A motorized ball valve to shutoff water to my house

[Stwood_]

..

[jteneyck]

Which one(s) do you think does not?  If "pressure is pressure" the results of the balloon experiment would be the same.

Another difference - gas is compressible, water is essentially not compressible.  As an example, water in the cylinder of an IC engine will usually destroy it, gas such as gasoline vapor does not.

All of them. 

You are completely missing the point about pressure.  Gasses and liquids are both fluids.  Gasses are compressible, liquids are not.  Pressure relief valves don't care, they open when the pressure of the fluid reaches the preset value.  If you can't understand that, or just refuse to believe it, then I suggest you call up Watts or one of the other pressure relief valve manufactures and ask one of their technical experts. 

Your balloon experiment proves the point; you just don't see it.  The balloon with water doesn't explode because water is not compressible.  The balloon with air will explode if the pressure is high enough precisely because the air inside is compressible AND the balloon is highly elastic.  But a water tank is not a balloon.  Under normal operating pressures it does not stretch (at least not a measurable amount).  So when you poke a hole in it (the T/P relief opening) it won't explode even when filled only with air; the air just rushes out.   It only explodes when the T/P fails to function (or was removed and the hole plugged) such that the pressure reaches some extreme value that exceeds the rupture strength of the tank.  The exact same scenario applies to air compressor tanks and any other pressure vessel.  

John

[geek2me]

All of them.

Sorry, not correct.

Gasses and liquids are both fluids.  Gasses are compressible, liquids are not.

Incorrect.  Gasses and liquids can be compressible, or not.

Pressure relief valves don't care, they open when the pressure of the fluid reaches the preset value.... I suggest you call up Watts or one of the other pressure relief valve manufactures and ask one of their technical experts. 

Have you tried calling them?  They may be better able to clear up your misunderstandings.  Or you could read their data sheets where they say the valves are ONLY for liquids.

The balloon with water doesn't explode because water is not compressible.  The balloon with air will explode if the pressure is high enough precisely because the air inside is compressible AND the balloon is highly elastic.  But a water tank is not a balloon.

Sort of, but not quite.  I used the balloon example for simplicity and most people will have access to balloons.  Most people don't have access to equipment to pressure test steel vessels like we do.  The reason vessels are tested with water rather than air is that they rupture instead of explode.  We know the pressure at the point of rupture and can then calculate the gas pressure that would cause a rupture.

You may find it interesting to read the ASME test procedures for steel tanks, that may help clear up your misunderstandings.

Regardless, you don't seem to value the knowledge of this expert, so I'm not sure there is much value in further discussion.

[jteneyck]

Sorry, not correct.


Incorrect.  Gasses and liquids can be compressible, or not.


Have you tried calling them?  They may be better able to clear up your misunderstandings.  Or you could read their data sheets where they say the valves are ONLY for liquids.


Sort of, but not quite.  I used the balloon example for simplicity and most people will have access to balloons.  Most people don't have access to equipment to pressure test steel vessels like we do.  The reason vessels are tested with water rather than air is that they rupture instead of explode.  We know the pressure at the point of rupture and can then calculate the gas pressure that would cause a rupture.

You may find it interesting to read the ASME test procedures for steel tanks, that may help clear up your misunderstandings.

Regardless, you don't seem to value the knowledge of this expert, so I'm not sure there is much value in further discussion.

I always value the expertise of knowledgeable people.  What are your credentials and experience from which you base your claim of being an expert?  

Of course pressure vessels are tested with water, they are taking the tank to rupture.  Please explain why you would have to calculate the gas pressure that would cause a rupture after measuring the rupture pressure using water? 

First you said gasses are compressible and liquids are not, now you say they both can be, or not.  Please explain.

I suggested you call Watts; I'm clear on how P/T relief valves work.  Show me a data sheet that says a P/T relief valve on a boiler or water heater will not relieve an over pressure condition if the tank is filled with air? 

John

[crokett™]

Unless I misunderstand you want a way to shut off the water while you're on vacation or whatever. I'm still trying to figure out why you need a 150.00 motorized valve when a 10.00 quarter turn valve will do the same thing? Do you eventually plan to make this remote control or wire it to the alarm system or something?

[Stwood_]

Unless I misunderstand you want a way to shut off the water while you're  on vacation or whatever.  I'm still trying to figure out why you need a 150.00 motorized valve when a 10.00 quarter turn valve will do the same thing?   Do you eventually plan to make this remote control or wire it to the alarm system or something?

He's lazy. Wants to hit the switch by the door for the water valve as he is exiting the house.

[jteneyck]

Unless I misunderstand you want a way to shut off the water while you're  on vacation or whatever.  I'm still trying to figure out why you need a 150.00 motorized valve when a 10.00 quarter turn valve will do the same thing?   Do you eventually plan to make this remote control or wire it to the alarm system or something?

He's lazy. Wants to hit the switch by the door for the water valve as he is exiting the house.

Yes, I want to be able to easily turn off the water whenever the house is not occupied, whether on vacation or just away from home for an hour or two.  The first post shows the switch that activates the valve right next to the security system panel.  Simple - so people will use it.  

John

[blackhat]

I'll make it easy for you.  Show me one picture of a water heater that ruptured while fitted with a properly functioning T&P valve.  Just one.

[Stwood_]

Yes, I want to be able to easily turn off the water whenever the house is not occupied, whether on vacation or just away from home for an hour or two.  The first post shows the switch that activates the valve right next to the security system panel.  Simple - so people will use it.  

John

[woodhead]

John, I am sticking with my original comment that water to a running boiler should never be shut off. Chances are that nothing will ever happen, but it could be ruined (not so much blowing up).



Al