Best Practices in Air Heater Installation

8/30/2019

When installed and operated properly, an air heater should have a long service life. However there are many common pitfalls that can cause problems and shorten the expected lifespan. This article discusses our recommended best practices for installing air heaters to avoid the most common errors that shorten tool life.

Hose or Piping

Air is typically supplied to the heater from a blower connected by either flexible hose or hard piping. When making this connection the pressure drop from the blower to the heater must be considered. As the pressure drop increases, the output flow from the blower will be reduced. Read more about pressure drop in blower-based systems. The following are some best practices to keep in mind:

Use the shortest possible length of hose or pipe to avoid unnecessary pressure drop along the length. Pressure drop increases with hose length.
If lengths greater than 3 meters cannot be avoided, STANMECH recommends using smooth wall hard pipe between the blower and heater; this minimizes pressure drop caused by the surface roughness of the hose wall.
When using flexible hose, avoid any sharp bends or kinks. Every corner increases pressure drop. Similarly, when hard piping, use as few as bends as possible.
- Position the blower so that the outlet is oriented in the direction of the heater.
- When possible, use 45° turns instead of 90° turns.
When using more than one heater with a single blower, be sure that the connections to all of the heaters are symmetrical.
- Air will always take the path of least resistance and will travel preferentially through the path with the lowest pressure drop. At the very least, this might cause differences in temperature or output flow between the two heaters. At worst, this could cause a heater to be damaged due to a lack of adequate air flow.

Proximity to Work

After exiting the air heater the air temperature immediately begins dropping with distance travelled. To be sure the heater is working efficiently it should be placed as close as possible to the target without restricting the outlet. Restricting the outlet can lead to reduced flow and potentially damage the heater.

Thermocouple Placement

Thermocouples are not used in all applications but when applicable there are some rules of thumb regarding placement:

The tip of the thermocouple should be located at the point where the temperature is most critical.
As distance between the thermocouple and the heater increases there will be a greater time delay in the temperature control.
Ensure that it is not possible for the thermocouple to slip out of the path of the heat.
- The heater controls will receive feedback that the temperature output is significantly lower than the actual output. This will result in full power output and could lead to damage to the heater and or the target of the heat.
When the thermocouple is located far from the heater the heaters maximum temperature cannot be used as a set point on the temperature controller. In this scenario, the air temperature at the heater would have to be above its maximum rated limit to register at the thermocouple.
Read more about Thermocouples in Hot Air Systems