Heater Failure Peppers Salt Bath Performance - Solved With Watlow Tubular Heaters
Salt bath furnaces treat metals 300-750°F(150-400°C) to achieve improved uniform hardness, less distortion, and reduced cleaning time. Types of applications where these qualities are designed are:
- Parts for computers
- Golf clubs
- Cutting tools
- Lawn mower blades
- Chain saw guide bars
- Gears and valve plates
Molten salt is the heat transfer medium used because:
a) It transfers heat rapidly
b) It virtually eliminates the problem of vapor phase barrier during the initial stage of quenching
c) Its viscosity is uniform over a wide range of temperatures
d) Its viscosity is low at removal temperatures, thus minimizing drag-out losses
e) It remains stable at operating temperatures and is completely soluble in water, thus facilitating subsequent cleaning operations
A competitor's tubular heater had a short life in this heavy industrial environment. The sheath tended to crack when the customer attempted to bend the tubular heaters. The junction between resistance wire and terminal pin was weak and the seals permitted moisture to pass into the heater.
Watlow tubular heaters replaced the competitive make. Watlow tubulars immersed into this highly corrosive fluid bath have a proven record of lasting over a year.
Because this customer has furnaces ranging from 9 by 7 inches (23 by 18 cm) to 20 feet deep by 48 feet (6.1 m by 14.6 m) long, he bends straight tubular heating elements into 200 plus configurations as required by the application. The 160-inch Watlow tubular, with a 0.059-inch (1.5 mm) steel wall, is fully annealed to facilitate field bending.
The 360 degree fusion weld between resistance wire and terminal pin is trouble-free and adds life versus the competitor's spot weld. Epoxy resin offers a moisture-proof seal for these heaters, too.
Salt baths are an efficient heat treating technique. Watlow tubular heaters are needed in this industry because of their durable construction that promotes a longer life.