Restrictive fittings...?

[The Z'eer]

Going by recent information I've been advised to use 1/2" BSP fittings, 10mm bore hosing etc. However, I have noticed quite a few popular brand air tools/guns and regulators are using 1/4 BSP fittings.

So if I am to use the larger bore hosing and fittings, surely it's purpose of aiding faster/greater volume of air will be defeated by the smaller 1/4" fitting at the tool?

Comments appreciated

 

[optima21]

no

 

[Toleman]

You would think so but gas fitters to combi boilers run 22mm most of the way then do the last metre in 15. I'd be interested in the answer too

 

[The Z'eer]

no

Any science behind that?

 

[The Z'eer]

You would think so but gas fitters to combi boilers run 22mm most of the way then do the last metre in 15. I'd be interested in the answer too

I wondered if by using some restriction, the purpose is to cause a pressure increase?

 

[armalites]

1/2 BSP are a really big fitting and not needed. A 1/4BSP fitting can flow way more than a standard compressor can keep up with anyway. The biggest issue are the quick release couplings. The standard PCL fittings which the most common work fine but PCL XF do make a difference.

Nearly all normal air tools run 1/4bsp or 1/4npt fittings. I have probably 25+ different air tools of different brands and not one of them runs anything bigger than 1/4.

There is an alwful lot scare mungering goes on with air hose bore etc. In many senarios even 6 and 8mm will work perfectly fine.

 

[armalites]

I have a hose with 1/2bsp fittings and it has 19mm bore so 1/2bsp will look silly on a 10mm hose

 

[brightspark]

well heres mine and if i didnt use 15mm bore pipe id notice the difrence on blasting pressure at the pot. all; other tools run on 10mm bore pipe using 8mm whip tails on the last meter my half inch and 3/4 windy guns do not like being restricted

 

[Maker]

I wondered if by using some restriction, the purpose is to cause a pressure increase?

It doesn't work like that, the air will move faster through the restriction but its pressure will be lower;

I don't know the name of this device but air flows through the top tube from left to right and the height of the water in the three manometers shows the relative pressures at the three points. You can see the pressure is highest at the start, greatly reduced at the restriction and then regained but still slightly reduced afterwards.

Depending what the weather's like tomorrow, I'll do some experiments with various hoses and fittings to see how much oomph you'll lose with a smaller fitting on the tool.

 

[brightspark]

here http://www.air-compressor-guide.com...pressed-air-piping/compressed-air-pipe-sizing. anyone putting a lot of bends in pipe for cooling is reducing the air flow pipes are best as strait as possible

 

[brightspark]

the easy way to measure air loss is use a pressure gauge at source and one on the end of the line . then use the tool any loss will be evident if there's a restriction in flow. quite simple not rocket science

 

[delta9]

and theres the option of getting a secondary/bigger tank for air tools (air receiver or a couple of those big orange homeless gas bottles joined together )

then you use your current compressor/pipework to fill that with air for those air hungry tools

 

[brightspark]

and theres the option of getting a secondary/bigger tank for air tools (air receiver or a couple of those big orange homeless gas bottles joined together )

then you use your current compressor/pipework to fill that with air for those air hungry tools

like this even though I run large bore pipe it has a pressure gauge on as well so I can check for drop not that I need to there is none I use it to cool the air and its also portable so I can blow tires up in the field or on drive . I don't need exra storage as the compressor has a massive tank and its 28cfm twin pump

 

[delta9]

Handy little tank, nice one, how many psi/bar can that safely hold?

 

[brightspark]

haven't a clue it held gas and the tank is thick ish so it will hold 150 psi no problem .believe it or not a 1gallon oil can with crimped ends can pressurise to 50 psi before it will burst

 

[brightspark]

here it is I hid round the corner http://www.mig-welding.co.uk/forum/threads/testing-a-pressure-vessel-oil-can.25381/

 

[indy4x]

Just changed all my fittings from 1/4 BSP PCL to 1/4 BSP PCL XL and defo noticed a difference when using the windy gun, much better

 

[gordon stephenson]

Depending upon hose length there will be a greater resistance to flow and i.e. pressure in a smaller bore hose. In the average small workshop 10mm should be ok for most applications. Blasting or impact guns would benefit from 12mm bore, with a short whip hose to the machine,

 

[optima21]

from my other post on your thread about airlines.

http://www.mig-welding.co.uk/forum/threads/inline-regulator-filter.74916/

where I showed the pressure drop on 25m of 10mm hose being 1.25 bar at a working pressure of 3.5 bar and the flow being 8cfm

the specification for the xf fittings is 0.5 bar pressure drop at 6 bar working pressure at 78 cfm

in other words the restriction in the air fittings have 1/20 of the restriction of my air hoses

see page 5 of this link for the pcl specification

https://www.buckandhickman.com/Assets/BuckHickman/DataSheets/PD_080115.pdf

the bore through any 1/4 bsp fitting is likely to be larger than the bore of the xf fittings so 1/4 bsp fittings should be able to flow more air for a given pressure drop than the xf fittings.

if you're worried about the flow rates through fittings just get the compressor upto working pressure, switch it off, connect the fittings to the compressor and see how long it takes to get to a certain pressure (e.g. 50 psi). then do the same with the air hoses fitted and see how much longer it takes.

I did a similar thing in post 4 on this thread about regulators

http://www.mig-welding.co.uk/forum/...e-ditching-cheap-regulator.72826/#post-992904

 

[rtbcomp]

It doesn't work like that, the air will move faster through the restriction but its pressure will be lower;
View attachment 115354
I don't know the name of this device but air flows through the top tube from left to right and the height of the water in the three manometers shows the relative pressures at the three points. You can see the pressure is highest at the start, greatly reduced at the restriction and then regained but still slightly reduced afterwards.
....

It's a venturi.

The drop in pressure along a pipe is a factor of length and diameter, if you have long length increasing the diameter will improve the air flow. The narrow fitting is so short as not to make a significant difference.