A throttle valve is the most commonly used in various filed, even in our kitchen, for example. The working principle of home faucet is the simple throttle valve, but the difference is hydraulic oil as media and high pressure in industrial field in stead of water in home. The throttle valve is throttling the fluid flow, there are many different structures designed to throttle and it is better to choose the correct one for some certain working condition. –finotek.com

Hydraulic-Throttle-Valve-TypesThrottle valve is the one of the most simple and widely used as flow control valve, it is often equipped with pressure relief vale to compose a variety of throttle speed adjustment hydraulic circuit or system for fixed position pump oil supplying. According to different ways of manipulating the throttle valves, this valve can be divided into general manually adjustable throttle valve, cam -operated mechanical moving response throttle vale and other different throttling forms. The throttle valve is often installed with a one way check valve to become one way throttle check valve, there are threaded type and modular type (Including sandwich type) as per the way of connection.

General Working Principle of Throttle Valve:
The picture below is the axial orifice type throttle valve. The inlet port and outlet port P and T are drilled on the valve house, there is a axial triangle throttle orifice hole is created on the top of valve poppet (part no.: XNUMX), the fluid flows into P oil ports and flows out from T oil port through triangle throttle orifice hole to actuators or to oil tank. By regulating the adjustable knob to move the valve poppet position axially, which is be able to achieve fluid flow rate adjustment by adjusting cross-sectional area of throttle port.

                                                    XNUMX- Adjustable knob; XNUMX- Pushing rod; XNUMX- Valve Poppet; XNUMX- Spring

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There are other throttle port type, such as needle throttle valve, eccentric style throttle valve, poppet seal throttle valve and axial gap throttle valve.
Please refer the following details:
Needle Type Throttle Valve:
The needle type of throttle valve regulates the fluid flow rate by adjusting the size of throttle area through the axial movement of needle throttle poppet.
Simple structure, but longer throttle gap with small hydraulic force radius, therefore, the needle throttle valve is easily be blocked and influenced by hydraulic oil temperature. The needle type throttle valve is often used in general working condition.

Eccentric-type Throttle Valve:
There is an eccentric slot of three angle shape on the cross section of valve poppet, the eccentric throttle valve adjusts the fluid flow rate by turning the valve poppet to change the size of throttle area. 
The eccentric type throttle valve feature is most similar with needle throttle valve, it is easy to be manufactured, but the disadvantage is unbalanced radial force on the valve poppet and hardly to rotate the adjustment wheel, especially under higher pressure. The eccentric throttle valve is mostly used for the hydraulic system requires large flow rate and less stability condition.

Axial Triangular Slot Throttle Valve:
There are one or two triangular slots on the end of valve poppet, the fluid flow rate is able to be regulated by the poppet axial movement to adjust the area of triangular slot.
Large hydraulic force radius, better stability for small flow rate. When the triangular slots are manufactured symmetrically, the hydraulic radial force keeps balance in hydraulic system. The axial triangular slow throttle valve is often used for high pressure systems.

Groove throttle valve
The groove throttle valve is throttling the flow by a groove on the valve poppet. The oil fluid flows into internal holes through the groove, then flows out from the left holes. To turn the valve poppet is able to change the groove gap area and throttle the oil by the area dimension.
The throttle oil port can be produced to a thin edge shape, to achieve small and low stable flow, but the valve poppet is unbalance while operation by radial force, therefore, the groove throttle valve is usually used for low pressure hydraulic system.

Axial Gap Type Throttle valve
There is a slut on the valve sleeve, moving the valve sleeve in axial directional to change the gap area size in order to adjust the fluid flow rate.
The valve sleeve is available to produce as single thin blade or double thin blade structure, thence, the flow is not sensitive to temperature variation. The axial gap type throttle valve is used for high performance requirement working condition because its large hydraulic force radius at throttle ports and good stability under small flow rate.