Key Points
- M106K (antimony-impregnated): high temperature 400°C+, high load, for hot oil pumps and high-temperature media, mainstream high-temperature grade
- M254K (furan resin-impregnated): acid/alkali corrosion resistance, for chemical pumps and reactors, mainstream corrosion-resistant grade
- M179K (epoxy resin-impregnated): general-purpose, high mechanical strength, for clean water and cooling water pumps
- Four-step selection: ① confirm media type and corrosivity → ② confirm temperature range → ③ confirm pressure and PV value → ④ confirm speed and face pairing
- Special service selection: food-grade → PTFE-impregnated; abrasive particulate media → hard carbon grades; nuclear primary pump → special high-purity grades
1. Why Graphite Grade Selection Matters
The carbon graphite grade directly determines seal performance, life and reliability. Sealing rings of identical dimensions using different carbon graphite grades may have 3-5x difference in service life. Incorrect grade selection is among the most common causes of premature seal failure.
Mainstream domestic carbon graphite grades follow the JB/T 8896 standard. The grade letters and numbers represent:
- M: carbon graphite material class
- Number 1: material series number (matrix formulation)
- K: impregnation type (K=antimony, F=phenolic resin, H=epoxy resin, N=furan resin, etc.)
2. Mainstream Grade Comparison
2.1 M106K (Antimony-Impregnated Carbon Graphite)
- Matrix: high-strength carbon graphite matrix, antimony-impregnated
- Density: 2.20-2.30 g/cm³
- Shore hardness: HS 75-90
- Compressive strength: 260-340 MPa
- Porosity: <2%
- Service temperature: 400-500°C (non-oxidizing media)
- Features: high-temperature and high-load resistance; antimony provides excellent thermal conductivity and load capacity
- Typical applications: hot oil pump seals, high-temperature thermal oil media, petrochemical high-temperature pumps, steam media
2.2 M254K (Furan Resin-Impregnated Carbon Graphite)
- Matrix: medium-strength carbon graphite matrix, furan resin-impregnated
- Density: 1.80-1.90 g/cm³
- Shore hardness: HS 55-75
- Compressive strength: 180-240 MPa
- Porosity: <2%
- Service temperature: 200-250°C
- Features: excellent acid/alkali corrosion resistance; furan resin is stable against strong acids and alkalis
- Typical applications: chemical pump seals, acid/alkali media, reactor agitators, electroplating equipment
2.3 M179K (Epoxy Resin-Impregnated Carbon Graphite)
- Matrix: general carbon graphite matrix, epoxy resin-impregnated
- Density: 1.75-1.85 g/cm³
- Shore hardness: HS 50-70
- Compressive strength: 170-220 MPa
- Porosity: <2%
- Service temperature: 180-220°C
- Features: balanced mechanical strength, moderate corrosion resistance, cost-effective
- Typical applications: clean water pumps, cooling water pumps, circulation pumps, general industrial pumps
2.4 Other Common Grades
- M106H (epoxy-impregnated): general purpose, ambient clean water
- M254N (furan-impregnated): strongly corrosive service, similar to M254K
- M120K (antimony-impregnated): high-strength matrix, heavy-duty bearing applications
- PTFE-impregnated grades: food/pharmaceutical sanitary grade, best chemical inertness
- Copper-impregnated grades: electrical applications, excellent electrical/thermal conductivity
3. Four-Step Selection Method
Step 1: Confirm Media Type and Corrosivity
| Media type | Recommended impregnation | Recommended grade |
|------------|--------------------------|-------------------|
| Clean water, cooling water | Epoxy resin | M179K |
| Weak acid/alkali | Phenolic or furan resin | M254K |
| Strong acid/alkali | Furan resin | M254K (N impregnation) |
| High-temperature oils | Antimony metal | M106K |
| Food/pharmaceutical media | PTFE | Food-grade |
| Particulate media | Antimony or un-impregnated hard carbon | M106K or hard carbon |
Step 2: Confirm Temperature Range
- <180°C: resin-impregnated grades available (M179K/M254K), cost-effective
- 180-400°C: must use metal-impregnated grades (M106K); resin impregnation carbonizes and fails
- >400°C: special high-temperature grades needed; consult supplier for customization
Step 3: Confirm Pressure and PV Value
- Media pressure <1.5 MPa: unbalanced seal acceptable, all grades suitable
- Media pressure 1.5-5 MPa: balanced seal needed, select high-strength grades (M106K/M254K)
- PV verification: PV = face pressure × face linear velocity, must not exceed material's allowable PV
- Carbon graphite vs SiC: allowable PV 7-15 MPa·m/s
- Carbon graphite vs hard alloy: allowable PV 5-10 MPa·m/s
Step 4: Confirm Speed and Face Pairing
- Speed <3000 rpm: standard carbon graphite + reaction-bonded SiC pairing
- Speed 3000-10000 rpm: select high-strength matrix grade (M106K), reduce face pressure
- Hard face pairing: SiC > hard alloy > alumina, selected by media corrosivity and cost
4. Special Service Selection Recommendations
4.1 Food and Pharmaceutical Sanitary Grade
- Media: drinking water, dairy, pharmaceutical solutions, alcohol
- Recommendation: PTFE-impregnated carbon graphite, FDA-compliant
- Note: avoid metal-impregnated grades to prevent metal ion migration
4.2 High-Wear Particulate Media
- Media: sewage, slurry, pulp
- Recommendation: consider hard carbon grades or SiC vs SiC pairing
- Note: carbon graphite soft face wears rapidly; select high-hardness grades or switch to hard-vs-hard pairing
4.3 Nuclear Primary Pump Seal
- Media: primary loop high-temperature high-pressure water
- Recommendation: special high-purity carbon graphite grade, nuclear-standard compliant
- Note: requires long-term irradiation stability and low impurity release; selection must follow nuclear specifications
4.4 Vacuum Pump Dry Gas Seal
- Media: gas (no fluid film lubrication)
- Recommendation: antimony-impregnated high-strength grade (M106K) + dry gas seal structure
- Note: dry friction service requires leveraging carbon graphite self-lubrication; metal impregnation enhances load capacity
5. Technical Verification Points for Procurement
When ordering, recommend confirming:
1.Grade compliance with domestic/international standards (JB/T 8896, API 682)
2.Impregnation type and post-impregnation porosity (should be <2%)
3.Mechanical property report: hardness, compressive strength, flexural strength
4.Whether material property test reports and certificates are provided
5.Batch stability: performance variation between batches from the same supplier should be <10%
6.Whether custom machining from drawings and samples is supported
Huahao Sealing Co., Ltd. supplies mainstream grades M106K, M254K, M179K and special impregnation customization, with custom machining of carbon graphite seal rings, bushings and segmented rings from drawings or samples, and complete material property test reports.