Use the force Luke....

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iwire

iwire

Moderator
Staff member
Location
Massachusetts
hardworkingstiff said:
I believe it is. The valves are designed to block flow from a higher pressure to a lower pressure. The valve has no idea if the pressure differential is caused by introducing pressure on the inlet side or vacuum on the discharge side. Same same as far as the valve is concerned.:smile:
Click to expand...

I hear what your saying it makes lot of sense except that I believe they also have passages to atmospheric pressure and the spring(s) would be calibrated with an expectation of a pressure higher than atmospheric pressure not lower.

But I will gladly admit I am not sure. :smile:
 
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nakulak

Senior Member
how much in the way of organic volatiles are they venting into the atmosphere ? Since this looks like a garage operation, I'm guessing they don't have an epa permit to do what they are doing ? are they storing hazardous chemicals and hazardous waste on site as well ? I'm not passing judgement, but there are times when you need to run away from operations like this as fast as you can. Imagine the worst case scenario - "electrical fire" destoys their home and your neck is in the line of sight of their insurance companies lawyers because you built them a better machine.
 
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hardworkingstiff

Senior Member
Location
Wilmington, NC
iwire said:
I hear what your saying it makes lot of sense except that I believe they also have passages to atmospheric pressure and the spring(s) would be calibrated with an expectation of a pressure higher than atmospheric pressure not lower.

But I will gladly admit I am not sure. :smile:
Click to expand...

I'm pretty sure the valves I use do not vent to the atmosphere and work only on differential pressure between the inlet and outlet, but I also am not 100% sure (but pretty close to 99.99% sure). :smile:
 
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hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
nakulak said:
Imagine the worst case scenario - "electrical fire" destoys their home and your neck is in the line of sight of their insurance companies lawyers because you built them a better machine.
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The insurance companies lawyers will come after you even if you did not design the better machine, just because you didn't challenge them about posssible illegallities. Even if it was designed by an engineer!:mad:
 
ptonsparky

ptonsparky

Tom
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
The ins co would probably come after you if you changed the light switch in the bathroom and didn't know anything about what they did in the garage.

A PICO type controller and all the other stuff, sounds like a fun job to me. May not pay well but that wouldn't be the first one.
 
iwire

iwire

Moderator
Staff member
Location
Massachusetts
George Stolz said:
Very very slowly, from what I've seen. Probably no good for the application based on that alone.
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A typical Taco zone valve works by thermal expansion, they are designed to operate slowly and quietly. :smile:

As the air temperature at the
thermostat drops to the thermostat
setting, a normally open contact in
the thermostat closes. This completes
a circuit between the thermostat, the
zone valve transformer and the heat
motor of the zone valve power head
(terminals 1 and 2). 24 VAC now
flows through the wires wrapped
around the heater section of the
element inside the zone valve heat.

The expandable wax substance inside the element is heated.
It expands and pushes the piston inside the element down
against the valve stem. Since the valve is an upside down
globe valve, this downward push on its stem moves the
valve disc away from its seat, opening the valve.
Click to expand...

http://www.taco-hvac.com/uploads/FileLibrary/100-3.pdf
 
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hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
I know it's heriacy in an electrical forum, but what about a mechanical linkage to the exsisting valves or relocate valves to a better location, since there speed valves, turning them by hand is relatively quick.
 
W

wireguru

Senior Member
couple thoughts:

if you feel like tinkering, instead of spending $$$ on solenoid valves that will work with vacuum you can use a small pneumatic piston (and the associated bracketry) to actuate a ball valve, and a small cheap 1/4in pneumatic solenoid valve to operate the piston. These can be had cheap surplus, probably around $20 for the pair. -obviously only works if they have an air compressor.

Could the vacuum pump be re plumbed to locate the valves to a more convenient location? Seems like the problem isnt so much having to turn the valve, but to reach under there. I would also use a larger diameter pipe on the pump side of the valves, and possibly a reservoir.

Is it safe to use PVC with vacuum? I know it isnt safe with compressed air...
 
ultramegabob

ultramegabob

Senior Member
Location
Indiana
wireguru said:
couple thoughts:

if you feel like tinkering, instead of spending $$$ on solenoid valves that will work with vacuum you can use a small pneumatic piston (and the associated bracketry) to actuate a ball valve, and a small cheap 1/4in pneumatic solenoid valve to operate the piston. These can be had cheap surplus, probably around $20 for the pair. -obviously only works if they have an air compressor.

Could the vacuum pump be re plumbed to locate the valves to a more convenient location? Seems like the problem isnt so much having to turn the valve, but to reach under there. I would also use a larger diameter pipe on the pump side of the valves, and possibly a reservoir.

Is it safe to use PVC with vacuum? I know it isnt safe with compressed air...
Click to expand...

If I do anything with it, its going to be electrically controlled, I dont want to make the contraption any larger or complicated than necessary.

it has 30 gallon air tank reservoir, it is the reason for one of the solenoids...

pressure in a PVC pipe could become a bomb, I dont think vacuum in a PVC pipe is dangerous, the worst I think it would do is leak.
 
H

hardworkingstiff

Senior Member
Location
Wilmington, NC
After reading this thread and pondering.....

If it was my rig, I'd put a tee in the line and bush up to 2" and extend it until it stored enough vacuum for the process. I was thinking steel, but I believe PVC will be just fine. The best pressure differential you can get on Earth with a vacuum is less than 15 PSI and PVC is fine with that (besides it's trying to crush the PVC not explode it).

I would also put the valves closer to the mold so you could operate them without moving. Actually, this maybe should be the 1st move, then if the plastic still dries too soon, get a bigger source of vacuum by installing the tee and 2" pipe (or 3-4") extenstion (maybe a couple of feet long would do).
 
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wamegojim

Member
Location
NC
I am wondering why they are vacuum forming as opposed to injection molding. Wouldn't injection molding be quicker and easier? Not that it matters, a full suit in payment is a good idea! Although, cash works too.
 
ultramegabob

ultramegabob

Senior Member
Location
Indiana
wamegojim said:
I am wondering why they are vacuum forming as opposed to injection molding. Wouldn't injection molding be quicker and easier? Not that it matters, a full suit in payment is a good idea! Although, cash works too.
Click to expand...

the dies for injection molding a suit like that would cost 50,000 dollars or more, and the machine to install the dies is possibly in the hundreds of thousands to million dollar range.
 
W

wireguru

Senior Member
wamegojim said:
I am wondering why they are vacuum forming as opposed to injection molding. Wouldn't injection molding be quicker and easier? Not that it matters, a full suit in payment is a good idea! Although, cash works too.
Click to expand...

vacuum forming seems to be the method of choice for this type of stuff. Its how RC car bodies are made for example. The entry cost is low, and its not too difficult to make design changes.
 
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rt66electric

Senior Member
Location
Oklahoma
open the airlock-- space the troopers

open the airlock-- space the troopers

Try putting in a "ballast" tank. Think of a small air compressor that has a large tank with it. Install a check valve so that is a large resevoir of "vacum" to instantly suck.
 
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