Watlow Heating System Aids Environmental Clean Up Of Hazardous Waste Site

Problem:asme vessel for soil remediation

Watlow's client was responsible for site remediation at a hazardous waste site, which included cleaning a contaminated aquifer. An extremely large amount of water, 100 gallons per minute, needed to be heated from 10 to 95°C (50 to 200 °F). The project had a limited budget, while at the same time, was to provide enough power to achieve the expected results.


In order to increase the temperature of 100 gallons (380 liters) of water per minute by 80°C (150°F), Watlow created one of its most powerful heaters to date?a 16-inch (40 cm) diameter, 20-foot (6.1 m) long circulation heater which produces 2.15 megawatts of heat.

A heater of this size would usually be separated into two stacked circulation heaters, piped-in series. Because space or size limitations did not exist, Watlow designed the heater as one long vessel, which helped keep project costs down.

Two separate immersion heaters, each containing 93 elements, were designed for placement at each end of the ASME code stamped carbon steel vessel. Incoloy® was specified for the element sheath to provide high temperature corrosion resistance. The innovative design enabled Watlow to provide the power needed for the job.

To monitor water temperature, a process thermocouple was installed in the outlet nozzle. Four Watlow mineral insulated Type J thermocouples were specified to monitor heater temperature.

To control the process, Watlow designed a control panel consisting of one Watlow SERIES 92 ON/OFF control, two Watlow SERIES 340 high-limit controllers and time delay circuitry. The SERIES 340 high-limit controllers, working with Watlow's MI thermocouples, were installed to protect the heaters from over heating. Built-in time delays in each circuit were specified to ensure that the whole system would not turn on at once to prevent excessive "in-rush." Watlow incorporated two lifting lugs with chain shackles for easy transportation, installation and removal of the heater.

Incoloy® is a registered trademark of Special Metals Corporation.