The Turbine Train Alignment

Why beat around the bush. Get the turbine's installation catalog and it will detail you. if not available check out the google for the website and catalog.

Dear Ducon,

With great respect but such advice I can give to myself without posting here. Do not you like to use your brain sometimes, just to check if it is in good condition?

you are as rude as you can get. seems to suit you better.

Dear Duncon,

There is no my intention to offend any forum members. If you feel hurt, sorry for this.This is discussion forum and I wanted to start thoughts shareing. As I wrote in my first post here in this topic, my proposal can be wrong and if somebody wants to correct it he is welcome. Do not you think that I had thought about googling this problem or check OEM docs?

These details are going to come to me but before I would like to get others point of view.

Your proposal to go check what is recommended in OEM is the easiest solution but this is not discussion. Maybe my replay was a bit rough but you should not feel touched.

I was but now

Is this train electric? What type of fuel? How big is the turbine? What's the gearbox for? Is it a closed system? How fast does the train go?

This is small (up to 60 MW) reaction turbine, with one shaft, driving the generator trough the gearbox to reduce the rpm. As I wrote I do not know the details yet.

Just wanted to find out if there are general rules how to align such rotating set or maybe there are no general rules ?

I think it should be vertical or horizontal, and balanced....

What catenary?

Yes, I would like to find out if the catenary I proposed in my first post is the right one or not and why

Do you know what a catenary is?

catenary - definition of catenary by the Free Online Dictionary ...

Result of cat plus canary?

as in catenary smile...?

What is wrong in the way I described catenary?

Is not the axis of the rotors coupled together? To get the parallelism of the couplings faces, the bearings supporting the shafts have to be put on different levels vertically. If I am wrong please explain why,

Where are the drawings?

I wrote that the drawings are with OEM but are going to be known for me in coming weeks.

Please let me stress that my intention is not to wait for ready OEM recommendation but to try to use my brain and my experience and get it checked by the forum members.

"I do not know the alignment details but I am going to get them within a few weeks.

Let me guess what should be the proper alignment of the train."

Dear squpek, your guess is missing in your post. I sincerly advise you to come after few weeks after getting the alignment details for any doubt. Why you want other members to make a wild guess on such matters which may vary depending upon the arrangement of equipments, their size and shapes, ambient temperature, operating temperature of three sets of equipments, their speeds, coupling type etc. and at last manufacturer to manufacturer.

Dear Pritam,

After these few weeks I will know everything. I do not want others members to make wild guess. I would like to get their opinion. It can be the case that it is impossible as I have given not enough details or there is no general rules and this would be the answer I can accept as well.

A line sketch of the arrangement would have attracted more guess. Depending on the thermal growth during operation it may require some misalignment in cold condition both in vertical & horizontal directions as well.

You do realize that steam turbines are only efficient if they have a condenser? I really don't know if a radiator is going to do that in the power range your will need.

You seem to be minimizing an extremely complex problem. This so called curve that you want to emulate may have no bearing on the final component placement to obtain the ideal machine train alignment.

the forces involved are mostly thermal in nature but can be influenced by gear bearing reactions and planned machining operations by the OEM prior to shipping the unit.

For instance some generator manufacturers purposely offset the bearing elevations so that at installation the machine can be installed on flat shim packs versus shingling the shim packs to effect alignment.

You will find that gears have a natural tendency to run someplace significantly off dead center, the reason should be obvious. It is not unusual for gears in the MW range you are speaking of to have this factored in.

The turbine will have two ends with extreme temperature differences, you are correct in mentioning that the inlet end is facing the gear box as this and many other things will influence the final optimum elevation because of thermal expansion. The thermal component can be calculated if you have an intimate knowledge of the materials, distances, etc involved, Otherwise you may as well throw some numbers on the paper and go with them.

Then there is empirical knowledge. Even with the most sophisticated calculations there is the occasional anomaly that becomes obvious after years of operation and a trend is established. The manufacturers make these known as they develop.

I personally think you are wasting your time.

Dear Otha,

Your remark can be the right one.

Maybe I am going to minimizing the complex issue but I am pretty sure that this issue has been resolved many times so far :-), so it should not be "terra incognita".

I can agree that it can be too complex and no general rules can be applied. Such explanation is OK for me as well,

Maybe some information to help.

Making Machine Train Alignment More Efficient and Accurate

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Written by MT Staff Friday, 01 April 2005 00:00

Machine trains, like all directly coupled equipment, must be aligned. The objective of any machine train alignment is to align the equipment within specified tolerances at operating conditions. Accurate shaft alignment will increase the life of machine components such as bearings, seals, and couplings, and prolong the life of the machinery. As a result, costly unscheduled downtime is reduced. If alignment can be improved, machinery failure rates decrease. One way to improve the process of alignment is by using a laser alignment system.

Fig. 1. Schematic of steam turbine-boiler feed pump-gearbox-booster pump machine train that was recently aligned using a laser alignment system.

A machine train consisting of a steam turbine, boiler feed pump, gearbox, and booster pump-shown schematically in Fig. 1-was recently aligned at a power company using a laser shaft alignment system. Because a laser alignment tool was used, the time necessary to complete this alignment task was reduced from 4 days to 2 days. The following steps were taken to align the machine using THE laser alignment system.

Alignment obstacles
This machine train possessed many alignment obstacles: the turbine base had settled over time due to environmental issues; the booster pump was subjected to considerable machine frame distortion (soft foot) due to excessive pipe strain; and prior to the outage, the gearbox was overhauled and the bearings were replaced.

Fig. 2. Coupling 1, between the turbine and the main feed pump

Laser mounting accessories
In this example, the provided chain brackets used to mount the laser and receiver were not sufficient to take readings at each of the three couplings. Each coupling required additional accessories for mounting.

Coupling 1, between the turbine and the main feed pump, utilized the standard chain brackets, using the provided 600mm long chains to accommodate the large shaft diameter (Fig. 2). Coupling 2, between the main feed pump and the gearbox, required narrow brackets due to extremely limited clearance axially (Fig. 3). Coupling 3, between the gearbox and booster pump, used magnetic brackets with offset support posts because of obstructions to rotation and limited axial clearance (Fig. 4). The coupling bolts protruded from the coupling hub, requiring a different option than straight support posts. The hardware obstacles were resolved with the optional accessories supplied by the manufacturer of the laser alignment kit.

Fig. 3. Coupling 2, between the main feed pump and the gearbox

"As found" measurements
Multipoint mode. At couplings 1 and 3, measurements are taken with the multipoint measurement mode, which permits rotation of the shaft to a desired location using turning gear, without taking readings along the way. Once rotated, the shaft is relaxed into its natural position so a reading can be taken. Multipoint mode achieves alignment readings without the forces from noncontinuous rotation influencing alignment results.

If excessive vibration from nearby equipment is present, it is necessary to take more samples during each multipoint reading in order to increase the averaging and mitigate possible erroneous information.

Fig. 4. Coupling 3, between the gearbox and booster pump

Pass mode. Coupling 2 provides a challenge for most laser shaft alignment tools. The spool piece is removed during the alignment process. Rotating both coupling halves simultaneously is usually impossible. Pass mode is used to combat this challenge. When measuring with pass mode, the laser is simply rotated past the receiver at least five times over at least 70 degrees of rotation to complete alignment readings automatically.

Once misalignment readings have been taken at all couplings, an overall picture of the "as found" alignment is produced, as shown in Fig. 5.

Machine alignment
One goal during the alignment process is to minimize movement and still reach the alignment objective. Once the "as found" picture is in view, the smallest possible move or optimal move can be calculated. By doing so, the risk of becoming bolt-bound or base-bound (having to lower a machine with no shims under the feet) is reduced.

Fig. 5. "As found" alignment condition

Becoming bolt-bound is one of the most common problems during machine train alignment. When the stationary machine in a train is angled on its base, the other machines in the train need to be aligned to this angle. When moving any given machine in the train, the movements required to achieve tolerances may not be met because the move required is greater than the space remaining between the bolts and the bolt holes. This obstacle then requires additional moves to achieve alignment tolerances, or other less-desirable alternatives, such as enlarging the anchor bolt holes in the feet.

To combat a bolt-bound condition, it is vital to look at the overall picture and explore the various move options. In the example of a pump-gearbox-motor machine train, a quick glance would assign the gearbox as stationary and the pump and motor as moveable. What if the alignment cannot be completed with this configuration? Other alignment options must be explored.

The best option is the static foot function available in some laser alignment systems. This feature permits viewing alignment conditions throughout the machine train while choosing different individual pairs of stationary feet rather than only entire static machines. This allows the user to find a solution with the smallest possible move for the bolt-bound machine.

Fig. 6. "As left" alignment condition Live move mode.In this example, the alignment was performed designating the turbine as the stationary machine. Movement of machinery commenced at the main feed pump, continuing with the gearbox and then the booster pump. The live move mode, which monitors each piece of equipment while it is moved, informs the user when tolerances are met. Because the move is monitored at each pair of feet, machinery is moved without guesswork, and the chances of over-shooting the required correction are reduced.

Target specification computation
The alignment is considered complete when all equipment is within tolerance while incorporating target specifications. Target specifications are deliberate values of offset and angularity that the machines are misaligned to in the nonrunning condition to compensate for expected changes in the alignment that will occur when the machines are made to run and are put under load, usually due to thermal growth or dynamic load shifts. All computations are done in the alignment computer, eliminating the need for cumbersome calculations on graph paper.

"As left" readings
After each piece of equipment is moved into tolerance, a new set of readings should be taken at each coupling. In this case, each coupling was within the suggested alignment tolerances, while incorporating targets (see Fig. 6). The appearance of the smile symbol ensured that the speed-related tolerances were met at each individual coupling.

There are a myriad of machine train configurations for every possible application. Machine trains are often the lifeblood of a plant or mill. Their alignment is crucial due to the cost of downtime, cost of the equipment, and their criticality. Using a versatile laser alignment tool will reduce frustration, save time, and help accomplish the original goal of aligning a machine train within specified tolerances. MT

Information supplied by Irene Hamernick, Ludeca, Inc.

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True Machine Train Alignment

The first system in the market offering this capability for the alignment of multiple-element drives.The new ROTALIGN ULTRA MultiCoupling from LUDECA allows the alignment of up to 7 machines in a train to be measured simultaneously, with a single quarter rotation (or less!) of the shafts. According to the company, the ROTALIGN ULTRA is further highlighted by:

• Better accuracy of the final alignment through optimization of corrective moves throughout the train.
• The power to save time and resources when aligning turbine trains on the critical path in an outage, or machine trains with gearboxes that are difficult to turn.
• Increased efficiency and an easier workload.

www.ludeca.com

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Thank you Ducon.

This is not answer to my proposal but can be usefull

I know I never ment to send it as an answer but as information to all CR4 members. It may help.