Magnetic Drive Pump Material Selection Guide
Comprehensive material selection guide for magnetic drive pumps covering wetted parts, magnets, containment shells, bearings, and elastomers for corrosive and high-temperature applications.
API 685NACE MR0175
Material Selection Overview
Magnetic drive pumps require careful material selection for multiple components:
| Component Group | Key Materials | Selection Driver |
|---|
| Wetted parts | SS, Hastelloy, Ti, PTFE | Chemical compatibility |
| Magnets | NdFeB, SmCo | Temperature, torque |
| Containment shell | Hastelloy, Ti, PEEK | Efficiency, P/T rating |
| Bearings | SiC, Carbon, WC | Fluid, dry-run tolerance |
| Elastomers | FKM, FFKM, PTFE | Chemical, temperature |
Wetted Parts Materials
| Material | Common Name | Composition | Best For |
|---|
| 316 SS | Stainless Steel | 18Cr-10Ni-2Mo | General service, water |
| 316L SS | Low Carbon SS | Low C version | Welded constructions |
| Alloy 20 | Carpenter 20 | 20Cr-35Ni-2.5Mo-3.5Cu | Sulfuric acid |
| Hastelloy C-276 | C-276 | Ni-16Mo-16Cr-5W | Most corrosives |
| Hastelloy C-22 | C-22 | Ni-22Cr-13Mo-3W | Oxidizing acids |
| Titanium Gr 2 | CP Titanium | 99% Ti | Seawater, chlorides |
| Monel 400 | Monel | 67Ni-30Cu | HF acid |
| Duplex 2205 | Duplex SS | 22Cr-5Ni-3Mo | Chloride SCC |
| Chemical | 316 SS | Alloy 20 | Hastelloy C | Titanium | Monel |
|---|
| HCl (dilute) | Poor | Fair | Excellent | Poor | Good |
| HCl (conc.) | No | No | Good | No | Fair |
| H₂SO₄ (dilute) | Poor | Good | Excellent | Fair | Good |
| H₂SO₄ (conc.) | No | No | Good | Good | Good |
| HNO₃ | Excellent | Excellent | Poor | Excellent | No |
| HF | No | No | Fair | No | Excellent |
| NaOH | Good | Good | Excellent | Poor | Fair |
| Seawater | Poor | Good | Excellent | Excellent | Good |
| Chlorides | Poor | Fair | Excellent | Excellent | Good |
| Material | Temperature Limit | Pressure Limit | Best For |
|---|
| PTFE-lined | 150°C | 16 bar | Most acids, caustics |
| PFA-lined | 200°C | 20 bar | Higher temp corrosives |
| PVDF | 120°C | 10 bar | Moderate corrosion |
| PP (Polypropylene) | 80°C | 6 bar | Low temp acids |
| FRP | 120°C | 10 bar | Aggressive chemicals |
Magnet Materials
Neodymium Iron Boron (NdFeB)
| Grade | Max Temp | BHmax (MGOe) | Application |
|---|
| N35 | 80°C | 33-36 | Low temperature |
| N35H | 120°C | 33-36 | General industrial |
| N35SH | 150°C | 33-36 | Elevated temperature |
| N35UH | 180°C | 33-36 | High temperature |
| N35EH | 200°C | 33-36 | Maximum NdFeB |
Characteristics:
- Highest magnetic strength commercially available
- Poor corrosion resistance - requires coating
- Coating options: Nickel, Epoxy, PTFE, Gold
- Temperature coefficient: -0.45 to -0.60%/°C
Samarium Cobalt (SmCo)
| Type | Max Temp | BHmax (MGOe) | Application |
|---|
| SmCo5 | 250°C | 16-22 | Moderate high temp |
| Sm₂Co₁₇ | 300-350°C | 24-32 | High temperature |
| High-T SmCo | 450°C | 18-24 | Extreme temperature |
Characteristics:
- Superior temperature stability
- Excellent corrosion resistance
- No coating required in many applications
- Temperature coefficient: -0.20 to -0.30%/°C
- Higher cost than NdFeB
Magnet Selection Matrix
| Process Temperature | Operating Environment | Recommended |
|---|
| < 80°C | Non-corrosive | NdFeB N grade |
| 80-150°C | General | NdFeB SH/UH |
| 150-200°C | General | NdFeB EH |
| 200-350°C | Any | SmCo Sm₂Co₁₇ |
| > 350°C | Any | High-T SmCo |
| Cryogenic | Any | SmCo (better cold) |
| Corrosive fluid | Aggressive chemicals | SmCo (no coating) |
Containment Shell Materials
Selection Criteria
| Factor | Consideration |
|---|
| Chemical compatibility | Must resist process fluid |
| Pressure rating | Design pressure + surge |
| Temperature rating | Process + eddy heat + margin |
| Eddy current losses | Efficiency impact |
| Cost | Initial and lifecycle |
| Material | Eddy Loss | Max Temp | Max Pressure | Corrosion | Cost |
|---|
| 316 SS | Very High | 400°C | 100+ bar | Fair | Low |
| Hastelloy C-276 | High | 450°C | 100+ bar | Excellent | High |
| Hastelloy C-4 | High | 450°C | 100+ bar | Excellent | High |
| Titanium Gr 2 | Medium | 315°C | 80+ bar | Excellent | Medium |
| Material | Eddy Loss | Max Temp | Max Pressure | Corrosion | Cost |
|---|
| PEEK | Zero | 120°C | 16 bar | Good | Low |
| Ceramic (SiC) | Zero | 250°C | 25 bar | Excellent | Medium |
| Carbon/Graphite | Very Low | 200°C | 20 bar | Good | Low |
| FRP | Zero | 100°C | 10 bar | Good | Low |
Shell Selection Guide
| Application | Recommended Shell |
|---|
| General chemicals | Hastelloy C-276 |
| High efficiency needed | Ceramic or PEEK |
| Seawater | Titanium |
| Very high pressure | Hastelloy |
| Budget constraint | 316 SS or PEEK |
| Cryogenic | Hastelloy C-276 |
Bearing Materials
Product-Lubricated Bearings
Magnetic drive pumps use product-lubricated (process fluid) bearings, making material selection critical.
| Material | pH Range | Dry-Run | Hardness | Best For |
|---|
| SiC (Silicon Carbide) | 0-14 | Poor | Very High | Most applications |
| Carbon/Graphite | 3-12 | Good | Medium | Clean fluids |
| Tungsten Carbide | 3-10 | Poor | Very High | Caustics |
| PEEK | 2-12 | Fair | Low | Light duty |
| Al₂O₃ (Alumina) | 2-12 | Poor | High | Abrasive service |
Bearing Pairing Options
| Configuration | Application | Notes |
|---|
| SiC vs SiC | General service | Best wear resistance |
| SiC vs Carbon | Dry-run possible | Better dry-run |
| Carbon vs Carbon | Clean fluids | Self-lubricating |
| WC vs WC | Caustic service | High hardness |
Bearing Selection by Fluid
| Fluid Type | Recommended Bearing | Alternative |
|---|
| Water (clean) | SiC/SiC | Carbon/Carbon |
| Hydrocarbons | SiC/SiC | SiC/Carbon |
| Acids (most) | SiC/SiC | - |
| Strong Caustic | WC/WC | SiC/SiC |
| HF Acid | SiC/SiC | - |
| Solvents | SiC/SiC | Carbon |
| LPG/LNG | SiC/SiC | - |
Bearing Life Factors
| Factor | Impact on Life |
|---|
| Fluid cleanliness | Critical - particles cause wear |
| Flow rate | Higher flow = better lubrication |
| Temperature | High temp reduces clearances |
| Startup frequency | Each start causes wear |
| Dry-run events | Catastrophic without protection |
Elastomer Materials
O-Ring and Gasket Materials
| Material | Temp Range | Chemical Resistance | Notes |
|---|
| FKM (Viton) | -20 to 200°C | Good - most chemicals | Standard choice |
| FFKM (Kalrez) | -20 to 300°C | Excellent - nearly universal | Premium cost |
| EPDM | -40 to 150°C | Water, caustics | Not for hydrocarbons |
| NBR (Buna-N) | -30 to 100°C | Oils, fuels | Not for oxidizers |
| PTFE | -200 to 250°C | Nearly universal | Requires compression |
| Graphite | -200 to 500°C | Most chemicals | High temp gaskets |
Elastomer Selection Guide
| Application | Recommended | Alternative |
|---|
| General chemicals | FKM | FFKM |
| High temperature | FFKM | PTFE |
| Cryogenic | PTFE | FFKM |
| Water/Steam | EPDM | FKM |
| Hydrocarbons | FKM | NBR |
| Strong acids | FFKM | PTFE |
| Strong caustics | EPDM | FFKM |
Special Service Materials
Sour Service (H₂S) - NACE MR0175
| Component | Requirement |
|---|
| Casing | Max 22 HRC hardness |
| Impeller | Soft grade SS |
| Bolting | ASTM A193 B7M |
| Weld overlays | Tested per NACE |
Cryogenic Service
| Component | Recommended Material |
|---|
| Casing | 316/316L SS, CF8M |
| Containment shell | Hastelloy C-276 |
| Magnets | SmCo |
| Bearings | SiC/SiC |
| O-rings | PTFE |
High Purity / Pharma
| Requirement | Material Solution |
|---|
| FDA compliance | 316L SS electropolished |
| Surface finish | Ra < 0.8 μm |
| Elastomers | PTFE or FFKM |
| No particle generation | SiC bearings |
=== MATERIAL SPECIFICATION ===
Wetted Parts:
- Casing: _________ (Grade: ___)
- Impeller: _________ (Grade: ___)
- Wear rings: _________
- Shaft/Sleeve: _________
Magnetic Coupling:
- Magnet type: NdFeB ___ / SmCo ___
- Magnet coating: _________
- Max allowable temp: ___°C
Containment Shell:
- Material: _________
- Type: Metallic / Non-metallic
- Thickness: ___ mm
Bearings:
- Material: _________ vs _________
- Configuration: _________
Elastomers:
- O-rings: _________
- Gaskets: _________
- Temperature rating: ___°C
Special Requirements:
- NACE MR0175: □ Required
- FDA compliant: □ Required
- Cryogenic: □ Required
- Other: _________
Material Verification Checklist
□ Wetted Parts
□ Corrosion data verified for process fluid
□ Temperature rating adequate
□ Pressure rating adequate
□ Material certificates required
□ Magnets
□ Temperature grade appropriate (process + eddy + margin)
□ Coating compatible with fluid
□ Torque capacity adequate
□ Containment Shell
□ Chemical compatibility verified
□ Pressure/temperature rating adequate
□ Eddy losses calculated (if metallic)
□ API 685 compliance confirmed
□ Bearings
□ pH range compatible with fluid
□ Dry-run protection if carbon not used
□ L10 life ≥ 25,000 hours
□ Elastomers
□ Temperature range adequate
□ Chemical compatibility verified
□ FDA compliance (if required)
Common Material Mistakes
| Mistake | Consequence | Prevention |
|---|
| 316 SS in chlorides | Pitting, SCC | Use Hastelloy or Titanium |
| Carbon bearings in acids | Rapid wear | Use SiC |
| NdFeB magnets too hot | Demagnetization | Calculate total temp |
| FKM in steam | Rapid degradation | Use EPDM or FFKM |
| PTFE shell at high pressure | Failure | Use metallic shell |
| No magnet coating | Corrosion attack | Specify coating |
Material Cost Comparison
| Component | Economy | Standard | Premium |
|---|
| Casing | 316 SS | Hastelloy | Titanium |
| Shell | 316 SS | Hastelloy | Ceramic |
| Magnets | NdFeB std | NdFeB high-T | SmCo |
| Bearings | Carbon | SiC | Diamond-like carbon |
| Elastomers | NBR/EPDM | FKM | FFKM |
Note: Always select based on technical requirements first, then optimize cost.