Alma Kelley Valves April 11th, 2019 - 12:00:05
There are many types of ball valves that are extensively used in various industries depending upon their designs, sizes and pressure handling capacities. Full port, reduced port, cavity filler, V port, trunnion ball valves and multiport valves are the common ones.
There is a slight flaw with valves though. The valve combination of 2-3 will be slightly sharp, the 1-3 combination will always be quite sharp, and the 1-2-3 combination will always be very, very sharp. Lets explore why this phenomenon happens.
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.
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.
A valve is a device which controls the flow rate, pressure or the direction. The controlled fluid can be the liquid, gas, the mixture of gas and liquid or the mixture of solid and liquid. The valve usually is composed of body, seat, bonnet, parts for opening or closing, actuating device, sealing element and so on. The controlling function of the valve depends on the actuating device or the movement of the fluid which drives the sliding, rotating or turning of the parts for opening or closing to change the area of the flow passage.
The formula for the theoretical length of tubing, TL, needed to lower a set number of half steps, x, for an instrument of length, L, is TL = L (16/15) ^ x. Example: 100" instrument lowering 3 half steps: TL = 100(16/15)^3. TL = 21.36.