Explaining Actuators and What is Critical in the Selection

Selection of you components in dealing with actuators is ger-mane to reliability. Let’s take an example that we need to replace a cylinder (linear actuator), with a like item, however it has not performed well or lasted long at all. There are usually reasons for this, and they are misapplication, inadequate selection process, mis-understand the actual need of the function necessary to perform the task. OK, here’s an example, I have a cylinder that is moving a load 24/7 at a rate of 1 cycle per minute. I am using a 2″ bore cylinder (keeping it simple), to push this small load of about 300 lbs http://shiftautomation.com/. Now a 2″ bore cylinder has an area of 3.14 sq in.. Remember force equals area x pressure. Well we know that pneumatics (Air) can only produce about 80-90 psi because of losses in the plant and leaks, etc, etc. If you have only 80-90 psi available this equates to 251-282 lbs of force. The fact that you worked for a while means that you had sporadic episodes of higher pressure.

Get the picture, this was a misapplication in the first place, undersized and designed. To do this work you would need to go to a size of 2 1/2″ bore which at 80 psi would give you 490 lbs of force and would do just fine, although I would even go to a 3″ bore to gain a reliability advantage. The same thing applies to the rotary actuators which rely on area (square inch area) x pressure to perform the work. Without getting overly complicated, the above just gives you examples of what and why proper selection and design is so important.

It has been my experience dealing with a lot of so called fluid power vendors, (those with resell rights for certain products) that there are only a select few who actually hire and train their sales engineers to know what you need and can help you with design and troubleshooting. This article is to caution you as well as explain to you the importance of the above. A lot of people call actuators a commodity item and there are vendors who prey on uninformed clients and customers who just order from them because they have undercut pricing just to get orders.:You have heard of “You Get What You Paid For”, is so true in this instance.

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