Throughout our lives, we have been exposed to the importance of visual signalling in keeping us safe. From the flashing green man on pedestrian crossings and the flashing of blue ambulance lights in our rear view mirror to emergency beacons and strobes mounted on industrial machinery; we are tuned to acknowledge these signals and take some kind of action to minimise any danger.
The use of visual warning signals becomes so much more important when used in situations where the potential hazards present can lead to catastrophic damage to life and property.
Facilities such as those in the Oil and Gas, Petrochemical, and Pharmaceutical industries have such hazards and so visual warning signals are an integral part of most fire and gas detection and prevention systems designed for and installed in such facilities. The nature of the potential hazards present within these facilities also requires that the signalling used meets a specific set of safety criteria and be certified for use in line with the site classification, making them very much a critical safety product.
Fire and gas (FG) detection systems should provide sufficient warning to enable personnel to enact emergency protocols allowing them to seek shelter or engage corrective action to mitigate risk of escalation. There are a number of factors that influence the effectiveness of these systems in providing these warnings such as detector reaction times, control system efficiency and the type and placement of warning signals on site.
It is a simple truth to say that the sooner site personnel receive a warning, the chances of a favourable outcome increase.
Fire and gas detection system design
When designing modern FG detection systems, significant focus is placed on those parts of the system that detect and communicate potential events to the overall plant control system so that automated responses can be activated.
Detector manufacturers are pushed to provide ever quicker response to the detection of leaks and ignitions and the performance of modern detection devices in conjunction with the latest integrated control systems ensures that new FG detection systems provide a marked improvement over legacy systems designed only 10 or 15 years ago.
So, whilst it is only right and proper to invest in the latest technology when designing control and detection systems, why do so many new systems make do with legacy products when specifying the devices which actually translate the digital detection into the visible alarms that provide the practical warnings to onsite personnel?
So Where do Visual Warnings come into this
The use of warning light signal products in hazardous areas goes back hundreds of years to the use of the Davy Lamp in mines which as well as providing illumination, also warned against the presence of hazardous gases such as methane and CO2. Even contemporary signalling products still utilise methods of protection which have been used for decades (the first British patent for an electrical flameproof enclosure was granted in 1884!).
The technology of putting visual warning devices into flameproof enclosures has not altered significantly for many years. The main development of these products over the past 50 years came in the material construction of the flameproof enclosure; for example with the introduction of non-metallic Ex d enclosures.
The performance of many products in terms of light output has altered little over the last 30 years, with Xenon light sources being used today being very similar to those in use all those years ago.
However, the change in approach to overall system design, the use of PLC controlled DCS systems for example, should be pushing for the introduction of signalling products which, at the very least, offer more energy efficient solutions that minimise the power required to drive them.
Hereby lies the problem, low power equals low output. If you want a bright xenon beacon, you need to be prepared to feed it the requisite current (which is why intrinsically safe products are limited in their use).
FG systems designers are well used to compromising overall system efficiency to support the all-important field alarm devices and hence little has changed in the specifying of visual alarm devices in FG systems over the past 30 years (The copy/paste of old “EExd” specifications into modern project instrument datasheets is proof of this); even the relatively recent introduction of LED technology as an alternative to Xenon has been undermined by the perceived lack of light quality and effective output (more on this later…).
So why should more time be spent on re-assessing the specification of visual signals if nothing has changed?
The fact is that there are real reasons and benefits in reviewing specifications. In the past few years, E2S Warning Signals has introduced products which offer such significant advances over legacy signalling products that there are real technical, operational and commercial advantages in integrating them into FG systems.
Let’s look at strobes…
The Gulf region is sunny. Really sunny and really bright. This creates challenges when it comes to providing visual warning signals, especially outdoors. The rule of thumb is that for a strobe to be effective in such lighting conditions it needs to have an effective candela (cdeff) rating of over 300.
This has historically been the realm of the higher energy Xenon tube (I use this term rather than “High Output” as clearly some 21Joule strobes do not have a particularly high output).
For example, one major Gulf petroleum company has as their “standard” strobe a 21 Joule Xenon beacon, providing an output of 355 cdeff. This standard has remained in place for many years. It is based on a legacy product that requires 1.4 amps to drive; a power consumption of over 33 Watts.
This specification is used in major projects not only for the Petroleum Company, but also for many other operators and contractors who choose to accept this standard as their own.
So why should this particular company, or any other operator, contractor or OEM consider spending the time and effort reviewing this specification?
Take for example a large capital project such as a new oil refinery. There could be upwards of two thousand strobes installed on a refinery, many included as part of detection systems, managed by the DCS system. Many of which will require battery backup in case of power outage.
IF the F&G system design chooses to stick to the tried and tested legacy “standard” specification, they will need to include some significant infrastructure to support just the strobes on the site:
Based on 2000 units in use on site, 66KW of power is needed to drive the strobes based on legacy specifications
There are modern strobes which can provide the required light output for a fraction of the current cost. Newer LED products which utilise high end, powerful LEDs which produce superior light quality are available. E2S LED strobes can provide over 300 cdeff of output for less than 10% of the current required for the “Standard” legacy product as well as having a longer effective strobe life.
5.2KW of Power needed to drive strobes based on new products.
Such a reduction in the required power will have a direct effect on the cost of the infrastructure needed to support these new strobes; reduced number and/or size of power supplies, lower cabling costs and vastly reduced battery demand.
Another reason for re-addressing your strobe specification is to look to improve light output. As previously mentioned, the earlier someone’s attention is drawn to a warning signal, the sooner they can act on the appropriate protocols. So in some cases, given that the Gulf region is so sunny and bright, a strobe with a significantly higher cdeff output might be beneficial in attracting attention.
Modern strobes which utilise specifically designed lenses which enhance the output, as well as more efficient circuits can generate a significantly higher effective output than legacy models.
Remember our “standard” strobe from earlier? 21 Joules Xenon, 1.4A current draw supplying a “High Output” of 355 cdeff.
As can be seen in Table 1. Modern alternatives can provide significant output increases whilst still considerably reducing current draw.
For example, E2S has 10 Joule Strobes available with outputs up to 645 cdeff and yet still only requiring 605mA of current to drive them.
For a more direct comparison, the E2S D1XB2 21Joule Xenon Strobe has an output of 1,250 cdeff; over 3 times as bright as the “Standard” strobe. This is real “High Output”, and yet it still only draws 2/3 of the current as the “Standard” strobe.
How much earlier might such a strobe catch someone’s attention in the bright Gulf sun? How much sooner might they react and enact a protocol which might save someone’s life?
And there’s more…
As well as the possibility of significant performance improvement and cost savings, there are many other reasons why strobe specifications should be reviewed including the provision of truly Global Certification;
E2S has products that are ATEX/IECEx Zone 1, UL Class 1 Div1, Class 1 Zone 1 AEx, UL1638 and SIL approved and as such are suitable for use throughout the Gulf Region without having to pick and choose which approval you need.
In modern FG detection system design, warning signals are too often considered to be commodity end of line devices and hence legacy specifications are used again and again.
Given the key role that these devices play in the notification of site personnel to a range of emergency situations and the contribution they can make to the overall efficiency of the system, it seems naïve at best and negligent at worst to underestimate the benefits that the utilisation of the latest generation of visual signals can provide.
For more information, go to www.e2s.com