Engineer Insight

Ask Ian: Increasing Conductive Heater Element Life

Does continuous operation shorten heater element life? It’s a common question, and frankly, the answer is yes. All heating wire will eventually fail over time, but it is possible to improve the life of the heater by following these recommendations. All heater types require a balance of cooling and voltage control to avoid overshoot failures. If a heater’s watt density is too high, the heater will quickly get too hot. It’s this accumulation of heat and the resulting oxidation of the internal components that ultimately lead to the death of a heater. The higher the temperature the higher the oxidation. Over time, the heater will fail. How much time depends on how well the temperature is controlled.
 
In the case of a conductive product, like a cartridge heater, if the heater is inserted into a tightly fitting hole in a large steel block and operated with a good voltage control and a moderately safe temperature of 300º or 400°F then the heater could last for many years.  In that instance, the heater has a low setpoint temperature and the low level of heat that is generated is sucked away quickly by the surrounding mass. Less temperature means less oxidation and longer heater life.
 
A wide range of variations is possible based on the application the heater operates in. Some heaters come back from the field operating for over 30 years while others can fail in weeks if not properly installed and controlled. In some cases, applications requiring higher temperatures may be detrimental to heater life but if high temperatures are required, the element life expectations should be shorter and a back up heater element kept in stock for quick field replacement.

Here are some quick pointers to help develop a conductive heating system for sustained performance:

Cooling – Conductive products use heatsinking to another mass to cool the element wire. It can be liquid, a tightly fitted metal mass, and air.
 
Voltage Control – Closed Loop control measuring process temperatures keep the heater running based on safe operating set points.
 
Ramp Rates – Managing the temperature increases and decreases through time avoids temperature overshoot. In combination with a closed-loop system, it’s an effective solution to increase heater life.
 
Process Temperatures – It's important to understand process temperatures are not actually element temperatures. To get to a process temperature quickly, the element temperature must be very high to heat the surrounding parts, mass, air, or medium. A safe balancing act occurs when using a fast-acting temperature controller in a closed-loop system. Proper setup, thermocouple type, and thermocouple placement are essential.

We are here and happy to help with any technical questions related to our heaters and your application. We look forward to working with you. 

Ian Renwick
Director of Engineering
TUTCO, LLC

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