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How to repair hydraulic cylinder ?

Date:2013 / 09 / 28 author: pageview:88

As we known,hydraulic cylinder repair is an essential skill that must be grasped by people who regularly use hydraulic systems. Now Polaris Fluid Power release a tutorial on hydraulic cylinder repair and it deals with all the major problems with hydraulic cylinders, like hydraulic cylinder seal damage. 

Hydraulic systems are widely used in agriculture, construction and manufacturing industry. Bulldozers, cranes, tractors, loaders, elevators and all such heavy equipment machines use hydraulics. Hydraulic hybrid vehicles are some of the newest developments in hydraulic technology. Hydraulics is an applied science which applies the mechanical properties of fluids to build hydraulic systems that can perform heavy duty mechanical jobs with precision.The hydraulic systems offer power with precise control and versatility . At the core of every hydraulic system is the hydraulic cylinder. It is the central component on which all hydraulic systems are dependent. Therefore, one must learn how to rebuild hydraulic cylinder, as it saves money and valuable time. Knowing hydraulic cylinder repair is a skill worth having under your belt because it's always good to know your tools of trade, inside out. Before we go into hydraulic cylinder repair, let us briefly understand the construction and working of a hydraulic cylinder.

Construction and Working of a Hydraulic Cylinder

Any hydraulic system is made of two parts; the hydraulic pump that generates the pressure and the hydraulic cylinder that delivers the mechanical action in response to pressure. The hydraulic cylinder is a cylindrical barrel fitted with a piston which fluidly moves back and forth. The cylinder barrel is of course sealed from both ends. 

The piston divides the barrel body into two parts; the rod end which is the side from where piston enters the barrel body and the other side which is capped called the cap end. The piston is driven back and forth by the hydraulic fluid, which is mostly oil, introduced by the hydraulic pump. The piston has sliding rings and seals which prevent the leakage of fluid from one part of the piston compartment to the other part. The piston is connected with appropriate mounting arrangement. It conveys piston motion to appropriate moving part of the machine which carries the load. 

The idea behind every hydraulic system working is simple. The pressure applied at one point is conveyed to other point by the use of an incompressible fluid which is usually oil. So when the pump pushes oil into the piston chamber, from the cap side, the piston is lifted up. When oil is sucked back by the hydraulic pump from the chamber, the piston gets pushed down. This is how a hydraulic system works by conveying force through an incompressible fluid. By using pistons of different surface areas, force multiplication can be achieved. A heavier load can be lifted up by relatively lesser force, using this principle!

Hydraulic Cylinder Repair

Now that we know, how a hydraulic cylinder works, we can delve into reasons for why it falls into disrepair condition. Here are some common problems that can break a hydraulic cylinder or cause its malfunctioning. I will outline the possible solutions that can help you rebuild or repair your hydraulic cylinder. Read instruction manuals for the machine supplied by the manufacturers carefully, before going ahead.

Problem 1: Hydraulic cylinder is cracked or piston rod is bent!

Solution: If on observation, you see the cylinder rod is bent or the cylinder barrel is cracked, there is pretty much nothing you can do. It's time to replace the cylinder. Forging a new barrel or straightening the piston rod is beyond your capacity. So if this is the case, repairing the hydraulic cylinder is not possible.

Problem 2: The hydraulic cylinder seal is broken!

Solution: If the shaft seal is broken, it can be replaced. However, an opening of the entire cylinder assembly is necessary. Let us see how we can go about it. Obtain a diagram of the hydraulic cylinder if possible as it will help you in reassembly. These diagrams can be had from the equipment manufacturers and you can also carry a printout. You can order a standard repair kit for your hydraulic cylinder which is supplied by the manufacturing company. It includes spare cylinders, spare seals and other spare parts according to the number and type of cylinders in your machine. 

The assembly of the cylinder varies with machine type. Locate the seal position first. Mostly, you will find it around the shaft on one end. The shaft entry end can be accessed by unscrewing the lid from that side. Then loosen the pipes that transmit the hydraulic fluid into the chambers which will release pressure. This will enable you to remove the shaft which otherwise cannot be removed due to hydraulic pressure. Handle the shaft carefully and take care that you do not scratch it. Detach the piston from the shaft and replace the seal with the spare one from the repair kit. Make sure that the seal is aligned rightly. Oil all parts after fitting and reassemble everything in exactly reverse order.

Problem 3: Piston Rings are damaged!

Solution:If the piston rings are damaged, then they can be replaced too, by the same disassembling procedure, as for the above problem. The Piston rings need to be removed and replaced very carefully. Oil the rings and cylinder assembly before putting back everything together.

If you have a multiple cylinder arrangement, things are more complicated. It is better to consult a qualified technician before going ahead. I hope this article has given you an idea about how to rebuild hydraulic cylinder with ease. Always remember one rule while you are solving mechanical problems, do not proceed without a reason to take a particular action. Also, study the assembly and causative framework of the machine before going for repair. Hydraulic cylinder repair can be a good learning experience for anyone who loves machine design.

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