Generator Turning Gear

[Yaima President]

Ajacking gear (also known as a turning gear) is a device placed on the main shaft of an engine or the rotor of a turbine. The jacking gear rotates the shaft or rotor and associated machinery (such as reduction gears and main steam or gas turbines), to ensure uniform cool-down. Without turning, hogging or sagging can occur. Additionally, the jacking gear's assistance in rotation can be used when inspecting the shaft, reduction gears, bearings, and turbines. As an auxiliary function, the jacking gear also helps to maintain a protective oil membrane at all shaft journal bearings.

The jacking gear motor is generally designed to rotate the shaft at approximately 1/10 rpm. Most jacking gear motors are rated at 5hp. The jacking gear motor assembly applies power and torque to the reduction gear by a flexible coupling or clutch that can freely engage and disengage to the high-pressure pinion (driving gear). Engaging is accomplished by means of a simple lever. Some newer propulsion arrangements utilize an automatic control system located in the engine room. Jacking gears often feature a lock to prevent the shaft from turning during current or tide changes or when being towed.

But some industrial gas turbines (GE Frame 5 and Frame 6 types) use a jacking system in which two hydraulic cylinders rotates the shaft about 1/4 turn in one or two seconds every 30 seconds.

GE Frame 9B gas turbines, in which accessories were designed in beginning of 1970's by Alsthom Belfort engineering, use a high pressure hydraulic motor which connects to the main shaft through an automatic SSS Clutch. Turning speed was chosen about 6 RPM, because the resisting torque is the smallest at this speed, then requiring a very low power.

A jacking gear (also known as a turning gear) is a device placed on the main shaft of an engine or the rotor of a turbine. The jacking gear rotates the shaft or rotor and associated machinery (such as reduction gears and main turbines), to ensure uniform cool-down.

Since I have defined the centres and pitch diameters of the gears, I would have thought this would be enough information for the gear generator tool to be able to create gear designs. But instead I'm prompted to manually enter the desired gear ratio (this should be the ratio of the two cylinder diameters). To make things worse, I can't seem to make the gear ratio value linked to any other parameters, so I can't set it to be equal to the ratio between the cylinder diameters.

I want the gear ratio to be defined by the cylinder parts, because the gear ratios in the mechanism are dependent on other geometry, so if I change one part, I need the gear ratios to update accordingly.

Something else I noticed is that the gear generator features only remove material from the cylinders, and don't add material, so if my cylinders are the diameter of the gear pitch diameter, I won't get the ends of the teeth. instead the teeth will be truncated / shorter than required. A workaround I used is to increase the diameters of the cylinders, but this just seems a bit unnecessary. I do understant where this would be preferable behaviour, but is there no way of changing this for cases like mine?

I really appreciate any help as I am using this for the first time, and for a personal project. I am beginning to think that defining gears from pitch-diameter-cylinders is not the normal way of operating, but I thought that was a very intuitive way of doing it so it's quite surprising to me if that's the case.

The Energy Transition is driving decarbonisation of the electrical system with massive investment in renewables at the same time as retiring traditional generating plant. SSS is at the forefront of this innovation, enabling flexible power generation and supporting electrical grid stability and system strength.

Turbo-machinery for the production of electricity includes some of the most powerful machines ever constructed. SSS provides solutions to meet the modern electricity market's requirements in many different generating plant configurations.

SSS Clutches automate engine changeovers in propulsion systems for naval ships, cargo vessels, fast ferries and special pleasure yachts. Our clutches are also used in ship electrical generation systems. SSS is the benchmark for operating flexibility and reliability in the tough conditions of the marine environment.

SSS Clutches enable fans, pumps, compressors and other industrial systems to be dual driven. The drive can be transferred from one prime mover to the other automatically at any speed. Dual driven systems provide Energy Recovery, Redundancy, Maintenance during operation, Startup and Helper (boost) drives.

SSS Clutches are the key mechanism in auxiliary drives such as gas and steam turbine slow speed turning gears, gas turbine starter drives and accelerator drives to run electrical generators to synchronous speed. More than 40,000 SSS Clutches have been supplied to automatically connect/disconnect auxiliary drives.

Turner gears are used for turning the wind turbine rotor during single blade installation. This is a very critical operation and the unbalanced weight of the rotor requires a safe rotating process and tools that are robust and precise. Danhydra holds more than 20 years of experience developing, manufacturing, and servicing turning gears for blade installation.

During the development work, our engineers put a great effort into ensuring that the solutions are easy to install and operate to make the blade installation as fast and efficient as possible. Even the hoisting principles are incorporated into the design process to make this process as cost effective as possible.

As mentioned in the previous module, any attempt to run up the turbine with an excessively deformed shaft is bound to fail because high vibration would sooner or later force a turbine trip. Meanwhile, the turbine generator would be unnecessarily exposed to increased risk of damage due to high vibration and/or rubbing.

If the turbine generator were prewarmed with the rotor held stationary, rotor and casing hogging would develop due to thermal stratification of . the atmosphere inside the machine as outlined in the earlier turbine courses. This would make runup impossible until the hogging is roiled out.

To achieve these two objectives, the turning gear is started early during unit startup such that the turbine generator can spend enough time on turning gear. In principle, the duration or turning gear operation must be enough to:

Meet the additional requirements (if any) regarding the minimum time on U1Dling gear that is necessary to equalize turbine casing temperature. This allows us to make sure that the casing is straight, despite lack of instrumentation that would measure casing hogging or sagging.

The required minimum time on turning gear varies from station to station, reflecting the operating experience of the turbine manufacturer. Usually, the minimum time depends on the duration of the preceding shutdown during which the turbine generator rotor was left stationary, and may reach up to 24 hours.

When turbine runup begins, the U1Dling gear disengages automatically as soon as turbine speed starts increasing. The turning gear motor, however, keeps running until turbine speed reaches a certain level at which the motor switches off automatically. The extended period of motor operation is a precaution taken to make sure the turning gear is available for proper turbine shutdown, should the turbine runup have to be aborted.

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Customers frequently need a rotor turning drive when the OEM turning gear motor stops working or loses its AC or DC power source for a longer period of time than a few minutes. The Hutter Putter Backup Turning Device allows the operators to continue to rotate hot rotors using Hutter Putter instead. This Hutter Putter comes with an air motor or hand crank driver and is permanently mounted but not coupled until its required. It then couples directly to the existing Turning Gear motor shaft or directly to any rotor using a quick connect coupling. Besides plant operators, the turbine maintenance department can couple up this device during outages to provide maintenance turning of the rotor train when needed, saving time and making job safer. Save your rotor from damage!

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attention is paid to the protection of the generator when the unit is off line. For example, protective devices that are crucial in avoiding disastrous occurrences are left on operational. It is important that when the unit is off line, the protective relaying systems are kept operational, and if work is being carried out on them, any risk be ascertained and mitigating action be taken.

This article discusses situations which may lead to accidental inadvertent/back energization of generator, effect of accidental inadvertent/back energization of generator on generator components, the typical means for detecting this abnormal condition and the tripping/protection practices against this condition.

Accidental inadvertent energization of a generator may happen If a generator is at rest/turning gear and the main generator three-phase circuit breaker is accidentally incorrectly closed connecting it to the power system.

The problem is particularly prevalent on large generators that are commonly connected through a disconnect switch to either a ring bus or breaker-and-a-half bus configuration. These bus configurations allow the highvoltage generator breakers to be returned to service as bus breakers, to close a ring bus or breaker-and-a-half bay when the machine is off-line. The generator, under this condition, is isolated from the power system through only the high-voltage disconnect switch. While interlocks are commonly used to prevent accidental closure of this disconnect switch, a number of generators have been damaged or completely destroyed when interlocks were inadvertently bypassed or failed and the switch accidentally closed.

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