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"Throttle" and "relief" features and requirements
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| Release time：2014.04.23 News source：Yuhuan TRV Throttle Body Co.,ltd,Throttle Body,Throttle Valve Browsing number： |
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According to the Throttle Body Kero understand, throttle and throttle is a simple one-way flow control valve, in quantitative pump hydraulic system with throttle valves and relief valves, throttle system can be composed of three kinds, That throttle system into the oil, the oil return throttle system and bypass the throttle system. Negative feedback does not throttle the flow can not be compensated by changing the speed of the load caused by instability, little change is generally only used for load or speed stability is not critical.
Performance requirements of the throttle are: flow adjustment range, smooth flow of a pressure change; leak · small amount, if any leaked oil spill port, and also a small amount of leakage; small · adjust torque, quick action. Throttle (throttle valve) outline the structure and there is no difference between the shut-off valve, but the shape of their opening and closing parts are different. Throttle opening and closing parts are mostly tapered streamlined, change the channel through which the cross-sectional area and to adjust the flow rate and pressure. Throttle valve for the pressure drop under conditions of great pressure to reduce media use.
Medium between the throttle valve and seat a large flow rate, to cause damage to these parts of the surface quickly - the so-called cavitation. To minimize the effects of cavitation, valve cavitation-resistant materials (alloy steel) and made into the top corner of 140 to 180 streamlined cone, which also enables the valve to have a larger opening height, is generally not recommended throttling at a small gap.
Throttle has the following characteristics:
1, the structure is simple, easy to manufacture and maintenance, and low cost.
2, regulation accuracy is not high, can not be adjusted to use.
3, the sealing surface erosion can not be cut off media use.
4, good sealing poor.
Press the throttle channel can be divided into two kinds of straight and angle; according to the shape of the opening and closing pieces, a needle-shaped groove shape and window-shaped three. Installation and maintenance of the throttle should note the following: The valve is often necessary to operate, and therefore should be easy to install in terms of the position they operate on. Note that when you install the media direction consistent with the direction of the body as the arrow. Orifice blockage causes:
1, fluid mechanical impurities or gelatinous precipitates due to oxidation, asphalt, carbon residue and other contaminants accumulate in the gap at the throttle.
2, the polarization due to aging or the oil after being squeezed charged molecules, a potential difference exists on the metal surface of the throttle gap, the polarized molecules are adsorbed to the surface of the gap to form a solid boundary layer adsorption, the adsorption layer thickness typically 5 to 8 microns, thus affecting the size of the throttle gap. More accumulation, adsorbate grow to a certain thickness, the flow will be washed away, and subsequently re-attached to the valve port. This cycle, the formation of a pulsating flow.
3, the larger the differential pressure valve, the valve port due to high temperature, the degree of enhancement of liquid by squeezing the metal friction surface is more susceptible to the formation of a potential difference, and therefore prone to clogging when large pressure difference.
Mitigation measures orifice blockage:
1, select the hydraulic radius of thin bladed orifice.
2, precision oil filter and change them regularly.
3, appropriate to reduce the pressure before and after the orifice.
4, using the potential difference between the metal material is small, the selection of a good oxidation stability of oil, reducing the surface roughness of the orifice.
According to the Throttle Body about Kero throttle applications because not only depend on the flow rate restrictor orifice size of the area, but also the pressure difference before and after the orifice is related to the stiffness of the valve is small, it is only adapted to perform components and load changes very little speed stability is not critical. For large actuator load changes and high-speed stability requirements throttle system must compensate for the throttle pressure to maintain constant pressure around the throttle to achieve stable flow
Relief: A hydraulic pressure control valve. In hydraulic equipment mainly from the constant pressure overflow effect and safety protection. Constant pressure relief function: quantitative pump throttle system, is a quantitative pump provides a constant flow. When the system pressure increases, flow demand will decrease. At this time the relief valve opens, so that excess flow back to the tank overflow, inlet pressure relief valve to ensure that the pump outlet pressure constant (often with the pressure fluctuations valve port open).
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