is the oil seal same for linear motion and rotating motion shaft?

If I were you, I would contact National, or CR. They will have some questions for you.

Welcome to the site.

already contact, the solution is change the seal again. Those oil seals are send by them.

You have alreadu posted the question in earlier thread, so repetition was not necessary. We do answer guests hence the repetion of post was unnecessary. In fact your query was answered there a) Rotary and linear seals are different b) The double lip seal is may be for rotary or linear motion c) Check the company catalogues for the type of application

juz to confirm for ans b) double lip seal may used for rotary or linear motion. what i mean for my case is the seal itself is station but the shaft is moving, will this make different?

i checked with the original manufacturer of the pump and seal, the catalogues did mention some application but never mention is it suitable or not.

Most of the linear (or at least more than half) is when the shaft is moving. (and any way it is the relative motion you know at the lips)

Contact or check the brochure whether the particular doublle lips are for the linear motion or not. Send a mail to them, they will respond. Wou may get an alternate seal in case it is not.

contact the supplier of the equipment, they advice to change to new seals again n again, the problem can't solve even though they send their representative to change the seals.

my concern is will this cause by design problem and i wish to know the real root cause, just for my own good.

Thanks

there are teflon " packings" that can be added in the o'ring gland...it sounds as though when rebuild sometime that the shaft seals. have , either no teflon packing installed, or they may be in the incorrect sequence ,allowing the fluid to bypass the seal on every actuation of the piston arm..

The friction to the shaft will cause the temperature increasing if the teflon packings are installed, that is the reason no packings being used. Besides, the pressure in the crankcase is around 30psi and the revolution of the crankshaft of the piston/plunger is around 500RPM.

Oil Seals are not suitable for linear motion shafts, these are suitbale for rotary applications. You need to go for different type of seals like spring energized seals. Please refer BAL Seals catalogs , you will get ample solutions.

Thanks,

Ashok

Pune/ India

susas.punde0@gmail.com

You have provided no details for us to work with. But hear is a start. Try to find a leather seal, instead of a rubber compound. They should last longer in a linear motion. O rings will work in almost all sealing applications, provided you use the correct compound. But we can't help with that because you provided no details.

With less details provided, we presume you are to seal liquid.

Chevron/ v'packing are one of the bests to contain liquid.

There are many standard manufactures for this type of seal sets. John Crane is a pioneer to whom you may try by giving the relevant dimensions like shaft dia, housing dia, housing depth etc.

seal the oil, max pressure 30psi. the moving of the cranshaft which attached (driven) these 3 shafts is 500rpm. "V" packing is good for the great pressure but not this, it will create heat to the shaft due to the friction.

Maybe the reasons the seals are failing is because of the a)type of lubrication is wrong, or b) the lubrication does not exist or c) that the environment is too dirty (you may need some bellows to protect the area of the shaft that moves in and out....)

Just some thoughts......

Hi there, Am called Bwankya Andrew and i have a hint on seals normally what we do here in africa is to go with that old seal to people who sell them and get a similler one and fix it. It will work. Please let me know.

thanks for the advice. this is the new pump, the seal leaked aft the pump 1st time start, so we tgt the new seal may leaked, but after run more n it leaked more, so we consult the supplier and there advice us to change to new seal. but leak again so they send us other type of seal n we change it n leak again.

we brought the seal manufacturer for well known company to investigate on this issues and they custom make us the seal they think is the best but leak too.

the supplier of the pump send their enigneer here and he got no idea also.

There is a preferred orientation to many seals. If the one you were sent as original equipment was installed backwards and you installed the following ones with the same orientation then this may account for your experience.

The lip of the seal will point in the direction of the oil pressure when correctly oriented.

Sincerely,

Mr. gee

thanks.

the orientation of the seal had been checked, confirmed with manufacturer and the drawing, no problem for that

1. Since it is a new pump (unlike what I thought) it is purely OEM responsibility. Let him sort out. Already you have taken quite a bit of initiative by calling the seal manufacturer.

2. Usually seals run on a particular contact pressure- more faster wear out, less= leakage. In your case it may not be the case since your case even a seal mfr has associated.

3. Try to identify the leakage position. A few times we thought it is from the lip, but actually it was from OD (happens if the housing tolerances are not maintained)

4. If it is a split seal, leakages may happen from split line.

5. Though it is not your baby, ask for a seal type change - mechanical or gland sealing. Let the OEM design and give you.

The leakage is not from OD, it is very obvious from the ID.

Supplier of the pump will send engineer again, just wait n see what is his opinion.

You have not given enough information to make a judgment on your shaft seals. Though you checked the shaft for scrapes and digs you do not state that it was checked for roundness and truth. However on linear shafts the wiper is sometimes confused with the seal which is buried in the piston end inside the housing. You make no comment on checking the housing for truth (straightness) or roundness. Linear motion shafts with seals are usually hydraulic with great pressure in them. O rings qualify as a seal for high pressure Not the Chicago Rawhide rotating shaft seal that you describe. Some electric linear motion shafts have oil seals to retain a small amount of lubricant for the shaft. What type of equipment is this shaft controlling?

These linear motion shafts are used as output shaft of the pump to charge up the hydraulic pressure, the pressure able to charge up and no problem for the flow rate as well. In short, in the oil & gas field this type of pump is very common, just nobody aware the leakaga open the cover and checked it or till the pump damaged due to lacking of oil.

All 6pcs shafts had been checked and no scoring, nicks or cuts were found. Also, the alignment, straightness and roundness of the shafts had been checked as well, all these shafts are new and the pumps are 1st time using.

For addition, it is about 30psi at the crankcase while the pump running, therefore i believed the CR seal should be able to withstand the pressure.The manufacturer and tech support reply and recomend to use other 2 types of seal, but all the seals are interchaneable while i checked it online. i brought up this issue to supplier but they seems no answer.

I agree with some of the other posts. We need more info on your specific application. Are there chemicals involved, if so what are they. Whats the speed of rotation or linear motion? What are the materials the seals are made of? Whats the shaft made of? Is it of a porous material? I personally use Viton single or double lip seals with bi-directional helix in all or most of the rotary vane vacuum pumps. Other times I use Teflon seals or Mechanical seals or Labyrinth seals, depending on the application. Sometimes just an o-ring is good. On older equipment we use hand cut buna seals or leather seals. No accurate answer can be given with allot more info.

a pump which consists 3 shafts, driven by a elect motor and the output of the shafts will charge up the hydraulic pressure to the hydraulic system. The shafts are linear motion and the speed is 500rpm for the crankshaft which connected to the shafts and submersed in the crankcase oil, the max pressure for the crankcase oil-pressure side of the seal is 30psi.

we are running 2 pumps at a time, so there will be 6 shafts. All these shafts and pumps are new.

The material of shaft is stainless steel

You need a teflon v seal. this will create heat but the stainless steal should prevent any scoring on the shafts depending on how hard it is. The type of fluid and heat generated will tell you which seal you should use. From my experience if you bought the pump and it was leaking after a small amount of use then you should by a better quality of pump. Just my opinion. Good luck.

Oh if your in Canada call Canadian Bearing and they should be able to set you up with the right thing.

Use a CR 12446. It is the same seal as the CR 12458, but with a long life designed seal material.

no chance for me to change it because the equipment (oil rig) already handover to other party (owner) few hours ago today and dont know what their decision yet. But I won't onboard anymore due to our charge (daily rate) too high.

Correct I looked up the Numbers you provided and came to the same conclusion These are rotory seals. You may wish to consult a local bearing shop in your area. Eastern Bearings works for me I have no Idea of your locality. You may also find McMaster carr (industrial catalog) very informational. There online catalog is more comprehensive then the ones they deliver. You did not mention the type of equipment, Pressures, cv rate (constant velocity) or anything else for that matter.

This part # you gave is also a press in seal. Does it need to be? can it be held captive in another manner if need be? I'm not a bearing specialist but I've not previously witnessed the use of a press in seal for liniar purposes. Perhaps it may be that all liniar shafts I've worked on where hydraulic.

I have seen a lot of talk about seals here and no one has answered the question as to rotary and linear seals. Yes rotary and linear seals are different. Typical linear seals are "u" seals, loaded U seals, teflon loaded square seals and many more. Rotary seals are the "CR", National, TCM, NSK are manufactures of rotary shaft seals up to about 25 PSI. There are some"BABSL" seals availible upto 150 psi. Also some company's rotary saels are dual function.

Mike,

I agree with you that the seals are different and that most rotary shaft seals are not designed for pressures (35 PSI ) that the writer is discussing. For this purpose special seals like you discuss and solid reverse land pump seals like Impro seals would be used in this application. However, as a generating power plant engineer and as my experience with Westinghouse erecting large steam turbines, My first call would be to the pump manufacturer that sold me the pumps for that specific purpose and tell him to fix the problem. Though the writer has tried to explain the problem I'm not smart enough to understand if the rotating pump motor and shaft to the pump is the problem or if the pump is a positive displacement pump with pistons with "linear shafts" as in round rods protruding the rotating element are going into a block which produces the strong hydraulic forces. In any event the owner has dismissed this company and hired someone else to fix the problem.

so can i say the manufacturer using the wrong seal? the three types of seals (CR12458, National 471766 and National 410163) which they are using now are rotary seal but the shaft is linear movement. but when i ask them n they told me thier R&D tested n proven.

Hello Mike,

These are two very different applications in terms of seal engineering. Rotary seals concentrate on one very small dynamic area. Rotary seals can generate a significant amount of heat since the dynamic motion is concentrated on one area. The surface finish of the rotary dynamic sealing area also tends to become more polished and therefore more seal friendly in a shorter time. Rods that extend and retract can act like a cheese grater to a seal as it goes back and forth.

So in the end, the better choice for a rod seal material may not be elastomeric. PTFE blends that contain higher amounts of fillers make seal materials that are more resistant to heat generation and better able to resist wear. These seals can handle reciprocating, rotary and oscillatory motion.

The trade off is that PTFE has no memory, so you have to energize it in order for the seal to maintain contact with the sealing surface. However this is readily achieved by using either an elastomeric or metallic spring energizer.

You can see a movie of what one of these metal spring energized seals looks like here: http://www.facebook.com/video/video.php?v=427120070517

Here is a pdf to a spring energized seal catalog c/w engineering details in terms of surface finish recommendations and hardware design: http://bit.ly/bttVbA

Finally here is a link to an Oil Seal video: http://www.facebook.com/video/video.php?v=427096155517

From your comments, I think you might want to consider a PTFE Flanged seal energized by a metallic spring.

Hope that helps.

Take care.

Welcome to the insanity.

That was an excellent answer, but unfortunately, the post is fairly old, and may be dead by now. But do hang on and enjoy the ride.

for rotating and linear motion seals are different just check the din standard seal for it

wel you can try with tangentially cut oil seal rings..

Is there a similar pump that is sold by the same company that you can research the seal design on?

yes, National sell the similar pump, but they are now all under one company.

In fact the manufacturer send a representative here this morning and he mentioned that the model/brand of this pump always complaint by customer about the leakage, and he agreed that all the seals which i mentioned before are for rotating shaft.

the latest news for the pumps which having leakage problem that i handled last week was solved, the manufacturer added in another seal which mean installed with 2 seals facing crankcase side to prevent the oil leak. they agreed that the design might have problem and their R&D still looking for the better solution.

This following massage is taken from public domain to emphasize the impotence of O-ring and elastomers.

The Space Shuttle Challenger was destroyed 73 seconds after takeoff due on January 28, 1986 due to a faulty O-ring. It failed to seal one of the joints, allowing pressurized gas to reach the outside. This in turn caused the external tank to dump its payload of liquid hydrogen causing a massive explosion. The cost of replacing the Space Shuttle was $2 billion in 1986 ($4.5 billion in today's dollars). The cost of investigation, problem correction, and replacement of lost equipment cost $450 million from 1986-1987 ($1 Billion in today's dollars).

In you assembly you have so many O-rings and lip seals. These are likely to get damaged/cracked if equipment is not in use and under maintenance if not well preserved.

You definitely require the support of the OEM, failing which you are in deep problem. You may try the following steps:

1. Locate an experienced mechanic/technician familiar with hydraulic pumps and components.

2. With the help of the drawing (the pdf that you downloaded), salvage and cannibalize one complete set.

3 For doubted O-rings, replace with new rings. Standard O-ring kit with various sized rings might help.

4. Locate local rubber components manufacturer/supplier for lip seals and other non-standard components.

5. Assemble one set and test.

6. Good luck.