Guidance Note No: IMCA D 021
The information contained herein is given for guidance only and endeavours to reflect best industry practice.
For the avoidance of doubt no legal liability shall attach to any guidance and/or recommendation and/or statement herein contained.
Diving Near Potentially Contaminated Locations
This guidanceaddresses specific safety precautions to enable divers to perform work safely in potentially contaminated locations such as on or near operational pipelines containing hydrocarbon or chemical products, and in areas contaminated by hydrocarbons or chemicals.
It covers both saturation and surface supplied diving.
The safety of diving personnel should be addressed by the application of the following:□ An adequate Safety Management System
□ Hazard identification and risk assessment
□ Provision of working procedures approved by relevant parties as defined within the Safety Management System
□ Adequate briefings prior to commencement of diving operations
The precautions mentioned in the following sections provide guidance for the responsible company to consider and are not meant toreplace any specific requirements identified for a particular task to be undertaken.
1 Known Hazards
Chemicals can be present underwater in oil, gas and chemical pipelines and in contaminated areas.
Special ‘muds’ are used in drilling, which are chemically complex. Even at a single site their composition will have changed over the years they have been in use.The ‘cuttings’ with adhered mud produced from the drilling process have in the main been left on the seabed. Since production drilling is virtually a continuous process, with many wells sunk at different depths and into different areas of any given field, some production platforms are surrounded by large amounts of oil based mud cuttings, of different age and composition.
Chemicals andpetroleum products underwater can be present in the form of gases, liquids or solids.
Gas Gases (if not dissolved) may appear in the form of bubbles in the water, but will usually be invisible in a diving bell atmosphere
Liquids Some liquids can be detected by their colour, some that dissolve in water are described as appearing to ‘shimmer’ in the water, and some will be invisible.They can be encountered underwater will be at varying levels of dilution. Condensate is a liquid that can pose particular problems. It contains constituents which are liquids under pressure, but gases at atmospheric pressure. Changes in pressure or temperature can cause these volatile components to evaporate.
Solids Solids can range in consistency from hard to soft.
2 ContaminationDivers and their equipment can become contaminated through two main routes.
1 Direct Contact
When wearing hot water suits, divers’ skin is permanently bathed by warm seawater. This has the effect of softening the skin and making it more susceptible to damage.
Direct contact of the skin by many chemicals or petroleum products can cause irritation or burning tooccur. When divers operate in areas where drill mud /cuttings deposits or liquid contaminants exist, because hot water suits and boots are not water tight, mud and /or liquids can often find its way between the hot water suit, helmet and boots, thus coming into contact with the divers’ skin. Some chemicals can also leach through the material of the suit. Some drill mud additives are, or canbecome, caustic.
Chemicals, petroleum products or drill muds and cuttings can impregnate or attach themselves to divers suits, oversuits, helmets, tools or umbilicals. In some cases these can remain trapped within the umbilical bundle and low molecular weight contaminants have been known to pass through the umbilical and affect the diver.
2 Contamination of the Diving Bell...