Masonry lining

An all plastic tank may be used for a chemical process such as the reconstituting of spent hydrochloric acid. However, at higher temperatures, the acid will attack the plastic sufficiently rapidly to make its use uneconomical unless a masonry lining is placed inside the plastic to insulate the interior—to bring the temperature on the face of the plastic down to an acceptable level. The plastic, then, functions as supporting structure and membrane, and the three necessary functions are supplied by two materials. 

Corrosion resistant masonry lined metallic process equipment combine three vital components that must be designed to complement each other and function as a whole. 

Third, there is the masonry lining itself, which must be designed with the necessary thickness and shape to be thermally and mechanically stable. The lower coefficient of thermal expansion of the lining compared to that of the shell, under thermal loading, for example, must be compensated for by the insulating effect of sufficient lining thickness to keep the lining in compression. 

These supports will not make a rectangular or square vessel suitable for pressure or vacuum service. If such a vessel is to receive a masonry lining, it must be designed as a cylinder with dished or hemispherical heads, both top and bottom or as a sphere. (Reference 8, p 80). Such vessel must also be designed in accordance with the ASME Code For Unfired Pressure Vessels, Section VIII. 

RESISTANT MASONRY LININGS FOR CHEMICAL IMMERSION SERVICE... 

This specification provides guidelines for the design and fabrication, of vessels that are to be membrane-lined, and to receive a chemical-resistant masonry lining for corrosion resistance. 

Note In brick lining vessels, it is not a matter of particular concern that vessels be perfectly plumb. If the vessels have floating heads, then the piumbness does become very important. It is more critical for out work that we have the center line established, and then our other criteria, namely, out-of-roundness will tell us if the steel is acceptable for receiving a chemically-resistant masonry lining. 

The size of the metal rods or hoops in unlined wood tanks is determined partly by calculations related to the hydraulic load imposed by the contents, but may be modified by dictates of past experience. As noted previously, the chemically-resistant masonry lining on the walls and the bottom may impose additional loads on the walls requiring more tie rods or hoops. The tank designer should be aware of the possibility of loads on the structure caused by the irreversible growth characteristics and the thermal expansion of the chemically-resistant masonry. The accidental soaking and consequent swelling of the dry wood shell may also be a factor to allow for. 

Where there are design requirements for the release of compressive stresses in the masonry lining. 

Masonry linings consist of three basic items chemically inert masonry units such as brick, stone, or block bonding mortar or mortars and membrane materials. Such linings are used to protect vessels from mechanical damage, (such as blows or abrasion), thermal damage by providing sufficient insulation to reduce thermal exposure to a level the substrate can accept, or to limit the penetration of the chemical corrosive to the substrate to prevent corrosion of the substrate. 

Steel vessels which are to receive a masonry lining must conform to ASME boiler and pressure vessel code. Section VIII Division 1, and in particular the design detailed in paragraph UG-22 item 4, which states that in lined vessels, loading due to the lining itself (such as weights and stresses) must be taken into account to determine wall thickness and supports. 

The code, in paragraph UG-80, also stipulates an out of roundness maximum of 1% variation of all diameters from the normal diameter. This must not be exceeded in vessels to be masonry lined. 

Nozzles of masonry lined vessels, which must be sleeved, cannot have an out of roundness exceeding 0.4%. Refer to Figure 7.1. 

Concrete is ideally suited to being used as a supporting substrate for acid resistant masonry. It has a coefficient of thermal expansion closest to that of brickwork (5.3 X 10 as against 3.8 - 4.2 X 10" for most shale and fireclay brick— while steel falls into the range of 6.8 to 7 X 10" ). Concrete also has the ability to absorb blows and vibration without transmitting them to the masonry lining. 

Membranes are installed between the substrate and masonry lining to act as a barrier to prevent the corrodent that passes through the masonry lining from reaching the substrate. These membranes can be classified as rigid or nonrigid, and as true or semimembranes. 

Masonry linings are installed to protect the substrate from mechanical damage such as blows or abrasion and/or to prevent thermal damage to the membrane... 

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