Joints enclosures

Figure 31.4(b) Rubber or metallic expansion bellows for enclosure jointing and end terminations (Courtesy Best Crompton)... 

H. C. Hottel and E. S. Cohen, "Radiant Heat Exchange in a Gas-EiUed Enclosure," paper presented at ASME/AIChE Joint Heat Transfer Conference, University Park, Pa., Aug. 1957, AIChE Paper No. 57-HT-23. 

In outdoor type switchgear or controlgear assemblies the normal practice is to provide a double door in the front to house the front panel and protect the door knobs, meters, lights, pushbuttons, reset knobs or other accessories mounted on the door and thus prevent water or dust leaking through joints, knockouts and fitments etc. It is also recommended to have a canopy on the top of the enclosure to protect the panel from direct rain. Figures 13.6 and 13.28 illustrate this type of construction. 

This test is applicable to all outdoor metal-enclosed switchgear and controlgear assemblies, as in lEC 60298, lEC 60694 and ANSI C-37/20C. The enclosure to be tested should be complete in all respects including its mounts, bushings (for HT switchgear assemblies, 1 kV and above) and wiring. One or more vertical units can be tested simultaneously as may be convenient, but not more than 3 m panel width can be tested at a time. For a multiple unit switchboard, however, at least two vertical units should be tested together to check the joints between the units. 

The normal practice of all leading manufacturers is to keep the same bus and enclosure sections for the outdoor and indoor parts of the bus system. This is to retain simplicity in design and ease of jointing and interconnections. But this may prove to be a costly arrangement, as now the indoor section of the bus system will have to be... 

For LT bus systems The length of the test piece will be a minimum 6 m as in lEC 60439-2 with at least one Joint. The Joints must be both in the conductor and in the enclosure in each phase. If the total length of the bus section is less than specified, the entire length of the bus system in the fully assembled form will then be tested. 

Structural baghouses are limited to very large baghouses. All structural components are fabricated as separate panels with formed flanges. The panels are bolted or welded in the field. These flanged joints serve as stiffeners to the hoppers, plenum, tube sheets, and baghouse enclosures. 

In addition, they are usually constructed without isolation valves on the fuel supply lines. As a result the final connection in the pipework cannot be leak-tested. In practice, it is tested as far as possible at the manufacturer s works but often not leak-tested on-site. Reference 32 reviews the fuel leaks that have occurred, including a major explosion at a CCGT plant in England in 1996 due to the explosion of a leak of naphtha from a pipe joint. One man was seriously injured, and a 600-m chamber was lifted off its foundations. The reference also reviews the precautions that should be taken. They include. selecting a site where noise reduction is not required or can be achieved w ithout enclosure. If enclosure is essential, then a high ventilation rate is needed it is often designed to keep the turbine cool and is far too low to disperse gas leaks. Care must be taken to avoid stagnant pockets. 

FPN No. 2) The explosion characteristics of air mixtures of gases or vapors vary with the specific material involved. For Class I locations. Groups A, B, C, and D, the classification involves determinations of maximum explosion pressure and maximum safe clearance between parts of a clamped joint in an enclosure. It is necessary, therefore, that equipment be approved not only for class but also for the specific group of the gas or vapor that will be present. 

To determine if there is intrusion of unfiltered air into the clean work areas from outside the clean room enclosure through joints and cracks in the walls, ceiling, etc., other than from the pressurized air supply system... 

Toluene Bath (Fig. 35).—This bath consists of a double-walled enclosure, access to which is obtained by a hinged door carrying a stout rubber joint. The door is fastened by thumb-screws. Any suitable liquid can be placed in the outer jacket to which is attached a condenser the liquid, however, most generally used is toluene (B.P. 110°). The inner compartment... 

This parabola defines the area of flame transmission through the joint. Its vertex is usually nearby or somewhat below the stoichiometric point. All gases show a behaviour similar to that shown in Fig. 1.3. The knowledge of the vertex MESG values of gas-air or vapour-air mixtures is essential for the construction and use of enclosures, type of protection flameproof... 

A similar situation exists for the particles generated by fault current arcing in flameproof enclosures after passing the flameproof joints (see Section 6.8). 

Before considering individual types of electrical apparatus, flameproof joints as an essential element of d shall be dealt with. The contents of EN 50018 and IEC 60079-1 are different, depending on the edition of the standard. The requirements are listed in Tables 6.27, 6.28 and 6.29. The values given in these tables are constructional requirements and ensure the flameproofness of an enclosure except for extreme shapes, e.g. long U-shaped pipes for electric heaters. In such cases, the gap shall be reduced to an appropriate value. 

Type of joint Minimum Maximum gap (in mm) for volumes V (in cm3) of enclosure... 

The width of a joint is the shortest path through a joint from the inside to the outside of a flameproof enclosure (in a very general sense, it is the length of the flame path)... 

Table 6.28 Minimum width of joint and maximum gap for enclosures Group IIC (according to EN 50018 and IEC 60079-1/4th edition)...

Table 6.29 Part IIA Minimum width of joint and maximum gap for Group IIA enclosures (according to IEC 60079-l/3rd edition + Amendment...

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