API 686 requirements for pump shim

[CaracasEC]

Dear All,
Is it acceptable the pump to be shimmed during alignment? The situation is that during our final alignment, we have noticed that the motor needs to be lower more, to have the alignment tolerance. However, the motor has no shim already and that we need to shim the pump in order to have minimum 3 mm at the motor as per api 686? hoping for your field experiences.,...

 

[JJPellin]

You described two different situations. In the first, you stated that the motor had no shim. I the second, you stated that the motor would not have the required 3 mm of shim. A nominal shim thickness of 3 mm is desirable so that future alignment moves can be made as needed. But, if you can achieve the required alignment with less than 3 mm, you should do so.

If, on the other hand, the motor truly has no shim at all, then you have a couple of choices. You can shim to raise the pump as you suggest, or you can machine down the motor base to allow for shims to be added. Obviously, it is much more expensive and time consuming to field machine the motor base. We had to make this same decision today on a pump. We decided to add shims under the pump. This is not the ideal solution, but it can be acceptable under some circumstances. In our case, the motor and pump were quite small and we had a time constraint that needed to be met. We decided that the addition of a single, ground spacer plate under the pump feet was the best option.

Johnny Pellin

 

[CaracasEC]

Hi Mr. Johnny Pellin,
Thanks for sharing your field experience. Our current situation is that i am on a client side for an ethylene cracker plant construction. However during the alignment of these overhung pumps, our contractor noticed that it cannot meet the API 686 requirement of providing the motor feet with a 3 mm shims and some installation even have 0 shims after the final alignment. What is a better solution to have a reliable pump/motor installation? To shim the pump or and in-place machining of the motor mounting pad. We are dealing with this problem about more than 50 pump/motor units...thanks...

 

[JJPellin]

The option for highest quality and highest reliability would be to machine the motor base. For a new construction project, I would probably require that they meet the specified nominal shim as called out in our pump standard. I might waive my rights to require the nominal shim if it was close. I might accept 2 mm shim if they could not achieve 3 mm. But, I would not accept zero shim and would not accept shimming the pump to achieve the alignment.

I work in a maintenance organization and tend to default to thinking in terms of maintenance repairs of existing equipment. For a new construction, the vendor or contractor should meet the requirements of the contract including the technical specifications and standards for the machinery.

Johnny Pellin

 

[Pumpsonly]

The minimum 3 mm shim under the motor is to be designed into the baseplate support footing. That means you purposely machine the motor support minimum 3 mm lower than calculated height difference the pump and motor shaft center height. During the proof alignment at the factory, the shim thickness must be minimum 3 mm. Do you have this before the final alignment at site? If not,than the
requirement was not met in the first place.

If you can achieve the final alignment at site with less than 3 mm or 0 shim under motor foot, that will be acceptable. You don't need to put 3 mm shim at the pump and motor just to meet the 3 mm shim under motor footing.

Have you consider any hot alignment requirement?

 

[CaracasEC]

Hi Mr. JJPelin & Pumps Only,
Could you please comment on the paragraph below?
Shimming of pump is not acceptable.
Paragraph 6.3.4 of API 610 states that “Shims shall not be used under the pump. All pads for drive train components shall be machined to allow for the installation of shims at least 3 mm thick under each component.” (See attached file)
thanks,

 

[Artisi]

What is there to comment on, it is clearly stated that no shims will be under the pump. The pump is not part of the drive train.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[Pumpsonly]

Well, I would like you to tell us what is your comment on the statement. Why is it not allow?
To start with, look at a complete pump package and try to figure out the procedures in installation, piping and final alignment of the drive train.Then you will understand the reasons behind the statement.

 

[CaracasEC]

For an old installation, shimming of the pump will affect the pipe strain on the pump. On new pump installation, to quote on one of my co-member at other forum "I can understand this multiple shimming technology as an effort of engineeres from API to improve the time consuming and skilful operation of making new shims (metal plates) to ensure a precise alignment with low cost and with less qualified fitters." The pump shim will is just be an added activity during maintenance if the pump will be disturbed. Is it reasonable the in-place machining of the motor pump to acquire high pump reliability installation? thanks..

 

[Pumpsonly]

In a new installation, after the piping are attached to the pump, moving the pump to achieve the shaft alignment is almost not feasible. So why put shims under the pump?
The motor will only have the flexible power cable connected to it.Very often you will find the pump foot is doweled onto the baseplate support.

 

[CaracasEC]

Hi pumpsonly,
If we will put shims to the pump,
1. API 610 will be violated "shims is not acceptable at the pump".
2. As the pump/motor assembly including the skid/baseplate is under vendor warranty, it is still their responsibility to comply on the contract requirements (API 610 requirements).
3. High reliability installation providing that the motor has the only one that have shims which will provide more maintenance flexibility.

 

[Artisi]

CaracasEC, point 2 is correct, reject the pumpset as not being to spec, that is provided you gave the supplier the standard / instructions to work to.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[CaracasEC]

Hi Artisi,
Yes this is provided / given to the vendor though it was not on spec but it was not given on their exception and deviation during the technical clarification meetings. Then it is their full responsibility to comply on the API610 standard...

 

[Artisi]

Correct.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[CaracasEC]

thanks Artisi...

 

[skpatel]

Dear Experts,

During Pump to motor alignment, we achieved the alignment with just 0.5 mm shims under motor base but Client inspector insist to provide minimum 3 mm shims as per API-686 and Project specs requirement.

Can you advise me the reason behind minimum 3 mm shimming is must even if we achieved the alignment with 0.5 mm ?

 

[Artisi]

skpatel, you should start another thread for your question and not piggy-back it onto this old thread.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[skpatel]

Mr. Artisi,

Thanks for the information for the posting new question.

Your response for my same post in new thread will be highly appreciated and helpful to me.