NEWS from REMBE®
So what does SIL involve?
When assessing the functional safety of a protection system it is above all important to ensure that its reliability matches the risks of a plant that is in danger. Such a SIL classification is based on a risk assessment that covers the probability of failure in a safety setup within a given scenario and the potential severity of any resulting damage. The defined tables and values, which can be found, for instance, in EN ISO 13849, lead to the required SIL level for the relevant (electronic) component. The higher the probability of occurrence and/or the potential severity of damage, the higher should be the requirements on the electronic componentry and also on the necessary SIL level. Any facilities with SIL level 4 certification thus offer the best risk minimisation and must be provided wherever probability and potential severity are especially high.
The risk assessment then forms the basis for an evaluation of measures designed to help reduce those two factors: probability of occurrence and potential severity of damage. The former is mitigated through preventive action, e.g. inertisation devices to prevent the occurrence of hazardous explosion-prone atmospheres). The severity of damage can be reduced through measures (e.g. explosion suppression systems).
SIL and “passive” explosion protection – REMBE® unites elements which belong together
SIL looks at the source which produces the functional safety of (E/E/PE) systems. The overall regulatory framework on which all certification is based is IEC 61508. Statements on the so-called “average probability of failure of the protective function at the point of requirement” have been available for quite a while as active protection systems, for instance, for REMBE®’s Q-Bic™ suppression systems.
Mechanical protection systems are not covered in this directive and cannot therefore be certified under it.
This has been the theory up to now. In practice, something else is required: Many plant manufacturers and operators in a variety of industries feel committed to SIL and demand that reliability parameters should also be available for mechanical protection systems, as they are often used in combination with (E/E/PE) systems and can only produce a consistent protection policy in its “overall effect”. Moreover a number of standards such as TRBS 2152-5 will expressly require certain SIL levels for protection systems in the future.
These practical requirements prompted REMBE® to take action: “Based on our close collaboration with customers and their planning and engineering offices, we are well aware that massive practical problems are likely to occur unless attention is paid to the safety gap of mechanical protection systems when reviewing the functional safety of explosion protection. With this in mind, we have set ourselves the task of finding a practical solution to the problem. After all, we are well aware of the vehement debates on the pros and cons of SIL outside electric, electronic and programmable electronic systems,” says Johannes Lottermann, PhD (Eng), Senior Consultant on Explosion Safety at REMBE®.
Based on these findings and its readiness for change, REMBE® has worked with IQZ, the German Institute of Quality and Reliability Management, in Wuppertal. Together, they have developed a transparent and legally sound methodology to assign SIL equivalents to REMBE® products despite their purely mechanical functions. The resulting PFD values (Probability of Failure on Demand) can thus be translated into “SIL language” under IEC 61508. It turned out that the company’s bursting disks had a SIL equivalent of 4, and the flameless venting devices a SIL equivalent of 2, due to the integrated electronic components of this SIL level.
“As we worked with renowned experts on the development of transparent methods in setting up PFDs, we are confident that the PFDs will be accepted in practice. REMBE® can be proud that, for the first time, this innovative approach is finally shedding some light into the darkness when it comes to assessing the functional safety of overall plant protection.
In a recent project, thanks to the SIL-equivalent parameters of our bursting disks, we helped a customer in New Zealand calculate the overall failure probability of their vented system which was protected by electronically controlled extinguishing barriers. This was a requirement specified by the relevant authority, and it was possible to complete the approval documents which, otherwise, would probably still be outstanding,” says Johannes Lottermann.
“The results of the relatively high SIL equivalents did not actually surprise us all that much,” says Stefan Penno, CEO of REMBE®. “It should be plausible to every engineer that a simple mechanical functional principle – like that of a bursting disk – is naturally more reliable than an electronic control circuit, despite all its sophistication and redundant backup systems.”
The company REMBE® has invited Ana and Kustaa from Windhoek to spend a month in Germany with an opportunity for some initial work experience. As both students have been studying German as a minor subject, the language barrier is only minimal. However, the cultural differences between Namibia and Germany are immense, and the two girls have therefore received a thorough induction in Windhoek. Also, REMBE® staff will be making a corporate effort to ensure that their Namibian guests have a good time in Brilon.
Their stay in Germany started, among other things, with a visit to the mayor of Brilon who gave them a very warm welcome to his town. Over the next few weeks, the two girls will be given an overall idea of each department at this medium-sized business, REMBE®. They can also look forward to a varied leisure programme during weekends.
REMBE®’s internship scheme with Namibia is a targeted social welfare programme, while at the same time encouraging opportunities for an international exchange. REMBE® wants to enable Namibian young professionals to gather some initial experience in a German company. “By creating this scheme,” says Annette Häger, member of the REMBE® Management Board, “we are showing how a company can be proactive in supporting young professionals internationally.”
The REMBE® initiative was welcomed by Onno Hückmann, the Ambassador of the Federal Republic of Germany in Namibia. When he spoke to Annette Häger, he emphasised the enormous importance of SMEs, in particular, to Germany’s economic success. He is especially pleased that REMBE® is acting as a pioneer in setting up the first programme of this kind in Namibia: “We need well-trained young people here in Namibia. Although there has been strong economic growth, the country still has a high level of unemployment.”
... to manage supplier information and risk within the supply chain as well as to procure efficiently in accordance with EU regulations. Achilles JQS is a cost effective system where suppliers in an easy and standardised way can advice details on their company and products and services to potential customers in a fair, open and transparent way. This facilitates and simplifies the tender process, offering new business opportunities for both buyers and suppliers. - See more at: www.achilles.com/en/
ISO/TS 29001 was developed specifically for the Oil & Gas industry and sets strict requirements on goods and services provided to ensure standardization and improvement within the sector. This latest certification constitutes an independent confirmation of REMBE®’s product and process quality as well as a demonstration of REMBE®’s commitment to the industry as a supplier.
The aim of ISO/TS 29001 was to provide a single QMS document to meet the needs of the oil and gas industries worldwide, specifically the major petroleum, petrochemical and natural gas organizations. Due to the inherent risks associated with the oil and gas industry, rigorous conformity to engineering, user and regulatory requirements are required. ISO/TS 29001 is available for use by manufacturers of oil and gas industry equipment and materials, service providers to the oil and gas industry, purchasers of equipment, materials, and services. The document can also be used for organizations to perform 2nd party auditing of their suppliers, as well as for the purpose of 3rd party certification.
From February 13th to 14th, all employees learned about REMBE®’s latest technical innovations. “Our employees abroad in particular need to be trained about the latest technologies," says Stefan Penno, Managing Director of REMBE® GMBH SAFETY+CONTROL. Since the company values external expertise, Prof. Dr.-Ing. Juergen Schmidt from the Karlsruher Institut for Technology (KIT), an expert for safety in chemical plants, gave an intensive speech about the topic “risk management” and illustrated the need for intelligent protection concepts. His view is that “Protection is not something that is only paperwork it is the ethical attitude of all operators. Therefore, industrial plants need the best and most innovative protection of pressure and explosion”. Accidents in industrial plants happen on a daily basis and threaten human lives. The cooperation between KIT and REMBE® supports the active exchange with students and professors in order to develop new products for process safety.
As well as Professor. Schmidt, Dipl.-Ing. Richard Siwek, CEO of FireEx Consultant GmbH, presented potential hazard sources for dust explosions in plants and informed all participants about the possibilities of hazard analysis and the latest technical rules and standards. “The process of production has to be monitored permanently, in order to protect the plant against uncontrolled explosions” Mr. Siwek appealed to the audience.
REMBE® loves sweets!
In addition to the theoretical framework, Mr. Francesco Petruzzelli of REMBE®'s Italian branch, gave practical insight of how a manufacturer of sweets uses an integrated REMBE® protection concept. Here not only are production processes protected against dust explosions, but also their trucks during loading. Loading trucks can cause electro-static reactions, which can be avoided by using the grounding systems of REMBE®'s collaboration partner, KERSTING GMBH SAMPLING+GROUNDING. Thanks to REMBE® and KERSTING, the customer and especially his sweets are now safe.
FPAL supports the European Oil & Gas Industry with auditing for relevant suppliers. For more details please check http://www.achilles.com/en/find-your-achilles-community?id=409
First of all, an explosion is nothing but rapid burning up of a material within a few milliseconds. It is the reactive forces released by this, which spread into the surrounding area in the form of flame jets and shock waves that are especially dangerous.
The process occurs at a very high speed. Controlled action in the event of an explosion is therefore almost impossible, in contrast to a fire incident, which takes place relatively slowly. In this case, fast and correct intervention often prevents anything worse from happening.
If the bases for explosion protection are considered, only three preconditions have to be satisfied to cause a dust explosion:
On the one hand, a flammable medium in dust form, which is dispersed into a cloud, is necessary;
- On the other hand, oxygen must be present, in order that, with the dust, it can create an atmosphere that can cause an explosion;
-Finally, a small source of ignition is sufficient to ignite the mixture of air and dust. In this way, a fireball that is extremely dangerous for the area surrounding it can develop.
Preventing dust explosions
There are different approaches for preventing dust explosions. These are all aimed at reducing one of the three afore-mentioned factors, in order to minimise the probability of an atmosphere capable of holding dust in it, or of a dust explosion. Examples of these preventive measures are the inertisation of equipment and the avoidance of active sources of ignition. However, regular maintenance of equipment and machines and keeping surfaces clean also reduce the risk of a dust explosion.
In practice, however, there are numerous applications, in which one of the three factors cannot be reduced, or not to the necessary extent. The risk of an explosion cannot be absolutely excluded, even when all possible safety measures have been implemented. For this reason, it is important to make provisions for reducing the effects to a tolerable level in the event of an explosion. These provisions can be summarised under the general heading "constructive explosion protection".
Protective measures against explosion can be implemented in different ways. The most current methods are listed below:
-; Explosion-resistant method of construction: when implementing this, a facility must be constructed in such a stable way that it can resist an excess pressure of at least 10 bars.
Explosion suppression: in the event of an explosion this will be detected in the shortest time possible. An extinguishing agent will then be blown towards the explosion, smothering the flames; in this way the dust explosion is suppressed.
- Explosion venting: bursting discs divert the shock waves and flame jets resulting from a dust explosion safely into the surrounding area. The bursting disc is designed and manufactured in accordance with the process conditions prevalent in the facility. At a specific pressure, as low as possible, the bursting disc opens and releases its cross section, the so-called venting area. In doing so, this venting area must be of an adequate size to safely allow an explosion to escape.
- Flameless pressure relief: If equipment or components are situated inside the buildings or in areas, in which a free pressure relief and the effects associated with it would cause damage, a flameless pressure relief is used. This way, the shock waves and flame jets are held back by a flame-trap affixed to the upper side of the bursting disc, so that there is no danger to the surrounding areas.
- Explosion decoupling: in the case of an explosion, the components of the equipment are decoupled from one another and from the remaining process; e.g. by non-return explosion valves. It is ensured that that the explosion does not propel the flame into equipment, which is upstream or downstream. The dust situated there would otherwise ignite and therefore trigger a secondary explosion.
It is essential to know the rim parameters and process conditions as precisely as possible for the construction of the explosion protection. It is necessary, therefore, for example, for the calculation of the required venting areas, to take account of the data regarding the equipment to be protected and of the exact key data about the existing material.
Intelligent pressure relief
A free pressure relief can only be guided into free, secured areas, due to the shock wave and the flame jet. In-facility traffic routes, close building developments or even public roads pose a problem time and again in the planning and implementation of such protection concepts. Operators often have no option but to determine very large areas at risk with safety distances around the installation for pressure relief. This additional expense means increased operating costs for the operator. The areas designated as safety areas may also no longer be used operationally, as entering them is extremely dangerous and is not permitted. It is precisely those traffic routes, which are used in-facility and also publicly, where a free pressure relief cannot therefore be implemented. Flameless pressure relief or explosion suppression is ideal protection concepts for keeping the effects of an explosion as low as possible. For many facility operators, however, a controlled pressure relief is a practicable alternative.
Problematic interpretation of standard specification
The diversion of the flames and shock waves into uncritical areas is addressed, amongst others, in Standard EN 14491. In Annex E of it, the use of so-called deflector plates is referred to. These are affixed in such a way that the effects of the explosion are diverted at an angle of 45° to approx. 60°.
The Standard does not mention, however, that the deflector plates must be constructed and fastened at great expense due to the tremendous repulsive forces. For a container of 20 m3, these forces amount to 50 kN (5 to), with an impetus of 25 kNs. In addition, these elements represent an enormous barrier during normal operation and take up valuable operational space.
New type of pressure relief
Against this background, the Brilon company, Rembe, has developed a new type of pressure relief. Targo-Vent is an opening angle delimiter, developed especially for bursting discs, which diverts the pressure relief into defined areas.
Targo-Vent cushions the bursting disc dynamically, progressively and can, therefore, elastically absorb large kinetic forces itself. The damper absorbs the enormous repulsive forces of the energy from the explosion and guides the explosion flames in the required direction. Depending on the conditions of application the flame is diverted upwards at a defined angle of approx. 30° to 45°. In this way, the shock wave and the flame jets are diverted into uncritical areas. This, in turn, allows the operator to minimise the safety areas around the vent openings and guarantees safe use of traffic routes. A further advantage in daily practice is that during normal operation Targo-Vent is assembled in a space-saving way on the bursting disc. No expensive baseplates or reinforcements are required. The system itself is made of maintenance-free stainless steel and does not cause any further current expenses.
Targo-Vent is manufactured in all current bursting disc sizes, so that retrofitting in existing facilities can be implemented without any problems. The system, in combination with Rembe bursting discs and venting panels has been type-tested and authorised in accordance with the Atex Directive 94/9/EC (Atex 114) (FSA 13 Atex 1637). Targo-Vent is therefore suitable both as the initial equipment for new bursting discs and as retrofitting component for installations already existing. The user receives an intelligent explosion protection, which involves neither high costs nor complicated fitting. Shock waves and flame jets, which arise during a dust explosion, are guided into the right channels, so that people and machines are protected from devastating damages.
read more about TARGO-VENT
Mike MacClancy Rembe Ltd managing director explained why the company had made this move: “Since incorporating Rembe Ltd in August 2009, Rembe’s UK business in bulk solids explosion protection, flow control and process pressure relief has steadily grown in all areas and applications by offering an unprecedented level of service to all customers. We keep extensive stocks of an ever increasing range of products for fast response deliveries; 48 hours door-to-door at no additional premium charge is now becoming something of a daily occurrence. Servicing and commissioning is also now regularly undertaken from a growing mature staff. Our previous facility was simply inadequate for our needs.” Colworth Science Park is the former headquarters of Unilever and is still used by Unilever R&D. The new premises offer high-speed fibre optic web connection and many state-of-the-art business facilities. Rembe Ltd’s central London offices are being retained.
The exhibition allows customers in the Middle East the opportunity to meet with REMBE® and discuss how the REMBE® superior laser technology can help their organisation to improve process reliability and reduce operational costs.
REMBE® Business Development Director, Orhan Karagöz, said “The Middle East and Africa are important growing markets for REMBE® and exhibiting at ADIPEC is key to that growth. I’m pleased to say it’s been another successful event for REMBE® and we are already starting our preparations for next year”
ADIPEC 2014 takes place in Abu Dhabi from 10th – 13th November.
But what makes wood material and wood handling processes so special in terms of explosion hazards?
This question can be answered quite simply: Considering requirements of dust explosion phenomenon:
- combustible dust
- air / oxygen
- effective ignitions sources
nearly all wood handling installations have the “perfect mixture” for dust explosions to occur.
Using the example of a fiber board plant, where all typical wood industry-related equipment such as silo´s, conveyors, screens, mills, dryers, cyclones and dust collectors are found, an explosion hazard is even more likely, as all the above-mentioned equipment creates wood dust causing explosive atmospheres. Additionally, given mechanical moving parts as well as drying processes, ignition sources are easily generated. In Autumn 2012, this deadly combination led to one of the most severe wood dust explosions in history in South America, where 5 people lost their lives and the entire plant was shut down for more than 5 months.
How to protect against explosion hazards in wood handling installations?
The explosion safety concept for such plants typically is made up of a combination of explosion prevention measures (to reduce the likelihood of explosion) and explosion protection measures (to reduce the effects of an explosion to an acceptable level).
Explosion Prevention means taking measures to prevent the formation of explosive dust clouds as well as avoiding ignition sources by dedusting, housekeeping, grounding, proper maintenance and/or spark extinguishers.
We know that even if all preventative measures are applied (especially with regard to the latter), this approach might lead to misapplication of spark extinguishers which
- might not work if particles are large;
- cannot suppress an explosion;
- are only addressing the ignition risk arising from small, hot particles; and
- do not prevent ignition sources from tramp metal or hot surfaces.
That is why protective measures also have to be applied in most wood handling installations. They typically apply one of three approaches:
- explosion resistant design (simple explanation: make equipment so sturdy it will withstand explosion overpressure of up to 10 bar)
- explosion pressure venting (simple explanation: pressure and flame relief by applying a predetermined breaking point on the installation)
- explosion suppression and (simple explanation: a rapid fire extinguisher that stops the flame )
- plus: Explosion isolation (simple explanation: Prevent flame and/or pressure propagation to down or upstream units)
Due to minimal maintenance requirements and low invest costs, passive explosion protection approaches such as explosion pressure venting is the most commonly used in wood handling facilities. The fact that these burst panels can even be combined with flame-trapping mesh materials allows various applications to be protected by so called flameless vents.
As with any comprehensive safety concept, even a fully protected plant can only be secured when all relevant persons, situations and conditions are taken into account. In practice, this means that plant management in the wood handling industry has to be aware of the explosion risk in general, implement available explosion safety measures and educate plant personnel. The awareness of the need for combustible dust explosion safety has to be raised so that catastrophic events are not likely to endanger health, lives and business objectives such as profitability, continuity and productivity.
Therefore, a risk analysis should be carried out to identify the hazards and to allow the implementation of appropriate safety measures.
As an aside: The “butterfly” effect!
When conducting a risk analysis, all circumstances have to be taken into consideration – this last example impressively shows that even small “bugs” can influence the explosion risk of plants:
Several saw mill operators carried out a risk analysis and decided not to protect their installations that handle wood chips with normally high humidity content. These conditions changed following a pine beetle infestation that led to numbers of dead/dried trees. After a long period of quarantine, these trees were purchased at a low price and brought to the sawmill. Due to the pine beetle infestation, the resulting wood chips lots were drier than usual and many explosions occurred in the saw mill plants, lead to long downtimes and several injured people.