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Hydraulic Cylinder Repair

Narayani Karthik
There are many applications that require hydraulic cylinders. Constant usage may lead of the wear and tear of this equipment. In such cases, repair may have to be carried out to restore the working of this machine. Here is some information about the same.
Most of the heavy machinery or your car for that matter works on the principle of hydraulics. Heavy bulldozers, excavators, and forklifts also have these cylinders as an integral part of their machinery. It plays a major role in domestic applications like automotive parts, elevators, and door stoppers.
The concept of a hydraulic system is based on the principle that a force which is applied at one point is transmitted to the destination via an incompressible fluid (e.g., oil).
The best example of this application is the brakes of your car, which are basically a piston driven hydraulic system. When you press the brake pedal in your car, a force is exerted on the brake's master hydraulic cylinder, thereafter the force which is applied is multiplied by the four slave pistons (each at the wheel).
The fluid is then compressed and a linear motion is produced which actuates to press the brake pads against the brake rotor to stop the car.


The entire hydraulic cylinder assembly comprises a pump (generates pressure) and a cylinder (delivers the linear motion). The cylinder is fitted into a cylindrical barrel with a piston and the whole barrel is sealed at both the ends.
Now, the piston's movement is driven by the fluid that is regulated by the pump. So when the pump generates pressure on the incompressible fluid, the piston is pushed up, causing the linear motion as stated.
If the pump sucks back the fluid, the piston is forced down. Now for a greater force, a greater surface area of the piston would suffice, which adheres to the theory of multiplying the force.
There are certain causes which may lead to malfunctioning of the hydraulic cylinder. Here are the reasons and solutions to get a better idea.
A crack in the cylinder indicates that the cylinder needs to be replaced at the earliest. A bent piston rod can also hamper the performance of this system.
Over a period of time due to persistent wear and tear, there is a chance that the seal of the cylinder might break. In such cases, all you have to do is have a graphical layout of the entire assembly (say, a printout) and order for a repair kit from the manufacturer.
To repair a broken seal, locate the seal which can be found around the piston shaft on one end. Unscrew the lid from the shaft entry and loosen the pump to reduce the hydraulic pressure. 
Now detach the piston from the shaft and replace the broken seal with the new ones. Once you are done, run a thorough check on the seal alignment. Oil the parts well and reassemble it entirely.
Similarly, if the piston rings get damaged, disassemble the parts and put a new piston ring from the kit. Remember to oil the system once the repair is done.

Repair Tools

Whenever you indulge in the repair of any machinery, a checklist must be prepared first. What you should repair, must be your first priority. Here are the requisites needed before you go about the task of repairing the cylinder.
Get a graphical layout of the hydraulic cylinder assembly before commencing with the repair.

Get your repair kit which will have new shaft seals. These are nothing but O-shaped rings that cover the inside of the cylinder when the piston shaft pushes into the cylinder.
Lubrication is a very important aspect as far as any machinery is concerned. The piston shaft must be well-lubricated, but remember, there is a specific level of lubrication defined in the manufacturer's manual. Any amount of lubrication more than or less than the desired level may hamper the life of the piston shaft.
Last but not the least, quality of the hydraulic cylinder matters the most. If the cylinder rod is unable to withstand pressure exerted by the fluid, then it might bend, which in turn will cost you more.
Whenever you try your hand at repairing assemblies, make sure you have the manufacturer's manual or the guidance of an experienced mechanic, so that the repairing goes smoothly for you.