AUTO Instrument Popular Science｜Field Instrument Checklist: Avoid Humidity Vibration Corrosion Induced Failures

AUTO Instrument Popular Science｜Field Instrument Checklist: Avoid HumidityVibrationCorrosionInduced Failures

 Introduction

For industrial‑site equipment including pressure transmitter, differential pressure transmitter, gauge pressure transmitter, dp transmitter working under vibration, humidity, corrosion and alternating temperature conditions,AUTO Instrument sorts out a standardized on‑site instrument inspection checklist. Standard inspection covers not only instrument display reading, but also instrument body, impulse lines, cable wiring, grounding, explosion‑proof measures and installation environment. Combined with the management requirements of pressure transmitter calibration, it helps operation and maintenance personnel identify hidden risks such as water ingress, leakage, loose wiring and signal fluctuation in advance, and reduce the risk of unplanned shutdown caused by equipment failure.

 I. Industry Fact: Harsh Working Conditions Are Main Triggers of Instrument Failures

Various field instruments including pressure transmitter, differential pressure transmitter, pressure gauges, valve positioners, temperature instruments and gas detectors are continuously exposed to vibration, humidity, corrosion and day‑night temperature swing. They are prone to failures such as water ingress, medium leakage, loose wiring and signal jumping.

Many operation‑maintenance personnel only check whether the instrument screen has readings, ignoring inspection of instrument body, impulse lines, cables, grounding, explosion‑proof components and installation environment. Minor hidden risks keep accumulating and eventually lead to measurement distortion and false interlock action.

Inspection should never focus merely on display readings. Instrument body, pipelines, cables, grounding, explosion‑proof devices and operating environment all matter. Periodic management shall be implemented and pressure transmitter calibration shall be performed on schedule to guarantee measurement accuracy.

 II. Core Highlights: Modular Standard Inspection Items

 1. Inspection of Various Instrument Bodies

 Pressure Gauges & Differential Pressure Gauges

‑ Check for water droplets, mist or moisture inside the gauge.

‑ Check whether pointers are stuck, jumping, bent or fallen off.

‑ Check whether dial scale, measuring range, unit and tag number are legible.

‑ Check whether housing, glass and connection parts are damaged, corroded or leaking.

‑ Check whether calibration labels are intact and within valid period.

‑ Check for continuous vibration or frequent pointer swing during operation.

‑ Check whether alarm and interlock set‑points of electric‑contact pressure gauges conform to operating requirements.

 Transmitters (pressure transmitter / differential pressure transmitter / gauge pressure transmitter / dp transmitter, including pressure, differential‑pressure, level, material‑level and temperature transmitters)

‑ Check whether housing, terminal chamber and cable entry have water ingress or moisture.

‑ Check whether displayed value, unit and status information are normal.

‑ Check whether obvious deviation exists between local reading and control‑system reading.

‑ Check for leakage at manifold, impulse joints and drain ports.

‑ Check whether instrument brackets, protective covers and fixing parts are loose or corroded.

‑ Check whether unused ports are plugged with plugs complying with site requirements.

‑ Check status of positive / negative pressure sides and manifold for differential‑pressure measurement loops.

 Valve Positioners and Pneumatic Accessories

‑ Check whether positioner, feedback lever and mounting bracket are firmly fixed.

‑ Check air‑supply joints, output joints and tube connections for air leakage.

‑ Check whether valve action shows creeping, oscillation, hysteresis or incomplete stroke.

‑ Check whether positioner opening indication matches actual valve position.

‑ Check whether filter‑regulator, pressure gauge and drain device work normally.

‑ Check for leakage at actuator, valve‑stem packing and diaphragm‑head connections.

 Gas Detectors and Acousto‑Optic Alarms

‑ Check whether equipment housing, junction box and mounting bracket are damaged or loose.

‑ Check for water ingress, condensation or moisture inside.

‑ Check whether detector inlet is blocked by dust, oil stain or foreign objects.

‑ Check status indication; check for fault or communication abnormality.

‑ Check whether calibration, inspection and sensor‑replacement labels are within valid period.

‑ Verify alarm and interlock function with standard gas if conditions permit.

 Temperature Instruments

‑ Check whether temperature elements, transmitters and protection sleeves are firmly installed.

‑ Check whether compensating wires or extension cables touch high‑temperature surfaces.

‑ Check whether local readings and control‑system readings are reasonable and stable.

‑ Check whether junction boxes, cables and protection conduits have water ingress or damage.

‑ Check protection sleeves and their connections for leakage, corrosion and vibration.

 2. Inspection of Pipelines and Accessories

 Impulse Lines and Pressure Pipelines

‑ Check neat arrangement and reliable support & fixation of pipelines.

‑ Check joints, ferrule fittings, welds and valve connections for leakage.

‑ Check pipelines for vibration, corrosion, cracks, flattening or deformation.

‑ Check friction against cables, air tubes or equipment housing.

‑ Check whether pipeline gradient, routing, heat tracing and thermal insulation comply with site requirements.

‑ Check for liquid accumulation, gas accumulation or blockage.

 Manifolds, Drain Valves and Vent Ports

‑ Check whether manifold position matches current operating condition.

‑ Check equalizing valves, isolating valves and drain valves for correct status.

‑ Check whether valve handles, bonnets and plugs are intact.

‑ Check drain ports, vent ports and exhaust ports for blockage.

‑ Check whether silencers, filters and rain‑proof caps are complete.

‑ Confirm valves are fully closed after draining or venting operation.

 Capillary Tubes

‑ Check whether capillaries lie on ground, scatter or stay in tram‑prone positions.

‑ Check neat coiling and reliable fixation.

‑ Check for bending, flattening, twisting or corrosion.

‑ Check sufficient clearance from high‑temperature surfaces, sharp edges and moving components.

 3. Cable, Wiring and Grounding Inspection

 Cables and Wiring

‑ Check neat cable arrangement and reliable support.

‑ Check contact with high‑temperature, vibrating or rotating equipment.

‑ Check cable sheath for aging, cracking, crushing or abrasion.

‑ Check cable sealing glands and terminals for looseness, moisture or corrosion.

‑ Check legibility of wire numbers, terminal numbers and cable IDs.

‑ Check intrinsic‑safe / non‑intrinsic‑safe / signal / power cables are separated as per design.

‑ Check rain‑proof measures for cable entries of outdoor junction boxes.

 Grounding System

‑ Check reliable earthing for instruments, solenoid valves and junction‑box housings.

‑ Check integrity of earthing conductors, terminals and bridge jumpers.

‑ Check earthing wires for corrosion, strand breakage or looseness.

‑ Check clear branches for each equipment earthing circuit.

‑ Check shield‑layer grounding mode of signal cables complies with design.

‑ Check earthing contact surfaces free of paint, rust and dirt.

 Limit Switches and Junction Boxes

‑ Check integrity of housing, cover plates and sealing rings.

‑ Check for water ingress, condensation or corrosion inside.

‑ Check terminals, cams and feedback mechanisms for looseness.

‑ Check whether switch position feedback matches actual valve position.

‑ Check all unused cable ports are properly blocked.

 4. Explosion‑proof and Marking Inspection

 Explosion‑proof Facilities

‑ Check cable glands, plugs and accessories meet site explosion‑proof requirements.

‑ Check all unused ports are reliably blocked.

‑ Check explosion‑proof housing for cracks, corrosion or missing fasteners.

‑ Check integrity of sealing rings, compression devices and threaded connections.

‑ Check legibility of equipment explosion‑proof marks and nameplates.

‑ Check flexible conduits for damage, falling‑off or excessive bending.

 Labels and Markings

‑ Check completeness and legibility of tag plates, nameplates and calibration labels.

‑ Check label contents match field equipment.

‑ Check labels are within valid period; perform work such as pressure transmitter calibration when due.

‑ Check cable ties and fasteners for aging or loosening.

‑ Check labels do not block display screens, nameplates and operating positions.

 5. Environment and Installation‑status Inspection

‑ Check instrument surroundings for ponding, oil contamination, sundries or corrosive pollutants.

‑ Check exposure to high temperature, vibration, salt mist, steam or flushing water.

‑ Check instruments, brackets, protection boxes and bases for looseness, corrosion or deformation.

‑ Check completeness of cable‑tray covers and internal ponding.

‑ Check unobstructed access for maintenance and operation.

‑ Check no long‑term retention of temporary supports, iron‑wire binding or wooden block shimming.

‑ Listen for abnormal noise, peculiar smell, air‑leak sound or signal fluctuation during operation.

 III. Scenario Value: Specification and Application Value of Inspection Records

Avoid vague entries such as “Normal” or “Abnormal”. Write down specific location plus real‑world phenomenon for convenient maintenance, pressure transmitter calibration and fault traceability.

Reference record examples:

1. Slight mist observed inside pressure gauge; reading is temporarily normal.

2. Moisture trace found in terminal chamber of pressure transmitter; sealing gland needs inspection.

3. Slight air leakage exists at air‑supply joint of valve positioner.

4. Fixing point of impulse line is loose with swing during operation.

5. Cable‑tray cover missing with small amount of ponding inside.

6. Deviation exists between local reading of differential pressure transmitter and control‑system reading; inspection and calibration are recommended.

Actual inspection items shall be adjusted according to process conditions, instrument types, operating environment and historical faults of the plant to form a dedicated inspection checklist. Standardized inspection eliminates numerous faults at early stage and reduces unplanned failures of pressure transmitter, differential pressure transmitter, gauge pressure transmitter, dp transmitter.

 IV. Supplementary Conclusion

Field‑site equipment such as pressure transmitter and differential pressure transmitter work continuously under vibration, humidity, corrosion and alternating temperature. Failures seldom occur instantaneously but develop from accumulated hidden defects.

Complete inspection cannot merely rely on screen readings. It shall cover instrument body, impulse lines, capillaries, cable wiring, grounding, explosion‑proof structures and installation environment. Meanwhile, implement periodic management of pressure transmitter calibration. Execute the checklist to identify water‑ingress, leakage, loose wiring and signal drift in advance and ensure stable performance of the whole measurement system.

AUTO Instrument provides full‑series products including pressure transmitter, differential pressure transmitter, gauge pressure transmitter and dp transmitter. In accordance with periodic requirements for pressure transmitter calibration, we offer type‑selection support, installation guidance and operation‑maintenance suggestions to help stable operation of plant instrument systems.