Loose linings

Look for broken or loose lines from purge source. 

Other metals are available which have very specific uses. Their cost is very high but their use is often justified in certain processes such as fine chemical manufacture. They are generally used as thin cladding or loose lining supported by steel or stainless steel. 

Important applications for titanium have been developed in processes involving acetic acid, malic acid, amines, urea, terephthalic acid, vinyl acetate, and ethylene dichloride. Some of these represent large scale use of the material in the form of pipework, heat exchangers, pumps, valves, and vessels of solid, loose lined, or explosion clad construction. In many of these the requirement for titanium is because of corrosion problems arising from the organic chemicals in the process, the use of seawater or polluted cooling waters, or from complex aggressive catalysts in the reaction. 

Loose lining FEP Liner fabricated No vacuum Determined Visual Difficult... 

Other typical uses of titanium in a membrane cell process are in the pipelines for hot anolyte and in the anolyte collecting tanks as well as dechlorination systems that normally work under vacuum and sometimes limit the use of loose linings. 

Corrosion-resistant metals and alloys, including stainless steels, nickel alloys, titanium, zirconium, and tantalum can be applied as linings or claddings to cheaper steel substrates. Most (>90%) are applied by roll bonding, but weld overlaying and explosive bonding are also used, as appropriate. Particularly expensive metals, such as tantalum, can be used as very thin ( 0.5 mm) loose linings. 

Loose lining FEP PFA Modified PTFE All 60, 90, 125, 187 mils Liner fabricated outside the housing and slipped inside Liner fabricated by hand and machine welding Shop only No vacuum. Pressure OK Determined by body flange (12) and section height (12) Visual Spark Difficult... 

Figure 8.18 Loose lining for insertion in the steel housing. (Courtesy Edion Company.)...

Figure 8.21 Loose-lined modified PTFE column.

Figure 8.23 Supply chain and job sequence for loose lining.

Fabricate a liner, insert it in the steel piping and flare the ends over the flange. PTFE and PVDF account for most pipe below 12" in diameter. For pipe sizes above 14" (35 cm), the pipe is lined as a loose lining using FEP, PFA, or modified PTFE... 

Loose lining. The loose-lined construction is used to make thick tantalum liners and was historically the first approach to a duplex system. The tantalum liner is manufactured separately and inserted into reactor vessels without bonding with the structural base metal. This loose-lined construction is the most economical and most widely used fabrication method throughout the entire industry. Liner thicknesses of 0.5 to 1 mm are satisfactory against corrosion. It is also possible to improve this technique by welding the liners to the base metal (i.e., weld overlay). Although economical, the loose-lined construction has some intrinsic drawbacks ... 

Loose linings are predominately composed of fiuoropolymer sheets which are welded into lining shapes, folded, and slipped into the housing. The lining is flared over body and nozzle flanges to hold it in place. Weep holes are provided in the substrate to permit release of permeants. This is an ASME code requirement. Vacuum is permitted in vessels having diameters up to 12 in. (300 mm). Larger diameter vessels cannot be used under vacuum conditions. 

Performance of loose linings in large vessels has only been fair, but they have proven very successful in lined piping. Refer to Ref. 2. 

Thermoplastic sheet linings are used more extensively than any other type of lining. Table 3.1 lists the most common thermoplasts used as linings. These materials are used to line piping as well as vessels. They may be installed as a loose lining or as a bonded lining. 

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