1. Problem description and scope
This guide is used to diagnose and correct oscillating and uneven steering valve opening in industrial control systems. The problem can occur in various types of equipment, including pressure control systems, chemical processes and thermal power plants. The middle of the problem can be critical if fluctuations lead to loss of process control or damage to equipment.
2. Protective measures
All work must be performed using personal protective equipment (PPE):Performing work in the presence of electrical energy or high pressure requires the Lockout and Tagout (LOTO) procedure. Before removing the battery, energy storage in springs or open systems must be excluded.
- Gloves for thermal protection
- Glasses with protection against rays
- Defensive weapons
- Protective clothing
3. Necessary diagnostic tools
| Tool | Model/Spec | Measuring range | The goal |
|---|---|---|---|
| Multimeter | Fluke 87V | 0–2000 Ω, 0–600 V, 0–20 A | Measurement of electrical parameters of the positioner |
| Vibration analyzer | Brüel & Kjær 3580 | 0–20,000 Hz | Analysis of the vibration state of the valve and accumulator |
| Thermal camera | FLIR T1030sc | -20°C to 1000°C | Detection of uneven battery heating |
| Diagnostic apparatus | UNITEC-D SmartDiagnostics 4.2 | 0–100% of the positioner signal | Diagnostics of positioner signals |
4. The first inspection checklist
| Item | action |
|---|---|
| 1 | Check process parameters (pressure, temperature, flow) |
| 2 | Check changes in the system in the last 24 hours |
| 3 | Check alarm history |
| 4 | Check the condition of the positioner and the battery |
| 5 | Check for vibrations or noises |
5. Systematic diagnostics
- Symptom: Valve oscillates
- Check valve outlet pressure measurement
- If the pressure changes during opening, check the positioner
- If the pressure is stable, check the battery
- Symptom: Uneven opening
- Check positioner signal
- If the signal is unstable, adjust the positioner
- If the signal is stable, check the battery
- Symptom: High vibration
- Measure vibration on the battery
- If the vibration is higher than 4.5 mm/s, check the positioner
- If the vibration is low, check the battery
- Symptom: Uneven temperature
- Measure battery temperature
- If the temperature is higher than 50°C, check the positioner
- If the temperature is low, check the battery
6. Matrix of causes of defects
| Symptom | Probable cause | Diagnostic test | Expected result |
|---|---|---|---|
| Fluctuation of the valve | Incorrect positioner setting | Check the output signal of the positioner | The signal should be stable |
| Uneven opening | Incorrect battery size | Check battery capacity | Power should be 0.5–1.0 kW |
| High vibration | Increased battery vibration | Measure vibration | Vibration should not exceed 4.5 mm/s |
| Uneven temperature | High pressure in the system | Check the pressure in the system | The pressure should not exceed 10 bar |
7. Analysis of the main causes of defects
7.1 Incorrect setting of the positioner
The positioner is not set correctly, resulting in an uneven signal. If the positioner is not configured, it will not be able to accurately meet the process requirements. Lack of adjustment leads to valve oscillations.
7.2 Incorrect battery size
The battery does not match the power of the system, which leads to uneven opening of the valve. If the battery does not have enough power, it will not be able to open the valve fully.
7.3 Increased battery vibration
The vibration of the accumulator is higher than the set values, which causes the valve to vibrate. High vibration can occur due to poor mounting or lack of damping.
7.4 High pressure in the system
High pressure in the system causes the valve to oscillate due to uneven opening. If the pressure is higher than the set values, it can cause defects.
8. Step by step repair procedure
8.1 Incorrect setting of the positioner
- Check the output signal of the positioner
- Adjust the positioner to a stable signal
- Measure the pressure after adjustment
- Check the stability of the valve
8.2 Incorrect battery size
- Check battery capacity
- Replace the battery with a suitable one
- Check the power after replacement
- Check the stability of the valve
8.3 Increased battery vibration
- Check the vibration on the battery
- Add cushioning or bracing
- Check for vibration after installation
- Check the stability of the valve
8.4 High pressure in the system
- Check the pressure in the system
- Set the pressure within 10 bar
- Check pressure after installation
- Check the stability of the valve
9. Preventive measures
| The main reason | Preventive strategy | Monitoring method | Recommended interval |
|---|---|---|---|
| Incorrect positioner setting | Regular adjustment of the positioner | Positioner signal measurement | Monthly |
| Incorrect battery size | Using an appropriately sized battery | Power measurement | Annually |
| Increased battery vibration | Adding depreciation | Vibration measurement | Annually |
| High pressure in the system | Regular pressure measurement | Pressure measurement | Monthly |
10. Production components and spare parts
| Component description | Specification | When to replace | UNITEC-D category |
|---|---|---|---|
| Positioner | 0-100% signal, 24 VDC | After setup | Category 400 |
| Accumulator | 0.5–1.0 kW | After measuring the power | Category 400 |
| Amortization | Material: nylon, steel | After measuring the vibration | Category 400 |
| Thermal insulation | Material: thermal layer | After measuring the temperature | Category 400 |
Visit our e-catalog for parts: https://www.unitecd.com/e-catalog/
11. Links
- CE and UkrSEPRO certification
- Standards: DSTU 2006-05, EN 13445, ISO 9001
- Original documents of the manufacturer
- Additional materials from UNITEC-D
