mud drilling equipments

[jaydev choudhary]

Big oil & gas giants are involved in mud drilling processes throughout the world. they use equipments like mud drilling motors, mwd, rotors, pumps etc. for drilling purposes. these parts while drilling in depths are subject of high corrosion and wears. with thermal spray coatings has wide variety of scopes in this drilling field. in fact few firms like bodycot are into coating of these mud drilling rotors against corrosion & wears.

if anybudy having any related details of coating of these rotors please share.

here i am also attaching photo of that drilling rotor for better understanding.

[pulaunias]

Are these components hard to polish, as they are not that regular (simple cylinders, or flat surfaces) in shape?

I heard from a colleague in a HVOF lab that they ever worked with a firm on coating glass molds with WC/Co for high temperature anti-corrosion purposes, but ended up with finding the coated molds were hard to polish (less regular in shape) so the project failed.

Appreciate if others can input any information.

[jaydev choudhary]

Can't say anything about polishing this component but as per my knowledge there won't be any such problem. i am looking for some technical guidance about coating of these drilling equipments.

[djewell]

Coating progressive cavity pump rotors is pretty easy. Place the rotor in a lathe and spray a little bit off center to get a uniform coating thickness. The hard part is polishing the finished rotor. A belt grinder cannot put enough pressure on the coating to cut it, even with a diamond belt. If you can solve that problem, let us know. You will make a lot of people very happy.

[jaydev choudhary]

djwell, thanks for your valuable contribution. Before grinding we are perceiving one more problem which may occur after coating. as these rotors are used in depths of land for drilling purpose, and suppose we make its surface hard with WC composition by thermal spray process and as these rotors perform under a higher impact i.e. usually motors holding these rotors runs between 1000-3000 Horse power.

so thermal sprayed coating may peel out or may flakes off due to such higher impacts. please suggest if you have anything related informations.

[djewell]

I was not aware that these rotors see a high impact, as they run inside an elastomer stator. WC is a hard, brittle material, so no matter what you do, it could crack or chip if it experiences a direct impact. Flaking and peeling are often due to the application process and how cracks propagate through the coating. Peeling occurs because the bond between layers in the coating is weaker than the bond between particles in the same layer. When a crack occurs, it propagates along the layer and peels the coating off. HVAF coatings have excellent bond strength between layers, so when a crack occurs, it cannot peel layers off, and the coating remains in place.

If the coating is pretty thin, it can flex with the substrate metal. Over time, the coating could fatigue and come off, depending on the application process. HVAF coatings are good in fatigue applications because they do not fail prematurely. WC is an excellent material to protect PC pump rotors, and several pump manufacturers offer WC coated rotors.

I have had excellent results with hard metal coatings in down-hole oil drilling applications. The metal is not brittle and can withstand severe impact even at 3 mm+ thickness.

[kenwolf]

We can polish both new and used progressive cavity rotors. We designed our own polishing equipment some time ago.

(07-29-2010 09:22 PM)djewell Wrote:  Coating progressive cavity pump rotors is pretty easy. Place the rotor in a lathe and spray a little bit off center to get a uniform coating thickness. The hard part is polishing the finished rotor. A belt grinder cannot put enough pressure on the coating to cut it, even with a diamond belt. If you can solve that problem, let us know. You will make a lot of people very happy.

[jaydev choudhary]

Though these rotors are cylindrical. but these are not regular cylinders, grooves are there throughout the body of these rotors, so putting these in lathe and coating while rotating does not seems easy. A uniform coating thickness can not be expected.

And impact is there though it is not striking impact like hammer shots but as these rotors moves inside the earth and rotate to drill it like a screw, so sand particles, stones, metal pieces etc. may come in the way of these rotors while drilling so its very important to maintain a hardness of the surface to combat with these and also we need to take care of a stronger bond strength between surface and coating. because with thermal spray only mechanical bonding can be formed which may not be much stronger in such drilling conditions.

Please suggest.

[Stuart Milton]

I can't go into any detail as the information is not proprietary to me or my company. However, I can confirm that it is done successfully with HVOF WC coatings and they are polished. Just thought that it may help to know that you are not chasing the Holy Grail

[djewell]

I know several companies using both HVOF and HVAF to spray WC coatings on down-hole pumps and motors. Their business is growing because the coatings work.

[Stephen Booth]

(03-01-2011 11:45 AM)Stuart Milton Wrote:  I can't go into any detail as the information is not proprietary to me or my company. However, I can confirm that it is done successfully with HVOF WC coatings and they are polished. Just thought that it may help to know that you are not chasing the Holy Grail

I second what Stuart says, these components are done on a regular basis around the world using HVOF and a WC material. Typically the OEM will also apply special sealant or top coat. Chrome plating has been used for many years before this. Technically challenging, but not impossible.

However, I think your biggest challenge will be getting OEM support for the repair, so that the End USER or Rental company will accept your coating.

In many cases customers will require inspection to a DS-1 standard before they will accept it in the field. Of course I am speaking of the multi national drilling rental companies. A local company might be really keen on a lower cost option, and I am sure you can develop this readily.

Grinding (or rather blending and polishing) is a challenge, and several approaches can be used, but usually require plenty of manual labor.