What should you know about hydraulic system safety?
What do you need to know to keep yourself and other people safe in the workplace?
Keeping a load safe is dependent upon ensuring that the pressure of fluid is correct. If the pressure of it becomes too high, then it will want to give that energy to other surroundings, and it’s only the soundness of the components that will prevent it from doing so. It will try to escape any way possible and this includes through weak seals, valves or other points of plumbing failure.
The metering devices such as valves, flow controls and counterbalances prevent the fluid from running away. To demonstrate this, a cylinder that is installed with rod down, and tension under load will often have a meter-out configuration to stop the load from taking control of the cylinder
Although this is safe, there is still a risk of the pressure on the rod-side intensifying. If the piston seals get blown by this, then the load will drop.
Some engineers will use a counterbalance to avoid metering out errors from occurring. Although a counterbalance valve is considered to be the same a pressure valve, it is what controls the speed of an actuator. It will control how fast the cylinder moves, even if there is a pressure intensification.
Another situation that can cause a catastrophic failure and even personal injury is a leak in the cylinder hose or tube. If fluid in the actuator exits through a broken conduit, it is no longer able to hold up a load. In the event of a conduit failure, the counterbalance valve will prevent the load from dropping. Another safety function that will hold a load is a pilot-operated check valve. Although it will hold a load indefinitely, it will not be as smooth with control of load induced movement.
The essence of a hydraulic system is pressure. It’s something that is required to make the system as powerful and effective as it is. However, there are many reasons why pressure can easily rise including load spikes, ‘water hammer’, intensification and even thermal expansion. If there isn’t enough control over pressure, then components can fail and seals can give way – leaving the machine to be unsafe. It’s for this reason that the hydraulic system has so many different types of pressure control valves.
Damage can be prevented by limiting pressure with relief valves. They can control the pressure in the main system or in isolated sub-circuits. In some systems, it’s necessary for sub-circuits to operate at different pressure to others. This can be achieved through the use of the pressure reducing valve which is able to limit pressure downstream of itself. It is also able to reduce pressure in situations where the fluid has become too heated and therefore has increased its pressure. In some systems there are a number of valves that will work to ensure that pressure is limited to a safe level in every part of the machine.
In summary, it’s important to control both the pressure and the flow in hydraulic systems. It enables safe operation of the system and movement of loads. Safe employees are everybody’s concern.