How Do Hydraulic Vane Pumps Create Pressure?
Hydraulic vane pumps create pressure by forcing hydraulic fluid into an ever-smaller area before releasing it back into the system. This is achieved through a combination of sliding vanes, inlet and discharge holes, and a drive shaft that’s off-center compared to the chamber.
Fluid is pushed through inlet holes and into the chamber of the pump by the atmospheric pressure acting on the fluid in the reservoir. Once in the chamber, the fluid is collected in the space between two vanes that are connected to the driveshaft and pressed against the external wall of the chamber to form a seal.
Because the drive shaft is off-center in relation to the pump chamber, as it rotates, the vanes are pressed in by the external wall and the space between them becomes smaller. This change in volume increases the pressure of the fluid, which is then forced out of the pump on the other side of the chamber when the pressure is at its greatest.
Advantages of Hydraulic Vane Pumps
Versatility
One advantage of using a vane pump is how it can handle a wide range of low to medium viscosity fluids. This means they can be used by a wide variety of industries to move fluids including, but not limited to:
Alcohols
Solvents
Refrigeration fluids (freons and ammonia)
Aqueous solutions
Aerosols
Fuels and lubricants
Fuel transfers and de-icing
Maintenance
The internal system of a vane pump is highly lubricated with fluid and minimal metal-to-metal contact. This makes these devices relatively easy to maintain, with the vanes being the parts that are the most prone to wear and tear. Luckily, vanes are cheap and easy to replace.
Running Volume
One potential safety issue in many industries is the noise level in the workplace. Thankfully, a pump that is running with no issues is quiet. So making use of them in a manufacturing facility helps keep the noise down, or at least does not add to it.
Reliability
When properly constructed and maintained, a hydraulic vane pump is a highly reliable piece of equipment. It has the potential to last a very long time. In fact, it could last you a lifetime. That is why it is important to take care of it and know what to look for as far as signs of problems.
Limitations of Hydraulic Vane Pumps
Ship hydraulics
Like everything else, these systems have their limits. No instrument, substance, or part will suit the needs of every job. A hydraulic vane pump typically does not do well with the processing of very high viscosity fluids. It also will not handle excessively high pressures or abrasive fluid contaminants.
Common Cause of Failure: Dirty Fluid
Industry insiders have calculated that dirty fluid is either directly responsible or at least a contributing factor to over 80 percent of all hydraulic vane pump system failures. It does not matter how well-constructed your hydraulic vane pumps are or how tight the seals are if you are running fluid with abrasive contaminants through them. Running these abrasive fluids through a pump at high speeds will wear down the vanes and affect other parts such as the rotor and cam.
One answer to this problem is installing and maintaining contamination control devices to make sure your fluid is kept clean. Do not assume that just because you have purchased a new fluid that it will automatically be clean. Having a filtration system in place is a must.
Another step against this problem is to have quality control checks. If improperly handled by the distributor or the manufacturer, new fluid can have significant levels of impurities. Do not introduce the fluid into your system until you’ve filtered it first and it passes a purity check.
Sometimes the contamination of the fluid may not come from the fluid distributor or manufacturer but from the machine itself. Just as we explained about fluid, the fact that your machine is new does not guarantee its cleanliness. So, when you purchase new equipment, you should clean it before beginning operations to avoid contamination to your pump and adjoining parts or systems.
The cost of filtration systems, quality control checks, and basic cleanliness in fluid and machines will more than pay for themselves over the years. Over time, the increased production resulting from not having to shut your line down due to a pump failure and needing less frequent repairs will result in higher profit.
Common Issue: Cavitation Damage
Cavitation is when small air bubbles manifest in your pump’s fluid and then implode. It seems like a relatively benign issue at first glance, but it can cause extensive damage to your hydraulic vane pump after some time.
The implosion of air bubbles in the hydraulic fluid can generate a massive amount of heat. This is a problem for two reasons. First, if the temperature gets too high, it can cause the hydraulic fluid itself to break down and be less effective. Second, the temperature and pressure differences caused by the implosions can wear down the metal components within the pump.
Both the wearing of internal metal components and the loss of the hydraulic fluid’s ability to properly lubricate parts of the pump can lead to metal chips and other contaminants entering the fluid. Once this happens, a snowball effect begins and the damage will exponentially get worse over time.
Cavitation Causes
The most common cause of cavitation damage is air intruding into the system. Common sources of air intrusion are the following conditions:
Low oil level
Undersized reservoir
Inadequate sealing
Suction line fault
Reservoir inlet too high
Another cause of cavitation damage is when excess force and pressure are placed on the fluid. If these forces are high enough to cause separations in the fluid, small air voids will begin to form. Much like the bubbles, these voids will implode and, as a result, generate excess heat.
To prevent this from happening, make sure your inlet velocity is at the optimal level. Check to see that there are no restrictions on your fluid flowing through the system. Do not run your system over the recommended rpm level. And check your filters to be sure they are not clogged.
Signs Hydraulic Vane Pumps Are Failing
Although hydraulic vane pumps are highly reliable and durable, malfunctions and breakdowns can happen.
Noisy Operation
As we mentioned above, one of the hallmarks of well-running hydraulic vane pumps is quietness. If you hear knocking or banging from the inside, you’re either dealing with the presence of air or extremely low pressure in your pump. Therefore, unusual noise (that isn’t a simple hum or regular “operating” noise) is almost always a sure sign that something is wrong. Loud whirring sounds are also often present when there has been extensive damage.
Leaking
If you notice external leakage around the pump, that points to a failure of one or more seals. Sometimes, this can also mean a bent rod. If the damage is not too extensive, you can have this problem fixed.
Poor Performance or Excessive Heat
Maybe you’re noticing your hydraulic vane pumps have been less efficient, combined with sudden and frequent pressure drops in the pump. There may also be excessive heat. When you notice any of these symptoms, it is time to have your systems checked out by a professional technician.
Problems with hydraulic vane pumps tend to worsen very quickly due to the nature of their high-speed operation. A few metal shavings can quickly damage the vanes, rotors, and walls and create a ripple effect of problems. Calling attention to it right away may enable you to have it repaired rather than having to buy a replacement.
