Ways to measure elastomer swell

[AlexVY]

TL;DR Summary

Cost-effective ways to measure the swell of elastomers of submersible pumps after they are pulled from wells

Summary: Cost-effective ways to measure the swell of elastomers of submersible pumps after they are pulled from wells

Dear Physics Community!

I am working for an energy company and we are using progressive cavity pumps (PCPs) for producing water from our wells.
This is a youtube video showing how the pump is working:


The rotating part of the pump is called the rotor and the static part of the pump is called the stator.
The stator is made of a metal casing. Inside the stator has an elastomer, which is a rubber material.
Normally after some time, the elastomer swells due to reactions with the water, gas, and also due to higher pressures and temperatures in wells.

My question is, are there some cost-effective but still accurate ways to measure the internal diameter of the stator after we pull the pump to surface? I am thinking about some electronic tools which could be run inside the stator and measure its diameter with high accuracy and around the circumference.
This information will help me calculate the elastomer swell and possibly design a better pump (i.e. with different elastomer).

 

[anorlunda]

Since your question is about measuring inside diameter, it fits better under general engineering rather than materials, so I moved it.

I presume you mean that you can remove the rotor and insert an instrument instead.

Are you looking for a single number for the I.D. or a value for each axial cross section, or a 3D map of the surface?

 

[AlexVY]

Yes, the rotor is always removed.
A single number would not be useful. A 3D map would be perfect, but I am not sure how sophisticated the tool should be to to get the data for that.
It would be good to get >=12 measurements at every location of the stator (i.e. at 12 o'clock, at 1 o'clock, at 2 o'clock, etc.). Ideally the measurement locations should be distributed uniformly every 10-20 cm along the length of the stator (3-5 m).

 

[anorlunda]

ping @jrmichler, @Baluncore , @Dale Do we have any suggestions for how to do this measurement?

 

[Dale]

It all depends how much you want to spend. At the low end you could use a good pair of calipers. At the high end you could use a 3D ultrasound probe.

I probably would start with the calipers and try a measurement and see if you need something fancy. You may find that you don’t even need the multiple measurements you were describing.

 

[berkeman]

ping @jrmichler, @Baluncore , @Dale Do we have any suggestions for how to do this measurement?

Also ping @Ranger Mike -- he has a lot of experience in precision mechanical measurements.

 

[JBA]

The swelling you observe at the surface will not be a representation of the stator I.D. at its service pressure and temperature; nor, account for any wearing of the stator bore; so, you will not gain any valid information by your proposed procedure.
Evaluations to determine and/or verify the compatibility of and an elastomeric material under a given service condition are generally performed in a laboratory in small autoclave under controlled conditions with a sample of the elastomer immersed a sample of the service fluid and subjected to the expected field operating pressure and temperature conditions.

 

[jrmichler]

When we used progressive cavity pumps in the paper mill, we made no attempts to measure wear or swelling. When we saw signs of degradation, whether swelling or wear, we first decided if the degradation was normal wear. If not, we called the supplier, with full details of the service (material pumped, pressure, RPM), then let the supplier recommend replacement materials.

Most of our problems were wear because we mostly used these pumps for pumping water based slurries at relatively high pressure and low flow.

My hazy recollection of the inside of the stator is that measuring swelling would be difficult because:
1) The shape is such that getting an accurate measurement is difficult, and
2) It takes only a very small amount of swelling to significantly increase the power requirement.

You might be better off to just run the pumps until the power required increases by a predetermined amount. Then send a used stator to the pump manufacturer, and ask for a recommendation. That's what I would have done, and would do.

 

[AlexVY]

Thank you all for the great comments!
We are actually doing some lab testing and sending some pumps to the manufacturers for a more detailed analysis. The difficult part is that although the lab tests are done at realistic conditions, still we do them only at specific pressure and temperature and only for a certain duration. Also, we can do them only with a limited amount of fluid samples. Otherwise the cost of the tests would be too high.
I was thinking that if somehow we could extract the useful information about the swell from the remaining pumps it would complement the available lab data and pump inspection results.
And yes, this is true that the remaining swell at surface will be different from the downhole swell. At the same time I did not want to discard this approach before obtaining some data.