KSB HPK-L Hot Water Circulation Pump 

The KSB HPK-L series horizontal radially split volute pump, with its air-cooled bearing support design that requires no external cooling, temperature resistance up to 400°C, and pressure rating of 40 bar, has become a benchmark product in large and medium-sized heating systems and forced circulation boilers.

KSB HPK-L Hot Water Circulating Pump: Expert in High-Temperature Heat Transfer Without External Cooling

In high-temperature applications such as hot water circulation, district heating, and thermal oil transfer, the reliability of the pump directly affects the continuous and safe operation of the entire system. The KSB HPK-L series horizontal radially split volute pump, with its air-cooled bearing support design requiring no external cooling, temperature resistance up to 400°C, and pressure rating of 40 bar, has become a benchmark product in large and medium-sized heating systems and forced circulation boilers.

KSB HPK-L Hot Water Circulation Pump 

The HPK-L is a horizontal, single-stage, single-suction centrifugal pump from KSB, specifically designed for hot water and

 thermal oil transportation. This product conforms to ISO 2858/ISO 5199 international standards and features a back-extraction 

design. Its core innovation lies in the integration of an insulation layer and a fan impeller cooling system, allowing the sealed 

chamber to maintain low-temperature operation without external cooling water.

This design makes it particularly suitable for:

Large and medium-sized heating systems

Forced circulation boilers

District heating networks

Thermal oil (heat transfer medium) circulation systems

KSB HPK-L Hot Water Circulation Pump  Core Technical Parameters

Basic Performance Range

Parameter Item | Value Range

Flow Rate Range | 1 ~ 1,400 m³/h

Head Range | 3.5 ~ 233 m

Maximum Allowable Working Pressure | 40 bar

Medium Temperature Range | -40°C ~ +400°C

Interface Diameter | DN 25 ~ 250

KSB HPK-L Hot Water Circulation Pump Materials and Structure

Components Material

Pump Housing GP240GH+N / A216 GR WCB (High-Temperature Cast Steel)

Impeller JL 1040 (Cast Iron)

Pump Shaft 1.7706 (High-Temperature Alloy Steel)

Bearing Type Rolling Bearing + Sliding Bearing Combination

Lubrication Method Grease/Oil Lubrication

KSB HPK-L Hot Water Circulation Pump  Core Design Features and Technological Advantages

1. Revolutionary Design Eliminating External Cooling Required

Traditional high-temperature pumps typically require external cooling water lines to reduce the temperature of the

 sealing cavity, increasing system complexity and operating costs. HPK-L completely solves this problem through the 

following design:

Heat Barrier Structure: A dedicated insulation layer is installed between the pump body and the bearing bracket, 

effectively blocking heat conduction from the high-temperature medium to the bearing side.

Integrated Fan Impeller: An integrated fan impeller is mounted on the bearing bracket, utilizing the pump's own rotation

 to generate cooling airflow, continuously air-cooling the sealing cavity.

Actual Effect: The mechanical seal cavity temperature is consistently maintained at a low temperature, completely eliminating

 the need for cooling water, saving water resources and eliminating the installation and maintenance costs of cooling water lines.

2. 40bar High Pressure Rating + 400°C Temperature Resistance

HPK-L's PN 40 pressure rating and 400°C temperature resistance enable it to perform exceptionally well under high-temperature

 and high-pressure conditions. Whether in a large-scale district heating network (typically 1.6-2.5 MPa) or a closed-loop circulation

 system for thermal oil boilers, the HPK-L operates stably.

3. Back-Pull-Out Design: Maintenance Without Piping Dismantling

The HPK-L's back-pull-out design, compliant with ISO 2858/ISO 5199 standards, allows for easy removal of the entire rotor 

assembly, including bearings, shaft, impeller, and mechanical seal, simply by unscrewing the bolts connecting the bearing

 bracket to the pump body. This eliminates the need to dismantle the pump casing and inlet/outlet piping.

This design significantly reduces maintenance downtime, making it particularly suitable for continuous heating systems.

4. Optional Dual Seals: Enhanced Safety for Thermal Oil

For hazardous media such as thermal oil, the HPK-L can be configured with a tandem dual-end mechanical seal. This dual-seal 

structure provides additional safety; even if the primary seal fails, the secondary seal prevents leakage.

Note: The maximum temperature resistance for the single-end face version of the 4HL mechanical seal is 130°C. The double-end 

face configuration is suitable for higher temperature scenarios.

5. High-Efficiency Hydraulic Model

KSB has continuously optimized the internal flow channels of the HPK-L, achieving higher hydraulic efficiency compared to the

 previous generation. For heating systems operating continuously throughout the year, the energy-saving effect of this efficiency

 improvement is significant.

6. ATEX Explosion-Proof Certification

The HPK-L can be equipped with an ATEX-certified version, suitable for environments with flammable and explosive risks. 

In scenarios such as thermal oil systems in chemical plants or natural gas boiler rooms, this certification is a necessary condition 

for equipment selection.

KSB HPK-L Hot Water Circulation Pump Detailed Explanation of Main Application Scenarios

1. Large and Medium-Sized Hot Water Heating Systems

Typical Scenario: Primary/Secondary Network Circulation in Urban District Heating

Operating Characteristics: High flow rate (up to 1400 m³/h), high head (up to 233 m), 24-hour continuous operation

HPK-L Value: The design eliminating the need for cooling water simplifies pump room layout; the back-extraction structure 

facilitates maintenance; and high pressure resistance meets primary network pressure requirements.

2. Forced Circulation Boilers

Typical Scenario: Forced circulation systems for industrial boilers

Operating Characteristics: High medium temperature (up to 350°C), frequent pressure fluctuations

HPK-L Value: 400°C temperature resistance + 40 bar pressure resistance fully covers the forced circulation requirements of boilers.

3. District Heating Network

Typical Scenario: Long-distance pipelines supplying hot water from thermal power plants to urban users

Operating Characteristics: Long transmission distance, large pressure drop, and extremely high requirements for pump stability

HPK-L Value: Wide performance range (1400m³/h/233m) to cover the needs of pipeline networks of different scales

4. Heat Transfer Oil (Heating Medium) System

Typical Scenario: Heating of chemical reaction vessels, textile printing and dyeing setting machines, plastic calendering machines, etc.

Operating Characteristics: The medium is organic or synthetic heat transfer oil, the operating temperature is usually above 300°C, 

and the risk of leakage is high.

HPK-L Value: Optional double-end mechanical seal for leak prevention, thermal barrier structure + fan cooling to ensure bearing

 system stability at high temperatures.

Operation and Maintenance Points

Operating Precautions

According to the HPK-L installation and operation manual, the following key points should be noted during operation:

Inspection Items | Requirements

Bearing Temperature | Must not exceed 90°C (measured externally to the bearing housing)

Operating Status | Must be stable, without abnormal vibration or noise

Mechanical Seal | Regularly check for leaks

Dry Operation Prohibited | Operation without liquid filling is strictly prohibited

Long-Term Operation with Valve Closed Prolonged Operation with Outlet Valve Closed Can Cause Overheating of the Medium

Cooling System Maintenance

KSB recommends shutting down the pump at least once a year for a thorough cleaning of the cooling system. Since the HPK-L relies 

on fan impellers for air cooling, keeping the fan blades and heat dissipation channels clean is crucial to ensuring cooling efficiency.

Standby Pump Management

For systems with one main pump and one standby pump, it is recommended to start the standby pump once a week to ensure it 

can be readily used in case of main pump failure.

Parameter Comparison: 50Hz vs 60Hz

The HPK-L is compatible with both 50Hz and 60Hz power supplies. Performance parameters at different frequencies can be

 customized according to customer needs.

Taking the HPK-LS4 050-250 model as an example (50Hz operating condition):

Parameter Values

Speed: 2663 rpm

Flow Rate: 50 m³/h

Head: 83 m

Efficiency: 65.2%

Shaft Power: 14.92 kW

Impeller Diameter: 243 mm

KSB HPK-L Hot Water Circulation Pump  

The HPK-L is suitable for hot water/heat medium circulation scenarios with high requirements for high-temperature

 reliability and operational stability. When selecting this model, it is recommended to focus on the following:

Medium temperature: Confirm whether it is within the range of -40°C to +400°C.

System operating pressure: HPK-L has a maximum pressure of 40 bar; please verify if this is met.

ATEX explosion-proof requirement: Select the explosion-proof version if there is a flammable or explosive environment.

Sealing method: For hazardous media such as heat transfer oil, a double-end mechanical seal is recommended.

Cooling water requirement: HPK-L does not require external cooling water, but ensure good ventilation in the pump room to 

ensure effective heat dissipation of the fan impeller.