The Bends, also known as Caisson Disease and decompression sickness, is one of the safety hazards when underwater welding. It is caused by dissolved gas, the majority of which is nitrogen, that comes out as bubbles during decompression. If you rise too quickly, these bubbles don’t have time to be reabsorbed into the body, and then they get trapped, causing problems. It can affect any part of the body and can be serious, if not fatal.
Proper decompression prevention is essential when you are welding underwater.
When you are rising to the surface, you need to make sure that you remain at specific depth till sufficient gas has left the body, so as not to cause issues. Each ascent rise is known as a decompression stop.
You should use a diver’s watch to time these properly. If you are diving at 20 feet, you may be able to dive for several hours, without the need for ascending with decompression stops. At depths that are greater than 130 feet, you may only have as little as a few minutes for the job, then decompression stops will be needed on the way up.
Using Dive Tables
Dive tables were originally used by the US Navy. They clearly show the amount of nitrogen that is residual in your body using different letter allocations. If you have spent a reasonable time on the surface between dives, where you offgas the nitrogen, you will be allocated a lower letter.
When you dive again, you need to use your letter to calculate how much nitrogen you have in your body. This will tell you how long you can dive for and the decompression stops that you will need. If you are diving with other people, make sure that you all use the same dive table calculations. It will help prevent any accidents whilst you are working.
There are computer programs and apps such as Dive Planner available to also help you calculate your decompression stops.
What dive tables won’t calculate
Diving is unpredictable, and there are some things that dive tables won’t be able to calculate – and the biggest risk is drinking alcohol before diving. Your dive table doesn’t know that you’ve been to a party the night before – it just assumes you are stone cold sober.
40% of drownings are actually alcohol related. Even drinking moderate amounts of alcohol the night before can affect your ability to calculate the decompression stops needed.
Using diving equipment when water welding is part of the job.
You need to take the utmost care and attention to ensure that you don’t get the bends whilst working.