Subsea Pump Balance Piston Suction Inversion

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Solution Overview

Problem

Conventional subsea pumps with balance pistons located at the outlet face limitations due to total differential pressure, which restricts the maximum achievable pressure and leads to impractical thrust bearing loads and unacceptable rotordynamic effects, especially in deep-water applications where pressure variations are significant at the suction side.

Innovation Solution

Positioning the balance piston closer to the fluid inlet, with mechanical seals exposed to the discharge pressure, allows the barrier fluid pressure to be regulated based on the stable discharge pressure, thereby counteracting the axial force and reducing the burden on thrust bearings.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the balance piston is placed at the pump outlet (discharge side), then the barrier fluid pressure regulation is simplified, but the total differential pressure is limited and thrust bearing loads become impractical

Engineering Contradiction:

Improvebarrier fluid pressure regulation complexityVSAvoidtotal differential pressure limitation

Core Design Contradiction:

Device complexityVSStress or pressure

Solution Approach 1:

The balance piston is inverted from its conventional location at the pump discharge to the pump suction side. This inversion allows the barrier fluid pressure to be regulated based on the stable discharge pressure while the balance piston counteracts axial forces using the pressure differential across the suction side, thereby resolving the contradiction between regulation simplicity and differential pressure limitations.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the reference pressure parameter for barrier fluid regulation from suction pressure to discharge pressure. By maintaining barrier fluid pressure based on the stable discharge pressure parameter while positioning the balance piston at the suction side, the system achieves both simplified regulation and the ability to handle high differential pressures.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If the balance piston is placed at the pump outlet, then the structure is conventional, but the thrust bearing loads become impractical and rotordynamic effects are unacceptable

Engineering Contradiction:

Improveconventional configurationVSAvoidthrust bearing load

Core Design Contradiction:

Ease of manufactureVSForce

Solution Approach 1:

By inverting the balance piston location from discharge to suction side, the axial force distribution on the rotor is fundamentally changed. The balance piston now counteracts thrust forces using suction side pressure differential, dramatically reducing the load on thrust bearings and improving rotordynamic characteristics while remaining manufacturable.

Inventive Principle:

Principle #13The other way round (Inversion)

3Device complexity

If the balance piston is placed at the pump outlet, then the configuration is simple, but the solution is inadequate for deep-water applications with significant suction side pressure variations

Engineering Contradiction:

Improveconfiguration simplicityVSAvoidperformance in deep-water applications

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The inverted balance piston configuration specifically addresses deep-water applications by positioning the balance piston where it can effectively counteract the significant suction side pressure variations characteristic of deep-water operations, while barrier fluid regulation continues to use the stable discharge pressure reference.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent applies local quality by positioning the balance piston specifically at the suction side where pressure variations are most significant in deep-water applications, while the barrier fluid regulation system separately references the stable discharge pressure, creating locally optimized pressure management in different regions of the pump system.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS10132142B2Fluid processing machines with balance piston on inlet

Publication Date: 2018.11.20 ONESUBSEA IP UK LTD

AI summary

A subsea pump is used in applications such as deep-water boosting of fluid produced from a wellbore. The process pressure variation is mostly related to the pump suction side in such applications. The barrier fluid system for the pump regulates its pressure according to the pump discharge pressure. A balance piston is positioned in a location close to the pump inlet such that both mechanical seals are exposed to the pump discharge pressure on the process side.