noddybrian
- noddybrian
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Weldmonger
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Posts:
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Joined:Thu Jan 24, 2013 12:13 pm
Welcome to the forum stapleto.
I've cut a bit underwater with a torch though it's mostly been thermic lance or oxyarc - a dedicated torch uses 3lines with the extra one supplying compressed air to an extra annular ring of holes surrounding the heating ones creating in effect an air bubble in which the flame exists - it's not usual to use acetylene as it would be limited to a few feet depth as it's not possible / safe to supply enough pressure to overcome the water pressure - hydrogen was often used - if this is a one off you could likely improvise the air jet ring with a little ingenuity & add it on to your torch - not sure what depth you need to work at though - I will say the simplest of jobs once you have to do them underwater is a major PITA - I'm curious as to what kind of " sea wall " is only 3/16" thickness - if it really is only that thick the cheapest option is to use a regular air powered grinder with a cutting wheel on - these will work just fine in water ( though pipe the exhaust a few feet away behind you ) I use common air tools regularly underwater no problem - a more powerful alternative is a hydraulic drive disc saw on a small power pack ( like you get with concrete breakers ) - you can rent them - just don't tell them where your using it ! you can also buy these days what is referred to as " micro lance " - which looks a bit like coax cable - comes on a roll - you need a fitting to connect the end of the roll to your oxygen supply & it's lit & used just like a regular lance - the fire service often keep it on their trucks to cut things too solid for the " jaws of life " to cut through - another random thought I once had to cut off a load of old sheet piles along a jetty & by picking a suitable tide we had time do dig a trench alongside them - built up a bund of shingle surrounding this & with a big pump drained the water level in that isolated area low enough to use a regular torch - so there are options.
I've cut a bit underwater with a torch though it's mostly been thermic lance or oxyarc - a dedicated torch uses 3lines with the extra one supplying compressed air to an extra annular ring of holes surrounding the heating ones creating in effect an air bubble in which the flame exists - it's not usual to use acetylene as it would be limited to a few feet depth as it's not possible / safe to supply enough pressure to overcome the water pressure - hydrogen was often used - if this is a one off you could likely improvise the air jet ring with a little ingenuity & add it on to your torch - not sure what depth you need to work at though - I will say the simplest of jobs once you have to do them underwater is a major PITA - I'm curious as to what kind of " sea wall " is only 3/16" thickness - if it really is only that thick the cheapest option is to use a regular air powered grinder with a cutting wheel on - these will work just fine in water ( though pipe the exhaust a few feet away behind you ) I use common air tools regularly underwater no problem - a more powerful alternative is a hydraulic drive disc saw on a small power pack ( like you get with concrete breakers ) - you can rent them - just don't tell them where your using it ! you can also buy these days what is referred to as " micro lance " - which looks a bit like coax cable - comes on a roll - you need a fitting to connect the end of the roll to your oxygen supply & it's lit & used just like a regular lance - the fire service often keep it on their trucks to cut things too solid for the " jaws of life " to cut through - another random thought I once had to cut off a load of old sheet piles along a jetty & by picking a suitable tide we had time do dig a trench alongside them - built up a bund of shingle surrounding this & with a big pump drained the water level in that isolated area low enough to use a regular torch - so there are options.