How to choose and use hydraulic cylinders safely?
- Issue Time
Many of the failures in a hydraulic system show similar symptoms: a gradual or sudden loss of high pressure, resulting in the loss of power or speed in the cylinders. In fact, the cylinder may stall under a light load or may not move at all. Often the loss of power is accompanied by an increase in pump noise, especially as the system tries to build up pressure. Any major component, including the pump, the relief valve, directional control valve, or the cylinder, could be at fault. In a sophisticated system, other components could be to blame, but this could require the service of an experienced technician. By following an organized step-by-step testing procedure in an orderly fashion, the problem can be traced to a general area, and then if necessary, each component in that area can be tested or replaced. We want to discuss the safety tips concerning cylinder design and use. What are some of the suggested things we should be looking for when selecting the right hydraulic cylinder for the job? Answering these questions before installation is a great start to safe and optimal cylinder design.
– Is the hydraulic cylinder rated for the work to be done? Using the F = P x A formula (Force = Pressure x Area of the piston) will ensure that the cylinder is sized properly to do the work at the required system pressure.
– Is the cylinder designed to handle the load? With so many hydraulic cylinder manufacturers today, choosing a replacement cylinder that will hold up to the load requirements is important. Be sure to evaluate the cylinder seals and guide bands compatibility being used. Agricultural equipment typically uses ag-type hydraulic cylinders that feature cast end covers bolted together with bolts and nuts onto a honed tube (tie-rod cylinder). They also typically use O-rings for seals. These cylinders generally operate at 1,500 – 2,500 PSI and are designed to be either quickly resealed in the field or thrown away. Using tie rod cylinder in a construction application would prove to be dangerous and self-defeating as it would have a short life span for the work to be done and may not hold up under the load requirements.
– Tie-rod or welded? When is it appropriate to use a tie rod cylinder or a welded cylinder? The typical response is that manufacturers of stationary equipment generally rely on tie-rod cylinders, as they can be configured to fit most unique applications and have many applicable valving blocks, making them simpler to configure for machinery. This reduces other possible needed valves to accomplish work desired and helps to reduce costs. Rated to NFPA standards, tie-rod cylinders are easily inter-changeable with other manufacturers. Welded hydraulic cylinders are the most common in mobile equipment where weight and size of application work needs can be considered. These heavy-duty designs are usually rated at 2,500 – 5,000 PSI or even higher. Featuring a barrel that is bolted or welded directly onto the end caps, these designs do not require tie-rods, so these cylinders are much stronger and more resilient in harsh environment.
It is important to be sure to use a hydraulic cylinder that is rated for the needed job. Choosing a cylinder because of the cost rather than design can be a mistake in many ways. Pressure seals, wear bands, rod seals, and porting all play an important part of the selection.