Problem:
- sparks and hot particles appear in the pneumatic transport duct for shredded textiles, and can cause explosion or fire if they enter the so-called “pulper”
- the audit carried out by the insurance company showed an unacceptable level of fire / explosion risk
- the investor expected a solution similar to the one applied at the sister plant (CO2 extinguishing system), which in this case could pose a threat to the personnel
Solution:
- substantive discussion and presentation of arguments to the investor as to why the CO2 extinguishing system can pose a threat to the life of the personnel
- installation of a spark detection and water-based suppression system on the inlet duct of the pulper
Check the details of the implemented equipment and services:
Insurance company audit
The system was designed and implemented in the Polish plant belonging to an international company producing quilts and pillows. Previously, the company had been audited by the insurance company. The audit showed that the textile pulping line did not provide the required minimum level of fire and explosion safety. A risk that sparks or hot particles could be drawn with the raw material through a pneumatic transport duct into the pulper chamber was identified. This situation posed a fire or explosion hazard.
Why you should not always follow in your sister’s footsteps
In a sister plant located in the UK, a CO2 extinguishing system was used to protect similar equipment. This solution is very effective in many cases and we often recommend it as the optimal method of protection. In this case, however, we faced the protection of equipment with a working chamber that was not fully sealed, and the machine itself was located in open space in the production bay. This means that the gas fed into the machine would be emitted into the bay, posing a danger to personnel. This is because CO2 lowers the oxygen concentration and when it exceeds 6%, it becomes toxic to humans. This can lead to dizziness, fainting and, in extreme cases, poisoning. For these reasons, the production bay would have to be evacuated before the start of extinguishing, which would significantly delay the activation of the extinguishing system and result in production downtime.
It should also be noted that extinguishing with CO2 or other inert gases is activated only when a fire is detected. The spark detection and suppression system, on the other hand, can be activated earlier, i.e. before a potential ignition source enters the protected equipment. This type of protection is most often mounted on pneumatic or gravity transport ducts, used to supply the equipment – most frequently cyclones, dust filters and silos.
CO2 extinguishing and human life
The CO2 extinguishing system has many advantages and in many cases is the best solution available. However, it should be remembered that no persons must be present in the extinguishing zone, as this could result in the risk of their death. This is due to two factors:
- the principle of inert gas extinguishing is to reduce the oxygen concentration in the air,
- increased concentration of CO2 has toxic effects on the human body.
Effects of oxygen concentration reduction
Extinguishing with an inert gas requires the oxygen concentration in the air to be reduced to at least 15% vol. Such a concentration is detrimental to the physiological and mental functions in humans. When the concentration drops to 12.5% vol., human life is at risk. In case of a further decrease of oxygen concentration to approx. 10% vol., humans may suddenly lose consciousness. In addition, if the oxygen deficiency is caused by inert gases (e.g. nitrogen, argon, helium, etc.), the weakening of the life functions is not noticeable to the victim.
Under normal conditions, the CO2 concentration in the air is between 0.2 and 0.5%. When its concentration increases to 6%, we feel a slight dyspnea, fatigue and a decrease in perceptiveness. At a concentration of about 10%, the dyspnea is significant. Hallucinations occur, torpor increases and, after several minutes, light-headedness comes on. Also, CO2 concentrations between 10 and 20% cause breathing pattern disorders, fits and ultimately death due to the paralysis of respiratory tract muscles. A sudden increase in the concentration of more than 30% causes death due to cerebrovascular insufficiency and oedema.
A CO2 concentration significantly exceeding 30% is required for effective fire extinguishing, this level should be reached in under a minute.
Choosing the optimal solution
After technical consultations, we agreed with the representative of the investor that, in this particular case, the optimal solution will be to use a spark detection and suppression system. After acceptance of the solution by the insurer, it was successfully implemented.
