tolerances for stagnated cap

[infallibile_GF]

Good morning, everyone. I have a mechanical piece, built in titanium, with a hole of diameter 20, which must be stopped hermetically, so that the water does not enter pressure of about 30bar. I need to stop it with a plug, also in titanium, which will be inserted to interference. according to you what hole-shaft tolerances should I use, to have a perfect stagnation?
Thank you all.

 

[MassiVonWeizen]

I imagine that it is not expected welding but the locking is given only by interference; 30 bars don't seem to me so I'd tell you that a h/r should be enough. for greater safety you could make a slight external excavation on the cap to let us slide the equivalent of titanium loctite

 

[falonef]

but is it a fixed cap?

did you also think about the use of gaskets?

 

[meccanicamg]

a nice screw cap with gasket? so it is removable.
use o-ring?
There will be regulations for pressure liquids. . .
If you put it in interference you have to calculate how much you need it and the temperatures for calettamento. I never worked with titanium so I don't know what to expect.

 

[infallibile_GF]

I imagine that it is not expected welding but the locking is given only by interference; 30 bars don't seem to me so I'd tell you that a h/r should be enough. for greater safety you could make a slight external excavation on the cap to let us slide the equivalent of titanium loctite

That's what I thought. the insertion to interference would be made instead of the welding, which gave us a lot of problems.

 

[infallibile_GF]

a nice screw cap with gasket? so it is removable.
use o-ring?
There will be regulations for pressure liquids. . .
If you put it in interference you have to calculate how much you need it and the temperatures for calettamento. I never worked with titanium so I don't know what to expect.

the stopper must be inamovable, even because once stopped, this piece must undergo other machining of turning to be brought to measure. welding is not possible because it is an actuator of a magnetic sensor, inside which a magnet is placed, that during welding we saw that, or for the heat of the same, or for the magnetic fields that are generated during the process, the magnet inside it is demagnetized, making the device useless.

 

[stevie]

hot or cold interference locking?
you have to calculate the friction force agent on the cap due to interference and verify that it is lower than the force applied by the pressure of 30 bar when the artifact goes into operation.

 

[infallibile_GF]

hot or cold interference locking?
you have to calculate the friction force agent on the cap due to interference and verify that it is lower than the force applied by the pressure of 30 bar when the artifact goes into operation.

Locking at room temperature. you could actually immerse the cap in the liquid nitrogen, but I do not have this possibility. for pressure I believe that it acts in a favorable way to lock to interference, the problem is that it must not enter the liquid inside the corked piece.

 

[meccanicamg]

Locking at room temperature. you could actually immerse the cap in the liquid nitrogen, but I do not have this possibility. for pressure I believe that it acts in a favorable way to lock to interference, the problem is that it must not enter the liquid inside the corked piece.

enough freezer to -18grade c and a warmer.

 

[MFT]

Locking at room temperature. you could actually immerse the cap in the liquid nitrogen, but I do not have this possibility. for pressure I believe that it acts in a favorable way to lock to interference, the problem is that it must not enter the liquid inside the corked piece.

just out of curiosity, but a koenig- expander cap isn't okay?

 

[infallibile_GF]

I have seen on the site of what it is and is not good for ever application, as I do not know if it exists in titanium and then it is too big. the cap I have to put on is a 20mm diameter disk, with a thickness of 2.5mm. must be taxably of these dimensions. the finished piece is a small float containing a magnet inside it. this float, being a component of a liquid flow measurement tool, must have very narrow dimensional tolerances and must also have a precise weight to the gram. that is why the use of titanium, as if it were in other material would not reach the desired weight, moreover the liquid in which it will work is hydrochloric acid and titanium resists well to corrosion.

 

[MFT]

I have seen on the site of what it is and is not good for ever application, as I do not know if it exists in titanium and then it is too big. the cap I have to put on is a 20mm diameter disk, with a thickness of 2.5mm. must be taxably of these dimensions. the finished piece is a small float containing a magnet inside it. this float, being a component of a liquid flow measurement tool, must have very narrow dimensional tolerances and must also have a precise weight to the gram. that is why the use of titanium, as if it were in other material would not reach the desired weight, moreover the liquid in which it will work is hydrochloric acid and titanium resists well to corrosion.

perfect was just a curiosity, since you never talked about size. I think that with 2.5 mm thick you have so little surface of support and interference that I fear a rather critical hold. .

 

[MassiVonWeizen]

at 20mm the h7/r7 interference is maximum +0.049 and minimum +0.007.It would seem a little. above all to the minimum, and perhaps a h7/s7 (+0.059/+0.014) would be better, but it is always a few cents. However, I imagine that everything is proportioned so the same coupling that at 200mm is has an average interference of about 0.1 has the same functionality at 20mm.
what I ask myself is that if it is a float from where the 30bars of pressure are born and if this pressure exists should be from outside to inside and therefore in favor of seal.
to prevent the cap being pushed into the inside by the pressure of the water just make a tiny shouldering that does as a stop.

a scheme of operation is always useful in connection with the request and its explanation

 

[infallibile_GF]

at 20mm the h7/r7 interference is maximum +0.049 and minimum +0.007.View attachment 72067It would seem a little. above all to the minimum, and perhaps a h7/s7 (+0.059/+0.014) would be better, but it is always a few cents. However, I imagine that everything is proportioned so the same coupling that at 200mm is has an average interference of about 0.1 has the same functionality at 20mm.
what I ask myself is that if it is a float from where the 30bars of pressure are born and if this pressure exists should be from outside to inside and therefore in favor of seal.
to prevent the cap being pushed into the inside by the pressure of the water just make a tiny shouldering that does as a stop.

a scheme of operation is always useful in connection with the request and its explanation

the float is inserted in a vertical tube in which the fluid flows, in this case hydrochloric acid. Depending on the amount of the fluid passing through the tube, the float is positioned at a certain height. the float contains a permanent magnet to the neodymium. when the float reaches a certain height on the tube is fixed a sensor that hears the magnet present in the gallegigator and snaps giving a signal. so it is clear that in that tube there may be a pressure of not knowing, but the specifications of the customer project say that it has to resist 30bar. the problem of the cap is not the fear that it can jump away, my fear is that the acid where the float is lost, can penetrate inside it by going to bribe the magnet, or going to weigh the float, which thus stands and will no longer give a correct measure of the flow. just a few grams to match the precision of the instrument

 

[MassiVonWeizen]

the problem of the stopper is not the fear that it can jump away, my fear is that the acid where the float is lost, can penetrate inside it going to corrupt the magnet

in this case more than interference will be to treat the roughness and geometry of the components.
In theory, an interfering coupling means that both surfaces are in full contact, but in practice the interference would be there even if one of the holes was slightly oval or had a 0.1 groove.
then put a cylindrical tolerance of 0.01 or less and a roughness of 0.02 or lower in order to have two identical "perfectly" cylinders and "perfectly" adherent surfaces.
I can assume that to work titanium you rely on a specialized company that has high precision machinery and that, always for the type of material used, costs do not have extreme relevance for the project.
as I have already mentioned before, although with different function, you can evaluate to perform on the cap a small excavation on the outer diameter in which to slide a veil of silicone asking information and advice to manufacturers of seals

 

[Marco F inox]

beyond the precarious seal given by the 2,5 mm thickness of the cylinder, are you sure that the considerable force necessary to insert it, do not deform in float?
I would think of a double fine thread with interposed brake fluid.

 

[MFT]

the float is inserted in a vertical tube in which the fluid flows, in this case hydrochloric acid. Depending on the amount of the fluid passing through the tube, the float is positioned at a certain height. the float contains a permanent magnet to the neodymium. when the float reaches a certain height on the tube is fixed a sensor that hears the magnet present in the gallegigator and snaps giving a signal. so it is clear that in that tube there may be a pressure of not knowing, but the specifications of the customer project say that it has to resist 30bar. the problem of the cap is not the fear that it can jump away, my fear is that the acid where the float is lost, can penetrate inside it by going to bribe the magnet, or going to weigh the float, which thus stands and will no longer give a correct measure of the flow. just a few grams to match the precision of the instrument

But if the magnet that I imagine can be a cylindrical pad, you can't incorporate it into the float by building it in two half and then weld them to tig?

 

[infallibile_GF]

already tried, but as I have already written, the welding process leads to the demagnetization of the magnet. I don't know if because of heat, or because of the magnetic fields that are generated during welding. titanium welding must always be done in oxygen-free atmosphere, otherwise it is oxidized.
cmq are now in place of the tests in production so soon I will know if the cap to interference works.

 

[Fabietto]

Hello, can I shoot you?
and hypothesize to cover the magnet? maybe covered in titanium nitride?
Okay, now don't shoot me.

 

[infallibile_GF]

Then I have to work the lathe. the float must have a precise shape of a cone with precise measurements and conicity to the cent. Moreover the surface must have a very low roughness and must be as smooth as possible, to avoid disturbances in the flow of the liquid, which could make the instrument unpredictable.