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"Normally Open" or "Normally Closed" are classifications that refer to actuated (not manually operated) valves. For an actuated valve, the "normal" state refers to its position when the actuator is not energized.
Therefore a normally open valve is one that is open until the actuator is energized to close it; if power to the actuator fails, the valve opens or "fails open".
Likewise with a normally closed valve if power to the actuator fails, the valve closes or "fails closed".
The "normal" state of an actuated valve must not be confused with the "usual" position of the valve during routine operation of the system. A normally closed valve may be open continuously over a long period of time while a process is running, but it is still a normally closed valve. It just happens that this normally closed valve is usually open.
For an actuated valve to return to its "normal" position, there must be some force, often a spring, that moves the valve from its actuated state back to its normal state. If a valve is actuated to open and then actuated to close, it will "fail" in whichever position it is in when the activator is de-energized. This type of a valve is not considered "fail safe".
A normally closed valve might be used in an application such as the loading of gasoline transport trucks where in the event of a power or automation system failure, you would want to stop flow.
A normally open valve might be used in a situation where you want flow to continue in the event of a power or automation system failure. This might be the case for the cooling water system for a nuclear reactor or for an actuated valve on the water piping to the fire protection system.
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Does it put pressure on the pipe to turn off toilet valve and not the main water for 2 days?
It does not increase the pressure it remains the same as if the valve was open.
What is the difference between a Single acting and double acting valve?
Normally a control valve is referred to by its fail position. This means "what position will the valve move to should the supply air or control signal to the valve falls away". This is important to safe guard the process at various places, so some valves will be fail open and some fail close. In order to have a valve as fail open or fail close, the valve actuator has to be spring loaded. So by having the spring on top or bottom of the actuator piston will we determine if it will be an FO or an FC valve. This kind of valve is also called single acting valve since it will only have one output from its positioner to either the top or bottom of the actuator. The positioner on the valve is also setup as a single acting positioner since it will only give a single action to the actuator, the reverse action will be done by the spring. The problem with this setup is that it is possible that the process might be so strong or the pressure so high (during a blow down or ESD shutdown in the plant) that the spring might in certain instances be too weak to push the valve into the fail position quick enough, due to the back pressure from the process, and can cause damage to the plant or even an explosion. To ensure that the valve will go to the fail position, we install a double action positioner with two outputs. One goes to the top of the actuator and one to the bottom. This is also very helpful in having very accurate and stable control on a high flow line since the pressure from the positioner does the actual control unlike spring controlling one way and positioner controlling the other way as is in the single acting control valves. It is also solving the problem that the valve will now be forced into the fail position by the spring as well as the positioner supply pressure during an emergency. In shutdown valves (open/close ESDVs) the same is true and sometimes at critical and high pressure points we use hydraulics instead of pneumatic as the double acting agent to make sure the valve will close during the emergency. So to summarize the double action in ESD and control valve, it suffices to say that this double action is there just to make sure that the valve will do what it was designed for. Call it an extra fail safe if you want. It might not be needed in theory since a single acting valve should do the trick just as well, but in practice you are at times very glad that you did it especially if you look at the kind of pressures the valves are working on. With those kind of flows and pressures you don't want to leave anything to chance.
When the intake and exhaust valves are both open at the same time that length of time is called?
Valve overlap.
What does the term valve overlap mean?
Valve timing overlap is the time when both exhaust and intake valves are open most engines with catalytic converters require valve overlap in order to send a small amount of raw fuel/ air mix to the converter's. An "open cam" has valve overlap a "closed" cam does not
Why can't the AV and sl valves be open at same time?
The blood in the heart moved from one chamber to another chamber. If the AV ( artrio-ventricular valve) and SL ( semilunar valve) open at the same time, the blood will not be able to circulate and can flow backward. Thus the valves are there to stop the back-flow of blood and keep the circulation going.
How do you bleed the injectors on a Massey Ferguson tractor?
1. undo the bleed valve on top of the sediment bowl, and pump the primer 10 times then close the valve. 2. open the bleed valve on the 1rst fuel filter, (top valve) repeat pumping. close valve. do the same to the bottom valve on the 1rst filter. 3. do the same to the secondary filter. 4. open the valve on the fuel pump(under the injector lines) pump and close it 5. do the same to the bottom valve. 6. if you have four injector fuel lines(four cylinder) undo two lines at a time and turn the key until straight diesel comes out, then reattach line. repeat with other two. then start the tractor. if it doesn't work, you may have more air in the lines or another problem.
What valve controls the flow of blood from the ventricles to the bodys main artery?
lol i had the same worksheet. the answer is the aortic valve. i just put down aortic
Is a PCV valve the same as an egr valve?
No.No.
Is presta the same nozzle as a schrader?
Prestas and Schrader needs different nozzles. Schrader needs a bigger nozzle with a pin to open the valve in the middle.
Is safety valve and pressure valve mean the same?
yes
Is a check valve the same as a non return valve?
yes
Have a ford f450 and half the injector quit at the same time?
Assuming this is a diesel engine, the electrical connection for the injector harness where the harness passes through under each valve cover is known to fail. The connection is part of the valve cover gasket and is easily replaceable. When you remove the valve cover from the bank that is giving you trouble, you will see the problem at the electrical connection.
