Connect appropriate transfer whips to the inlet ( I ) and outlet ( O ) ports on the cylinder head and attach these to the supply tank and the fill tank. Slowly open the valves on the fill tank and supply tank. (Very slowly if you are boosting oxygen!) Open the line valve, if present, and allow the fill tank to equalize to the same pressure as the supply tank if the fill tank pressure is lower than the supply tank pressure. Drive gas is normally provided from a scuba tank equipped with a standard first stage regulator adjusted to 147 psi (10 bar) and is connected to the booster with a standard low pressure inflator hose.

Slowly open the valve on the scuba tank to start boosting. There will be a clicking sound as the piston starts it’s pressure stroke and a hissing sound from the muffler as the piston is returned to the bottom of it’s stroke. If the booster doesn’t start when the valve is opened try disconnecting and venting the inflator hose, reconnecting the whip, and opening the valve again. The booster won’t cycle without pressure at the inlet port.

The pumping speed is internally regulated and provided the drive gas pressure is adequate, depends on two factors.

1) the fill tank pressure.

2) the supply tank pressure.

The higher the fill tank pressure the slower the booster will cycle. This is independent of the pumping efficiency. Ultimately the booster will stall as the fill tank pressure reaches the 23:1 ratio of drive gas pressure vs. fill tank pressure.

The higher the supply tank pressure the better the pumping efficiency will be.

Drive gas is consumed in direct proportion to the fill tank pressure and number of strokes.

Using compressed gas to compress gas isn’t necessarily efficient, but it can be convenient.

As the supply tank pressure decreases the drive gas consumption increases dramatically and the time required to pressurize the fill tank increases due to less gas being actually delivered to the fill tank with each stroke.

If the fill tank pressure is near the maximum (approximately 3200 psi/218 bar) each stroke will use 176.7 cubic inches (2.9 litres) of drive gas no matter what the supply tank pressure may be. If the supply tank pressure is 3000 psi (204 bar) the pumping efficiency would be approximately 90%. If the supply tank pressure is 500 psi (34 bar) the pumping efficiency will be approximately 12% and the drive gas consumed would still be 176.6 cubic inches (2.9 litres) per stroke.

Consider the situation from a mechanical perspective:

If the fill tank pressure is 3000 psi (204 bar) and the supply tank is 2000 psi (136 bar) the high pressure cylinder of the booster will be filled to a pressure of 2000 psi (136 bar) at the beginning of the compression stroke. The total stroke length is 2.5 inches (63.5 mm). The piston will travel .83 inches (21 mm) in order to raise the pressure in the booster cylinder enough to equal the pressure in the fill tank. Only then will the booster begin to transfer the gas into the fill tank.

If the supply tank pressure is only 500 psi (34 bar) the piston will have to travel 2.1 inches (53 mm) before it can begin to transfer the gas into the fill tank. But in both cases the drive gas consumed will be the same.

To take the situation to the extreme:

The booster will continue to cycle with a supply pressure of only 73 psi (5 bar). At this pressure NO gas will be pumped into the fill tank. But if the fill tank was at 3000 psi (204 bar) the booster would still use 2.9 litres of drive gas per stroke.

Short answer:

“Pretty good, most of the time.”

Long technical answer:

First connect a supply tank to the inlet and a fill tank to the outlet of the booster with suitable high pressure connecting whips. These ports are marked with a letter “I” and “O” stamped on the top of the bronze head of the booster. “I” stands for inlet and “O” stands for outlet. (For some reason this isn’t obvious to everyone.) When the valve on the supply tank is opened (very slowly if it happens to be an oxygen tank) the pressure enters the high pressure cylinder of the booster and pushes the piston to the bottom of it’s stroke. Next open the fill tank cylinder valve (again very slowly if it is an oxygen tank). If there is a line valve on the outlet whip this can now be opened and if the supply tank pressure is higher than the fill tank pressure the line valve can be used to control the rate of gas flow into the fill tank. If the fill tank pressure is higher than the supply tank pressure nothing much will happen at this stage.

The drive gas whip can now be attached to the low pressure fitting on the drive end of the booster.

When the supply tank pressure pushed the piston to it’s bottom position the large drive piston contacted PV-1. This a small “poppet” type valve that lives under the domed head hex plug next to the low pressure fitting. When this valve is opened and the drive gas is turned on (now’s a good time to do this) gas flows through PV-1 to PV-2 (PV-2 is a close relative of PV-1 who lives under a flat hex plug on the other end of the booster.) and SV-1 (the silver block named Humphrey on the end of the booster with the short plastic tube attached to his head) . This gas (signal) tells SV-1 to let the drive gas start pushing the large piston and compressing the gas we are boosting. As soon as the large piston starts to move it lets PV-1 close and traps the “signal” in the line connecting PV-1, PV-2, and SV1. This is the small black plastic tube that goes from SV-1 through the “DO NOT RUN UNTENDED” plate and continues down the right side of the booster to the “JETSAM TECHNOLOGIES LTD.” plate.

When the drive piston gets to the end of it’s stroke it runs into PV-2. When this happens PV-2 vents the signal and SV-1 stops trying to push the piston forward and vents the drive gas through the muffler. (Big white plastic thing on the left side of the booster next to the high pressure cylinder.) With the drive gas vented, the gas from the supply tank starts pushing the piston to the bottom of the stroke again and the cycle starts over.

Since we just finished talking about SV-1, PV-1 and his relative PV-2 let’s start there while we still remember who they are. They are normally a pretty reliable group but eventually everything (and everybody) screws up.

If there is any leakage in the line connecting the three valves or leakage from any of the three small hex plugs near this tube the signal will be lost before the drive piston reaches PV-2, the booster will develop a severe stutter, and it won’t pump any gas. If this happens first check that all of the small hex plugs are snug (don’t tighten them too much or they will strip their threads) and that the small tubing isn’t damaged. If the plugs or tube fittings aren’t leaking the next possibility is that PV-1 or PV-2 are leaking. To determine which one is the problem disconnect the small tube at the “JETSAM” plate. To do this press the red ring towards the fitting and pull the tube out of the fitting at the same time. Fold the tube over to seal it and turn on the drive gas. If the booster still stutters the leak in somewhere in the “DO NOT” plate area or PV-1. If the booster quits stuttering and makes a full compression stroke the problem is in the “JETSAM” plate area or PV-2. By releasing and folding the tube the booster can be made to operate if the problem is in this area. You just took over PV-2's job, and it’s really boring.

While you are doing these tests ignore the plugs, fittings, and tube on the other side of the booster. All they do is carry the exhaust drive gas to the muffler. You could remove all of them and the only difference is that the booster would be a little louder. In fact if the problem is that one of the plugs on the signal circuit is missing this would be a good place to steal one!

If the problem is with either PV-1 or PV-2 refer to the section on stripping the booster.

Whatever you do don’t disassemble the silver block named Humphrey. I’ve tried it several times and they never work again. The good news is that Humphrey is normally good for about a million cycles before he dies.

Next (and more common) problem.

The booster sits there, makes all the right noises but doesn’t fill the tank.

First make sure the leak isn’t in the inlet or outlet whips or on the fill tank valve area. This is a small booster. It doesn’t take a major leak to kill the pumping rate of the booster. A vent screw that isn’t fully sealed will do it.

99% of the time the pumping stops because of something making the reed valves in the high pressure head leak. Of all the things I’ve found in the reed valves most of the time it has been Teflon tape. You can expect this problem any time you have taken the fittings out of the high pressure head or anytime you have resealed any fittings on the whips with Teflon tape. Unfortunately Teflon tape is still the best way to get a leak free seal on the fittings.

You can minimize the problem by cleaning all remnants of Teflon from the threads on the fittings when you remove them and by wrapping the Teflon tape one thread away from the end of the fittings when you reinstall them.

To clean the reed valves first vent any pressure in the booster. It’s a pretty obvious first step but lots of people forget to do it. Then remove the three screws holding the high pressure head using a 3/16 Allen key. You will end up with the three screws, the head, the reed valve, and a valve plate. The head and valve plate both have two o rings each (V75-012) and these o rings face toward the reed valve when the parts are assembled ( just in case you dropped them when you took out the three screws). Carefully wipe off the reed valve and be careful not to bend it. It is very thin. Next check the surfaces of the head and valve plate for damage or debris. (Did they hit the floor when you dropped them?) Normally there will be small particles on the flat surfaces inside the o rings that were holding the valves open. Carefully clean the surfaces and holes of any particles. Don’t scratch the sealing surfaces! When the reed valve, valve plate and head are (oxygen) clean reassemble them with a light film of oxygen compatible grease and reinstall them on the booster. Make sure that the large o ring (V75-020) is still in position on the high pressure cylinder. Unfortunately if there is debris in the supply gas or whip you may have to clean the assembly several times as the particles work their way through the system.

The reed valves are a direct metal to metal seal. They will always leak slightly. To check the leakage rate pump the fill tank to maximum pressure and close the fill tank valve. Close the supply tank valve, vent the supply whip to zero pressure, and close the vent screw on the supply whip. Disconnect the drive gas whip. You should now have the supply whip at zero pressure, the fill whip at near maximum pressure, and no drive gas. The gage on the fill whip will slowly begin to drop as the gas in the fill whip leaks back through the reed valves and flows into the supply whip. With 5' (1.5 m) Swagelock hoses on both the inlet and outlet and air (not helium) in the booster it should take approximately 5 minutes for the pressure to decrease by half. Different length or size of hose will change this rate. If you have a gage on the supply side you can also check for external leaks. If the supply and fill whips are of the same internal volume and there is zero external leakage (this is unlikely) the pressure in the fill whip will drop by 50% of it’s initial reading and stabilize there. After the pressure in the supply and fill whips equalizes any further leakage is from gas escaping from the system.

If the fill and supply hose pressures rapidly equalizes to half of the initial fill hose pressure and then slowly continue to drop the reed valves are leaking but the system does not have significant external leaks.

If the fill and supply hose pressures equalize to a pressure significantly lower than 50% of the initial fill hose pressure and the pressure continues dropping then there is an external leak in the system.

It is normal for the system to leak slightly. A five minute leak down to zero after the supply and fill hose pressures equalize is generally not a problem. There are at least 8 o rings, two vent screws, and approximately 15 pipe fittings in the system and this test is being done with a minute volume of gas.

If there is a significant external leak it is probably somewhere in the fill whips, not the high pressure seal. The high pressure seals have been very reliable. These are the same seals used in the Jetsam electric drive booster. The seals have normally lasted for 4-5 years on the electric boosters.

But if you have to replace the high pressure seal:

First remove the high pressure head, then:

Plan A:

With a piece of plastic push the piston to the bottom of it’s stroke and shake the high pressure bushing out of the front of the booster. Don’t drop it!/p>

It didn’t come out?

Plan B:

Stick your finger in the high pressure bushing and pull it out.

It still didn’t come out?

Plan C:

With the piston pushed to the bottom of it’s stroke connect the drive gas whip and slowly open the tank valve. The piston should move forward and push the high pressure bushing out of the booster far enough that it can be pulled out.

Don’t use any sharp tools to remove or install the high pressure seal. Lift the old seal out of the recess in the end of the high pressure bushing with your finger.

There’s no seal in the recess? It’s probably still on the piston rod. You’ll have to fish it out before reassembling the booster.

Clean out any residue of Christolube. (It starts out white but turns black and gummy after a while.) Inspect the bushing to make sure there are no big gouges in it. Apply a small amount of oxygen compatible grease to the edges of the new seal and place it in the recess with the spring side down. Don’t force it into place. Carefully work the edges of the seal into the recess and make sure the spring expander hasn’t popped out of it’s groove. Apply a small amount of grease to the inside of the bushing and re-install it in the high pressure cylinder.

Or..............

Still stuck eh?

Plan D, complete disassembly of the booster:

First disconnect any gas sources and vent any pressure in the system. Remove the high pressure head and set the parts aside.

If you have to get at PV-1 it is easiest to remove Humphrey first. Otherwise leave him alone. (You remember Humphrey? He’s the one with the tube stuck in his head.) Undo the two screws holding Humphrey to the DO NOT plate. You’ll have to remove the tube by pressing the red collar towards one of the fittings and pulling the tube out of the fitting at the same time. Set Humphrey aside and leave him alone. There is nothing you can do for him other than replace him when he wears out which will take a long time.

Next disconnect the tubes that connect the Jetsam plate to the DO NOT plate. Same procedure as the tube in Humphrey’s head. Now you can remove the four large screws holding the booster together (1/4" Allen key).

After the screws are removed pull the DO NOT plate off, then pull off the composite tube and pull the piston out of the high pressure bore. (If it didn’t already come out with the tube.)

You can now see the four screws that hold the high pressure cylinder to the JETSAM plate. When these four screws are removed the high pressure cylinder can be separated from the JETSAM plate and (finally) you can push the high pressure bushing out of the high pressure cylinder and get at the high pressure seal. The guide bushing can be seen in the front of the JETSAM plate and this can be pushed out and replaced if necessary. The rod wiper is in the back of the JETSAM plate and can be replaced if necessary. Neither of these parts is likely to ever need replacement unless you have been running the booster 24/7 to fill your doubles with 100% 02.

When reassembling the high pressure cylinder note that the cylinder should be positioned so that the two screws on the head end are at the bottom and the single screw is at the top. You won’t damage anything if you don’t do this but the fill whips will end up at some weird positions.

PV-1 and PV-2

You can remove these parts by unscrewing the large hex plugs on the DO NOT and JETSAM plates. There are springs under the plugs so don’t loose them. PV-1 will have to be pushed out of the plate since it has two o rings on it and is tight in the plate. PV-2 will probably fall out since it only has one o ring on it and is loose in the plate. Replacing the o rings is the only thing that can be done for these parts and even these should last many years. To remove the old o rings cut them off of the valve stems and take care not to damage the o ring grooves. The new o rings need to be lightly lubricated and installed on the valves. Make sure the holes that the valves go into are clean. PV-2 will drop into the hole in the JETSAM plate but PV-1 will have to be pushed into the hole in the DO NOT plate since the small o ring is a tight fit in the hole. When the two valves are installed the stem of the valves should protrude about 1mm above the surface of the plates.

The only awkward part of the reassembly is that the large piston has to be inserted into the composite tube from the back and the “V” seal needs to be pushed into the bore without damaging the edge of the seal. When inserting the small diameter of the piston into the high pressure bore gently twist it into the bore until is passes through the high pressure seal. Don’t force it. All of these parts should be lightly lubricated with oxygen compatible grease.

When the piston is in place and the composite tube is located on the JETSAM plate the piston should move easily. If it is tight and cannot be easily pushed with one finger something is binding.

There is a large o ring on the DO NOT plate that seals against the end of the composite tube. Make sure this is in place and undamaged and then fasten the DO NOT plate in position with the four screws. Tighten the screws evenly.