Forklifts use hydraulics in order to lift and carry loads, so poor lifting performance normally indicates that there's a problem with the forklift's hydraulic system. In order to lift a load, the forklift's hydraulic pump needs to force hydraulic fluid into the lift cylinder, where the pressure of the fluid provides the resistance necessary to carry the weight of the load. If leaks occur in the system or the hydraulic components in the forklift are damaged, then the forklift won't be able to generate enough pressure. To find out what may be causing your forklift's poor lifting capability and how you can fix it, read on.
Low Hydraulic Fluid Levels
If the level of hydraulic fluid in your forklift is too low, then it won't be able to generate enough pressure to lift heavy loads. The hydraulic system in a forklift is designed to be completely closed. If your fluid levels are low, it means that there's a leak.
Hoses and seals are common locations for leaks, and you can usually find a leak by wiping your forklift down with a white microfiber cloth — if you pick up any hydraulic fluid on the cloth, it means that your hydraulics are leaking. You'll need to take your forklift to a machine shop to have the leak sealed and the hydraulic fluid replaced.
Leaking Control Valve
The lift cylinder and the tilt cylinder on a forklift are fed by hydraulic fluid running through the main control valve. The valve prevents fluid from flowing back to the tank while the forklift is holding a heavy load. It also slows the rate at which fluid flows back into the tank when you're lowering a heavy load, which is an important safety feature that prevents operators from accidentally lowering a load too quickly.
The valve is held closed by a spring. If this spring becomes worn and loose, the valve may remain open while you're trying to raise a load with a forklift. Hydraulic fluid will slowly leak back into the tank, so you'll lose hydraulic pressure. In order to fix the problem, you'll need to have the control valve inspected and the spring replaced.
Clogged Hydraulic Filter
The hydraulic system in a forklift has a filter that removes contaminants like dust and water from the hydraulic fluid. Hydraulic fluid becomes very hot while it's under pressure, and the high heat will cause water to turn into steam. This can severely damage the hydraulic components of your forklift, so the filter plays an important role in making sure no water ever mixes with the hydraulic fluid.
However, the filter can become clogged with use. This slows down the rate at which hydraulic fluid flows through your system, since the pump in your forklift isn't powerful enough to force fluid through a badly clogged filter. Slow-moving hydraulic fluid has difficulty generating enough pressure to lift loads. Thankfully, you can fix the problem by simply replacing the filter.
Leaking Lift Cylinder
If the forklift's lift cylinder is leaking, it will have difficulty generating pressure. Mechanical wear and tear can cause the seal between the piston and the edges of the cylinder chamber to fail, which means that hydraulic fluid will leak behind the piston when it's trying to push against the fluid within the cylinder. This reduces the amount of pressure it's capable of creating, which reduces lift performance. If your lift cylinder is worn, you'll need to replace it.
When your forklift struggles to lift and hold heavy loads, it's important to take it to a machine shop for hydraulic repairs. A faulty control valve or a leaky lift cylinder can both become safety hazards — if fluid rushes back into the tank and causes the cylinder to rapidly lose pressure, the load that's being held by the forklift will clatter to the ground. For safety, have these problems repaired as soon as possible. Contact a hydraulic repair service for more information.