Maintenance & Reliability · SOP

Post Catalyzed Varnish Pot Life Test

Determines the usable working time (pot life) of two-component catalyzed varnish after mixing. Ensures full cure properties and prevents application defects from premature gelation or over‑aging.

Estimated Time

45 min

Difficulty

Advanced

Regulation

IEC 60034

Version

1.0

Free download — no sign‑up, no email.Take this SOP to your shop floor and make it yours.

↓ PDF (print‑ready) ↓ Word (editable)

Purpose

To verify the usable working time (pot life) of catalyzed varnish after mixing the resin and hardener. This test ensures that the varnish is applied within its optimal viscosity window to achieve proper impregnation, curing, and dielectric strength in electrical windings. Early gelation or over‑extended working time leads to coating defects and equipment failures.

Scope

This procedure applies to all two‑component varnish systems (resin + hardener) used for vacuum pressure impregnation (VPI) of motor stators, transformer coils, and other electrical equipment in our facility. It covers all batches where pot life has not been previously validated for the current ambient temperature and humidity conditions.

Safety Precautions

CHEMWear chemical‑resistant gloves (nitrile), safety goggles, and a chemical‑resistant apron. Varnish contains isocyanates and solvents — avoid skin contact.
VENTPerform work in a well‑ventilated area with local exhaust ventilation (LEV) or a fume hood. Breathing vapours can cause respiratory irritation.
PPENo open flames or ignition sources. Varnish solvents are flammable. Keep away from sparks and hot surfaces.
SPILHave spill containment materials (absorbent pads, chemical waste container) ready. Spills must be cleaned immediately per hazardous waste protocol.

Required Tools & Materials

Catalyzed varnish (resin + hardener) from approved batch
Manufacturer’s mixing ratio chart
Transparent graduated container, 1 L capacity
500 mL sample cup (disposable)
Wooden stir stick (clean, dry)
Timer / stopwatch (resolution 1 s)
Thermometer, 0–50 °C (±0.5 °C)
Ford #4 viscosity cup (or equivalent)
Digital scale (0.1 g precision)
Data recording sheet / tablet

Stop Chasing Maintenance Blindly

Track every calibration, pressure drop reading, and machine performance trend in one place. ServiceGrid logs your tasks automatically and alerts you before failure.

Try ServiceGrid →

Procedure: Step-by-Step

1 Prepare workspace — Ensure the area is clean, dry, and at ambient temperature 20–25 °C. Record the exact ambient temperature and relative humidity on the data sheet.

2 Verify components — Check resin and hardener drums for correct product, lot numbers, and expiration dates. Do not use if expired or if off‑odour/clumping is observed.

3 Weigh components — Using the digital scale, measure the resin and hardener per the manufacturer’s ratio (e.g., 4:1 by weight). Pour into the 1 L graduated container. Tare between components.

4 Mix thoroughly — Start the timer immediately after combining. Stir with a wooden stick for 2 full minutes, scraping sides and bottom until uniform. Avoid introducing air bubbles.

5 Initial viscosity reading (T=0) — Dip the Ford #4 cup into the mixed varnish, fill to brim, and lift. Measure the time (seconds) for a continuous stream to break. Record as initial viscosity.

6 Repeated measurement — Repeat the viscosity test every 10 minutes. Stir gently with the stick before each test. Record each reading and any visual changes (haze, stringiness).

7 Identify pot life end — The pot life expires when the viscosity reaches twice the initial value, or when gelation is observed (thread formation on the stir stick). Record the elapsed time.

8 Document results — Fill out the data sheet with: ambient T/RH, component lot numbers, initial viscosity, final viscosity, pot life time, and any anomalies. Attach a photo if needed.

9 Dispose of waste — Transfer all leftover varnish and used tools into a labeled hazardous waste container. Clean work surfaces with approved solvent. Remove gloves and wash hands.

Post Catalyzed Varnish Pot Life Test

Stop Chasing Maintenance Blindly

Software that works like your best tools.