Underground pump rooms are often the areas in automation upgrades that “appear to be nearby but are actually the most difficult to communicate with”: equipment rooms are located underground, concrete walls are thick, pipes, motors, and frequency converters are densely installed, the air is humid, and some areas also have metal doors, fire compartments, or corner passages. When technical evaluators consider wireless differential pressure transmitters, their primary concern is not whether the instrument can measure differential pressure, but whether the data can be continuously and reliably transmitted to the control room or platform.

The conclusion is not simply “stable” or “unstable.” Wireless differential pressure transmitters can be used reliably in underground pump rooms, provided that the communication method, installation location, antenna arrangement, power supply conditions, and on-site electromagnetic environment have been specifically evaluated. If selection is based only on communication distance in open above-ground environments, issues such as intermittent disconnections, data delays, low battery power, or fluctuating signal strength may easily occur later.

First clarify: stable differential pressure measurement does not mean a stable wireless link

A differential pressure transmitter is responsible for measuring the pressure difference between two points. In an underground pump room, it may be used for filter blockage monitoring, determining the pressure differential before and after a pump, monitoring pipeline network differential pressure, converting level difference measurements, or controlling ventilation system differential pressure. The accuracy, range, overload capacity, and media compatibility of the sensor itself determine whether the measurement values are reliable, while the wireless transmission section determines whether the data can be delivered in full.

The two aspects should be evaluated separately. For example, a differential pressure transmitter may be installed near a pump unit, with properly designed impulse piping, a matched range, and stable displayed values. However, if the wireless module is enclosed in a metal control cabinet, or several reinforced concrete walls separate the control room from the pump room, the platform may still frequently receive missing data. Conversely, a smooth communication link cannot compensate for measurement errors caused by water accumulation, blockage, or zero drift in impulse lines.

Therefore, procurement or retrofit plans should clearly define two sets of acceptance criteria for wireless differential pressure transmitters: one for instrument metrological performance and the other for communication availability and data integrity. Confusing the two often makes troubleshooting lengthy.

Which factors in underground pump rooms are most likely to affect wireless signals

Obstruction and multipath reflection are the primary issues. Walls, floor slabs, and fire doors in underground pump rooms can significantly attenuate wireless signals, while large pumps, tanks, valves, cable trays, and metal pipes can create reflections. The signal may not disappear completely, but it can fluctuate due to equipment startup and shutdown, door opening and closing, or personnel movement on site. For differential pressure data requiring continuous trend analysis or abnormal-condition alarms, this uncertainty needs to be eliminated in advance.

Electromagnetic interference should not be overlooked either. Areas near frequency converters, motor starter cabinets, contactors, and cable trays are usually locations where interference is concentrated. Wireless communication does not mean being “completely immune to interference,” especially when the transmitter is close to power cables, variable-frequency control cabinets, or high-power equipment; both communication quality and equipment power supply stability may be affected. Installation locations should avoid strong interference sources and areas with extensive metal shielding as much as possible.

Humidity, condensation, and water ingress risks affect the long-term condition of the equipment. What is common in pump rooms is not uniform humidity, but localized condensation, valve leakage, and splashing wash water. Enclosure protection, cable entry sealing, antenna interface treatment, and prevention of water accumulation in impulse piping are all related to long-term stable operation. Wireless equipment reduces the need for long-distance signal cable installation, but this does not mean that installation details can be given less attention.

How to select a communication solution: do not look only at “how far it can transmit”

The theoretical communication distance in selection materials usually comes from relatively ideal environments. Underground pump rooms should focus more on penetration capability, networking capability, retransmission mechanisms, data buffering, and on-site maintainability, rather than comparing distance figures alone.

There is an easily overlooked boundary here: if the differential pressure signal directly participates in pump unit safety interlocks, emergency shutdowns, or millisecond-level real-time control, wireless solutions should be evaluated cautiously. Wireless transmission is more suitable for monitoring, remote meter reading, condition warnings, retrofit supplementary measurement points, and non-critical closed-loop data acquisition. Where critical protection circuits are involved, reliable wired control links should generally remain the primary choice, or a system architecture with clearly defined redundancy should be adopted.

During site surveys, it is recommended to record these six items

Rather than deciding in an office that “it should work,” a targeted site survey is more valuable. Technical personnel can inspect the route section by section from the planned transmitter installation point to the gateway, receiver, or control room, and record the following information:

• The straight-line distance between the installation point and the receiving end, as well as the actual number of walls, floor slabs, and metal doors along the route;
• The relative positions of pump units, variable-frequency cabinets, distribution cabinets, cable trays, and large pipelines in relation to the instrument;
• Whether there are elevated and relatively open locations available for installing external antennas, relay equipment, or gateways;
• Whether stable power is available in the pump room, and whether continued data collection or historical data storage is required after a power outage;
• The medium, temperature, pressure fluctuation range at the differential pressure measurement point, and the pressure tapping conditions on the positive and negative pressure sides;
• The final data access location: local display instrument, PLC, host computer, IoT platform, or remote operation and maintenance system.

Among these factors, antenna installation height is often more important than many people expect. Moving a gateway or receiving antenna from a low corner to above a doorway, to a more open area near a corridor turn, or away from densely packed pipelines may be more effective than simply replacing it with higher-power equipment. If the pump room structure is complex, relay nodes are generally a more reliable choice than “gambling on long-distance penetration” in one attempt.

The selection of the differential pressure transmitter itself must also match pump room operating conditions

Communication stability is only half of project success. Differential pressure transmitters used in pump rooms should also be selected according to the measured object to confirm the range and pressure resistance. The pressure differential before and after a filter is usually small; if the selected range is too large, the effective resolution will be insufficient. For pipeline networks or pressure differentials before and after pump units, static pressure, transient pressure surges, and overpressure conditions must all be verified. For systems where water hammer may occur, the model cannot be determined solely based on the pressure differential under normal operating conditions.

Impulse piping is also a common source of error. Improper pressure tapping locations, excessively long piping, significant temperature differences between the two sides, condensate in gas systems, or air bubbles in liquid systems can all distort differential pressure readings. Before installing a wireless differential pressure transmitter, it should first be confirmed whether the pressure tapping method complies with process logic; otherwise, even continuous and visually perfect data on the platform may only be steadily reflecting an incorrect condition.

For areas that are humid, contain corrosive gases, or require frequent washing, appropriate wetted materials, sealing methods, and protective structures should be selected based on the medium and environment. If the equipment is installed in a location that is difficult for personnel to access, the operability of zero checks, draining, maintenance, and battery replacement should also be considered.

Do not conduct only a “can it communicate” test; conduct an operating-condition test

During project acceptance, it is recommended not to merely check once whether data has come online after equipment installation is completed. A more reliable practice is to test the pump unit under different operating conditions, including startup, variable-frequency speed regulation, full-load operation, and shutdown changeover. Observe whether the wireless data exhibits obvious fluctuations, increased delays, or brief interruptions, and verify the consistency among on-site instruments, transmitter outputs, and platform records.

Performance after network disconnection should also be checked: whether the equipment can buffer data, how data is retransmitted after communication is restored, and how the platform marks offline or abnormal conditions. For remote operation and maintenance, the most troublesome issue is not the occasional loss of a single data point, but when the system misjudges a communication interruption as normal process operation, or cannot distinguish between “the actual differential pressure remains unchanged” and “the device has lost connection.”

Xi'an Shenghongchuang Instrumentation Co., Ltd. and its subsidiary, Shaanxi Qinkong Sensor Technology Co., Ltd., have long provided pressure, level, differential pressure, and other sensing and supporting instrumentation products for industrial automation measurement and control applications. In projects such as underground pump rooms, where site conditions vary greatly, matching based on measurement point operating conditions, installation structure, communication paths, and system interfaces is more appropriate than determining a solution solely by a single parameter.

Evaluation conclusion: wireless is feasible, but “the site” must come before parameters

Underground pump rooms do not inherently exclude wireless differential pressure transmitters. For scenarios with difficult cable routing, tight retrofit schedules, dispersed monitoring points, or a need to connect to digital platforms, wireless solutions offer practical value. However, their stability comes from sound design, not from the word “wireless” in the equipment name.

Before making a final decision, technical evaluators are recommended to complete at least three tasks: confirm differential pressure measurement requirements and safety levels, inspect the actual communication path and conduct on-site testing, and clarify the handling logic for network disconnection, low battery power, and abnormal data. Only when the measurement end, transmission end, and platform end form a closed loop can wireless differential pressure data truly serve as a basis for judging pump room operation, rather than being merely an occasional signal appearing in the system.