At the August Technology Evening, Busisiwe Zikalala from WIKA gave a presentation titled: Sensor protection methods.
Juaandre Heyneke (right) thanks Busisiwe Zikalala for the presentation.
Process sensors come in many forms. In addition to the big four: temperature, pressure, level and flow, process sensors are used in many applications and are designed to take accurate measurements of the process. Busisiwe’s presentation covered the following issues:
Selecting a protective method: The amount of harmful exposure a sensor receives from the environment and harmful constituents in the measuring process depends on what is being sensed and the environment itself. Different packaging is required to cope with and survive the specific application. Two major considerations for protection are at the sensing element/transducer level or at the sensing module level.
Limiting factors of protective methods: The characteristics of a sensor developed for a given application are strongly determined by the requirements of the application and by existing sensor science and technology.
Thermowells: These protect sensors from damaging effects of the measured substance and allow removal of the sensor without compromising the process or environment. The well dimensions should provide sufficient strength to withstand stresses imposed by vibration, pressure and flow. However, sufficient immersion length is necessary for accurate temperature measurement and a large diameter increases response time. It is thus a question of striking the best balance.
Wake frequency: The biggest cause of thermowell failure is vibration due to flow of gas or liquid perpendicular to the thermowell (‘von Karmann effect’). The natural resonant frequency of the thermowell (function of mass, diameter and length) should be kept well below the wake frequency of the fluid/gas. If the two frequencies coincide, the resultant vibration can cause mechanical failure.
ScrutonWell design: This design reduces the amplitude of oscillation by more than 90%, which allows easy and fast installation of the thermowell without expensive and time-consuming rework on site. Thus no Wake frequency calculation required.
General sensor issues: Incorrect readings due to improper mounting; sensor drift due to build up; complete sensor failure; slow response due to dead time or blockage; and mechanical damage.
MESA Africa Summit has been expanded and rebranded SAIMC Supplier Advisory Council
SAIMC
We are writing to share some exciting developments regarding the evolution of the MESA Africa Summit, which has been a cornerstone event in industrial automation and manufacturing excellence.
Read more...How to claim CPD points SAIMC Supplier Advisory Council
SAIMC
SAIMC makes it possible for you to claim CPD points for attending courses and technical meetings, or completing an online quiz on a SA Instrumentation & Control magazine.
Read more...SAIMC: From the office of the CEO:Slaughtering AI holy cows SAIMC
SAIMC
A couple of sessions at various dealers, a wrong delivery, a failed holiday plan, a two-week unplanned vacation and 32 kg of steel on the back seat awaited us as we left South Africa on a dream holiday. But let me start at the beginning.
Read more...SAIMC: Secunda branch SAIMC
SAIMC
At the most recent SAIMC Secunda technical evening, Jenine Jansen van Vuuren, sales account manager from Comtest Technologies, gave a presentation on the calibration of process instruments.
Read more...SAIMC: Durban branch SAIMC
SAIMC
The Durban branch of the SAIMC held its October technology meeting, not on the first Wednesday of the month as usual, but on the second Wednesday to accommodate the very interesting presenter, Nico Erasmus from Abacus Automation.
Read more...SAIMC: Johannesburg branch SAIMC
SAIMC
The October Technology Evening was hosted by Pepperl+Fuchs. Patience Moila, the enterprise mobility expert for sub-Saharan Africa, presented on ‘Lone Worker Protection for the Mobile worker 4.0’.
Read more...SAIMC: It’s not black and white SAIMC
Editor's Choice SAIMC
Grey imports are a problem worldwide, not least in the automation industry in South Africa. The Supplier Advisory Council (SAC) operates under the umbrella of SAIMC, and is tackling this problem head-on.
Read more...How to claim CPD points SAIMC Supplier Advisory Council
SAIMC
SAIMC makes it possible for you to claim CPD points for attending courses and technical meetings, or completing an online quiz on a SA Instrumentation & Control magazine.
Read more...SAIMC: From the office of the CEO: The real damage of fake news SAIMC
SAIMC
People depend on accurate information and their own reasoning and belief systems to draw conclusions or make decisions. However, when they are inundated with fake news, the reliability of the information they receive is compromised.
printer friendly version