Tanks and Vessels

Welded tanks are preferable to those riveted or bolted. 

Fastener joints provide sites for creviee corrosion. 

Secure the flatness of welded plates on tank tops and bottoms during welding. 

Avoid undrainable horizontal fiat tops of tanks where possible provide appropriate drainage. This applies also to underground tanks 

Slope tank bottoms towards drain holes to prevent coUection of liquids after emptying of tank. Direct inlet pipes towards the center of the vessel. 

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During the course of operations such as filling and draining tanks and vessels, light hydrocarbons are lost. These losses are expressed as volume per cent of liquid. According to Nelson (1958), the losses can be evaluated by the equation (/ (/... 

Careflil material selection is required to prevent brittle failure of tanks at low temperatures. In addition, for tanks where the service temperatures are reduced, it is essential that an engineering analysis be performed to ensure that the tanks are not subject to brittle failure at the house temperature. The tank and vessel codes usually specify allowable materials based on design temperature. Further information about selection of metals for low temperature is available (8). 

Contrac tors bids offer the most rehable information on cost. Order-of-magnitude costs, however, may be required for preliminary studies. One way of estimating them is to obtain cost information from similar facihties and scale it to the proposed installation. Costs of steel storage tanks and vessels have been found to vaiy approximately as the 0.6 to 0.7 power of their weight [see Happel, Chemical Process Economics, Wiley, 1958, p. 267 also Williams, Chem. Eng., 54(12), 124 (1947)]. AU estimates cased on the costs of existing eqiiipment must be corrected for changes in the price index from the date when the equipment was built. Considerable uncertainty is involved in adjusting data more than a few years old. 

Develop operating instructions on the correct or permitted connections between tanks and vessels... 

Provide adequate fixed fire protection for tanks and vessels containing flammable, unstable or reactive materials. This can include fire loops with hydrants and monitors in the storage area, foam systems for individual tanks, and deluge spray systems to keep the exposed surfaces of tanks cool in case of fire in an adjacent tank. 

Development of electrostatic charges in tanks and vessels in which hydrocarbons are pumped or stirred is widely recognized as a serious hazard. This electricity, which is generated in tanks during these normal operations, occasionally causes a spark in a tank vapor space. 

For tanks and vessels, welded units are preferred over riveted or bolted designs. Fastener joints provide sites for crevice corrosion. Undrainable horizontal flat tops of tanks should be avoided unless proper drainage schemes are included in the design. Tank bottoms should be sloped toward... 

Do not allow nitrogen or air supplies to overpressure tanks or vessels. Tanks and vessels could be designed to withstand the air and nitrogen header pressure. Another solution is to install a pressure relief valve downstream of a pressure reducing station sized to relieve the entire flow on failure of the station. 

Standards and codes have very speeific safety requirements for Uie design of tanks for flaimiiable liquids or gases and pressurized chemicals such as aimnonia. Overpressure devices and vents are included in Uie design. Tank and vessel supports should be built for the ma.ximum intended load. 

A useful application is for tank and vessel heating, with the heater protruding into the vessel. Bayonet heat exchangers are used in place of reactor jackets when the vessel is large and the heat transfer of a large mass of fluid through the wall would be difficult or slow, because the bayonet can have considerably more surface area than the vessel wall for transfer. Table 10-43 compares bayonet, U-tube, and fixed-tubesheet exchangers. ... 

Above ground (internal surfaces only) Surface and elevated water storage tanks condensers and heat exchangers hot-water storage tanks, processing tanks and vessels hot- and cold-water domestic storage tanks breweries and dairies (pasturisers). 

If the vessel is a pressure vessel the optimum length to diameter ratio will be even greater, as the thickness of plate required is a direct function of the diameter see Chapter 13. Urbaniec (1986) gives procedures for the optimisation of tanks and vessel, and other process equipment. 

Figure 7-18 Bonding and grounding procedures for tanks and vessels. Adapted from F. G. Eichel, Electrostatics, Chemical Engineering (Mar. 13, 1967), p. 153.

Equipment such as pumps, compressors, tanks, and vessels associated with large inventories of flammable gas or liquid (>5000 gallons) should be provided with equipment emergency isolation valves to stop the flow of material if a leak occurs. For example, the decision to add emergency isolation valves to the inlet and outlet of a compressor is dependent on the flammability of the gas, its pressure, and the quantity of gas in the associated piping and vessels. 

For equipment, tanks, and vessels containing flammables or heated combustible liquids, their steel structural supports, legs, and anchors should normally be fireproofed for a 2-hour fire resistance rating. Some typical examples of where fireproofing should be applied are ... 

Refrigerated vessels handling flammables should also be provided with fixed fire protection in a manner similar to that of other storage tanks and vessels. Water spray protection or fireproofing of vessel surfaces that could be fire exposed should be considered. Where fireproofing is used, it should be specified for a fire endurance rating of 1 hr. 

Authorize tanks and vessel fabricators to order materials before drawings approval. 

Supports for tanks and vessels, which are to receive brick linings, must be located to support the weight of the brick lining. 

Rubber has been used by the mining industry, both in the form of cured rubber and in its uncured state, for bonding and vulcanising to metal surfaces of tanks and vessels for over half a century. It has been used to protect such items of the plant and equipment from the deleterious effects of abrasive wear, caused by elements such as coal dust, ore particles in slurry and solid form and dusty fumes. 

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