running hydraulic pump dry factory

If the impeller seizes, it will stop and not rotate. To correct this, the pump should be taken apart and a drill bit should be used to clean out the bore of the impeller.

A hole may develop in the rear housing, allowing liquid to escape. Or, the boss of the rear housing, which secures the pump shaft, may become deformed, which will allow the shaft to move instead of remaining stationary.

This will cause damage to the impeller and may cause the shaft to break from the impeller bouncing on it. If the pump is made from stainless steel, it is unlikely holes will develop in the rear housing or that the boss will deform. What is likely to happen is the impeller bushing will seize onto the shaft.

Generally, the larger the pump with larger and heavier impellers, the faster it will be to suffer damage. You can search our pumps for the sizes we have available.

Another factor is the liquid previously in the pump. If the liquid is ambient or cooler, it will take more time for the pump to suffer damage after it starts to run dry than if the liquid is warmer.

If you are using the pump for tank transfer and want to empty the tank, this may mean running the pump dry for a few seconds. If the pump is run dry for less than 45-60 seconds, the pump should not suffer damage. Anytime you are aware that the pump may have to be run dry to empty the tank, the operator must take care to ensure the pump is run dry for the absolute minimum amount of time. Any pump that suffers from running dry is not covered by warranty.

Dry running can be an expensive hazard on your equipment but with care and supervision, you can elongate the life of your machinery. Learn more about our maintenance best practices by contacting us.

Dry Running is an undesirable condition which affects most pump designs and is characterised when a pump operates without an adequate amount of fluid. In most pump technologies, this leads to cavitation and critical damage to the internal pumping elements such as impellers, lobes, gears, casings, seals & bearings.

Dry running is usually related to how the pump is operated, monitored & controlled which is typically a result of human error. Companies generally rely on their operators to monitor the pumps on the line, however, problems will arise when a pump is unintentionally left running for prolonged periods of time after the intended operation has been completed. For example, during offloading of a tanker, an operator may leave the pump unattended whilst the tanker is being evacuated and the pump may over-run when the tanker is empty thus resulting in damage to the pump internals.

Dry running could lead mechanical seals to wearing quickly which could cause the pump to leak. This will allow the potentially hazardous liquid to spill putting pump operators at risk.

Dry running can damage your pump which could cause an immediate stop to your production line meaning a loss of production – delays & costs to your business

Risked cavitation if dry run for long periods of time which may require the whole pump to be replaced if there has been serious damage to the impellers in your pump

Dry Running can be extremely costly to your business so please check with your supplier or the pump manufacturer whether the pump you’ve purchased can be dry run before operating it.

When using most pump designs, such as Rotodynamic as well as Reciprocating and Rotary Positive Displacement Pumps, most companies need to install protection and control devises on the pumps and system to ensure that the pump is stopped immediately after the pumping operation is complete, or in the absence of fluid at the pump suction or source.

Pressure or Level Switch Protection:Pressure Switches fitted to the suction pipe or port of the pump(s) or Float Switches/Electrode Relays in the Supply tank

Engineers on-site and Operators spend significant amounts of time ensuring pumps are properly installed & primed, significantly increasing the cost and complexity of the installation. However, despite all these efforts, the ever-present possibility of human error, malfunctioning control and monitoring equipment, unpredictable events & improper use of equipment means that Dry Running is never completely eradicated. As a result, plant owners are constantly in search of technology and solutions which can prevent or avoid the costly and damaging effects of Dry Running in order to reduce maintenance costs, increase throughput and alleviate pressures put onto operators to constantly monitor, control and protect their equipment on the line.

There are a variety of standard accessories that can be used to control pumping equipment to protect is from dry running such as pressure and temperature sensors. Additional accessories and expensive sealing systems aren’t always the answer. Not all pumps are created equally, in fact, at Tapflo UK we have a variety of pump solutions that will allow you to dry run your pump without causing damage to it. Need your pump to run dry? Let us know when you call us.

Tapflo offer a range of pump technologies that have the added benefit of being able to dry run, including our Diaphragm Pumps and Peristaltic Pumps which can run dry indefinitely without damaging the pump.

Due to their design and construction, both of these pumping technologies are able to operate under dry conditions without experiencing common wear problems associated with dry running. Not only does this alleviate the pressure put on the operator, but it also simplifies the pumping system and reduces the cost of installation and ownership significantly. Of course, these designs, on their own, do not overcome the energy costs affiliated with overrunning equipment, to improve this, Tapflo offers dry run protection devices such as our Pneumatic Guardian System for Diaphragm Pumps which automatically stops your pump when the pumping process is complete.

In summary, Tapflo UK have a full range of pumping solutions which can either protect equipment from Dry Running or indeed avoid problems associated with Dry Running completely! Let’s discuss your options today.

Facility operators in the oil and gas industry have raised concerns on how to solve their top failure modes: extremely short or non-existent dry run pump time limits and unacceptable levels of cavitation when pumping extremely light liquids with high vapor pressures.

Pump cavitation and dry run related failures cost companies millions of dollars annually, including replacement costs for damaged equipment and lost sales due to poor performance. With an improving economy and anticipated fuel production increase, sales of fluid-handling pumps are forecast to rise 5.5% annually to $84 billion in 2018. Given this proliferation, the historical pattern suggests that costs associated with repairs or replacements also will increase dramatically.

Learn how Parker"s innovation in pump technology can reduce your operational downtime, decrease operating costs, and improve performance. Download our white paper now.

Dry running occurs when a pump operates without sufficient lubricating liquid around the pumping element. This can be caused by either widespread vapor formation, also known as cavitation, inside the pump or absence of pumping fluid altogether. These adverse conditions can lead to dangerously unstable pressure, flow, or overheating which may cause the pumping element to seize or break.

When cavitation occurs, vapor bubbles form and expand in the pumping liquid on the suction side of the pump before reaching the higher-pressure discharge side of the pump and violently collapsing near the surface of the pumping element. This triggers shock waves inside the pump which cause significant damage to the pumping element. If left untreated, cavitation will destroy the pumping element and other components over time, drastically shortening the pump’s life.

Cavitation itself may also be so widespread that it creates a dry run situation inside the pump due to excessive vapor formation. Pumps most often rely on the pumping fluid itself to lubricate the bearing surfaces of the pumping element – if a pump is operated without this fluid, the low to non-existent lubrication at these bearing surfaces will cause excess heat generation, increased wear, and potentially even failure of the pump if the pumping element seizes or breaks. The life of a pump subjected to dry run will be significantly reduced or, in the worst case, brought to an untimely end.

“What separates our solution from our competitors is, our technology is automated and integrated into the pump design. You don’t need to worry about pumps stopping and starting every 20 – 30 seconds, they will dry run continuously.”

Learn how this innovation in pump technology can reduce your operational downtime, decrease operating costs, and improve performance. Download our white paper now.

Dry running is usually undesirable in a centrifugal pump it occurs in the total absence of the liquid component of the fluid handled (e. g. following the ingress of air in the suction line) or if under normal operating conditions gas bubbles (see

During normal operation of a well-designed centrifugal pump, the fluid handled completely fills the flow space inside the pump, including narrow controlled gap seals on impellers,mechanical seals. The liquid helps to cool and lubricate the components in contact with each other and exercises a centring action in the clearance gaps of the impellers and shaft passages (see Multistage pump) so that long and slender ring-section pumps for example are able to run without the rotor touching the casing.

In the absence of liquid, dry running can occur in certain areas because of insufficient cooling and centring action. The consequences are overheating, abrasion, seizure of the materials, vibrations and other phenomena which may in due course lead to the complete disintegration of the pump.

If the pump operator cannot avoid such instances of absolute or partial dry running, it may be necessary to invest in the optimisation of the centrifugal pump"s design. An improved pump design should include reinforced shafts which prevent radial contact between the rotor and the casing, specially designed clearance gaps (controlled gap seal) and mechanical seals, gland packings and bearings which are supplied with external lubricating or barrier fluids rather than using the fluid handled.

Pumps fitted with a hydraulic axial thrust balancing device must be equipped with an additional thrust bearing to prevent rubbing contact or seizure. In the event of incipient dry running, the pump can also be stopped by a dry running protection device.

Self-priming centrifugal pumps must always be filled to a certain liquid fill level prior to start-up in order to be able to self-prime. During the self-priming phase they operate under partial dry running conditions.

One of the main reasons of pump damage is the dry running due to functioning without liquid, so it is important to pay attention and never let a pump operate without liquid inside. Moreover, if you think about it, the main purpose of hydraulic pumps is to transfer a fluid, so letting the pump work without liquid is useless and it’s a huge waste of energy.

To avoid the inconvenience of the dry running you can simply install a dry running protection device which stops the pump immediately in case of danger of dry-running. As a matter of fact, the device checks constantly the active power of the motor, which is the minimum value of the instantaneous power absorbed by the pump, through the reception of information about the voltage, the cosφ and current variations. Through a set point and a timer, which are adjustable, it’s possible to set the minimum power and the triggering time of the device. If the power goes under the established value, the pump stops and the device must be switched on again manually. In case of continuous intervention on the apparatus,  check the presence of liquid and/or the correct functioning of the plant to find the cause of working of the device.

A gear pump is a type of positive displacement (PD) pump. It moves a fluid by repeatedly enclosing a fixed volume using interlocking cogs or gears, transferring it mechanically using a cyclic pumping action. It delivers a smooth pulse-free flow proportional to the rotational speed of its gears.

Gear pumps use the actions of rotating cogs or gears to transfer fluids. The rotating element develops a liquid seal with the pump casing and creates suction at the pump inlet. Fluid, drawn into the pump, is enclosed within the cavities of its rotating gears and transferred to the discharge. There are two basic designs of gear pump: external and internal(Figure 1).

An external gear pump consists of two identical, interlocking gears supported by separate shafts. Generally, one gear is driven by a motor and this drives the other gear (the idler). In some cases, both shafts may be driven by motors. The shafts are supported by bearings on each side of the casing.

As the gears come out of mesh on the inlet side of the pump, they create an expanded volume. Liquid flows into the cavities and is trapped by the gear teeth as the gears continue to rotate against the pump casing.

No fluid is transferred back through the centre, between the gears, because they are interlocked. Close tolerances between the gears and the casing allow the pump to develop suction at the inlet and prevent fluid from leaking back from the discharge side (although leakage is more likely with low viscosity liquids).

An internal gear pump operates on the same principle but the two interlocking gears are of different sizes with one rotating inside the other. The larger gear (the rotor) is an internal gear i.e. it has the teeth projecting on the inside. Within this is a smaller external gear (the idler –only the rotor is driven) mounted off-centre. This is designed to interlock with the rotor such that the gear teeth engage at one point. A pinion and bushing attached to the pump casing holds the idler in position. A fixed crescent-shaped partition or spacer fills the void created by the off-centre mounting position of the idler and acts as a seal between the inlet and outlet ports.

As the gears come out of mesh on the inlet side of the pump, they create an expanded volume. Liquid flows into the cavities and is trapped by the gear teeth as the gears continue to rotate against the pump casing and partition.

Gear pumps are compact and simple with a limited number of moving parts. They are unable to match the pressure generated by reciprocating pumps or the flow rates of centrifugal pumps but offer higher pressures and throughputs than vane or lobe pumps. Gear pumps are particularly suited for pumping oils and other high viscosity fluids.

Of the two designs, external gear pumps are capable of sustaining higher pressures (up to 3000 psi) and flow rates because of the more rigid shaft support and closer tolerances. Internal gear pumps have better suction capabilities and are suited to high viscosity fluids, although they have a useful operating range from 1cP to over 1,000,000cP. Since output is directly proportional to rotational speed, gear pumps are commonly used for metering and blending operations. Gear pumps can be engineered to handle aggressive liquids. While they are commonly made from cast iron or stainless steel, new alloys and composites allow the pumps to handle corrosive liquids such as sulphuric acid, sodium hypochlorite, ferric chloride and sodium hydroxide.

External gear pumps can also be used in hydraulic power applications, typically in vehicles, lifting machinery and mobile plant equipment. Driving a gear pump in reverse, using oil pumped from elsewhere in a system (normally by a tandem pump in the engine), creates a hydraulic motor. This is particularly useful to provide power in areas where electrical equipment is bulky, costly or inconvenient. Tractors, for example, rely on engine-driven external gear pumps to power their services.

Gear pumps are self-priming and can dry-lift although their priming characteristics improve if the gears are wetted. The gears need to be lubricated by the pumped fluid and should not be run dry for prolonged periods. Some gear pump designs can be run in either direction so the same pump can be used to load and unload a vessel, for example.

The close tolerances between the gears and casing mean that these types of pump are susceptible to wear particularly when used with abrasive fluids or feeds containing entrained solids. However, some designs of gear pumps, particularly internal variants, allow the handling of solids. External gear pumps have four bearings in the pumped medium, and tight tolerances, so are less suited to handling abrasive fluids. Internal gear pumps are more robust having only one bearing (sometimes two) running in the fluid. A gear pump should always have a strainer installed on the suction side to protect it from large, potentially damaging, solids.

Generally, if the pump is expected to handle abrasive solids it is advisable to select a pump with a higher capacity so it can be operated at lower speeds to reduce wear. However, it should be borne in mind that the volumetric efficiency of a gear pump is reduced at lower speeds and flow rates. A gear pump should not be operated too far from its recommended speed.

For high temperature applications, it is important to ensure that the operating temperature range is compatible with the pump specification. Thermal expansion of the casing and gears reduces clearances within a pump and this can also lead to increased wear, and in extreme cases, pump failure.

Despite the best precautions, gear pumps generally succumb to wear of the gears, casing and bearings over time. As clearances increase, there is a gradual reduction in efficiency and increase in flow slip: leakage of the pumped fluid from the discharge back to the suction side. Flow slip is proportional to the cube of the clearance between the cog teeth and casing so, in practice, wear has a small effect until a critical point is reached, from which performance degrades rapidly.

Gear pumps continue to pump against a back pressure and, if subjected to a downstream blockage will continue to pressurise the system until the pump, pipework or other equipment fails. Although most gear pumps are equipped with relief valves for this reason, it is always advisable to fit relief valves elsewhere in the system to protect downstream equipment.

Internal gear pumps, operating at low speed, are generally preferred for shear-sensitive liquids such as foodstuffs, paint and soaps. The higher speeds and lower clearances of external gear designs make them unsuitable for these applications. Internal gear pumps are also preferred when hygiene is important because of their mechanical simplicity and the fact that they are easy to strip down, clean and reassemble.

Gear pumps are commonly used for pumping high viscosity fluids such as oil, paints, resins or foodstuffs. They are preferred in any application where accurate dosing or high pressure output is required. The output of a gear pump is not greatly affected by pressure so they also tend to be preferred in any situation where the supply is irregular.

A gear pump moves a fluid by repeatedly enclosing a fixed volume within interlocking cogs or gears, transferring it mechanically to deliver a smooth pulse-free flow proportional to the rotational speed of its gears. There are two basic types: external and internal. An external gear pump consists of two identical, interlocking gears supported by separate shafts. An internal gear pump has two interlocking gears of different sizes with one rotating inside the other.

Gear pumps are commonly used for pumping high viscosity fluids such as oil, paints, resins or foodstuffs. They are also preferred in applications where accurate dosing or high pressure output is required. External gear pumps are capable of sustaining higher pressures (up to 7500 psi) whereas internal gear pumps have better suction capabilities and are more suited to high viscosity and shear-sensitive fluids.

A gear pump is a type of positive displacement (PD) pump. Gear pumps use the actions of rotating cogs or gears to transfer fluids. The rotating gears develop a liquid seal with the pump casing and create a vacuum at the pump inlet. Fluid, drawn into the pump, is enclosed within the cavities of the rotating gears and transferred to the discharge. A gear pump delivers a smooth pulse-free flow proportional to the rotational speed of its gears.

There are two basic designs of gear pump: internal and external (Figure 1). An internal gear pump has two interlocking gears of different sizes with one rotating inside the other. An external gear pump consists of two identical, interlocking gears supported by separate shafts. Generally, one gear is driven by a motor and this drives the other gear (the idler). In some cases, both shafts may be driven by motors. The shafts are supported by bearings on each side of the casing.

As the gears come out of mesh on the inlet side of the pump, they create an expanded volume. Liquid flows into the cavities and is trapped by the gear teeth as the gears continue to rotate against the pump casing.

No fluid is transferred back through the centre, between the gears, because they are interlocked. Close tolerances between the gears and the casing allow the pump to develop suction at the inlet and prevent fluid from leaking back from the discharge side (although leakage is more likely with low viscosity liquids).

External gear pump designs can utilise spur, helical or herringbone gears (Figure 3). A helical gear design can reduce pump noise and vibration because the teeth engage and disengage gradually throughout the rotation. However, it is important to balance axial forces resulting from the helical gear teeth and this can be achieved by mounting two sets of ‘mirrored’ helical gears together or by using a v-shaped, herringbone pattern. With this design, the axial forces produced by each half of the gear cancel out. Spur gears have the advantage that they can be run at very high speed and are easier to manufacture.

Gear pumps are compact and simple with a limited number of moving parts. They are unable to match the pressure generated by reciprocating pumps or the flow rates of centrifugal pumps but offer higher pressures and throughputs than vane or lobe pumps. External gear pumps are particularly suited for pumping water, polymers, fuels and chemical additives. Small external gear pumps usually operate at up to 3500 rpm and larger models, with helical or herringbone gears, can operate at speeds up to 700 rpm. External gear pumps have close tolerances and shaft support on both sides of the gears. This allows them to run at up to 7250 psi (500 bar), making them well suited for use in hydraulic power applications.

Since output is directly proportional to speed and is a smooth pulse-free flow, external gear pumps are commonly used for metering and blending operations as the metering is continuous and the output is easy to monitor. The low internal volume provides for a reliable measure of liquid passing through a pump and hence accurate flow control. They are also used extensively in engines and gearboxes to circulate lubrication oil. External gear pumps can also be used in hydraulic power applications, typically in vehicles, lifting machinery and mobile plant equipment. Driving a gear pump in reverse, using oil pumped from elsewhere in a system (normally by a tandem pump in the engine), creates a motor. This is particularly useful to provide power in areas where electrical equipment is bulky, costly or inconvenient. Tractors, for example, rely on engine-driven external gear pumps to power their services.

External gear pumps can be engineered to handle aggressive liquids. While they are commonly made from cast iron or stainless steel, new alloys and composites allow the pumps to handle corrosive liquids such as sulphuric acid, sodium hypochlorite, ferric chloride and sodium hydroxide.

External gear pumps are self-priming and can dry-lift although their priming characteristics improve if the gears are wetted. The gears need to be lubricated by the pumped fluid and should not be run dry for prolonged periods. Some gear pump designs can be run in either direction so the same pump can be used to load and unload a vessel, for example.

The close tolerances between the gears and casing mean that these types of pump are susceptible to wear particularly when used with abrasive fluids or feeds containing entrained solids. External gear pumps have four bearings in the pumped medium, and tight tolerances, so are less suited to handling abrasive fluids. For these applications, internal gear pumps are more robust having only one bearing (sometimes two) running in the fluid. A gear pump should always have a strainer installed on the suction side to protect it from large, potentially damaging, solids.

Generally, if the pump is expected to handle abrasive solids it is advisable to select a pump with a higher capacity so it can be operated at lower speeds to reduce wear. However, it should be borne in mind that the volumetric efficiency of a gear pump is reduced at lower speeds and flow rates. A gear pump should not be operated too far from its recommended speed.

For high temperature applications, it is important to ensure that the operating temperature range is compatible with the pump specification. Thermal expansion of the casing and gears reduces clearances within a pump and this can also lead to increased wear, and in extreme cases, pump failure.

Despite the best precautions, gear pumps generally succumb to wear of the gears, casing and bearings over time. As clearances increase, there is a gradual reduction in efficiency and increase in flow slip: leakage of the pumped fluid from the discharge back to the suction side. Flow slip is proportional to the cube of the clearances between the cog teeth and casing so, in practice, wear has a small effect until a critical point is reached, from which performance degrades rapidly.

Gear pumps continue to pump against a back pressure and, if subjected to a downstream blockage will continue to pressurise the system until the pump, pipework or other equipment fails. Although most gear pumps are equipped with relief valves for this reason, it is always advisable to fit relief valves elsewhere in the system to protect downstream equipment.

The high speeds and tight clearances of external gear pumps make them unsuitable for shear-sensitive liquids such as foodstuffs, paint and soaps. Internal gear pumps, operating at lower speed, are generally preferred for these applications.

External gear pumps are commonly used for pumping water, light oils, chemical additives, resins or solvents. They are preferred in any application where accurate dosing is required such as fuels, polymers or chemical additives. The output of a gear pump is not greatly affected by pressure so they also tend to be preferred in any situation where the supply is irregular.

An external gear pump moves a fluid by repeatedly enclosing a fixed volume within interlocking gears, transferring it mechanically to deliver a smooth pulse-free flow proportional to the rotational speed of its gears.

External gear pumps are commonly used for pumping water, light oils, chemical additives, resins or solvents. They are preferred in applications where accurate dosing or high pressure output is required. External gear pumps are capable of sustaining high pressures. The tight tolerances, multiple bearings and high speed operation make them less suited to high viscosity fluids or any abrasive medium or feed with entrained solids.

Check that the electric motor is running. Although this is a simple concept, before you begin replacing parts, it’s critical that you make sure the electric motor is running. This can often be one of the easiest aspects to overlook, but it is necessary to confirm before moving forward.

Check that the pump shaft is rotating. Even though coupling guards and C-face mounts can make this difficult to confirm, it is important to establish if your pump shaft is rotating. If it isn’t, this could be an indication of a more severe issue, and this should be investigated immediately.

Check the oil level. This one tends to be the more obvious check, as it is often one of the only factors inspected before the pump is changed. The oil level should be three inches above the pump suction. Otherwise, a vortex can form in the reservoir, allowing air into the pump.

What does the pump sound like when it is operating normally? Vane pumps generally are quieter than piston and gear pumps. If the pump has a high-pitched whining sound, it most likely is cavitating. If it has a knocking sound, like marbles rattling around, then aeration is the likely cause.

Cavitation is the formation and collapse of air cavities in the liquid. When the pump cannot get the total volume of oil it needs, cavitation occurs. Hydraulic oil contains approximately nine percent dissolved air. When the pump does not receive adequate oil volume at its suction port, high vacuum pressure occurs.

This dissolved air is pulled out of the oil on the suction side and then collapses or implodes on the pressure side. The implosions produce a very steady, high-pitched sound. As the air bubbles collapse, the inside of the pump is damaged.

While cavitation is a devastating development, with proper preventative maintenance practices and a quality monitoring system, early detection and deterrence remain attainable goals. UE System’s UltraTrak 850S CD pump cavitation sensor is a Smart Analog Sensor designed and optimized to detect cavitation on pumps earlier by measuring the ultrasound produced as cavitation starts to develop early-onset bubbles in the pump. By continuously monitoring the impact caused by cavitation, the system provides a simple, single value to trend and alert when cavitation is occurring.

The oil viscosity is too high. Low oil temperature increases the oil viscosity, making it harder for the oil to reach the pump. Most hydraulic systems should not be started with the oil any colder than 40°F and should not be put under load until the oil is at least 70°F.

Many reservoirs do not have heaters, particularly in the South. Even when heaters are available, they are often disconnected. While the damage may not be immediate, if a pump is continually started up when the oil is too cold, the pump will fail prematurely.

The suction filter or strainer is contaminated. A strainer is typically 74 or 149 microns in size and is used to keep “large” particles out of the pump. The strainer may be located inside or outside the reservoir. Strainers located inside the reservoir are out of sight and out of mind. Many times, maintenance personnel are not even aware that there is a strainer in the reservoir.

The suction strainer should be removed from the line or reservoir and cleaned a minimum of once a year. Years ago, a plant sought out help to troubleshoot a system that had already had five pumps changed within a single week. Upon closer inspection, it was discovered that the breather cap was missing, allowing dirty air to flow directly into the reservoir.

A check of the hydraulic schematic showed a strainer in the suction line inside the tank. When the strainer was removed, a shop rag was found wrapped around the screen mesh. Apparently, someone had used the rag to plug the breather cap opening, and it had then fallen into the tank. Contamination can come from a variety of different sources, so it pays to be vigilant and responsible with our practices and reliability measures.

The electric motor is driving the hydraulic pump at a speed that is higher than the pump’s rating. All pumps have a recommended maximum drive speed. If the speed is too high, a higher volume of oil will be needed at the suction port.

Due to the size of the suction port, adequate oil cannot fill the suction cavity in the pump, resulting in cavitation. Although this rarely happens, some pumps are rated at a maximum drive speed of 1,200 revolutions per minute (RPM), while others have a maximum speed of 3,600 RPM. The drive speed should be checked any time a pump is replaced with a different brand or model.

Every one of these devastating causes of cavitation threatens to cause major, irreversible damage to your equipment. Therefore, it’s not only critical to have proper, proactive practices in place, but also a monitoring system that can continuously protect your valuable assets, such as UE System’s UltraTrak 850S CD pump cavitation senor. These sensors regularly monitor the health of your pumps and alert you immediately if cavitation symptoms are present, allowing you to take corrective action before it’s too late.

Aeration is sometimes known as pseudo cavitation because air is entering the pump suction cavity. However, the causes of aeration are entirely different than that of cavitation. While cavitation pulls air out of the oil, aeration is the result of outside air entering the pump’s suction line.

Several factors can cause aeration, including an air leak in the suction line. This could be in the form of a loose connection, a cracked line, or an improper fitting seal. One method of finding the leak is to squirt oil around the suction line fittings. The fluid will be momentarily drawn into the suction line, and the knocking sound inside the pump will stop for a short period of time once the airflow path is found.

A bad shaft seal can also cause aeration if the system is supplied by one or more fixed displacement pumps. Oil that bypasses inside a fixed displacement pump is ported back to the suction port. If the shaft seal is worn or damaged, air can flow through the seal and into the pump’s suction cavity.

As mentioned previously, if the oil level is too low, oil can enter the suction line and flow into the pump. Therefore, always check the oil level with all cylinders in the retracted position.

If a new pump is installed and pressure will not build, the shaft may be rotating in the wrong direction. Some gear pumps can be rotated in either direction, but most have an arrow on the housing indicating the direction of rotation, as depicted in Figure 2.

Pump rotation should always be viewed from the shaft end. If the pump is rotated in the wrong direction, adequate fluid will not fill the suction port due to the pump’s internal design.

A fixed displacement pump delivers a constant volume of oil for a given shaft speed. A relief valve must be included downstream of the pump to limit the maximum pressure in the system.

After the visual and sound checks are made, the next step is to determine whether you have a volume or pressure problem. If the pressure will not build to the desired level, isolate the pump and relief valve from the system. This can be done by closing a valve, plugging the line downstream, or blocking the relief valve. If the pressure builds when this is done, there is a component downstream of the isolation point that is bypassing. If the pressure does not build up, the pump or relief valve is bad.

If the system is operating at a slower speed, a volume problem exists. Pumps wear over time, which results in less oil being delivered. While a flow meter can be installed in the pump’s outlet line, this is not always practical, as the proper fittings and adapters may not be available. To determine if the pump is badly worn and bypassing, first check the current to the electric motor. If possible, this test should be made when the pump is new to establish a reference. Electric motor horsepower is relative to the hydraulic horsepower required by the system.

For example, if a 50-GPM pump is used and the maximum pressure is 1,500 psi, a 50-hp motor will be required. If the pump is delivering less oil than when it was new, the current to drive the pump will drop. A 230-volt, 50-hp motor has an average full load rating of 130 amps. If the amperage is considerably lower, the pump is most likely bypassing and should be changed.

Figure 4.To isolate a fixed displacement pump and relief valve from the system, close a valve or plug the line downstream (left). If pressure builds, a component downstream of the isolation point is bypassing (right).

The most common type of variable displacement pump is the pressure-compensating design. The compensator setting limits the maximum pressure at the pump’s outlet port. The pump should be isolated as described for the fixed displacement pump.

If pressure does not build up, the relief valve or pump compensator may be bad. Prior to checking either component, perform the necessary lockout procedures and verify that the pressure at the outlet port is zero psi. The relief valve and compensator can then be taken apart and checked for contamination, wear, and broken springs.

Install a flow meter in the case drain line and check the flow rate. Most variable displacement pumps bypass one to three percent of the maximum pump volume through the case drain line. If the flow rate reaches 10 percent, the pump should be changed. Permanently installing a flow meter in the case drain line is an excellent reliability and troubleshooting tool.

Ensure the compensator is 200 psi above the maximum load pressure. If set too low, the compensator spool will shift and start reducing the pump volume when the system is calling for maximum volume.

Performing these recommended tests should help you make good decisions about the condition of your pumps or the cause of pump failures. If you change a pump, have a reason for changing it. Don’t just do it because you have a spare one in stock.

Conduct a reliability assessment on each of your hydraulic systems so when an issue occurs, you will have current pressure and temperature readings to consult.

Al Smiley is the president of GPM Hydraulic Consulting Inc., located in Monroe, Georgia. Since 1994, GPM has provided hydraulic training, consulting and reliability assessments to companies in t...

Dry running a pump can cause all kinds of serious problems, yet many operators are unaware of the dangers. When a pump runs dry, it generates heat and force it was never designed to handle, leading to wear and tear that can quickly add up to inflated repair costs. Avoiding dry running is highly important, but it makes sense to learn how negative it can be in order to fully understand the severity of the phenomenon.

When a pump runs dry, it runs without any liquid going through it. This is always a bad idea, as it puts an inordinate amount of strain on the pump’s moving parts.

Instead of circulating fluid, a dry running pump pushes nothing but air around, leading to friction, heat, and destruction of delicate internals. A hydraulic pump is normally designed to run while filled with fluid. As it runs, the fluid inside it helps to preserve its internal pieces, cooling them and even assisting in centreing moving elements such as the rotor.

Pumps that operate at particularly high pressure can suffer considerable cavitation simply from fluid-derived vapor; completely dry running a finely tuned pump is significantly worse for its longevity. Even self-priming pumps should only be run once the proper amount of fluid is inside, as they can withstand only partial dry conditions while priming themselves.

Running your hydraulic pump dry is likely to result in disaster, wearing it out prematurely via the aforementioned heat, violent vibrations, or complete lock-up/seizure of important parts, costing you money to fix or replace.

Running a hydraulic pump dry can lead to a large variety of issues with the pump’s parts and the rest of your hydraulic system as well. Here are a few common problems that dry running can cause:

High temperatures caused by dry running can ruin your pump, pitting its housing and causing leaks.¹ If heat and pressure are excessive enough, the housing boss may deform, potentially stopping your impeller from rotating freely and rendering your pump functionally useless. In many cases, a severely damaged, leaking pump is likely to need replacing, which can run your costs up much further than anticipated.

As is the case for the housing of your pump, the impeller is susceptible to damage done by excessive heat during use. Dry running your pump causes friction, and this friction is strong enough to heat up the impeller, causing it to melt.² Even minor melting is severely detrimental to your pump’s performance, potentially causing it to seize up and stop working at all. Taking it apart for repair is usually an involved and costly exercise best avoided through preventive operating practices.

Internal wear caused by dry running your pump can lead to additional wear throughout the entirety of your system. This is generally caused by either excessive heat or metal particles scraped from disintegrating moving pieces within your pump travelling through the rest of your system. Metal particles, in particular, can cut and clog valve components, pipes, and tubes, leading to system failure over time.

You may need to run your pump dry for short periods of time to empty the system completely, but it is best to keep such instances as brief as possible. Once your tank or system has been emptied by the pump, it should be turned off. Do not allow it to keep running for more than a minute without any fluid.

Keeping someone in charge of monitoring your pump as it runs can help avoid unintended dry running problems. Often, a pump may be left running until a job is completed. If the pump performs its function faster than intended and all fluid is purged from the system, it will run dry and damage itself until an operator returns to turn it off. Having someone manage the pump at all times is crucial to keeping it functional.

Some companies have found an automatic means of controlling their pumps’ functions from afar. By leveraging special protective devices and control systems, it is possible to automatically stop a pump that is in danger of running dry, preserving its internal parts and averting expensive disasters.³ However, such devices incur an additional cost.

At White House Products, Ltd., we offer all manner ofpump parts to patch up a system damaged by dry running. We can also provide complete replacements as needed. Call our technical support team at +44 (0)1475 742500 to learn how we can help get your pump working again.

Every year, air operated double diaphragm (AODD) pump users spend thousands on electricity, replacement parts and labor because they dry run their pumps. Unlike many other types of pumps, AODD pumps can run dry (run without being fully primed) without immediate damage. Therefore, they are useful in applications such as sumps and tank transfers in which the liquid may unexpectedly run out.

Routinely relying on an AODD pump’s ability to run dry, however, can incur substantial costs—including energy loss, increased maintenance and lost compressor capacity. This article details these costs, the prevalence of dry-running pumps and solutions for running a greener and more cost-effective operation.

When a pump runs dry, 100 percent of the consumed air is wasted. Although lost energy from wasted air is the most obvious cost, additional maintenance, downtime and lost compressor capacity are also significant.

As seen in Table 1, the yearly dry-running costs can exceed the cost of the original pump. Furthermore, the air and maintenance costs are often much higher, as a dry-running pump can operate two to three times faster than it does when under load. This means more air usage and faster wear and tear on the pump.

While the direct pump and compressed air costs are substantial, the associated costs can be just as high. A few 70 standard cubic feet per minute (scfm) “leaks” in an air system represent a significant drain on a compressor, requiring plant engineers to consider increasing the overall system pressure, or increasing the size and number of compressors. Frequent and unexpected pump failures can also lead to product loss and production downtime, both of which can match the air and maintenance costs.

Despite the high cost of dry-running pumps, the practice is a common occurrence in many factories. Some typical causes and observations seen at several factories are described in this section.

A chemical factory needed to rebuild one to two pumps every month. Given the number of pumps that the factory had and the amount of time the pumps needed to be in use, only one to two rebuilds per year should have been required. The parts cost per rebuild was $300 to $500 plus labor, and the maintenance bills were adding up quickly.

Operators unintentionally left the pumps running throughout the weekend. Because the plant’s energy or maintenance bill was not included on performance reviews, the operators had little incentive to remember to turn off the pumps.

The same pattern is repeated in other factories.  Another example is a large paint factory at which workers use pumps to empty large tanks. Again, operators would turn the pump on, get distracted by other tasks and forget to turn them off.

Because AODD pumps are often used in “dirty” situations—outside or in waste sumps in factory floors—debris or corrosion frequently cause level sensors to fail. Non-contact types are susceptible to debris or being dislodged as well.

In many of the observed factories, sumps had level sensors that were bypassed because they were not reliable enough. In these cases, the sump pumps operated 24 hours per day, despite the sump filling only occasionally. By equipping two of their pumps with monitoring equipment, the operators discovered that a 2-inch pump was only pumping liquid 32.8 percent of the time, and a 1-inch pump only 7.3 percent of the time. More than half of their energy and maintenance bill was being used to needlessly pump air.

Whether the cause is operator error, a failed level sensor or simply installing a pump to run non-stop when unnecessarily, dry-running AODD pumps appear to be a common occurrence.

Although dry-running pumps can be costly, several solutions, ranging from inexpensive procedure changes to sensor-based control solutions, can reduce costs substantially. Most of these solutions will show a return on investment within six months to one year, depending on the frequency of dry running.

If personnel are informed of the true cost of dry-running pumps, including the resulting increase in maintenance, they can work individually to avoid leaving pumps running unnecessarily. Adding dry-running observations to maintenance records can help diagnose the root cause of pumps that require frequent rebuilding. Routinely checking sump level sensors for correct operation can also help to avoid long stretches of dry-running operation.

A myriad of level sensors and controllers can be used to turn pumps off when they are not needed. Inexpensive, simple float-trigger switches indicate when a tank or sump level is too high or low, turning the pump on or off as required. Because floats can easily become obstructed by debris, many float-less types—such as capacitive (both contact and non-contact), radar and ultrasonic—are other options.

When considering level sensors, end users should evaluate the whole system cost because many sensors require an additional solenoid and, in some cases, a separate programmable logic controller (PLC). Installation requirements for all the separate components should also be taken into account. Unfortunately, since many level sensing solutions are in contact with the pumping liquid, they suffer from corrosion or clogging. Even non-contact sensors can be blocked by debris or dislodged.

Another category of controllers that avoids the problems of level detection devices is air monitoring controllers. Air monitoring controllers work similarly to load-monitoring controllers on electric motors, turning the pump off when the air input indicates that the pump is running dry.

Some controllers in this category rely only on mechanical switches, while others use electronic controls. The mechanical controllers typically detect a change in pressure or flow to determine when a pump is running dry. Because a dry-running pump faces little to no resistance, it operates faster and uses more air than when transferring liquid.

While mechanical controllers have the benefit of operating without power, they can be unreliable when plant conditions change, such as the input or pump discharge pressure.

Air monitoring controllers with electronics can employ more sophisticated logic to compensate for changing environments, and also better detect when a pump is truly running dry.

Some of these solutions use pressure sensors to listen to the pump like a stethoscope to detect the individual stroke rate, which typically changes much more than the air input rate.

Dry-running AODD pumps are a costly problem that can easily go unnoticed, wasting significant energy, money and maintenance resources. Since many people are unaware of the high cost, dry-running pumps are a common occurrence in many factories. Fortunately, many solutions are available that provide a fast return on investment, ranging from simple maintenance procedural changes to controllers that automatically turn off pumps when they are not needed.

The gear pump is a PD (Positive displacement) pump. It helps to develop a flow by carrying the fluid between repeatedly enclosing interlocking gears or cogs, transferring it automatically using a cyclical pumping action. So, the Gear pump provides a smooth pulseless fluid flow of which rate depends on its gears’ rotational speed.

The gear pump uses the rotating gears or cogs’ action to move fluids. Its rotating part forms a fluid seal by the casing of the pump and creates the suction at the inlet of the gear pump. Fluid pulled into a gear pump is surrounded within the rotating gears or cogs cavities and shifted out to discharge.

External design Gear pump contains two identical and interlocking gears that are supported through separate shafts. The motor is used to drive the first gear which drives the second gear. In a few cases, electrical motors can drive both shafts that are supported with bearings on every side of the casing.When gears move out from the mesh on the pump’s inlet side, they form an extended volume, Fluid flows into the pump’s cavities and entrapped by the edges of gear while gears carry on rotating against the casing of the pump.

The fluid cannot be transferred back over the center, amongst the gears, as they got connected. Close tolerances amongst the casing and the gears let the external gear pump to extend suction over the inlet and prohibit fluid from going back from the pump’s discharge side (Though the low viscosity fluids have more tendency for fluid leakage).

The Internal Design Gear Pump works the same as of External Design Gear Pump except that it’s both interconnected gears have different sizes where one rotates inside of others. It has a larger internal gear which is called the rotor i.e. its edges projecting from the inside. The other external gear of small size mounted into the center of the rotor which is called the idler. It is designed for interconnecting with the outer rotor in a way that edges of gear engage at the one end. The bushing along with a pinion is attached to the casing of the pump which holds inner idle into its location. A crescent shape fixed divider fills the vacant place which is created by the idler’s irregular mounting position. It works like the seal amongst outlet & inlet ports.When gears move out from the mesh on the pump’s inlet side, they form an extended volume, fluid flows into the pump’s cavities, and entrapped by the edges of gear while gears carry on rotating against the partition and casing of the pump.

The gear pump has few moving parts and is very simple and compact. Its pressure power cannot be matched with reciprocating pumps or the rates of flow of the centrifugal pumps. Yet it provides higher throughputs and pressures than lobe pumps or vanes. The gear pump is specifically suitable for fluids of high viscosity and pumping oils.

From the two types of gear pump, the external design has the ability to sustain high flow rates and pressures (more than 3000psi) due to its closer tolerances and stronger shaft support. Internal design provides better suction. It is suitable for fluids of high viscosity but it provides an operating range of 1cp to more than 1,000,000cp. As output depends on the rotational speed, the gear pump is mostly used for blending and metering operations. The gear pump can also be engineered for handling the aggressive liquids. Whereas it is generally made from stainless steel or cast iron, new composites and alloys let the pump handle the corrosive fluids like sodium hypochlorite, sulphuric acid, sodium hydroxide, and ferric chloride.

The external design can be used in lifting machinery, hydraulic power, plant equipment, and vehicles. When the gear pump is driven in reverse, by using the oil which can be pumped from anywhere in the system (generally through a tandem pump within an engine), creates the hydraulic motor. It can be beneficial for providing power in those fields where the electrical system is costly, inconvenient, or bulky. For example, a tractor depends on an external design engine-driven gear pump to power its services.

The gear pump is self-priming yet it can also dry lift, though its priming features can be enhanced by wetting the gears. The gears should not run dry for a prolonged period and must be lubricated through a pumped fluid. Some designs of gear pumps can be operated in both directions (forward or reverse). Since the same gear pump can be utilized for loading and unloading the vessel, for instance.

Close tolerance amongst the casing and gear means that this pump type is vulnerable to wear especially when feeds consisting of entrained solids or the abrasive fluids are used. Though, few pump designs, specifically internal variants that let to handle the solids as well. The external design gear pump has four bearings with tight tolerances. Therefore, it is less suitable to handle abrasive fluids. The internal design gear pump is more robust and has just one bearing (maybe two) to run in a fluid. The gear pump needs to install a strainer on a suction side that can protect it from potential damages of solids.

In general, when a gear pump requires for handling abrasive solids then it’s better to choose a pump with higher capacity that can be run at low speed to avoid wear. But it must keep in mind that the gear pump’s volumetric efficiency becomes lessens at low flow rates and speeds. The gear pump must not be run beyond the recommended speed.

In applications of high temperature, it’s necessary to make sure that an operating range of temperature is compatible along with the specification of the pump. Gears and casings’ thermal expansion lessens clearances in the pump which can lead towards increased wear as well as in extreme circumstances, pump failure.

In spite of the best precautions, the bearings, casing, and gears of the pump succumb to wearing with every passing day. As there is an increase in clearances, a gradual decrease in efficiency happens along with an increase in the flow slip: pumped fluid’ leakage from the expulsion back towards a suction side. The flow slip depends on the clearance’ cube between the casing and cog edge so, practically, wear provide a small impact till a critical stage is reached after which the performance of the pump degrades rapidly.

Gear pumps continue to pump in contrary to reverse pressure then, if downstream blockage happens, it will carry on to the pressurized system till the pipework, pump, or other parts fails. Due to this reason, some gear pumps are used to equip with the relief valves. It’s advisable to use a relief valve anywhere within a system for protecting the downstream equipment.

The internal designs gear pumps that operated at less speed are considered ideal for the shear-sensitive fluids like paint, soaps, and foodstuffs. The lower clearances and higher speeds of eternal design gears make them appropriate for these kinds of applications. The internal design gear pump also prefers where hygiene conditions are more important due to its mechanical simplicity. This is a fact that it has easy to clean, strip down, and reassemble features.

Gear pumps are appropriate for pumping the fluids of high viscosity like foodstuff, oil, paints, or resins. They are used in any kind of application where the output of high pressure or accurate dosing is required. The gear pump output is not affected too much by pressure and they can be used in any type of situation where irregular supply occurs.

The gear pump helps to develop a flow by carrying the fluid between repeatedly enclosing interlocking gears or cogs, transferring it automatically to smooth pulseless flow of which rate depends on its gears’ rotational speed. Two basic design types of gear pumps are external design and internal design.

External design Gear pump contains two identical and interlocking gears that are supported through separate shafts. The Internal Design Gear Pump has two interconnected gears having different sizes where one rotates inside of others.

Gear pumps are appropriate for pumping the fluids of high viscosity like foodstuff, oil, paints, or resins. They are used in any kind of application where the output of high pressure or accurate dosing is required. The external design gear pump is used to sustain high pressure (more than 7500 psi) while the internal design gear pump provides better suction and is more suitable to fluids which are shear sensitive and of high viscosity.

Hydraulic pumps serve key functions in your hydraulic system. Without them, the system could never supply its mammoth output. Overall, hydraulic pumps offer many advantages over other pump types. They function efficiently and have low maintenance requirements. While hydraulic pumps have always been reliable, manufacturers continue to invent improvements.

Hydraulic pumps convert their mechanical energy into hydraulic energy. Their operation within a hydraulic system serves two functions. Firstly, their mechanical action generates a vacuum located at the pump inlet. The atmospheric pressure pushes the liquid out of the reservoir, through the inlet line, and into the pump. Secondly, the hydraulic pump’s movement forces this liquid into the pump outlet and then out into the hydraulic system.

Hydraulic pumps produce liquid flow rather than generating pressure. However, this flow serves an essential role in building the pressure that transports the fluid through the system. For instance, when the pump is disconnected, the fluid pressure at the pump outlet remains at zero. When the pump delivers fluid into the system, the pressure rises to the intensity needed to overcome the load resistance.

Hydraulic pumps can move large volumes of liquid over long distances with minimal energy consumption. This ability had made them popular for transporting both gasses and liquids. In addition, they have low maintenance requirements compared to other pump types. Also, hydraulic pumps have excellent safety records and require little labor.

Over time, manufacturers worked to improve hydraulic pumps, making them more energy-efficient, increasing runaway control, and reducing maintenance costs.

In general, hydraulic pumps consume less energy than other types of pumps to complete the same output or volume of liquid or gas. In fact, many hydraulic pumps rate as 80% more efficient than pneumatic-style systems.

Today’s latest hydraulic pumps boast even more efficiency versus earlier iterations. As a result, organizations’ overall cost of operating hydraulic systems has lessened. Additionally, increased efficiency leads to shorter job times, allowing faster production. Lastly, more efficient hydraulic pumps take less mechanical stress while operating, allowing for longer life cycles and lower maintenance costs.

Hydraulic pumps, on the other hand, very seldom run dry. Pneumatic systems are harder to monitor in terms of speed and flow. Hence, operators often fail to notice a runaway system until the damage has already resulted, causing valuable time to be lost.

Today’s hydraulic systems comes with readily recognizable excessive speed and flow warnings. Because monitoring them is simple, busy operators are never caught off guard by a system running dry. By ensuring operators recognize runaway issues, hydraulic pumps prevent resultant seal and package damage as well as internal part breakage.

All machines require routine maintenance to continue functioning efficiently and avoid breakdowns. As your vehicle needs oil changes, brake jobs, tire rotations, and transmission service, hydraulic pumps must receive scheduled maintenance to prevent loss of power and component deterioration. However, overall maintenance costs for hydraulic pumps are substantially less than other pump types. Much of this benefit is owing to their self-lubricating setup.

Because of self-lubrication, they lack many difficulties associated with other pumps, such as compressed air models. Lacking self-lubrication, these types of pumps suffer increased susceptibility to moisture, areolated oils, scale, and rust. In addition, self-lubrication eliminates the problems of icing, which can wreak havoc when the pump’s cycles result in the cooling of rapidly exhausting compressed air.

Over the previous years, you have probably noticed that vehicle maintenance requirements have grown less frequent. Better technology allows for parts to last longer with lower maintenance. The same is true of hydraulic pumps. As a result, manufacturers have endeavored to create more efficient models with longer-lasting components. The result is hydraulic pumps that last longer with less attention.

Hydraulic pumps are your best friend when you need reliable hydraulic system production. They provide the ceaseles