Hydraulic Actuator Test

Experiment with a Hydraulic actuator

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Suggested exercises and observations

1. Consider a hydraulic system you work with or use your worked project application as an example.

♦ Identify which type of cylinder is being used, e.g. welded, tie rod or mill. Or consider a welded cylinder performance.

♦ Check the maximum pressure rating of the cylinder against the maximum working pressure seen in the system (supply or intensified pressure).

♦ Check the safety factor by comparing the design with actual pressure ratings. (Note! Manufacturers will have built-in a design safety factor so 1 is acceptable.)

♦ If 1 million cycles is approximately when the seals will need to be changed. Work out when that might be in months or years.

♦ Compare with actual data from your equipment or predict how dirty the environment is and how much this will reduce the life of the seals.

♦ Consider how best to store the cylinder when the equipment is not running e.g. so that the rods are protected by the fluid. Remember that not having an unsafe, unsupported load is the first priority.

Sample cylinder datasheets

Experiment 1: Cylinder rod seals are one of the key contamination entry points.

Question 1: Why are rod seals so important for the reliability of the whole system?

Over 80% of component failures are caused as a result of dirt in the fluid. Rod seals are one of the main areas where dirt will enter the fluid.

Experiment 2: Every time a cylinder extends a tiny film of fluid is left on the cylinder rod.

Question 2: Why is it best to keep the cylinder retracted as much as possible e.g. when not being used?

Dirt sticks to the extended rod fluid film and is passed into the fluid when it retracts. Storing the rod with it retracted means that less dirt will stick to it and the rod remains protected by the oil, no matter how long the system is at rest.

Experiment 3: Cylinder cushions can be fitted to one or both ends of the cylinder.

Question 3: What function do cylinder cushions provide?

They slow the cylinder as it reaches the end of its stroke. This provides an effective deceleration of the cylinder movement and significantly reduces shock loadings on the framework.