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Users are Ultimately Responible for their own Safety
These Standards are Specific to Germany
The exhaust alone doesn't lead to an explosion, but the three factors oxygen, fuel and ignition source in a certain combination.
1 Risk Examples
In connection with oxygen and an ignition source these are dangerous:
Combustible liquids, gases and steams
e.g. Acetone
Combustible materials
e.g. Magnesium
Mix of materials:
e.g. A mixture of steel and aluminum forms an explosive gas during corrosion of the steel.
Dust
All kinds of dust, which reach a higher concentration of 15-30g/m3 oxygen and fall below a grain size of 30 ¦Ìm, are dangerous in combination with an ignition source.
Ignition sources can develop through:
- Electrostatic unloadings
- Electrical produced sparks
- Flames
- Heat
2 Evaluation of the Explosion Risks
Not all kinds of dust and materials represent the same danger. Therefore different precautions must be made for different materials and processes.
Does a risk exist on my job? If so, how do I judge the risk?
The explosion risks are to be judged in their whole:
- Probability and duration of the occurrence of combustible fumes;
- Probability of the occurrence and the activation of ignition sources, including electrostatic unloadings;
- the machines, used materials, procedures and their reciprocal effects;
- the extent of the effects that can be expected.
3 Organization of Highly Combustible Zones
Highly combustible ranges are divided after frequency and duration of the occurrence of combustible fumes into zones:
Zone 0
Range, within which combustible fumes, as a mixture from air and flammable gases, are present constantly or frequently during long periods.
Zone 1
Range, within which, during normal operation, occasionally combustible fumes can form as mixtures from air and flammable gases.
Zone 2
Range, within which, with normal operation, combustible fumes do not or only briefly appear as a mixture from air and flammable gases.
(Pressure resistant ex - engines, ex - motor disconnect, engine, antistatic filter, optimal grounding)
Zone 20
Range, within which combustible fumes are frequently present as a gas containing flammable dust constantly during long periods.
Zone 21
Range, within which, during normal operation, occasionally combustible fumes are present as a gas containing flammable dust.
Zone 22
Range, within which, with normal operation, combustible fumes do not or only briefly appear as a gas containing flammable dust.
4 Determining Possible Precautions Against Explosions or Fires
- Prevention of the formation of combustible fumes, or, if this is not possible due to the type of activity,
- Avoidance of the ignition of combustible fumes and
- Weakening of the harmful effects of an explosion, in order to ensure the health and safety of the employees.
5 Prevention of Combustible Fumes
5.1 Regular Cleaning
- Regular cleaning of the suction apparatus, the pipes and hoses contributes substantially to the minimization of explosion danger.
- In the suction pipe a large quantity of dust can settle. It is not recommended to disconnect the hose during the process since the dust can exceed 15-30g/m3.
- A operation extension lag time of the suction apparatus after the treatment prevents additional deposits of particles in the pipework systems and hoses.
5.2 Pipework Systems Constructionally Adapt
- Pipes generally exclude dust deposits due to its open dimensions
- Property of cleaning
- A flow rate of 20m/s is guaranteed by adjustment of the diameter
- Pipes must be grounded because of static unloadings
5.3 Control
- A follow-up system cleans the pipework and hoses. It prevents additional deposits of particles. No matter the risk or the zone, regular cleaning is necessary.
- A filter flushing during the process prevents the brief formation of combustible fumes. The filter flushing only becomes active during process termination.
- Our machines are ready for this type application. With your own controller you can operate the valve and cleaning process. If no controller is present, we offer one with our system.
5.4 Flow Rate Increases
Starting from a concentration of 15-30g/m3 and a grain size of ¡Ü 30¦Ìm dust is considered dangerous.
According to the procedure, high flow rate helps to decrease the concentration from 15-30g/m3.
With an appropriate exhaust a critical dust loading can be excluded, to a large extent. With instructions (max. values) we are able to offer an optimal exhaust.
6 Avoidance of Ignition or Fire
6.1 Antistatic Unloading
Ries withdrawal systems, starting with the type GLS-B and larger, are all equipped with antistatic filters.
For highly combustible zones:
- ground screws attached at the housing, with the house grounding at 10 mm2, a grounding electrode to connect it with a static unloading; grounding is ensured.
- the pipeworks must use an antistatic suction hose or be grounded.
- with the suction apparatus, special IP 65 motors must be ordered.
- with the suction apparatus, a conductive powder coating with a resistance 108 must be ordered.
6.2 Precautionary Measures
- Ignition sources, e.g. cigarettes, mechanical. Prevent this in processing.
- Within the range of the high-risk zone there are warning signals for the danger of explosion and ignition sources.
6.3 Exhaust Hoods Material
- With exhaust hoods pay special attention to the fact that this is a rapidly transmitting manufactured material.
6.4 Burning Chamber
For containment we offer burning chambers, which are installed between the siphon and exhaust, to prevent burning material from entering the exhaust.
A burning chamber removes and settles burning particles. A further advantage of the chamber is a separation of the rough particles, which are deposited in a drawer for discard. The system dimensions create an optimal chamber.
6.5 Fire-Extinguishing System
Fires in connection with metal chips and sparks, which could remain for hours, are efficiently fought with a wet fire-extinguishing agent.
- Extinguishing agent containers with valve and nozzles
- Detection line and manual release
- An interface contact for an alarm is available.
6.6 Explosion Suppression
In order to avoid explosions completely, the suction apparatus can be equipped with an explosion suppression. Explosion Suppression systems are laid out in such a way that they detect and stop a burn reaction in the initial phase, before the pressure exceeds a preassigned amount and destroys equipment.
Explosion suppression is the prefered method if toxic media is processed, if the system is instaslled within enclosed spaces and/or a pressure relief would expose the personnel to an unacceptable risk with pressure, heat or fire. An potential explosion is detected in its initial phase and suppressed by sudden blowing out (within milliseconds).
The explosion suppression consists of:
- System control processes detect a signal and directly activates the attached explosion protection components. Floating contacts make an interruption in the system process possible.
- Supply voltage 18 - 30 V
- Explosion pressure detector with printing diaphragm ceramics (IP66)
- 10 liter Extinguishing agent containers with manometer for printing monitoring
- Discharge nozzle and gas discharge
- Manufacturer's conformity explanation
7 Possible Weakening Effects
7.1 Suction Apparatus Outside
The suction apparatus can be set up outside with explosion protection.
- This variant is to be done with the most favorable method for safety requirements.
- The disadvantage is a possible adjustment of suction power because of pressure losses by longer pipework. The mobility and flexibility of machinery is likewise reduced.
- With a possible explosion the suction apparatus would be destroyed. Unless the equipment was equipped with a simple explosion diaphragm.
- With a possible fire the suction apparatus is likewise destroyed.
7.2 Explosion Pressure Discharge Via Pipe Outside
- The suction apparatus can be equipped with an explosion diaphragm. A relief pipe is led outside to the explosion diaphragm.
7.3 Ex-Shelter
For protection against explosion the suction apparatus can be placed into an explosion-proof area.
- This variant creates an existing explosion-shelter or structure.
- The disadvantage is a possible adjustment of suction power because of pressure losses by longer pipework. The mobility and flexibility of machinery is likewise reduced.
- With a possible explosion the suction apparatus would be destroyed.
7.4 Explosion Pressure Discharge and Equipment
For protection against explosion the suction apparatus can be equipped with an explosion pressure discharge.
- The explosion pressure discharge consists of an integrated explosion diaphragm, which relieves the explosive gases and forces into the pipe. Up to 1500° C flames and gases are cooled down by energy transfer in the wide high-grade steel-mesh-filter basket. The gas volume is reduced and the flame expires automatically.
- Flames, burned and unburned materials are not withdrawn.
- A pressure increase and a noise disturbance typical of an explosion are reduced to a hardly perceptible level in the operating room.
- The operating condition is moitored with a signal generator and emits a warning signal on a light or control, via a separation circuit amplifier.
- The explosion pressure discharge is not certified for enclosed areas and an outward blow-off channel must be installed. Thus flexibility is ensured with the removal or adjustment of the machines without any loss.
The explosion pressure discharge consists of:
- Flame-trap with an integrated dust-trap made of high-grade steel
- Maintenance-free curved, three-part explosion diaphragm
- Signal generators by means of quiescent current interruption
- Separation circuit amplifier 24V DC/110V AC/230V AC
- Manufacturer's conformity explanation
 to the Material Database GESTIS
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