This may help
Polypropylene (PP) was developed in the 1970’s since then it has become a standard material used in chemical applications. It can be fabricated into different size tanks and can handle solutions up to 190°F. The larger tanks with high solution temperatures and “wave action” from parts on hoists create an increased possibility of tank failure.
Immersion heaters used in Polypro can range from just about any heater (Over-the-side, L-shaped or bottom, Screw-plug or screw-in, flanged) we manufacture. Temperature control and liquid level sensors are a Must-Have in any plastic or Plastic lined tank. If there is tank failure, solution evaporation, pump hose evacuating the tank, or a faulty drain valve then the level safety device will shut the heater off safely.
190 f is about 85 degrees c so setting to 65 c is well within a safety margin - although I doubt anyone has a water level switch an immersion element blows almost instantly if exposed to air
Darran