Why is my air compressor not powerful enough to run my impact gun?

hassy786 · 3 Sep 2021 at 22:54

Hello,

I hope I put this in the right forum but not many websites to ask this question on... I bought myself a Workzone 3HP 50 litre 14.5cfm max operating pressure 8 bar air compressor and also a impact gun rated at doing 1700nm loosening torque which I wanted to use with my air compressor but every time I go to use the gun, it sounds like it has no power. Runs fast when not opening the bolts but when opening a wheel bolt, it sounds like it is struggling/not getting enough power.

I messaged the seller thinking it was a faulty gun but they told me it is because my air compressor cant handle it and the gun is perfectly fine... Now although they gave me a small discount out of good will, I would still like to use the 1700nm torque it is offering so what am i doing wrong?

The gun specs

standard operating pressure 90psi
avg air consumption 6.cfm (170l/min)
air inlet size 1/4
air hose (ID) 3/8

my air compressor specs

Maximum operating pressure 8 bar
Air displacement 14.5cfm
Tank size 50litre

Going by the papers it seems like it should run it fine as my compressor does 8 bar and has a displacement of 14.5 whereas the gun requires 6? So what am I missing out? Granted the gun requires 3/8 hose whereas I am using a 1/4 hose however the couples on the gun are 1/4 any way and the seller has already told me it would make no difference using a 3/8 hose as it is the compressor that I need to change. So could someone tell me what exactly I need to look at when buying another compressor and why my current compressor cant handle the gun?

Thank you very much in advance.

Dandle · 3 Sep 2021 at 23:13

I would start with increasing the tube size, 1/4" hose will flow a lot less air than 3/8. It doesn't matter that you have a smaller fitting at one end the hose will still cause a restriction.

You compressor might be a bit on the small size but start with the hose and see how it goes. https://www.sgs-engineering.com/help-advice/what-cfm-air-compressor-is-needed-to-run-air-tools/

g60dubster · 4 Sep 2021 at 00:24

Had a compressor this size and power many years ago, it was useless for anything other than inflating tyres and maybe a nailgun. Couldn't power any tools with decent pressure or the pump would run continuously (which is bad for them, and really bad for spray guns, but also creates significant pressure fluctuation in tools)
Changed for a 150ltr tank with a true 3hp belt driven pump and the difference was unreal - yes the tank was 3 times the size but the pump was over double the stable cfm when using air tools (impact, screwdriver, cutoff saw etc)

sja360 · 4 Sep 2021 at 08:03

g60dubster said:
Had a compressor this size and power many years ago, it was useless for anything other than inflating tyres and maybe a nailgun. Couldn't power any tools with decent pressure or the pump would run continuously (which is bad for them, and really bad for spray guns, but also creates significant pressure fluctuation in tools)
Changed for a 150ltr tank with a true 3hp belt driven pump and the difference was unreal - yes the tank was 3 times the size but the pump was over double the stable cfm when using air tools (impact, screwdriver, cutoff saw etc)

It might be this, although the cfm is fine the capacity of a 50L tank won't be much, so probably within a few seconds its running out of pressure and the compressor is kicking in trying to keep up.

1700NM is a fair whack of torque, what is it your doing with it :confused:

dlockers · 4 Sep 2021 at 08:26

Remove the regulator from your compressor entirely. Your compressor is no where near big enough for proper use though. I know because I made exactly the same mistake.

Then I realised it was a stupid amount of money to spend to undo wheel nuts and sold it.

DXP55 · 4 Sep 2021 at 12:48

Dandle said:
I would start with increasing the tube size, 1/4" hose will flow a lot less air than 3/8. It doesn't matter that you have a smaller fitting at one end the hose will still cause a restriction.

You compressor might be a bit on the small size but start with the hose and see how it goes. https://www.sgs-engineering.com/help-advice

/what-cfm-air-compressor-is-needed-to-run-air-tools/

Have to agree with this reply -Mate over the road suffered same problem -first he renewed his compressor for a twin 50lt compressor and then still found it wasn't enough so he bought all new hoses and fitting with as big a diam as he could -that still wasn't enough so now he also has two of those huge propane tanks connected.
It's more about stored air capacity and hose size than anything else.

I have a small portable compressor and also have a 50lt propane tank connected as well.
If you start playing with different fitting use gas PTFE tape as well - not thin plumbing stuff.

Hotwired · 4 Sep 2021 at 13:26

The connector to the gun might be 1/4 but everything between the tank and the gun restricts the air flow so the fatter and shorter the hose to the tank the better.

Mind you if the outlet from the tank is 1/4 there's no point in a fatter hose.

Dandle · 4 Sep 2021 at 19:28

Hotwired said:
Mind you if the outlet from the tank is 1/4 there's no point in a fatter hose.

No there is a point to the larger hose, it will still help and give you a better flow even is there is a restriction in the line beforehand.

Mysterae_ · 4 Sep 2021 at 22:34

DXP55 said:
I have a small portable compressor and also have a 50lt propane tank connected as well.
If you start playing with different fitting use gas PTFE tape as well - not thin plumbing stuff.

For even better than the PTFE tape, use some Loctite 55 pipe sealing cord, great stuff.

Richie · 5 Sep 2021 at 14:36

Your compressor might state 14.5CFM but that may be displacement and not Free Air Delivery (FAD) which would be lower.