industrial explosion protection and risk assessment
i. elements of industrial explosion
when combustible materials (dust, gas, and smoke) are mixed with oxygen in the air and ignited, an explosion occurs. when an explosion occurs during the production process or in a closed storage container, the pressure will rise rapidly within a few milliseconds, and the destructive force will put personnel and equipment at risk. most equipment designed to handle, process and store materials is not designed to withstand deflagration. only devices specially designed to withstand the maximum pressure (pmax) produced by deflagration are spared, but such devices usually have a design pressure exceeding 75psig(5.2barg). so it's a very expensive device.
deflagration is the forward propagation of a flaming fireball at a velocity lower than the speed of sound, as opposed to detonation at a velocity higher than the speed of sound. generally speaking, protected industrial equipment may be protected from the hazards of deflagration.
dust explosion prevention and protection measures
in general, several measures are required to eliminate the danger of deflagration. the techniques used in these measures can be classified as passive and active. the typical passive protection technology is mechanical and does not require external energy. explosive release devices (called flameproof plates) are passive protection technology. the function of active protection system needs one or more energy sources to realize. explosion suppression system is an active prevention technique. spark detection and elimination system is an active prevention technology used to detect and eliminate the source of fire which may lead to fire or explosion. both active and passive protective devices require regular inspection. stainless steel explosion-proof plate provides economical discharge protection for dust explosion, but it must be installed in a safe position that can accept the fireball generated by discharge.
there are many options for the assessment of explosion risk
these measures can be classified as prevention and protection. the application of various measures needs to be evaluated separately, including the following:
1. quantitative analysis of risks; identify the deflagration characteristics of the raw material (which may require experimental determination).
2. consider whether preventive and protective measures should be applied.
direct explosive release is economically advantageous, but the full impact of the release must be assessed to determine the correct safety measures available:
1. can the fireball formed in deflagration be discharged?
2. when protecting indoor equipment, can drain pipes be installed?
3. how to isolate the connected equipment to prevent the spread of explosion?
4. can the equipment withstand the reaction force caused by discharge and exhaust?
5. can the building or equipment in the release area withstand the transient high temperature caused by explosion pressure impact and fireball?
the answer to the above question usually determines that several protective measures should be used, for example:
1. measures to restrain explosion extension without emission.
2. fire explosion hazard prevention measures: (daily management and processing management of limiting fuel load)
3. anti-static management, especially for dust with low minimum ignition point (mie)
4. management and control of spark generation source (such as grinding and milling) by means of spark detection and elimination technology.
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