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Tank Heaters
Over-the-Side Immersion Heaters
Hooked over the tank rim with no penetration, no drilling and no welding. The standard answer for an existing plating, pickling or cleaning tank that has to keep running.
What it is
An over-the-side heater has a vertical riser section that clears the tank wall and a horizontal heated section that sits down in the liquid. The terminal housing stays above the rim, outside the tank, where it stays dry and serviceable. Nothing is cut into the tank.
Because the element hangs rather than threads in, you can lift it out for cleaning, move it between tanks, and raise or lower the heated section to keep it clear of sludge on the tank bottom. That last point matters more than most buyers expect — an element buried in settled solids overheats and fails, and it will do it in weeks rather than years.
When it is the right choice
- The tank cannot be drilled. Lined tanks, poly tanks, rented tanks, or tanks under a coating warranty.
- The tank is already in service. No shutdown to cut and weld a coupling or flange nozzle.
- The liquid is aggressive. A hanging element in PTFE or titanium is far easier to replace than a through-wall fitting that is leaking acid.
- Sediment collects on the bottom. The heated section can be positioned above the sludge line.
- You need it in more than one tank. One heater, several tanks, moved as needed.
When to choose something else
Over-the-side heaters are usually the wrong pick above roughly 24 kW in a single unit, in a pressurized or closed vessel, or where the tank is covered and there is no rim access. For those, look at flange immersion heaters or an external circulation heater.
Specifications
Standard build ranges. Outside these, see custom engineered systems.
| Specification | Range or option |
|---|---|
| Rating per unit | 1 kW to 24 kW |
| Voltage | 120 V, 208 V, 240 V, 277 V, 480 V, 600 V |
| Phase | Single phase or three phase |
| Sheath materials | 316 stainless steel, 304 stainless steel, PTFE-coated steel, titanium, quartz, Incoloy 800, carbon steel, Monel |
| Riser length | Built to clear your tank wall — specify rim height to liquid level |
| Heated length | Built to your tank width, positioned above the sludge line |
| Element geometry | L-shape (single leg), J-shape, or multi-leg hairpin |
| Terminal enclosure | NEMA 1 general purpose, NEMA 4X moisture and corrosion resistant, NEMA 7 hazardous location |
| Thermal protection | Over-temperature thermostat, low-liquid-level cutoff, RTD or thermocouple for external control |
| Mounting | Rim hook, tank-lip bracket, or bolt-down bracket |
Sheath material by tank chemistry
The sheath is the part that touches the liquid, and it is the single decision that determines whether the heater lasts years or months. Full detail on the sheath material guide.
| Tank liquid | Typical sheath | Typical max watt density |
|---|---|---|
| Clean water, rinse water | 316 stainless steel or Incoloy 800 | Up to 60 W/in² |
| Alkaline cleaners, caustic soda | 316 stainless steel, nickel-plated | 30 – 45 W/in² |
| Nickel, zinc, copper plating baths | PTFE-coated steel or titanium | 25 – 45 W/in² |
| Chromic acid, chrome plating | Titanium or PTFE-coated | 25 – 40 W/in² |
| Sulfuric acid, dilute | PTFE-coated steel or quartz | 20 – 30 W/in² |
| Hydrochloric acid, pickling | PTFE-coated steel or quartz | 20 – 30 W/in² |
| Hydrofluoric acid | Quartz | 20 – 25 W/in² |
| Phosphate and phosphoric baths | PTFE-coated steel or 316 stainless | 25 – 35 W/in² |
| Light oils, solvent degreasers | Carbon steel or 316 stainless | 20 – 25 W/in² |
| Heavy oils, wax, tar | Carbon steel | 5 – 10 W/in² |
These are industry guideline values for typical concentrations and temperatures. Concentration, temperature and contaminants all shift the answer, so confirm the selection against your actual bath analysis before ordering.
Common questions
Can an over-the-side heater go into a tank that is already full and running?
Yes. That is the main reason they exist. The heater hooks over the rim and the heated section drops into the liquid, so no drilling, welding or draining is required. Verify you have the voltage available at the tank and enough clearance above the rim for the terminal housing.
How far off the tank bottom should the element sit?
Enough to stay clear of settled solids, and enough that the element is always fully submerged at your lowest working level. In a plating or cleaning tank that drops sludge, several inches of clearance is normal. An element that runs partly dry or sits in sludge will fail from local overheating, not from the electrical load.
What happens if the liquid level drops below the element?
The element overheats almost immediately, because the liquid is what carries the heat away. This is the most common cause of premature failure. Specify a low-liquid-level cutoff on any tank that can be pumped down, evaporate significantly, or be drained by someone who is not thinking about the heater.
Can one heater serve two tanks?
Physically yes, if the tanks have compatible chemistry and similar geometry, and you are willing to move it. Practically, moving a live electric heater between tanks introduces handling and disconnect issues. If both tanks need heat at the same time, quote two units.
Do you supply the controls too?
Yes. Contactor panels, temperature controllers, over-temperature limits, and liquid level cutoffs are quoted with the heater. See voltage and controls.
Send tank dimensions, get a heater built to them
Inside dimensions, liquid, volume, target temperature, and the voltage you have at the tank. That is enough to quote an over-the-side heater.