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Over-the-Side Immersion Heaters

Over-the-side immersion heaters are designed for tanks where it is not convenient to install a flanged or screw-plug immersion heater through the side wall. These heaters offer easy installation and the ability to move the heater from tank to tank, without having to drain the liquid. Over-the-side immersion heaters are ideal for applications where scale or sludge build-up on the heater sheath is an issue and heaters should be removed periodically for cleaning. Over-the-side immersion heaters are installed from the top and are available in two versions; units that have the heated section at the bottom of a tank (Type OTSL & OTSR) or along the side wall (Type OTSH).

Over The Side Immersion Heater

Typical Heating Applications of Over the Side Immersion Heaters:

  • Hydraulic Oils
  • Alkaline Cleaning Solutions
  • Oils, Including Light to Heavy
  • Water & Water Based Solutions
  • De-mineralized or De-ionized Water
  • Solutions that Precipitate, such as Phosphates
  • Tall storage tanks with a top opening as the only installation option

Bottom-of-the-tank heaters

Two designs are available

  • Type OTSL "L" shaped heaters for rectangular tanks
  • Type OTSR, circular heaters for round tanks or for applications where the heater will be

installed through a manhole cover

The basic construction includes rugged tubular elements that are welded or brazed into a lower terminal box. The power wires come up through a non-heated vertical riser-pipe into a moisture resistant (NEMA 4) terminal box. The tubular elements are mounted in multiples of 3 for a balanced 3-phase load. Heater banks can be added for higher kilowatt output. Sheath material selection (Steel, Copper, Incoloy, Stainless Steel or other special alloys) is based on design parameters.

Bucan technical staff will help you select the optimum watt density and sheath material to suit your specific needs.

"L" Shape

For rectangular tanks 40-50 watts/in2

KW "B" Dim. (in) Copper Sheath Stainless Steel Sheath Incoloy Sheath
3 12 OTSLC30312 OTSLS30312 OTSLI30312
6 22 OTSLC30622 OTSL30622 OTSLI30622
9 30 OTSLC30930 OTSL30930 OTSLI30930
12 38 OTSLC31238 OTSL31238 OTSLI31238
15 46 OTSLC31546 OTSL31546 OTSLI31546
18 53 OTSLC31853 OTSL31853 OTSLI31853

"L" Shape

For rectangular tanks 20-25 watts/in2

KW "B" Dim. (in) Steel Sheath Incoloy Sheath
1.5 12 OTSLF301512 OTSLI301512
3.0 22 OTSLF30322 OTSLI30322
4.5 30 OTSLF304530 OTSLI304530
6 38 OTSLF30638 OTSLI30638
7.5 46 OTSLF307546 OTSLI307546
9 53 OTSLF30953 OTSLI30953

Circular Shape

For round tanks or openings 40-50 watts/in2

KW "B" Dim. (in) Copper Sheath Stainless Steel Sheath Incoloy Sheath
3 9.75 OTSRC30309 OTSRS30309 OTSRI30309
6 13 OTSRC30613 OTSRS30613 OTSRI30613
9 15.5 OTSRC30915 OTSRS30915 OTSRI30915
12 18 OTSRC31218 OTSRS31218 OTSRI31218
15 20.5 OTSRC31520 OTSRS31520 OTSRI31520
18 23.75 OTSRC31823 OTSRS31823 OTSRI31823

Circular Shape

For round tanks or openings 20-25 watts/in2

KW "B" Dim. (in) Steel Sheath Incoloy Sheath
1.5 9.75 OTSRF301509 OTSRI301509
3.0 13 OTSRF30313 OTSRI30313
4.5 15.5 OTSRF304515 OTSRI304515
6 18 OTSRF30618 OTSRI30618
7.5 20.5 OTSRF307520 OTSRI307520
9 23.75 OTSRF30923 OTSRI30923

Side-wall heaters (Single Phase)

Type OTSH Over-the-side heaters have a rectangular form and are made for open tank applications. These heaters are lightweight, thin-profiled and are designed to hang on the tank wall in order to save space. Weather/moisture proof (NEMA 4) terminal boxes are standard. These heaters can be made with a single element (single-phase) or with three elements (three phase). Different sheath materials are available.

KW Watt Density Sheath Material
Incoloy® Inconel® Stainless Steel Titanium Weight (lb)
3 18 OTSHI03 OTSHN03 OTSHS03 OTSHT03 9
5 30 OTSHI05 OTSHN05 OTSHN05 OTSHT05 9
7.5 45 OTSHI07 OTSHN075 OTSHN075 OTSHT075 9

Side-wall heaters (Three Phase)

Specialy designed to hang on the tank lip. 3 elements single or 3 phase. Specify voltage and phase when ordering.

KW Watt Density Sheath Material
Incoloy® Inconel® Stainless Steel Titanium Weight (lb)
9 18 OTSHI09R OTSHN09R OTSHS09R OTSHT09R 9
15 30 OTSHI15R OTSHN15R OTSHN15R OTSHT15R 9
22.5 45 OTSHI1225R OTSHN1225R OTSHN1225R OTSHT1225R 9

Accessories of Over the Side Immersion Heaters

  • Vertical riser can be made in any height
  • Hazardous Location (NEMA 7) terminal enclosures
  • Passivation - when required
  • Special fitting for closed top
  • Built-in thermostats, thermocouples, and high limit thermocouples

Installation and Maintenance

  • Electric heaters must be installed by qualified personnel in accordance with all national and local electric codes.
  • The supply electric power should match the nameplate voltage and wattage.
  • The heated section of the heater should be fully immersed in the liquid when the heater is energized.
  • Sludge build-up on the element sheath may damage the heater; special legs should be installed to keep the heater above the tank bottom, and the heater should be periodically inspected and cleaned if necessary.
  • The standard terminal box is weather/moisture proof (NEMA 4). Periodically, the electrical connections should be inspected for tightness and the interior of the terminal box checked to make sure that it is clean.

Features of Over the Side Immersion Heaters

  • Special sheath materials - selected to suit the liquid or gas being heated
  • Special flange on the riser for gas heating applications
  • Vertical riser made in any height
  • Sludge legs, to raise the heater elements above the tank bottom
  • Hazardous location (NEMA 7) terminal enclosures
  • Passivation - when required
  • Special fittings for closed top
  • Built-in thermostats, thermocouples, and/or high-limit thermocouples