Friday, July 20, 2018

Under Pressure

A common question regarding our watertight doors and hatches is how much pressure can they handle?  For the sake of simplicity (so we don't have to write out "door or hatch" constantly), we will discuss this using a watertight door as an example.  All of these questions apply to watertight hatches as well.  There are several variables to consider when answering the question about pressure:
  1. Will the pressure be pushing the door open (unseating/internal pressure), or will it be pushing the door closed (seating/external pressure)?
  2. What size is the clear opening for the door?
  3. How much pressure?
  4. Will this be "in case of emergency" or protection for the "once in 100 years flood", or will the water pressure be constant (for example, on the side of a tank that is normally full)?

Will the pressure be pushing the door open or closed?

If the pressure is closing the door, then more pressure can be applied without causing leaks, since the pressure is working to help seal the door.  If the pressure is opening the door, then it requires relatively small amounts of pressure to unseal the door panel and cause a leak.  How much pressure?   Well ...
 

How large is the door?

A smaller door can handle more pressure than a larger door.  We determine if our product can meet the specified requirements based on the number of pounds per square inch (psi) of pressure applied to the clear opening surface of the door panel.  For pressures in a closing direction, we are limited by the material strength of the steel or aluminum used for the panels.  If it is a large door panel, a large pressure load (greater than 30 - 40 psi) can eventually cause the panel to warp and fail.  For example, if you had 30 pounds per square inch pushing against a door with a 36" x 80" clear opening, that would equal 86,400 pounds or 39.27 TONS pushing against the door panel.  Cen-Tex products cannot handle that kind of pressure, however, MCS does consult with engineering firms that have built doors to handle higher-pressure loads on larger doors like this.
 

How much pressure?

A Cen-Tex door may be the perfect fit for you, provided your pressure requirement and door size are within limits we know the products can handle.  Depending on the size, Cen-Tex doors can handle approximately 30 psi in a closing direction, and approximately 2-4 psi in an opening direction.  These are rough estimates and do not take into account your door size.  For smaller door openings, Cen-Tex may be able to make doors to handle a higher internal pressure, but this needs to be evaluated on a case-by-case basis.  For pressure requirements beyond these specifications, we can consult with manufacturers that specialize in high-pressure closures.

Will this door be used in emergency situations only?

A door that will be used once to make sure that an electrical vault in a building located in a floodplain stays dry can be built differently than a door located on the side wall of a tank that will be kept full all the time.  If you don't care if the door "takes one for the team", may get a little bent in the process, may not close the same way once the pressure is removed, but still holds and does its job, then you can go with a door that is not over-engineered for the job.  These questions are always a balancing act between what it costs to design a door to meet any contingency, versus the likelihood of these incidents to occur.  Basically, you're trying to balance being prepared without going overboard and spending too much money to be prepared for a situation that may happen in 500 years, if ever.


In summary, these are general guidelines for items that need to be evaluated on a case-by-case basis.  The consequences of throwing more water pressure at a door than it is designed to handle are potentially life-threatening.  Our extensive product knowledge and experience will help guide you to the product that meets your needs, while helping you find a product that doesn't exceed your needs (and as a result, exceed your budget).

   

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