You’ve probably heard the term ‘pump pressure’ used in the context of hydraulic pumps to describe the amount of force a pump exerts. What if we told you that was wrong?
Hydraulic pumps don’t actually create pressure, they deliver flow. Don’t worry, we’re about to explain. In this guide, we go over hydraulic pressure vs flow, how the two work together and some best practices for hydraulic pump performance.
What is Hydraulic Pressure?
Let’s start with pressure. Hydraulic pressure is the result of resistance. To understand what we mean, think of a hose. When you open the tap, water will flow easily out of the other end at a steady pace. However, if you cover the end of the hose with your thumb, shrinking the opening, suddenly the water becomes more like a jet, leaving the hose with greater force.
That’s pressure, caused by the resistance of you partially blocking the flow of the water. Hydraulic pressure works in the same way, only inside a closed system. So, if hydraulic fluid leaves a pump and encounters resistance, such as a valve, pressure builds. What causes the pressure is the resistance, not the pump.
What is Hydraulic Flow Rate?
Hydraulic flow rate, on the other hand, is how quickly fluid flows through a system. Hydraulic pumps are rated primarily on the basis of their flow rate, or how quickly they can move fluid.
This is different from hydraulic pressure, which is a measure of resistance. Flow rate is measured independently of pressure.
How Pump Displacement Affects Flow Rate
Displacement is a measure of the volume of fluid that a pump can move (displace) with each rotation. A higher displacement pump will be able to move more fluid with each rotation and will therefore be able to achieve a higher flow rate.
Conversely, a smaller displacement pump will produce a lower flow rate, as the volume of fluid it can move per rotation is smaller.
How Pressure and Flow Work Together
While hydraulic flow and pressure are two separate metrics, they are connected. Pumps with a higher flow rating are more likely to increase system pressure, because they are capable of moving a larger volume of fluid faster. This means more fluid passing through the same space, resulting in a restriction of flow, creating resistance and, in turn, pressure.
Therefore, it’s possible to increase or decrease pressure inside a hydraulic system by choosing a pump with a higher or lower displacement.
Impact of Pressure and Flow on System Performance
Getting the balance between hydraulic pressure vs flow wrong can result in poor performance or even damage to the system. If flow is too low, the system might not accumulate enough pressure to operate properly. You might experience weakened performance or internal damage to the pump itself caused by cavitation.
However, if flow rate is too high, the system can become overpressurised. This can cause seals to fail, fluid to leak and even result in damage to components.
Best Practices for Hydraulic Pump Performance
Maintaining optimal pump performance requires careful monitoring and routine maintenance. Some key best practices include:
- Proper pump sizing – selecting the right displacement of pump is crucial to system longevity, as it will affect pressure regulation
- Filter maintenance – change or clean filters regularly to prevent fluid contamination and utilise good quality filters
- Fluid selection – ensure the fluid used is the correct specification for the system and application
- Pressure monitoring – keep an eye on system pressure and look out for unexpected spikes or dips
- Temperature control – make sure your pump and any associated components have the space and airflow they need to shed excess heat and avoid overheating
- Preventative maintenance – schedule regular preventative maintenance to help identify issues early before they can worsen
Signs Your Hydraulic Pump Needs A Repair
If your pump becomes damaged, there are usually telltale signs. Keep an eye out for common indicators, as early identification can help minimise repairs:
- Unusual noises – one of the easiest signs to identify is unusual noises, so listen out for new or unexpected sounds coming from your pump
- Pressure fluctuations – inconsistencies in system pressure could be a sign your pump is struggling
- Excess or reduced pressure – if the pressure in your system is regularly too high or too low it can indicate issues with your pump
- Poor performance – dips in system performance can be caused by a damaged or failing pump
- Fluid leaks – fluid leaking from the outside of your pump could be a sign of faulty seals or excess pressure
- Contaminated fluid – contamination in your hydraulic fluid might signal internal wear in your pump
How CJ Plant Can Help
At CJ Plant, we specialise in hydraulic repairs. From pumps to control valves, we provide expert diagnosis and repairs for all hydraulic system components. We have more than 20 years of experience, a team of expert engineers and access to high-quality OEM parts.
Our process includes free diagnosis and quoting and we clean and test everything we repair to ensure reliable operation. Our work is also covered by a 12-month warranty for complete peace of mind.
To arrange your free diagnosis and quote, just contact us today by calling 01527 870 793, emailing tracey.jones@cjplant.com or filling out our contact form.