Underwater Magazine -September/October 2013 - (Page 43)

gas Diver Gas Management in the Bell THE SAFETY AND SECURITY OF gas supply to a diver is of paramount importance to any operator sustaining life underwater. This is perhaps nowhere more important than in closed bell / saturation diving. With divers operating in a cold, dark environment, sometimes over 1000ft beneath dive control, it’s imperative that the correct equipment is used to manage the gas to the diver. In the mid to late seventies, a number of incidents took place where divers working from a closed bell lost their primary gas supply. In some of these instances, it was discovered that given the design of the gas supply panels, the failure of one diver’s umbilical or supply pipework severely endangered the other diver. In the worst case, a single failure removed the gas supply to both divers. In 1976 an initial requirement was put in place that required each diver’s gas supply to be set up in such a way that if one supply line or umbilical failed, it would not interfere with another diver’s supply. This requirement was repeated by the UK Department of Energy’s Diving Safety Memo 10/1983 with the AODC later issuing a formal guidance note AODC 028 - Divers’ Gas Supply. At around the same time as the regulatory bodies were advising the industry on these very important requirements a UK based firm (Mara Engineering Ltd) was working on changing the industry. Derek Clarke, now Divex Joint Managing Director, filed a US patent (4,739,790) on the design of a shuttle block to automate and isolate gas supplies in an emergency. The incorporation of this shuttle block into a panel went onto become what is commonly known in the industry as the “Mara Panel”. A common site in diving bells the world over, the Mara Bell Gas Management Panel centralizes all of the bell gas control requirements into a single assembly. Aberdeen-based Divex, having acquired Mara Engineering, have continued to manufacture and supply the Mara Panel globally ever since. The shuttle system is “energized” via a pressure bias between the various supply regulators. If loss of the surface supply gas, or excessive demand occurs, as would happen with a ruptured diver umbilical, the pressure from the surface supply regulator drops below the 30 psi bias, the upper valve of the shuttle assembly closes and the lower valve opens as the emergency regulators take over. In addition to the shuttle block providing automatic switching and isolation functions, it provides visual feedback to the Bellman via indicators on the panel. These indicators, mechanically interconnected with the shuttle block, give a visual display as to whether surface gas or emergency gas supplies are being used by the divers. A green display indicates normal surface gas while a red display indicates emergency gas. A number of other saturation diving system designers and manufacturers, along with operators have attempted to recreate the automatic operation of the Mara Panel with limited success. It must be noted that the Mara Panel is not the only approach to safely protect and isolate the gas supply to the divers. Additional methods include the use of flow fuses and/or totally separate supply systems (from separate sources). The most important principal that is often overlooked is that no matter which solution is chosen, there should be no human intervention in either the gas supply switch or isolation in the case of an emergency. At Underwater Intervention 2012, held in New Orleans, California-based SURFACESUPPLIED, Inc. launched their latest product offering - a Bell Gas Management Panel with remote LCD display. SURFACESUPPLIED’s TRITON Bell Gas Management Panel also provides operators with the ability to remotely monitor the status and operation on the surface. Utilizing a combination of solid state surface-mount electronics and piezo-resistive pressure sensors, the diving supervisor is able to see the status of a number of parameters from the panel. This includes the line pressure of both divers in the water, plus the Bellman along with the location of each valve on the panel. The data stream is transmitted to the dive control station via one twisted pair utilizing Heliox Technologies’ proprietary communications protocol subseaIP. Once the data stream has reached the surface station it is displayed on a 7-inch www.adc-int.org ■ www.underwatermagazine.com UnderWater 43 http://www.adc-int.org http://www.underwatermagazine.com

Table of Contents for the Digital Edition of Underwater Magazine -September/October 2013

Board of Directors
President’s Message
Executive Director’s Message
Jascon 4 Rescue
Croc Country
Saturation Diving and Microbes
Commercial Diver Training Requirements
Emergency Repair at Sewerage Plant
California High Schools Prevail in International Student Underwater Robotics Competition
Revolutionary PileJax™
Safety and Efficiency through Automation
Diver Gas Management in the Bell
Unique System LLC (USA) Completes the Upgrade to the Ranger Offshore, Inc. HOSS-1, 6-Man SAT System
New Gear
Underwater Intervention 2014
New ADCI Members
Index to Advertisers
2014 ADCI Scholarship Fund Raffle

Underwater Magazine -September/October 2013

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