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Edition 03/2017

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Article

ATEX: Blower technology and explosion protection

AERZEN combines effective reactions with preventive measures

As specialist in blower and compressor technology for conveying air and gaseous media, the AERZEN Ex-protection within different ATEX-zones is a part of day-to-day business.

Combustible dust, spatial distribution, oxygen share, ignition source and the closed reservoir are components of a dust explosion and form the so-called explosion pentagon.

Combustible material

ATEX
In ATEX relevant application ranges such as the chemical industry technologies of AERZEN are the right choice.

Dust-air mixtures are explosive when the dust consists of combustible material. This includes besides timber, flour and cellulose cocoa, coffee, starch and inorganic substances such as the elements magnesium, aluminium and iron. These raw materials are typical when pneumatic conveying systems are used for which blowers or compressors made by AERZEN ensure the continuous supply of the production by the silo.

Closed reservoir

Pneumatic conveying uses a piping system for the material flow. Here, in the sense of the explosion pentagon this concerns a closed reservoir, without which an explosion is not possible, and without which a pneumatically driven material flow would not work.

Dust distribution

The process air generated by blowers or compressors conveys amongst other things fine dusts and powders through the piping system. Then, inside the piping, the conveying air is mixed with the product. The fine distribution increases the risk of a dust explosion as the combustible substance can ignite easily due to its large surface and the maximum availability of oxygen. 

Oxygen

If a substance burns, this conceals an oxidation. In case of a fire, this proceeds slowly, in case of an explosion abruptly. Both of them have in common that oxygen is needed to generate a fire as well as an explosion. Therefore, explosives always carry their own oxidant. No matter whether timber or explosives: Both of them need activation energy fed in from the outside to be able to burn or explode.

Ignition source

What a match is for timber and a lit fuse for explosives is for pneumatic conveying mechanical friction, electrostatic charges or hot sparks. Frequently, they are sufficient as activation energy to detonate a dust-air mixture.

Influence of the blower technology on the explosion pentagon

Concerning pressure conveying of dust or combustible gases, the only way to intervene with the conception of the suitable blower or compressor technology is at the ignition source of the explosion pentagon. It must be excluded that an ignitable energy source is introduced into the conveying medium. Concerning assemblies with ATEX approval (2014/34/EU) AERZEN most effectively and elegantly integrated a spark arrester in the discharge side silencer. The highlight of this solution is that the spark arrester works simultaneously as effective silencer. Compared with silencers with dampening material, concerning reactive silencers a slotted piping system eliminates the noise by means of a time-delayed interference of sound curves (interference method). This patented functional principle on the one hand works free from wear with regard to the otherwise eroding, loosening filter fabric and on the other hand ensures that sparks peter out and extinguish across the long way through the silencer.

Cause for sparks

spark arrester
The spark arrester within the AERZEN discharge silencers represents an effective measure to safely prevent the entry of activation energy into the material conveying flow.

Potential risks in Ex-protection areas cannot be excluded even with a blower. If it comes to an input of sparks into the pressure pipe, as a rule, this results from a defect of the compressor stage. A too high bearing clearance, for example due to lack of maintenance, may be the reason why inside the rotary pistons do not rotate any longer with the defined air gap but hit together and generate sparks. In application ranges coming under the ATEX regulations, the spark arrester within the discharge silencers represents an effective measure to safely prevent the entry of activation energy into the material conveying flow. Thus, the silencer is among the reactive ATEX measures, as it is used when a damage has already occurred.While the above measures aim to guarantee the Ex-protection, particularly for pressure pipes, AERZEN considers also for vacuum conveying the ATEX requirements as integral part of a blower solution from one single source. Concerning vacuum conveying the penetration of the material into the blower must be excluded safely. For this, mainly filter inserts are used, creating a barrier between the material to be transported and the assembly, in this case providing the negative pressure. Furthermore, AERZEN developed their own zone separation filters, representing as so-called sentinel filter a further decoupling between the upstream process and the assembly. “If it comes to a filter fracture we can react accordingly quickly and shut down the assembly, before an explosive atmosphere can generate inside the compressor stage,” explains Fabian Pasimeni, product manager for blowers and rotary lobe compressors at AERZEN. If, however, as a result of a chain of unfortunate circumstances it comes to an explosion the effects on the environment can be reduced effectively by using special material for the construction of the compressor stage. Pasimeni: “If the ATEX requirements and the explosion risk are high, for the housing of the compressor stage we no longer use normal grey cast iron, but special spheroidal graphite cast iron.” Mainly in ATEX relevant application ranges AERZEN uses early warning systems to prevent serious and safety relevant damage from the start. Here, this concerns the active mechanisms of Condition Monitoring, with which potential damage can be detected reliably - mainly by means of vibrational monitoring. “We offer an expansion stage covering three levels,” says Pasimeni. The easiest way to monitor vibrations of a compressor stage are special measurement points installed near the bearing positions. With sensors as second expansion stage AERZEN takes a step towards continuous monitoring. The sensors installed at the sides of the compressor stage measure continuously and emit corresponding 4-20 mA signals which can be monitored and evaluated by the control system. If the AERZEN blower itself is installed in an ATEX zone, the sensors are supplied with a corresponding approval. “Meanwhile, our modular system of blower solutions is so nuanced that we are able to quote for different applications with varying ATEX requirements as standard,” states Pasimeni. Based on this extensive know-how AERZEN developed the third stage of real-time monitoring. With up to four sensors per compressor stage “we can look precisely into the inside and find out the condition of the corresponding bearing,” explains the product manager. This includes condition monitoring of internal rings, Pitting (local material damage) and touching of the rotor against the internal housing wall as a consequence of thermal deformations. If the assemblies themselves are installed in an ATEX zone, AERZEN serves this application with motors of different rating and further components with ATEX approval.

Compact news

inauguration of the Aerzen Asia site

Aerzen Asia opens new head office in Singapore

On 25th August 2017, Aerzen Asia officially opened its new head office for the Asia Pacific(APAC) region in Singapore. Customers, partners, suppliers and colleagues of the region and fromGermany participated in this event. Klaus-Hasso Heller (CEO AERZEN), Chuck Lim(Vice President Aerzen Asia Pacific) and StephanBrand (Vice President Marketing & Product Management)gave very inspiring and encouraging speeches about the importance of team spirit, co-operation, friendship and future orientation for the team in Asia. In his speech Chuck Lim emphasised that the term “team” stands for“Together everyone achieves more.” So, each member of the team is an important piece of the puzzle.Later on, during a ceremony, symbolically the ribbon for the inauguration of the site was cut and they had a glass of sparkling wine. A traditional lion dance, asking for happiness and prosperity followed. After lunch, they had a guided tour across the premises. On the first floor of the two-storied building of Aerzen Asia the offices are located. At the ground floor there is a workshop for the After Sales Service. Here the focus is on overhauling and repairing blower and compressor stages. The training centre for many technicians in the AERZEN service team in theAPAC region is also located there. The special facilities and equipment are on the same level as at the parent company in Germany.With its new head office Aerzen Asia is well prepared for the challenges of the expanding business environment.

Application brochure

Applications with water vapour: new brochure

The know-how and experience that AERZEN has gathered over the decades in almost all types of application are particularly strongly reflected in water vapour and vapour recompression processes. The compression and transportation of water vapour is a complex process, which can only be achieved through the use of special technology and finely-tuned processes. In this context, water vapour is often used as a medium to provide heat in boiling, evaporation or distillation processes. This method can also be used during drying processes and for heat production in the chemical and foodstuff industries. The new brochure “Applications with water vapour” (A5-010-00) provides information about the AERZEN product portfolio in terms of water vapour compression, which includes a wide range of special blowers and compressors, combined with extensive application expertise. Please have a look at this new brochure.

Participants

First Business-Event for Aerzen North Africa

Aerzen North Africa has moved into new premises: to mark the occasion, the subsidiary’s first business event took place on 9th August 2017 in Cairo. 30 customers and plant manufacturers from the wastewater, cement, steel and chemical industries were invited to the Hotel InterContinental. After welcome speeches from Managing Director Dr.-Eng. Ahmed Yehia and Steffen Glindhaus (Director, Middle East & Africa), employees introduced the team, products, applications and the service orientation of Aerzen North Africa. The establishment of Aerzen North Africa and the move into new premises mark an important step for the AERZEN Group, enabling the company to provide support for many customers and installations in North Africa through its own, local sales and service network.

Alejandro Knoop with Adrian Dubini

Order No. 1 for Aerzen Argentina

Adrian Dubini will always be remembered at Aerzen Argentina. The Managing Director of Dubini Automación placed the first order with the new AERZEN subsidiary, founded on 1st May 2017. In appreciation, Alejandro Knoop, Director Aerzen Argentina, invited his first customer to join him for a photo. Mr. Dubini ordered a positive displacement blower Delta Blower GM 15 L. This assembly, from AERZEN series Delta Blower Generation 5, will be used for pneumatic conveying at a manufacturer of pet food and veterinary products.