Underwater Reciprocating Saw

[Aquanomad]

Hi all,
I'm looking at using a pneumatic reciprocating saw underwater. Anyone done this? Is there a depth limitation or do I just need to properly set the IP? The saw runs at 90psi so as I understand it I will need an IP equivalent to depth plus 90psi. So 100' would require 59psi + 90psi for a 149psi total? I planned on using an air integrated computer with an Lp to Hp adapter to fit the hose. Then adjust the IP based on working depth. Any reason this wont work? Thoughts?

 

[redacted]

What do you plan to use for an air source? Some pneumatic tools are pretty "heavy breathers". What will you use for a regulator?

 

[Aquanomad]

I bought a saw that only uses .7cfm and found it accurate at the surface. I have a few 130s to pack the most time I can comfortably sling. I use Poseidon Xstreams but am considering a dedicated first stage that can handle high IPs.
Also curious about how accurate readings are with AI computers. I plan to go with a hosed version but need a 10psi margin for error. I would be happy with an analog Ip gauge but an underwater version does not seem to exist.

 

[dumpsterDiver]

I've used some pneumatic tools underwater, primarily a chisel. I used a separate dedicated tank, I would not tap into my air supply - unless the depth was trivial. i found that the use of a longer hose, maybe 8 ft or so, helped to act as an air pressure reservoir and allowed the tool to work well in bursts.

I didn't mess with the air pressure coming off the scuba regulator. I chopped the end off a normal LP hose from a second stage, inserted 3 inches of a 6 inch piece of stainless tubing in the hose and hose clamped it and then added electrical tape to the other end and inserted that into a cheap pneumatic tool hose (had a larger ID if I recall) which had the quick disconnect on the other end. A few more hose clamps and the splice seemed to work, but not somehting I would want connected to my breathing supply.

I don't think you need to make any adjustments to the supply pressure for different operating depths, because the scuba first stage does that automatically

 

[Aquanomad]

Bottle is strictly for cutting. Not my air source. Doesnt even have a second stage. Its plumbed with a lp hose that has a npt end fitted to a quick connect. Same on the saw side. Added an inline shut off as well. I thought adjusting the ip to the saws requirements would work as well but no go. Took it to 286' and didnt even budge. Was told I needed to take the psi at depth and add the tools required psi to make it work. Confused?

 

[redacted]

Bottle is strictly for cutting. Not my air source. Doesnt even have a second stage. Its plumbed with a lp hose that has a npt end fitted to a quick connect. Same on the saw side. Added an inline shut off as well. I thought adjusting the ip to the saws requirements would work as well but no go. Took it to 286' and didnt even budge. Was told I needed to take the psi at depth and add the tools required psi to make it work. Confused?

A scuba 1st stage will take care of the IP adjustment unless the saw is also compensating somehow. But you may have to play around a bit to get 90 psi from a scuba 1st. I tried lowering the output from a Mk10 by inserting shims between the seat and the seat carrier but don't remember h0ow low I got it before it would not function. I'm sure you could modify the spring a bit to get it to work. How much range do you have in the supply pressure spec? What were you using for a regulator at 286 ft?

 

[dumpsterDiver]

Does it work off the regulator at the surface? Does it work at 100 ft? I am confused why it would not work unless maybe it got some kind of vaccum during the descent? I would think that if it works at 90 psi on the surface it should also work at the normal IP pressure of 125 too?

 

[Jack Hammer]

You need more drive pressure at depth to compensate for water resistance and added ambient pressure. Then some tools (type, brand, model) don't work as well as others

 

[arcticat99]

why not just use a electric one salt water and electricity are best friends .its a joke ill shut up now

 

[Aquanomad]

It works fine at the surface. I detuned my Xstream and it held 90psi no problem. 125 is too much and not advised by the manufacturer. I figured I needed more drive pressure and thus the math in the initial post. I will tune it to 149psi and take it to 100' to test again.