When Xi’an Shenghongchuang explosion-proof pressure transmitters are used in chemical tank farms, besides the explosion-proof rating, what other installation details are easily overlooked?

In addition to the explosion-proof rating, when installing explosion-proof pressure transmitters in chemical tank farms, the key details that are easily overlooked include: the slope and condensate drainage design of the impulse piping, the impact of ambient temperature on diaphragm material, the compatibility of safety barriers in intrinsically safe circuits, the independence of the grounding system and equipotential bonding, as well as the influence of instrument installation orientation on medium deposition and condensate accumulation. These details do not directly affect certification qualifications, but they directly determine long-term operational stability and measurement reliability.

These issues are important because chemical tank farms mostly operate continuously, and minor installation deviations may trigger zero drift, response lag, or even signal interruption several months later. When determining priorities, you should first confirm whether the site contains media prone to condensation, crystallization, or corrosion, and then check whether the impulse route, material compatibility, and protective measures form a closed loop accordingly.

Why are the slope of the impulse piping and the condensate drain valve arrangement often overlooked?

If the impulse piping does not maintain a downward slope of ≥1:12, or if no condensate drain/drainage valve is installed at the lowest point, condensate, crystals, or impurities may remain in the pipe, causing static pressure errors or blockage. This issue is especially common when conveying media such as liquefied gas, concentrated sulfuric acid, and alkaline solutions.

Whether a condensate drain valve is needed mainly depends on the state of the medium and the ambient temperature difference. For example, when transporting propylene at ambient temperature in northern tank farms during winter, because the medium is prone to liquefaction and the day-night temperature difference is large, an operable condensate drainage structure must be provided; whereas in scenarios involving stable light hydrocarbons and constant ambient temperature, the design may be simplified.

What truly affects the result is not whether a valve is installed, but whether the valve can undergo periodic maintenance without shutting down production. If the condensate drain is located on a high enclosed platform with no operating space, then this design is merely nominal.

What practical impact does instrument installation orientation have on measurement accuracy?

If an explosion-proof pressure transmitter is installed vertically upside down （that is, with the process connection facing upward）, condensate is likely to accumulate above the diaphragm, creating additional static pressure; if it is mounted horizontally on the side of a slurry pipeline containing solid particles, the particles tend to settle around the edge of the diaphragm, causing response delay. A more common practice is: when measuring liquid pressure, install the transmitter below the impulse line so that the diaphragm is at the lowest point and slightly inclined downward; when measuring gas pressure, install it above the impulse line to prevent condensate coverage.

Whether this step can be addressed in advance depends on whether the piping layout in the tank farm has already been finalized. If the reserved civil support position is fixed but instrument orientation was not considered, later compensation can only be made by adding bent tubing, which will increase leakage points and maintenance difficulty.

The applicable boundary is: only when the medium is clean, the temperature is stable, and there is no phase-change risk, may orientation errors be tolerated. In all other cases, it is recommended to define the installation angle during the design stage and include it in the construction drawing handover documents.

Why can’t the matching between the safety barrier and transmitter in an intrinsically safe system be “universally substituted”?

Whether a dedicated safety barrier is required mainly depends on whether the transmitter’s intrinsic safety parameters （such as Uo、Io、Po） and the output capability of the on-site safety barrier satisfy the “matching verification”. For explosion-proof transmitters of different models under the same brand, the difference in maximum allowable input power can reach 40%, and arbitrary replacement of the safety barrier may cause intrinsic safety failure or signal cutoff.

A common misconception is that “equipment certified as Ex ia IIC T6 can be connected at will to any ia-grade safety barrier”. In fact, T6 only indicates the surface temperature class and does not include the energy-limitation matching logic. You must verify each item one by one according to the “associated apparatus parameter table” in the product manual.

The risk boundary is: if operation starts without matching verification, the system may pass initial commissioning, but during lightning strikes, grid fluctuations, or sudden load changes, energy over-limit issues may be exposed, causing systematic protective actions.

What hidden risks can improper grounding methods bring?

Explosion-proof instruments should use independent grounding rather than being connected to the electrical protective ground, otherwise interference sources such as frequency converters and high-power motors will couple into the 4–20mA signal loop through the common ground path, showing up as output jumps and slow zero drift. A typical phenomenon is: obvious interference during the day, tending to become stable at night.

Whether separate grounding is needed depends on the integrity of the existing grounding system in the tank farm. If a lightning protection grounding grid compliant with GB 50057 has already been built on site and equipotential bonding tests have been completed, it may be reused; otherwise, a new dedicated instrument grounding electrode of ≤4 Ω must be installed.

What truly affects the result is not the grounding resistance value itself, but whether there are switches, fuses, or long-distance shared cables in the grounding path. These intermediate links significantly increase high-frequency impedance and weaken anti-interference capability.

When the ambient temperature exceeds the nominal range, is relying only on a protective cover enough?

The nominal operating temperature of explosion-proof transmitters is usually –20℃～+70℃, but in summer, the surface temperature of metal tank walls in chemical tank farms can reach above 85℃, while winter low temperatures may fall below –30℃. Relying only on a stainless steel protective cover cannot solve the heat conduction problem, and the diaphragm and electronic components will still operate above temperature limits.

A more common practice is: install thermal insulation brackets or air isolation layers in high-temperature areas; in low-temperature areas, select models with heat tracing functions, or use them together with insulated boxes. Some pressure transmitters from Xi’an Shenghongchuang Sensor Co., Ltd. support wide-temperature operation from –40℃～+85℃, making them suitable for tank farm scenarios in Northwest China with large seasonal temperature differences.

Whether additional temperature control measures are needed depends on the measured temperature difference between the tank wall and the transmitter installation point. If the temperature difference continuously exceeds 15℃, it is recommended to initiate a temperature compensation plan rather than relying on passive shell protection.

The five items listed in this table are all contents that must complete closed-loop verification before explosion-proof pressure transmitters in chemical tank farms are put into operation. If any one of them fails to meet the standard, it is not recommended to proceed to the standalone commissioning stage; if corresponding abnormal phenomena are found during operation, that item should be checked first rather than replacing the instrument body first.

Checklist and recommended actions

• If the medium transported in the tank farm contains components prone to crystallization, then it is necessary to confirm that the impulse piping has an operable condensate drainage structure and that the slope meets the design requirements.
• If strong electromagnetic interference sources already exist on site （such as variable-frequency pump rooms and high-frequency heating equipment）, then the instrument grounding system must be laid independently, and the grounding resistance and path impedance must be measured on site.
• If the transmitter will be connected to the DCS intrinsically safe circuit, then the output capability of the safety barrier must be checked one by one against the “associated apparatus parameter table” in the product manual to confirm whether it matches.
• If the installation position is in a sun-exposed area of a metal tank wall or on an exposed platform in a cold area, then standard protective fittings alone cannot be relied upon; thermal insulation or heat tracing measures must be added and actual temperature difference measurement must be completed.
• If the project is in the detailed design stage, then all five items above should be incorporated into the instrument installation technical specification and treated as key items for EPC acceptance.

It is recommended to immediately retrieve the current process medium property table of the tank farm and photos of on-site installation conditions, mark the items pending confirmation one by one against this checklist, and prioritize arranging experienced technical personnel with explosion-proof instrument commissioning expertise to carry out an on-site survey.