Nuclear Coolant Pump Seal Chambers for Balanced Pressure Staging

Solution Overview

Problem

Nuclear coolant pump seals face challenges in balancing effectiveness and longevity due to increased wear and leakage issues caused by pressure differentials, which are influenced by fluid conditions and seal geometry, leading to uneven wear and performance in existing designs.

Innovation Solution

A coolant pump design featuring a staging flow pathway with first and second seal chambers, each with static and rotating sealing elements, where fluid is accelerated by a rotor assembly to achieve a balanced pressure drop across multiple seal stages, controlling fluid velocity and pressure to optimize seal performance and longevity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If sealing pressure is increased to maintain pressure differential across seal, then sealing effectiveness is improved, but wear of sealing elements increases

Engineering Contradiction:

Improvesealing effectivenessVSAvoidseal longevity

Core Design Contradiction:

ReliabilityVSDuration of action of moving object

Solution Approach 1:

The seal system is divided into multiple seal stages (first seal stage and second seal stage) arranged in series. Each stage handles a portion of the total pressure differential, so that no single seal stage must withstand the full pressure differential. This segmentation allows each sealing element pair to operate at lower individual pressures, reducing wear while maintaining overall sealing effectiveness across the entire system.

Inventive Principle:

Principle #1Segmentation

2Device complexity

If single-stage seal design is used to simplify structure, then device complexity is reduced, but uneven wear and leakage occur due to unbalanced pressure distribution

Engineering Contradiction:

Improveseal structure complexityVSAvoidseal performance uniformity

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The seal system is divided into multiple seal stages (first seal stage and second seal stage) arranged in series. Each stage handles a portion of the total pressure differential, so that no single seal stage must withstand the full pressure differential. This segmentation allows each sealing element pair to operate at lower individual pressures, reducing wear while maintaining overall sealing effectiveness across the entire system.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The seal stages are designed with dynamic pressure balancing, where the fluid velocity and pressure are controlled to achieve substantially equal pressure drops across each seal stage. This dynamic balancing ensures uniform wear distribution across all sealing elements, improving reliability without requiring overly complex static structural modifications.

Inventive Principle:

Principle #15Dynamics

3Temperature

If fluid velocity is increased to improve cooling, then heat removal is enhanced, but pressure drop across seal becomes unbalanced

Engineering Contradiction:

Improvecooling effectivenessVSAvoidpressure distribution uniformity

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The seal stages are designed with dynamic pressure balancing, where the fluid velocity and pressure are controlled to achieve substantially equal pressure drops across each seal stage. This dynamic balancing ensures uniform wear distribution across all sealing elements, improving reliability without requiring overly complex static structural modifications.

Inventive Principle:

Principle #15Dynamics

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

The design achieves a balanced seal performance and longevity by evenly distributing pressure drops across multiple stages, reducing leakage and wear, and maintaining consistent sealing effectiveness despite dynamic fluid conditions.

Implementation Method 1

fluid passing through the staging flow pathway is accelerated by the acceleration surface

Methodology Applied

Scientific EffectFluid acceleration:

Implementation Method 2

first and second seal stages within the first and second seal chambers, each having a static sealing element and a rotating sealing element, the sealing elements engaging one another to form a fluid-tight seal

Methodology Applied

Scientific EffectMechanical sealing:

Implementation Method 3

The design achieves a balanced seal performance and longevity by evenly distributing pressure drops across multiple stages

Methodology Applied

Scientific EffectPressure drop: Pressure Drop

Data Source

PatentUS11913465B2Nuclear coolant pump seal and methods of sealing

Publication Date: 2024.02.27 CANDU ENERGY INC

AI summary

A seal assembly for a pump comprises a gland housing mounted to the pump casing. A staging flow pathway is defined within the gland housing with multiple seal chambers. A seal stage is positioned in each seal chamber, each having a static sealing element and a rotating sealing element, the sealing elements engaging one another to form a fluid-tight seal. A rotor assembly pumps coolant through the gland housing. Fluid passing through the staging flow pathway is accelerated by an acceleration surface of the rotor assembly. An inlet passage feeds coolant fluid into the staging flow pathway and past the acceleration surface.