DBSE (Distance Between Shaft Ends)
DBSE (Distance Between Shaft Ends)
(OP)
For new lube oil pump ,We have faced issue of not able to achieve the required DBSE. The deviation between the design and actual DBSE is 3mm.The motor bolts are bolt bound and there is no margin available to shift motor to achieve the required DBSE.I know there is one way which to enlarge bolt hole diameter in motor with to achieve DBSE but Guys ,Is there any other reliable way to solve this problem that we can do it on base frame pad rather touching the motor.





RE: DBSE (Distance Between Shaft Ends)
Johnny Pellin
RE: DBSE (Distance Between Shaft Ends)
"Is there any other reliable way to solve this problem that we can do it on base frame pad."
Depends what the drawings and pictures of the base frame show.
If you cannot access the holes in the base to enlarge them Another option is using bolts with strategically reduced body diameter.
Much discussion amongst various parties will likely required before such a modification is permitted.
Reduced diameter bolts are Commercially available.
Here is one source - reduced diameter bolts
Whenever bolt holes are enlarged nice thick hardened washers are needed to keep from "coning" and forcing the motor etc to move back toward center.
Actually, NTH washers are good to have in every installation.
And no lock washers.
RE: DBSE (Distance Between Shaft Ends)
It would help to know the manufacturer of the pump.
RE: DBSE (Distance Between Shaft Ends)
RE: DBSE (Distance Between Shaft Ends)
RE: DBSE (Distance Between Shaft Ends)
RE: DBSE (Distance Between Shaft Ends)
The way we do this is fab up a rigid plate you can bolt on the hub, and make a spacer of the desired adjustment, 60 thou or whatever you want. then you start to apply torque to the plate and the hub starts moving. Sometimes it doesn't move and you can apply some heat to the hub to loosen it up. It depends on the pump.
This fix has to be agreed upon by the owner of course. Also, vendors don't always give you couplings that fit, and when you call them out on it they will tell you to move the hub. Additionally, some flexible couplings are pretty forgiving. Check the coupling against the data sheet to make sure it matches, and see if you can find a tolerance for axial distortion for the coupling.
Let me know if something here doesn't make sense.
In my experience, as long as most of your hub is on the shaft you are ok. This is subject to owner's approval and they will decide if they take it or not.
RE: DBSE (Distance Between Shaft Ends)
Johnny Pellin
RE: DBSE (Distance Between Shaft Ends)
RE: DBSE (Distance Between Shaft Ends)
My experience was the coupling manufacturer's engineering support will be ready, willing, and able to answer that.
Before making the call Be sure to have the info on hand that would be required to select the coupling initially.
An Example is Page 268 / T-10 here -
file:///C:/Users/Robyn%20Timberlake/Desktop/cd%20chnger%20repair/Torsional2010.pdf
I'd request a formal response via e-mail to keep in the job records, just in case.
RE: DBSE (Distance Between Shaft Ends)
As far as engineering standards on overhang, depends on torque, area of shaft to hub, if you really want to guess then take the limiting agent there, probably the shear key and do some math voodoo.
RE: DBSE (Distance Between Shaft Ends)
One more help , see attachment- my coupling drawing shows DBSE (minimum-127mm , maximum-141.14mm and actual-127mm ), so which value(Actual/Minimum/Maximum) is to considered while setting DBSE in field?
Also usually how much tolerances allowed in DBSE and spacer length? For example If spacer length is 126mm then what should be DBSE(+/-) for Sureflex TB woods coupling for a Lube oil pump?
RE: DBSE (Distance Between Shaft Ends)
Ideally, you would get the coupling manufacturer to review this and give you written confirmation that it is appropriate. But, I know some manufacturers do not respond well to these sorts of requests.
Johnny Pellin
RE: DBSE (Distance Between Shaft Ends)
I have below queries:
1.What do mean by ideal spacing?Is it the Actual DBSE-127mm?
2. How much hub overhang is allowed are you aware of any engineering standard reference?
3. How much tolerances allowed in DBSE and spacer length? For example If spacer length is 126mm then what should be DBSE(+/-) for Sureflex TB woods coupling for a Lube oil pump?
RE: DBSE (Distance Between Shaft Ends)
If I am given an acceptable range for something like DBSE, I would prefer to be right in the center of that range to allow for necessary adjustments in the future. The range on the drawing shows that you can overhang the hubs by as much as 0.28 inches (one half of the difference between minimum and maximum DBSE). The drawing actually shows the hubs overhanging.
The correct setting for this coupling is not defined by DBSE. The drawing clearly shows the required spacing between the inner faces of the coupling hubs at 1.0 inch. That is what it should be set to. It is not shown, but I assume that this includes an axial clearance between the rubber spacer and the inside of the hubs. We have an internal specification that defines this internal axial clearance for a Woods coupling of this type as 1/16" as shown in our drawing (attached). The couplings we use for our governors are much smaller than the one you are working on, so the required axial clearance may be greater. But, ultimately, if you set the hubs at a 1 inch spacing, you will be set as the manufacturer requires.
Johnny Pellin
RE: DBSE (Distance Between Shaft Ends)
The measured DBSE is 130.14mm and it well within the range specified in drawing(Maximum-141.14mm,Minimum-127mm)
If you don't mind ,just for my knowledge I want to understand the importance of G (Coupling spacing shown in drawing)? Is there any tolerance allowed in this value G?
Also what is significance of internal axial clearance for a Woods coupling of this type?
RE: DBSE (Distance Between Shaft Ends)
Johnny Pellin
RE: DBSE (Distance Between Shaft Ends)