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Screw-plug immersion resistors


The electric resistors on threaded fitting for immersion use (so called “screw-plug”) are designed for all the applications concerning the liquids or gas thermal treatment subject to static or forced convection.

They can be manufactured for use in many industrial applications for heating liquid substances.

Their typology, both for standard and non-standard models consists of heating tube bundles generally made by 1 element (single-phase type) or from 3 to 6 elements (Three-phase type) with U-folding (with parallel or “cross” layout) or folded as eyelet (1 or 2 eyelets); these elements are welded on a brass or stainless steel threaded fitting suitable for being secured to the basin to be heated wall.

Furthermore, these heaters typology can be efficiently installed on tanks and basins wall edge , in horizontal or vertical position, for the fluids direct heating intended for countless uses in the main industrial sectors.

The first quality materials use within our production cycle allows the screw-plug immersion electric resistors manufactured by us, to reach high operating temperatures and a medium-long term useful operative life.


Designed to be introduced in pipes, basins or tanks under pressure and immersed directly into contact with fluid, the electric screw-plug immersion resistors welded on threaded fitting grant an excellent heat exchange, despite their very limited overall dimensions.

In order to design an on-cap efficient immersion electric heater, the following technical parameters must be established:


The entire production cycle of industrial screw-plug electric resistors on threaded fitting is subject to the strictest dimensional checks and electric tests in compliance with the standards set forth by our own ISO 9001:2015 certified Corporate Quality System, and in full compliance with the CEI/EN requirements in force.



This heaters typology consists of a tube bundle including 1, 2, 3 or 6 heating electric elements of various diameter, with fold finishing, as follows:


This heaters typology is suitable for applications with operating pressure lower than 15 bar. In addition, in case of high working temperatures, it is suggested to use neutral cooling extension cords of the electric contacts outside the fitting in order to protect its integrity and to limit damages due to overheating in case of temperatures higher than 100°C reached inside their protection housing. The electric connections side, in fact, is included inside housings or standard Bakelite or aluminium

protections (IP40) or in die-casted and polycarbonate aluminium (IP55) or inside specific explosion-proof heads foreseen for explosive environments (IP65, IP66)

To avoid the premature damaging of this type of electric resistors, the heating section must be constantly and fully immersed in the fluid to be heated. In order to limit the overheating risk, this type of heaters can be properly equipped with efficient

Thermal regulation devices (control thermostats with adjustable temperature scale, with automatic or manual reset or, alternatively, surface safety thermostats with shut-off intervention, thermoresistors PT100 and/or thermocouples “J” or “K”), suitable for heater protection from overheating and possible premature damaging. Based on the customer specific exigences, the power or gas inlets power (NPT or GAS) are also properly dimensioned according to the number of elements installed and rated power installed

These types of electric resistors surface load (W/cm2) is properly decided case by case, according to the use conditions and the type of fluid to be heated; in addition to these factors, the maximum operating temperature and operating environment also are variables directly influencing the sheath material type choice the tube bundle of these heaters will be manufactured with (Carbon steel, Stainless steel AISI304, AISI 321, AISI 316L, Incoloy800).