Fast and repeatable response

With our fast acting RTD tip design and thermowells, our system is usually faster than typical competitor spring loaded versions. Response time for thermowell mounted temperature probes will normally be in the range 10 seconds for T05 (50% of temperature change) and 40 seconds for T09. The chart below shows the reaction curve for our typical competitor’s spring loaded assembly versus ifm’s temperature instruments assembled into a thermowell.

Response time comparison between a thermowell mounted ifm temperature sensor and a typical spring loaded design

When an air gap exists between the probe tip and thermowell, response time is increased. Total reaction time of a ¼” probe tip contact gap will significantly increase T09 response time of the thermowell assembly. This can add an additional 30 seconds to the thermowell and temperature probe assembly (60+ seconds total). Adding thermal grease will greatly minimize the increased response time. Longer reaction times are typically not an issue with long length thermowells used in storage tanks. It is not recommended to have combinations with air gaps in short assemblies used for pipe applications monitoring flowing fluids.

Thermowell vs. protective tube

Ifm offers both thermowells and protective tubes for temperature sensors, but the products are all listed under the term "thermowell". The main difference is that a thermowell housing is constructed of one piece of metal with no welds, while a protective tube is multiple pieces welded together. As a result, protective tubes have a lower pressure rating than thermowells. As seen in the image to the right, a protective tube consists of:

1. Process connector
2. Metal tube
3. Metal plug

Most ifm thermowells comply with the "ASME" (American Society of Mechanical Engineers) standard, which allows them to be dimensionally interchangeable with standard pipe and tank penetrations. This means that the form factors of ifm's thermowells are generally equivalent to other North American thermowell manufacturers. It is important to note, however, that products are not "ASME" stamped, since entire machines are certified for "ASME".

See examples of thermowells and protective tubes below.