The most commonly selected Chromalox immersion heaters for industrial tanks are screw plug heaters for compact and moderate-load applications, flanged heaters for larger or higher-capacity vessels, and over-the-side heaters for open tanks without permanent mounting connections. The correct product family depends primarily on the tank size, process liquid, required kilowatts, watt density, mounting method, pressure, and maintenance access.
Table of Contents
The Most Common Chromalox Tank-Heater Options Chromalox Screw Plug Immersion Heaters Chromalox Flanged Immersion Heaters Chromalox Over-the-Side Immersion Heaters Removable-Element Immersion Heaters Best Options for Clean-Water Tanks Process Water and Corrosive Solutions Oil and Viscous-Fluid Tanks Chromalox Pick & Ship Immersion Heaters How to Select the Correct Tank Heater Controls and Safety Protection Frequently Asked Questions Chromalox Immersion Heaters from Big ChiefThe Most Common Chromalox Tank-Heater Options
Chromalox manufactures immersion heaters for direct heating of water, oils, viscous fluids, corrosive solutions, gases, and other industrial process media. For tank heating, the most frequently considered mounting styles are screw plug, flanged, and over-the-side assemblies.
Each style fills a different need:
- Screw plug heaters: Compact threaded assemblies for smaller tanks, reservoirs, pipelines, and moderate heating loads.
- Flanged heaters: Larger element bundles for high-capacity tanks, process vessels, and pressure-rated systems.
- Over-the-side heaters: Removable heaters that enter through the top of an open tank without requiring a threaded or flanged wall connection.
- Removable-element heaters: Serviceable assemblies that allow heating elements to be changed without replacing every part of the flange assembly.
“Most popular” should not be interpreted as one universal best-selling model. Chromalox organizes its immersion-heater range around fluid type, mounting style, watt density, materials, electrical rating, and service conditions. The most appropriate product is the one designed for the actual tank and process.
Chromalox Screw Plug Immersion Heaters
Screw plug immersion heaters are among the most common choices for small and medium industrial tanks. Hairpin-bent tubular elements are attached to a threaded plug that screws directly into a compatible tank coupling or pipe fitting.
They are widely used because they provide:
- Compact installation
- Simple threaded mounting
- Multiple sheath-material options
- Standard voltage and wattage combinations
- Models with or without integral thermostats
- Several terminal-enclosure options
- Relatively straightforward replacement
Typical applications include:
- Water-storage tanks
- Wash and rinse tanks
- Oil reservoirs
- Boiler and preheating equipment
- Small chemical tanks
- Heat-transfer-fluid systems
- OEM machinery
- Small circulation chambers
Chromalox screw plug families are offered for clean water, process water and corrosive solutions, and oils or non-corrosive viscous fluids. These categories differ in sheath construction, watt density, plug material, thermostat options, and allowable service conditions.
When Screw Plug Heaters Are the Best Choice
A screw plug heater is usually the practical option when the tank already includes a compatible threaded coupling and the required heating capacity fits within the available plug size. It is also useful when compact installation and lower replacement cost are priorities.
The main limitation is the amount of element surface area that can fit through the threaded opening. As kilowatt requirements increase, concentrating more power into the same compact bundle can raise watt density beyond what the fluid can safely absorb.
Chromalox Flanged Immersion Heaters
Flanged immersion heaters are one of the most widely applied options for larger industrial tanks and process vessels. Multiple tubular elements are mounted to a plate or pipe flange that bolts to a matching connection on the tank.
The larger opening accommodates more elements and greater heated surface area than a typical threaded plug. This allows flanged assemblies to support:
- Higher total kilowatt loads
- Longer element bundles
- Lower watt density
- Multiple electrical circuits or stages
- Larger thermowells and control sensors
- Pressure-rated vessel connections
- Custom element and enclosure configurations
Flanged Chromalox heaters are commonly used in:
- Large water tanks
- Pressurized process vessels
- Oil-storage systems
- Chemical-processing tanks
- Thermal-fluid equipment
- Food-processing systems
- Power-generation facilities
- Circulation and inline heating systems
A flanged heater generally requires more installation space and maintenance labor than a screw plug assembly. The vessel must include a matching flange, compatible gasket, correct bolt pattern, and enough clearance to withdraw the complete element bundle.
When Flanged Heaters Are the Best Choice
Flanged heaters are usually preferred when the tank needs substantial heating capacity, when the process requires a low watt density, or when a pressure-rated flange is already part of the vessel design.
They are also a better platform for engineered applications involving corrosive solutions, hazardous locations, staged heating, multiple circuits, specialized materials, or independently mounted controls.
Chromalox Over-the-Side Immersion Heaters
Over-the-side immersion heaters are installed through the open top of a tank. The heating elements extend down the side or across the bottom while the terminal enclosure remains above the liquid level.
This configuration is especially useful when:
- The tank lacks a threaded coupling or flange.
- Drilling or welding the vessel is impractical.
- The heater must be removed frequently for cleaning.
- The tank is open at the top.
- Temporary or portable heating is required.
- Working space inside the tank must remain available.
Chromalox offers metal-sheath, fluoropolymer-covered, quartz-tube, and other application-specific over-the-side constructions. Available materials allow the heater to be matched to water, plating solutions, acids, alkalis, and other industrial liquids.
Typical applications include:
- Plating tanks
- Cleaning and degreasing tanks
- Rinse tanks
- Open water tanks
- Pickling and chemical-treatment tanks
- Pilot and temporary process systems
The element must remain adequately immersed while energized. Tank level, mounting position, sludge accumulation, and liquid movement should be reviewed before installation.
When Over-the-Side Heaters Are the Best Choice
Over-the-side heaters are often the simplest option for retrofitting an open tank that does not have a permanent heater connection. They also make inspection and cleaning easier because the complete assembly can be lifted from the vessel after power is isolated and the heater has cooled.
They are less suitable for sealed or pressurized vessels and may require mounting brackets or guards to protect the elements from impact, movement, and contact with tank contents.
Removable-Element Immersion Heaters
Some Chromalox flanged immersion-heater assemblies use replaceable or removable heating elements. This construction can reduce maintenance cost when individual elements eventually fail but the flange, enclosure, and remaining assembly are still serviceable.
Removable-element designs can be useful when:
- The heater operates in a critical process.
- Long-term serviceability is important.
- The assembly contains multiple heating elements.
- Replacing the complete flange would be costly.
- The application permits safe access for element replacement.
- Spare elements can be stocked for maintenance.
Some designs incorporate elements installed within thermowells, allowing service without exposing the electrical element directly to the liquid. The exact maintenance procedure depends on the heater construction and vessel design.
Removable elements do not eliminate the need to review the root cause of a failure. Scale, corrosion, dry firing, loss of flow, incorrect voltage, or failed controls can damage replacement elements if the operating problem remains unresolved.
Best Options for Clean-Water Tanks
For clean-water tanks, screw plug and flanged heaters are the two most common starting points. The mounting style depends mainly on required kilowatts and tank construction.
Clean-Water Screw Plug Heaters
Clean-water screw plug heaters are well suited to smaller hot-water tanks, wash systems, reservoirs, boiler-support equipment, and OEM water-heating applications. Copper, stainless steel, or other sheath options may be available depending on the product and water conditions.
Choose this style when:
- The tank includes a suitable threaded coupling.
- The required wattage fits within the available plug size.
- The system operates at moderate pressure and capacity.
- Compact and economical replacement is important.
Clean-Water Flanged Heaters
Clean-water flanged heaters are better suited to large storage tanks, pressure vessels, commercial water-heating equipment, and systems that require greater element surface area or higher capacity.
Choose this style when:
- The tank requires a larger kilowatt load.
- The vessel already has a flange connection.
- Multiple heating stages are needed.
- Lower watt density is preferred.
- The system requires a pressure-rated assembly.
Water quality still matters. Hardness, chlorides, dissolved minerals, sediment, operating temperature, and treatment chemicals can affect scale formation and sheath life even in an application described as clean water.
Process Water and Corrosive Solutions
Process water and chemical solutions may require stainless steel, Incoloy®, titanium, fluoropolymer, quartz, or another material selected for the specific liquid. Chromalox offers screw plug, flanged, and over-the-side configurations for these applications.
Chromalox MTS and related screw plug families use stainless steel elements for process-water and corrosive-solution applications. MTI and related models use Incoloy elements for compatible solution-water and corrosive services. Available variants may include integral thermostats and different terminal enclosures.
Selection should account for:
- Chemical composition
- Concentration
- Normal and maximum temperature
- Contaminants
- Chloride content
- Flow or agitation
- Potential for crystallization or deposits
- Tank and gasket materials
- Hazardous-location requirements
The heater sheath is not the only wetted component. The screw plug, flange, thermowell, gasket, welds, and tank connection must also be compatible with the solution.
For open chemical tanks that lack a permanent connection, an over-the-side heater may be easier to install and service. Highly aggressive fluids may require a fluoropolymer-covered or quartz construction rather than an exposed metal sheath.
Oil and Viscous-Fluid Tanks
Oil and viscous fluids generally require lower watt density than clean water because they do not carry heat away from the element as quickly. Excessive sheath temperature can carbonize oil, create deposits, degrade the fluid, and shorten heater life.
Chromalox offers screw plug, flanged, and removable-element heaters configured for oils and non-corrosive viscous fluids.
Important design factors include:
- Oil type and viscosity
- Cold-start temperature
- Maximum allowable film temperature
- Required heat-up time
- Tank circulation or agitation
- Element watt density
- Potential for sludge or carbon deposits
- Operating and high-limit temperatures
Flanged heaters are often advantageous for large oil tanks because the larger element bundle distributes the required kilowatts across more sheath surface. Screw plug heaters remain useful for small reservoirs, hydraulic systems, lubricating-oil tanks, and equipment sumps when the load is moderate.
Increasing wattage without increasing heated surface area is rarely the best way to improve oil heat-up time. Better circulation, insulation, staged heating, or a larger low-watt-density bundle may provide more reliable performance.
Chromalox Pick & Ship Immersion Heaters
Chromalox Pick & Ship products are preconfigured immersion heaters intended to cover common industrial applications with shorter product-selection and delivery timelines than a fully custom-engineered assembly.
Pick & Ship options include screw plug and flanged configurations for common watt densities, voltages, and process categories. Chromalox’s Pick & Ship flanged line includes configurations reaching up to approximately 58 kW and covers several commonly used watt-density ranges.
These products are useful when:
- The application fits a standard configuration.
- A replacement is needed without a custom design cycle.
- Common voltage and phase requirements apply.
- The process medium matches the heater’s intended service.
- Standard flange, enclosure, and element options are acceptable.
A stocked or preconfigured heater should not be selected merely because it is available quickly. The watt density, sheath material, insertion length, voltage, flange or thread connection, pressure, enclosure, and process fluid must still match the application.
How to Select the Correct Tank Heater
Start with the process requirements before choosing a specific Chromalox family or model.
- Identify the liquid. Record the fluid, concentration, contaminants, viscosity, and compatibility requirements.
- Calculate the heat load. Include tank volume, temperature rise, heat-up time, incoming material, and continuous losses.
- Select the mounting style. Determine whether the tank uses a threaded coupling, flange, open top, or another connection.
- Establish watt density. Match element surface loading to the liquid, circulation, temperature, and deposit potential.
- Choose wetted materials. Verify the sheath, plug or flange, thermowell, gasket, and other wetted components.
- Confirm dimensions. Check insertion length, tank clearance, liquid level, sludge depth, baffles, coils, and agitators.
- Review electrical service. Confirm voltage, phase, available amperage, number of circuits, and control-panel capacity.
- Check pressure and location ratings. Account for vessel pressure, enclosure requirements, moisture, corrosion, and hazardous-area classifications.
- Plan maintenance access. Provide enough space to remove the complete element bundle and service the enclosure.
- Select controls and protection. Include process control, high-limit protection, low-level cutoff, and flow interlocks where required.
A standard screw plug heater may be ideal for one tank, while a flanged or custom assembly may be necessary for another tank containing the same liquid. Tank size, mounting, pressure, heat load, and maintenance conditions determine the difference.
Controls and Safety Protection
An industrial tank heater requires more than an element bundle. Controls and safety devices regulate normal temperature and protect the heater if process conditions become unsafe.
A complete system may include:
- A thermostat or electronic temperature controller
- An RTD or thermocouple
- An independent high-limit controller and sensor
- A low-liquid-level cutoff
- A flow switch for circulation systems
- A contactor, SSR, or SCR power controller
- Overcurrent and ground-fault protection
- Alarms and remote monitoring
The active heated length must remain covered by the intended fluid whenever the heater is energized. An exposed element can overheat rapidly because air and vapor do not remove heat as effectively as liquid.
The high-limit circuit should operate independently from the normal temperature-control loop where a single control failure could damage the heater, tank, or process. Low-level and loss-of-flow devices should interrupt heater power rather than only notify an operator.
Frequently Asked Questions
Which Chromalox immersion heater is best for an industrial tank?
Screw plug heaters are usually best for compact tanks and moderate loads, while flanged heaters are better for large tanks, high kilowatt requirements, pressure vessels, and applications requiring more element surface area.
Which Chromalox immersion heater is best for clean water?
Clean-water screw plug and flanged heaters are common choices. The correct style depends on tank size, required wattage, mounting connection, pressure, heat-up time, and maintenance access.
Which immersion heater should be used for oil?
Use a heater designed for oil or non-corrosive viscous fluids with watt density low enough to control sheath and film temperature. Flanged bundles are often appropriate for larger oil tanks, while screw plug heaters work well in smaller reservoirs.
When should an over-the-side immersion heater be used?
Over-the-side heaters are useful for open tanks that lack a threaded coupling or flange, or where the complete heater must be removable without permanently modifying the vessel wall.
Are Pick & Ship heaters suitable for every tank?
No. They are intended for applications that fit the available standard configurations. Fluid compatibility, watt density, voltage, connection size, insertion length, pressure, enclosure, and controls must still be verified.
Can one Chromalox heater be used for water, oil, and chemicals?
Not generally. These fluids may require different sheath materials, watt densities, seals, mounting arrangements, and controls. The heater should be selected specifically for the process medium and operating conditions.
Chromalox Immersion Heaters from Big Chief
Big Chief helps industrial facilities compare Chromalox tank heaters based on the process liquid, tank size, temperature rise, heat-up time, mounting connection, watt density, sheath material, pressure, electrical service, enclosure, and maintenance requirements. This application-based approach helps determine whether the tank needs a standard screw plug heater, a larger flanged bundle, a removable over-the-side assembly, or a custom-engineered solution.
For replacement or new-equipment selection, provide the existing Chromalox model or PCN, nameplate photographs, tank dimensions, thread or flange information, element length, voltage, phase, wattage, process fluid, operating temperature, pressure, controls, and failure history. These details improve cross-reference accuracy and help determine whether the original heater should be duplicated or revised for better performance.
