The importance of hydraulic relief valves
A recent blog looked at some of the hydraulic valves offered by Yuken (Europe) all of which were CETOP valves (the interchangeable valves used in most hydraulic equipment today) but that blog focused mainly on directional control and flow control valves and their functions. Here, we will look at relief valves and the importance of their function, and why those working with hydraulic systems need to know and understand how they work and what their proper uses are.
A pressure relief valve is extant in hydraulic equipment to serve the most basic yet fundamental function of limiting and relieving pressure in a system when it is too high. Without this, pressure would build up and could cause expansive or irreparable damage to equipment, costly replacements and the potential for serious harm or worse to anyone in the area of the equipment should the pressure blow. Unfortunately, this awareness is as much as many machine operatives have, unless they are trained or have qualifications in hydraulic engineering. Every time machinery experiences a pressure issue, particularly a loss of pressure, instinct is to adjust the pressure relief valve, now while this may address the issue temporarily, it is not fixing the root cause of any pressure issues.
When the pressure valve is ‘adjusted’ by several people over the course of a working week or even just a long shift, each person thinks they are “fixing” the pressure issue, making it is easy for the valve to be restricted down to a dangerous level without people realising until the pressure issues continue and finally an engineer might be called in. Unfortunately, by this time substantial damage (not to mention the risk of explosion) to the equipment could have taken place that cannot be seen until the machinery is opened up. A system or reporting process should always be in place regarding any loss of pressure in hydraulic machinery so that the person responsible for the maintenance of hydraulic equipment, is informed not just “fixed” by an operator.
With the knowledge that any pressure relief valves have probably been adjusted by someone with little or no training, a hydraulic engineer will be able to check any settings, as well as the adjustability of the relief valve to see what has taken place. All relief valves should then be checked to ensure they are still in working order, and replaced if not. Once the pressure relief valve has been looked at, it will become apparent to an engineer whether this is hiding a bigger problem that needs addressing in the hydraulic machinery elsewhere. Quite often, the most likely culprit will be a leak or a seal issue that has been causing the drop in pressure that originally led to the pressure relief valve being altered. Once the hydraulic machinery has been returned to its fully working function, it is important to take further preventative measures, i.e. educating machine operators about the pressure relief valve and why it should not be adjusted frequently in order to address pressure loss issues.
