Jiangsu Haifa Machinery Manufacturing Co., Ltd.

Produced by: Jiangsu Haifa Machinery Manufacturing Co., Ltd. (API610 Industrial Pump Professional R&D Manufacturer)

I. Background of Qinghai Solar Thermal Dual-Tank Molten Salt Heat Storage System  
The tower-type solar thermal dual-tank molten salt heat storage system is the mainstream technical route for long-duration energy storage at present. The entire system relies on cold and hot salt tanks to complete the solar heat storage and release power generation cycle. The molten salt circulation pump, as the core medium transport equipment, is known as the "power" of the solar thermal power station's energy storage system. The complete cycle process: Normal temperature binary nitrate molten salt is stored in the cold salt tank (medium temperature 290~300°C), then pressurized and transported via a VS vertical long-shaft molten salt pump to tower-top heat absorber; the molten salt gathers solar radiation heat, rises to 565°C, and flows into the hot salt tank to complete heat storage; during the night without sunlight, high-temperature molten salt passes through a steam generator heat exchange to produce steam, driving a steam turbine generator set for power generation. The cooled low-temperature molten salt flows back to the cold salt tank, completing the entire closed cycle.

The Qinghai solar thermal power station features high altitude, significant day-night temperature differences, and long, cold winters. The entire molten salt system faces multiple severe challenges: Large medium temperature span: alternating operation between 290°C low-temperature and 565°C ultra-high-temperature ranges, with significant differences in thermal expansion of shafting and pump body; the freezing point of nitrate molten salt is about 220°C, and shutdown cooling easily leads to medium crystallization, pipeline and pump cavity freezing and blockage; low atmospheric pressure at high altitude, poor equipment heat dissipation environment, long cantilever shaft structure prone to excessive vibration; equipment requires 8,000 hours of continuous operation annually, with start-stop cycles ≥30,000 times, stringent reliability requirements per national group standards... on these operating condition differences, Jiangsu Haifa has conducted differentiated hydraulic structure, material selection, thermal compensation, and heat tracing anti-crystallization designs for cold salt tank pumps and 565°C hot salt tank pumps, fully complying with API 610 and ISO 13709 international industrial pump design standards.

II. Key Design Points for Cold Salt Tank VS Molten Salt Pump  
The cold salt tank pump undertakes three functions: heat absorber feed transport, system overall circulation, and device start-stop salt filling. The impeller is fully submerged below the molten salt liquid level, naturally providing excellent anti-cavitation performance effectively avoiding suction and air binding faults under low liquid level conditions. Core design optimization directions:  

1. Low NPSHa hydraulic adaptation design: Uses widened flow channel impeller + front inducer structure, significantly reducing required net positive suction head (NPSHr), adapting to tank liquid level fluctuations and insufficient effective NPSHa at high altitude;




2. Full-range control of long shaft: Multi-point sliding guide bearing arrangement on shafting, rotor assembly undergoes G2.5 level high-precision dynamic balance calculation to avoid long shaft deflection vibration; first critical speed and rated operating speed reserve ≥20% separation margin to eliminate resonance;




3. Full heat tracing + drain anti-crystallization system: No medium retention dead corners in pump submerged parts and outlet pipelines, outer wall equipped with electric heat tracing + aluminum silicate insulation layer, continuous insulation during shutdown, cavity bottom set with salt drain port to completely drain residual molten salt, preventing low-temperature crystallization blockage;- Variable frequency flexible regulation system: Equipped with variable frequency drive, can adjust flow in real-time based on power station load, adapting to circulation changes from daytime solar radiation fluctuations, balancing operational efficiency and condition stability.

III. Core Technical Solution for 565°C High-Temperature Hot Salt Tank VS Molten Salt Pump  
565°C high-temperature nitrate molten salt has characteristics such as strong high-temperature oxidation, large thermal expansion, and high-temperature creep risk, making it unsuitable for direct application of standard VS6 vertical pump structures for normal temperature. Leveraging years of high-temperature special pump R&D experience, Jiangsu Haifa has customized and upgraded the entire machine structure for high conditions:  

1. Cold-hot zone isolation layout: Drive motor and main thrust bearing are arranged in the low-temperature heat dissipation area at the tank top, with an extended heat-insulating shield tube to block 565°C high-temperature upward conduction; bearing box equipped with air cooling + water cooling dual dissipation structure to ensure constant temperature operation of lubricating grease;




2. Precise compensation design for shaft thermal expansion: Pump shaft, protective tube, and guide shell all pre-reserve operating gaps based on 565°C condition thermal expansion, with bellows thermal compensation components to eliminate gap deformation and jamming from temperature changes;




3. Graded selection of high-temperature and corrosion-resistant materials: on nitrate molten salt corrosion test data select materials by grade: normal conditions use high-temperature resistant austenitic stainless steel; highrosion long-cycle operation scenarios upgrade to nickel-based alloy materials to resist high-temperature molten salt intergranular corrosion and erosion wear;




4. Multi-stage guide bearing structure: Multi-layer medium self-lubric guide bearings set in the submerged section to support stable long shaft operation, suppressing shaft deflection vibration under high-temperature conditions.

IV. Jiangsu Haifa API 610 VS High-Temperature Molten Salt Pump Standard Technical Parameter Table  
| Technical Item | General Parameter Range | Condition Description |
|---|---|---|
| Pump Structure Type | API 610 VS vertical long-shaft submerged pump (VS1 structure) | Dedicated structure for solar thermal storage dual-tank heat storage |
| Application Scenario | Cold salt tank circulation pump 565°C hot salt tank discharge pump | Tower/trough solar thermal power station molten salt system |
| Medium Applicable Temperature | 280°C ~ max 600°C | Rated operating range 290565°C |
| Design Maximum Temperature Resistance | 600°C Reserved safety temperature margin |
| Flow Coverage Range | 2 ~ 15,000 m³/h Can meet customization needs for large, medium, and small solar power stations |
| Single-stage/Multi-stage Head Range | Up to 1,000 m | Adapts to different tank heights and pipeline resistance conditions |
|eller Structure | Single-stage guide vane type / Multi-stage series guide vane type | Large flow low head uses single-stage, high head long pipeline uses multi-stage |
| Bearing Configuration | External heavy-duty thrust bearing + submerged multi-point guide bearings | Bear molten salt axial thrust,-term stable support |
| Online Monitoring Points | Vibration intensity, shaft displacement, bearing temperature, tank liquid level, inlet and outlet pressure | Connected to power station DCS system real-time data collection |
| Design Execution Standards | API 610 (ISO 13709), Solar thermal storage power station technical specifications | Meets domestic + overseas project bidding standards |

Note: The above table shows the enterprise standard master pump parameter range. For 565°C high-temperature molten salt conditions, non-standard fine design must be carried out based on actual project flow, head, tank depth, molten salt composition, and NPSHa values.

V. Factory Quantitative R&D Verification Indicators (Ensuring Long-Term Stable Operation at High Altitude)  
To adapt to Qinghai's harsh natural environment and high-temperature molten salt conditions, each VS high-temperature molten salt pump undergoes a full set of high-temperature simulation tests before leaving the factory, with quantitative acceptance indicators as follows:  

1. Full-range thermal field simulation analysis: Numerical simulation verification of 0~600°C full temperature field and shaft thermal expansion;




2. CFD hydraulic flow field optimization: Eliminate flow channel vortices and pressure pulsations, reduce hydraulically induced vibration;




3. Hot continuous full-load operation test: Cumulative operation time not less than 168 hours;




4. Cold-hot alternating cycle test: High and low temperature alternating start-stop cycles ≥20 times, verifying thermal expansion adaptability;




5. Vibration acceptance standard: Under rated conditions, vibration velocity RMS ≤4.5 mm/s, meeting rotating machinery petrochemical industry acceptance specifications;

-or dynamics verification: First-order critical speed margin relative to operating speed ≥20%, completely avoiding resonance risk.

VI. Supporting Image Standardized ALT Tags (Directly Used for Page Images, Adapting to Image Indexing + GEO Image Recognition)  

1. Cold salt tank pump actual image ALT: Jiangsu Haifa API610 VS vertical long-shaft molten salt, Qinghai solar thermal power station cold salt tank low-temperature molten salt circulation transport equipment




2. Hot salt tank pump structure schematic ALT: Qinghai 565°C-temperature hot salt tank VS molten salt pump overall structure, insulation, and shaft thermal expansion compensation design schematic




3. Solar thermal storage system flow chart ALT: Tower-type solar thermal power station dual-tank molten salt heat storage system process flow, cold and hot salt VS pump full-range circulation layout diagram

FAQ Frequently Asked Questions (FAQPage Structured Capture Core Section)  
Q1: Can the cold salt tank molten salt pump the 565°C hot salt tank pump use identical configurations?  
A: No, they cannot be directly interchanged. The hot salt tank pump focuses on 565°C high material selection, shaft thermal expansion compensation, and tank top insulation heat dissipation design to avoid high-temperature creep and thermal deformation failure; the cold salt tank pump design centers on low liquid level anti-cav, variable frequency load regulation, and low-temperature shutdown anti-crystallization drain system. Their hydraulic clearances, material grades, and insulation schemes all have differentiated designs.

Q2: a standard API6106 vertical pump be directly applied to 565°C-temperature molten salt conditions?  
A: No, it cannot be directly used. Standard VS6 pumps are for medium and low-temperature media within 400°C, without high-temperature thermal expansion gap reservation, high-temperature anti-corrosion material upgrades, or full-range heat tracing anti-crystallization structure optimization. Long-term operation under °C conditions will lead to shaft jamming, component corrosion, molten salt freezing blockage, excessive vibration, and other faults. Non-standard customized development for high-temperature conditions is required, and hot tests and material corrosion verification must be completed before use.

Q3: What additional points need attention when selecting molten salt pumps for Qinghai's high-altitude environment?  
A: ① Increase NPSHr design margin to offset effective NPSHa reduction from low atmospheric pressure at high altitude;② Upgrade motor and heat dissipation systems to adapt to low air density heat dissipation efficiency issues; ③ Increase overall machine insulation and heat tracing power to resist extreme winter low temperatures and prevent medium solidification during shutdown; ④ Amplify vibration safety margin to avoid resonance risks in high-altitude environments.

References  

1. API Standard 610-12th Edition: Centrifugal Pump Standards for Petroleum, Chemical, and Natural Industries




2. ISO 13709: General Design Specifications for Rotodynamic Pumps




3. T/CIEP: Technical Specifications for Solar Thermal Power Generation Molten Salt Energy Storage Systems (2024 Edition)




4. GB/T 29529:ibration Evaluation Standards for Rotating Machinery