NCR Booster service advice

[JackZwykle]

I have picked up a second hand NCR 220/2, so far it's working great for our small 3 diver CCR group.
I was told that in time I can service it myself, but I can't find any manuals, videos or even posts about it.

Does anyone have experience with that? I know I can send it to manufacturer, but I like to dabble myself plus the savings.

Will be appreciated.

 

[iain/hsm]

It's a very poor manual compared to the Haskel units with not much inside all of 12 pages
A parts list of 47 parts and a single outline drawing
No outlines no wear tolerance no lubrication components and no torque settings.
It talks about "Special Grease" but dont tell you the specifics.
Another of those "Scuba Specials" One of those things if you read the manual before purchase
you wouldn't bother.
But here you go enclosed below.

 

[JackZwykle]

Fenomenal, thank you!

 

[JackZwykle]

I guess I will contact the NCR for that specialist grease and torques when the time comes, so far it's not losing any pressure and works very well.
It was picked up from a dive centre where it worked for 10 years without issues (I dived there for years and I know it personally because my O2 was boosted by it).
When the centre closed I picked it up for a decent price, so no regrets.

This manual is indeed a bit simplistic, but much better than nothing.

One thing that surprised me a little is that they limit O2 boosting to x5.... that's not what I saw it used for and I boosted myself without issues (x8-x10).

I hope it's one of those "overly cautious about O2" things.
(Yes, I am charging <=6bar/min)

 

[iain/hsm]

I guess I will contact the NCR for that specialist grease and torques when the time comes, so far it's not losing any pressure and works very well.
It was picked up from a dive centre where it worked for 10 years without issues (I dived there for years and I know it personally because my O2 was boosted by it).
When the centre closed I picked it up for a decent price, so no regrets.

This manual is indeed a bit simplistic, but much better than nothing.

I would advise you first obtain a set of seals and gaskets directly from them and at the same time
gleen as much information as you can such as service life expectancy liner parts etc

Two reasons for this.
1. The pump wont get any younger and will at some point require wear component replacement
2. If and when they stop suppling you parts you have at least a fresh “Pattern” for an alternative supplier.

At the same time get them to advise what grease they recommend and the torque settings.
Looking at the pump and their entire range of compressor/ booster products it wont be anything special or advanced two maybe three types of lubricants will be used.

1. For the high pressure piston gas (oxygen side) end assembly probably nothing
2. For the spool valve control (oxygen side) probably a typical PTFE based Christo Lube MCG 111 or from the Krytox type range. Also I would consider as they are a German based importer possibly a German grease supplier such as Fuchs and from the Gleitmo range of lubricants.
3. For the Main drive piston (Air side) will be interesting to see what they recommend The usual oxygen lubricants would not be recommended and many of the silicone products such as the Dow Corning MS4 or Molycote III also wont work that well on such a large o-ring contact area and long piston stroke but the better lubricants are petroleum based and again any contamination would be cause for concern.

With the new seals and gaskets they are a 4 piece arrangement, a split rider ring and solid rider to avoid piston contact with the piston liner, a back up ring and the lipped seal ring.

Careful examination once you receive them will tell you if these rings are commercial off the shelf moulded rings or machined from solid rod “specials” One has smooth moulded side the other machined has fine gramophone record like grooves along the side walls.

From memory the heads are attached with Nyloc nuts so around a 15 to 20 ft/lbs torque should be more than sufficient even less.

 

[iain/hsm]

One thing that surprised me a little is that they limit O2 boosting to x5.... that's not what I saw it used for and I boosted myself without issues (x8-x10).

I hope it's one of those "overly cautious about O2" things.
(Yes, I am charging <=6bar/min)

At this point we would probably disagree I'm not a great believer in this scube doo cave fill mentality or the bull recreational divers have been fed as scuba divers by the rinky dink dive shops instructors and various rag tag vendors of products and other suppliers with little or no history with these kind of products.

But from the position of inert gases N2 He Argon and Breathing air etc the compression ratio is of little interest safety wise apart from reducing the service life of the components. But as the average scuba use is extremely light most scuba products out live the divers average 3 year active sports life.

However for oxygen it's a completely different position compression ratio CR is extremely interesting once you get above the 5:1 level. Add to this the adiabatic heat loadings together with the piston speed and piston stroke and gas velocity over the valve on the discharge side then you have the makings of a small ignition event. Granted most burn out quickly and all you see are some black specks in the discharge 2Mu filter matrix. But occasionally you get a "kindling" effect the result if which is melted metal spouting out and a big bang. Tests done say with this NCR German supplier would be BAM testing if indeed it has been independent tested. It would be interesting for them to publish the results if indeed they have bothered to test the product under BAM Approval but as they only sell to us lot scuba I would doubt very much that they have bothered.

IMHO and experience 8:1 and 10:1 is asking for an ignition event at some point especially as the discharge pressures for scuba are normally above the 150 bar maximum mark for gaseous oxygen compression. In industry we tend to use liquid oxygen to compress over 200 bar for safety reasons using a liquid compressor. And an oil free oil less oxygen compressor for gaseous oxygen compression rather than a booster pump while limiting the discharge pressure compression ratios and by using multiple stages or compression again to reduce risk.

In addition a typical design philosophy for an oxygen compressor is to load the compression ratio in at the first stage higher than the subsequent stages again to reduce risk but also by directing any fire event to the lowest pressure range. In additional key in the philosophy is to achieve an additional heat loading in the first stage again for reasons of safety. If you burn off the contaminant at low pressure and high temperature say at 10 bar gauge this can be a controlled burn in as it's called. By contrast the same amount of contamination at the 3rd or 4th stage and you picking metal out the walls.

With oxygen compressors designed for compressing pure oxygen even at the small 3 to 10 CFM range a printed "Burn in Procedure" is common practice with commissioning engineers. By contrast with boosters re constituted an inert gas pump into what is commonly called a "Gas Hammer" to pump oxygen you are on your own.

 

[JackZwykle]

I would advise you first obtain a set of seals and gaskets directly from them and at the same time
gleen as much information as you can such as service life expectancy liner parts etc

Two reasons for this.
1. The pump wont get any younger and will at some point require wear component replacement
2. If and when they stop suppling you parts you have at least a fresh “Pattern” for an alternative supplier.

At the same time get them to advise what grease they recommend and the torque settings.
Looking at the pump and their entire range of compressor/ booster products it wont be anything special or advanced two maybe three types of lubricants will be used.

1. For the high pressure piston gas (oxygen side) end assembly probably nothing
2. For the spool valve control (oxygen side) probably a typical PTFE based Christo Lube MCG 111 or from the Krytox type range. Also I would consider as they are a German based importer possibly a German grease supplier such as Fuchs and from the Gleitmo range of lubricants.
3. For the Main drive piston (Air side) will be interesting to see what they recommend The usual oxygen lubricants would not be recommended and many of the silicone products such as the Dow Corning MS4 or Molycote III also wont work that well on such a large o-ring contact area and long piston stroke but the better lubricants are petroleum based and again any contamination would be cause for concern.

With the new seals and gaskets they are a 4 piece arrangement, a split rider ring and solid rider to avoid piston contact with the piston liner, a back up ring and the lipped seal ring.

Careful examination once you receive them will tell you if these rings are commercial off the shelf moulded rings or machined from solid rod “specials” One has smooth moulded side the other machined has fine gramophone record like grooves along the side walls.

From memory the heads are attached with Nyloc nuts so around a 15 to 20 ft/lbs torque should be more than sufficient even less.

Sir, I owe you a beer.

 

[JackZwykle]

At this point we would probably disagree I'm not a great believer in this scube doo cave fill mentality or the bull recreational divers have been fed as scuba divers by the rinky dink dive shops instructors and various rag tag vendors of products and other suppliers with little or no history with these kind of products.

But from the position of inert gases N2 He Argon and Breathing air etc the compression ratio is of little interest safety wise apart from reducing the service life of the components. But as the average scuba use is extremely light most scuba products out live the divers average 3 year active sports life.

However for oxygen it's a completely different position compression ratio CR is extremely interesting once you get above the 5:1 level. Add to this the adiabatic heat loadings together with the piston speed and piston stroke and gas velocity over the valve on the discharge side then you have the makings of a small ignition event. Granted most burn out quickly and all you see are some black specks in the discharge 2Mu filter matrix. But occasionally you get a "kindling" effect the result if which is melted metal spouting out and a big bang. Tests done say with this NCR German supplier would be BAM testing if indeed it has been independent tested. It would be interesting for them to publish the results if indeed they have bothered to test the product under BAM Approval but as they only sell to us lot scuba I would doubt very much that they have bothered.

IMHO and experience 8:1 and 10:1 is asking for an ignition event at some point especially as the discharge pressures for scuba are normally above the 150 bar maximum mark for gaseous oxygen compression. In industry we tend to use liquid oxygen to compress over 200 bar for safety reasons using a liquid compressor. And an oil free oil less oxygen compressor for gaseous oxygen compression rather than a booster pump while limiting the discharge pressure compression ratios and by using multiple stages or compression again to reduce risk.

In addition a typical design philosophy for an oxygen compressor is to load the compression ratio in at the first stage higher than the subsequent stages again to reduce risk but also by directing any fire event to the lowest pressure range. In additional key in the philosophy is to achieve an additional heat loading in the first stage again for reasons of safety. If you burn off the contaminant at low pressure and high temperature say at 10 bar gauge this can be a controlled burn in as it's called. By contrast the same amount of contamination at the 3rd or 4th stage and you picking metal out the walls.

With oxygen compressors designed for compressing pure oxygen even at the small 3 to 10 CFM range a printed "Burn in Procedure" is common practice with commissioning engineers. By contrast with boosters re constituted an inert gas pump into what is commonly called a "Gas Hammer" to pump oxygen you are on your own.

Ok... 5:1 it is, no deviation.

Now that I have my own supply I think boosting to 200 bar is going to be exceedingly rare (just when filling O2 stage after an event).

I will be normally filling to 130-140 bar, so even 4:1 is tons of compression, I don't care about a couple of bars left in the O2 J.


Once again thank you.

 

[iain/hsm]

Ok... 5:1 it is, no deviation.

Now that I have my own supply I think boosting to 200 bar is going to be exceedingly rare (just when filling O2 stage after an event).

I will be normally filling to 130-140 bar, so even 4:1 is tons of compression, I don't care about a couple of bars left in the O2 J.


Once again thank you.

No Problem.

Can't see a problem per se with compressing oxygen to 200 bar (2900 psig) just not with a low inlet pressure. You can't have it both ways increase the pressure you increase the risk but if in addition as you decrease the inlet pressure then that risk increases exponentially. Especially as the doner cylinder pressure decreases as a factor of fixed mass gas transfer

From an oxygen production position this would be when a pure gas scavaging pump would be employed.

A small three stage compressor in effect to drag the last dregs out of the cylinder/s down to under a Bar (14 psig) .
Now from the point of economics and time taken these are generally used on expensive gasses such as Argon Krypton Neon `Xenon etc. or in remote areas of the world such as in small missionary hospitals

Incidentally I was involved in breathing Neon in a mix as an alternative to helium to counteract the heat loss and vocal distortion problems associated with heliox back in my offshore commercial diving days.
Never made it Into the big time scuba wise I guess the price per cylinder put folk off LOL But glowing in the dark and lighting up after sex also caused some difficulties.

The Brit contingent Stuart Clough and Peter Readey did however a number of dives for scientific purposes for Smith Kline Beecham on one of our modified Mk 15.5 and Mk 16 UBA and experimented with Jane Pimlott from the DDRC. To the best of my memory Jane still holds the depth record for Neon at 250MSW. Dr Maurice Cross played his doctor death part and also was in the dives with Comex on Hydrogen with the Hydra Progect (I think number 3) and Dave Crockford with Richard Dawson DDRC played the not bent yet unbenders.

But all thing being equal hydrogen as a diving mixtures is much more difficult to handle safely than oxygen so I guess its all relative. But pumping oxygen outside or in the shed and having a fire extinguisher on hand and two pairs of Nomex underpants on may be useful. You can thank me later LOL Iain