I haven't done this before, but I know the procedure 'in theory'. Does anyone know of any good on-line resources regarding installing mechanical seals _successfully_? This seal costs over $2000, and I don't want to have to try again with a new seal.
My understanding is that rule #1 is don't touch the seal surface, rule #2 is don't touch the seal surface, and on down the line until you get to about rule #30 which is to take your time and work as clean as you possibly can.
Does that about say what needs to be said, or can we improve on that?

Do you implement duty/standby operating mode?

Mech seals will only work well if everything else works well such as balancing and alignment.

What type of mech seal is it?

Duty/Standby? Not really. This seal is in a rotary union which is an absolutely mandatory piece of the puzzle in a large-ish process line. The union runs 24 hours a day (less downtime for breakdowns, rare, and set-up, which averages perhaps an hour every other day). It runs five days a week, and is down for weekends.
The rotary union in question is in a hot-oil roller. I'm not sure what kind of seal it is, but I _believe_ that it has at least one half of the seal made out of carbon (just based on some observations without taking the union apart).
The union is lubricated by the oil that is flowing through it. The union has worked well enough for a couple of years now, but it has started getting an intermittent leak which makes me think that a bit of crud got in there and buggered the seal surfaces, and when the scratch happens to line up on each face it drips. If the scratches are lined up when the machine is shut down then I've got a pool of oil on the floor in the morning, otherwise it just drips now and then and it's not a problem.

It looks like your production cycle i.e run over week days and shutdown during weekends gives the mechanical seal an intermittent operations. But it can run for a couple of years. So it's good.

What brand is it then?

The rotary union is a Deublin H67.

http://www.deublin.com/products/operating_data.asp?SERI...am+and+Hot+Oil+Union

Hi Mike,

You could do worse than checking out this site:

www.mcnallyinstitute.com/

This has a wealth of information regarding seals and pumps. Including installation, operation and trouble shooting.

Good luck

Here's my two cents worth... I've dealt with quite a few Deublins over the years, though not this particular type. Typically, you have two pieces; one static, the other rotating. One is ceramic, the other carbon. One is spring-loaded, the other fixed. The spring-loaded half "floats" and locates to the fixed half to optimize face surface contact. Yes, each of these surfaces needs to remain as clean as possible. The ingression of foreign material will damage the contact surface and cause it to leak. I agree, it sounds like your problem. Also, they should never be run "dry" for any length of time. The fluid acts as a lubricant between the two surfaces. The rotating mechanics obviously must be sound, but because this coupling is self-supported, I would imagine that balance, alignment, etc. would be more of a long-term reliability issue (although it could become a short-term issue depending on speed). I hope some of this helps!

Hello Mike,

Certainly one should take particular care to work in a clean environment in any application involving a mechanical seal. It is good to avoid touching the seal, however an accidental touch of the face should not cause the seal to fail. After all it is flushed with oil so a little oil from the finger tips would not cause failure. Since your existing seal has lasted ~2 years without trouble, it sounds like you do not have any operational problems. The life of any seal is dependent on accurate alignment and dynamic balance of the rotating part to the stationary. When installing this seal extra precaution should be taken to minimize axial play (end float). Bottom line, keep cleanliness at high standards, adjust radial, angular, axial alignment and coupling runout to close tolerances and make sure the rotating part is dynamically balanced. This should maximize the life of your union seal.

quote:

Originally posted by Wise Old Owl:
After all it is flushed with oil so a little oil from the finger tips would not cause failure.

I'd be more worried about the acids from my finger (i.e. sweat). I can rust ferrous metal seemingly by just _looking_ at it.

quote:

dependent on accurate alignment and dynamic balance of the rotating part to the stationary.

In the case of this rotary union the rotational speed is perhaps 12 rpm, so perhaps balancing isn't a big deal in this case, but I can certainly see how it would matter in the case of a vacuum pump, for instance.

Dear Mike,

About your problem, this type of rotary joint normally it will leak after 2-5yrs. It depend upon the operating condition (rpm and Hot Oil condition).
For your case, i think the hot oil cleanness is more important than the installation of the mechanical seal.As your current seal normally is a component seal the setting is depending upon single or multi-spring design. this due to the compression ratio is different.

Mike,

Do you send out the used seal for failure anlysis to see whether dirt really scratched the faces as you mentioned above or just simply worn out?

The borchure says it has a seal wear indicator to allow preventive maintenance, hasn't it?

quote:

Originally posted by GT-X2:
Dear Mike,

About your problem, this type of rotary joint normally it will leak after 2-5yrs.

Okay. I guess I'm on the short end of that, but I guess if it's going to cost us $3K to replace every few years then that's the cost and there's no point in complaining about it.

quote:

For your case, i think the hot oil cleanness is more important than the installation of the mechanical seal.

I will think about this. I'm not sure, now, how fine a filter there is in this system. Maybe I should add another one.

quote:

Originally posted by Josh:
Mike,

Do you send out the used seal for failure anlysis to see whether dirt really scratched the faces as you mentioned above or just simply worn out?

It's still attached to the machine at this point.

quote:

The borchure says it has a seal wear indicator to allow preventive maintenance, hasn't it?

That's what the brochure says... I haven't seen anything on it that looks like a wear indicator, but I haven't been able to find the manual for it, so maybe I'm missing something.

The seal and all flush piping must be checked and installed as needed prior to starting the pump,the life of the mechanical seal depends on various factors such as cleanliness of the liquid handled and its lubricating properties,and never operate the pump without liquid supplied to mechanical seal.Running a mechanical seal dry,even for a few seconds, can cause seal damage and must be avoided.Physical injury can occur if mechanical seal fails.

Dear Mike,

quote:

Okay. I guess I'm on the short end of that, but I guess if it's going to cost us $3K to replace every few years then that's the cost and there's no point in complaining about it.

The seal life 2 to 5yrs is not no point to discuss. If we have trouble we need to discuss. So, we can understand the seal problem and the life expected.
As current mechanical seal manufacturer, they normally can warranty the seal for 1 yrs only (for seal damaged due to manufacturing defect).
From my experience, the rotary joint seal maximum life is about 7yrs. Only if the operation condition can keep in good condition as mention by Jun. 2 to 5 yrs is very common, because the operating condition sometime good and sometime bad (i.e. speed changing,hot oil condition,vibration,etc)
Normal mechanical seal damaged is due to human error and bad operating condition.
However, since the stationary/rotating seal face is a carbon material, the seal life is reduced.
If you expect to run the seal for longer time, the seal face material need to change.
But in this rotary seal design, normally carbon is more preferable than silicon carbide or tungsten carbide(for 1 of the seal face). This mainly due to the operation of your machine.
For more information of the seal face material selection, i think you better seek the manufacturer advice whether they can change the material or not or for better solutions.
Take care.