Dry Gas Seal Carrier Load Control for Slow-Roll Wear Reduction

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Solution Overview

Problem

Mechanical seals face issues with excessive wear and hang-up due to frictional contact during slow roll conditions and inadequate gas conditioning, leading to premature failure and leakage, especially when dirty hydrocarbon gas condenses on the sealing surfaces.

Innovation Solution

An electromagnetically controllable carrier system with a magnetic ring and annular solenoid is used to modulate axial forces, reducing friction between seal rings and preventing hang-up by counteracting spring preload forces, allowing for controlled axial movement and minimizing contact between seal faces, even at low speeds.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If spring preload force is increased to maintain seal face contact, then sealing reliability is improved, but frictional wear increases during slow roll conditions

Engineering Contradiction:

Improvesealing reliabilityVSAvoidseal face lifespan

Core Design Contradiction:

ReliabilityVSDuration of action of moving object

Solution Approach 1:

The patent applies dynamic control of the carrier position using an electromagnetic actuator that adjusts the axial force on the carrier based on rotational speed. During slow roll conditions, the actuator reduces the axial force to minimize frictional contact between seal faces, while during high-speed operation, it increases the force to maintain proper sealing contact. This dynamic adjustment resolves the contradiction between maintaining sealing reliability and reducing wear.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of axial force applied to the carrier based on operating conditions. By using a controller that monitors rotational speed and adjusts the electromagnetic actuator accordingly, the system varies the axial force parameter to optimize both sealing performance and wear reduction across different operating regimes.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If spring preload force is increased to prevent hang-up, then carrier movement reliability is improved, but friction between carrier and balance diameter sealing element increases

Engineering Contradiction:

Improvecarrier movement reliabilityVSAvoidfriction force

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

The electromagnetic actuator dynamically adjusts the axial position of the carrier based on rotational speed feedback. During slow roll conditions, the actuator positions the carrier to reduce friction between the carrier and balance diameter sealing element, preventing hang-up while minimizing frictional forces. This dynamic positioning resolves the contradiction between ensuring carrier movement reliability and reducing friction.

Inventive Principle:

Principle #15Dynamics

3Duration of action of moving object

If DLC coating is applied to reduce friction, then wear resistance is improved, but manufacturing complexity increases

Engineering Contradiction:

Improveseal face durabilityVSAvoidmanufacturing process simplicity

Core Design Contradiction:

Duration of action of moving objectVSEase of manufacture

Solution Approach 1:

The patent replaces the mechanical solution of DLC coating with an electromagnetic control system. Instead of relying on specialized surface coatings to reduce friction, the system uses an electromagnetic actuator to dynamically control the contact between seal faces, eliminating the need for additional manufacturing steps like DLC coating while achieving the same wear reduction effect.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

This solution extends the lifespan of dry gas seals by reducing frictional contact and preventing hang-up, maintaining seal integrity and reducing leakage, without requiring additional coatings like DLC and fitting within existing compressor designs.

Implementation Method 1

The solenoid can provide a magnetic force to urge a magnetic ring axially

Methodology Applied

Scientific EffectElectromagnetic force: Electromagnet

Implementation Method 2

The magnetic ring can be operably coupled to the carrier, such that the magnetic force operates to counter the preloaded spring force

Methodology Applied

Scientific EffectMagnetic force: Magnetic Field

Data Source

PatentUS11015714B2Dry gas seal with electronically controlled carrier load

Publication Date: 2021.05.25 JOHN CRANK UK

AI summary

A mechanical seal assembly with an electronically controllable carrier load. The assembly includes a magnetic ring affixed to the carrier and driven by a solenoid. The solenoid can apply an axial force to the carrier. The carrier load can be controlled to prevent or reduce friction between the primary ring and mating ring in slow-roll running conditions by partially or completely compensating a spring force provided by a biasing mechanism. The carrier load can further be controlled to inhibit seal hang-up. In embodiments, desired the carrier load can be determined by rotational speed. In embodiments, carrier load can be determined based on sensor signals.