You can extend service life of ISO-KF seals in high temperature applications by switching from generic fluoroelastomers (FKM) such as Viton, to perfluoroelastomers (FFKM), and by ensuring the seal is properly sized.
ISO-KF (or ISO-QF or ISO-NW) type flange seals provide an economical, convenient and simplified means of constructing vacuum systems. However, despite the efficiency offered by these flanges, you may face premature seal failure and unscheduled equipment downtime when standard AS-568A o-rings are specified for locations which will be exposed to >/= 150°C and/or harsh process effluent, particularly in heated forelines and exhaust lines.
Serious errors in calibration and display can result if the wrong sensor type is selected on the controller versus what is actually wired to it. Only a physical check of sensor wire and sensor prompts can detect this condition. A systems validation test checking at several temperature points with an external calibrator or measurement device is highly recommended. See chart below.
This is especially important if using a hi-limit sensor, as the limit sensor may be set incorrectly and will not shut down the system safely in the case of an overtemp condition.
Below are examples of improper readings shown when the controller is set up for default Type J sensor:
There are many factors to consider when choosing a power control device. The role of the output device is to receive a signal from the temperature controller and switch electric current ON and OFF to the heater. When possible, it is convenient to have the output device incorporated into the temperature controller.
Let’s take a moment to explore the different types of switching devices and their advantages and disadvantages:
Electromechanical Relays – an Electromechanical Relay is a mechanical device with moving parts. When power is called for, the control output supplies current to the relay’s wire coil, creating a magnetic field, thus pulling the upper metal contact of the relay down closing the circuit and allowing the load current to flow through the contacts to the heater. Conversely, when the control output cuts off the current signal, the magnetic field is lost and the relay contact opens cutting off current to the heater. The above scenario is for a
