Blast-resistant walls

Blast resistant walls are adequate for establishing the boundary of an area of exposure provided the protection from blasts is oriented in the correct direction. 

Rapidly deployed, soil-filled, blast-resistant walls... 

Tayout also has a significant role in minimizing the probability of ignition of a flammable release. Area electrical classification provides the basis for the control of electrical ignition sources. This classification is also used to determine the areas that require protection from vehicular access, etc. Frequently, highly hazardous processes that can result in overpressure (e.g., hydrogenation) are placed behind blast resistant structures/walls. 

The motor control center (MCC) and Substation have concrete block load bearing walls of ordinary construction. The control house is of blast resistant construction with reinforced concrete walls and roof designed for 0.2 bar static. All three buildings are 4 m tall. 

Increase the blast-resistance capabilities of windows by replacing glass with polycarbonate or laminated safety glass and, where necessary, upgrading frame design and attachment to walls... 

An option for upgrading blast resistance of an existing building may be to provide additional beams, columns, or walls strengthened with a mortar or concrete pneumatically projected at high velocity onto a surface. The concrete is placed on a cage of reinforcement, which is doweled into elements of the existing stmcture. 

However, it is normal practice in blast-resistant design to assume conservatively that the VCE blast wave is fully reflected from the front wall as an ideal shock. 

However, one additional requirement for blast resistant design should be considered. The presence of negative pressures and rebound forces require that wall to frame connections be provided to assure proper transfer of these outward acting forces. Figure 8,2 shows an application of anchor straps to handle rebound forces,... 

FIGURE 10.9 Blast Resistant Shell Around Existing Building 10.3.6 Barrier Walls... 

Another possible protective scheme, although rarely used in the petrochemical industry, is a blast resistant barrier wall. A barrier wall can be used to provide protection from fragments and reduce reflected wall loads. However, it will not reduce overpressures on the roof and unprotected side walls. 

The blast resistance of conventional doors is generally limited by the rebound capacity in the unseating direction. A conventional unreinforced hollow metal door with a cylindrical latch may be adequate to withstand a rebound force of 50 psf (2.4 kPa). Door with a mortised latch may be adequate for a rebound force of 100 psf (4.8 kPa). If the blast pressure exceeds this, other alternatives may be considered. These include placing interior or externa barrier walls, or installation of blast resistant doors and frames. Unlike conventional doors, blast doors are typically provided as a complete assembly including the door, frame, hardware and accessories. This is because all the components are dependent on each other to provide the overall blast resistance. Refer to Chapter 9 for performance requirements and design details for blast resistant doors. 

The majority of dynamic analyses performed in blast resistant design of petrochemical facilities are made using SDOF approximations. Common types of construction, such as single story plane frames, cantilever barrier walls and compact box-like buildings are approximated as SDOF systems. Several examples of such structures are illustrated in Figure 6.2. 

Masonry, both reinforced and unrein forced, is a common construction material in petrochemical facilities. However, unreinforced masonry is inappropriate in blast resistant design due to its limited strength and its nonductile failure mechanisms. Reinforced masonry walls with independent structural framing for vertical loads arc commonly used in blast resistant design. 

A typical shear connection for a wall girt might consist of a relatively thin two bolt shear tab. As a blast load is applied to the girt, tearout of the tab may occur due to an inadequate number of bolts or insufficient weld capacity. This will prevent development of plastic moment capacity of the member and thus reduce its blast resistance. A typical upgrade for this type of connection is addition of a new shear tab wetded or bolted to the existing column and girt. 

A new reinforced concrete wall has been determined to be a constructable solution to provide the required blast resistance. The new wall is simply supported at top and bottom. 

SILs are order of magnitude bands of PFDavg, which also reflects the amount of risk reduction of a preventive safety instrumented function. Non-SlS Mainly two parameters, namely, consequence and likelihood, which affect risk, are considered. The consequence is the potential severity of the hazard. The likelihood is the frequency of occurrence. Risk graphs/risk matrices are used for these purposes. The inherent risk can be reduced by non-SlS risk reduction. To assess the risk, one is required to know and evaluate the effectiveness of all non-SIS risk reduction measures to ensure that the risk is reduced to as low as possible before application of any SIS. In other words, it is required to assess whether an SIS is necessary to further reduce the risk. Non-SIS risk reduction methods could be consequence reductions such as a dike, whereas blast walls or blast-resistant control buildings could reduce likelihood. 

Reid, R.R., 2007. Rapidly deployed, soil-filled, blast resistant barrier walls. In Proc. GRI-20 Conf. GSI Publ, Folsom, PA, 10 pp. 

Lightweight Composite proprietary materials, typically of glass fiber and polyester resins, are available as sheet boards which can be arranged into protective walls or enclosures. They offer light weight, inherent insulation, and can be configured to achieve blast protection. These materials are corrosion free, and wear resistant. 

Connections for precast panels can be a problem for blast loaded buildings. Typical connections for walls rely on direct bearing for support of the panel for positive loads, and weld plates for negative loads such as wind suction. Rebound of stiff panels due to blast toad can be very high, and the connections typically used in conventional design may be inadequate to resist this load. Substantial and expensive changes arc often required to develop the full capacity of precast panels. 

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