Pressure Monitoring Selection in Chemical Plants: Techniques for Balancing Corrosion Resistance and Precision

Pressure monitoring in chemical plants is a core link to ensure production safety, control process quality, and prevent environmental risks. The erosion of corrosive media (strong acids, alkalis, organic solvents), extreme high-temperature and high-pressure working conditions, and strict explosion-proof and leak-proof requirements put pressure sensor selection in a dilemma: insufficient corrosion resistance shortens service life, while excessive pursuit of precision leads to soaring costs. According to the 2025 Chemical Industry Equipment Maintenance Report, 58% of pressure monitoring failures stem from an imbalance between corrosion resistance and precision selection : either sensor failure due to inadequate material corrosion resistance (average service life less than 6 months), or more than 30% cost waste from blind pursuit of high precision. A single sensor failure-induced process interruption costs an average of over $28,000. 

Combining typical chemical industry scenarios (e.g., acid-base reaction kettles, halogenation processes, solvent storage tanks), this article breaks down selection logic from four dimensions—working condition analysis, corrosion-resistant design, precision matching, and balancing techniques—to help chemical industry professionals achieve the selection goal of "corrosion resistance compliance, sufficient precision, and optimal cost."

I. Core Working Condition Pain Points of Pressure Monitoring in Chemical Plants

The medium characteristics and process conditions of chemical production impose dual stringent requirements on pressure sensors, which is also the premise for "balancing corrosion resistance and precision": 

1. "Graded Erosion" Challenge of Corrosive Media

Chemical media are classified into three levels based on corrosiveness, directly determining sensor material selection: 

• Weakly corrosive media: Such as acid-base solutions with pH 4~9, ethanol, acetone, etc., which cause slight erosion to ordinary stainless steel; 

• Moderately corrosive media: Such as sulfuric acid (concentration 50%~90%), sodium hydroxide (concentration above 30%), chlorine gas, requiring special corrosion-resistant materials; 

• Highly corrosive media: Such as hydrofluoric acid, fluorine gas, aqua regia, hydrogen halide gas, which cause rapid corrosion and failure of ordinary metal materials, requiring special alloys or non-metallic linings. 

2. "Dual Test" of Extreme Working Conditions

• Superposition of temperature and pressure: Process temperatures of reaction kettles can reach 150~300℃, with pressure ranges of 0.5~10MPa. High temperatures accelerate the erosion rate of corrosive media and affect sensor precision (precision drift may increase by ±0.1% F.S. for every 10℃ rise); 

• Multiphase medium interference: Slurries containing solid particles and gas-liquid mixed media (e.g., fermentation tanks) not only intensify corrosion but also wear sensor probes, leading to reduced precision; 

• Explosion-proof and safety requirements: Most chemical workshops are Zone 1/2 explosion-proof areas. Sensors must pass ATEX/IECEx explosion-proof certification and meet leak-proof design requirements (e.g., double-seal structure). 

3. "Scenario Differences" in Precision Requirements

Different processes have vastly different requirements for pressure monitoring precision, and blind pursuit of high precision is meaningless: 

• Precision reaction processes (e.g., pharmaceutical intermediate synthesis, catalyst reactions): Require ±0.1%~±0.2% F.S. precision to ensure stable reaction pressure and avoid by-product formation; 

• Indirect storage tank level monitoring (e.g., acid-base storage tank pressure-level conversion): Precision of ±0.5%~±1.0% F.S. is sufficient; 

• Safety interlock systems (e.g., overpressure alarms): Precision ≥±0.5% F.S., with emphasis on response speed (≤20ms) rather than extreme precision.

II. Corrosion-Resistant Design: Full-Dimensional Protection from Materials to Structure

Corrosion resistance is the "survival bottom line" of pressure sensors in chemical plants. Selection should follow the logic of "medium adaptation → material matching → structural enhancement" to avoid premature sensor failure due to corrosion. 

1. Core Material Selection: Graded Matching Based on Corrosiveness

2. Structural Enhancement: Improve Corrosion-Resistant Reliability

• Diaphragm isolation design: Adopt welded metal diaphragms (Hastelloy/tantalum) or PTFE isolation membranes to completely isolate core sensor components from corrosive media, avoiding direct contact; 

• Dual-seal structure: Use "metal seal + PTFE seal" double protection to prevent medium leakage into electrical interfaces, especially for high-pressure corrosion scenarios; 

• Protection level upgrade: Sensor housing protection level ≥IP67, and junction boxes adopt explosion-proof sealed design to prevent dust and condensed water from entering and causing short circuits. 

3. Auxiliary Protection Measures: Extend Service Life

• Install corrosion-resistant sleeves: In highly corrosive and particle-containing media, add PTFE or ceramic sleeves to sensor probes to reduce wear and erosion; 

• Medium pretreatment: Remove solid particles from media through filters to reduce probe wear; for easily crystallizable media, install heat tracing devices to prevent crystal adhesion; 

• Regular calibration: Corrosive media will slowly erode probes. It is recommended to calibrate every 3~6 months to promptly correct precision drift.

III. Precision Control: Key Techniques for Maintaining "Accuracy" in Corrosive Environments

High temperatures, corrosion, and vibration in chemical working conditions can cause sensor precision drift. Selection must consider both "basic precision" and "environmental adaptability" to avoid precision indicators being "theoretical." 

1. "Reasonable Trade-Off" in Precision Class

• Core principle: Precision class ≤ allowable pressure fluctuation range of the process × 0.5 (reserve safety redundancy).

Example: If the allowable pressure fluctuation of a reaction kettle process is ±0.05MPa (working pressure 1.0MPa), the sensor precision must be ≤±0.025MPa, corresponding to a precision class of ±0.25% F.S. (select 0~2.0MPa range); 

• Avoid "precision excess": If the allowable pressure fluctuation for storage tank monitoring is ±0.1MPa (working pressure 2.0MPa), selecting a sensor with ±0.1% F.S. precision (cost increased by 40%) cannot reflect advantages in practical applications. 

2. Anti-Interference Design: Offset Environmental Impact on Precision

• Temperature compensation function: Select sensors with "wide temperature range temperature compensation (-40℃~150℃)" to correct precision drift caused by temperature through built-in compensation chips; 

• Vibration and electromagnetic interference resistance: Pumps and compressors in chemical workshops generate vibration (≤10g). Sensors must pass IEC 60068-2-6 vibration testing to ensure precision drift ≤±0.03% F.S./g under vibration; simultaneously support EMC electromagnetic compatibility certification (EN 55011) to resist electromagnetic interference from frequency converters and motors; 

• Static pressure compensation: For deep storage tanks (static pressure ≥1MPa), select sensors with static pressure compensation function to avoid zero drift caused by static pressure. 

3. "Precision Adaptation" of Sensor Types

Different types of pressure sensors have significant differences in precision characteristics and corrosion adaptability, requiring targeted selection: 

• Capacitive pressure sensors: Precision ±0.075%~±0.2% F.S., strong corrosion resistance (supports PTFE lining), suitable for precision reaction processes; 

• Piezoresistive pressure sensors: Precision ±0.1%~±0.5% F.S., moderate cost, requiring corrosion-resistant diaphragms, suitable for medium-low corrosion and general precision scenarios; 

• Ceramic pressure sensors: Precision ±0.2%~±1.0% F.S., inherently corrosion-resistant (inert ceramic material), suitable for highly corrosive and low-precision requirements (e.g., storage tank monitoring).

IV. Balancing Techniques for Corrosion Resistance and Precision: 4 Practical Methods

1. Selection Based on "Corrosiveness Priority" of Media

• Highly corrosive media (e.g., hydrofluoric acid): Prioritize corrosion resistance, select PTFE-lined + ceramic probe or tantalum material sensors, and appropriately relax precision (e.g., ±0.5% F.S.) to avoid rapid sensor failure due to incorrect material selection; 

• Weakly corrosive media (e.g., ethanol): Prioritize precision, select 316L stainless steel + high-precision capacitive sensors (±0.1% F.S.) to balance cost and performance. 

2. Use "Technical Means" to Reduce Precision Loss

• In corrosive environments, sensor precision will decrease year by year due to probe erosion (annual drift ±0.1% F.S.). Select intelligent sensors with "self-calibration function" to perform regular automatic calibration through PLC or upper computer, maintaining long-term precision; 

• For high-temperature corrosion scenarios (e.g., 180℃ sulfuric acid reaction kettles), select "high-temperature isolated sensors" to isolate media from core components through capillary tubes, achieving both corrosion resistance and avoiding high-temperature impact on precision. 

3. "Optimal Solution" for Cost and Performance

• Critical processes (e.g., reaction kettles): Adopt "high corrosion resistance + high precision" combination (Hastelloy C-276 + capacitive, precision ±0.1% F.S.). Although the initial cost is high, the service life can reach more than 5 years, resulting in lower comprehensive operation and maintenance costs; 

• Non-critical processes (e.g., raw material storage tanks): Adopt "basic corrosion resistance + medium precision" combination (316L stainless steel + piezoresistive, precision ±0.5% F.S.) to reduce initial investment while meeting monitoring requirements. 

4. Refer to "Industry-Proven Solutions" to Avoid Trial and Error

• Strong acid processes (e.g., sulfuric acid production): Adopt "PTFE-lined diaphragm sensors + temperature compensation," which has been verified in factories such as BASF and Dow Chemical, with service life ≥3 years and precision drift ≤±0.2% F.S./year; 

• Halogenation processes (e.g., fluorochemical industry): Select "tantalum material sensors + double-seal structure," suitable for Zone 1 explosion-proof areas, precision ±0.25% F.S., meeting harsh corrosion resistance and safety requirements.

V. Selection Pitfalls: 4 Common Mistakes and Solutions

Pitfall 1: Using 316L Stainless Steel for All Corrosive Media

• Wrong Performance: Using 316L stainless steel sensors in fluoride or chlorine gas environments, resulting in probe corrosion and precision failure within 1~3 months; 

• Solution: Select PTFE lining or tantalum material for fluoride media, and Hastelloy C-276 for chlorine gas environments, avoiding "one-size-fits-all" material selection. 

Pitfall 2: Blind Pursuit of "Ultra-High Precision" While Ignoring Corrosion-Resistant Life

• Wrong Performance: Selecting ultra-high precision sensors (±0.05% F.S.) in highly corrosive scenarios, but due to insufficient material corrosion resistance, precision drifts to ±0.5% F.S. after 6 months, which is no different from ordinary precision sensors; 

• Solution: First meet corrosion resistance requirements, then match precision. For highly corrosive scenarios, precision ≤±0.5% F.S. is sufficient, and maintain precision through regular calibration. 

Pitfall 3: Ignoring the Impact of Installation Methods on Corrosion Resistance and Precision

• Wrong Performance: Using insertion installation in slurry media, resulting in probe wear by solid particles, which accelerates corrosion and reduces precision; 

• Solution: Adopt flange installation with the probe parallel to the medium contact surface to reduce wear; or select remote-sealed sensors to install the probe away from medium flow. 

Pitfall 4: Neglecting Explosion-Proof and Compliance Certifications

• Wrong Performance: Using sensors without ATEX certification in Zone 1 explosion-proof areas, which not only violates safety regulations but may also cause explosions due to electrical sparks; 

• Solution: Select CE+ATEX certification for the European market, UL+FM certification for the US market, and comply with GB 3836 explosion-proof standards for the Chinese market, while meeting REACH/RoHS environmental requirements.

VI. Ultimate Checklist for Pressure Monitoring Selection in Chemical Plants

✅ Clarify medium type and corrosion level, and match corresponding corrosion-resistant materials (316L/Hastelloy/PTFE/tantalum) 

✅ Determine precision class based on the allowable pressure fluctuation range of the process (avoid excess or insufficient precision) 

✅ Verify working condition parameters (temperature/pressure/vibration), and select models with temperature compensation and anti-interference functions 

✅ Confirm explosion-proof level (Zone 1/2) and certifications (ATEX/IECEx/GB 3836) to meet safety requirements 

✅ Select appropriate installation methods (insertion/flange/remote seal) to adapt to medium status (pure/particle-containing/easily crystallizable) 

✅ Prioritize intelligent sensors (with self-calibration/data upload functions) for critical processes, and control costs for non-critical processes 

✅ Verify compatibility between materials and media (refer to corrosion-resistant material tables provided by suppliers, and conduct immersion tests if necessary) 

Conclusion

The core of pressure monitoring selection in chemical plants is to "pursue reasonable precision on the basis of corrosion resistance"—corrosion resistance determines the "service life" of sensors, and precision determines the "practical value" of monitoring, neither of which can be neglected. Through the four-step logic of "medium grading → material matching → precision trade-off → technical optimization," it is possible to avoid frequent replacements due to corrosion and cost waste caused by over-pursuit of precision. 

Ultimately, the essence of selection is "adaptation": matching the sensor's corrosion resistance to the medium erosion degree, precision class to process requirements, and cost to application scenarios, in order to achieve safe, stable, and efficient operation of chemical production. 

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