Jiangsu Haifa Machinery Manufacturing Co., Ltd.

Jiangsu Haifa High-Temperature High-Pressure Pumps Adopt Shrink Fit Assembly Process | Enhancing Long-Term Operational Reliability of High-Speed Heavy-Duty Rotor Systems

Release Date: 2026--08
Produced by: Jiangsu Haifa Machinery Manufacturing., Ltd. (a restructured enterprise from 1958, deeply engaged in the R&D and manufacturing of API 610 chemical process pumps, providing domestically manufactured high-temperature high-pressure pump equipment for the petrochemical, coal chemical, power, and new energy industries)

Petroleum refining, coal chemical, power station, and new energy all operate in long-cycle continuous production. High-temperature high-pressure pump rotors subjected to long-term high-temperature alternating loads, high-pressure loads, and-speed centrifugal forces. The connection method between the impeller and pump shaft directly determines the operational safety of the entire. Traditional flat key locking structures are prone to stress concentration and fit loosening under high-speed, high-temperature cyclic conditions. Jiangsu Haifa has specifically adopted an impeller-shaft shrink fit interference assembly process on its API 610 high-temperature high multistage pump products strengthening the overall rigidity of high-speed heavy-duty rotors, eliminating the risk of connection failure under alternating working conditions, and ensuring stable operation of critical process units.

I. Why Choose Shrink Fit Assembly Under High-Temperature High-Pressure Conditions

Ordinary centrifugal pumps mostly use flat keys plus lock nuts to secure impellers. This structure is simple easy to assemble and disassemble, cost-controllable, and can meet normal-temperature, medium-to-low-speed operating conditions. However, under the following working conditions, the of key connections are amplified:

1. Pump operating speed > 3,650 rpm

-istage high-pressure pumps operating continuously for extended periods

1. Medium working temperature > 150°C

2. Strict requirements for rotor dynamic stability

High-speed rotation generates enormous centrifugal forces, compounded by thermal cycle impacts from repeated temperature rises and falls. Stress concentration occurs at the keyway position, and the keyway weakens the effective cross-section of the pump. Long-term start-stop alternating cycles can lead to fit loosening and increased vibration, and in severe cases, directly trigger rotor failure. For such demanding conditions, Jiangsu Haifa selects shrink fit interference assembly, relying on metallic interference gripping force to transmit all loads, avoiding the inherent defects of key connections.

II. Shrink Fit Assembly Process Principle

Shrink fit assembly leverages the physical properties of metal thermal expansion and contraction to achieve high-precision interference engagement between the impeller hub and pump shaft. The entire process consists of calculation verification, impeller heating, on-site assembly, and and setting.

2.1 Preliminary Calculation and Simulation Verification

Based on the pump shaft and impeller materials, actual working temperature, rated speed, and medium loads, the interference amount design is completed. Through finite element strength verification, the shaft diameter tolerance, reasonable interference range,eller heating temperature, cooling shrinkage amount are determined, and the contact stress distribution under actual working temperatures is simulated. The interference amount must not be too large, to prevent plastic deformation of the imp hub; nor too small, to avoid mating surface slippage after high-temperature operation. All parameters are output based on the equipment's actual operating conditions.

1. Uniform Impeller Heating

The impeller hub is heated according to the curve, causing controlled expansion of the impeller bore to create assembly clearance, ensuring the impeller can be smoothly fitted onto the pump shaft without forced pressing that could damage the mating surfaces. The heating process strictly controls the heating rate and temperature uniformity to avoid localized overheating of the impeller, deformation or changes to the material's metallurgical structure.

2.3 Positioning, Assembly, Cooling, and Setting

Once the impeller reaches process temperature, it quickly positioned at the designed location on the pump shaft. The impeller naturally cools contracts, with the hub bore gripping the pump shaft to form a uniform, large-contact-area interference friction connection. After assembly, the imp and pump shaft form an integrated rotor assembly, with loads transmitted through mating surface friction rather than relying solely on key forces.

III. Practical Advantages of Jiangsu Haifa's Shrink Fit Assembly ProcessEnhancing Operational Reliability Under High-Speed Conditions

At high speeds, the impeller withstands centrifugal forces, hydraulic loads, thermal stresses, and vibration impacts. Shrink fit assembly relies on full-circumference uniform contact pressure to transmit, eliminating localized stress concentration from key connections, reducing the risk of impeller slippage, and accommodating high-speed rotors at 3,650 rpm and above.

ing to Temperature Alternations, Ensuring High-Temperature Connection Reliability

Frequent start-stop cycles of the unit bring temperature cyclic variations, and differences exist in the thermal expansion coefficients of impeller and pump shaft materials. During the design phase, the material linear expansion coefficients, maximum working temperature, and-stop cycle counts are incorporated into calculations to ensure that the mating surfaces maintain effective interference gripping force under long-term high-temperature service conditions.

izing Rotor Dynamic Performance

The API 610 standard imposes strict requirements on rotor stiffness, critical speed, balance quality grade, and shaft deflection for high-temperature-pressure pumps. The fit structure eliminates largeways, reducing cross-section weakening of the pump shaft helping to improve overall rotor stiffness. Jiangsu Haifa performs shaft strength verification, critical speed calculations, and rotor dynamic balancing checks on the complete rotor assembly, while controlling seal position runout to reduce high-speed operating vibration and protect the service life of mechanical seals and bearing assemblies.

Note: Rotors using shrink fit assembly still a locating key, which serves only for circumferential positioning and does not bear primary load transmission.

IV. Comparison Between Shrink Fit Assembly Traditional Flat Key Connection

| Item Shrink Fit Interference Assembly | Flat Key + Lock Nut Connection |
|------|----------------------------------|-------------------------------|
| Load method | Full-surface friction transmission across mating surfaces | Localized load transmission through flat key |
| Effect on shaft structure | large keyway weakening the shaft cross-section | Keyway causes stress concentration and cross-section weakening |
|able conditions | High-speed, high-temperature, high-pressure multistage pumps |-temperature, medium-to-low-speed ordinary chemical pumps |
|-speed high-temperature stability | Excellent | Fair |
| Maintenance and disassembly | Requires specialized heating tooling and professional procedures | Simple and convenient assembly/disassembly |
| Manufacturing cost | Relatively high | Lower |

V. Key Manufacturing Control Points for High-Temperature High-P Pumps

Jiangsu Haifa strictly follows the API 610 standard in the design and manufacturing of high-temperature-pressure pumps. Not only does the rotor adopt the shrink fit process, but control is also implemented across all critical aspects of the complete unit:

| Technical Control Item | Design and Manufacturing Measures |
------------------------|----------------------------------|
| Pressure component safety | Strength verification of pressure casings such as pump casing and cover; hydrostatic testing per specifications |
| Rotor system | Combined strength and stiffness simulation analysis of the complete rotor (shaft-impeller-coupling) |
| High-speed dynamics | Critical speed verification to ensure sufficient speed margin; strict control of vibration indicators |
| system | Mechanical seal selection and flush plan matched according to temperature, pressure, and |
| Inspection and verification | Raw material physical and chemical re-inspection, rotor dynamic balancing, casing hydrostatic testing, non-destructive testing of components |

Under high-temperature high-pressure conditions, addition to casing pressure containment, special designs are implemented for mechanical seals, bearing systems, rotor balancing, and cooling circuits to ensure long-cycle operation of the equipment.

VI. Main Application Fields of Shrink Fit Assembly High-Temperature High-Pressure Pumps

1. Petroleum refining: hydrogenation unit circulation pumps, high-pressure feed pumps, feed pumps

2. Coal chemical: coal-to-liquid process pumps, syngas supporting system pumps, high-temperature process medium transfer pumps

3. Power and energy: supercritical unit auxiliary pumps, high-temperature demineralized water pumps

4. New energy storage:-temperature molten salt circulation pumps, hydrogen energy process circulation pumps, carbon capture process pumps

FAQ — Frequently Asked Questions

1: Do all centrifugal pumps need shrink fit assembly?
A: No. For ordinary centrifugal pumps operating at normal temperature, speed, and stable loads, flat key connections are sufficient for field service. Shrink fit assembly is primarily used for critical units operating at high speed, high temperature, and high pressure, where unit downtime losses are significant and rotor reliability requirements are stringent.

Q2: Is it troublesome to disassemble shrink fit assemblies during later maintenance?
A: Shrink fit is a high-reliability interference connection. Disassembly requires specialized heating tooling and must be performed according to procedures — forced hammering is prohibited. However, for continuous production units such as petrochemical and coal chemical plants, the of long-cycle equipment operation far outweigh the later maintenance costs, which is why critical rotors preferentially adopt the shrink fit structure.

3: Will shrink fit impellers loosen after operating at high temperatures?
A: No. During the design phase, the working temperature and the differential thermal expansion between the two materials are incorporated into the interference calculation, ensuring that effective interference is maintained even at the maximum working temperature, and the mating surfaces will not slip or loosen.

Reference Standards:

1. API 610 "Centrifugal Pumps for Petroleum, Petrochemical and Natural Gas Industries"

-/T 34807 "Evaluation of rotor dynamics for centrifugal pumps"

1. JB/T 8097 " of vibration measurement and evaluation for pumps"