Vent panels

Consider the safety of personnel in rooms or buildings if those spaces are to be vented, e.g., by vent panels. 

After three months of operation mild explosion vent panel lifted. 

After three months c f operation mild explosion vent panel lifted. Three weeks later another explosion roof blown off tank. 

These quasi-static pressures are determined by the total heat energy in the explosive and/or combustible source, the volume of the enclosure, the vent area and the vent panel configuration, the mass per unit area of vent covers, and the initial ambient conditions within the enclosure. 

Typical sections through vent panels evaluated in the suppressive shields program are shown in Fig. 36, together with definitions of vent area ratios which were found to correlate with attenuation of transmitted blast waves. 

Equations 30 and 31 apply to any vented panel configuration which has been tested (e.g., all safety approved shields) and to uniformly vented structures, i.e., structures vented in the same manner through all sides and the roof. 

A building or enclosure incorporating pressure resistant and pressure relieving features should be designed by an engineer competent in this area. Construction should be performed by qualified construction contractors. Vent panels and vent panel relief devices that have been listed or approved for this use are available. 

As a precaution against explosion or fire hazard the precipitator casing may be of explosion-resistant construction, with venting panels on its roof and sides. 

Protection against explosions is typically provided by explosion-venting, using panels or membranes which vent an incipient explosion before it can develop dangerous pressures (11,60). Protection from explosions can be provided by isolation, either by distance or barricades. Because of the destmctive effects of explosions, improvement in explosion-prevention instmmentation, control systems, or overpressure protection should receive high priority. 

Deflagration venting (see NFPA 68) is highly applicable to powder operations. This is because most powder operations are at atmospheric pressure, the rate of deflagration pressure rise is usually small enough for vent relief panels to be of a practical size, and the subsequent fire is limited because most powders cannot bum in bulk. 

Containment of explosion overpressure, i.e. by designing plant eapable of withstanding in exeess of the maximum explosion overpressure, or safe venting of forees, e.g. via blow-off panels, doors, membranes. 

In fact, the air was not vented. The 1 -inch vent line on the air supply was choked by a wasp s nest. Although this example primarily illustrates a wrong assumption, a second factor was the inadequate indication of the state of the oxygen valve by the panel light. A similar error was a major contributor to the Three Mile Island nuclear accident. 

Environmentally Responsive Work-stations (ERWs). Workers in open-office areas have direct, individual control over both the temperature and air-flow. Radiant heaters and vents are built directly into their furniture and are controlled by a panel on their desks, which also provides direct control of task lighting and of white noise levels (to mask out nearby noises). A motion sensor in each ERW turns it off when the worker leaves the space, and brings it back on when he or she returns. 

Using a nomograph requires only the vessel volume in meters, selecting the dust class. St-1, St-2 or St-3 from Table 7-28. Using Tables 7-29 or 7-30 select the Kst value determined experimentally. The reduced pressure, Pfed. (maximum pressure actually developed during a vented deflagration, termed reduced explosion pressure) must not exceed strength of vessel (see earlier discussion) and the Psut, i.e., the vent device release pressure. Note that the static activation pressure, Pjj, must be determined from experimental tests of the manufacture of relief panels such as rupture disks. 

Containment of explosion overpressure or safe venting of forces, e.g. via blow-off panels, doors. 

Deflagration venting in buildings and process vessels is usually achieved by using blowout panels, as shown in Figure 9-10. The blowout panel is designed to have less strength than the walls... 

Directional Venting. Most vented explosion safety structures are designed with blowout wall panels, entire walls, entire roofs, or even the entire roof and one wall. Other walls and roofs in the structure are designed to withstand a worst-case explosion without catastrophic failure. The explosion-proof parts of the structure provide some close-in blast protection, and hopefully complete protection from fragments and thermal radiation. But blast in the venting directions is not always attenuated compared to free-field blast and can even be enhanced in certain directions. 

For facilities susceptible to the contamination of nitroglycerin liquids and vapors, basic construction materials of wood framing, reinforced concrete, fiberglass reinforced plastic, and sandwich panels were chosen for development of architectural details incorporating lead conductive floor lining, equipment doors, personnel escape chutes and doors, ceiling and wall interfaces, interior finishes, joint sealing, door and wall louvers, wall vents, wall penetrations, and fixed windows. 

Work in the Hood. A hood is a specially constructed workplace that has, at the least, a powered vent to suck noxious fumes outside. There s also a safety glass or plastic panel you can slide down as protection from exploding apparatus (Fig. 1). If it is at all possible, treat every chemical (even solids) as if toxic or bad smelling fumes came from it, and carry out as many of the operations in the organic lab as you can inside a hood, unless told otherwise. 

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