Seal Locations

Seals are required at entries by conduit or cable to explosion-proof enclosures containing arcing or high-temperature devices in Division 1 and Division 2 locations. It is not required to seal IM in. or smaller conduits into explosion-proof enclosures in Division 1 areas housing switches, circuit breakers, fuses, relays, etc., if their current-interrupting contacts are hermetically sealed or under oil (having a 2-in. minimum immersion for power contacts and 1-in. for control contacts). 

Seals are required where 2 in. or larger conduits enter explosion-proof enclosures containing taps, splices, or terminals in Division 1 areas (but not Division 2 areas). 

Except for conduit or cable entries into explosion-proof enclosures containing arcing or high-temperature devices (as described in Item I above), cables that will leak gas through the core at a rate of less than 0.007 ft /hr at 6 in. of water pressure need not be sealed if they are provided with a continuous gas/vapor-tight sheath. Cables with such a sheath that will transmit gas at or above this rate must be sealed if connected to process equipment that may cause a pressure of 6 in. of water at the cable end. 

Cables without a continuous gas/vapor-tight sheath must be sealed at classified-unclassified area boundaries. 

All cable terminations in Division 1 areas must be sealed. This requirement is imposed by API RP 14F, when specific cables are allowed in Division 1 areas. 

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Figure 26.30 shows details of a gas vent pipe system. The two details at the top left of the illustration show close-ups of the boot seal and flange seals located directly at the interface of the SWCR system with the FMC. To keep the vent operating properly, the slope of the closure system should... 

Fig. 331. Preparation of iron (II) iodide, a iron wire fo asbestos wool c iodine f seal location (after sealing, the section to the right of / is removed).

The turbine exhaust E seal was replaced with a segmented cylindrical piston ring seal, which became typical of all other seals. The turbine vertical inlet face seal was replao with two horizontal segmented cylindrical piston ring seals between the turbocompressor and a new adapter. These seals, located above and below the hot duct, are the same type as the turbine exhaust seal. The tee-shaped adapter also interfaces to the hot duct with a segmented piston ring seal that replaces the hot duct bellows that was previously used to accommodate thermal expansion. 

With the adoption of the seal concepts proposed by the seals task force, all seals are accessible for removal and replacement when the turbomachine is removed. The seals will utilize a softer material than those interfacing surfaces which are not intended to be replaced over their 60 year design life. The hardness of these latter surfaces will be attained with suitable coatings, of which chromium-carbide is one candidate. A second sealing location on these surfaces is incorporated in the design as a backup should the first location become inadvertently... 

Seal oil consoles The hydraulic seals, located at the outer ends of the compressor shaft, receive oil from the seal oil console (Exhibit 4-5). The seal oil equipment may be configured as a console or may be designed as individual pieces of equipment. 

When the mine ventilation, methane, and dust control plan is up for a 6-month review, all coal mines should determine satisfactory locations on the main entries for temporary seal locations. Furthermore,... 

For the very first section of the borehole a base from which to commence drilling is required. In a land location this will be a cemented cellar in which a conductor or stove pipe will be piled prior to the rig moving in. The cellar will accommodate the Christmas tree (an arrangement of seals and valves), once the well has been completed and the rig has moved off location (Fig. 3.13)... 

Control Room. The control room location can be critical to the efficient operation of a faciHty. One prime concern is to locate it the maximum distance from the most ha2ardous units. These units are usually the units where LPG or other flammables, eg, hydrocarbons that are heavier than air, can be released and accumulate at grade level. Deadly explosions can occur if a pump seal on a light-ends system fails and the heavier-than-air hydrocarbons coUect and are ignited by a flammable source. Also, the sulfur recovery unit area should be kept at a healthy distance away as an upset can cause deadly fumes to accumulate. 

Electrical Hazards. Because carbon fibers are conductive, the airborne filaments can create serious problems shorting out electrical equipment. The best option is to locate sensitive equipment in clean rooms outside of areas where carbon fiber is being processed. If this is not possible, electrical cabinets must be effectively sealed to prevent contact with carbon fibers. A filtered air-positive purge provides additional protection for sensitive equipment. 

Yu and Sparrow (]. Basic Eng., 70, 405-410 [1970]) give a theoretically derived chart for slot seals with or without a sheet located in or passing through the seal, giving mass flow rate as a function of the ratio of seal plate thickness to gap opening. 

Explosion-proof enclosures are characterized by strong metal enclosures with special close-fitting access covers and breathers that contain an ignition to the inside of the enclosure. Field wiring in the hazardous environment is enclosed in a metal conduit of the mineral-insulated-cable type. All conduit and cable connections or cable terminations are threaded and explosion-proof. Conduit seals are put into the conduit or cable system at locations defined by the National Electric Code (Article 501) to prevent gas and vapor leakage and to prevent flames from passing from one part of the conduit system to the other. 

Dust entrained in the exit-gas stream is customarily removed in cyclone cohectors. This dust may be discharged back into the process or separately cohected. For expensive materials or extremely fine particles, bag collectors may follow a cyclone collector, provided fabric temperature stability is not hmiting. When toxic gases or solids are present, the exit gas is at a high temperature, the gas is close to saturation as from a steam-tube diyer, or gas recirculation in a sealed system is involved, wet scrubbers may be used independently or following a cyclone. Cyclones and bag collec tors in diying applications frequently require insulation and steam tracing. The exhaust fan should be located downstream from the cohection system. 

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