MODULE NEMA 23 CAESAR 5.1 2

[psapiensone]

I calculate moments and forces resultants for comparate with Cesar 5.1 NEMA 23 Module.
The loads and Dc factor are ok, but my problem are the moments.
I don't know as Caesar it calculates this.
I calculate using the considerations included in NEMA 23.
I use translations force from other connections to principal nozzle for determinate de resultants moments...

I hope answers

Thanks a lot.

Pablo

 

[ApC2Kp]

PaulusP,

There might be a difference in the reference point for the summation of moments and loads. Some use the discharge flange face as the reference point. Some others use the shaft and discharge line intersection as the reference for summation of moments and loads.

 

[psapiensone]

Thanks ApC2Kp, I have a new ask...
Caesar II use for calculate Dc factor the nominal diameters, but I understand that, according to that mentioned in NEMA 23, should be calculated with internal diameters.
Please, can somebody clarify this?
Regards.

 

[C2it]

The usual assumption is that Dc is based on nominal diameter. I always ensure that this and the resolution point are clarified and agreed with the vendor, early in the project and preferably at bid stage.

 

[ApC2Kp]

PaulusP,

NEMA 23 defines

D = Nominal size of the connection in inches up to 8 inches in diameter.

NEMA 23 goes on to further instruct the user,

For sizes greater than this, use a value of

De = (16 + Dnom ) inches / 3

and these apply to loads on individual connection.

CaesarII should calculate the De automatically.

There is also the check of the combined resultants, and then the term Dc has diameter equivalent to total of areas of the openings up to a value of 9 inches in diameter. For openings larger than 9 inches, use a value of Dc "adjusted"

Dc = (18 + Equivalent diameter) / 3 (where De=equivalent dia)

And it is this area that would be calculated based on the inside diameter of each connection.

The NEMA 23 input requested by CaesarII is the nominal diameter number, but there might be a link back to the model piping data for the inner diameter? The loads are already limked by node number designation of each connection. This would be a good question for COADE techsupport.

 

[psapiensone]

I verified all the calculations of Caesar and it uses the internal diameter, I used a simple excel sheet, and the results of Caesar are "ok" in comparison with NEMA 23.
If we considerate the internal diameter the result it is more conservative.

But, textually NEMA says:
Dc = Diameter (in inches) of a circular OPENING equal to the total areas of the inlet, extraction, and exhaustopenings up to a value of 9 inches in diameter. For values beyond this, use a value of Dc equal to:

(18+Equivalent diameter)
Dc = --------------------------
3

I undertand OPENING as the internal diamter.

I think that it is necessary to clarify the NEMA.

 

[JohnBreen]

This is an interesting discussion. There is MUCH in NEMA SM-23 (and SM-24) that begs for interpretation from the NEMA Committee but they just do not do it. Write as often as you want and they do not reply. Also, they say one thing in the text and they do something else in the example "problems".

Oh well, that is the reason why we have discussion forums.

John

 

[psapiensone]

Thanks John, finally I used internal diameter for to do more conservative my calculations.
Regards,
Pablo