Screw Plug Immersion Heaters
Screw Plug Immersion Heaters consist of hairpin bent tubular elements brazed or welded into a screw plug and provided with terminal enclosures for electrical connections. Screw Plug Immersion Heaters are screwed directly through a threaded opening in a tank wall or through a matching pipe coupling or half coupling. Sizes of screw plug heaters are available with 1/2, 3/4, 1, 1-1/4, 2 and 2-1/2″ pipe threads. A wide selection of screw plug sizes, kilowatt ratings, voltages, sheath materials, terminal enclosures and thermostats makes these compact heaters ideal for all types of applications.
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.
· Hot Water Storage Tanks
· Warming Equipment
· Preheating all Grades of Oil
· Food Processing Equipment
· Cleaning and Rinsing Tanks
· Heat Transfer Systems
· Process Air Equipment
· Boiler Equipment
· Freeze Protection of Any Fluid
Technical & Application Data
Description
Heavy duty tubular elements are welded or brazed to a screw plug. Uniform heat distribution and repressed element bends lead to long element life. For all heaters, a thermowell (hollow tube sealed at one end) is welded or brazed to the screw plug allowing thermostat sensing element replacement without draining the tank. A variety of methods of terminating power leads is available for special application heaters.
General purpose screw plug heaters are equipped with a steel terminal enclosure painted with red enamel. These same heaters are also available with a combination moisture tight/explosion resistant terminal enclosure that may be used in applications where either or both conditions exist. Screw plug type heaters are screwed directly through a threaded opening in the tank wall. Heavy tank walls may be drilled and tapped if thickness is sufficient to engage 3/4 of the threads. Lighter tank walls should be equipped with a suitable pipe half-coupling welded or brazed to the tank wall.
Construction Features – Stock & Assembly Stock Units
Element
Materials — copper, steel, INCOLOY ® , 304 stainless steel
Number Elements in Screw Plug — 1, 2 or 3 depending on screw plug size
Element Diameter — 0.315, 0.375, 0.430 and 0.475″
Watt Density — 6.5, 15, 23, 45 and 75 W/In 2
Screw Plug
Materials — carbon steel, brass, 304 stainless steel
Size — 1/2, 3/4, 1, 1-1/4, 2, 2-1/2″ NPT nominal
Tolerances — Tolerance on immersion length (B) dimension is ± 1% ( ± 3/8″ min.)
Terminal Enclosures
- General purpose, sheet metal, painted with red enamel. The terminal enclosure rotates 360 ° to accommodate an electrical conduit run.
- Moisture resistant housing.
- Combination moisture resistant/ explosion resistant.
- Explosion resistant enclosures are for use in hazardous location conditions:
Class I Groups B, C & D, Division 1 & 2
Class II, Groups E, F & G, Division 1 & 2
Class III, Division 1 & 2
Safe operation of heaters equipped with explosion resistant enclosures depends on electrical wiring meeting the National Electrical
Code for hazardous locations and on limiting the 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 a system malfunction.
Temperature Controls
Many screw plug type heaters are available with built-in thermostatic controls. In some installations where there is more than one heater in a tank, one heater with a built-in control can be used to control the other heaters by wiring the thermostat into the holding coil circuit of a magnetic contactor. If the thermostat is separate from the heater, the thermostat sensing element should be located in the liquid approximately 4 to 6 inches above the heater.
Note — The integral thermostat functions as a temperature control only. This is not a fail safe device, so an approved pressure and/or temperature limit control should be used with these heaters to assure safe operation.
CAUTION — Explosion Resistant construction refers to heater design features which provide explosion resistant containment of electrical wiring according to National Electrical Code. Application or use of heaters which result in abnormal or excessive temperature can create hazardous conditions which can lead to a fire or explosive condition.
