Hi all,

Regarding API 617 Force and Moment equations in SI Units, are they included 1.85 times of NEMA?

Can we derived NEMA in SI unit from API 617 by deviding right side by 1.85?

For example, equation (2.E-1a) API617 is Fr + 1.09Mr <= 54.1De --> NEMA in SI Unit is Fr + 1.09Mr <= 29.24De

Since this is true for US units in API617.

The allowable load limits for NEMA (and therefor API617) use a formula that is set for US Customary units and cannot be simply converted for other units. What we do is convert the non-US units to US terms and apply the US limits.

That said, then yes, with US units you can use API61 to back out the NEMA allowable limits. But why not just use NEMA?

I understand that the NEMA document that provides these turbine load limits has been rescinded even though API 617 still references 1.85 times NEMA. CAESAR II still has the NEMA check.

I worked for a famous firm and they have converted NEMA to SI unit by an excel sheet for turbine/compressor nozzle loads evaluation through many projects. It seems logic and working.

This is also same philosphy with PSE book by Peng, page 297, chapter 6, I quote as below:

"Most pipe stress analysis software packages convert the calculated metric units force and moment to the units given by the equation (in NEMA) and then evaluate them with the equation. This sounds inconceivable, but it is the only way to get the job done. To make the equation more universally appealing, it can be converted by multiplying the entire equation with 12 as : 36FR + MR' <= 6000De (Inconsistent units)

Where MR' = 12MR is the resultant moment in inch-pounds. In this new equation, the number 36 represents 36 in. By the same token, 6000 represents 6000 lb. With 36 and 6000 properly defined, they can be converted to any unit desired."

How do you think?

it would be nice if the standard produced an evaluation scheme that is transparent to units.

Your quote shows a method for adjusting the individual nozzle limits but there is more work to do in setting the overall, combined resultant loads. To adjust one without the other would be even more confusing.

For units discussion you may take a look to
http://65.57.255.42/ubbthreads/ubbthreads.php?ubb=showflat&Number=58621

best regards