Throttle is a valve that controls the flow of a fluid by changing a throttle section or a throttle length. The throttle and the check valve are connected in parallel to form a one-way throttle valve. The throttle and the one-way throttle valve are simple flow control valves. In the hydraulic system of the fixed pump, the throttle and the relief valve cooperate to form three throttling speed control systems, that is, the throttle speed regulation System, return oil throttle control system and bypass throttle speed control system. The throttle has no negative flow feedback function and cannot compensate for the instability caused by the load change. It is generally only used in applications where the load does not change much or the speed stability is not high.
Performance requirements
The performance requirements for the throttle are:
·The flow adjustment range is large, and the flow-pressure difference changes smoothly.
·The amount of internal leakage is small. If there is an external leakage port, the amount of external leakage should be small.
·The adjustment torque is small and the action is sensitive.
The shape of the throttle is no different from that of the shut-off valve, except that the shape of the opening and closing member is different. The opening and closing members of the throttle valve are mostly conical and streamlined, and the flow rate and pressure are adjusted by changing the cross-sectional area of the passage. The throttle valve is used to reduce the pressure of the medium in the event of a large pressure drop.
The flow rate of the medium between the throttle flap and the valve seat is so great that the surface of these parts is quickly damaged, so-called cavitation. In order to minimize the influence of cavitation, the valve disc is made of cavitation resistant material (made of alloy steel) and made into a streamlined cone with a tip angle of 140-180. This also enables the valve flap to have a large opening height, which is generally not recommended. Throttle under a small gap.
Characteristics
1. The structure is simple, easy to manufacture and maintain, and the cost is low.
2. The adjustment accuracy is not high and cannot be used for adjustment.
3. The sealing surface is easy to be eroded and cannot be used as a cutting medium.
4. Poor sealing.
Classification
The throttle can be divided into straight-through type and angle type according to the channel mode; according to the shape of the opening and closing member, there are three types of needle shape, groove shape and window shape.
Adjustable throttle: The valve needle and spool are made of hard alloy. The product is designed according to API6A standard and has wear resistance and erosion resistance. Mainly used in wellhead oil (gas) tree equipment.
Sleeve type throttle: The valve core adopts low noise balance structure, which is light and easy to open. The product is designed according to API6A standard. The surface of the valve core is covered with tungsten carbide. It is suitable for flashing, high pressure difference, high pressure, cavitation and other harsh conditions. Occasionally, the service life is long and the flow adjustment accuracy is greatly improved. Suitable for oil, natural gas, chemical, oil refining, hydropower and other industries.
