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FIREBAR® Tubular Heaters Work Faster, Last Longer In Welding Pre-heat

Problem:

Preheat steel hull sections to obtain proper welds. Traditional round tubular elements have difficulty achieving intimate contact for good thermal transfer, resulting in premature failure.

Solution:

The versatile FIREBAR® has proven far superior to other heaters in many applications including pre-weld heating. The ship building industry, as well as other industries that weld heavy metal plates together must normally heat the plates to a temperature of between 350 and 150 and 230°C (450°F) before welding. In some instances, heat is also applied immediately after welding to prevent the welds from cooling too rapidly. The pre- and post-heating improves the weld quality and prevents brittle welds.

In the ship building and ship repair industry the heater normally used has been a conventional round tubular that has been flattened on the contact side to increase contact area. The heaters are laid on the metal plate or studs and then are welded to the plate and the heater is then clamped to the plate. Typically these round heaters have a very short life. Many times they fail in less than a month due to a high temperature. The round heater cannot transfer the heat to the plate being heated at a rate rapid enough to keep the sheath temperature of the heater at an acceptable level. At times this problem can be compounded if the plate being heated is curved (like a ship's hull), which prevents the heater from being in total contact with the plate. Obviously, the portion of the heater that operates in open air becomes extremely hot.

Our customers report that the short life problem has been eliminated by using the FIREBAR, and the FIREBAR provides several other advantages in addition to increased heater life. the round tubulars were replaced by FIREBAR heaters using the same basic overall physical dimensions. Since the FIREBAR has 70 percent more surface are per linear inch, the watt density was decreased accordingly while still yielding the same kW output.

This lower watt density, increased contact surface area, and high quality heater, provided the following advantages:

  • Heater life increased over (4) times (to date none of the FIREBAR heaters have failed). The actual increased life is expected to be much greater than this. The watt density of the FIREBAR allows it to operate in air without causing over-temperature. Tests show that in applications such as this the sheath temperature of the FIREBAR is approximately 60 percent of the round tubular.
  • Faster heat-up of the work. The flat surface puts the heat into the work, not in the air. Our customers have estimated heat-up time has been reduced by 25 percent. Lab tests confirmed a reduction of at least 15 percent in the time required for heat-up in similar applications when compared to round or strip heaters. 
  • A more even heat pattern is obtained. 
  • Less electricity is used since more of the heat is transferred to the plate directly rather than being lost in the air. Lab tests and customer testing confirms the FIREBAR is approximately 15 percent more efficient than round flattened tubulars in similar applications. (According to our customers, in this particular application a 30 percent efficiency increase was obtained). Due to the increased surface area, in contact with the work, most of the heat is transferred by conduction with the FIREBAR, whereas most is transferred by radiation by a round tubular.

Value Added:

Ability to provide application expertise with a custom FIREBAR solution.