Pipes grounding

Ttu pci roniiance of this type of electrode grounding is almost the same as for the pipe grounding (Section 22.1.2) its is the viirialion in resistance to the ground with the length of the electrode as in Figure 22.4. 

A-With concrete outer shell, we now have support for the brick, but note that the membrane is discontinuous at the bottom where it terminates at pipe edge. E-This is a typicai iniet design, with the entry pipe simpiy embedded in the waii, membrane brought to pipe edge and brick laid around the intruded pipe. Ground movement or expansion/contraction of the pipe can push or pull the pipe through the cavity in the concrete and cause the joint and membrane to be disrupted, and contained liquid to get back to the concrete. 

Water plays a primary role in corrosion of the metal walls of tanks and pipes (17), and increases the tendency for high speed pumps to produce wear particles and to exhibit shortened life. Formation of corrosion products can be controlled by addition of corrosion inhibitors, a mandatory additive in military fuels. However, corrosion inhibitors may also degrade other fuel properties and adversely affect ground filtration equipment. Thus they are not generally acceptable in commercial fuels where rigorous attention is given to clean and dry fuels upon aircraft fueling. 

Parts with fiber volume fractions up to 60% can be fabricated by filament winding. The procedure is often used to manufacture composite rocket motors, corrosion-resistant tanks and storage containers, and piping for below-ground appHcations. 

Chemical-Porcelain Pipe Made of dense, nonporous material and fired at 1230°C (2250°F), chemical-porcelain pipe, fittings, and valves are inert to all acids except hydrofluoric but are not usually recommended for alkalies. Surfaces, except when ground for gasketing, are usually glazed for easy cleaning. Working pressures of 0.3 to 0.7 MPa (50 to 100 Ibftin") are recommended for valves and piping. Temperatures of 200°C (400°F) or more can be used, but sudden thermal shocks must be avoided. 

AOC provide the additional advantages of reducing ground-space requirements and piping and pumping requirements and of providing smoother column operation. 

Ground area and. space requirement.s. Comparisons of the overall space requirements for plants using air cooling versus water cooling are not consistent. Some air-cooled units are installed above other equipment—pipe racks, shell-and-tube exchangers, etc. Some plants avoid such inst ations because of safety considerations, as discussed later. 

Examples of the sacrificial-anode method include the use of zinc, magnesium, or aluminum as anodes in electrical contact with the metal to be protected. These may be anodes buried in the ground for protection of underground pipe lines or attachments to the surfaces of equipment such as condenser water boxes or on ship hulls. The current required is generated in this method by corrosion of the sacrificial-anode material. In the case of the impressed emf, the direct current is provided by external sources and is passed through the system by use of essentially nonsacrificial anodes such as carbon, noncor-rodible alloys, or platinum buried in the ground or suspended in the electrolyte in the case of aqueous systems. 

Protect against the accumulation of electrostatic charges which can cause ignition. This may include the bonding and grounding of the tank, piping. 

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