“Hydrocarbon gas detectors are required by local legislation,” commented Crowcon’s Indian distributor, Mr Kishore Degwekar of Detection Instruments Pvt. Ltd. “Our customer Larsen and Toubro, purchased the Nimbus detectors as they are certified by the Indian Directorate General of Mines Safety”.

Crowcon’s Nimbus gas detectors have an excellent 10-year proven track record and, as well as having local certification, are also ATEX and UL certified. The detector is also assessed to the globally recognised functional safety standard IEC61508 and is suitable for use as part of SIL 2 systems.

Many thousands of Nimbus detectors are installed in locations across the globe, in all climatic conditions, such as the north of Sweden with its sub-zero winters, the deserts of Qatar, where summer temperatures can exceed 50oC and where sandstorms are common, and hot and very humid regions such as Malaysia.

It is used in all manner of locations, including underground tunnels, oil and gas rigs, oil and gas refineries, over-ground pipelines, compressor stations, turbine halls, pumping stations, sewage works, chemical works, aerosol filling plants, floating production ships (FPSO’s) and power stations.

Designed to be integrated with existing gas detection systems, Nimbus can be used in conjunction with digital communication networks (via RS-485 Modbus) or conventional 4-20mA control systems such as Crowcon’s Gasmonitor.

Rated to IP67, Nimbus functions in even the dirtiest conditions. The optics operate at up to 90% obscuration, with a dirty optics warning light activating at 75% obscuration. An external status light indicates whether the unit is in normal function or fault, alerts users to rising gas levels, and also identifies 22 further conditions for simple diagnosis.

About Cairn Energy’s Mangala oil processing terminal

The Mangala processing terminal covers an area equivalent to 200 football pitches and includes oil, gas, power and water infrastructure. At an eventual length of 670 km, the pipeline will provide access to more than 75% of India’s refining capacity. At the peak of construction, approximately 16,000 workers were involved: 5,000 on the pipeline and 11,000 on the processing terminal.

As recently reported in the national news, a four-mile exclusion zone has been set up around the Elgin Total platform in the North Sea and workers have been evacuated due to an explosive gas cloud.

Explosive hazards from hydrocarbon gases and vapours are an ever-present risk, whilst toxic hydrogen sulphide gas and depleted oxygen environments can pose significant risks to personnel. Gas detectors are therefore essential to provide dependable early warning of gas hazards. They are permanently installed in strategic locations around fixed installations and as many as 700 may be installed on a single offshore platform.

Communication Technology on
Offshore Rigs

On a rig, gas detectors are connected to a centralised control system, which is responsible for indicating the current gas level and triggering alarms at pre-defined thresholds. Gas detectors will typically be located within the hazardous area, with the control system mounted in the ‘safe area’ potentially hundreds of metres from the detectors.

Detectors are typically connected to the control system via cables, using ‘point-to-point’ topologies where each detector connects to a discreet input on the control system via an independent cable (or separate cores within a multi-core cable from a ‘marshalling cabinet’).

This conventional ‘point-to-point’ method of operation has been the preferred technique for decades for signal reliability and system security reasons. With a dedicated cable and controller input for each detector, a single failure will affect that specific detector only: the rest of the system can remain operational.

Point-to-point systems typically utilise analogue signals from the detector to indicate the gas level. Analogue signals however can only communicate a limited amount of information from the detector, typically: gas value (4-20mA), fault (<3mA), gas reading over-scale (>21.5mA).

New Technologies

The emergence of new technologies has enabled a far greater range of information to be communicated to a control system, as well as providing opportunities to reduce the amount of cables needed to connect detectors. Three of the most well known of these are HART, Modbus and Fieldbus.

The HART Communications Protocol (www.hartcomm.org) complements conventional 4-20mA systems by super-imposing additional diagnostic information onto the 4-20mA signal. This data can be read using a HART enabled hand-held device or Asset Management System (AMS) to diagnose faults and manage system calibration and maintenance.

Developed by Modicon Inc, the Modbus protocol has been in existence since the early-1990s and is an address-based protocol whereby each ‘node’ or gas detector in this case is communicated with using a unique address. Information such as gas level, alarm and fault status is stored in registers within the detector, and the ‘Modbus Master’ control system routinely addresses individual detector ‘nodes’ to retrieve data. A full guide to Modbus can be downloaded from www.modbus.org/docs/PI_MBUS_300.pdf.

Like the HART Communications Protocol, Modbus can be used in conjunction with the analogue signal to provide additional detector information, or can be used as the primary means of communication with a control system such as a PLC (Programmable Logic Controller) or SCADA (Supervisory Control and Data Acquisition) system.

Foundation Fieldbus (FF) is a well-established solution widely used for process instruments, but as ever the safety industry is slower to change from established and trusted systems and practices. FF provides the opportunity to use alternative cabling interfaces: data can be transferred via conventional copper cables or fibre-optic cables. Data can also be transferred via Intrinsically Safe (I.S.) interfaces. For more information visit www.fieldbus.org.

All of the communications technologies listed above enable detectors to be installed in an addressable cable configuration rather than the conventional point-to-point topology. Thus cable installation costs can be significantly reduced by connecting multiple detectors onto a single cable where the cable loops from one detector to the next. The cost of control equipment can also be significantly reduced as a single controller can communicate with a fleet of detectors (addressing each detector ‘node’ individually on a sequential basis).

As we look forward, wireless communications seem a very attractive proposition where running additional cables to new or additional detectors is impractical. Detectors may be powered locally (via cables, batteries or solar panels), and transmit the gas levels and status information to a control system via a radio signal. Although wireless products are available on the market, a global ‘standard’ for the protocol and frequency deployed has yet to be established and therefore suitability will depend on local regulations in the region in which the device is to be used.

Installing wireless devices also requires very careful consideration to the characteristics of each detector location to ensure guaranteed signal integrity and security. In practice, at present wireless devices are viable mainly where they are needed for temporary area monitoring or where gas detection is needed in a location where installing a conventional cabled detector is impractical.

The majority of gas detection systems on offshore installations continue to use conventional 4-20mA point-to-point systems. For established platforms where safety systems are already installed there are no installation savings to be made by using addressable systems as the assets are already in-place. There is however an option to replace older gas detectors with HART enabled devices to realise the benefits of access to additional diagnostic data for asset management purposes.

For new installations, communications technologies such as Foundation Fieldbus may provide a better overall solution to conventional analogue systems, but as always the individual safety case assessment is the critical determining factor.

Crowcon offers a very wide range of both fixed and portable gas detectors for use on installations such as offshore platforms and can provide advice on overcoming challenges faced.

When choosing flammable gas detectors, users want them to withstand the most rigorous conditions, prevent signal faults and welcome any other obstacles that the instrument may face.

IRmax is an ultra-compact, dual-wavelength, infrared (IR) flammable gas detector which delivers rapid, fail-safe detection of methane gas and other potentially explosive hydrocarbons in the harshest environments. Crowcon’s third generation of IR detector platform, and building on their 15 years of experience with the technology, IRmax also features an important innovation to reduce power consumption and maintenance.

Unlike conventional IR gas detectors, IRmax does not utilise heaters to prevent condensation on windows and mirrors. Instead, its optical components are treated with a highly durable hydrophobic coating called STAY-CLIR that completely prevents signal faults due to condensation.

IR type gas detectors detect tiny reductions in transmitted infrared light due to absorption by hydrocarbon gases. It is essential that the light path of the detector is not obscured by condensation or dirt to ensure dependable hazard detection. Conventionally, the windows and mirrors in IR detectors are heated to prevent condensation forming. Although an effective solution, heating components require significant amounts of power to operate and can result in the build-up of dissolved deposits (such as salt).

As IRmax contains no heating components, power consumption is dramatically reduced. It requires less than 1 Watt of power, typically 75-90% lower than conventional IR gas detectors. A gas detection system using IRmax detectors therefore requires smaller (and lower cost) power supplies and battery back-up systems. Longer cables can also be used and more detectors can be powered on addressable networks.

A further benefit of the STAY-CLIR coating is resistance to contamination from dirt and dust, eliminating routine cleaning of the optical components.

Detailed research and development undertaken by Crowcon’s scientists resulted in a highly durable coating that was proven by being subjected to aggressive corrosion and resilience tests in extreme locations such as the Australian desert and the north coast of Scotland.

Following Cirrus and Nimbus, IRmax has now been continually in use on petrochemical sites from the North Sea to Singapore since September 2009, providing ‘real world’ evidence of the effectiveness and durability of the STAY-CLIR coating.

Crowcon will be showcasing IRmax as well as their existing range of gas detection products at the Safety and Health Expo from 15th to 17th May 2012 at the NEC in Birmingham, UK. You can find Crowcon in Hall 1, stand number F80.

The parent group of Crowcon, £520m Halma PLC is a group of companies that produce specialist products used to protect lives, or improve the quality of life, for individuals and businesses worldwide.

The Halma Operations Network has been running for 4 years and consists of the Operations Directors from each of the three Halma divisions (Health and Analysis, Infrastructure Sensors, and Industrial Safety) as well as being sponsored by a Divisional Chief Executive. The network was established so the operations divisions within the Halma Group are able to get together to share experiences, ideas and to visit each other’s premises to gain an understanding of their business structure.

In February the Operations Directors visited Crowcon UK headquarters where Stuart Woodward, Crowcon’s Operations Director and newly appointed Facilitator of the Ops Network, and his team took them on a tour of the premises as well as detailing for them Crowcon’s Operational Excellence Programme, Customer Centric Project, Business Process Mapping and Showroom Manufacturing.

“I’m extremely proud of the reaction from my peers in Halma to the progress we’ve made in our Operations and our Showroom manufacturing facility. We are now perceived to be one of the leading lights in Halma and that is something for which every one of us can take great pride. The whole day went very well and many Operations Directors from across Halma spoke to me about how impressed they were with the professionalism and enthusiasm they found from everyone they have spoken to at Crowcon during the day. The key thing now is that we don’t rest on our laurels but continue to work together towards attaining Crowcon Excellence and improving our customer satisfaction.”
Stuart Woodward, Operations Director, Crowcon

Examples of comments received were:

“The Crowcon team has been very professional and well prepared for this meeting and it was really impressive what you have achieved so far through your Crowcon operational Excellence Programme.”
Thomas Holle – Operations, Reister

“Stuart, I would just like to take this opportunity to thank you and your team for the hospitality and professional presentations. You have an excellent operations team around you which I am sure will help you to continue to improve as you move forward with Crowcon Excellence. If you could bottle the enthusiasm your team possess I’d take it and pour it over my supervisors!”
John Fulton – Operations, Elfab

“A very impressive transformation, showing that lean thinking aligned to motivated teams can make real changes…well done.”
Russell Trotter, Operations, Texecom Ltd

Crowcon have created a video giving more information on the successful structure and working ethics of the Operations department. You can view the video here

Industry members will come together at the only show with support from the key industry partners – IOSH (Institute of Safety and Health), RoSPA (Royal Society for the Prevention of Accidents) and BSIF (British Safety Industry Federation).

Crowcon regularly exhibit at this major show and has seen steady growth in footfall as well as brand exposure and recognition in the industry.

This year Crowcon will be showcasing its Gas-Pro portable gas detector which is specifically designed for confined space workers and +ve Safety – an innovative, tri-colour status indicator flexible enough to fit differing regulations.

Since its initial launch the number of gases detectable by the Gas-Pro has grown and now includes common hazardous gases in the water, construction and manufacturing industries, including H2-filtered carbon monoxide, ammonia, sulphur dioxide, ozone, nitrogen dioxide and chlorine.

Crowcon will also be presenting a number of other new gas detection products, including the IRmax infrared (IR) hydrocarbon fixed gas detector and a wider range of test stations.

All these products, as well as Crowcon’s existing range of state-of-the-art gas detection products, can be found in Hall 1, stand number F80. Crowcon’s experts will also be on hand to answer any gas-safety related questions.