Since our founding, Hunter has strived to diligently serve the refining, petrochemical and specialty chemicals communities by enhancing productivity and occupational safety through the reliable manufacturing of superior quality blast-resistant modular buildings. Blast-resistant modules (BRMs) have become a practical solution to industrial facilities for providing a cost-effective way to protect personnel or equipment. Many have realized the benefits Hunter provides of having a single point of contact for building procurement while minimizing on-site installation time, making it a global leader in the manufacturing and installation of blast-resistant buildings. People feel confident Hunter BRMs will protect their personnel or equipment in the event of an accidental explosion and satisfy various regulations, such as OSHA 29 CFR 1910.119, API RP 752 and API RP 753. However, it may be less well known Hunter’s BRMs protect building occupants from other potential hazards, including debris from interior building objects, fires and toxins.
How do BRMs address blast issues?
Hunter provides BRMs that satisfy the various levels of structural response as defined in the American Society of Civil Engineers’ design of blast-resistant buildings in petrochemical facilities — namely the low, medium and high response levels. Typically there is a trade-off where a lower response level will result in a more robust design, but many times a BRM designed for high response can provide sufficient protection. With the increasing use of quantitative risk assessments (QRAs) as opposed to consequence evaluations, an appropriate level of protection when using BRMs can be determined to meet acceptable risks. All of Hunter’s BRMs use structural steel components with welded connections designed to allow the components to stretch and distort without failing. Because of this, even at a high response, a BRM will not collapse or cause life-threatening injuries to building occupants from damage to the structure.
Furthermore, Hunter’s BRMs are designed so all walls can withstand blast loading from any direction or orientation, as opposed to having only one or two stronger walls with weaker walls on the rear. This allows Hunter’s BRMs to offer protection from potential explosions originating from any direction, unlike other BRM manufacturers.
Why are interior items a concern?
BRMs, like all structures properly designed for resisting blast loads, will deflect and sustain damage while absorbing energy when impacted by a blast load. However, the designed rapid movement of the building exterior can cause interior nonstructural items to be unintentionally thrown around, creating the potential for a serious injury. One type of interior nonstructural item of potential concern would be a stud wall installed just inside the exterior wall of the BRM that is finished out with drywall or other wallboard material.
In addition, the presence of furniture can become a debris hazard, such as bookcases and desks placed immediately adjacent to exterior walls, wall-mounted cabinets and items loosely placed on furniture. Other items may also include overhead items, such as light fixtures and ductwork, which could cause an injury if they were to fall. Given the relatively small building footprint of typical BRMs, high-velocity debris can have a significant likelihood of causing an injury since the building occupants are near exterior walls. This can be mitigated by properly designing the interior finish-out of a BRM.
Hunter has taken the necessary steps to reduce the likelihood interior items will become a significant debris hazard due to the blast response of the outer walls and roof or the lateral response of the building as a whole. However, conventional construction techniques will put these components in jeopardy of being thrown inside a BRM. For example, leaving a gap between the exterior building wall and the interior finished-out stud wall will significantly reduce the amount of damage to the finish-out of the building. Leaving a gap between the wall finish-out and furnishings inside the building will provide a similar benefit. Furthermore, providing a strong attachment between the roof of the building and the overhead lights, ductwork and other items will increase the likelihood these items will not fall during the blast response of the roof components. Without properly designing the interior nonstructural items, it is possible BRM occupants could be subjected to serious or life-threatening injuries due to interior nonstructural debris.
How do BRMs address thermal hazards?
Industrial facilities are becoming increasingly concerned with protecting their people from accidental fires. Buildings in close proximity to process units could be impinged by an accidental fire from a hydrocarbon release or affected by other thermal hazards such as pool fires. BakerRisk and Hunter can develop designs for BRMs that include thermal protection from fires in accordance with API RP 752.
BakerRisk can assist facilities with the siting of BRMs at their locations that provide convenient places for personnel while being located at a distance far enough away from potential fires so the building and its occupants are adequately protected. Insulating a BRM can often assist in achieving adequate thermal protection. BakerRisk and Hunter are aware of the most current developments in building insulation materials, including intumescent coatings applied to the exterior walls and roof and conventional wall insulation installed inside the building.
Escape routes from BRMs must also be considered when determining their locations at a facility. BakerRisk can develop an egress plan in the event of a thermal hazard.
How do BRMs address toxic issues?
In addition, BRMs are sometimes used for sheltering in place in the event of a toxic gas release. BakerRisk can perform dispersion analysis of a postulated release using its state-of-the-art proprietary software, which can determine the locations where a cloud may drift, as well as concentrations and durations of exposure. Hunter and BakerRisk can develop BRM designs that satisfy API RP 752 and ensure the safety of personnel. Hunter’s BRMs can be designed as a Shelter In Place (SIP) so personnel can safely remain inside the building until a toxic gas has dissipated.
BRMs tend to be very airtight due to their welded construction with the primary leak path through the HVAC system. It is possible to have no fresh air supply, but that creates a “sick building” issue where occupants become prone to illnesses. HVAC systems that draw outside air typically rely heavily on isolation dampers. This is more important with HVAC that runs in recycle mode versus one that turns off. Even if the HVAC is turned off with the damper closed, this is likely still the most significant leak path into the building. The ideal arrangement has two systems: one for temperature control and one for ensuring outside air is brought in during normal operation. The air supply system should also be isolated and well sealed during toxic emergency.
The next most important leak path is through doors. Ideal doors fit well, have compressible gaskets in good condition and latch tightly. A vestibule dramatically reduces “latecomer” issues and reduces the infiltration rate. In addition, wall and roof penetrations could be a significant path if they are not sealed. Hunter manufactures all doors that are installed on its BRMs and has quality control over every aspect to ensure the utmost safety to your personnel.
Clean air supply can dramatically improve BRM toxic mitigation effectiveness. Due to the small volume inside the BRM and the relative leak tightness of the building envelope, compressed air may mitigate toxic impact. The small building volume means a small air supply is required to effectively purge the building, and the tight volume means small air flow will reduce the infiltration rate.
Air-supplied respirators can be used to protect occupants even if interior conditions degrade. Personal protective equipment can be used to safely evacuate if interior conditions degrade. Without indoor monitoring, SIP effectiveness degrades, but procedures and training are necessary for occupants to know when and how to evacuate.
Hunter, BakerRisk: Working to make your facility safer
Hunter and BakerRisk are industry leaders in providing solutions to manage catastrophic risks. Together, they can help facilities understand what hazards may be present at their plants, provide BRMs that provide protection to personnel at industrial facilities from various potential hazards and assist with determining appropriate locations to site BRMs.
For more information, visit www.hunterbuildings.com or call (281) 452-9800.
