Method for handling the shutdown of a turbomachine string in a liquefaction plant of a gaseous product

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Solution Overview

Problem

In LNG production plants, the shutdown of one turbomachine string leads to a sudden increase in refrigerant flow to the remaining string, potentially causing under-speed and shutdown due to power overload, resulting in halted production.

Innovation Solution

A method and control unit that detect the shutdown of one turbomachine string and promptly increase the driving torque on the second string's shaft until a preset speed or time is reached, anticipating and managing the increased load to prevent power overload and maintain production.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If one turbomachine string shuts down, then the refrigerant flow is concentrated on the remaining string, but the absorbed power increases suddenly causing under-speed shutdown

Engineering Contradiction:

Improvecontinuous operation of active stringVSAvoidabsorbed power of compressor

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The control system detects the shutdown of one string and proactively increases the driving torque on the remaining active string before the compressor speed drops to dangerous levels. This preliminary action prevents the under-speed shutdown by anticipating the sudden load increase and compensating for it in advance.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors the speed of the active string and the status of other strings. When a shutdown is detected, the feedback loop triggers an immediate torque increase on the remaining active string to maintain safe operating speed and prevent cascade failure.

Inventive Principle:

Principle #23Feedback

2Power

If the driver supplies maximum power to handle the increased load, then the speed may decrease towards minimum gas turbine speed, but the risk of shutdown increases

Engineering Contradiction:

Improvepower supply capacityVSAvoidrotational speed of shaft

Core Design Contradiction:

PowerVSSpeed

Solution Approach 1:

The control system applies preliminary anti-action by increasing the driving torque before the speed drops to critical levels. This counteracts the tendency toward under-speed shutdown by preemptively compensating for the increased refrigerant flow load, maintaining speed within safe operating limits.

Inventive Principle:

Principle #9Preliminary anti-action

3Use of energy by moving object

If the active string operates near minimum operating speed, then power consumption is reduced, but the risk of shutdown from sudden load increase is higher

Engineering Contradiction:

Improvepower consumption of compressorVSAvoidresistance to under-speed shutdown

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The system maintains readiness to apply preliminary action by continuously monitoring operating conditions. When operating near minimum speed, the control system is primed to immediately increase torque upon detecting a string shutdown, preventing the transition to under-speed shutdown even though the string was operating efficiently at low power consumption.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11486406B2Method for handling the shutdown of a turbomachine string in a liquefaction plant of a gaseous product

Publication Date: 2022.11.01 NUOVO PIGNONE SPA

AI summary

A method for handling the shutdown of a turbomachine string installed in a plant for the liquefaction of a gaseous product comprising at least two turbomachine strings comprises the steps of detecting the shutdown of a first turbomachine string; promptly increasing the driving torque on a shaft of a second turbomachine string when the shutdown is detected; maintaining the driving torque increase on the shaft of the second turbomachine string until a preset speed of the motor driver is reached or a predetermined period of time expires.