Hydraulic lock is two hydraulically controlled one-way valves used together. It is usually used in the oil circuit of a load-bearing hydraulic cylinder or motor to prevent the hydraulic cylinder or motor from sliding down by itself under the action of heavy objects. When you need to act, you have to supply oil to another road. Only by opening the one-way valve and connecting the oil circuit through the internal control oil circuit can the hydraulic cylinder or motor act. Due to the structure of the product itself, during the movement of the hydraulic cylinder, due to the self-weight of the load, the pressure in the main working chamber will often lose instantly, resulting in vacuum, which will close the one-way valve, and then continue to supply oil, so that the pressure in the working chamber will rise and the one-way valve will open. Due to frequent opening and closing actions, the load will have great impact and vibration during falling. Therefore, hydraulic locks are usually not recommended for high-speed and heavy-load conditions, but are often used in closed circuits with long support time and low movement speed.

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Balance valve, also known as speed limit valve, is often used in variable load mechanism, and the mass or mass moment changes during the operation of equipment, such as cranes, gate hoists, tipping equipment and tipping devices. It can overcome the influence of load change on speed, ensure that the mechanism can continue to run smoothly without impact, and also ensure that the mechanism can be positioned immediately without falling in an emergency. Taking construction machinery as an example, the hydraulic balance valve is one of the important components of the hydraulic system of construction machinery, and it is a widely used control valve. It plays an important role in improving the performance of construction machinery and has an important impact on the overall performance of construction machinery (working stability, reliability and system efficiency). For example, when the load of lifting mechanism, luffing mechanism and telescopic mechanism of hydraulic crane falls, if there is no balance valve, the mechanism will fall over speed, lose control and appear dangerous phenomenon under load. The greater the load, the greater the danger. Similarly, in the fully hydraulic walking system (open system), the danger of overspeed will also occur when going downhill, so it is also necessary to use the balance valve. In order to prevent danger and realize controllability, micro-motion, balance and safety of load drop, it is necessary to install a multifunctional balance valve in the drop circuit, which can not only limit the speed of load drop, but also realize fine adjustment and arbitrary control, so that it can stop at a certain height in space without any trace of downward movement (or drop).

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The balance valve also locks the positioning function, which can be maintained for a long time and has a good effect, but the price is more expensive.