Gasoline exhaust and intake air placement for trailer.

[tanksforthememories]

I have searched and haven't found a clear answer to this question. Where should the gasoline motors exhaust exit the trailer in rel'n to the compressors air intake? Is there any harm in over sizing the intake plumbing? I am thinking of plumbing an Alkin W31 gasoline powered 3.5cfm compressor in a 12x6 covered utility trailor. From what I am hearing plumb the exhaust low and at opposite end of the trailor to the high 3inch diameter intake. Is this correct? I should also have the ability to position the intake upwind of the exhaust no matter how the trailor is parked, (on a swivel). Is this correct? Also watch for car,truck exhaust and other sources of impurities ie barbecues, solvents etc. Am I right in this? Any help is appreciated.

 

[swamp diver]

Yes exhaust low and intake high however you will run into real problems on windless days especially with only a short distance separating the two. The exhaust will build into a plume and travel horizontally and vertically until it engulfs your intake. I've see an exhaust plume travel the length of a fire truck and a large boat on windless days.

I wouldn't use a gas-powered compressor unless it has a catalyst bed (i.e. Hopcalite to convert small amounts of CO to CO2) and definitely a CO monitor on the output. You can purchase a CO monitor from Oxycheq, Nuvair or Analox to plumb into the compressor discharge air.

Have a look at the thread below to see the risks of using gas-powered compressors.
http://www.scubaboard.com/forums/co...ding-systems/458853-why-i-own-co-monitor.html

 

[tanksforthememories]

Thank you Swamp Diver. Would a hand held, Analox Co EII work? Or is the inline, Analox CO Clear, better? I like the idea of portability of the handheld for trips and the like. The system has the P21 filter from Lawrence Factor with AC and Hopcalite, but I am getting a second coalescer and filter tower from LF. Do you think 3inch exhaust for the motor is a good idea?

 

[Wookie]

How will you get cross flow ventilation to keep the compressor cool? I have a friend who has his in the man-door in the front of the trailer, but that negates use of the man door. He went a different route, he uses an electric compressor and a generator to run it. He has a 100 foot cord on the generator, so he can move the generator downwind wherever he sets up.

It's something to think about.... the other advantage is that he can plug the trailer into house current when he's home and not have to run the engine to fill tanks.

 

[swamp diver]

Thank you Swamp Diver. Would a hand held, Analox Co EII work? Or is the inline, Analox CO Clear, better? I like the idea of portability of the handheld for trips and the like. The system has the P21 filter from Lawrence Factor with AC and Hopcalite, but I am getting a second coalescer and filter tower from LF. Do you think 3inch exhaust for the motor is a good idea?

You could use the Analox CO EII and just check every tank filled, but the day you forgot to do so will be the day you'll find a CO contaminated fill. We use the Analox CO Clear which is a fixed unit but it will likely cost you $1300 when all is said and done with regulators, cal gas, cal gas regulator, etc.

The real trick is keeping the exhaust out of the intake and keeping an eye on where it goes when there is no wind around. Even hanging a small handheld CO monitor with 95 dB audible alarm and visual alarm on the intake would give you an idea of exhaust activity before it gets entrained into your compressor. I know one fire service which now does this with all their portable gas-powered compressors and the compressor intake is up at the cab with the compressor at the back of the truck. You can purchase from Canarysense.com a disposable analyzer which does not need calibration for 2 or 3 years. Just be careful as some of the CO analyzers will lock you out if you don't bump check or calibrate at a particular time interval. I think on the BW Tech units you can turn that feature off.

This unit from Oxycheq is easier to plumb into your compressor and can be taken on trips as well.
Oxycheq CO Analyzer - Cave Country Diving Store

I would consider what Wookie is saying about ventilation for the compressor since a hot compressor is also problematic. Using a generator may allow a greater separation between compressor intake and exhaust source.

 

[tanksforthememories]

I like the idea of the generator. It would mean an electric motor big enough to supply 5hp. The compressor shop was saying that would involve a large sized generator. Financially not viable at the prices quoted especially after just buying the unit with the Honda motor attached... I won't be filling lots of tanks. Likely 4-6 a week. And I have 11 tanks at the moment so I will only fill on days with at least a breeze. Ventilation is more of an issue. The trailer has a ramp style back door and a"man" door on the front right side. I am thinking I will need a 12v or battery powered fan big enough to move some air through the trailer. Nights here in the Rockies are usually cool and windy but air flow is important to keep the oil from creating CO. I am torn over which CO detector to get...

 

[rjack321]

Wheel the (gas powered) compressor out of the trailer for fills. Then use a long but large diameter snorkel for the intake. I have a W31 and a 2" diameter reinforced hose works fine as a snorkel. You can put the inlet filter on the end using a 2" to 3/4" PVC reducing fitting. You'll need some other brass or PVC fittings to upsize the compressor inlet too. I think my "mobile" snorkel is about 12ft long. Put some string on the end and hang it upwind.

And use triplex filters. I use the pre-packed ones. My summertime experience is that I get a max of 10 hrs out of a P0 filter. Because I am manually checking the hours (no hour meter on the gas engine) and its hard to have the 10/20/30 humidity disks in the bush, I change the pre-packed filter at about 8 hours. I only use my W31 with a gas engine for a week once a year though.

 

[tanksforthememories]

Thanks rjack. That is what I did last year but after reading all the threads about CO danger I decided to increase the filtration. This means a second tower which needs to be fixed in place. I guess I may be able to get a flex line long enough to connect to the tower from the compressor which would allow for the movement of the compressor to the outside...? I worry about stress on the connection points causing a leak. Another thought is the risk of tank failure because of the temperature in the trailer. If I add more vents to the trailer Al80's filled to 3000psi should be okay wouldn't you think? Definitely a lot to think/worry about.

 

[Wookie]

I know it isn't helpful right now, but when a hurricane is coming, folks buy Home Depot/Lowe's/etc. out of 25kw gen sets. After the hurricane, they take them back. These can't be sold as new, so the big box stores sell them out for cheap cheap. Keep your eyes open. Additionally, big Lincoln and Miller Bobcat welders are also generators, and can be bought very inexpensively. I would prowl the boatyards (not newbuild, but repair yards) in Vancouver for running takeouts or overstock gensets. They take more work, but if you are handy enough to mount a air compressor in a trailer, you should be able to turn a keel cooled generator into a radiator cooled one.

 

[tanksforthememories]

Just a thought, the pre filter for the intake has an opening of 3/8's of an inch. If I increase the diameter of the snorkel to three inches shouldn't I increase the size of the pre filter? Otherwise the bottle neck is the same 3/8's of an inch.