Pressure resistance and resistance to flow rate of SAH heaters
For the SAH series, the basic pressure resistance is 0.6 MPa. However, in addition to this, resistance to flow rate should also be considered. Maximum resistance to flow rate is basically set as (Rated power of the model x 0.15 L/min). The resistance to flow rate can be increased up to 5 times this value with special treatment.
When the unit is used in a line, the high pressure will be applied to the entire line leading to the problem of air leaking from the unit through which wire is drawn, the leakage is also reduced to almost zero with special treatment.
Heating element and hot air temperature, and heater life of SAH heater
In SAH series, heating element and heat vapors are in direct contact. The outer diameter is compact but the surface area is extremely large due to the high density heating element. The difference between the temperature of heated gas and heating element is about 572ºF (300ºC) and the heat transmission efficiency is very good. The passing gas can be heated to approximately 1472ºF (800ºC).
When the heater is used for high temperatures, if the voltage applied is limited to around 60% of the rated voltage (1/3 of the rated electric power) and air flow rate is reduced accordingly, air with high temperature (1652ºF (900ºC)) can be generated.
The maximum temperature for the service life of the heating element is set to 2012ºF (1100ºC), above which the service life drops rapidly. At 2102ºF (1150ºC), the service life drops to below several hundred hours ( the lifetime will differ depending on the heating wire thickness and other conditions even at the same temperature).
Service life of several thousand hours can be expected with a heating element temperature of 2012ºF (1100ºC), and service life up to several years can be obtained if the temperature is below 2732ºF (1050°C). Hot air temperature at this heating element temperature is usually as low as 572ºF (300°C). In other words, if the heating element temperature is 2012ºF (1100ºC), the hot air temperature is approximately 1472ºF (800ºC). As described above, if the voltage is reduced to about 60%, the temperature difference approaches to approximately 392ºF (200ºC). When the heating element temperature is 2012ºF (1100ºC), the hot air temperature is approximately 1652ºF (900ºC).
The service life of SAH heaters is mainly determined by the temperature of the heating element. As a manufacturer, it is difficult to guarantee the service life.
Accuracy of Built-in Temperature Sensor
The built-in hot air temperature sensor (optional) is not accurate enough to be used as a reference for hot air temperature. Set the hot air temperature using a standard thermometer and use it for reference in case the built-in sensor temperature is used during that time. The reproducibility of temperature is comparatively good with the same heater and is sufficient to be used as an operating standard. The operating temperature of the reference thermometer must be reset without fail when the heater is replaced.
The accuracy of the built-in temperature sensor is poor and cannot be used as a temperature reference because the air flow condition and temperature distribution inside of the hot air heater is complicated, and it is difficult to measure the average hot air temperature with the sensor inside the heater as the measured temperature changes considerably depending on the installed position etc. There is no improvement even by improving the accuracy of the installed position.
Overheat prevention of heater with the built-in temperature sensor
In addition to the hot air temperature sensor, the optional temperature sensor for heating element can be installed. The use of this sensor is to primarily prevent the burn out of the heating element due to overheating. If for some reason such as malfunction, the air supply stops or reduces significantly, the output temperature of the temperature sensor used for the heating element increases rapidly from the normal state. If this is detected, even when there is a malfunction such as stoppage of air supply, it can protect so the heater does not burn out.
Service Life of the Built-in Temperature Sensor
Normally K thermocouple is used as a temperature sensor. Using a thermocouple of sufficient thickness may not be possible depending on the size of the heater. Wire with diameter of 0.039 in (ø1.0 mm) can be used for a metal case of ø0.5 in (ø13 mm) type and 0.019 in (ø0.5 mm) for metal case of ø0.314 in (ø8 mm) type.
Since the structure is such that the temperature sensor passes through the center of the heating element, the sensor is exposed to almost the same temperature as the heating element. In many cases, there is no problem with the service life of the thermocouple but on using the SAH heater at very high temperatures, the service life of the built-in temperature sensor may be reduce. Specify R type (platinum type) built-in temperature sensor in such cases. The option code added to the model number is /+S(R). In case of 2 sensors, it is /+2S(R).
Compliance with RoHS Directive
Our products are manufactured carefully without using hazardous substances. RoHS compliance has been completed even for SAH.
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