Why Pressure Sensors Cannot Be Selected by Range Alone Under High-Temperature, Corrosive, and Pulsating Conditions

Under normal operating conditions, pressure sensors can usually be matched based on range, output signal, and accuracy. However, in systems involving high-temperature media, corrosive fluids, rapidly fluctuating pressure, or frequent start-stop cycles, sensor failure is often caused not by insufficient range, but by temperature drift, diaphragm corrosion, seal aging, overpressure shock, or fatigue damage.

For example, steam pipe networks, reactors, hydraulic stamping equipment, chemical transfer pipelines, and high-pressure cleaning equipment may simultaneously involve temperatures exceeding 150°C, corrosive media, and instantaneous pressure spikes 1.5 to 3 times higher than normal operating pressure. If selection is based only on normal pressure, the instrument may operate in the short term, but long-term stability cannot be guaranteed.

Therefore, selection under severe operating conditions should shift from merely “measuring accurately” to “measuring accurately and reliably over the long term.” In addition to the pressure range, parameters such as medium temperature, material compatibility, allowable overload, pressure resistance, response speed, installation method, sealing structure, and electrical protection rating should also be systematically verified.

For equipment manufacturers, system integrators, and on-site maintenance personnel, defining operating condition limits before purchase is usually more economical than frequently replacing sensors later, and it also helps reduce the risks of downtime, leakage, and control failure.

I. First Confirm the Pressure Limits: Range, Overload, and Burst Pressure

Operating Pressure Is Not the Only Pressure Value

During selection, normal operating pressure, maximum continuous pressure, instantaneous peak pressure during startup or valve switching, and possible system vacuum pressure should be recorded separately. For hydraulic systems with pulsation, the stable value displayed by a pressure gauge cannot fully reflect the actual impact load.

Under normal circumstances, the sensor full scale should cover the maximum continuous pressure with an appropriate margin. If operating pressure remains near the upper limit of the range for a long period, the risks of zero drift and fatigue increase significantly. If the selected range is too large, resolution and control accuracy in the low-pressure range may be affected.

For frequent pulsating conditions, particular attention should be paid to allowable overload pressure and burst pressure. Allowable overload refers to the sensor's ability to maintain its specified performance after withstanding over-range pressure for a specified period; burst pressure is the limit at which the structure does not rupture. These two values must not be confused.

For example, if normal system pressure is 10MPa and instantaneous spikes may reach 18MPa, selecting only a 10MPa range is clearly inappropriate. A higher range, damping structure, or dedicated impact-resistant pressure transmitter should be configured based on spike duration, occurrence frequency, and control requirements.

II. Key Considerations for High-Temperature Conditions: Medium Temperature, Temperature Drift, and Isolation Methods

Distinguish Between Medium Temperature and Ambient Temperature

The operating temperature in pressure sensor specifications usually needs to distinguish between medium temperature, ambient temperature, and the allowable temperature of electronic components. When a sensor is installed on a high-temperature pipeline, heat may be transferred through the process connection to the sensing element and circuit board even if the ambient air temperature is only 40°C.

An increase in temperature causes changes in zero output and full-scale output. Attention should be paid to the zero temperature coefficient, sensitivity temperature coefficient, and overall temperature error, rather than considering only room-temperature accuracy. For a product with an accuracy class of 0.5%FS, its actual error under substantial temperature variation must also include the effect of temperature drift.

When the medium temperature exceeds the limit for direct sensor contact, heat sinks, capillaries, condensate loops, diaphragm seals, or remote transmission structures can be used to isolate the high-temperature medium from the sensing core. In applications involving steam, heat transfer oil, and high-temperature melts, the isolation solution often determines instrument service life.

It should be noted that adding impulse-line structures can result in response delay and require additional installation space and maintenance. For control loops, not only the cooling effect but also whether the response time meets system regulation requirements should be confirmed. For example, fast pressure protection applications are generally not suitable for excessively long impulse paths.

High-Temperature Selection Parameter Checklist

III. Key Considerations for Corrosive Media: Wetted Materials and Seal Compatibility

Do Not Rely Solely on “304” or “316L” Markings

The parts of a sensor that come into direct contact with the medium usually include the diaphragm, process connection, welds, sealing rings, and fill fluid. Selection must be based on the complete wetted material specification, rather than only on the housing material or a single “stainless steel” description.

316L stainless steel offers good general corrosion resistance and is suitable for many industrial water media, mildly corrosive liquids, and general chemical media. However, for high concentrations of chloride ions, strong acids, strong alkalis, fluorine-containing media, or special solvents, pitting corrosion, crevice corrosion, or stress corrosion may still occur.

When the medium is highly corrosive, materials such as Hastelloy, tantalum, titanium, ceramic diaphragms, or PTFE can be evaluated based on medium composition, concentration, temperature, and pressure. The corrosiveness of the same chemical medium can vary greatly at different temperatures; therefore, “suitable at room temperature” cannot be directly considered equivalent to suitability at high temperature.

Sealing materials must not be overlooked. Seals made of NBR, FKM, EPDM, PTFE, and other materials differ in their resistance to oil, acids and alkalis, steam, and temperature. Expansion, hardening, or dissolution of even one sealing ring can cause leakage, contamination of the measuring chamber, or even total sensor failure.

IV. Key Considerations for Pulsation and Vibration Conditions: Dynamic Response and Fatigue Life

Identify the Sources of Pressure Spikes

Pulsating pressure is common in plunger pumps, hydraulic pumps, compressors, stamping equipment, fast switching valves, and high-pressure cleaning equipment. Water hammer, cavitation, and sudden valve shutdown can also generate pressure spikes with extremely short durations but very high amplitudes, which ordinary instruments may not fully display.

Frequent pressure cycles subject diaphragms, welded sections, and internal sensing elements to alternating stress. Even if each pressure event does not exceed the rated range, zero drift, output fluctuations, and mechanical fatigue may occur after hundreds of thousands or even millions of cycles over the long term.

The sensor's response time, sampling frequency, impact-resistant design, and pressure cycle life should be considered. Control systems that need to capture rapid fluctuations can use products with faster response; applications focused primarily on equipment protection should balance pulsation resistance with reliable overpressure protection.

Dampers, buffer tubes, restrictor orifices, or pulsation absorbers can be configured at the installation end according to operating conditions, but excessive throttling that causes signal delay should be avoided. For equipment subject to strong vibration, vibration resistance rating, connector locking method, and cable fastening method should also be verified to prevent intermittent faults caused by loose connections.

V. Include Installation, Electrical, and Maintenance Conditions in the Selection Process

Sensor Performance Requires Correct Installation

For process connections, confirm the thread standard, connection size, sealing method, and installation orientation. Connections such as G1/4, NPT1/4, and M20×1.5 cannot be identified by appearance alone; mismatched threads or unsuitable sealing surfaces can easily cause leakage and mechanical stress concentration.

For the electrical section, confirm the power supply range and output type based on the on-site control system, such as 4mA～20mA, 0V～10V, RS485, or other digital communication methods. For long-distance wiring, installation near variable-frequency drives, and environments with strong electromagnetic interference, shielding and grounding, surge protection, and anti-interference capability should be emphasized.

The protection rating must correspond to actual site conditions. IP65 is suitable for general dustproof and water-spray environments. Where washdown, condensation, outdoor rain exposure, or high humidity is present, the waterproof structure, wiring method, and sealing reliability of the cable outlet should be further verified. Where flammable or explosive media are involved, the appropriate explosion-proof product should also be selected according to area requirements.

For maintenance, it is recommended to reserve isolation valves, drain ports, or calibration connections at critical measuring points to facilitate periodic verification and troubleshooting. For conditions involving high temperature, corrosion, and pulsation simultaneously, operating records can be established to track zero changes, abnormal peaks, and replacement intervals, providing a basis for subsequent selection optimization.

VI. Pressure Sensor Selection Checklist for Severe Operating Conditions

When submitting selection requirements, it is recommended to provide the medium name and concentration, normal and maximum pressure, peak pressure, medium temperature, ambient temperature, pressure fluctuation frequency, process connection, installation location, power supply method, output signal, and protection requirements at one time. The more complete the information, the closer the selection result will be to actual application requirements.

For complex media, also specify whether particles, crystals, bubbles, viscous components, or substances prone to clogging are present. These factors may affect diaphragm type, impulse pressure method, and cleaning and maintenance solutions. For pulsating systems, it is best to also provide the pump type, valve operating characteristics, and whether water hammer occurs.

Xi'an Shenghongchuang Instrumentation Co., Ltd. can provide parameter matching, structural recommendations, and customized services for pressure transmitters and supporting measurement and control products based on temperature, pressure, media, and installation conditions at industrial sites. For complex operating conditions involving high temperature, corrosion, strong interference, and high-frequency pulsation, technical confirmation is recommended before ordering.

Please organize on-site operating condition parameters and photos of existing connections, and contact technical personnel for a selection assessment. After confirming wetted materials, temperature resistance methods, range margin, and anti-pulsation configuration, determine the specific model and installation solution.