Application Note on Read First
Worry later, or Struggle first and then read the manual later, Radar Level Measurement
with FMP40’s – solving the unseen problem
Have you ever rushed to apply an instrument
and failed to read the manual. If you are like most people you will follow the
pictures in the manual before you read the details. It is also been said, “the
Devil is in the Details.” If you ever built models as a child, you will know
only to well how easy it is to put the pieces together and forget that one.
Like the pilot in the cockpit for the model airplane, after you have glued the
canopy in place. Recently on a service call for a manufacturer in the Michigan
market an otherwise apparently simple installation became much more of an
effort. The effort could have been avoided if only some specific details in the
installation manuals were read / reviewed prior to the installation.
The level transmitter was installed in a wet
well that collects rain water and is pumped to a local facility for treatment
and eventual discharge. The installation was completed in the winter and all
devices were working acceptably. It was not until the spring when the weather
broke, the warmth of spring melted the ice, and the concrete structure went
from dry to wet. As the concrete absorbed the moisture it also absorbed the
sensor’s signal, and where it worked in January through March it no longer
worked reliably in April.
Endress+Hauser offer’s the FMP40 Level
transmitter for several applications, from metal tanks to concrete silo’s. In
this case the sensor was installed in a concrete pit, with a 14” thick poured
floor, the concrete was sleeved with a 4”PVC pipe that was 12” long, creating
an issue with the bottom of the opening to the tank. This was necked down to a
2”diameter hole or so, and the cable went through the hole just fine. When the
concrete was dry the sensor’s signal went through this short section with
little noticeable reduction in operation. It was not until April and the wet
cement, that the signal was knocked down to a level to low to return a good
measurement.
In April the installing contractor contacted
the system integrator about the sensor not working, and after a solid day or 2
of effort the contractor called in the manufacturer for assistance. Initially,
from phone support the issue was not detected. After several field efforts to
improve signal strength with the assumption of a good installation, the
installation was again reviewed. It was then learned that the nozzle opening
was not 3.5” all the way down as expected, and that the sensor cable was
mounted 2” from a concrete wall.
Reading in the manual, the installation notes
talk first about metal tanks, 4” minimum distance from a wall, then other
applications, and finally liquid applications and concrete walls where
recommended distances of 18” from the wall are preferred. The sensor was
temporarily installed in a location in the middle of the wet well to verify the
installation location was bad, and the signal increased 10 fold. Now the sensor
was acting as expected. After this a new hole was cored in the concrete floor
away from the all the walls and the sensor signal was 8-9 times stronger than
originally seen in April.
Reading the manual although time consuming on
this particular item could have saved the customer easily over 40 man hours of
combined labor when travel time of all parties is reviewed (the General
Contractor, the System Integrator, and the Company Representative.) For this
application, the cost were not avoided, and they are unfortunately more
significant than the 10 minutes of reading in the manual or review of the
installation position prior to final concrete pour.
If
you have an application question about an instrument installation, please
contact Forberg Scientific’s Service Group and our staff will help you to
resolve your issue, or connect you with someone who visit your facility and
assist you.
If you have any questions our Services or Pricing
please call Forberg Scientific Service Group at 248-288-5990. You can also
contact Endress+Hauser at 800-642-8737.
