We needed to get a larger air compressor to power the grit blaster and the spray gun because the little compressor (Draper Website ) was finding it difficult to keep up with the demands placed on it.
We need one that provided at least 12CFM (Cubic feet per minute) of air and I needed the bigger compressor urgently to finish cleaning a tractor ready for spraying. Draper Website -again!. However what I did not realize is the figure that Draper (and Clarke ) referred to for CFM is actually the air displacement figure - that is the amount of air the compressor sucks in not the FAD (Free Air Delivery ) The higher figure - is misleading if you are trying to find the right compressor, Draper do put both figures on their website - because the FAD figure is the one that tells you whether a compressor will power the tools that you want it to. If you are working in a confined space i.e. a submarine you might be interested is the air displacement figure. I am in a barn so its of minor interest - however the efficiency of the compressor could be gauged by the difference between air input and FAD.
With the lower FAD of the compressor I had to make the supply lines as free flowing as possible. So 22mm copper pipe was used from the compressor to the first take off point and then into 15mm copper pipe up to the final water/oil filter and regulator. An OIL and Water filter has to be used because the new compressor is not an oil free one and some oil can end up in the air line. Pressure regulator is needed as whatever the compressor is producing often 116 psi is sometimes too much! I connected the line direct to the compressor receiver tank, bypassing the built in regulator. This needed a 1/2inch BSP male to male adapter and then flexible rubber pressure hose to 3/4inch BSP connector to connect to a standard 3/4 inch BSP tap fitting soldered to 22mm copper pipe
Welding: The DIY Guide is a great source of information on welding and paint spraying. Check out their website for the lots of information on air supply
 In this photo you can see the flexible pipe and the second compressor connection point. |
 |
I bought nearly all the standard copper pipe and fittings from Screwfix. To get as much air flow as possible I connected the air receiver directly to the air line via the special flexible pipe, connections needed are End Feed Straight Tap Connector 22mm x ¾" (57405) soldered on to the 22mm copper, you can use compression fittings I just prefer soldering fittings. The flexible pipe was made up by T Cook this is proper high pressure hose 3000 PSI burst pressure - way over the top I know. Screwfix and others do flexible tap connect pipe which is cheaper but I could find any specs on their burst pressure and mains water pressure is rarely more than 75 PSI / 4 Bar so 116 PSI / 8 Bar is pushing it!