Guidelines and Best Practices for Spark Testing Glass-Lined Equipment

Why Spark Testing Matters

Regular inspection of glass-lined equipment is essential for maintaining process integrity, preventing contamination, and ensuring operational safety. One of the most reliable methods for identifying damage that might be missed during visual inspections—such as small chips, cracks, pinholes, and other defects—is spark testing.  

This procedure helps detect potential failures before they escalate, saving both time and costly repairs. In this updated guide, we’ll walk through:
✔ The fundamentals of spark testing
✔ General safety guidelines
✔ Proper preparation procedures
✔ Best practices for operating AC and DC spark testers

Whether you're conducting routine preventive maintenance or inspecting your equipment after an incident, following these steps will help ensure an accurate and safe evaluation of your glass-lined surfaces.

Understanding Spark Testing: DC vs. AC Spark Testers

There are two types of spark testers used for inspecting glass-lined equipment:

• DC Spark Testers (Preferred for vessels and grounded equipment)
  • Portable and safer for field use
  • Ideal for large, stationary equipment that can be electrically grounded
  • Detects defects with a visible spark, red light alarm, and audible signal
• AC Spark Testers (Used for removable components like agitator blades)
  • Required for equipment that is fully glassed and cannot be grounded
  • Generates a bright white spark when passed over a defect
  • Must be used with extra caution due to higher voltage output

⚠ Note: Since spark testing is considered a destructive test, it should only be performed:
✅ If there is a suspected defect (visual clues or after an incident)
✅ As part of an annual preventative maintenance program

General Safety Guidelines for Spark Testing

When performed correctly, spark testing is a safe and effective method for identifying damage. However, failing to follow safety precautions can lead to electrical hazards, glass damage, or even explosive risks.

Key Safety Considerations

• Never perform spark testing in a combustible atmosphere 🔥
  • Spark testers generate up to 6,000 volts, which can ignite flammable gases.
• Only conduct spark testing on a clean, dry surface
  • Moisture or chemical residues can cause false readings.
• Ensure only trained personnel operate the spark tester
  • Always consult plant safety personnel before conducting the test.
• Avoid contact with the probe’s spark discharge
  • While non-lethal, it can cause an involuntary reaction that may result in injury.

Additional Safety Precautions

✅ Wear non-conductive, protective footwear when inside the vessel
✅ Remove metal objects (e.g., belt buckles, tape measures) to prevent scratches
✅ Hold the test probe only by the insulated handle
✅ Keep the probe away from personnel and any metal surfaces that could conduct electricity
✅ Inspect the electrode brush for broken or bent wires before use

Preparing Your Vessel for Spark Testing

Before testing, proper preparation is critical for accurate results and operator safety.

Step 1: Disconnect Sensitive Probes & Instruments

• High-voltage spark testing may damage electronic probes inside the vessel.
• Always disconnect or remove sensitive instrumentation before testing.

Step 2: Thoroughly Clean and Dry All Glass Surfaces

• Any residual humidity or contamination can give false readings.
• Ensure all areas, especially nozzles and internal attachments, are clean and dry.

Step 3: Properly Ground the Equipment

• For DC spark testers, grounding is critical for accurate readings.
• For AC spark testers, grounding is recommended for additional safety.
• How to ground properly:
  • If the equipment's electrical ground is inadequate, connect it to a water pipe or drive a solid grounding rod into the earth.

Step 4: Verify the Spark Tester is Functioning Properly

• Before testing, touch the probe to the metal substrate of the equipment to confirm:
  ✔ The alarm circuits activate
  ✔ The brush/electrode generates a visible spark

How to Operate a Spark Tester

The following steps outline proper spark testing procedures:

Step 1: Power Up the Tester

• Ensure the probe is held away from personnel and conductive surfaces.
• Turn the power switch ON and confirm the:
  ✅ Indicator light illuminates
  ✅ Unit emits a buzzing sound

Step 2: Begin Testing the Glass-Lined Surface

• Gently move the electrode brush across the glass at a consistent speed.
• Maintain the correct angle:
  • Laying the brush completely flat may reduce the voltage below detection levels.

Step 3: Identifying Defects

• DC Spark Tester Indicators:
  ✔ Visible spark at defect location
  ✔ Red light alarm & audible signal
  ✔ Drop in output voltage
• AC Spark Tester Indicators:
  ✔ Bright white spark when moved across a defective lining
  ✔ Warning: Surface moisture or impurities may also cause a slight discharge

❗ Important: If a suspected defect is found, clean and retest the area to confirm before marking it for repair.

Step 4: Properly Discharging the Vessel After Testing

• Wipe the glass surface with the probe to neutralize residual voltage.
• Reconnect any instrument probes that were previously disconnected.
• If no repairs are needed, the vessel can be returned to service.

Maintaining Your Spark Tester for Reliable Performance

Regular maintenance ensures consistent accuracy and operator safety.

Battery Maintenance (DC Spark Testers)

🔋 Best Practices:
✅ Recharge after every use to prevent battery drain.
✅ Charge at least once every 3 months to prevent long-term storage damage.

Probe & Electrode Brush Maintenance

• Use an ohmmeter to check resistance between the probe handle plug and installed brush.
• If resistance is detected, replace the high-voltage lead to avoid performance issues.

Final Thoughts: The Role of Spark Testing in Preventative Maintenance

Routine inspections of glass-lined equipment are essential for maintaining reliability, product quality, and plant safety.

Key Takeaways

✅ Spark testing detects early signs of damage, preventing costly failures.
✅ Safety precautions are critical—never test in combustible atmospheres.
✅ Proper preparation ensures accurate results, including cleaning and grounding.
✅ Routine maintenance of your spark tester prolongs its lifespan and ensures reliable operation.

Need Assistance with Spark Testing?

De Dietrich Process Systems offers onsite field service technicians across North America for professional inspections and repairs.

📞 For expert support, contact us at 908-317-2585
📩 Contact us online or by phone to request instructional engineering bulletins:

• Bulletin 185 (AC Models)
• Bulletin 883 (DC Models)

Download our free Glass-Lined Equipment Inspection eGuide or speak with a technical sales representative today!