As high-temperature technologies continue to advance—including concentrated solar power (CSP), thermal energy storage, metal heat treatment, and high-temperature chemical processing—the demand for stable and reliable molten salt pumps has grown rapidly. These pumps operate under extreme temperatures (300°C–600°C or more) where standard thermal oil pumps cannot survive.

Choosing the right molten salt pump is critical for system reliability, safety, and operational efficiency. As a professional high-temperature pump manufacturer, SDP Pump provides a clear and practical guide to help industrial buyers select the most suitable molten salt pump for their engineering needs.

1. Understand Your Molten Salt Medium

Molten salts vary in melting point, corrosion behavior, and viscosity. The pump you choose must match the fluid’s characteristics.

1.1 Common Molten Salt Types

• Nitrate salt (solar salt, NaNO₃–KNO₃)
  • Melting point: 220–260°C
  • Operating range: 300–565°C
  • Widely used in CSP and TES systems
• Carbonate salt
  • Melting point: ~400°C
  • Operating range: 450–700°C
• Chloride salt (MgCl₂ / NaCl / KCl blends)
  • Melting point: 430–500°C
  • High corrosiveness
  • Used in next-generation thermal storage

Why it matters

Different salts require different materials, heating methods, and pump structures.

✔ Higher melting point → requires stronger heating & insulation
✔ Higher corrosiveness → requires higher-grade alloys
✔ Higher viscosity → affects pump sizing and NPSH

Before selecting a pump, confirm:

• Salt melting point
• Maximum operating temperature
• Corrosion behavior
• Crystallization tendency

2. Select the Correct Pump Type (Vertical vs Horizontal)

Unlike standard chemical pumps, molten salt pumps have unique structures.

2.1 Vertical Molten Salt Pumps (Most Common)

• Long vertical shaft
• Motor stays far from high-temperature zone
• Bearings remain protected
• Suitable for tanks, reactors, and salt circulation systems

2.2 Horizontal Molten Salt Pumps

• Used in confined spaces
• Requires enhanced cooling systems
• Typically used for lower temperature molten salt (<450°C)

Recommendation

✔ Choose vertical molten salt pumps for temperatures above 450°C
✔ Choose horizontal only when installation conditions require it

SDP Pump specializes in vertical molten salt pumps with long service life under extreme temperatures.

3. Pump Material Selection (Critical Factor)

Material selection determines service life and corrosion resistance.
Standard stainless steel is not enough for molten salt.

Common Materials for Molten Salt Pumps

• 316H / 304H stainless steel – economical option for nitrate salts
• Incoloy 800H / 825 – excellent high-temperature strength & corrosion resistance
• High-Ni alloys – essential for chloride salt applications
• Ceramic sleeves & bearings – prevent wear at extreme heat

Key Considerations

✔ Corrosion resistance
✔ High-temperature creep strength
✔ Thermal shock resistance
✔ Low oxidation rate

SDP Pump recommends Incoloy alloys for continuous operation above 500°C.

4. Choose the Correct Shaft & Bearing Design

Molten salt pumps operate with long vertical shafts that must remain cool and stable.

4.1 Extended Shaft Design

• Keeps bearings away from molten zone
• Reduces thermal expansion damage
• Extends pump lifespan

4.2 Bearing Configuration

• Upper bearings: Grease or oil lubricated
• Intermediate bearings: Often air-cooled
• Lower bearings: Dry-running or ceramic bearings (no water/oil allowed)

4.3 Cooling Methods

• Natural cooling
• Air cooling
• Forced cooling fans
• Cooling jackets (for >550°C)

✔ Choose a shaft and cooling configuration based on your maximum operating temperature.

5. Heating & Insulation Requirements

Unlike thermal oil pumps, molten salt pumps MUST stay above the salt melting point.

Key Heating Components

• Pump casing heat tracing
• Outlet piping heat tracing
• Shaft sleeve insulation
• Salt tank heating system

If any part cools below the melting point, solidification occurs, leading to:
✘ Blocked pump
✘ Shaft overload
✘ Seal and bearing damage

Recommendation
✔ Full-system insulation and heat tracing is mandatory for molten salt operations.

6. Hydraulic Selection: Flow, Head & NPSH

Accurate hydraulic selection ensures stable circulation.

6.1 Flow Rate

Salt systems typically require:

• Large circulation flow
• Continuous 24/7 operation

Choose a pump whose BEP (Best Efficiency Point) is close to your operating point.

6.2 Head

Account for:

• System height
• Pipeline resistance
• Salt viscosity at working temperature

6.3 NPSH Requirement

Molten salt has low vapor pressure → cavitation risk is low.
But keep adequate NPSHa for safety margins.

7. Seal Type: Mechanical Seal vs Sealless

Mechanical Seal Pumps

• High-temp graphite seals
• External cooling required
• Risk of salt infiltration if improper heating occurs

Sealless Magnetic Drive Pumps

• Zero leakage
• Suitable for toxic or corrosive salts
• More expensive but safer
• Used in CSP and molten salt reactors

SDP Pump offers both sealed and sealless molten salt pump designs.

8. Supplier Expertise Matters

Molten salt pumps are not commodity products.
Their performance depends heavily on engineering details.

Choose a manufacturer who offers:

• High-temperature alloy casting capability
• Experience with nitrate/carbonate/chloride salts
• Full heat transfer system design support
• Custom vertical shaft engineering
• Real project references in CSP or TES

SDP Pump has more than 20 years of experience in chemical high-temperature pumps, supplying molten salt pumps to chemical plants, energy storage projects, and solar power stations.

Conclusion

Choosing a molten salt pump requires far more than selecting a pump size or flow rate. You must evaluate temperature levels, salt properties, materials, cooling methods, hydraulic performance, and system layout.
For temperatures above 350–400°C, a properly engineered molten salt pump is essential for safe, stable, and long-lasting operation.

With its expertise in high-temperature and chemical-resistant pump solutions, SDP Pump provides reliable molten salt pumps built for continuous operation in the harshest environments.