In this blog post we look at what hydrocarbons are, how they are dangerous and how the Hyper-Gas MKII monitor can keep divers safe.
Hydrocarbons are an organic compound consisting of hydrogen and carbon atoms, and they are commonly given off by the vaporisation of crude oil and condensate.
Exposure to hydrocarbons can cause health effects such as asphyxiation and narcosis. Where divers are working on dirty sites, there is a likelihood for contamination of the bell atmosphere from vapourisation of hydrocarbons carried on dive suits and umbilical lines, even when divers are wearing additional safety diver suits.
Only a small quantity of hydrocarbons is enough to set off gas in the bell atmosphere and act as an anaesthetic, which could prove potentially fatal for divers if they are not made aware so that they can take evasive action.
An incident in the North Sea
In 1997, the North Sea industry became concerned about the safety of divers, following an incident where two divers showed signs of becoming anaesthetised after their diving bell became contaminated by volatile hydrocarbons.
The hydrocarbons were derived from a condensate pipeline and accidentally brought back to the bell from the seabed by one of the divers.
Luckily they realised something was wrong and managed to flush the bell before being put onto breathing apparatus and making a full recovery.
In the presence of anaesthetic levels of volatiles divers can suffer the effects within a few breaths.
Even in the presence of sub anaesthetic levels, divers will still be affected, and the effects can be compared with the pattern of behaviour caused by alcohol consumption.
The following effects have been detailed for different hydrocarbons:
- 33% of the anaesthetic level of toulene leads to hyperactivity
- 13% of the anaesthetic level of xylene causes tremors which could impair purposeful actions
- 44% of the anaesthetic level of benzene causes uncontrolled jerking of limbs
- 52% of the anaesthetic level of cyclo-hexane causes convulsions
In response to the need for hydrocarbon monitoring, Analox designed a unique hyperbaric hydrocarbon monitor for use in saturation diving.
The Hyper-Gas MkII – monitoring hydrocarbons in commercial diving
The Hyper-Gas MkII comprises a bell monitor which is located inside the diving bell and measures its total hydrocarbon content. This information is transferred to a topside repeater inside the dive control area for the dive control team to see.
It can monitor hydrocarbon gases in diving bells at depths down to 600 metres, and is set to alarm at 10% of the amount of hydrocarbons required to cause anaesthesia. Both units are powered by a 24V DC supply and they are connected together via the dive bell umbilical for communications
The Hyper-Gas MkII is now mandated by The Association of Oil & Gas Producers (OGP) in their “411 Report” which means that any diving contractor working for an OGP member such as Shell, BP, Total or Chevron must have a Hyper-Gas MkII installed in their saturation diving system.
The unit is now used in the majority of operational diving bells and recognised as the accepted best industry practice.
Author: Araminta Hartley
Founded in 1981, Analox Sensor Technology provides niche and custom gas detection solutions to industries including beverage and fast food, commercial diving and laboratories. Analox has over 325 years of collective, specialist electronics and software engineering expertise, as well as a worldwide distributor network. Contact us to see how we can provide expert gas monitoring solutions and help you achieve your goals.