Wireless gas detection total system

Yokogawa has announced that the ProSafe-RS SIL2 Wireless Gas Detection System will be released in September 2017. This will offer a total flammable gas detection system solution, using ISA100 wireless communications, and Yokogawa will include the necessary  consulting and engineering.

The ProSafe-RS SIL2 wireless gas detection system will consist of a newly enhanced version of the Yokogawa ProSafe-RS SIL3 safety instrumented system (R4.03.10), Yokogawa field wireless network devices, annunciator panels, and GasSecure (a subsidiary of Drägerwerk AG) wireless gas detectors GS01 or the GS01-EA (this model is equipped with an extension antenna).

For this system, Yokogawa will establish a total solution that will include both consulting and engineering.

Development Background

In energy and basic materials industries such as oil & gas, petrochemicals and chemicals, a safety instrumented system is employed to safely initiate an emergency plant shutdown when a critical failure is detected, and to initiate the operation of facilities that can extinguish or prevent the spread of a fire.

A field wireless system consists of field devices that are able to communicate wirelessly with a monitoring and control system. Wireless devices have a number of advantages such as allowing installation in difficult-to-access locations and the reduction of installation costs, and they are increasingly seen as essential elements in plant safety solutions. This is a particularly important consideration with gas detection systems, as operation can easily be impacted by factors such as installation location and ambient conditions. And even after system installation, ongoing efforts to optimise its overall configuration may necessitate occasional changes in the location and number of detection devices. The use of wireless technology eliminates the need to worry about wiring and thus greatly facilitates the process of moving and/or installing additional detection devices.

To achieve SIL2 level risk reduction when using wireless gas detectors with a safety instrumented system, communication protocols that comply with the functional safety requirements specified in the IEC 61508 international standard are required. A standard for the functional safety of electrical/electronic/programmable safety-related systems. To meet this need, Yokogawa will provide a SIL2 wireless gas detection system based on a new version of the ProSafe-RS safety instrumented system that will link to field devices using an IEC 61508 compliant communication protocol.

Features of the System

The ProSafe-RS SIL2 wireless gas detection system will consist of a new version of the ProSafe-RS safety instrumented system, R4.03.10, that will be enhanced to add support for an IEC 61508 compliant safety communication technology used in distributed automation; annunciator panels; ISA100 Wireless compliant field wireless devices; and GasSecure GS01 or GS01-EA wireless gas detectors, which are the only devices of this type in the industry that achieve SIL2 risk reduction. The ISA100 Wireless network protocol is based on the ISA100.11a wireless communication standard for industrial automation that was developed by the International Society of Automation (ISA), and the applications necessary for its implementation. This was approved as the IEC 62734 international standard in October 2014.

Total system solution including both consulting and engineering

Through the use of wireless technology, the ProSafe-RS SIL2 wireless gas detection system will allow increased flexibility with the configuration of detection devices, and will be suitable for use as a fire & gas system and emergency shutdown system thanks to its achievement of SIL2 risk reduction. Based on its knowledge of each of this system’s components and its expertise in production control, safety instrumentation, and field wireless engineering and consulting, Yokogawa will be able to offer a total system solution that includes customer support.

Enhanced operating efficiency

On their Yokogawa CENTUM VP integrated production control system screens, operators will be able to easily monitor the operation of the ProSafe-RS SIL2 wireless gas detection system as well as that of any conventional wired gas detection system. Since the GasSecure GS01 or GS01-EA wireless gas detector uses the same faceplate as a wired gas detector, operators will have no trouble identifying any changes in the detector’s status, thus helping to prevent errors that can result from the misinterpretation of information.

 Improved maintenance

With CENTUM VP, operators will have on-screen access to information on the status of all network devices, the charge remaining on the gas detector batteries, and the status of wireless communications, and thus will be able to quickly detect and respond to any abnormality. Thanks to this functionality, more efficient maintenance plans can be drawn up that, for example, will require fewer periodic checks.

About ProSafe-RS

Released in February 2005, the ProSafe-RS safety instrumented system helps prevent accidents by detecting abnormal conditions in plant operations and initiating emergency actions such as a plant shutdown. An independent certification body has certified that ProSafe-RS can be used in SIL3 applications. Unlike conventional safety instrumented systems and distributed control systems, which are regarded as having different roles and functions and operate separately, the operation of ProSafe-RS and the CENTUM integrated control system can be fully integrated. ProSafe-RS is highly regarded by users and has been installed in more than 2,100 projects worldwide (as of June 2017).

Yokogawa’s Commitment to the Field Wireless Business

Yokogawa developed wireless communication technologies for continuous processes that necessitate advanced control and released the world’s first ISA100 Wireless system devices in July 2010, thereby offering its customers a wider range of products to choose from. Currently, Yokogawa offers its customers in the oil & gas, and other industries a wide range of field wireless management stations, field wireless access points, wireless field devices, and wireless adapters for conventional wired devices.

Major Target Markets and Applications

For use in fire and gas systems (FGS) and emergency shutdown systems (ESD) in process industries such as oil, natural gas, petrochemicals, chemicals, pharmaceuticals, electric power, and iron and steel.

Dräger GasSecure

GasSecure AS is a subsidiary of Dräger, and has been a long term partner with Yokogawa in developing the market for wireless gas detectors using ISA100. GasSecure developed, markets and sells the world’s first truly wireless optical gas detector for demanding industrial applications. Representing an evolution in gas detection, the detector is based on innovative ultra-low power MEMS optical technology and has introduced a new level of reliability and flexibility for the detection of gas leaks. The totally wireless detectors increase safety and dramatically reduce costs for the oil & gas, petrochemical, marine, and other process industries. For more information, please visit www.gassecure.com.

False alarms from safety sensors?

So I do know about sensors and control systems, from the supplier point of view. But maybe like many suppliers I’ve only been on site to troubleshoot a sensor that is reported to be giving incorrect data. So someone else made the decision to question the validity of the sensor outputs.

These days, the nearest I get to regular sensor monitoring is at home, typically with smoke alarms, a CO monitor, and a flammable gas alarm. Plus the plant manager, my wife, is always demanding an immediate solution to any alarm system going off, to continue production.

The problem

A flammable gas alarm was positioned above the gas hob: perhaps in retrospect not the best place, as the instructions said humidity and steam should be avoided. But very quickly we realised that the detector was not very tolerant of any wine added to dishes being cooked on the hob. Then, surprisingly, it alarmed whenever we had bread dough baking in the (electric) oven. Since the detector was said to be set to alarm at 25% of the LEL this was surprising.

The instruction came down – ‘Get me a switch in that alarm circuit, so I can switch the piercing noise of the alarm off!’ So, there was my solution, and a task, so that was done. I did not think it through any further.

Time passes

This system worked well for maybe 3 years. The alarm switch changed power from the alarm to a lamp over the worktop, so we knew to switch it back on after a problem event. But such sensors must have a life, and so when the alarm started going off when the kettle boiled and steam drifted up past the detector, I thought the unit was failing. There were then several late evening alarms, for no apparent reason, and we could not smell any gas (it is difficult to detect these days), nor see anything untoward. Like every engineer I guess, I felt the sensor, to find it very hot. This seemed to confirm the problem, that the sensor was failing, so take the thing out – ‘it was not that hot before!’ Something had changed.

Six months later, this Summer, we had a new gas meter – a Smart unit – installed on the domestic gas supply. Ultrasonic measurement of the flow, wifi connection to the indoor display, and mobile network reporting usage figures to the supplier. That would all be great, except the fitter refused to reconnect the gas to the house, because of a slight leak detected indoors. We had to call out a plumber to deal with our in-house problems. Good job it was Summer, as that took over a week.

Finding the gas leak

The leak was located as somewhere in the piping to the gas hob. The plumber tightened up the connections under the hob, and repeated the pressure loss checks. Still a slight leak, but within allowable tolerances. OK, so he checks once more, to be sure, and starts his paperwork. A last twist of the 90 degree bend directly on the hob (supplied by the Chinese supplier) produced an interesting result: the threaded part of this connector sheared off, almost in two half-round pieces. It looks like steel, but low grade steel, and showed a brittle type fracture all around the fitting.

Presumably the crack that had been there before, allowing a slow leak, had led to the fracture on tightening the connection. That was installed 10 years before, and no-one had done any checks of that or the system post installation. OK, I had never had the systems tested for gas leaks.

What had happened?

The conclusion at this point was that the slow leak presumably collected gas in the lower cupboards, and when this escaped it combined with the wine vapours to trip the alarm. Possibly the steam from the kettle just accelerated the rise of the gas past the detector. The detector was presumably a Pellistor, and got hot because it was burning the gas off. The dough rising in the oven? I don’t know much about bread and dough – but the leak was directly above the oven, so maybe the gas and air, warmed from the sides of the oven, helped the gas rise up past the detector. If that fitting had actually failed totally one night, there would have been a major blast, as I had removed the gas detector.

We now have installed a new detector, further from the cooking (3 metres). Plus the old one is re-installed, as a back-up unit: it is working OK still, next to the boiler. The bad news: the new alarm went off last weekend, when simmering a Paella laced with white wine….

Yesterday the plant manager produced a batch of dough and made bread. Both flammable gas alarms went off, first the unit 3 metres away then the old reserve unit, now even further away in the utility room, with the boiler.

Legislation

In any rented accommodation the landlord has to have a gas system safety check once a year. Because we own our own house there is no such requirement, and the boiler service man, who checks the gas boiler and heating system once a year, is not required to, and does not include, a system gas leak test in his inspection.

Product or system failure?

The gas hob was made by Proline, and installed around 8 years ago by a registered installer. It was a Chinese manufactured unit supplied by Comet as a low-cost own-brand hob to many retail outlets in the UK. The 90 degree bend that failed was supplied as a part of the hob, the gas inlet port. It is not steel, it could be an aluminium or zinc alloy. It appears the design was such that this port could be stressed during installation or tightening, as the bend itself would not rotate to suit the angle of the delivery pipework. It seems the break was on the hob side of the fitting. A combination of a poor quality fitting and a poor design.

The flammable gas alarm seems to work OK in detecting natural gas, but is even more sensitive to alcohol vapours, bread and dough making, and using any window cleaning spray that has any hydrocarbons in the fluid. So beware of using them in a brewery, distillery, bakery, bread shop, pub, restaurant and so on!

There was undoubtedly a small gas leak, around the hob, which has now stopped. Possibly this was from the 90 degree bend fitting, which then completely broke apart on tightening the joint. It remains possible that this failure was an accident waiting to happen.

The domestic plant manager is none too pleased at the moment. So do I leave the sensors installed, take both or one of them away, or fit switches to suppress the noise and turn off the alarm(s)?

Postscript

The supplier of the unit is surprised and upset. He considers these sensors do not give false alarms, when exposed to wine fumes from simmering a paella, or from baking bread in the oven. He has asked me to return the newest one to allow him to test it.

This has been done so we will see what results!