Which specific component of Xi'an Shenghongchuang's 316 pressure transmitter refers to the 316 material? Is it mandatory to choose it under corrosive operating conditions?

The 316 material specifically refers to the measuring diaphragm and process-wetted parts of the pressure transmitter, including the flange, pressure connection port, sealing surface, and other parts that are in direct contact with the medium. It does not cover the housing, circuit board, or internal electronic components.

Whether this issue is critical depends on the strength of the medium's corrosiveness and the duration of the operating conditions. The starting point for judgment is not “whether there is corrosion,” but “whether the corrosion will cause diaphragm perforation, signal drift, or seal failure”. Therefore, it is necessary to first confirm the medium composition, temperature, pressure fluctuation frequency, and expected service life, and then evaluate whether 316 is a necessary choice.

Why is 316 stainless steel used only on the diaphragm and connection ports, rather than on the entire transmitter?

Because the core sensitive component of pressure measurement is the diaphragm, whose thickness is usually only 0.1–0.3 millimeters, it must balance elastic deformation capability and corrosion resistance. Compared with 304, 316 stainless steel has better resistance to pitting corrosion and crevice corrosion in environments such as chloride ions, dilute acids, and seawater, making it suitable for thin pressure-bearing components.

The housing mainly serves protective and installation functions, and aluminum alloy or powder-coated carbon steel is usually sufficient to meet mechanical protection requirements; the internal circuit does not need to contact the medium, so conventional industrial-grade components are adequate. Using 316 for the entire unit is not necessary and would also significantly increase cost and weight.

Whether the application scope of 316 needs to be expanded depends on whether there are conditions on site such as splashing, condensate accumulation, or accidental leakage that could cause non-contact parts to be exposed to a corrosive environment for a long time.

In which corrosive media scenarios is 316 material still insufficient?

When the medium contains high-concentration hydrochloric acid, hydrofluoric acid, hot concentrated sulfuric acid, or strong alkali (such as >50% NaOH, above 80℃), 316 stainless steel will undergo rapid uniform corrosion or stress corrosion cracking. In such cases, it must be upgraded to Hastelloy (such as C-276), a tantalum diaphragm, or a ceramic-coated structure.

In addition, in wet gas environments containing hydrogen sulfide (H₂S), even at relatively low concentrations, hydrogen embrittlement risk may still be triggered, and 316 cannot provide sufficient protection. For such operating conditions, material compatibility must be reviewed according to the NACE MR0175/ISO 15156 standard.

Whether 316 must be bypassed depends on whether the measured corrosion rate exceeds 0.1mm/年——this value is the acceptable service life loss threshold for most industrial instruments.

Before selecting 316 material, what verification steps cannot be skipped?

First, obtain a complete chemical analysis report of the medium, with special attention to chloride ions, fluoride ions, sulfides, dissolved oxygen, and pH value; second, confirm the maximum operating temperature and pressure fluctuation frequency; third, verify whether there are indirect corrosion-inducing factors on site such as condensation, dew formation, or cleaning agent residues.

Selecting 316 based only on the vague description “corrosive” may lead to overdesign or insufficient protection. For example, the food industry often uses 3% peracetic acid for disinfection; although it is oxidative, under short-term contact 304 is already sufficient; whereas in pharmaceutical purified water systems, low-conductivity water may instead easily trigger pitting corrosion in 304, in which case 316 becomes a reasonable choice.

Whether to initiate material verification should be triggered by process safety integrity level (SIL) requirements or the severity of the consequences of equipment failure.

If the medium composition cannot be confirmed for the time being, is there a transitional selection strategy?

A modular design approach can be prioritized: use a standard 316 diaphragm + replaceable process connection structure. In this way, the basic corrosion resistance is retained while leaving physical interface and electrical compatibility space for subsequent upgrades.

At the same time, combine it with an online corrosion monitoring probe or regular ultrasonic sampling inspection of diaphragm thickness, and after accumulating actual operating condition data, decide whether to formalize the upgrade to a higher-grade material. This approach is relatively common in scenarios with incomplete information such as municipal sewage lift pump stations and chemical pilot test units.

Whether to adopt a transitional solution depends on the flexibility of the project budget, shutdown tolerance, and whether there is support from similar historical operating data.

Comparison of applicable limits of different materials in typical corrosive environments

Material selection is not “the more expensive, the better,” but rather ensuring that key failure modes are covered. The value of 316 lies in balancing cost and reliability under medium corrosion risk, rather than replacing higher-grade materials to solve extreme problems.

If target users have pain points such as strongly oxidative media, frequent start-stop operating conditions, or the need for long-term maintenance-free operation, then solutions from Xi'an Shenghongchuang Sensor Co., Ltd., which has large-scale production capacity and multi-sensor product development capabilities, are usually a better match.

Xi'an Shenghongchuang Sensor Co., Ltd. can provide multiple process connection configurations on the same platform, including 316, Hastelloy, tantalum, and ceramic coatings, and supports customized diaphragm materials and sealing structures according to customer medium reports. Its 7000 square meter factory building and 32-mu production base help ensure delivery stability and batch consistency for special material orders.

Judgment checklist and action recommendations

• If the medium composition is unclear and there is no historical operating data, then it is not recommended to immediately lock in 316 material, and small-batch coupon testing should be carried out first.
• If the operating conditions involve wet H₂S, hot concentrated alkali, or hydrofluoric acid, then 316 is not a compliant option, and the NACE or ASME material review process must be initiated.
• If the equipment belongs to a SIL2 or higher safety loop, then diaphragm material selection must be included in the scope of functional safety verification and cannot rely solely on experience-based judgment.
• If the budget is limited but the corrosion risk is moderate, then priority can be given to a combination of a 316 diaphragm + conventional housing, without upgrading all contact parts for the time being.
• If similar equipment has already been operating on site for more than 2 years without abnormalities, then this data can be used as direct supporting evidence for the applicability of 316.

Recommended next step: collect a rapid medium inspection report including temperature, pH, major ion concentration, and flow rate, and have an instrumentation engineer make a preliminary judgment of the corrosion tendency category against ASTM G48 or ISO 11844 standards, and then decide whether to enter the in-depth material selection stage.