The strip and rebuild
Main Haskel booster page

If I don't keep notes then it will all go wrong and if I do a proper write-up I can save myself endless bother when I have to service it again. The pictures were taken prior to cleaning so I had locations for rings and things so that is why they look grubby.

So let's start here. This is the key to understanding how the Haskel works. This is the spool and sleeve that are used to direct the drive gas to the appropriate end of the drive cylinder and to vent the exhaust on to the heat exchanger. This is what I think is the smart bit.

The first point is that they go this way round. You have to look carefully at the manual to work this out and the sleeve will fit either way and only works one way. There is a rubber lined washer at the left hand end to make the seal work. It is referred to as the bumper and fits rubber side towards the sleeve. The rubber is to act as a soft end stop for the spool and is made with slots to prevent it sealing like a suction cup and stopping everything moving.

Block The sleeve mounts in the bottom of the block in the big hole. It is feed with drive gas into it's centre section, the left hand end is connected via a pipe to the far end of the drive piston and the right hand end feeds directly to the near end. As the spool moves back and forth drive gas is directed to alternate ends and exhaust gas is vented to the hollow body of the spool.

The little pin I have marked as a poppet is touched by the drive piston at the end of its travel and feeds drive air to the closed left hand end of the spool driving it to the right. Drive piston This space at the end of the spool is also coupled to a similar poppet at the other end that vents to the open air removing the pressure so the spool is no-longer held right and the pressure of the exhaust gas within it drives it back to the left. There is a slight tweak using the piston on the end of the sleeve to reduce the overall effect of the exhaust pressure but that enables Haskel to run without springs except in the valves and without detents. Frankly I'm impressed. This is probably why my 20 year old pump looks so new inside once I'd cleaned it up.

HP pump The piston drives the high pressure pump which, as you can imagine when we discuss 775bar, is this thick walled device. The drive shaft is a close fit in the 16mm bore but to compress 775bar would take about 1500Kgs of force, a ton and a half roughly, so it needs to be serious metal.
Inside it has a complex array of parts including one silly little washer like bearing that needed changing from normal to oxygen service and took weeks to come.

The moving gas seal on the piston is hideously complex but the supplied diagram spells it out nicely enough. As I had to replace my obsolete end cap I just ordered that in oxygen service so I didn't need to do anything other than bolt it on.

Other problems
Well the connection between the Swagelok parts and the Subaqua Products parts was more problematic than I expected. The top picture to the right, P1, is the Swagelok part 400-7-4RG. The second and third pictures, P2 and P3, are of the SAP 3084 300bar Elbow. I wanted them to connect but the Swagelok part lacks a cut out for a SAP sealing ring on the shoulder as it expects one at the bottom.
Unfortunately the part I wish to screw into this is shaped as P4 (SAC 1625) and it will not sandwich a washer as it has a cut out for the conical adapters of the hoses as in picture P5.

I started by trying to sandwich an O-ring regardless of not having a cut out but that popped out at about 80 bar so, after some experiments I contacted SAP who tried to solve the problem by making the washer shown in P6 with a conical end to go into the screw in and a flat side to mate up against the Swagelok fitting. The part looked right so I assembled it finger tight and put some gas pressure on it. It hissed. I gently tightened the fittings. It hissed less, less, less, more. OH DRAT. Tightening it up and applying pressure had rendered it P7.

There was a delay but when I discussed it with SAP we came to the conclusion that we needed metal and settled for Brass. They made the part shown in P8 and I sandwiched an O-ring below the flat side and spannered it up. I let the presure on gently - no hiss so I assembled the other side and tested it. Chuff-phut, Chuff-phut we were pumping gas.

We fixed it but it does seem ironic that the biggest problem was nothing to do with pumping reactive gas at high pressure they were just the usual run of the mill problems you get connecting any two dissimilar systems.

The only other snag is that a 770bar pump will destroy a 275bar gauge in moments if you shut the valves in the wrong order. <sigh> Such is life.
Mouse over the picture for the identifying text

P1 - Swagelok 400-7-4RGP2 - SAC 3084 300bar Elbow
P3 - SAC 3084 300bar Elbow detailP4 - SAC 1625
P5 - End of a SAC flexible HP hoseP6 - Attempt one in PTFE
P7 - Attempt one after pressurisingP8 - Attempt two in brass

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