PSD Doors Protect Your Equipment and Personnel

from Explosions due to Deflagration


An Explosion...

... is the bursting or rupturing of an enclosure or a container due to the development of internal pressure from a

deflagration. (From NFPA 68, Chapter 3)


Burning Starts the Potential Explosion Process


The following burning process causes overpressures that could result in explosions. 


  1. A sufficient amount of combustible dust or gas (fuel)

  2. When disbursed in a closed enclosure (vessel)

  3. With a sufficient amout of oxidant (oxygen or other like gas) and

  4. Subjected to an energy source (spark) of sufficient energy

  5. Will burn away from that spark at a certain speed

  6. And develop an overpressure within that enclosure.




  • If the velocity of that propagating pressure wave is less than the speed of sound, it is called Deflagration.

  • If the vessel is infinitely strong, a Maximum Pressure (Pmax) will be developed within the vessel.

  • "Deflagration Index" (Kst) of a dust or a Deflagration Index (Kg) of a gas can be computed.

  • These Deflagration Index numbers can be used to compare and calculate the relative severities of different materials. 


Burning with Excess Overpressure Causes Explosions


If the vessel is not infinitely strong, the pressure from the deflagration will burst or rupture the enclosure, defined as an Explosion.  .


PSD Doors Avoid Explosions


  • If equiped with a Vent opening of sufficient size and strength to relieve that developing pressure, the enclosure will experience a Reduced Pressure (Pred) below the potential Maximum Pressure, avoiding bursting or rupturing (Explosion) of the enclosure. 

  • PSD doors are Vents that use the Kst or Kg and Pmax values of the fuel with the characteristics of the vessel and any connected ducts to design and built hinged Vents that release the pressures safely below the Explosion pressures.

  • PSD uses NFPA 68: Standard on Explosion Protection by Deflagration Venting or guidance from FM Global Engineering to design explosion vents that protect your facilities and employees.


PSD Doors Protect Your Equipment and Personnel from

Process Overpressures due to Operational Errors


Excess Process Pressures, Not Explosions or Deflagrations


Process overpressures, (unlike pressures from burning dusts or gases that can cause explosions) stem from sequencing errors when opening or closing processing ducts and valves during production or cleaning.


Overpressures from these errors can cause damage to seals, bellows, and gaskets. 


PSD Doors have sucessfully been used to alleviate such damage.


If dusts or gases are not in the system or at levels below the minimum explosible concentration (MEC), we can size a PSD door to reduce your down times. 


PSD Doors Protect Your Equipment and Personnel from

Process Overpressures in the Petroleum Industries



Excess Nitrogen Blanket Pressures, Not Explosions or Deflagrations



API (American Petroleum Industry) Oil Separators and their lift (sump) stations use the PSD doors as accessable covers to preserve the protective nitrogen blanket that covers waste waters in this process. Contact us for more specific details. 

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