When it comes to linear polyethylene, cross-linked polyethylene, and FRP tanks, none of these materials are better than the others but each material has its proper application.
Whether it be linear (LLDPE or HDPE) or cross-linked (XLHDPE), polyethylene is a very abrasion and chemically resistant material. The shortcoming is that polyethylene, in general, is not a strong material by comparison to FRP or various metals. Polyethylene also has a lower maximum temperature threshold compared to FRP or metal tanks. However, polyethylene is generally less expensive.
In smaller size tanks, the cost savings can be substantial while still realizing the same, or better service life. Linear polyethylene has a 120°F maximum temperature limit and 150°F maximum for XLPE.
The typical lead time is 4-6 weeks after drawing approval.
FRP (fiber reinforced plastic) tanks are typically used for larger vessels, taller and narrower vessels, and for elevated temperature applications. Where polyethylene (not being as strong as FRP) is limited to roughly a 2.5:1 height to width ratio, FRP can be as much as a 5:1 height to width ratio.
A good parallel to use is boats. You don’t see many polyethylene boats, but you see a lot of FRP boats. FRP is just stronger. FRP Tanks with certain Durakane resins can handle up to 250°F for short periods of time without softening. One important caveat is that FRP tanks do not do well with sulfuric acid. FRP is limited to 67% max, at 70°F.
There is a variation of FRP tanks called dual laminate tanks. These are special FRP tanks with a liner made of special dual laminate construction using fluoropolymer liners (PVDF, ECTFE,FEP, MFA, PFA). Dual laminate tanks are most often used for the most demanding applications such as hydroflouric acid (HF) or other extremely dangerous or comparable chemicals.
Typical FRP tank lead time is 9-12 weeks after drawing approval.
Metallic tanks are often used in applications requiring pressure ratings above atmospheric or by customer preference. For chemical applications, a wide variety of coatings and linings are available to meet almost any application.