Industrial Tank Level Monitoring

Application Background

Measurement of levels in tanks is important across many industrial applications. There are many tank monitoring applications, for example fuel monitoring, mining process liquids monitoring, and pipeline corrosion inhibitor liquid monitoring. The monitoring is required for two purposes. One purpose is to make sure the liquid does not run out / the tank does not run dry. Another purpose is to ensure the liquid is being drawn from the tank in line with the expected usage, which is another indicator that the process using the liquid is operating correctly, and is a derived measure of the flow from the tank.

Application Detail

For this application, it would be appropriate to use a pressure sensor, and use the pressure from that sensor to determine the level in the tank. The sensor would be most likely strain gauge technology, sometimes called a hydrostatic sensor. These sensors can be either vented or non-vented. Vented sensors have one side of the sensor exposed to the liquid being measured and the other side of the sensor open to the air, either directly exposed, or exposed by using a small vent tube inside the cable with a vent to the atmosphere at the termination end of the cable. Non vented sensors need a barometric pressure sensor at the location of the measurement to provide the current atmospheric pressure, which is then used in a calculation to compensate / normalise the pressure reading based on the current atmospheric pressure at that location and at that time. The casing for such sensors can be either stainless steel or titanium. Titanium is chosen for more corrosive environments. The output of such sensors can be 0 to 5 volts, 4 – 20mA, SDI-12 or Modbus. The diagram shows two methods of connecting the sensor. The first method is to immerse the sensor in the liquid and the cable exits from the top of the tank. The second method involves adding the T piece with an attached pressure sensor to the tank output pipe. Pressure measured within the T piece is directly related to the level in the tank.

Consideration should be also given to the choice of communication channel for the telemetry function. The most economical choice, if available, would be to use a cellular network. All Unidata Neon Remote Loggers support this option. If there is no cell phone coverage then the Satellite Neon Remote Loggers would be the way to go. As tank monitoring is low volume data, services such as Iridium short burst data, Inmarsat ISAT Data pro or Orbcom are probably the best options.
However, the data transmission costs escalate greatly for these services when the data rate is anything more than an occasional transmission of a short packet of data.
The third option is to use a LoRa Neon Remote Logger. In this case, water level sensors are read by the logger according to the scheme. A set of short data packets will be sent, as set by logging interval, to the LoRa WAN gateway over either private or public LoRa network. LoRa WAN gateway transfers data packets to Neon Server using Ethernet, cellular or satellite network. The LoRa WAN system has a typical range of up to 5km, the range reduces in built up areas depending on building density and increases where there is line of sight and when a larger antenna is used.

The application is quite a simple one; the tank level should be measured, perhaps hourly, and stored locally and then sent to the Neon Server daily to display the level on the Neon Web application. The Neon Remote Logger in the field would also have alarms set up based on any unusual condition, for example too fast level changes would indicate a leak and too slow level changes would indicate a blockage. In the event either of these conditions was detected an immediate transmission back to the server will be initiated and an alarm set to alert operators of the problem.

As the power requirements for this type of monitoring are light, the whole system could be housed inside a small pelican case and powered by a set of lithium batteries. The power budget is small as the sensor would be turned on every few hours and only for the short period of time needed to take a measurement. In this configuration a suitable lithium battery pack could power the entire system for up to 5 years.

Typical Configuration

Options for Application Specific Instruments / InputsUnidata Part NumberDescription
Hydrostatic Water Depth Probe6542D-A / B / CPT12 Pressure / Temperature Sensor SDI-12 3.5m, 10m or 20m
Hydrostatic Water Depth Probe - Titanium6542D-T-A / B / CPT12 Pressure / Temperature Sensor SDI-12 3.5m, 10m or 20m
4-20mA Pressure Transmitter6548A-B / CSubmersible Pressure Transmitter 4-20mA 5m or 10m

Options for Neon Telemetry - NRL / NRT / RTU / Field UnitsUnidata Part NumberDescription
Neon Remote Logger 16 Channels3016AOptions Available: 3G/4G Cellular, Ethernet, Globalstar, Inmarsat, Iridium SBD and LoRa
Neon Remote Logger 8 Channels3008AOptions Available: 3G/4G Cellular, Ethernet, Globalstar, Inmarsat, Iridium SBD and LoRa
Neon Remote Logger 4 Channels3004AOptions Available: 3G/4G Cellular
Neon Remote Logger 4 Channels M Series3004A-MOptions Available: 3G/4G Cellular, Ethernet, Microsatellite, Iridium SBD and LoRa
Cellular RTU 3G/4G2013F-AB03 / 2013F-AB04Neon Metering Module 3G/4G with Antenna and Li Battery
Cellular RTU 3G/4G - Industrial2016F-AB03 / 2016F-AB04Neon Remote Terminal 3G/4G with Antenna and Li Battery
Low Earth Orbit Satellite Globalstar2015F-AB0NRT Satellite Globalstar Modem with Antenna and three Li Batteries
Ethernet2017F-0B0-1 or 3NRT Ethernet with single or triple Ethernet Ports with three Li Batteries
Equatorial Orbit Satellite - Inmarsat2018F-AB0-1 or 3NRT Ethernet with single or triple Ethernet Ports with three Li Batteries
LCD Display2500ENRT LCD Display
NRT Field Termination Strip2103F2015F,2016F,2017F, and 2018F NRT FTS
NRT Firmware Option2303A-8M8M Extended Memory Option
NRT Firmware Option2303A-8M-CAM8M Extended Memory & Serial Camera Option
NRT Firmware Option2303A-CAMSerial Camera Option

Options for Neon Application Software - Customer ServerUnidata Part NumberDescription
Neon Application Software2302ANeon Server Software Licence Incl 5 NAL
Neon Application Software2302A-10Additional 10 NRT Access Licences
Neon Application Software2302A-20Additional 20 NRT Access Licences
Neon Application Software2302A-50Additional 50 NRT Access Licences

Options for Neon Application Software - Unidata ServerUnidata Part NumberDescription
Neon Application Software2301ANeon Data Initial Subscription Setup Fee
Neon Hosting Service2301A-01Neon Data Service Fee for 1-50 NRTs
Neon Hosting Service2301A-02Neon Data Service Fee for 51-100 NRTs
Neon Hosting Service2301A-10Neon Data Service Fee Metering

Options for Conventional Dataloggers / Field UnitsUnidata Part NumberDescription
Neon Remote Logger 16 Analog Channels / Touch Screen Display3016A-00016 Ch NRL (Superseded Prologger 7001D)
Neon Remote Logger 8 Analog Channels / Touch Screen Display3008A-0008 Ch NRL (Superseded Stalogger 6004D)
Neon Remote Logger 4 Analog Channels / Touch Screen Display3004A-0004 Ch NRL (Superseded Micrologger 8010C)
Starlog V4 Management Software6308A-AUEStarlog V4 Full Licence Key