Overhung Rotary Pump Pressure Balancing for Axial Thrust Relief
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Solution Overview
Problem
Rotary pumps with overhung impellers face high axial thrust that necessitates expensive and complex axial or thrust bearings, which are not feasible in some applications.
Innovation Solution
A rotary pump design incorporating a pressure chamber upstream of the impeller, connected to a relief passage and balance line, which uses discharge pressure to counteract the axial thrust by creating a balancing force opposite to the impeller-generated thrust.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a strong and large axial bearing is used to support high axial thrust, then the axial thrust can be adequately supported, but the costs and complexity of the pump increase
Solution Approach 1:
A balance drum is introduced as an intermediary component between the impeller and the axial bearing. The balance drum creates a balance chamber that receives high-pressure fluid from the discharge, generating a counteracting axial force that reduces the net thrust on the bearing. This intermediary mechanism allows the use of simpler, less expensive axial bearings while still supporting the required load.
Solution Approach 2:
The invention uses hydraulic pressure from the discharged fluid to create a balancing force. High-pressure fluid is directed into the balance chamber surrounding the balance drum, creating hydraulic pressure that generates an axial force opposing the impeller thrust. This hydraulic balancing system replaces the need for oversized mechanical bearings.
2Ease of operation
If antifriction bearings are used to support axial thrust, then the pump operation is simplified, but they become insufficient when the axial load is too large
Solution Approach 1:
The balance drum acts as an intermediary that reduces the axial load before it reaches the antifriction bearing. By creating a balance chamber that receives high-pressure fluid, the system generates a counteracting force that significantly reduces the net axial thrust, allowing antifriction bearings to operate within their capacity limits while maintaining reliability.
Solution Approach 2:
The invention changes the pressure parameter by introducing high-pressure fluid into the balance chamber. This pressure change creates a force that counteracts the axial thrust, effectively reducing the load parameter on the bearing to a level where antifriction bearings can reliably support it.
3Force
If tilting pad bearings are used to handle high axial thrust, then the load capacity is sufficient, but the lubrication system and costs increase
Solution Approach 1:
The invention uses hydraulic pressure from the process fluid itself to create the balancing force, eliminating the need for a separate lubrication system. The high-pressure fluid from the discharge is directed into the balance chamber, creating a self-contained hydraulic balancing system that reduces axial thrust without requiring additional lubricants or complex lubrication infrastructure.
Solution Approach 2:
The system uses its own discharge fluid to create the balancing force. The high-pressure fluid that is already part of the process is redirected into the balance chamber, allowing the pump system to self-regulate and reduce its own axial thrust without requiring external lubrication systems or additional resources.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Significantly reduces the axial thrust on the shaft, allowing for the use of less complex and less expensive bearings, thereby reducing overall pump complexity and cost.
Implementation Method 1
at least one balance line is provided, which is configured for supplying the fluid having the discharge pressure to the pressure chamber
Implementation Method 2
The pressure chamber, which is arranged on the low pressure side of the impeller, is supplied with the pressurized fluid having the discharge pressure. The rotary part delimiting the pressure chamber at least partially balances the axial thrust
Implementation Method 3
the stationary part and the rotary part are configured to overlap with respect to the axial direction, such that a relief passage is provided between the rotary part and the stationary part, wherein the relief passage extends from the pressure chamber to a low pressure location
Data Source
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AI summary
A rotary pump for conveying a fluid is proposed, comprising a pump housing (2) with an inlet (3) for receiving the fluid having a suction pressure (SP) , and an outlet (4) for discharging the fluid having a discharge pressure (DP), further comprising an impeller (5) for conveying the fluid from the inlet (3) to the outlet (4) and for pressurizing the fluid from the suction pressure (SP) such, that the fluid is discharged with the discharge pressure (DP), and a shaft (6) for rotating the impeller (5) about an axial direction (A), wherein the impeller (5) is configured as an overhung impeller (5), wherein a pressure chamber (15) is arranged upstream of the impeller (5) between the inlet (3) and the impeller (5), wherein the pressure chamber (15) is delimited by a stationary part (18) and a rotary part (16), wherein the stationary part (18) is configured to be stationary with respect to the pump housing (2), wherein the rotary part (16) is fixedly connected to the shaft (6), wherein the stationary part (18) and the rotary part (16) are configured to overlap with respect to the axial direction (A), such that a relief passage (19) is provided between the rotary part (16) and the stationary part (18), wherein the relief passage (19) extends from the pressure chamber (15) to a low pressure location (17), and wherein at least one balance line (30) is provided, which is configured for supplying the fluid having the discharge pressure (DP) to the pressure chamber (15).