A saltwater disposal well operator needed a reliable way to monitor the very low gas blanketing pressure on a remote storage tank to detect valve failures. The key challenge was the remote, off-grid location, which required a cellular-based system with automated alarms for vacuum conditions. A comprehensive solution was provided using a specialised low-range pressure transmitter, a battery-powered wireless 4-20mA adapter, and an IoT cellular gateway to deliver data and alerts to any internet-connected device.
- Application: Gas blanketing pressure monitoring on a saltwater storage tank.
- Challenge: Detecting negative pressure (vacuum) from a valve malfunction at a remote, off-grid location.
- Requirement: A fully wireless, cellular-based monitoring system with automated SMS/email alerts.
- Solution: A low-range pressure sensor, a wireless 4-20mA transmitter, and a cellular IoT gateway.
A saltwater disposal well operator required a robust method for monitoring the gas blanketing pressure on remote storage tanks. The primary objective was to receive immediate alerts if the pressure deviated from its normal positive range and entered a negative, or vacuum state, which would indicate a malfunction in the gas blanketing valve system. The typical operating pressure was maintained between 4 to 6 inches of water column. The critical fault condition that needed to be detected was a drop into the negative range, specifically down to -2 to -6 inches of water column. A significant challenge was the remote location of the tanks, which lacked local network infrastructure and power for instrumentation, making a conventional wired solution impractical. The customer had been searching for a wireless system with cellular communication capabilities to transmit data and alerts from these isolated sites.
The proposed solution is a fully integrated, multi-component system designed for remote, low-power operation. At the point of measurement, a DMP343 series low-range pressure transmitter is used. This device is specifically engineered for measuring very low gauge pressures and vacuum conditions, making it ideal for this application. Configured for a measurement range of -6 to +6 inches of water column, it can accurately monitor both the normal positive pressure and the critical negative pressure fault condition. The DMP343 provides a standard 4-20mA, 2-wire current loop output signal that is proportional to the measured pressure. Its high-quality construction ensures excellent long-term stability, which is vital for reliable monitoring in unmanned locations.
To overcome the lack of cabling and power, the 4-20mA signal from the pressure transmitter is fed into an IWTxT series wireless current transmitter. A key advantage of the IWTxT is its ability to provide the necessary excitation voltage to power the connected DMP343 pressure transmitter directly from its own internal battery pack, eliminating the need for any external power source at the tank. The IWTxT reads the 4-20mA signal, digitises it, and transmits the pressure value wirelessly using the license-free 2.4 GHz frequency band. The transmission update rate is user-configurable, allowing for a balance between data immediacy and extending the long operational life of the batteries.
The final component is the IoT-GATEWAY, which serves as the central receiver and communications hub. It receives the wireless pressure data from the IWTxT transmitter, which can be located up to 500 metres away. The gateway’s integral 2G/4G cellular modem directly addresses the customer’s core requirement for remote communication. Using the MQTT protocol, the IoT-GATEWAY uploads the sensor data to a secure, cloud-based IoT Platform. This platform provides a user-friendly interface accessible from any internet-connected device, such as a PC or smartphone, for viewing live and historical data. Most importantly for this application, the platform allows the operator to configure alarm thresholds. If the tank pressure drops below a pre-set limit and enters the negative range, the system automatically generates and sends an alert via SMS and/or email, providing immediate notification of the gas blanketing valve malfunction.
DMP 343 Bi-Directional Negative & Positive Gauge Low Range Pressure Transmitter
- Pressure Range: -6 to +6 inWC
- Range Type: Bi-Directional Gauge (-P to +P)
- Output Signal: 4-20mA (2 wire)
- Electrical Connection: M12 x 1 connector (4 pin)
- Process Connection: 1/4 NPT male
- Media Compatibility: Air and non-corrosive gases
IWTxT Loop Powered 4-20mA Input to Wireless Transmitter
- Part No: IWTxT-00
- Input: 4-20mA
- Power Supply: AA Cell Lithium Ion 3.6V Battery
- RF Output: 2.4GHz 3dBm Tx Power
- Antenna Type: External SMA Connector
- Enclosure: ABS IP67 with built in battery
IoT Gateway Wireless Transmitter Receiver with Cellular Modem
- Part No: IoT-GateWay-00
- Wireless Inputs: Up to 128 IWT Wireless transmitters
- Analogue Inputs: 4 x 4-20mA or 0-10Vdc
- Digital Inputs: 8 x Volt-free Digital Inputs
- Outputs: 4 x Relay contact outputs
- Communications Inputs: Acts as RS485 Modbus RTU master
- Display: 6 line LCD backlit display
- Cellular Connection: 2G/4G Transmit Bands MQTT protocol
- Power Supply: 12-36Vdc