Compressor piping setup

[andeep]

Hi there,

This may be a fairly long post so please bare with me.

I have a Clarke SE18 4HP compressor rated at 18cfm, so probably around 12 cfm FAD. I also have a Clarke direct drive 3HP compressor rated to 14cfm, so probably around 9 cfm FAD.

I am going to use the air system for media blasting, spraying with an air fed mask and also with air grinders, sanders and an impact.

Therefore I have around 21 CFM FAD and I am going to run copper pipe around my garage. The run of copper will be around 6m to the wall regulator (1/2" BSP) and then that will be connected to an air reel. If I use 1/2" copper pipe that has a bore of 15mm and running around 100PSI, that gives me a pressure drop at the regulator of 0.47PSI. The 18m hose reel that attaches to the regulator has 1/2" BSP fittings and is 12mm bore, therefore the pressure drop at the end of the reel where the tool connects will be 4.35PSI

Does this seem ok? A pressure of 99.53 PSI at the regulator, then after the hose reel where the tool connects a pressure of 95.18. Does this seem okay considering most tools use a pressure of 90PSI?

Will this setup be able to supply enough air for an air fed and spray gun?

The 4HP compressor supplies are at 10 BAR (145 PSI), is there any point in having the compressor set to this high pressure or should I adjust this so that it is around 105 PSI and leave the other 3HP compressor at 100PSI? The 5PSI difference is so that they don't start at the same time to avoid mains surge.

I will be running 1/2" piping an 1/2" BSP fittings at the compressors and at the regulator and hose reel. What sort of quick disconnects would be suitable at the end of the hose reel to attach to the tool? I don't want these creating a restriction. Seeing as the standard PCL ones have a bore of 4.8mm, but they are very short, therefore the pressure drop caused by these will be negligible?

 

[Gareth0123]

Have you considered using either of the following airline quick release couplings:

Parker Twist Lock airline fittings

Or

Atlas Copco ergoquip full flow quick release airline couplings

I have used both in 1/4 and 1/2 BSP and they are far superior to the PCL fittings

 

[rtbcomp]

All seems OK to me. dropping the pressure to 105 would mean the compressor will be less stressed.

 

[andeep]

Thank you for your reply rtbcomp, it is much appreciated.

One thing I can't understand is why some people say that PCL quick couplings can't flow enough CFM because they have a small bore. Looking on their website it says that they can flow 43CFM at 100PSI?

 

[Farside]

Thank you for your reply rtbcomp, it is much appreciated.

One thing I can't understand is why some people say that PCL quick couplings can't flow enough CFM because they have a small bore. Looking on their website it says that they can flow 43CFM at 100PSI?

I made the mistake of going with PCL connectors because that's what was available locally. When I changed over to the Euro connectors, the extra grunt from the air tools was really noticeable. Iirc, they flow about 50% more.

 

[rtbcomp]

The trouble with quoting CFM is that it's pressure dependant, the higher the pressure the more cfm you can squeeze through a hole.

 

[dannyp]

just had a read of the specs they sound good at first read but then you think about it. they say it flows upto 43 CFM @ 100 psi. what it should say is pressure drop @ 43 cfm = 100 psi , they claim the nominal bore to be 4.8 mm aka 3/16ths so quick look up of blasting nossels.

@ 100 psi a 4.8mm nossel needs 45 cfm. so that supposrts the 100 psi pressure drop at 43cfm. looking at the flow requirements for blast nossels down to 50 psi shows some worryingly high numbers. so did a bit more searching. and found this

http://azglassclasses.com/Reference/CFM-PSI.htm

3.9 CFM = 1 psi
8.7 CFM = 5psi
12.3 CFM = 10 psi
15 CFM = 15 psi
20 cfm = 17.1

but on an airline you chould double that as there is a quick release at each end. ( at this point i've just had a moment of realisation ) a half usefull rattel gun is going to want 15 cfm so chould be useign 30 psi in the pcl connectors, + whats lost in the airline, no wonder putting airlines straight on the tank helps the tool is proably only just getting its working pressure then

 

[normspanners]

I dont understand your logic in this post
especially the

pressure drop @ 43 cfm = 100 psi

What that stated flow is telling you quite simply is the the amount of cfm though the connector from the tank side to the tool at 100psi which is 43cfm with NO pressure drop on the tool side
After 43cfm used, you WILL suffer pressure drop.

15 cfm so chould be useign 30 psi in the pcl connectors,

???? Sorry no idea what this means

3.9 CFM = 1 psi
8.7 CFM = 5psi
12.3 CFM = 10 psi
15 CFM = 15 psi
20 cfm = 17.1

You have these figures completely the wrong way ie 3.9 CFM = 1 psi ??
what that chart is telling you is a 4.8mm hole at 1psi passes 3.9cfm etc etc

 

[dannyp]

my logic is very very simpel here.

we are dealing with air, not a super fluid therefor ANY flow will enounter resistance, resistance to flow in a pipe / system causes pressure drop.
in simplest form i'm presenting the idea

A PCL connector has a nominal bore of 4.8 mm.

A PCL connector is not unlike a crude media blasting jet would it be therefor not be reasonable to assume flow rates chould be simalar.

the PCL connectors are quoted as flowing 43cfm @ 100 psi ( that sounds good ) a media blasting nossel of 3/16th or 4.8 mm is quoted as flowing 43 cfm @ 90 psi or 45 cfm @ 100 psi

those numbers are very very simalar so for guestimation pourposes i've declared them to be the same thing. a 4.8 mm blasting nossel and a 4.8 mm PCL connector will flow around 43 to 45 cfm . with a 90 - 100 psi pressure drop across the nossel or pcl connector.

there is no way your going to manage any significant flow through a 4.8 mm nossel / connector / hole without a pressure drop. hell if you chould find a way of getting 40 cfm to flow through a 4.8 mm nossel without a pressure drop you'd be very very rich.


the figures arn't the wrong way round they are the other way round.

a flow of 3.9 cfm through a 4.8 mm nossel will give a pressure drop of 1 psi or 1 psi of pressure will cause a flow 3.9 cfm through a 4.8 mm nossel, same data written the other way round.

all i'm saying there is X cfm of flow is going to cause X PSI of pressure drop

 

[normspanners]

43 to 45 cfm . with a 90 - 100 psi

No ------you have it wrong where does it say there is a 100psi pressure drop?

a flow of 3.9 cfm through a 4.8 mm nossel will give a pressure drop of 1 psi or 1 psi of pressure will cause a flow 3.9 cfm through a 4.8 mm nossel, same data written the other way round.

NO------that chart is saying-------- AT 1psi ----that pressure will flow 3.9 cfm through a 3/16 nozzle it doesnt mention pressure drop because there is TOTAL pressure drop (to 1atm) through a blast nozzle, from, whatever your line pressure IS say 100psi TO 1atm

 

[dannyp]

for the most part the chart dosent matter it was just trying to eleaborate the idea a bit more

but further up the tabel blast nossel with PCL bore is show to flow near as dammit the same CFM as a PCL connector at the same pressure. both items in there simpelest form are a bit of pipe. i dought there flow v's pressure drop is going to be that diffrent. that combined with 10 minutes playing about with some pressure gadges and airline connectors this morning, means shortly i won't have any PCL connectors in the workshop

anyway were never going to agree,

 

[normspanners]

anyway were never going to agree,

I am not trying to argue with you, I just think you have the wrong end of the stick, all I was trying to do was explain that while yes PCL's do restrict the flow, it is no way as much as you are thinking.
CFM blowing through a pipe is not what you 'have' on the tank side of the coupling, it is the resulting amount of air that is travelling out of the connector/orifice, into the other pipe or atmosphere and the result of a specified air pressure against, a set orifice.

 

[langy]

Your setup sound very like mine, I use normal PCL fittings and have done for years, never had a problem

 

[brightspark]

it depends on what u are using on the end of your line. i use half inch ball valve on the compressor tank and use claw couplings with 15mm bore pipe to the blasting pot no restriction whatsoever. the drop in pressure at the nozzle is verry noticable using standard pcl couplings. i have a 3/4windy gun and it doesnt like the small conectors either

 

[normspanners]

it depends on what u are using on the end of your line. i use half inch ball valve on the compressor tank and use claw couplings with 15mm bore pipe to the blasting pot no restriction whatsoever. the drop in pressure at the nozzle is verry noticable using standard pcl couplings

^^^^^^

in the way of a coupling yes, but not a tool.because if a tool needs,100psi and uses 30cfm then you have to fit the coupling to suite.

pressure drop @ 43 cfm = 100 psi

dannyp made the above statement which is totally wrong

 

[normspanners]

PCL Std Coupling - Standard Vertex - Female Thread - 1/4 Inch BSP
Flow rate: 42 cfm @ 100 psi (3 psi pressure drop)
Maximum pressure: 200 psi
Temperature: -40 to +100 deg C

(3 psi pressure drop)

this is the rated pressure drop across/through this coupling at 100psi
Which there is obviously less drop at more psi.

 

[dannyp]

at some point may have flow test said fittings.

for a while i've been using the air heavy kit with no quick connectors. air inpactors 1/2 and 1" are connected straight onto the airline and to the main air ring via a ballvalve. they run a lot better that way

 

[normspanners]

for a while i've been using the air heavy kit with no quick connectors. air inpactors 1/2 and 1" are connected straight onto the airline and to the main air ring via a ballvalve. they run a lot better that way

Yes they will run better.
I use the 100 series PCL for large kit.http://www.ebay.co.uk/itm/PCL-AC5JF...518?pt=LH_DefaultDomain_3&hash=item27bf4c5dae
Designed and manufactured in Sheffield by PCL this traditional PCL coupling range offers greater airflow characteristics for the larger air tool applications in garage and tyre shop environments.

Sleeve is marked "M100 Coupling - Series 326" and "Patent No 995589".



Key Product Benefits

• Hardened steel shoulder prevents accidental disconnection
• Secure locking device
• Swivel feature prevents kinking of the hose
• Specially designed valves and large aperture provides optimum air flow

Specifications
Nominal bore 10.3 mm
Maximum flow rate 117 cfm @ 100 lbf/in²
Temperature Range -40°C to 100°C
Maximum Working Pressure 200 lbf/in² 14 bar



and for VERY LARGE gear ie blasters jack hammers etc claw fittings.

 

[brightspark]

i use them on most things then drop to these at the end of the long hose