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March 2017

The first edition of American Petroleum Institute (API) Recommend Practice (RP) 753 Management of Hazards Associated with Location of Process Plant Portable Buildings was released in 2007. The RP was predicated on the assumption that light wood trailers, defined as consisting of standard 2” x 4” construction with a thin skin, were the weakest type of portable building used at processing facilities. However, self-framing panel buildings, lightweight aluminum trailers, and portable buildings constructed with light gauge insulated metal (sandwich) panels, etc., may be weaker than light wood trailers and should be analyzed carefully prior to being placed near congested volumes that could produce damaging blast loads.

Blast resistant modules (BRMs) have become a popular option for facility owners wanting to site portable buildings. However, it is sometimes not clear how to specify the appropriate BRM for a given application. In addition, it should be understood that other, non-BRM, options may also satisfy the requirements of API RP 753. Finally, it is important to understand that all buildings, including portable buildings and BRMs, may experience significant wall deflections due to applied blast loads. These wall deflections can create significant debris hazards inside of the building envelope. Debris hazards may be increased in smaller portable buildings due to the limited standoff distance between building occupants and exterior walls.

In order to address these concerns, BakerRisk has prepared a paper for the 2017 Global Congress on Process Safety Loss Prevention Symposium entitled Real World Applications of API RP 753. The paper provides example portable building API RP 753 siting analyses to illustrate relevant points. The example includes a discussion of the detailed analysis requirements for siting a portable building within the API RP 753 Zone 2-3 boundary. In addition, the paper discusses a potential range of portable building options available to owner/operators seeking to comply with API RP 753, such as heavily-framed (e.g., 2”×6” or 2”×8”) wood trailers, retrofitted ISO shipping containers, and commercial BRMs. The paper also presents a brief discussion of the internal debris hazard associated with the blast response of two different portable buildings as observed during full-scale testing conducted with the BakerRisk Deflagration Load Generator (DLG) test rig.

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