teflon bushing on ss shaft

Is this teflon sleeve used on the shaft of a centrifugal pump at stuffing box area?

we are using teflon insteed of mechanical seal in lobe pump

is it related to coefficient of friction

This pump is used for 'soap solution', right? Do you use a lobe pump for this or it a screw pump?

Any way, "instead of mechanical seal" you are using this. Are you using 'gland packing rope' over this teflon sleeve?

No we are not using any gland packing

lobe pump we are using for soap transfer

we are using teflon ring in housing and it fitted like oil seal

mechanical seal solve the problem of axial as well as radial leakage

but now people are just using there own theory with wrong concept to save mechanical seal cost

my curiosity is how come teflon makes the stainless steel to get worn out

shaft is ss 304

there is no way to understand which grade of teflon we are getting in kenya. it is difficult to get resources in kenya.

Which stainless steel you used in shagt?

And also Teflon bushing?

A pure teflon bushing should not cause wear to a 304ss shaft - unless the teflon is filled with an abrasive material, or there is abrasive in the fluid you are trying to seal. Abrasive in the fluid can become imbedded in the teflon and cause the shaft to wear. Suggest you examine both the fluid and the teflon closely for filler material (hard particles). Teflon bushing may cold flow under mechanical stress. This will increase the clearance to the shaft, but the wear should be in the teflon bushing.

Using teflon bush in place of gland packing for a pump is not correct, it can not replace gland packing or mechanical seal.

Teflon bush can be used as bearing, but pure teflon wears very fast as beatring. The teflon is filled with glass, graphite or bronze depending on the application to be used as bearing bush, but ball bearings are always advisable. The glass filled teflon bush is supposed to last 500 times better than pure teflon.

Teflon bush(with glass filling etc) can be used if you can not use ball bearings in corrosive or abrasive environment.

A supplier of mine asked me once:"what's that you call "hardness"?because we changed the bronz bushes by teflon in the automatic saw and it wasted the steel so which one is harder?".That's the truth.Believe or not the experience told above is correct,dont look for mistakes.-

As many said above, using Teflon as a hollow ring may not serve the purpose. Teflon has a very high degree of coefficient of expansion. As many said, the filling in these materials like glass filling and metal filling or the grids from the process fluid stay/embed into it. The fillings and the grids grind the shaft and are accelerated by expansion (towards the shaft).

Nevertheless well-engineered Teflon (PTFE) rings for these purposes are in practice for long time.

Basically there are two types: Lip Seals and Segmented Rings.

Lip Seals: More popular as 'V-Rings' or Chevron Rings.

On tightening the gland follower (or spring loaded), these rings expand radically and seal the leaking passages.

This type is more used for reciprocating elements like plungers and for valve spindles.

These ring come in many materials besides Teflon and with different fillings. The following sites are a few to give more understandings of this type:

www.veepacking.com, www.ycindustries.com, www.jaderubber.com, www.freepatentsonline.com, www.kpbptpn.co.id, www.johnsonpackings.com

Segmented Rings: Some time referred as 'tangential and radial cut rings'.

As the shaft wears, the segments close the gaps by an annular (grater Spring) spring as shown in the figure.

They come in many designs to suit to different applications.

These types of rings are mostly used for rotating shafts of steam turbines and in reciprocating compressors.

Using these types of rings in lobe pump shaft is subjective. The standard practice is to use 'gland packing arrangement or mechanical seal'.

But occasionally, maintainers are forced to deviate the standard practices due to reasons like availability of proper materials and proper skills, cost, etc. It is we maintainers to provide an immediate/temporary solution to a demanding contest and constantly look for getting back to standard practices.

But when we take such temporary solutions we should bear in mind of the HSE issues. If you succeed, you are doing your duty. But if you fail (especially in HSE related issues), the deviations from 'standard practices and standard procedures' will be critically commented and some times even punished. Take care…

Hallo yesyen

what is this HSE issues?

i like your bio - a picture worth thousand words, needless to say if it is annimated.

please tell me how you are doing this annimation in which software.

HSE: Health, Safety and Environment...

Is our desire technology be driven for rules so clear like gemetricals principles,as euclidean principles , rules the entire geometry, then just silogisms,pure logics, etc...But if you see coupple days ago an engineer was asking about pinion starter motors material cheaper and close to its originally was used:If you see some answers you discover this kind of tech we talk about is not completely developed.In every engineering office for mantainance for foraign machines are making new experiences whiches are repeated in somewhere else,in space and along time too.Seems rules were not writen as clearly...

Just for telling experiences i think seals systems becomes superior to the hydraulics like the speed regulators to the injection fuel pumps, or logic to the electronis,or equally ridiculous in costs matters cases for electronics devices to electronics circuits inside.

Here some complexity about:common sintetic seals for shafts superior in temperature skills under grease or oil enviroment are inferior to common sintetic rubber for shaft seals when you use them for gas-oil fuel.May be after years working in hydraulics you will discover under speed considerations the greatest for all matter poliuretano (¿polyurethane?) is no as good as others inferior plastics.In other plan of considerations i should avoid the nice teflon in seals systems.

I saw in tork converters Clark trademark, rings what seems made for some platics or iron powder. Do you have some information about that material?

Teflon bushings are almost aways machined or molded from a Teflon / glass bead mixture.

It is highly likely that the glass beads are abrading the shaft. It is also impossible for teflon to abrade a steel shaft. Teflon is one of the softest, non-abrasive plastic materials.

Teflon pump packings are usually made from expanded PTFE...PTFE is the generic name for Teflon....expanded PTFE is usually braided to form pump packing materials . the braided material will be in a "rope" form....

Expanded PTFE will be pure PTFE with no fillers, but I dont see how you could replace a machined bushing with a packing material.

perhaps you could use a bushing machined from PTFE with a less abrasive filler such as Graphite