Introduction: symptom of an explosion, causing investigation

During regular technical maintenance of a company producing based on rotor pumps in the Donetsk region, an explosion of the bearing in the FIBRO 0676221 pump was detected. The explosion occurred as a result of bearing damage, leading to rotor explosion and production stoppage. The explosion was characterized by a high level of noise, higher temperature regime and vibration exceeding the permissible limits. During inspection, electrical erosion roughness on the bearing surface was detected, indicating the influence of currents induced by frequency converters (VFD).

Component overview: function, location, operating conditions

FIBRO 0676221 is a rotor pump with bearings, used in systems for transporting liquids with high humidity. Bearings are mounted on the pump shaft, which rotates at a speed up to 1500 rpm. The operating temperature around the bearings does not exceed 85 °C, and an explosion in case of incorrect use of VFD may lead to an increase in temperature up to 120 °C. Vibration within acceptable limits should be less than 4.5 mm/sec, but at the time of explosion it exceeded 8.2 mm/sec.

Explosion evidence: what the technician sees (photos, measurements, vibration data)

The following signs of an explosion were found during inspection:

• Electro-erosion roughness on the surface of suspensions, indicating current influence.
• High noise level (up to 90 dB), indicating vibration disturbances.
• Вища температура в області підвісок (112 °C) порівняно з номінальною (85 °C).
• Vibration was higher than permissible (8.2 mm/sec) by 40 %.
• Microcracks on the suspension surface, indicating mechanical stresses.

Vibration measurement computer system (VIBRO-3000) showed high vibration level in the range of 1–10 kHz, indicating suspension failure.

Root cause analysis: systematic analysis (5 Whys, Ishikawa, or failure tree)

For determining the cause of the explosion, the 5 Whys method was used:

1. Why did the explosion occur? — Due to the influence of currents induced by VFD on the suspensions.
2. Why are currents induced? — due to high rotational speed and incorrect insulation selection.
3. Why was the insulation selection incorrect? — due to the absence of appropriate VFD usage instructions.
4. Why was there no appropriate instruction? — due to insufficient technical training of the maintenance personnel.
5. Why was technical training not conducted? — due to the absence of mandatory requirements in the standard DSTU 1859-96.

Other methods, such as Ishikawa, showed that the main cause of the explosion was the absence of insulation on the suspensions, leading to the generation of currents.

Definition of the cause of explosion: sorted causes with probability and supporting evidence

The following is a list of explosion causes, sorted by probability:

1. Lack of insulation on the hangers (probability: 75 %). The hangers were not properly insulated, resulting in the generation of currents.
2. Incorrect VFD selection (probability: 20 %). Use of VFD with insufficient insulation level.
3. Inadequate technical training (probability: 5 %). Non-compliance of personnel with standards DSTU 1859-96.

Evidence includes the detection of electrical erosion roughness, high temperature and vibration.

Corrective actions: immediate correction + long-term prevention for each cause

The following corrective actions are provided for each defined explosion:

1. Absence of insulation — immediate action: installation of insulation layers on hangers. Long-term prevention: use of hangers complying with standard EN 13445.
2. Incorrect VFD selection — immediate fix: replacement with VFD having high insulation level. Long-term prevention: use of VFD complying with standard IEC 61800-5.
3. Inadequate technical training — immediate action: conducting mandatory training for personnel. Long-term prevention: use of technical training materials compliant with the DSTU 1859-96 standard.

Quick diagnostic check: 12 points for the technician in mobile mode

1. Check vibration using VIBRO-3000. Allowable level — less than 4,5 mm/sec.
2. Measure the temperature in the suspension area. Permissible temperature — up to 85 °C.
3. Check for absence of electrical erosion roughness on the suspensions.
4. Check the insulation compliance with standard EN 13445.
5. Check the VFD selection using IEC 61800-5.
6. Perform vibration analysis in the range of 1–10 kHz.
7. Check the compliance of technical training to DSTU 1859-96.
8. Measure the noise level. Permissible level — up to 85 dB.
9. Check the compliance of variable voltages to the standard EN 50112.
10. Measure the resistance level on the suspensions. Allowable level — more than 1 MOhm.
11. Check the compliance of the hangers to the standard ISO 14214.
12. Use the test stand to determine the effect of VFD on suspension.
13. Record the results in the service system.
14. Perform the appropriate actions depending on the results.

Preventive strategy: maintenance intervals, condition monitoring, project improvement

To prevent similar explosions, it is necessary:

• Виконувати регулярне обслуговування кожні 1500 годин роботи.
• Use condition monitoring with vibration and temperature sensors.
• Provide technical training for personnel, in accordance with DSTU 1859-96.
• Вибирати підвіски з високим рівнем ізоляції, відповідно до EN 13445.
• Використовувати VFD, відповідні до IEC 61800-5.
• Perform analysis of electrical erosion roughness on suspensions.
• Use appropriate means for measuring the resistance level on suspensions.

Callout from the UNITEC-D E-Catalog

It is important to consider the risks associated with the use of VFD during maintenance in Ukraine. Explosion of suspensions may lead to significant losses, therefore regular maintenance, use of appropriate standards and technical training should be carried out. To obtain components compliant with standards EN 13445, IEC 61800-5 and DSTU 1859-96, visit UNITEC-D E-Catalog.

UNITEC-D E-Catalog

List of used standards and recommendations

1. DSTU 1859-96 — Requirements for Technical Training.
2. EN 13445 — Suspension Requirements.
3. IEC 61800-5 — Requirements for VFD.
4. ISO 14214 — Vibration Measurement Requirements.
5. EN 50112 — Requirements for variable voltages.
6. VIBRO-3000 — Vibration Meter.
7. UNITEC-D — Component Information.

1. Problem Description and Scope

This guide is intended for systematic diagnosis and correction of errors in industrial intermediate devices (VFD), specifically: overload, overvoltage, grounding and communication errors. It covers industrial devices used in automotive specialized production, air engineering, food industry, chemical and energy sectors. Errors are classified as critical and medium importance, depending on their impact on the production process.

2. Safety and Measures

Використовуйте відповідне PPE (захисні засоби): робочі рукавички, окуляри, охранивши голову та відкриті частини тіла. Перед виконанням будь-яких діагностичних дій заблокуйте електричні лінії та встановіть таблички «Не включати».

Warning: Disconnect the power supply and remove the connections before performing any diagnostic procedures to avoid hazards.

3. Required diagnostic tools

4. First inspection before diagnosis

5. Systematic Diagnostic Scheme

1. Symptom: Continuous tripping of VFD
   1. Check the input voltage (measure between phases and neutral)
   2. If the input voltage is normal, check the output power supply current
   3. If the current is normal, check the engine vibration
   4. If vibration is within normal limits, check the engine temperature
2. Symptom: Grounding Fault
   1. Measure the ground resistance between the VFD housing and the grounding
   2. If the resistance exceeds 10 Ohms, perform grounding
   3. If the resistance is within normal range, check the electrical connections
   4. If the connection is normal, check the cable insulation
3. Symptom: Communication Error
   1. Check the communication cable connections
   2. If the connection is normal, check the cable impedances
   3. If impedance is normal, check for noises in the network
   4. If noise is absent, check the VFD

6. Cause and Effect Matrix

7. Root Cause Analysis

7.1 Overload

VFD overload may be caused by incorrect settings or improper motor operation. Incorrect settings may lead to exceeding the nominal current. Improper motor operation may cause higher vibration or temperature, leading to overload.

To confirm this cause, check the VFD settings and compare them with the motor's nominal values. Measure the motor's vibration and temperature. If the values exceed the permissible limits, this confirms the root cause.

7.2 Overvoltage

Overvoltage may be caused by incorrect power supply or incorrect filter operation. Incorrect power supply may lead to higher input voltage. Incorrect filter operation may lead to lack of filtering, resulting in overvoltage.

To confirm this cause, check the input voltage and the status of the filters. If the voltage is higher than 450 V or the filter is blocked, this confirms the root cause.

7.3 Earthing

Grounding may be caused by incorrect grounding or incorrect connections. Incorrect grounding may lead to higher resistance, which causes grounding. Incorrect connections may cause a break or corrosion.

To confirm this cause, measure the earth resistance and check the cable connections. If the resistance is more than 10 Ohm or there is a break, this confirms the root cause.

7.4 Communication Error

Communication error may be caused by incorrect connection or incorrect cable impedance. Incorrect connection may lead to breakage or corrosion. Incorrect impedance may lead to higher resistance, resulting in communication error.

To confirm this cause, check the cable connections and measure the impedance. If there is a break or impedance higher than 100 Ohms, this confirms the root cause.

8. Step-by-step correction procedures

8.1 Overload

1. Check the VFD settings and compare with the motor's nominal values.
2. If the settings are incorrect, adjust them using the VFD application.
3. Measure the engine vibration. If the vibration is higher than 4.5 mm/s, perform balancing.
4. Measure the engine temperature. If the temperature is higher than 95°C, perform cooling.
5. After correction, check the VFD for functionality.

8.2 Overvoltage

1. Check the input voltage. If it is higher than 450 V, disconnect the power.
2. Perform filter check. If the filter is blocked or clogged, replace it.
3. Measure the input voltage again. If the voltage is within normal range, turn on the power.
4. Check the VFD for functionality.

8.3 Earthing

1. Measure the earth resistance. If the resistance is more than 10 Ohm, perform earthing.
2. Check the cable connections. If there is a break or corrosion, restore the connection.
3. Measure the earth resistance again. If the resistance is within normal limits, turn on the power.
4. Check the VFD for functionality.

8.4 Communication Error

1. Check the cable connections. If there is a break or corrosion, restore the connection.
2. Measure the cable impedance. If the impedance is higher than 100 Ohm, replace the cable.
3. Check the VFD firmware. If there are errors, restore the firmware.
4. Check the VFD for functionality.

9. Maintenance Methods

10. Replaceable Parts and Components

Go to UNITEC-D catalog

11. References

• DSTU 2181:1999 – Requirements for Electrical Equipment
• EN 60034-2-1:2007 – Requirements for Electric Motors
• ISO 14224:2012 – Electrical System Diagnosis
• CE and UkrSEPRO certification
• Original manufacturer instructions
• Additional Guides UNITEC-D

1. Purpose and scope of application

This how-to guide is performed to perform pre-security checks, fan cleaning, capacitor checks, and firmware updates on industrial variable frequency drives (VFDs). The protocol is performed once every 6 months or after 1000 hours of operation. It is intended for operation in the conditions of Ukrainian production and meets DSTU, EN, ISO standards and CE, UkrSEPRO certifications.

2. Preliminary safety measures

Turn off the power and perform a lockout/tagout before starting any work.

Use insulating gloves, goggles, a protective cabinet and appropriate protection against electric shock.

Do not perform work on live elements. When using chemical solutions, use an air mask and additional protective equipment.

3. Necessary tools and materials

4. Pre-support check

Point	Verification	Acceptance/rejection criteria	Notes
1	Performing a power off	Power off confirmation	Use a multimeter to measure the voltage
2	Confirmation of execution of lockout/tagout	Sign Related Articles Guide to Diagnosing Erratic Sensor Readings: EMI/RFI Interferences, Grounding Problems, Cable Degradation and Transmitter Diagnostics This guide offers a systematic approach to diagnose and resolve issues of erratic sensor readings, with focus on EMI/RFI, grounding… Troubleshooting Irregular Hydraulic Actuator Motion: Proportional Valve Diagnosis, Contamination Detection and Signal Integrity This guide describes the diagnosis and resolution of irregular movements of hydraulic actuators. It addresses problems such as faulty valves,… Troubleshooting Compressed Air Dryer Dewpoint Excursions: Refrigerant Charge, Heat Exchanger Fouling, Drain Valve Failure, and Load Matching This guide provides a systematic approach to diagnosing and resolving dewpoint excursions in compressed air dryers. It addresses refrigerant charge,… Maintenance Guides June 30, 2026 1 min read Guide to Troubleshooting VFD Errors and Malfunctions: Overload, Over Voltage, Ground, and Communication Errors Technical analysis: Troubleshooting VFD fault codes and nuisance tripping: overcurrent, overvoltage, ground fault, and c V Vincenzo Marino Technical Editorial Team #MRO & Procurement 1. Problem description and scope This guide is for debugging VFD (Variable Frequency Drive) errors and improper shutdowns such as overload, over voltage, ground fault and communication errors. It responds to cases where the device cannot work stably, is disabled due to built-in protections, or displays illegal messages. VFD errors can occur in various types of equipment: electric motors, pumps, compressors, conveyors. The severity of the impact on production is classified as critical, as the shutdown could cause line shutdowns or equipment damage. 2. Preventive measures Protective Equipment: Insulating gloves, goggles, and electrical shock protection must be used when debugging the VFD. Protective shutdown: Perform lockout/tagout procedure before debugging. Conserving Power: Turn off the power and then remove power from the subsystem. 3. Necessary tools for diagnosis Tool Model Measuring range The goal Multimeter Fluke 434 II 0-1000 V, 0-200 mA Measurement of voltage, current, resistance Thermal camera FLIR T1020 -20°C to 1200°C Detection of overheated components Vibration analyzer BBE VIBROSCOPE 320 0-10000 Hz Detection of irregular movement Optical meter Keyence LS-600 0-200 mm Measurement of distances and clearances 4. First review Point action 1 Check VFD status and display messages 2 Write down the values of voltage, current, and temperature 3 Check the history of shutdowns and changes in settings 4 Take photos of the damage 5. Systematic diagram of diagnostics Error: Overload Check the current value with a multimeter If the current exceeds 150% of the rated current, check the connections and clearances If the current is within normal limits, check the VFD settings Error: Overvoltage Check the power at the input terminals If the voltage exceeds 450 V, check the filters and insulation If voltage is within limits, check VFD settings Error: Ground Measure the ground resistance If the resistance is less than 10 ohms, check the ground If resistance is within limits, check VFD settings Error: Communication error Check the communication cable and its connection If the cable meets the requirements, check the protocol settings If the settings are correct, check the connection to the virtual service server 6. Matrix of occurrence of defects Symptom Probable causes (by probability) Diagnostic test Expected result Overload 1. Overcurrent Current multimeter Current > 150% of nominal Overload 2. Incorrect VFD settings Checking the VFD parameters Parameters rejected Over voltage 1. Incorrect power supply Multimeter for voltage Voltage > 450 V Over voltage 2. No filter Checking the filter The filter is missing or damaged Grounding 1. Improper grounding Ground resistance multimeter Earthing resistance < 10 Ohm Grounding 2. Incorrect VFD settings Checking the VFD parameters Parameters rejected Communication error 1. Damaged cable Cable check Damaged cable Communication error 2. Incorrect protocol settings Checking settings Incorrect settings 7. Analysis of root causes 7.1. Overload An overload occurs when the current measured in the VFD exceeds the rated value. This could be due to either incorrect equipment connection or deviations in the VFD settings. If not corrected, this could damage the motor windings or cause the VFD to shut down. 7.2. Over voltage Over voltage occurs when the supply exceeds the permissible level. This can be caused by the absence of a filter, incorrect grounding or deviations in the power supply. If not corrected, arcing or damage to VFD components may occur. 7.3. Grounding A ground fault occurs when there is an improper ground or improper VFD settings. This can cause arcing or improper shutdown of the VFD. If not corrected, this could cause equipment damage or shutdown. 7.4. Communication error A communication error occurs when there is a problem with the cable or protocol settings. This can cause the VFD to lose control or shut down. If not corrected, this may cause the equipment to malfunction. 8. Step-by-step repair procedure 8.1. Overload Measure the current with a multimeter If the current exceeds 150% of the rated current, check the connection Check clearances and distances Set the VFD to the correct settings Check the current after correction 8.2. Over voltage Measure the input voltage If the voltage exceeds 450 V, check the filters Apply filters or spacers Set the VFD to the correct settings Check the voltage after correction 8.3. Grounding Measure the ground resistance If the resistance is less than 10 ohms, check the ground Establish proper grounding Set the VFD to the correct settings Check ground resistance after correction 8.4. Communication error Check the communication cable If the cable is damaged, replace it Set the correct protocol settings Check the connection with the server Test the connection after the fix 9. Preventive measures The root cause Preventive strategy Monitoring method Recommended interval Overload Checking the connection Multimeter Weekly Over voltage Installing filters Multimeter Every month Grounding Grounding check Multimeter Every month Communication error Cable check Optical meter Every month 10. Replacement parts and components Description of the component Specification When to replace UNITEC-D category Communication cable 300 V, 4 mm² When damaged Category 300 Voltage filter 450 V, 10 A When damaged Category 200 Earthing device 10 ohms With incorrect resistance Category 100 Multimeter Fluke 434 II When absent Category 500 Go to the UNITEC-D catalog to order the required components 11. Links DSTU 3023-96 - Standards for electrical devices EN 50112 - Standards for debugging electrical systems ISO 12100 - Hardware security CE – Certification for devices UkrSEPRO – Certification for Ukrainian industrial production Original manufacturer's documentation - For additional information Related Articles Guide to Diagnosing Erratic Sensor Readings: EMI/RFI Interferences, Grounding Problems, Cable Degradation and Transmitter Diagnostics This guide offers a systematic approach to diagnose and resolve issues of erratic sensor readings, with focus on EMI/RFI, grounding… Troubleshooting Irregular Hydraulic Actuator Motion: Proportional Valve Diagnosis, Contamination Detection and Signal Integrity This guide describes the diagnosis and resolution of irregular movements of hydraulic actuators. 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