What determines the thickness of the equipment’s lining layer?

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Hello everyone, fiberglass storage tanks or pipeline systems are lined with materials such as PVC, CPVC, or FEP. The compatibility between the lining material and the medium is something that needs to be taken into account, including the selection of the resin grade. But how is the thickness of the lining layer determined? If there are any professionals available, please help clarify this. Thank you. I’ve read some materials that state it is determined based on the design documents. But which standards are the design documents based on? Which provision? As per the regulations, technical discussions are held with the manufacturers, and these decisions are made based on decades of engineering experience. So, what exactly is engineering experience? There has to be some basis, right? The lining serves as an anti-corrosion layer and does not contribute to strength; the strength is primarily provided by the glass fiber reinforced plastic structure layer. But what is the appropriate thickness for this lining layer? What is the basis? There’s also a lined pump here; take a look at this text – do you know what thickness is appropriate? Requirements for the thickness of the lining layer in fluorine-lined chemical pumps: According to the standards set by foreign pump manufacturers, the thickness of the lining layer in plastic-lined chemical pumps is generally 3–5 mm. If the lining is too thin (e.g., 1.5–2 mm), local defects in the lining can occur during the pressing process, which reduces the pump’s allowable operating temperature and service life. It also increases the likelihood that the lining layer will separate from the metal substrate of the pump body and rear cover. The lining layer can be secured by using densely arranged annular dovetail grooves on the base metal, which ensures a firm fixation of the lining layer while requiring minimal machining. It is also possible to use a method of arranging numerous small holes (or threaded holes) on the base metal; however, the lining layer is not as firmly fixed as with dovetail grooves, and more machining is required. To prevent non-metals from falling off or cracking the pump casing due to temperature changes, it is possible to weld scale-proof mesh to the centrifugal pump casing, thereby allowing plastic-lined pumps to be manufactured in larger sizes, with an inlet diameter of up to ф600mm.