lower pressure, heat is generated and absorbed in the oil.

When a hydraulic system is designed, the reservoir and heat exchangers are sized to remove that heat—some of which is allowed to dissipate through the reservoir walls to the atmosphere. “Heat exchangers, if properly sized,” Smiley noted, “should remove the balance of the heat and allow the system to operate at approximately 120 F.”

Fig. 1. Pressure-compensating piston pumps are the most common type used in industrial hydraulic systems. The tolerances between the pistons and barrel are approximately 0.0004 in.

The pressure-compensating piston pump (Fig. 1) is the most commonly used type in industrial hydraulic systems. Tolerances between the pistons and barrel are approximately 0.0004 in. A small amount of oil at the pump outlet port will bypass through these tolerances, flow into the pump case, and then be ported back to the reservoir through the case-drain line. “This case-drain flow,” noted Smiley, “does no useful work and is, therefore, converted into heat.”

According to Smiley, the normal flow rate out of the case-drain line is 1% to 3% of the maximum pump volume. For example, a 30-gpm pump should have approximately 0.3 to 0.9 gpm of oil returning to the tank through the case drain. “A severe increase in this flow rate,” he explained, “will cause the oil temperature to rise considerably.”

To check the flow rate, the line can be ported into a container of known size and the flow timed “unless personnel have verified that the pressure in the hose is near zero psi,” Smiley warned, “they should not hold the line during this test.” The line should, instead, be secured to the container, he advised.

A flow meter can also be permanently installed in the case-drain line to monitor flow rates. Check it regularly to determine the amount of bypassing. The pump should be changed when the oil flow reaches 10% of the pump volume.

Fig. 2 (top). During normal operation of this typical variable-displacement, pressure-compensating pump, when system pressure is below the compensator setting (1,200 psi), the internal swash plate is held at maximum angle by the spring. This arrangement allows the pistons to fully stroke in and out, permitting the pump to deliver maximum volume. Flow from the outlet port of the pump is blocked through the compensator spool.

Fig. 3 (bottom). Once the pressure builds to 1,200 psi, the compensator spool shifts, directing oil to the internal cylinder. As the cylinder extends the angle of the swash plate, it moves to a near-vertical position. At this point, the pump will only deliver enough oil to maintain the 1,200-psi spring setting. The only heat generated by the pump at this time is from the oil flowing past the pistons and through the case-drain line.

Figure 2 is a diagram of a typical variable-displacement pressure-compensating pump. During normal operation, when the system pressure is below the compensator setting (1,200 psi), the internal swash plate is held at maximum angle by the spring. This allows the pistons to fully stroke in and out and let the pump deliver maximum volume. Flow from the pump’s outlet port is blocked through the compensator spool.

Figure 3 shows the condition of the same pump when pressure reaches 1,200 psi, and the compensator spool shifts, directing oil to the internal cylinder. As the cylinder extends the angle of the swash plate, it moves to a near-vertical position. At that point, the pump will only deliver enough oil to maintain the 1,200-psi spring setting. “The only heat generated by the pump at this time,” Smiley noted, “is from the oil flowing past the pistons and through the case-drain line.”

Fig. 4. Many pressure-compensating pumps incorporate a relief valve as a safety backup in case the compensator spool sticks in the closed position. The relief valve should be set 250 psi above the pressure-compensator setting. Since the relief-valve setting is above that of the compensator, no oil should flow through the relief-valve spool. Therefore, the valve tank line should be at ambient temperature.

Many pressure-compensating pumps incorporate a relief valve as a safety backup in case the compensator spool sticks in the closed position (Fig. 4). According to Smiley, the relief valve should be set 250 psi above the pressure-compensator setting. If the relief valve setting is above that of the compensator, no oil should flow through the relief-valve spool. Therefore, the tank lines of these valves should be at ambient temperature.

If, however, the compensator were to stick in the position shown in Fig. 2, the pump will deliver maximum volume at all times and oil not used by the system will return to the tank through the relief valve. “If this occurs, Smiley said, “significant heat will be generated.”

Smiley lamented that plant personnel often randomly adjust the pressures in these systems in an attempt to make the equipment run better. “If the local knob turner turns the compensator pressure above the setting of the relief valve,” he explained, “the excess oil will return to the tank through the relief valve, causing the oil temperature to rise 30 or 40 degrees. If the compensator fails to shift or is set above the relief-valve setting, a tremendous amount [of heat] will be generated.”

Assuming the maximum pump volume is 30 gpm and the relief valve is set to 1,450 psi, the amount of heat generation can be determined using the following formula.

If a 30-hp electric motor is used to drive this system, 25 hp will be converted to heat when in the idle mode. Since 746 W = 1 hp, then 18,650 W (746 x 25) or 18.65 kW of electrical energy will be wasted.

Smiley cited several other heat-generators in hydraulic systems and the importance of maintaining these components. These include accumulator dump valves and air-bleed valves that fail to open, thus allowing oil to bypass to the reservoir at high pressure. He also pointed to heat generated by oil bypassing cylinder piston seals.

If an air-type heat exchanger is used, clean the cooler fins—using a degreaser, if necessary—on a regularly scheduled basis. The temperature switch that controls the cooler fan should be set at 115 F.

If a water-cooled system is used, a modulating valve should be installed in the water line to regulate the flow through the cooler tubes to 25% of the oil flow.

Smiley noted that reservoirs should be cleaned at least annually, lest sludge and other contaminants coat their bottoms and sides. This would allow the reservoir to act as an incubator instead of dissipating heat to the atmosphere.

Smiley offered a final helpful hint for hot-hydraulics troubleshooters: “The next time a heat issue surfaces in one of your hydraulic systems, look for oil flowing from a higher to a lower pressure in the system. That is where you’ll find your problem.” MT

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.

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.

After leaks, overheating is the second most common problem that occurs with hydraulic equipment. Inefficiencies are what causes the heating of hydraulic fluid while in operation, which will result in losses of input power, which is then converted to heat.

If you’re experiencing overheating problems in your hydraulic systems, there are two solutions that can help you with this problem. You can choose to either decrease the heat load or increase the heat dissipation. Start by checking the reservoir fluid level and fill it to the correct level if you see that it’s low because

Next, inspect the heat exchanger to ensure that the core is not being blocked. This is very important because the heat exchanger’s ability to dissipate heat is dependent on both the flow rate and the temperature of the hydraulic fluid and the cooling air or the water that is circulating through the exchanger. If you see that there is an issue with the performance of the cooling circuit components, replace them right away.

You can use an infrared thermometer to check the performance of a heat exchanger so long as the design flow rate of the hydraulic fluid through the exchanger is known. Measure the temperature of the oil entering and exiting the exchanger and substitute the values using a specific formula that a professional hydraulic company can provide.

A pressure drop will cause heat to generate, meaning that any of the components in the system that have internal leakage will increase the heat load on the system, causing it to overheat. This could occur for a number of reasons, including a cylinder leaking high-pressure fluid past its piston seal to a relief valve that has been incorrectly adjusted. For this reason, you must replace any of the heat-generating components that don’t look right, and in many cases, an expert is needed to help identify the component that is causing the problem.

No matter what is causing the hydraulic system to overheat, you must shut it down right away to get to the root of the cause and fix it. Continuing to operate when the fluid is at an incorrect temperature is dangerous and the damage is inevitable. If you start to see that the system is overheating, you need to identify the cause so that you can resolve the issue.

Hydraulic pumps convert mechanical energy into fluid flow, which powers hydraulic systems. Hydraulic systems are critical for everything from vehicles to industrial machinery to heavy-duty construction equipment.

No matter what you’re using your hydraulic system for, it’s important to know the signs that your pump is struggling. A simple check of these signs might be all that’s needed to prevent an expensive or dangerous pump failure later on.

One of the most serious signs of future pump failure is overheating. If heat exchanges and vents are obstructed or overwhelmed with airborne debris, it can reduce the pump’s ability to adequately dissipate heat. At temperatures of 180° F or higher, hydraulic fluid begins to lose viscosity, reducing its lifespan. Overheated fluid lowers the pump’s operating efficiency and puts additional strain on seals, valves and other parts.

Hydraulic fluid is also susceptible to contamination from external debris, chemicals or particles that have separated from the internal components like metal shavings or chips.

These particles will also increase heat by thinning the hydraulic fluid, clogging valves and fluid pathways and degrading the pump’s components. Another cause of excess heat is over-pressurization, which overworks the hydraulic fluid and increases friction and wear on the system.

Hydraulic pumps should be expected to produce some noise as a result of normal operation. However, new or unfamiliar noises like banging or a high-pitch whine are cause for concern. The most common cause for unusual sounds is contamination of the hydraulic fluid through aeration or cavitation.

As the aerated hydraulic fluid is put under pressure in the pumping process, these air bubbles destabilize the regular cycling of fluid, creating loud bangs or a high-pitched whine.

Leaks are a clear sign of problems with a hydraulic pump. Pump leaks are divided into internal and external leaks. External leaks are easier to find and may take the form of pools or puddles of hydraulic fluid underneath the machine, or a spray of fluid from a pressurized line. External leaks are usually caused by component issues like a hole or tear in a hose or pipe, loose connections, or damaged valves.

Internal leaks are harder to diagnose and are usually identified through secondary problems like low pressure, increased fluid demand, or slow performance. Internal leaks are tracked by closely monitoring fluid levels in different areas of the system or testing the pump with a trained technician. Internal failures are usually caused by the degradation of valves and other parts over time.

Slow or unreliable performance is an obvious sign that something is wrong with a hydraulic pump. Slow operation is symptomatic of a variety of other problems like overheating, contaminated fluid, or issues with pressurization. Another possible cause is that the pump’s components have simply degraded through regular use and are due to be changed. Problems with heat, fluid or pressurization will all put more stress on aging internal components and decrease the pump’s efficiency further.

With a little practice it’s easy to identify the common signs a hydraulic pump is starting to fail. Over time, common hydraulic pump problems will compound on one another to worsen overall performance, which makes early identification and repair important. However, even the best-maintained hydraulic pumps begin to show signs of wear and damage eventually. Many experts recommend a service check after every 10,000 hours of operation.

Servo Kinetics in Ann Arbor provides reliability centered maintenance checks to best serve your hydraulic pump and motor function. Our team of professionals and engineers are here to help address your industrial hydraulic repair needs in a timely manner with high quality work and at a low cost.

Our services include a large span of hydraulic pumps and motors as well asreverse engineering services and new pumps and motors. Every unit you send goes through a rigorous quality process that is trusted and used throughout the industry. Call us and experience the difference with a rapid response, fast turnaround, and ongoing cost savings.

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.

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.

When a wide diameter tube narrows into a thin rubber hose, heat is generated, for the oil is “squeezing” itself into less space. Better system designs minimize this phenomenon, but the impact of this fluid compressibility problem is felt again if the gear is placed under stress. Mobile hydraulics overloading incidents often translate to fluid overheating problems. Next, loose mechanical parts vibrate. As the vibrations propagate, the noise generates heat. Dissipated across a large machine frame, the energy can find its way into the force storing fluid. Moving on, pressure drops across actuators and valves generate thermal losses. If the pressure differential doesn’t produce mechanical work, then it’ll turn into an unmanageable thermal loss. Cumulative heat losses, loose parts, design bottlenecks, and pressure losses, all of these thermal effectors constitute a system threat.

As the temperature rises, the oil and frame dissipate the heat. At least that’s the theory. If the losses are too high, hydraulic fluid overheating problems will worsen. The oil might separate, the equipment seals degenerate, and the gear prematurely fail. Lift and transport responsiveness experience a performance drop because of a change in the oil’s viscosity. Maintenance techs can reverse these effects. Since the fluid reservoir collects the heat, they’ll make sure that the tank is full. With heat exchanger parts, they’ll check flow-rates and temperatures. Remember, the oil temperature has to stay below 80°C if the seal and hose components are to remain functional.

On a recent project, there was a 25 horsepower motor running a torque limited piston pump. When we were doing performance testing, everything worked out fine. As soon as I left, the customer was complaining about excessive heat generation leading to downtime waiting for the oil to cool.

The problem wasn’t clear until I talked with the pump manufacturer. In order to keep a pressure compensated pump cool, the oil needs to be circulated internally. Depending on the manufacturer, 1/4 of the flow may be dumped back to tank to keep the pump cool.

Pressure compensated hydraulic systems tend to overheat because oil is continually circulated to keep the pump cool. The higher the standby pressure, the more heat created. Adding heat exchangers, shutting the pump down and lowering or having adjustable stand by pressure can reduce the heat generated.

So you have spent the extra money to get a piston pump, but do you know that there is a hidden danger in built in to these pumps? Let’s explore the danger

It turns out that pressure compensated systems are always moving oil, even when in standby. I found out that roughly 3 to 4 gpm were being dumped back to tank through the pump’s case drain at the compensator pressure. This was nearly 7 horsepower that was wasted.

This situation was not detected in testing, because we ran back to back tests with no idle time in between. Once the idle time was added in, we discovered that the oil temperature rose around 1-2 degrees per minute. An impressive feat on 100 gallons of hydraulic oil.

Adding a heat exchanger is a very obvious solution. These are usually forced air radiators made for hydraulics that are installed on the return line or the case drain line.

In an industrial application, an 8 hp heat exchanger is going to run around $1000 (in 2019). That doesn’t include the cost of the hoses or an electrican to wire the fans. Mobile (12 VDC) applications are less expensive and easier to wire yourself.

But as an engineer you should be asking yourself, “Why am I generating all this power just to heat the shop? That extra heat is going to make working in the summer excruciating.” All that an it is wasteful as well.

If we assume that we have 7 hp of wasted power from our pump during idle time, that is 5.2 kWh of energy. At 12 cents per kWh, that is $0.63 / hr of idle time.

If the only reason you are adding a heat exchanger is to reject idle time heat generation, there are many other options which we will explore below. Don’t let the simplicity of the a heat exchanger solution be where you stop. Keep reading.

As an engineer, the first step should always be fully diagnosing the root cause and not just masking the symptom. If you notice excessive idle time, make inquiries as to why the machine idles so much. Is an operator waiting on another process? Is it breaktime? They are many reasons for high idle time.

This one is pretty self explanatory. If the system doesn’t need to be on, shut it down. If the system isn’t running, it can’t create heat. In fact, it has the opportunity to reject heat out of the system. Win-win!

One thing that we want to watch out for is turning the motor on and off too much. Motor startup is a significant source of wear on the motor so we want to minimize the number of startups.

Luckily, pressure compensated systems will start in a loaded condition. There should be no (or little) pressure on the outlet and compensator. This means that when starting the motor, it won’t be anywhere near fully loaded. Since there is no pressure, it will take 1-3 seconds for the pump to produce enough pressure to load up the compensator. This will usually be long enough to minimize startup loads on the motor.

If the machine is PLC controlled, adding a timer is easy to do when the machine is idle. This will be a good back up to the case where an operator accidentally leaves the system on when it is break time.

In the machine discussed above, we added a 2 minute timer for periods when there were no outputs given to any function. This was a great protection from heat generation, plus it was a signal to the operator that he or she was taking too long. Yes, it also had the side effect of increased production.

If excessive motor startup is a real concern, you may want to add a restart delay. This is common in HVAC systems where it is common to see a 5 minute ‘compressor delay’. This delay probably adds many hours of life to your HVAC system.

In some hydraulic systems, you just don’t need the system pressure you designed for. As a good designer, you have calculated your pressures and flows for less than what is available. As a result, you can reduce the standby pressure, but only minimally.

I say minimally, because there isn’t a drastic reduction in power with this one. However, you know your machine better than I do, so maybe there is more energy savings here.

This option is the most expensive and most efficient. By using an electro-proportional relief valve (DO3 P to T relief valve for industrial applications), you can set the compensator pressure for exactly what you need for the current function. As the functions change, the compensator pressure changes.

This is the most expensive option because your PLC system is going to have to output an analog signal (usually 0 – 10VDC) to control the electro-proportional relief valve (also expensive). As a good designer, you will also want a pressure sensor to provide feedback on the system.

However, this system is fully customizable and can act similiar to a load sensing mobile system. Through careful programming, you can tailor your pressure setting to what that function needs at any particular time.

This is a much simpler version of the adjustable compensator option above. In this scenario, we would have one or more compensator relief valves switched on or off by non-proportional solenoid valves.

In this system, there would be one relief valve (main relief below) tied directly to the compensator and other relief valves are separated from the pressure line by 2 position, 2 way, normally closed solenoid operated valve. The main valve must be set at the maximum desired pressure so that if all else fails, the system will have a direct path of pressure control. The other valves can be activated, one at a time, to control the pressure for certain pressures.

This system cost is also reduced from the adjustable relief valve option because it eliminates the needed analog control system and extra programming for the PLC.

Additionally, the system can be made to look quite neat as well. Having a multisection DO3 manifold with the pressure port connected to the compensator will provide the foundation. Often, you can get the main relief valve already incorporated into the manifold which is a big bonus. You can then add solenoid valves on as the first row. On top of those valves you can add the individual relief valves.

If none of the sections are energized, the pump will create the maximum pressure which is set in the manifold relief valve. If one or more sections are activated, the pump will create pressure to the lowest set active pressure. In the schematic above, you can adjust the compensator pressure to 600 psi, 1200 psi, 2200 psi or 2750 psi depending on which sections are activated.

This can be a subset of several other options. If your system idles for long periods of time, you can just have a 2 position, 2 way, normally closed solenoid valve dump the pressure to tank. This will destroke the pump and not create any heat.

Another option on this is to couple it with a timer so that if there is no demand for the system hydraulics, the solenoid will activate and the pressure will be reduced. When demand for higher pressures is needed, the PLC will deactivate this solenoid.

I actually chose two of these solutions. First, I put a two minute timer on when the system is in normal standby. There is also a 25 minute timer when the system is in the cutting mode. At the 25 minute cycle, only 500 psi is needed to operate a hydraulic motor and control the travel of a saw.

In cutting mode, I also reduced the standby pressure from 2750 psi to 500 psi reducing the needed power by 82%. Sweet! I accomplished this by adding a second compensator relief valve that is activated by a 2 position 3 way valve.

Pressure compensated systems are generally more efficient and with a torque limiter they will give you the best performance of any other hydraulic system. Unfortunately, they do have the drawback of heat generation when in standby mode. If the solutions above are applied, you can often eliminate the need for a heat exchanger.

Replacing a failing hydraulic pump can be challenging. If the wrong alteration is made, you risk damaging your entire hydraulics system. Furthermore, there are many reasons why your pump may be failing, but not all of them may require a full replacement.

If your hydraulic pump isn’t working like it used to, you need to start troubleshooting as quickly as p