Repair and testing of crane valves

Three types of systems are usually used in mobile hydraulic systems. Constant flow systems (CF), constant pressure (CP) and load sensing system (LS).

A constant flow system uses a fixed displacement pump to provide a constant current in the system. When the operator spends part of the flow for the task, the system will push the constant current flow to the control valve. In the valve, the flow is divided, so that part of the flow is transferred to the load and the rest of the flow is sent through the tank to the reservoir. Transferring of the whole flow through the control pressure valve creates heat in the system. The main reasons for choosing a CF system include economic satisfaction, ease of maintenance and troubleshooting, and a reduction in the need for maximum system pressure. CF hydraulic systems are suitable for trucks, some forestry equipment, cranes and tractors.

A constant pressure system of a variable displacement pump with a pressure compensator is used to provide the exact flow required for system operation. In the pressure compensating system always is arranged and controlled, even if the load pressure is not high. When the operator wants to move the load, pump provides flow which is based on the request and opening of the valve and the control and adjustment of the pressure compensator.

A strong advantage of choosing a CP system is that the controls respond quickly, because the system is always under pressure and the system responds instantly to requests. Other types of systems should be pressured to create controls. In this system, the pressure is always high and the pump is the only complicated part of the system (control valve has still a relatively simple technology). CP systems are widely used in railroad maintenance equipment, oilfields and some forestry equipment.

The sensitive load system is designed with a variable displacement pump. When the operator wants to move the load, the system generates the required amount of flow at the system pressure a small amount of extra pressure in addition to the main flow.

The load-sensitive system is less common and less understood compared to the previous two, but it is an efficient way to use energy. Currently, sensitive-load systems are more expensive and complex than the other two systems. Working with these systems are also very difficult and to resolve the problem, it is essential to train their service technicians. However, due to higher investment efficiency and better energy efficiency of these systems, their applications are increasing.

A crane is a device that with a few control moves lifts the load in a vertical direction. Cranes are in many different types. These include truck cranes or overhead cranes used in warehouses or crates, or large cranes, which are called braces, also referred to as tower cranes.

Repair of parts and systems of hydraulic cranes, repair, assembling of all kinds of home or shop lifts, loadings, cars, hospital stretcher, service lifts, shops, home-lift wheelchairs, handicaps, elders, laboratory lifts and elevators van be done by experts of Saman Sanat Pouya Company.