gas bottle to air tank question

[VanMarco]

Hello, as I've gotten an old air compressor with an excellent motor but the tank (at least to me) has a lot of steel missing on the inside due to rusting, tank is from 2011 but it has never been drained, and I don't feel ok with using that tank, I wanted to to the gas bottle to air tank thing. I have just a couple of questions about it.

As some of you may know the tap thread is not a standard one, its below 1/2 but bigger than other sizes, so my plan will be to simply re-thread that brass valve with a 1/4 thread. a question about this, what kind of drill bit I have to use before I apply the 1/4 tap? I have a threader set and already did other threads but never a 1/4. In my threader set I got the drill bit for M12, which is 10.5mm, is that any good for the purpose? alternatively I have an 11mm one.

As illustrated on the images I plan to put the bottle upside down, with a tee installed so that I can drain moisture easily.
I wanted to weld 3 brackets on the handle so that I can screw this on the floor, and I would like to weld a sheet on the top on which i could mount the motor. May I weld these items on the specified part without ruining the pressure vessel? I think it won't be a problem because they are not the vessel itself but I'd like to ask anyway.

The pink line will be a copper pipe going from the compressor motor to the bottle, as ideally I would like to simply have a line going there and then have the pressure switch, manometers on the top, but I am not sure if this will give false readings or it can't be done as this items would need to be installed directly on the tank

Thank you for any reply

 

[rtbcomp]

Welcome to the forum.

Google "1/4 BSP Tapping drill sizes", that should turn up the correct drill size.

Remove the valve before drilling, it may have a safety valve with a steel ball and spring which could cause sparks when the drill hits it.

You will need to put a non-return valve (NRV) in the line between the pump and the tank.

You can tee-off after the NRV to feed the pressure switch, pressure gauge and safety valve. There will be no airflow through this pipe so there will be no pressure drop.

You will also need to tee off before the NRV to the unloader valve in the pressure switch.

I did a similar exercise to this, but I drilled the brass valve to 15mm clearance and soldered a copper pipe into the hole and used compression or capillary fittings to connect to the rest of the system

 

[normspanners]

There is a post on here somewhere for this exact scenario with all the sizes req but what I did was to put an upright tube high up inside the tank but also inside the tee fitting, finishing high up to extract the dry air through and straight out of the tee fittings the problem with how you have designed it, is it will constantly be re introducing the air to the drained condensate/ water.

 

[knighty]

you can get adapters to go on gas bottles (adapters to a different thread)

I know a fridge engineer who uses one so he can recover refrigeration gas into an lpg bottle if there's too much for his normal recovery cylinders

might be easier that way ?

 

[rtbcomp]

I think he's got a butane LPG bottle with snap-fit connector. You can get high pressure hoses with screw connectors to fit the red propane bottles from camping shops. I've used one of these in the past.

 

[WorkshopChris]

I think he's got a butane LPG bottle with snap-fit connector.

If so especially at this time of year you would need to be very sure you had a fully empty cylinder.
Or you could end up with running tools on compressed butane. If this is to replace the factory tank will also need to fit a safety valve.

I don't feel ok with using that tank, I wanted to to the gas bottle to air tank thing.

 

[rtbcomp]

If so especially at this time of year you would need to be very sure you had a fully empty cylinder.
Or you could end up with running tools on compressed butane. If this is to replace the factory tank will also need to fit a safety valve.

True, I did mention the safety valve in post #2

 

[rtbcomp]

^^ Safety valve & pressure gauge screw into the pressure switch, if you get a 3 or 4 port one.

 

[VanMarco]

Thanks for all the answers oh i failed to say what bottle Im going to use, given the image gave a nice idea but I was wrong lol. It's a 47Kg bottle. And yeah of course I'll purge the gas. I've already done this with smaller butane one, removed the valve, filled with water and left standing there for a few days (as I had other things to do) then I just drained the water and cut weld etc. and thanks for reminding me that the pressure switch also require the other tiny pipe to be connected. Also why the original compressor tank did not have a non-return valve?

Normspanner yeah I gave it a thought too, the fitting sketch is just a sketch. do you know the link to the post you are talking about?

 

[julianf]

Im pretty sure that the thread in 47 kg tanks is just 3/4 bsp.

I don't mean the brass, but the steel.

 

[Burdekin]

I think the top is 3/4 BSPT, think I tapped it to 3/4 BSP. Tigged a 1/2"BSP steel bush to the side (inlet) and bottom (drain) and the top is the outlet. http://www.mig-welding.co.uk/forum/threads/new-compressed-hard-airline-design.60065/page-2

 

[VanMarco]

Uhm, as I have found two non return valve, that are 3/8 and another fact is that my motor output pipe is also 3/8. the propane bottle valve (s, as I have also one from a butane bottle and are the same thread as the big one) are about 17/18mm. at one point for about 10mm or so are like 20mm. Only thing is to do a 3/8 taper I would need to drill a 15.2mm hole resulting in having just 2-3mm of metal around once threaded, do you think it can be done? I will post pictures later

Thanks

 

[Wedg1e]

I could foresee some horrific vibration if you bolt it to the floor...