Vessel material is SA53B or SA106B steel. Good for up to 750°F (399°C) operating temperature. Optional Heating source—1-1/4" and 2-1/2" Screw Plug Heaters are used on smaller units. 3" to 14" size heaters use Flanged Immersion Heaters. The flanges are made from forged steel rated for 150 lbs with raised face. Optional stainless steel flanges or 300 lb ratings are available. Various element sheath materials are available for maximum corrosion resistance to the medium being processed. On smaller circulation units with screw plug heaters, the element diameter is .315" or .475". On larger units with flanged heaters, the element diameter is .475".