All the components of a flowmeter are important but in the flowmeters with indication by means of magnetic coupling the graduated scale plate and the indicator needle are particularly important. We explain this to you.
Do you have an audit tomorrow? Murphy’s Law: It is the perfect time for our flowmeter or level meter to start showing a wrong performance. But yesterday we checked it to make sure it was going to work well! The indicator needle seems to get stuck and / or readings are not correct.
This situation occurs quite frequently, it is not something that only happens to you. Trying to avoid problems, sometimes we generate other because of lack of care or being in a rush.
We wish everything goes smoothly and check the instrument from head to toe. Even we disassemble part of the device to clean and remove the cover with the measuring scale.
Después lo montamos y ¡listo! Todo debe funcionar perfectamente para la auditoría que nos trae de cabeza.
Then we re-assemble it and ready! Everything should work perfectly for the audit that brings us a big headache.
The only problem is that now the needle seems to move slowly or does not indicate correctly the flow rate which should be passing through. And this happens because we have not placed correctly the instrument graduated scale plate when re-assembling.
“It is very important to place the graduated scale plate
in the right slot and not in another one”
When the scale plate is not installed on the housing, we can see several slots where different parts are placed.
The scale plate should be fitted on the first outer slot (lower and upper) by sliding until it stops.
One of the advantages of this type of instruments with modular housing is that we can retrofit limit switches and/or transmitters. Do you know which switchescan you install? Have a look at this article to find it out.
Parallax error in the flowmeters with indicating needle
If we have placed the graduated scale plate in the second outer slot, surely we cannot see the actual value of the readings due to parallax error:
Graduated scale plate placed correctly
Scale plate placed in wrong slot
with reading parallax error
Maybe the scale plate is located in the correct slot but the indicator needle is bent, it is in contact with the scale plate and it seems to be getting stuck.
Sometimes it happens that when placing the graduated scale plate in the slot we put, without realizing, the indicator needle through a slot that exists on it that is used to display some switches.
Sólo deberemos enderezar la aguja doblándola suavemente hasta separarla 2-3 mm de la superficie de la escala.
The indicator needle of our flowmeter does not show 0 flow
If you detect that the indicator needle does not point the zero flow scale in its rest position, we will have to check a few things:
1 . If when the float is lifted up and down the indicator needle moves but does not return to 0, we have to check that the pointer hub is firmly fixed to the shaft.
If it is not so you have to fix it onto the conical tip of the shaft by tapping it lightly and carefully.
2 . If the pointer hub is correctly fixed to the shaft, you should match the indicator needle with the 0 of the scale by using the front adjusting screw of the indicator needle, turning it right or left depending of the movement we wish.
IMPORTANT: Hold the shaft so that it is not bent or damaged.
3 . Check that there is no friction between the indicator needle system and the cables connected to a limit switch and/or transmitter you have installed on your instrument.
You have probably managed to make your flowmeter or level measurement equipment to work properly. That’s great, certainly you will not forget for a next time to take these recommendations into account.
If your instrument still does not show correct readings after checking all the points before mentioned, you will have to contact your sales engineer. For sure he/she can give you some more new tips to try before sending the device to Tecfluid for checking.
Before anything have a look also to our article on the performance of flowmeters with indication by means of magnetic coupling. Perhaps it is a problem you could have avoided.
I hope you were able to solve it and you have passed your audit with flying colors!