Hello all! Many years since my last visit. Nice to see you all active in it.
I have a problem with hydraulic pumps vibrations. 2 or more all linked in a row. I suspected bad machining on the flanges and it was verified. up to 10 mils of excentricity and 5 mils in angular.
In my mind, it can't produce a good running. Do you have specs on what it should be? I think 1 or 2 mils maximum should not be exceeded in both readings.

When you speak of flanges - do you mean pipe flanges? Common piping header I assume.

You kind of imply alignment; but piping or shaft-to-shaft?

The way you have worded it, I take it as piping misalignment.

Please indicate.

Hello Sam!
No piping flange but the C-flange where the mounting bolts to the bell housing are attached and the flanges where they bolts to one another when mounted in a row.
In the last case, the coupling is a splined sleeve that does'nt permit much and I fear it creates a very strong stress ont the pump shafts. Enough to create a deflexion and thus induce a rubbing action on the vane barel inside the pump.
In case of a piston pump, it just shortens the life of the bearings greatly.
Yvan

No distance piece?

Time for re-machining or need a quick fix. Regardless, document.

10 mil is too excessive regardless of type of coupling as angular is way out too.

Quick fix is to raise the motor above the rabbet fit (boss fit). Enough axial float? This will enable to correct for parallel and angular by shimming.

If you can machine; then take the time to align basically perfectly and then dowel in position with two dowels.

Tolerance is 80% of clearance in coupling and bearings - not additive. 80% of the smallest.

From NEMA MG-1 (2003)

"4.12 TOLERANCES FOR TYPE C FACE MOUNTING AND TYPE D FLANGE MOUNTING MOTORS - For Type C face-mounting and Type D flange-mounting motors, the tolerance on the mounting rabbet diameter, the maximum face runout, and the maximum eccentricity of the mounting rabbet shall be as in Table 4-5 when measured in accordance with 4.11."

Table 4-5 provides limits for runout, eccentricity etc of mounting rabbbit based on dimension "AK".

Table 4-1 tells us what "AK" means: "Diameter of male or female pilot on face, flange, or base of machine"

For AK < 12" (I assume this includes your machine?), Table 4-5 gives the limits as:

AK dimension tolerance: +0.000" / -0.003"
Maximum face runout: 0.004"
Maximum permissible eccentricity of mounting rabbet: 0.004"

This is for new motors, the dimensions of the rabbet on the motor. I assume similar would apply to the other components.

Linked below is a photo of the hydraulic pump at our plant. Ours is a 40hp, 1800 rpm, horizontal, face-mounted, piston type hydraulic pump. I guess we call that a "spacer" between the motor face and pump face (correct?). Does yours look similar? I've forgotten the difference between the terms "face" and "flange" is when applied to this type mounting. Something to do with how the thing is bolted. Does anyone know? (I apologize if I used the terms wrong).
http://home.comcast.net/~elect...anceforums/cface.jpg

This message has been edited. Last edited by: electricpete,

Yes, the principle is the same, only I deal with motors up to 250HP linked to groups of 2, 3, 4 and even 5 pumps all attached together. Sometimes I have 2 pumps on one side and 3 or 4 on the other side of the motor (2 shafts motor). A very popular combination on plastic injection presses.

You can imagine that with these machining errors, a great deal of vibrations is generated in these assembly.

Some pumps are running good and other are just destrying themselves with the consequences that when they break, everything around them also breaks.

I know that this the source of the problem. What I need is to prove it, not to blast the manufacturer, but to force him to review his machining process in order to eliminate the cause of all this.

Therefore, I need specs to prove my point because they will act reluctantly if they ever accept their fault.

It is impossible to get this information from them. They keep it all secret, as if I was going into the hydraulic pumps business.

I'm sure I'm not the only one with this problem, although not everyone is aware of it, taking for granted that pump manufacturer are very precise in their production process.

But all the same, I'm willing to keep you guys posted on the follow up of this adventure and transmit the knowledge I've acquired and to acquire in the future.

Thanks for the help!

Yvan

Regardless, common sense will tell you - you cannot take-up more than 80% of the bearings clearance else you will have trouble. If you go to zero you are at a bad limit with no remaining clearance nor forgivness when other elements kick-in. Can your motor freely move or is it affected by thermals?

If your bearing has 3 mils total clearance; then, 1.5 diametrical X .8. That is what I use and generally no trouble.

Hello All !

I'm back with my follow up on hydraulic pumps that had machining problems out of specs. (24th november 2008).

I said I would keep you up to daye on the subject.

First, I want to thank ElectricPete and Sam Pickens for their input.

Here is what happened:

My client did not want to pursue in this line of measurements and solution. He did not want to argue or fight with his suppliers. That was his choice. We do not collaborate anymore. That his also his choice. I know that to this day, he still lives with this problem and it is costing him dearly.

I have other clients with similar machines and production. I have diagnosed the same type of machining errors in his layout. He checked them and found the motors and bell housings to be out of specs.

He had them rebuilt and machined and what was the outcome ?

The vibrations dissapered and the hydraulic groups are running within normal amplitudes again.

ElectricPete told me to check the NEMA specs and I did. I transmitted them to my clients. The one who made the check-up and had the parts brought to near zero in angularity and excentricity fixed his problem.

Now, whenever he will take off a group of pumps, he will check these data on his bell housings and will have it corrected if need be.
I told him to also check the pumps for the same problems. You never know. even machinists can have a bad day.

These problem show up easily in velocity when you compare horizontal to vertical and axial.

They show up even when the pressure is not applied. As in any assembly, vertical and axial should not be higher than horizontal.

Of course, you have to determine what is acceptable, specially when the motors are mounted on isolators.

Generally, you will have other machines that are similar and don't have that problem. You can use them as a comparison. If one layout works well there are no reasons why others can't be the same.

Thanks to you all who freely give out your experience on this board.

Yvan