Hot Oil Pump Antimony-Impregnated Carbon Graphite Seal Retrofit — from Frequent Phenolic Failures to Long-Runout Service at 350°C

1. Service Conditions and Failure Modes

350°C vacuum residue carries high viscosity (~78 mm²/s at 100°C), high carbon residue and catalyst fines. The face film flashes easily; solids drive abrasive wear; once past the resin limit the impregnant carbonizes and radial face cracks follow. Phenolic rings typically last 2-3 months in this service.

2. Material Solution: Antimony-Impregnated M106D

M106D antimony-impregnated carbon graphite (third-party tested: 2.20 g/cm³ density, 190 MPa compressive strength, 92 HS, 2% porosity):

• Rated 450-500°C, covering 350°C residue service with margin
• Metallic network conducts heat away quickly, reducing thermal cracking
• 92 HS hardness resists abrasive wear far better than resin grades

Pair with WC (solids-laden) or SSiC faces; springs in Inconel/Hastelloy class alloys.

3. Retrofit Essentials

• Flush and cooling: verify the API 682 plan keeps seal chamber temperature below the allowable face temperature
• Solids: add a hydrocyclone separator where catalyst fines are present
• Installation: set face pressure and compression per drawing; avoid off-center loading

4. The Economics

• Replacements: phenolic ~4/year → antimony ≤1/year
• Cost per event: seal + labor + thermal-oil make-up loss
• Downtime: one unplanned outage often costs tens of thousands of RMB — dozens of times the seal price
• Conclusion: a few hundred RMB more per ring, usually paid back within the first year

5. Verification

After the retrofit, inspect face wear and geometric tolerances quarterly and track leak rate and running hours to confirm the improvement in life and cost.