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API RP 752/753

The following overview is offered for your convenience and is intended to provide a basic understanding of API RP 752 and 753. Hunter encourages you to refer directly to the API’s formal verbiage as the ultimate authority on these and other Recommended Practices.

API RP 752

According to RP 752, there are several types of buildings commonly used in process areas. These building types and the effects of explosion overpressure on each are as follows:

Building Type Overpressure (psi) Consequences
Wood-frame trailer 2.0 Complete collapse
Steel frame/metal siding 2.5 All walls destroyed
Unreinforced masonry building 1.5 Complete collapse
Steel frame with reinforced masonry

2.5

 Complete frame collapse
Reinforced concrete 4.0
6.0		 Complete collapse

API Recommended Practice 752, Table 4 (1st Edition, 1995)

Hunter’s standard blast-resistant buildings are designed for use at overpressures up to 8 psi. We can also custom design a blast-resistant building with overpressures ratings to meet your unique building requirements.

API RP 753

Blast Zones
According to API RP 753, there are three (3) explosion hazard zones. Click here to see graph of zones.

“Congested Volume” refers to the volume, in cubic feet, of a collection of closely spaced objects that have the potential to increase flame speed to an extent to generate a damaging blast wave, such as an area populated with pipes, pumps, valves, vessels and other process equipment and supporting structures (See API RP 753.1.7.1 and 1.7.2 for actual API verbiage).

Buildings should be located in zones as follows:

 Table: Allowable Locations and Personnel for Portable Buildings Intended for Occupancy
  Light Wood Trailers Portable Buildings other than Light Wood Trailers Occupancy Restrictions
Zone 1 Not allowed Detailed analysis required House only essential personnel
Zone 2 Detailed analysis required Detail analysis required No restrictions
Zone 3 No restrictions

 No restrictions No restrictions

Toxic Release Hazards
Portable buildings located in areas where a toxic release can reach ERPG-3 levels should meet either of the following:

  1. Be designed for shelter-in-place; or
  2. Have an emergency response plan (see API RP 753.5).

Portable buildings used for shelter-in-place should have the following features as a minimum:

  1. Heating, ventilation and air conditioning (HVAC) systems capable of rapid shutdown of the system or placement in recirculation mode, whichever is more appropriate. This HVAC shutdown response should be included in the emergency response plan.
  2. Exhaust fans and duct penetrations of exterior surfaces equipped with a positive seal against infiltration of outside air.
  3. Emergency communications equipment (telephones are acceptable).
  4. PPE to be used by all occupants during the evacuation as necessary.
  5. Seals for windows and doors that are present.
Click here to view an example of a Blast Zone Diagram. 		[Photos]