Bristol 4S.7.40

[stuart1957]

Hi
New to this forum.
Just purchased a Bristol Pneumatics Ltd Compressor skid unit.
Model No :- B.P.S.40.C.N.G
Serial No :- B67573
Bristol Compressor block
Model No :- 4S.7.40
Serial No :- 67573
Looking for help and advice on re-commissioning the unit.
The compressor itself has not run for 6 years, turns freely by hand, has oil in the sump, looks ok in colour
Builds a little pressure by hand noticed on the condensate trap drain tap.
Have a manual for it too.
Running on Brigs and Stratton 5.5hp engine.
4 inch diameter pulley on the engine.
Don't think engine pulley size looks correct as it equates to nearly 4:1, meaning engine speed needs to be 4500 rpm ?? to get 1200 rpm at compressor flywheel.
Compressor and heat exchangers all look in very original un molested condition all identification plates are as it left the factory.
Has a PAS-5 filtration tower, any sources for cartridge ?
Any help would be appreciated.

 

[iain/hsm]

New to compressors I guess but this CNG bit may have put everyone else off using a compressor built for Compressed Natural Gas CNG and try to convert it for breathing air.​

Now the 6 years it lay idle may be enough time for the smell of gas to dissipate but if the CNG contained methyl mercaptan I would wait another 6 just to make sure its out of the castings.

An oil change would be on my list of first offs but first look at the first stage inlet connection is it a threaded pipe or is there a large black Vokes air intake filter fitted. Also the piston diameters in the manual would be useful.

As It's also important to assertain if this "40" in the Model No :- B.P.S.40.C.N.G number isn't the required gas (CNG) intake gas pressure in psi As 40 psi is typical of a CNG gas compressor
inlet pressure.

If so its not designed for an ambient air intake pressure. Or someone before you tried the modify it and jacked up the RPM to compensate for the lack of flow when using it at ambient pressure.
And also fitted a petrol engine as an add on modification.

Also what is the block colour Bristol Pneumatic (Fishponds Bristol) used to paint them light blue
for CNG use.

If the piston set on the first stage was designed originally for a 40psi inlet pressure it will be much smaller in diameter than for the same block designed for ambient air

If you were to run say a 10cfm 40 psi pump design originally for CNG but run it with ambient air it will run arounf half that flow and double the heat generated so the heat exhangers are under sized and overheat the oil, the compression ratio interstage goes into orbit and it basically cooks the oil overloading the chemical filter zeolite and the heat cant condence the water vapour out efficiantly enough.

Hope you can post pictures if for nothing else save all the angst or have a good laugh about it at least.

 

[stuart1957]

Hi
Some history for you, the compressor was used as a back up compressor on a boat in the South of England, Maidstone for some years, then sold and used by the previous owner for twinsets (twin 12s) for technical diving in the North of England.
The 6 year lay off period was due to him and his group having families etc, etc.
The intake side on the first stage does have a threaded intake with a large pipe tail screwed into it, around 3" long.
The Block is painted Black the rotation plate and the ident plate have no paint bleed on them.
The manual I have is for the 4S.7.40 block only.
Bristol Compressor block
Model No :- 4S.7.40
Serial No :- 67573
I shall try to upload pictures later

 

[stuart1957]

 

[stuart1957]

 

[iain/hsm]

Hi
Some history for you, the compressor was used as a back up compressor on a boat in the South of England, Maidstone for some years, then sold and used by the previous owner for twinsets (twin 12s) for technical diving in the North of England.

First the good news its an ambiant air block so suitable for breathing air and diving. Pweee!

Now this used originally as a back up compressor for a boat in Kent England I will buy that. The brits are happy in ignorance using junk old compressors. Gives then something to moan about when the tanks go rusty. The air intake hose is missing as proberbly the pump was stored below deck (so no rust) as a back up compressor so this all adds up.

Now used by the second owner for filling twin 12s for technical diving, what with that A clamp connection fitting!! No way. My take would be he bought it and never used it at best. Now did you buy it site unseen or did you see it run up to pressure? If he could get that Briggs & Stratton engine to fire up I fear the former.

Replace the drive belt, the rubber HP hose and any rubber stuff I would discard, use a pressure gauge you know is accurate and trust for the testing and not the one fitted.
Get that Briggs engine working first without the drive belt to the pump. If you manage to get that far look at replacing that old separator (silver) tower and the black chemical cartrige tower (black). The charging hose pressure gauge and that A clamp needs changing for a DIN connection.

Its not a Bristol factory standard build that Argus quarter turn valve for starters is an add on and a dozen other odd mods around the frame, belt guard and plumbing. But nothing that cant be repaired/replaced

So now you only need to disclose your intended use as your free divers forum consultancy period will expire soon.

If for diving you will need fitration to BSEN 12021 for UK use and that will need a better filter system than the BS4001 old system you have. If you intend using it for paintball then your in the wrong forum.

 

[stuart1957]

Thanks for your valuable information, the previous owner did fill his twins with this unit as I know one of his colleagues very well, he confirmed that they used it on a regular basis, with the Briggs and Stratton engine.
Purchased as a project not running.
Unfortunately the engine doesn't run now as the carb is varnished up.
I have another engine 5.5 hp Honda that I will transfer the pulley over to.
I will change the oil.
Then give it a run up.
Further to your comments re first stage piston size and C.N.G e.t.c, I have this morning spoken to a company who's MD is ex Bristol Pneumatics, he confirmed that the block and internals for ambient and C.N.G are the same.
He also said that the designed positive inlet pressure was very low.
Will replace both belts.
All rubber pressure pipes.
And the output pressure gauge.
Intended use is for breathing air again.
Fully understand the requirements on the filtration side.
Previous owner used an inline external air filter as his last filtration stage , which took an 'A' clamp fitting.
Where are you based ?
Thank you again.

 

[iain/hsm]

Im just glad your a diver, for a moment back then your first post and all I had you down as a paintballer.
We get an incresing number of them making first posts to get up and running then never add or contribute to the forum as I guess they sell them on ebay for loose change.

The RPM and pulley sizing you need to sort out Your Honda replacement engine depending on its size may have to turn full pelt at 3600RPM to achieve enough power to turn the pump over at full pressure.

The block is not an overdriven design, All you need is the driven pulley diameter and belt groove dims.
The ceter distance between the driver and driven pulleys and your required pump RPM
From the driver end the engine RPM and if big enough you can throttle it it back from 3600 to decide your driver pulley.

Another consideration is your max presure 232 bar is common and maybe better than 300 for such an old pump.
Also 5.5 BHP on a petrol engine maybe a tad too low for this block. If Honda maybe the 8 BHP unit they do
Its a common mistake to replace an electrical motor say 5.5BHP 4kW with the same size petrol engine.

Once serviced and parts replaced black hi temp spray paint on the block and the belt guard and frame poweder coated with new filters gauges and hoses and it may be a worth while project.

Noted on the CNG thats very good news for you The ambient air head takes low inlet pressure 0-5psi. For CNG the pump would be connected to the domestic gas ring using mains gas pressures not much above 20 millibar hence the same piston set. Lucky you it never tasted CNG

As you have the manual get an idea on parts costs with your ex Bristol contact also Gardner Denver in UK is a source of parts. Some parts you can buy direct like thoses cranky Enots tube fittings
Also be careful on the oil you choose These blocks had a nasty habit of coating the inside with black oil deposit, the minute you change from mineral oil to synthetic all the cooked deposits flake off and jam up the inlet and discharge valves making it a nightmare to strip down and de coke.

I'm based in UK.

 

[stuart1957]

Have done a bit of research on the oil front, with Shell, the original Rotella X 30 is now redundant but has been replaced by Rimula R3 + 30 as a 30 SAE mineral oil.
Its very difficult to determine which oil has been used, but it does look like like mineral oil.
The carbon removal using Andreol 500 or similar could be tragic.
From what I understand the Anderol is bright yellow when new, my oil looks to be reasonably clear deep green
Looking forward to recommissioning the unit, it may be old but its built to last as long as its maintained lets hope all goes well