What is Surface Supplied diving?
All offshore air diving work and a large percentage of inshore diving work takes place using surface supplied diving gear. In this post we explain how it works.
Whether you’re an experienced diver or have never been in the water at all, you’ll know that the fundamental purpose of diving gear is to let you breathe and keep you alive under the water. When diving using SCUBA (Self Contained Underwater Breathing Apparatus) your air is with you while you dive and you have a finite amount of air, which means a finite amount of time that you can be underneath the water. With surface supplied, as the name suggests, your air is supplied to your diving helmet via a hose to the surface. The result of this is that you can get on with whatever job you’re under the water to do, and someone on the surface will be monitoring and looking after everything you need to stay alive and comfortable. You can stay in the water as long as necessary (within decompression limits of course.)
How surface supplied diving works
Air is sent to the diver from the surface using either a low-pressure or high-pressure system. Most commercial operations use a low-pressure compressor to supply breathing air for their divers. This method is very reliable but can be expensive to run and noisy. High-pressure systems take the form of high-pressure cylinders, generally filled off-site and transported to the site of the dive operations.
Surface supplied divers do carry a cylinder of air on their dive vest, which is also connected to their diving helmet. This is referred to as a ‘bail-out’, for perhaps obvious reasons! In the extremely rare event that the surface supplied air should fail, the diver always has an emergency supply.
The hose from the surface to the diver is referred to as the ‘umbilical’. The umbilical is typically made up of three hoses. One, as mentioned, is for air, one carries communications between the diver and the surface and the other is the pneumofathometer, or depth gauge, which tells the Dive Supervisor what depth the diver is at, at all times. The ‘pneumo’ can also be used as a back-up air supply in non-contaminated water situations. Communications are via a mic and speaker inside the diver’s helmet.
Surface supplied equipment
The Dive Supervisor uses a Dive Panel on the surface to monitor and communicate with the diver. The dive panel contains gauges which allow the supervisor to monitor and adjust air supplies. The Dive Supervisor also has control over the information between the diver and other members of the team.
There are a number of manufacturers of diving helmet used for surface supplied diving, however Kirby Morgan helmets (worn by the divers in the picture above) are the main helmets used by the diving industry worldwide. Kirby Morgan supply a range of models. The helmet is provided by the diving contractor, unless you are in America where the tradition is for each diver to have his own helmet.
Wet bell diving
When diving offshore, divers are transported to and from the dive work site in a ‘wet bell’. The wet bell (pictured right) has its own umbilical which is connected to the panel and a low-pressure surface air supply. The bell also has its own high-pressure supply in the form of cylinders on the side of the bell. The diver’s umbilicals are connected to the wet bell itself. The primary purpose of the high-pressure cylinders are as a back-up air supply for the divers. The benefit of diving from a wet bell is that the divers place of safety is closer, as well as keeping the diver’s umbilical away from the ships propellers and thrusters. The structure of the bell itself also protects the divers as they are travelling to and from the dive site.
HSE Surface Supplied divers are qualified to dive to 50metres depth; beyond that saturation divers are used. Look out for a future post explaining how saturation diving works.
Do you have any other questions about surface supplied diving? What experiences have you had using surface supplied equipment? Leave us a comment and let us know