A level transmitter's job is a little harder than you may think. Sure, the concept of detecting a liquid level and transmitting a signal to a control system is pretty simple. However, the concept leaves out all the sticky specifics.
The problem is that we often put our level sensors in - and this is saying it nicely - harsh environments.
The term "harsh" is a pretty broad one. An environment can be called "harsh" if it is:
- unusually hot or cold
- especially caustic on standard materials
- exposed to moisture and dust
- prone to heavy vibrations
- likely to cause stickiness and build-up
- hazardous to health and safety
- or otherwise difficult for either humans or sensors
If you're monitoring a liquid level in a harsh environment, you need a sensor that is up to the task. It may be constructed of specialty materials, or have hazardous location certifications, or it may work well with suspended solids or sticky liquid. Choosing the right level transmitter starts with identifying the harsh in your harsh environment.
The Right Level Transmitter
An interesting example of a harsh environment we came across is the paunch disposal tank at a nearby slaughterhouse. If you are not sure what paunch disposal is, it is the process of cleaning out the innards (stomach, intestines, etc) of a slaughtered animal. Fun, right?
The slaughterhouse needed a level transmitter in the paunch disposal holding tank to control their lead-lag grinder pumps. When activated, the pumps send the slurry off to a wastewater treatment process.
For this particular application we recommended two magnetic level probes. The heavy-duty probes were a good fit for the underground tank where mounting is difficult. The float on the magnetic probe is designed for suspended solids and has an excellent track record in similar circumstances. It is also built with a 1-inch thick stem, which is capable of withstanding extreme turbulence from submerged pumps.
Both magnetic level transmitters were installed in the 48 inch holding tank located in the Paunch disposal area of the facility - one as a primary and one as a backup sensor. Activating the pump in a timely manner is very important to prevent excessive odors and to maintain hygiene.
It is important to note, however, that if this tank was situated differently, an ultrasonic sensor would have made good sense as well. Ultrasonic level sensors often perform exceptionally in harsh conditions - depending, of course, on what those harsh conditions are.