Basic criteria must be adhered to in designing, engineering and manufacturing blast resistant modular buildings. The four primary variables that need to be considered in developing a blast resistant building for petrochemical plants or refineries are the following:
- Freefield Overpressure (psi, bar, mbar, kPa)
- Duration of the blast event (ms) or Impulse (psi-ms)
- Damage Response Criteria as graded by the ASCE: High, Medium & Low
- Anchored or Slide designed building
This article addresses a critical variable, which is often overlooked when requesting a quote for a blast resistant building, the Damage Response Criteria. Philosophies vary among engineers and petrochemical companies in regard to which Damage Response Criteria is suitable for their respective location. Following are the three major Damage Responses as defined by ASCE:
All of these criteria are safe for personal and designed to resist the overpressure of the blast. The damage level determines the usability of a building following exposure to an event and also distinguishes replacement / repair costs. Low damage buildings are designed to have lower allowable wall deformations than Medium and High damage buildings. With that being said, the initial costs on low damage buildings are higher than that of the medium and high damage buildings. Early on, we noted that most customers selected either medium or high damage response criterion; however, over the last year we have seen an increase in requests to manufacture blast resistant building which are rated at Low Damage.
Buildings containing critical equipment such as Remote Instrument Enclosures (RIE) are typically designed to be Low Damage. Other buildings such as Control Rooms, Operator Shelters, or Alky Change Houses, are typically designed to either High or Medium Damage. These examples are only a representation of various buildings MBI has produced over the years. The final decision on which damage level to select is always determined by the customer.
Another thing to consider is the fact that damage level criteria and existing design standards do not give consideration to the hazards of flying debris during a blast. However, in the event of a blast, flying debris is a virtual certainty. For this reason, MBI has designed our standard building to resist various levels of projectile threats. We also have the ability to design buildings to withstand specific projectile threats as defined by our customers.
So, be sure to consider all the factors when selecting your next blast resistant building.