Dialing in a haskel ext-420-2

I am looking to dial in a haskel ext 420-2. What psi is everyone running at? How many cycles per minute? Haskel recommends 60 cycles a minute and around 50-70 psi. Running at this rate the pump sounds like its extremely slow and is taking 2.5-3 hours to recover 20-30 lbs of solvent. We previously ran the ext-420 and got extremely faster run times.

I run mine plumbed single stage with inlet air @120 psi 35 cfm or so. The single stage plumbing makes the pump more air effiecent.

Can you send a photo? And how often do you rebuild?

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No pic on me atm, never had to rebuild these ones. We just changed the plumbing.Instead of the gas going through both stages of the booster, both stages of the booster act like seporate pumps.

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Can you elaborate on this setup more ?

Like this, you may need to remove the check valves from the pump and install them into the ports differently.


If you have a double haskel is it twice the flow still?


For anyone coming across this looking to convert a 59025 (two stage) to an ext-420 (single stage double acting) you don’t have to remove the check valves, just remove the 6 Allen key bolts on the bottom of the gas drive and spin the bottom section 180°. You will need an additional crossover pipe, and a total of two elbows and two tees to tie the inlets and outlets together.


are you rocking the pump in this config?
sure beats the other plumbing in terms of gas moved.

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Yes sir, my current lab has four Haskel EXT-420s plumbed single stage double acting, and they kick ass. I’ve previously run an EX40 with two 420’s in parallel and it would move about .8 - 1lb a minute.

Just rebuilt one yesterday that was in the worst shape I’ve ever seen a Haskel. This was its last rebuild- it’ll be ready for replacement next time it loses its footing…

My favorite config is the -2, switchable with the valve. I’ve used the kit from FLW to mod a 59025 over to a 420-2, that’s how I learned you can just rotate the bottom.


Maybe you guys can help, I’m running two ext-420s and I get a gas leak from one of them, itsgone as high as 16 lel. My coworker set of the alarm off yesterday getting the LEL above 20. You guys think it could just be the Orings/gaskets? Thanks

It is def leaking Send it to flw they will rebuild it for you

Thanks bro, I actually took it apart today and replaced Orings and back stopper. Which was the culprit of the leak, it was busted.

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Gotta set your alarm for much lower than 20%LEL by then it’s too late

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Got a link or a part number for that kit? Looked on FLW’s website and didn’t see it

I’ve noticed this was the reg among c1d1 manufacturers. I question if it has more/less to do with displacement of oxygen. After 8.8%? There is to much gas in the air to ignite. They realistically should turn on anywhere from 2-9% for gas but I think the concern is more so about oxygen as the environment is designed not to ignite.

Your 8.8% that you’re referring to, would be 88% on the sensor. I believe, may be wrong. But, I think that the 100% in the booth is 10% lel. I think.