Claire Christian Valves April 10th, 2019 - 14:32:46
A four-stroke engine is said to have a very laborious life. Manufacturers are currently downsizing the production of engines. Along with the downsizing of engines comes the boosting, which is basically means turbo-charging. However, when manufacturers try to boost engines, there is an increased pressure and temperature inside the combustion chamber. The exhaust gas temperatures also become higher. Normally, the exhaust valves already have to deal with higher temperatures compared to the inlet valve in an engine that is naturally-aspirated, and these valves could increase in temperature even further.
Customers wanting the best in Needle Valves need look no further than Swagelok to meet all their needs. Swagelok Needle Valves are used in flow metering applications, where a constant, calibrated flow must be maintained. A Needle Valve has a long tapered point at the end of the valve stem that is lowered through the seat to restrict or block flow, as required, and a needle-shaped plunger on the end of the screw which exactly fits the point. Fluid flowing through the valve turns at 90 degrees, and passes through the orifice that is the seat for a rod with a cone shaped tip. The finely threaded stem, and large seat area allow for the precise calibration of resistance to flow. As the plunger is retracted, flow between is possible - until the plunger is completely retracted, fluid flow is impeded.
In order to achieve the best performance of valves, manufactures must take many important design factors into consideration. These factors include actuator or positioner design, valve response time, valve type and sizing, and dead band.
As sleeved valves, then the passport MTBF of 1,300 cycles, their actual performance is enough for 20-40 cycles, after which the sediment accumulated on the sealing saddle, do not allow completely block the flow by turning the valve itself in another "architectural extravagances." Moreover, the coefficient of local resistance they simply record - from 16 to 20. That is, at a flow rate of 1 m / sec, passing through the valve, the pressure of the liquid is reduced by 1 m of water.
Valve response time is another important factor for us to consider. For optimum control of many processes, it is important that the valve reach a specific position quickly. A quick response to small signal changes is one of the most important factors in providing optimum process control. Valve response time includes both the valve assembly dead time, which is a static time, and the dynamic time of the valve assembly. It is important to keep the dead time as small as possible. Dead band, whether it comes from friction in the valve body and actuator or from the positioner, can significantly affect the dead time of the valve assembly.
Among all the above mentioned considerations, it is rather necessary to talk about the actuator and positioner design. These two must be considered together. The combination of them affects the static performance (dead band), as well as the dynamic response of the control valve assembly and the overall air consumption of the valve instrumentation.