What Is a Reversing Valve?

Directional valves are directional control valves with two or more flow patterns and two or more ports. It is a valve that realizes the communication, cut-off and reversal of hydraulic oil flow, as well as pressure unloading and sequential action control. The valve is controlled by the relative movement of the valve core and the valve body. There are two types of rotary valve and slide valve. According to the number of working positions where the valve core stays in the valve body, it is divided into two and three positions; according to the number of oil circuits connected to the valve body, it is divided into two-way, three-way, four-way, and six-way. There are manual, motorized, electric, hydraulic, electro-hydraulic and other types.

Six-way reversing valve is mainly composed of valve body, seal assembly,

(1) Motorized directional valve, also known as stroke valve.

(2) Electromagnetic directional valve. Electromagnetic directional valve is a directional control valve that uses electromagnetic attraction to manipulate the position of the spool.

(3) Electro-hydraulic directional valve. Electro-hydraulic directional valve is a composite valve composed of electromagnetic directional valve and hydraulic directional valve.

(4) Manual reversing valve. The manual reversing valve is a directional control valve that is operated by pushing the lever with the lever.

The action is accurate, the degree of automation is high, and the work is stable and reliable, but the drive and cooling system is required, and the structure is more complicated; the valve disc structure is simpler, and it is mostly used in production processes with small flow.

In petroleum, chemical, mining and metallurgy industries, the six-way directional valve is an important fluid reversing device. The valve is installed in thin oil

The most important items are solenoid valves, which mainly include the following items:

Working reliability

Refers to whether the electromagnet can be reliably reversed after being powered on, and whether it can be reliably reset after being powered off. The solenoid valve can only work normally within a certain flow and pressure range. The limit of this working range is called the commutation limit.

2. Pressure loss

Because the opening of the solenoid valve is small, a large pressure loss occurs when the liquid flows through the valve port.

3. Internal leakage

In different working positions, the leakage amount from the high pressure chamber to the low pressure chamber is the internal leakage amount under the specified working pressure. Excessive internal leakage will not only reduce the efficiency of the system and cause overheating, but also affect the normal operation of the actuator.

4. Commutation and reset time

The commutation time of AC solenoid valve is generally 0.03 ~ 0.05s, and the commutation impact is large; while the commutation time of DC solenoid valve is 0.1 ~ 0.3s, and the commutation impact is small. The reset time is usually slightly longer than the commutation time.

5. Commutation frequency

The commutation frequency is the number of commutations allowed by the valve per unit time. At present, the commutation frequency of a single solenoid solenoid valve is generally 60 times / min.

6. Service life

The service life of the solenoid valve depends mainly on the solenoid. The life of wet electromagnets is longer than that of dry ones, and the life of DC electromagnets is longer than that of AC.

7.Hydraulic clamping of spool valve

The hydraulic clamping phenomenon of the spool valve is not only found in the reversing valve, other hydraulic valves are also common, and it is more prominent in the high-pressure system. In particular, the longer the retention time of the spool valve, the greater the hydraulic clamping force. The thrust of the moving spool valve (such as the solenoid) cannot overcome the clamping resistance, so that the spool valve cannot be reset.

Some of the causes of hydraulic clamping are the difficulty of moving the spool due to dirt entering the gap, and some are stuck due to the expansion of the spool when the oil temperature rises, but the main reason is the geometrical error of the spool valve pair and Radial imbalance caused by concentricity changes. In order to reduce the radial imbalance force, the manufacturing precision of the valve core and the valve hole should be strictly controlled. When assembling, it should be made as tapered as possible. Reduce radial imbalance forces. ^[2]