You’ve researched the many types of actuators and decided a rod-style actuator is the answer for your industrial equipment design. That’s great! But, do you want a hydraulic rod cylinder or a pneumatic rod cylinder? Either style can deliver excellent, reliable performance in the right circumstances, so what’s the difference?
Hydraulic Rod Cylinders
These cylinders are powered by either hydraulic fluid or, sometimes, oil. They are very powerful and able to move and hold very heavy loads (like an elevator) indefinitely. But the seals wear and can leak. Leaking hydraulic fluid can potentially damage other equipment components, contribute to a dirty working environment, or even contaminate whatever is on the production line. Hydraulic components also require a variety of associated parts in order to work, increasing maintenance time and cost.
Pneumatic Rod Cylinders
These products are powered by pressurized air. They are cleaner to operate, which is ideal in situations where pristine working environment is required. Pneumatic cylinders are more efficient, plus they can operate at much higher cycle speeds than their hydraulic cousins.
They are a lot easier to integrate into your overall design than hydraulics because they have fewer associated components. That also makes pneumatic rod cylinders easier and less costly to maintain. In fact, overall operating costs are lower for pneumatic style cylinders.
All that said, compressed air-powered cylinders are usually limited to 100-200 psi so they cannot generate anywhere near as much force as a comparably sized hydraulic rod cylinder because a hydraulic system can produce higher pressure forces of 500 psi and greater. Also, the simple fact that air can be compressed means there is a risk that pressure applied to the cylinder may not be perfectly consistent. This is not critical in all situations, but it can be vitally important for certain applications.
Another potential negative is that the rod that operates the cylinder is round, and so is the borehole it travels through. Over time, the rod can tend to rotate in position ever so slightly, pushing the cylinder out of alignment.
W.C. Branham addressed this issue by designing an innovative pneumatic rod cylinder, which has an oval bore instead of the usual round shape. This eliminates risk of rotation during extension and retraction, making this particular model a sound choice for applications where consistent precision is critical. The low-profile OVLPRO comes in two sizes with multiple configurations available.
The Bottom Line
Remember the story of the tortoise and the hare? Think of a hydraulic rod cylinder as the tortoise — not the fastest tool around, but reliably tough and strong. A pneumatic rod cylinder would be the hare — faster and more agile, but not the right tool when you need major muscle.
That may be all you need to know to determine whether hydraulic or pneumatic is the better way to go. Usually, though, there are other factors that come into play since every industrial design project is unique in its requirements and challenges. If you have questions, need help puzzling through the decision-making process, or suspect you might need a custom-designed rod cylinder, give us a call. We have answers.