1、 Display abnormal faults

1. No display or garbled text on the screen

• Possible reasons：
  • power failureThe fuse inside the explosion-proof junction box is blown (such as 1A/250V slow melting type), or the power cord is damaged, causing a circuit break.
  • Explosion proof enclosure seal failureAfter long-term use, the sealing ring ages and moisture enters the interior of the instrument, causing a short circuit in the circuit board.
  • electrostatic interferenceIn a dusty environment, static electricity accumulation may penetrate the display screen driver chip (such as HT1621B).
• treatment method：
  • Check the voltage of the power cord (stable at 220V ± 10%) and replace the fuse with the same specification.
  • Use an air tightness tester (such as negative pressure method) to check the enclosure protection level (should reach IP65 or above), and replace the sealing ring.
  • Connect an anti-static grounding wire (resistance ≤ 4 Ω) to the instrument grounding terminal and regularly clean the dust on the equipment surface.

2. Large fluctuations in weight display

• Possible reasons：
  • Sensor signal interferenceExplosion proof cables (such as the intrinsic safety type ZR-IASP-2 × 1.5) are damaged, resulting in signal attenuation.
  • Vibration impactThe device is installed near the vibration source (such as next to the compressor), and the sensor output is unstable.
  • temperature driftExplosion proof sensors are not equipped with temperature compensation modules, resulting in changes in resistance values in low-temperature environments.
• treatment method：
  • Use a megohmmeter to measure the insulation resistance of the cable (should be ≥ 500M Ω), and replace the damaged cable.
  • Install shock-absorbing pads (such as rubber isolators with a bearing capacity of ≥ 5 tons) between the foundation of the weighing apparatus and the ground.
  • Choose explosion-proof sensors with temperature compensation (such as HBM C9C type, compensation range -20 ℃ to+60 ℃).

2、 Inaccurate measurement fault

1. Weight deviation exceeds the standard

• Possible reasons：
  • Sensor malfunctionThe internal strain gauges of explosion-proof sensors fall off (commonly after overload impact), or the bridge resistance is unbalanced.
  • Angle difference not correctedUneven force distribution on the four corner sensors (such as when a certain corner is suspended due to deformation of the tabletop).
  • The limit device is too tightThe gap between the limit bolt of the explosion-proof weighing instrument and the scale body is less than 2mm, which limits the free floating of the scale body.
• treatment method：
  • Use a multimeter to detect the sensor output signal (0mV ± 0.1mV when unloaded and 2mV/V ± 0.05mV when fully loaded), and replace the abnormal sensor.
  • By using the instrument angle correction function (such as the "Corner Cal" mode of Mettler Toledo IND331), standard weights (such as 20kg) are loaded at each corner for calibration.
  • Adjust the gap between the limit bolts to 3-5mm and apply anti rust grease (such as Molykote X-5).

2. Large repeatability error

• Possible reasons：
  • Explosion proof junction box water ingressPoor sealing of the junction box leads to internal oxidation and increased contact resistance.
  • sensor agingFatigue of sensor elastomer after long-term use (such as aluminum sensors used for more than 5 years).
  • Improper software filtering parametersThe instrument filtering time is set too short (e.g.<0.5 seconds), which does not effectively suppress vibration interference.
• treatment method：
  • Disassemble the junction box, clean the contacts with alcohol and apply conductive paste (such as DEOXIT D5), and reseal.
  • Replace the stainless steel sensor (such as HBM Z6FD1 type, with a lifespan of over 10 years).
  • Adjust the filtering time to 1-2 seconds in the instrument parameter settings (such as the "Filter Time" option of the Sartorius BSA series instrument).

3、 Explosion proof function failure type fault

1. The explosion-proof certification mark is blurred or detached

• Possible reasons：
  • Shell corrosionIn the chemical environment, acid and alkali gases corrode explosion-proof coatings (such as epoxy resin coatings).
  • mechanical damageScratching the explosion-proof casing during transportation or installation, resulting in metal exposure in the marked area.
• treatment method：
  • Polish the corroded area with sandpaper (800 grit) and reapply explosion-proof paint (such as DuPont Corlar 220).
  • Contact the manufacturer to reprint the explosion-proof label (including Ex mark, equipment category, temperature group, etc.), and affix the explosion-proof certificate seal.

2. Inherent safety circuit short circuit

• Possible reasons：
  • Cable selection errorReplace intrinsic safety cables with non explosion proof cables (such as regular RVV cables).
  • wrong connectionMixing the power line with the signal line causes the current to exceed the safe threshold (e.g. maximum current of Ex Ia circuit ≤ 100mA).
• treatment method：
  • Replace the intrinsically safe cable (such as PVC/STP type, with an outer sheath thickness of ≥ 1.8mm).
  • Strictly follow the explosion-proof wiring diagram (such as ATEX certification drawings) to connect the circuit, and use explosion-proof wiring terminals (such as Phoenix UK series).

4、 Mechanical structural faults

1. Deformation or sinking of the scale body

• Possible reasons：
  • Weak foundationThe insufficient strength of the concrete foundation for shallow pit type weighing apparatus (such as C20 replacing C30) leads to settlement after long-term use.
  • Overloaded useFrequent weighing exceeding the measuring range (such as long-term weighing of 15 tons on a 10 ton scale), resulting in deformation of the scale body.
• treatment method：
  • Re pour concrete foundation (thickness ≥ 300mm, reinforcement Φ) 12@200mm ）And maintain for 28 days.
  • Install limit plates (such as Q235 steel plate, thickness 10mm) around the scale body to prevent over range use.

2. Transmission components are stuck

• Possible reasons：
  • Explosion proof motor malfunctionThe lack of oil in the motor bearings (such as the use of No. 3 lithium grease that is not regularly replenished) leads to an increase in rotational resistance.
  • Gear wearThe gearbox of the manual explosion-proof weighing instrument has not been lubricated (such as Shell Omala S2 G 150), and the tooth surface has pitting corrosion.
• treatment method：
  • Add lubricating grease to the motor bearings every 3 months (5-10ml each time) and clean old oil stains.
  • Replace the worn gear (with a tooth surface hardness of HRC58-62) and adjust the gear clearance to 0.1-0.15mm.

5、 Environmental adaptability failure

1. Cannot start in low temperature environment

• Possible reasons：
  • Decreased battery performanceExplosion proof instruments with built-in lithium batteries (such as 3.6V/2.4Ah) experience a capacity decay of over 50% at -20 ℃.
  • Screen LCD freezesThe lower limit of the operating temperature for TN LCD screens is -10 ℃, below which the display becomes blurry.
• treatment method：
  • Replace the low-temperature lithium battery (such as SAFT LS14500, operating temperature -40 ℃ to+85 ℃).
  • Install an electric heat tracing strip (such as a self limiting type with a power of 50W/m) on the instrument casing to maintain an internal temperature of ≥ 0 ℃.

2. Short circuit in high humidity environment

• Possible reasons：
  • Explosion proof shell breathing valve blockedThe breather valve filter is clogged with dust, causing internal condensation.
  • The circuit board has not been treated with three protectionsOrdinary PCB boards are prone to moisture absorption and short circuits in high humidity (>85% RH) environments.
• treatment method：
  • Regularly clean the breather valve filter (once a month), or replace it with a waterproof breather valve (such as GORE-TEX membrane).
  • Spray three proof paint (such as Humisay 1B31, thickness 50-100 μ m) on the circuit board, and bake and cure (80 ℃/1 hour).