Inst ToolsInst ToolsInst Tools
  • Courses
  • Automation
    • PLC
    • Control System
    • Safety System
    • Communication
    • Fire & Gas System
  • Instrumentation
    • Design
    • Pressure
    • Temperature
    • Flow
    • Level
    • Vibration
    • Analyzer
    • Control Valve
    • Switch
    • Calibration
    • Erection & Commissioning
  • Interview
    • Instrumentation
    • Electrical
    • Electronics
    • Practical
  • Q&A
    • Instrumentation
    • Control System
    • Electrical
    • Electronics
    • Analog Electronics
    • Digital Electronics
    • Power Electronics
    • Microprocessor
  • Request
Search
  • Books
  • Software
  • Projects
  • Process
  • Tools
  • Basics
  • Formula
  • Power Plant
  • Root Cause Analysis
  • Electrical Basics
  • Animation
  • Standards
  • 4-20 mA Course
  • Siemens PLC Course
Reading: What is Barring Gear Logic? Why is it Required in the Steam Turbine?
Share
Notification Show More
Font ResizerAa
Inst ToolsInst Tools
Font ResizerAa
  • Courses
  • Design
  • PLC
  • Interview
  • Control System
Search
  • Courses
  • Automation
    • PLC
    • Control System
    • Safety System
    • Communication
    • Fire & Gas System
  • Instrumentation
    • Design
    • Pressure
    • Temperature
    • Flow
    • Level
    • Vibration
    • Analyzer
    • Control Valve
    • Switch
    • Calibration
    • Erection & Commissioning
  • Interview
    • Instrumentation
    • Electrical
    • Electronics
    • Practical
  • Q&A
    • Instrumentation
    • Control System
    • Electrical
    • Electronics
    • Analog Electronics
    • Digital Electronics
    • Power Electronics
    • Microprocessor
  • Request
Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Inst Tools > Blog > Power Plant > What is Barring Gear Logic? Why is it Required in the Steam Turbine?

What is Barring Gear Logic? Why is it Required in the Steam Turbine?

Here in this article, we will discuss what is barring gear and barring gear logic .why it is required in the steam turbine.

Last updated: September 28, 2022 3:31 pm
Shiv Kumar
Power Plant
2 Comments
Share
6 Min Read
SHARE

Here in this article, we will discuss what is barring gear and barring gear logic .why it is required in the steam turbine.

Contents
What is Barring Gear?Why do turbines keep turning gear after shutdown?Types of Turning Gear

Barring Gear is also known as Turning Gear.

The Barring Gear of the turbine depends upon

  • Turbine RPM
  • Lube oil Header Pressure
  • Overhead tank level
  • Emergency oil pump

What is Barring Gear?

Barring gear is the mechanism provided to rotate the turbine rotor shaft at a lower speed during the stoppage period.

With the aid of an external device or motor using a set of gearboxes attached to the turbine shaft.

Barring Gear is the most important mechanism in a power plant where the turbine unit is in stopping condition.

Turbine has two parts

  1. STATOR BLADES – these blades are mounted on lower and upper casings.
  2. ROTARY BLADES – these blades are mounted on rotors.

As the superheated steam enters the turbine the steam expands through stages and the turbine rotor starts to rotate at a speed of 8300 RPM. The steam turbine is coupled to 3 Phase, 4 pole synchronous generator speeds of 1500 RPM.

Now if the turbine is shut down or the turbine is not in operation over a period of a couple of weeks or a month.

The turbine rotor shaft tends to bend or deflect at the center portion due to the hot gases or steam rising upwards, and the temperature increases at the upper casing.

While the temperature at the bottom casing temperature gets low which results in contraction.

Barring Gear Logic
Barring Gear Logic Activated

This can cause a relatively high differential expansion as the clearance between stator and rotor blades are very low so it can cause serious damage to the turbine. This is known as hogging or upward bowing of the shaft.

Usually, in the Sugar Industry, the Turbine runs only for the period of 6 to 7 months in a year. 

The speed of the barring gear in a steam turbine varies with the turbine specification and is within the range of 110 to 300 RPM.

The ideal Speed of the barring gear in the turbine is 155 RPM (Siemens and Triveni Turbine)

The main purpose of barring gear in Turbine is to prevent sagging and hogging

  • Sagging: Sagging in the turbine rotor shaft is bending the shaft downwards curve in the middle
  • Hogging: Hogging in the turbine rotor shaft is bending the shaft upwards curve in the middle

 The sagging and hogging usually occur when the shaft is installed in a horizontal direction.

When the speed of the turbine rotor is reduced to  Zero RPM due to an Accidental Trip or during the time of Shut Down.

Due to the heavyweight of the turbine rotor and high temperature of about 400 Degrees Celsius. The turbine rotor shaft starts to deform (Bend).

What is Barring Gear
Barring Gear Logic Deactivated

The stator and rotor blades start touching each other and the vibration occurs during the rotor movement. That may damage the system.

To avoid this vibration and Damage in the system the turbine must be engaged with Barring Gear in Auto Mode or by the operator in Manual Mode as directed by OEM.

Rotating the shaft with Barring Gear has advantages

  1. Avoids the shaft bending
  2. Helps in cooling down the rotor  by circulating the air

During Cold/Warm start-up of the turbine, the barring gear should be kept in service for a period of 12 Hours (or more) as advised by the manufacturer, the Jacking oil temperature must be maintained to 40 degrees.

During shut down of the turbine, the barring gear should be kept in service for 48 hours as advised by the manufacturer,

Why do turbines keep turning gear after shutdown?

To avoid the hogging (bending downwards) or sagging (bending upwards) effect of the turbine the turning gear is used after shutdown.

There is a temperature difference in the lower casing and upper casing of the turbine after shutdown. If we keep the turbine shaft stationary then it will bend the turbine rotor shaft, to avoid this problem the turbine should be rotated at a slower speed.

Types of Turning Gear

There are generally three types of turning gear are used

Electrical Turning Gear

The electrical motor is used in this type of turning gear to rotate the turbine rotor at the speed of 200 rpm. A reduction gear is used to reduce the speed.

Hydraulic Turning Gear

In this system, a hydraulic turbine wheel is mounted on the shaft of the turbine. High-velocity oil is supplied from the Jacking Oil Pump which rotates the blade of hydraulic turning gear hence the turbine rotor.

This system will start after the starting of the Jacking Oil Pump. Most advanced turbines use this system.

Hand Barring System

If the electric or hydraulic system fails then hand barring is done with slow speed through a lever and handle.

Don't Miss Our Updates
Be the first to get exclusive content straight to your email.
We promise not to spam you. You can unsubscribe at any time.
Invalid email address
You've successfully subscribed !

Continue Reading

Importance of Instrumentation Engineering – Objectives
Proportional Valve and Servo Valves
What is Boiler blowdown ?
Parts and functions of Steam Turbine
What is a Boiler Draught System? – Purpose, Types, Advantages
What is Turbine Supervisory Instrumentation (TSI)?
Share This Article
Facebook Whatsapp Whatsapp LinkedIn Copy Link
Share
2 Comments
  • sudhakara A M says:
    June 10, 2023 at 5:09 am

    TURBINE ROLLIMG TIME WHILE VACUUM PULLED THEN ROTER JAM BARRING GEAR MOTOR TRIPPED WHY?

    Reply
  • Paramdeep Singh says:
    November 25, 2023 at 6:01 am

    Hi, thanks for the detail information on barring gear.
    I have seen many small turbine (3 to 5MW) in which baring gear was not provided.
    Can you explain what are the cases in which barring gear is not required?

    Reply

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Stay Connected

128.3kFollowersLike
69.1kFollowersFollow
210kSubscribersSubscribe
38kFollowersFollow

Categories

Explore More

What are the Interlocks for Steam Turbine?
8000 RPM 8000 kW Turbine Problem
Stroke Checking Procedure for GCV, SRV, IGV, and LFBV
Gas Turbine Troubleshooting Tips
Burner Management System Logic and Interlock
What is an Air Pre-heater? – Types, Working, Advantages
Coal Based Fuel Feeding System for Boiler
Gas Turbine Control System

Keep Learning

Turbine Bypass System

Turbine Bypass System

30% Feed Control Valve

Purpose of 100% and 30% Feed Control Valves in a Power Plant

Deaerator Pressure and Level Control System in Power Plants

Deaerator Pressure and Level Control System in Power Plants

Electrostatic Precipitator

Principle of Operation of an Electrostatic Precipitator

Working of Proximitor

Different Types of Turbine Protective Devices

Conductivity Meter for Medium Concentration

Measurement of Impurities in Water and Steam – Power Plant

Single Phase Energy Meter

Measurement of Electrical Parameters in Steam Turbine

Barometric gage with Magnetic Float

Process and Mechanical Parameters in Steam Turbine

Learn More

Digital Control Systems

Difference Equations

Safety Instrumented System Engineer Interview Questions

Safety Instrumented System Engineer Interview Questions

Selector Control Function in DCS

Selector Control Functions

Why Starting Current of Induction Motor is High

Best Online Courses to Learn Electrical Engineering

Best Online Courses to Learn Electrical Engineering

Process Control Instrumentation Terms Glossary

Process Control Instrumentation Glossary

Connecting Blocks in Functional Block Diagram

Connecting Blocks in Functional Block Diagram – Studio 5000

CAN based Projects

CAN based Projects – Controller Area Network Protocol

Menu

  • About
  • Privacy Policy
  • Copyright

Quick Links

  • Learn PLC
  • Helping Hand
  • Part Time Job

YouTube Subscribe

Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Welcome Back!

Sign in to your account

Username or Email Address
Password

Lost your password?