Air line between 2 buildings

Pattnmaker · Jul 29, 2015

I have recently bought the building next door and have moved the patternmaking part of my business to the new building. I am running the new shop on a cheap 5 hp compressor but when I move the CNC router over I need to hook my 10hp Champion over so i don't burn the smaller compressor out, it will run it ok but long term the steady use will kill it.

I need most of the air capacity in the wood shop but occasionally need high volumes of air in the metal shop for a day or 2. Often I won't need much or any air in the metal shop. I am planning on connecting the air systems in the 2 shops which are about 16' apart but am concerned with the airline between the shops freezing in the winter. I don't want to get into burying the pipe below the frost line. Am I doomed to a frozen air line if I run the air line between the buildings about 10ft high? Would insulating the pipe help? I guess the other option would be to get another cheap compressor for the metal shop and only open the connecting pipe when I need lots of air in the metal shop.

Mcgyver · Jul 29, 2015

I think it would freeze....what about those heating strips you snake around the eves so you doesn't ice build up? attach (handmans secret weapon) on along the line and I'd give you a fighting chance of it being ok. Farm supply place might have other/better pipe warming products

Larry Dickman · Jul 29, 2015

put a pipe heater on it.

Jay Fleming · Jul 29, 2015

Run a 2" PVC pipe between the two buildings overhead, supported somehow. Pull a length of 3/4" polyethylene air pipe with foam rubber pipe insulation around it through the 2" PVC. Inside the insulation also run a length of heat trace with a thermostat inside the building. Should prevent any freeze ups. You could also just slope the pipe about a foot vertically over the length between the two buildings and have an auto-blowoff valve inside the building on the low side.

The real Leigh · Jul 29, 2015

Your air system should have a moisture-removal feature even if only one a single building.

Put one in each building, with a significant slope to the air pipe, and use a large diameter (like 1" or more) pipe outside between the buildings.

Any residual moisture will freeze, but you won't care because there's so little of it.

A pipe heating wrap with an insulated over-wrap is not a bad idea, as others have suggested.

Also, I suggest putting a large reservoir tank in each building to reduce peak loading and pressure drop through the interconnecting pipe.

- Leigh

Scruffy887 · Jul 29, 2015

No matter what you need an air drier. Your CNC router will thank you for it.

surplusjohn · Jul 29, 2015

you are not going to have much moisture in the air to start with, I would have an exterior inlet vent for the compressor so you are drawing outside air in.

adama · Jul 29, 2015

IMHO if you slope it down in the direction of flow i don't think you will have a issue, so long as it naturally does not puddle i can't see it freezing up! IE no big U type sags, nice straight inclined run in hard pipe!

The real Leigh · Jul 29, 2015

adama said:
IMHO if you slope it down in the direction of flow i don't think you will have a issue...

In fact, quite the opposite is true.

You want the low end at the source (compressor), with a moisture drop to floor level.

That prevents moisture from going any farther into the system than absolutely necessary.

- Leigh

Tonytn36 · Jul 29, 2015

adama said:
IMHO if you slope it down in the direction of flow i don't think you will have a issue, so long as it naturally does not puddle i can't see it freezing up! IE no big U type sags, nice straight inclined run in hard pipe!

1/4" / ft slope and auto drain on other building side with a tank. I also suggest a larger pipe between the buildings.

Modelman · Jul 29, 2015

Ditto. Run it overhead in iron pipe, pitched in the direction of the air flow. Put a drip leg and water trap at each end, at the source to collect any water moving along the pipe before it goes outside; in the next building because the cold temp. will likely condense some more water out of it, Use water traps with automatic drains, so you don't forget.

Worse that can happen is you carry enough water along that it condenses and coats the inside of the pipe with ice. Iron pipe can be heated with a torch to get back running; add a heat trace in side insulation to resolve the problem in the future.

Connect the outdoor section with unions at each end so it's easy to replace when someone drives a truck into it.

You can also do this with the pipe buried, but the drains are a problem unless you can go from basement to basement.

Dennis

On edit:

For a quicky, just run 1-1/4 air hose on the ground between the buildings (construction hose). Chances are it's too big to freeze solid; can always be brought inside if it does.

EPAIII · Jul 29, 2015

Slope? Absolutely yes! But not down in the direction of the flow: definitely UP to drain any moisture back to the source. You do not want the moisture to get into the devices using the air. Put a collection jar at the beginning of the run.

And use heat tape on the pipe to keep it from freezing in the winter. And some insulation over that. I was able to keep water hose to my trailer working in -20 degree temps in Iowa with heat tape and a double layer of foam insulation, well wrapped with duct tape.

adama said:
IMHO if you slope it down in the direction of flow i don't think you will have a issue, so long as it naturally does not puddle i can't see it freezing up! IE no big U type sags, nice straight inclined run in hard pipe!

The real Leigh · Jul 29, 2015

At the risk of being redundant and repeating myself over and over...

You ALWAYS slope the distribution system with the lowest point at the source (compressor end).

Water is a contaminant in a compressed-air system.

Why would you slope the piping in a direction that spreads a contaminant throughout the system?

- Leigh

Joe Rogers · Jul 29, 2015

No pcv for air lines please. Not rated for it and when cold or impacted could fracture and spread shrapnel over a large area. Use iron or steel pipe or even thick wall copper.
Joe

moonlight machine · Jul 29, 2015

We ran an air line outside in Ohio. 16' off the ground. 2" black steel pipe, sloped up about 3" in a 20' run building to building. Kaeser compressor and air drier feeds the pipe. Its been up there 16 years now, never frozen yet.

WHHJR · Jul 29, 2015

Follow leigh's direction for the pipe installation. Use a larger size than you need for flow ie 1" or 1-1/4". Call Raychem for heat trace and insulation recommendations. It will likely be around a 3 watt/foot self regulating trace and rubber foam insulation. In reality though a hose connection between buildings may do the trick for little cost.

The real Leigh · Jul 29, 2015

WHHJR said:
In reality though a hose connection between buildings may do the trick for little cost.

If you use a hose, the air must be really really dry.

Even a small amount of moisture will collect at the sag point over time, and can build up to the point where it will completely obstruct the flow if it freezes.

- Leigh

gbent · Jul 29, 2015

Run 2 smaller pipes. Insulate them electrically. Bond them in the building without a welder. Now when they freeze hook your welder up to the two pipes to thaw them out.

WHHJR · Jul 29, 2015

The real Leigh said:
If you use a hose, the air must be really really dry.

Even a small amount of moisture will collect at the sag point over time, and can build up to the point where it will completely obstruct the flow if it freezes.

- Leigh

The purpose of the hose is to have a TEMPORARY as needed connection. Take it off when not needed. How many 20 foot hoses do you have? I have at least 10.......

metlmunchr · Jul 30, 2015

You ALWAYS SLOPE AN AIR LINE DOWN IN THE DIRECTION OF FLOW.

The reason for this is simple. You cannot assume condensate will flow counter to the direction of air flow, because it won't happen. What will happen is condensate will continue to collect in the pipe to the point where it reduces the cross section to the point that the air picks up a slug of water and carries it thru the pipe and thru any regulator or moisture separator in its path.

Typical design velocities for compressed air systems vary from 15 ft/sec to 30 ft/sec. Any assumption that condensate will flow counter to these air speeds based on gravity induced by the typical 1/4" per foot grade on the pipe is both wrong and capable of causing damage to downstream equipment.

By sloping in the direction of flow, you keep a relatively small continuous quantity of condensate moving toward low points in the system where its easily handled by a separator.

https://www.omega.com/auto/pdf/CompressedAirTips.pdf Item 6, page Z-186 says slope in the direction of flow. I'd imagine Norgren knows as much as any company around when it comes to the correct way to run air piping.

Air line between 2 buildings

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