Accurately monitoring water levels in tanks and reservoirs is critical for industrial facilities. Water level probes provide real-time data on liquid height to inform system operations and prevent overflows or dry runs. But with so many probe technologies available, how do you choose the right one? Consider these key factors when selecting a water level probe for your specific application.
Start by Understanding Your Environment
The first step is determining what kind of substance you need to measure and what type of vessel. Is it water, wastewater, chemicals, oil, or something more viscous? Will the probe be mounted in an open basin, enclosed tank, standpipe, or outdoor pond? Narrow down the probe choices based on which is suitable for your liquid and application.
Assess Required Accuracy and Range
Consider what level of accuracy or resolution you need. For example, do you need to pinpoint liquid height within 1/10th of an inch or is detecting every few inches adequate? Also, what is the overall measurement range? Probes have minimum, maximum, and dead band specs based on their design. Match this range to your tank dimensions and liquid fluctuation.
Compare Measurement Technologies
There are a variety of water level probe technologies to select from:
- Float & Tape Gauges – Simple and inexpensive but can snag in turbulent tanks.
- Capacitance Probes – Accurate, with no moving parts, and good for clean water.
- Ultrasonic – Non-contacting, good for tough environments but at a higher price.
- Hydrostatic Pressure – Ideal for deep tanks, unaffected by density changes.
- Radar – Contacting probe good for a wide range of liquids.
Assess your needs to narrow down the ideal technology.
Consider Your Outputs and Connectivity
Determine what kind of output signal you need – 4-20mA analog, HART digital communication, relays, or Modbus. This depends on how you want to transmit and utilize the level reading. Also, consider connectivity – does the probe need to integrate into a plant control, SCADA or monitoring system? Select technology that aligns with your infrastructure.
Evaluate the Operating Environment
Look closely at the temperature, pressure, flow rate and other conditions the probe will endure. For example, will it handle freezing or boiling liquids? What about buildup from grease, algae and other contaminants? Can it withstand turbulence or other mechanical factors? Choose a rugged probe rated for your environment.
Ensure Chemical Resistance
Confirm the probe’s wet parts, such as seals, cable jacketing, and mounting components, are chemically compatible with the media. Otherwise, corrosion can occur. Look for probes constructed with stainless steel, PVC, Teflon, and other inert materials that are resistant to your substance.
Simpler is Often Better
When possible, lean towards less complex technologies without too many bells and whistles. Simple ultrasonic transmitters or hydrostatic probes are often the most reliable options in harsh plant environments. Avoid overkill if basic point level detection is all that’s required. Consider ease of installation and maintenance too.
Get Proper Electrical Ratings
Verify the probe operates on power supply voltages available at your facility and meets code requirements. Intrinsically safe rating is a must for flammable/combustible liquids. Also, check if explosion-proof housing is needed for hazardous areas. Don’t take electrical compatibility for granted.
Review Accessories
Look at what mounting fittings, conduit adapters, junction boxes, and other accessories come standard with the probe versus at added cost. Factor required accessories into the total investment. Also, consider backup components, like redundant transducers or cables.
Confirm Calibration Services
Regular calibration ensures ongoing accuracy but isn’t always easy with fixed probes. Look for products with calibration test points accessible from outside the vessel. Or choose a supplier that offers cost-effective field calibration services so you don’t have to remove probes.
Consider a Managed Solution
For worry-free level monitoring, a managed tank level gauge solution provides professional installation along with remote system access for management by expert technicians 24/7. This convenient outsourced model is ideal for many industrial users.
While these guidelines will get you started, every application has unique needs. Work closely with an experienced instrumentation supplier to get expert guidance on matching the right level probe technology and features to your specific tanks or vessels. With close attention to detail on the front end, your facility can benefit from precise, trouble-free water level monitoring.
