TERMS COMMONLY USED

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• Bore - size of the cylinder barrel, in terms of diameter.

• Cushion - an option on a cylinder that decelerates the piston before it reaches the end of stroke. It can be on the extend side, retract side, or both on the cylinder. Too much cushioning adds to the time it takes for the piston to reach the end of the stroke; too little cushioning adds to impact shock.

• Cylinder Barrel -  the body of the cylinder that guides the piston. It also holds the ends in place. 

• Cylinder Head Gland - also known as the stuffing box, this component has more than one purpose: 1) Retaining static and dynamic seals at the head end. 2) Seals off at the end of the cylinder. 3) The support for the rod. 4) The mechanical stop to keep the piston from falling out of the barrel.

• Piston - the piston has many purposes. It retains the primary seal from the extend side and the retract side. This component moves back and forth from hydraulic oil. It is the mechanical means of connecting the rod and moving it in and out of the cylinder. The piston also acts as a guide for one end of the piston rod.

• Piston Rod - also known as the shaft or ram, this is a round instrument moves in and out of the cylinder; it can be solid or hollow. Usually is plated or heat treated to protect it from corrosion and yield better durability.

• Port - how the cylinder is able to have conduits (fluid lines) connected. O-ring Boss (SAE) Port has straight threads as well as an O-ring to seal those threads. With a Pipe Port, the threads are tapered and count on interference between male and female threads to seal it. A 4-Bolt Flange Port relies on 4 bolts to hold the two halves together; It uses an O-ring to seal it. A BSP is a British Standard Pipe Thread.

• Retract - this is the length from pin to pin when the cylinder is completely closed.

• Rod/Ram/Cylinder Shaft - this is round piece that slides in and out of the cylinder. The rod is usually plated or heat treated to protect it from corrosion and yield better durability.

• Seals - There are three types of seals: a positive seal which has the capability to make a non-leakage seal; a static seal that doesn't move; and a dynamic seal which seals a moving surface like a rod or barrel.

• Stroke - this is the travel of the cylinder; Extended length (or pin to pin center) minus the retracted length (or pin to pin center).

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COMMON QUESTIONS

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What is the difference between single acting and double acting cylinders?

Double acting have a port on each end and is supplied with hydraulic fluid for both retraction and extension; With single acting, hydraulic fluid goes through a port at one end of the cylinder. This extends the rod by means of area difference. Gravity returns the piston rod.

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What are some common causes of cylinder failure?

Side loading - Caused by the cylinder being misaligned; This creates an odd force on the piston rod. A side load of enough greatness can cause tube scoring, piston rod and rod bearing erosion, and seal failure.

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Rough or scored rod - If there are rough places on the rod, this can cause damage to the seals and reduce their normal life. This can result in the need for frequent replacement.

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Contaminated Fluid - This can cause untimely rod seal failure. If there are abrasive particles in the fluid, it can damage the seal and piston rod surfaces. A faulty wiper seal can draw in any airborne contaminants. Contamination happen in various ways, but the most common is pulled in from the oil or the pump.

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If you have any other questions, please don't hesitate to give us a call at (205) 648-6272