painting

why? Paint is usually an aesthetic coating as well as protective. Inside a pipe where none can see, all that is left is protective coating. Against what are you protecting the pipe innards?

corrosion and we must follow the drawing call out to the mil spec. aerospace application....

I am making the assumption that ID means Identification.

With that thought in mind I would recommend vinyl lettering or tags instead of paint.

Works well on paint or clean metal. Cheap, easy and can even be made inhouse or onsite.

Hi Tom,

It seems you have not understood the problem properly, read it again you will understand it. By the way referring to your comments on white man at bottom, are you the surviving Indian?.

Ok, my assumption was wrong, ID was not identification, it's inside diameter...but that's not what you are spraying, I'm assuming again, but the inside surface.

Have you thought of dipping the entire pipe, allowing to dry and then boring the paint out of the threads with a small wire wheel on a drill? Or you could try taping and/or coating the threads (petroleum jelly, perhaps, depending on the solvents used in the paint). It could then be washed and the edge lightly sanded to feather any paint edge.

If that's still not what you're trying to do, then please explain a little more verbosely

And no, I'm not an Indian, but I could see myself living in those much simpler times (but I get to take my computer :P )

If you are painting the Inside Diameter there are spray tips that will do this. Not knowing the reason for the application makes it difficult to help. Contact an automotive paint supplier. They should be able to point you in the right direction.

The openings at each end of the tubes are to small for normal tips. As I said the ends are about 1/4 opening. The application is called out by aerospace engineers and must be met to certain standards and painting them is the only way right now. We pour them now and it is labor intense and we end up having to clean the ends as well as no paint in allowed in the threads...

Can you make your own tip? Take a small dia tube of suitable length and seal the end (crimp, solder, braze, whatever). Drill small dia holes around the OD. Connect to an airless paint gun and give it a try. Do be careful with airless systems. The one I used would pump up to 1700 psi. It was capable of more but that is where we ran it. Is there a spec on the paint thickness? That could take some practice to maintain consistent desired thickness. Start out with the smallest holes you can make to try this. If more flow is required then slowly increase the size to suit your process. Controlling the holes sizes instead of the flow control on the paint gun will allow you to maintain pressure and flow at the tip. As for the no paint on threads, we would apply grease to fittings and threads to keep the paint from sticking. After the paint dried we removed it by wiping it off. The remaining grease would help prevent corrosion and lubricate the threads. Is that an option for you? Or make some plastic sleeves to press in to cover the threads. Remove while wet and give them a quick rinse to prevent build up. On second thought, Don't use the grease. It will rub off on the tube and could contaminate subsequent pipes and cause problems with the paint. Go with a sleeve or other method.

Mechanic

You have given me a couple of good ideas to try. Our openings are very small but possibley we could build our own tubes to deliver the paint. I also think we could make our own starting point each time so we only made contact with one end of the tube and then if we used your idea for the ends that would be even better.

Thank you

Apple

It is quite possible the materials of construction of the pipe and the fluid inside it are incompatible with each other. Choose another combination that doesn't need painting!

http://www.coleparmer.com/techinfo/chemcomp.asp

There is a low temperature melt-able plastic that is used to protect machining tools in transit. With a tray of this filled to sufficient depth, you could dip the threaded ends into it and allow to dry. After drying is complete, submerge the tubes into a 6" pipe sealed at the bottom, and filled with paint. Although the system would require a tall operations area, it would be an easy approach. If the outside needs to remain paint free, spiral wrap masking tape on it at some point after forming.

this may have solved half my problem,, thank you!

On thinking about it, it would be possible to protect the tube as described previously. Then suspend the tube into a wide, shallow container of paint. Apply suction to the top of the tube, drawing the paint up into the tube. Use clear plastic tubing to apply the suction. When visible in the plastic, stop the suction. Cut the plastic near the now painted metal tubing. This would allow the process to be completed in a building that is less tall, if that is a concern. Good luck.