Series L4 | FLOTECT® Float Switch operates to indicate tank level. No bellows, springs, or seals to fail. Applications include level and valve control, automatic tank dump operations, and direct pump control.
Source sus explosion-proof vertical mul-piont float level switch on m.alibaba.com
Magnetic float level switch - TK1 - MINV - for liquids / for tanks / stainless steel
APG FS-410 Stainless Steel Vertical Float Switch - Intrinsically Safe Store