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Screw Plug Heaters/ Screw-Plug Immersion Heaters:

Industrial Heaters for Storage Tanks, Asphalt Plants, Sewage Processing/Recycling/Water Purification, Oil Heating Loops, Caustic Solutions 
Screw-Plug Immersion Heaters with General Purpose & Nema 4 Enclosures- Industrial Process/Tank Heaters

Product Description Guide and Construction-Screw-Plug Immersion Heaters:

A Screw Plug Immersion Heater can have from 1 to 3 tubular elements, or blades, either welded or brazed into the screw plug. Screw plug immersion heaters consist of hairpin bent tubular elements brazed or welded into a screw plug and provided with terminal boxes for electrical connections. Screw plug immersion heaters are screwed directly through a threaded opening in a tank wall or through matching pipe coupling, half coupling or welding flange. Sizes of screw plug heaters are available with 1/2", 3/4" 1", 11/4", 2" and 21/2" pipe threads. A wide selection of screw plug sizes, kilowatt ratings, voltages, sheath materials, terminal housings, and thermostats makes these compact heaters ideal for all types of applications. Screw plug immersion heaters are used for heating liquids and gases in a variety of processes. These heaters are ideal for process water heating and freeze protection. All types of oils and heat transfer solutions can also be heated using these compact easily controlled units. The direct immersion method is energy efficient and well suited for many applications.

Applications Guide: Screw Plug Immersion Heaters
Screw-Plug Immersion Heaters-Construction Components

Screw-Plug Immersion Heaters: Specifications, Manuals, Technical Letters & Tips:

 Flanged Immersion Heaters Specifications Screw Plug Immersion Heaters Specifications-NL.pdf
 How to Extend the Life of Your Immersion Heater-2 How to Extend the Life of Your Screw Plug Immersion Heater-2.pdf
 Flanged Immersion Heaters Wiring Diagrams Screw Plug Immersion_Heaters_Wiring_Diagrams-2.pdf
 Flanged Immersion Heaters-Installation, Operation and Maintenance Instructions Screw Plug Immersion Heaters-Installation, Operation and Maintenance Manual.pdf

Screw Plug Immersion Heater - Features:

  • National Pipe Thread (NPT) screws into a mating fitting in your tank
  • Kilowatt range from low to medium (100 watts to 30 kw)
  • Easy to install into your tank
  • 1" to 2 ½" NPT available
  • Metric and custom screw plugs can be made to match existing tank connections
  • General purpose terminal enclosure (NEMA 1), weather resistant terminal enclosure (NEMA 4), and hazardous location terminal enclosure (NEMA 7), available
  • Thermocouples, thermostats, and high limit controls can be built-in surface temperature, providing longer coil life.
  • High Conductivity Elements-Filled with highest purity blends of magnesium oxide refractory (MgO) compacted to rock hard density to insure maximum thermal conductivity and maximum electrical resistance, and assure long element life.
  • Heavy Coil Construction - Watt density on the heating coil is designed for low watt density operation by increasing the coi diameter and length to give maximum coil surface area and limit coil surface temperature, providing longer coil life.

Most Common Screw Plugs:

  • Brass, Mild Steel or 316 series Stainless Steel
  • Other materials available
  • 1", 1 ¼", 1 ½", 2', and 2 ½" NPT are most common sizes
  • Other sizes or metric and British thread sizes can be made

Most Common Sheath Material:

  • Copper, Steel, Stainless Steel, Incoloy 800® & Incoloy 840®, Inconel 600®, Titanium

Other Sheath Material Also Offered:

  • Incoloy, Inconel are Inco Ltd registered trademarks.

Most Common Terminal Enclosures:

  • General Purpose NEMA1
  • Weather Resistant
  • NEMA 4, NEMA 4X, class 4
  • Hazardous Location NEMA 7

1" NPT (National Pipe Thread) Screw-Plug Heater Construction

Best Screw Plug Immersion Heaters: NPT Screw Plug Heaters

NEMA 4 and NEMA 7 -Enclosures 1.25 NPT-Built In Thermostat-SPST

NEMA 1 - 1.25 NPT-General Purpose Enclosure-No Thermostat-Single Element Design

NEMA 1 -1NPT-General Purpose Enclosre- No Thermostat

NEMA 1 -1NPT-General Purpose Enclosure-With Built In Thermosat

NEMA 1 -2 NPT-General purpose Enclosue -2 Elements-With Thermostat

NEMA 1 -2 NPT-General Purpose Enclosure-2 Elements-No Thermostat

NEMA 1 -2 NPT-General Purpose Enclosure-3 Elements-Built In Thermostat

NEMA 1 -2 NPT-General Purpose Enclosure-3 Elements-No Thermostat

NEMA 1 -2.5 NPT- General Purpose-3 Elements-With Thermostat-1 or 3 Phase Connection

NEMA 1 -1.25 NPT-General Purpose Enclosure-Built In Thermostat-Dual element Design

NEMA 4 -Enclosures-1NPT-With Built In Thermostat-SPST

NEMA 4 and NEMA 7 -Enclosures-3 Elements-Built In Thermostat- SPST-1 or 3 Phase Connection

NEMA 4 and NEMA 7 -Enclosures- 3 Elements-No Thermostat-1 or 3 Phase Connection

NEMA 4 and NEMA 7 -Enclosures-1.25 NPT-No Thermostat

NEMA 4 and NEMA 7 -Enclosures-1NPT-No Thermostat

NEMA 4 and NEMA 7 -Enclosures-2 NPT-2 Elements-No Thermostat

NEMA 4 and NEMA 7 -Enclosures-2 NPT-2 Elements-With Thermostat SPST

NEMA 4 and NEMA 7 -Enclosures-2 NPT-3 Elements-With Built In Thermostat-SPST

NEMA 4 and NEMA 7 -Enclosures-2 NPT-3 Elemets-No Thermostat

NEMA 4 and NEMA 7 -Enclosures-2.5 NPT-3 Elements- Built In Thermostat 480V-600VAC TPST

NEMA 1 -2.5 NPT-General Purpose-No Thermostat-3 Elements-1 or 3 Phase Connection

Safe operation of heaters equipped with these enclosures depends on employment of electrical wiring meeting National Electric Code and limiting maximum operating temperatures (including temperatures on outside of vessel, piping, flanges, screw-plugs, enclosures and other heat conducting parts) as dictated by flammable liquids, vapors, or gases present. Approved pressure and/or temperature limiting controls must be used to assure safe operation in the event of system malfunction.

Common Nema Enclosure Types

NEMA 1 - General purpose indoors. Basic enclosure intended to prevent accidental contact with internal electrical components. Suitable for use indoors where not subjected to unusual conditions.

NEMA 4 - Watertight and dusttight indoors or outdoors. Designed to exclude water applied in the form a hose stream. Also suitable where apparatus may be subjected to a stream of water during cleaning operations.

NEMA 4x - Watertight, dusttight, and corrosion resistant - indoors or outdoors. Protects internal components against splashing water, falling or hose directed water, and severe external condensation. Sleet resistant. Corrosion resistant material or finish.

NEMA 7 - Explosion resistant in hazardous class 1 locations (areas where flammable gases or vapors are or may be present in quantities to produce explosive conditions or fire).

NEMA 12 - Dusttight and driptight indoors. Enclosures are designed to protect internal components from fibers, lint, dust, dirt and light splashing, and dripping of non-corrosive liquids.
Terminal Enclosure Types - General purpose, sheet metal, (NEMA-1) painted with enamel. Moisture Resistant-Nema 4, Nema 4X, Explosion Proof Nema 7.
Grounding Connector Standard - A solid terminal connector is standard on all NPH immersion heaters insuring positive ground and personal safety.

Built In Thermocouple Options:

  • "K" calibration thermocouple for high limit sheath protection
  • "J" calibration thermocouple for temperature control

Built In Thermostats:

Power Ratings:
  • Up to 240 volts, 25-amp single pole, single throw (SPST)
  • Up to 240 volts, 25-amp double pole, single throw (DPST)
  • Up to 600 volts, 15-amp triple pole, single throw (TPST)

Temperature Ranges:

  • 16 to 40°C (0-100°F),
  • 10 to 10°C (50-250°F),
  • 70 to 280°C (160-540°F),
  • 160 to 370°C (320-700°F)

Listed below are some of the recommended watt densities to heat various fluids and gases:

(a) 90, 60 & 45 Watts/Square InchFor industrial water heating of many acqueous solutions which accept heat easily.(b) 23 Watts/Square InchIndustrial process heating of many light oils and cooling fluids for some corrosive solutions along with air and gas heating.(c) 15 & 12 Watts/Square InchFor industrial heating of medium viscosity oils, high temperature air and gas heating.(d) 8 Watts/Square InchFor heating of #5 and #6 fuel oil, viscous materials, raw crude oil and residual oils(e) 6 Watts/Square InchFor heating #6 fuel oil, very viscous materials and fluids that do not accept heat readily.

Specifications, Manuals, Technical Letters & Tips:

Construction-Flanged Immersion Heaters ( Or have above a link to new page) Screw Plug Immersion Heaters Specifications.pdf How to Extend the Life of Your Immersion Heaters-2.pdf Screw Plug Immersion_Heaters_Wiring_Diagrams-2.pdf Screw Plug Immersion Heaters-Installation, Operation and Maintenance Instructions.pdf

Applications Guide: Screw Plug Immersion Heaters

  • Hot Water Storage Tanks,
  • Warming Equipment,
  • Heating & Preheating All Grades of Oil
  • Food Processing Equipment,
  • Food Processing Equipment,
  • Cleaning and Rinsing Tanks
  • Heat Transfer Systems,
  • Process Air Equipment,
  • Boiler Equipment,
  • Petro-Chemical
  • Freeze Protection of Fluids,
  • Sewage Processing/Recycling/Water
  • Purification
  • Oil Heating Loops,
  • Caustic Solutions

National Plastic Heater Corrosion Policy:

NPH cannot warrant any electric immersion heater against failure by sheath corrosion if such failure is the result of operating conditions beyond the control of the heater manufacturer. It is the responsibility of the purchaser to make the ultimate choice of sheath material based on his knowledge of chemical composition of corrosive solution, character of materials entering the solution, and controls which he maintains on the process. * Not intended for use in hazardous locations.

 Construction Components-Screw Plug Immersion Hetaers

How To Order Screw Plug Immersion Heaters

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