Special fasteners

A typical plate is shown in Figure 11.22. The plate sections are supported on a ring welded round the vessel wall, and on beams. The beams and ring are about 50 mm wide, with the beams set at around 0.6 m spacing. The beams are usually angle or channel sections, constructed from folded sheet. Special fasteners are used so the sections can be assembled from one side only. One section is designed to be removable to act as a manway. This reduces the number of manways needed on the vessel, which reduces the vessel cost. 

As a general rule, the access to uninsulated live parts within an apparatus shall be possible only with the aid of a tool. Some types of protection, e.g. flameproof enclosure - d and increased safety - e - require special fasteners complying with the following ... 

Requirements are given in EN 50014 as well as in IEC 60079-0 General requirements, covering all types of protection. Plugs and sockets shall be mechanically or electrically (or otherwise) interlocked to avoid disconnection when energized, or shall be fixed together by special fasteners and additionally be marked with a warning label DO NOT SEPARATE WHEN... 

The standards for flameproof enclosure - d EN 50018 and IEC 60079-1 give additional requirements for plugs and sockets not fixed together by means of special fasteners ... 

The plug and socket according to Fig. 6.142 shows a coaxial arrangement of the contacts of a three-phase system. The central multi-contact pin is intended for six pilot and auxiliary circuits. Plug and socket are fixed together by means of a special fastener. 

Despite unfavorable mechanical properties of polyethylene compared to polypropylene, PVC, ABS, and Nylon, HDPE is the most popular plastic in WPCs. Polypropylene is too tough and makes difficult to use nails and screws as fasteners at a deck installation. Polypropylene-based composites require special fastening systems. PVC is typically considered as not environmentally friendly. Other polymers are not weather stable, brittle, or expensive. 

Proper Connections There are many ways to connect electrical conductors plugs, receptacles, screw terminals, wire nuts, and other special fasteners. It is important to tighten the screws or other fasteners that form electrical connections to ensure the conductors make good contact with each other. In some cases, codes specify the force or torque required for a coimection. Over time, vibration, corrosion, creep of materials (see Chapter 10), damage, and other factors may reduce the connecting force. These... 

CPA. Copolymer alloy membranes (CPAs) are made by alloying high molecular weight polymeries, plasticizers, special stabilizers, biocides, and antioxidants with poly(vinyl chloride) (PVC). The membrane is typically reinforced with polyester and comes in finished thicknesses of 0.75—1.5 mm and widths of 1.5—1.8 m. The primary installation method is mechanically fastened, but some fully adhered systems are also possible. The CPA membranes can exhibit long-term flexibiHty by alleviating migration of the polymeric plasticizers, and are chemically resistant and compatible with many oils and greases, animal fats, asphalt, and coal-tar pitch. The physical characteristics of a CPA membrane have been described (15). 

Portable tanks may be stowed io the holds of conventional cargo ships or special container ships, or they may be fastened on deck. 

Special precautions must be taken regarding end bearing for these members to avoid crushing of the web at peak response. If end bearing controls, the allowable response is limited to reduce the chance for non-ductile failure. Connections for these members also present difficulty because of the thin web material. To develop the ultimate strength of a member, multiple fasteners may be required so that the shear strength of the materia is not exceeded. 

Virtually no chemicals are used in the assembly. Wires and components are fastened in place by ingenious clips, with almost no soldering. Occasionally, but certainly not commonly, some small quantities of solvent are used for cleaning special applications. 

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