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Actuator Frequently Asked Questions
If you have only 40 psi and you would like to apply a VP-VL spring return actuator, the most effective spring combination is three springs on each piston. This designation is SR3. The easiest approach is to take standard 60 psi ( SR 4/5 ) unit from stock and remove one spring from the piston that has four springs and then remove two springs from the piston that has five springs. Having done this you will have three springs remaining on each piston ( SR3 ). The torque output for SR3 actuators running at 40 psi is in the table below.
If you would like further assistance in actuator sizing, please contact Summit Controls.
What are the power requirements of Rexa Electraulic actuators?
Ball Valve Frequently Asked Questions (FAQ)
A full bore (or full port) valve is one where the hole in the ball is equal in diameter to the hole in the pipe. In other words, if you were to look down a piece of pipe which also contained the valve, you would not notice any constriction at the location of the valve.
A reduced bore ( also called a standard bore or port) valve is one where the hole through the ball is smaller than the hole in the pipe. In some valves such as the Jamesbury 5000 series, there is a gradual narrowing so that the valve almost looks like a vena contracta. In other valves, such as the reduced bore Jamesbury 4000 series, the reduction is simply a shoulder. Often, the reduction in diameter is to the next standard size. For example, a 2" (nominal size) reduced bore valve would have a 1.5" bore in the ball. A 1.5" (nominal size) reduced bore valve would have a 1.25" bore in the ball and so on. This comes from a rule of thumb which actually coined the term "standard bore" as much as the desire for modular design to allow the same ball to be used in one size of full bore valve and another of a standard bore. Long time ago, the engineers noticed that to get good control, very often the solution was to use a full bore valve of one size smaller than the pipe you were using. Now, this arrangement required reducers on either end of the valve. Someone then came up with the idea of integrating the reducers in to the valve and the standard bore valve was born.
Engineers as well as pipe designers feel that because of the restriction in a reduced bore ball valve, that a significant amount of pressure loss happens. Actually, it is less than one might think. We will use Neles Automation's valve sizing program Nelprof© to demonstrate how little difference there actually is. The conditions we will use are as follows:
We will adjust the differential pressure until the valve is showing as close to 100% open as possible. Here is the sizing of the full bore valve:
Using the same process data, we will size a reduced bore valve.
The difference is less than a tenth of a psi. Granted that the reduced bore valve has a pressure loss that is about an order of magnitude greater, either case becomes insignificant when compared to the pump output. For the savings available from using the reduced bore valves, it should be considered.
Jamesbury's lip seal deisgn uses a completely different sealing principle than a typical "Jam" seat. A "jam" seat is simply jammed between the body and the ball and uses the compression of assembly to provide the forces necessary to create a seal. This results in high operating torques and thermal expansion problems. With Jamesbury's Lip seal design, the ball is cradled between the two seats but the seal is created by elastic (spring-like) movement of the seat's lip rather than compression of the complete seat. The movement of the lip is limited by the heel. Once the ball has moved a pre-determined amount against the lip due to pressure or thermal expansion, the ball then contacts the heel and significantly reduces any subsequent movement. The benefits of this design include cavity relief without a relief hole or upstream pressure. Also, it reduces the operating torque requirements for the valve. Finally, the design copes much better with thermal expansion than a typical "jam" seat. How to Size a Mag Meter
From the table, obtain the velocity at 40 ft/s for 3 " meter (955.6). v = 7.32 ft/s
Footnotes: 2 Full scale analog output may be set between 1 and 40 ft/s. All Converters have the following features:
AS-i Link Frequently Asked Questions
It is a field proven standard for discrete (On/Off) actuators and
sensors and stands for Actuator Sensor Interface. Although more complex
netwoeks may
be used in this role, AS-i is optimally suited for this level.
Because of its proven
reliability, wide range of bus interfaces and huge installed
base, it is well accepted throughout the world at this level.
Currently, Stone-L offers the following connectivity options:
In addtion, an ISA card is available for your PC to connect as the master for a group of devices. What field wiring components are available to help implement a fieldbus networking system?
Vortex Shedding Flowmeter Frquently Asked Questions
The vortex shedding meter is best used for gas and steam, as well as liquids of low viscosity that do not contain significant amounts of solids. In fact, steam is the largest single application for vortex meters. The vortex meter can be used in most applications where dP/orifice meters have been used.
Sizes range from 3/4" to 12". They are available in flanged and wafer styles.
The basic concept is that there is a flow obstruction, or shedder, that causes the flow to separate and then shed swirls or vortexes of flow. The rate at which the swirls are shed is directly proportional to the amount of flow passing the shedder. However, one should note that at very low densities flowing slowly there is very little energy in each vortex swirl. At some point in the flow range the energy is too low for the sensor to detect and the meter goes to zero. For liquids, the lower limit of the operating range is determined by the Reynolds number of the flow. The Reynolds number (Re) is viscosity dependant and as the viscosity goes up, the Re goes down. Vortex meters are linear in output to an Re of 20,000. Below that, the vortex shedding process starts becoming less regular until is becomes so irregular that it is unreliable. For optimum performance in a vortex meter, the viscosity of the liquid should be water-like. As the flow strikes the shedder located in the middle of the flow stream, the flow must separate to go around the shedder. As it does, it rolls up in swirls or vortexes on alternating sides of the shedder. The vortex swirl hangs on the shedder growing larger until its volume gets too large at which point it separates or sheds from the shedder. At the point of shedding there is a momentary low pressure, high velocity on one side and a momentary high pressure, low velocity on the other side. The next vortex swirl then forms on the opposite side and repeats the process all over again. The vortex swirls are always shed on opposidte sides of the shedder, 80 degrees out of phase with each other. Each vortex swirl grows to be the same size so you can determine a K-factor to express the ratio of swirls to volumetric flow regardless of what the flowing material is. Using this K-factor and counting the number of pulses, you can determine total flow or volumetric flowrate and the meter then outputs this information on a 4-20 mA signal. |
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1-48 Queen Street East Cambridge, Ontario Canada N3C 2A8 Phone: (519) 651 2730 Fax: (519) 651 2722 Email: sales@summitcontrols.com © 2003 Summit Controls Ltd. |
