Power Plant using Immersion Heaters for Tank Heating

Situation: A power plant located in North Dakota uses large holding tanks that contain demineralized water that is used in the process of their turbines. The challenge was to keep this water at an acceptable temperature during the cold winter climate of the Midwest. Water levels also need to be monitored closely as tubular elements had a tendency to be exposed to the air when liquid levels decreased.

This caused burnouts and, expensive downtime. A precise temperature control system was required to maintain the temperature as well as provide safety redundancies to protect the heater in case of overheating. The control center was located far from the location so a solution was required to monitor the activities.

Solution: Wattco provided three 10 inch stainless steel 150# ANSI flanged heaters each were rated 250KW with NEMA 4 waterproof terminal boxes to avoid possibility of corrosion and termination failure.

Two thermocouples were used: one in the bundle of the process heater for heater element protection and the other at the opposite end of the tank to maintain temperature control at the extremity of the tank.

Cold winters can have a detrimental effect in areas of the tank that are not heated – typically the point furthest from the industrial heater. A PLC controller was used and able to control the heat intensity as well as provide a high limit shutoff in case of overheating. A thermocouple was also placed on the sheath of the tubular element to measure heat intensity and relay this information to the controller. Alarms were available to alert technicians of problems should the water level fall below acceptable levels.
 
Benefits
·         An all in one solution to monitor temperature levels in a remote area
·         Thermocouple controls that add safety controls as well as provides users with immediate notification of element failure