ALLOWABLE NOZZLE LOADs 3

What is on the skid?

Perform a stress analysis of the piping connected to the skid components. Then perform an FEA of the components affected by those piping loads, including all other loads (internal/external pressure, wind, seismic) acting on the components. Those loads will be used to size the skid components, the anchor bolting and the skid itself. Accordingly, the cost of the skid and piping can be established and included in the plant budget cost.
cheers,
gr2vessels

You should probably ask the skid manufacturer to specify the allowable forces and moments on his battery limit flanges and you configure your offskid piping to suit, verified by a stress analysis of the offskid piping.

By requesting the skid manufacturer to nomonate the allowable forces and moments, he will be defining the acceptable installation and operating conditions, removing any dispute he may have later should a warranty claim arise. In this instance be careful that the manufacturer does not come up with an unrealistically low set of values to protect his equipment but make your piping design hell. I recall some pump manufacturers (thankfully not API 610) asking for zero forces and zero moments from piping!

Conversely, we have specified the values to package suppliers at bid, requiring the nozzles to meet or exceed the strength requirements and offskid piping is designed to meet these limits. This is usually done when the schedule is tight and piping design must be ongoing before vendor data is available.
Regards,
Bill

to all.....

This issue of allowable nozzle loads keeps popping up like an ugly foot-fungus....over and over again.

I have dealt with this issue (on and off) since 1972

I this it is very important that all "newbies" to this issue recognize this interplay between equipment vendors and A&E firms as a game. The A&E firms want to do a reasonable job. The equipment vendors are 1) afraid of extreme loads that will cause thier equipment to fail and 2)are motivated by additional money that can be squeezed from the client in "approving nozzle loads"

Both of these motivations prompt vendors to come up with inane requirements such as "Zero forces and moments"

BillBirch is on the right track. Ask for reasonable forces and moments at the bid stage...

-MJC

I think what is more important than the interplay between parties is to understand what the equipment has been designed to do. In the case of pump units designed to carry pipe thrust/loads etc you can only be governed by what is reasonable in line with what the manufacturers advise as to off-set load or thrusts being transmitted into the pump cases, mountings etc. In the case of ANSI, DIN and other foot mounted overhung impeller pumps any loads applied to the flanges can lead to casing deflections resulting in pump failures. For the later units it is reasonable to spec. "zero forces and moments" as a basis on which to call bids as the pumps have NOT been designed to carry any thrust or deflective loads.
I do not believe for 1 minute that the manufacturer/vendor is motivated by anything other than ensuring the end user get a piece of equipment that will operate as it was designed and not suffer premature failure because of pipe / thrust loads.

All this means is that the pipe engineer designing the system does some work to come up with a design to eliminate or remove the loads rather than cutting corners and requiring units to carry in some cases unspecified and unrealistic loads.

I too have been involved with this issue over many years and have seen the results of pipe loads (many by accident not design)on pump equipment not designed to carry these loads.

Zero forces and moments is never acceptable, nor reasonable. You violate it just by hanging a flange. Even if zero forces and moments are designed for, it doesn't stay that way after relaxation of the pipe. It is reasonable for some equipment to have lower allowables than others, especially when detrimental performance is concerned; however, I'll never buy a pump, etc. with a zero force and moment restriction.

I2I

External Loads on Nozzles and Pipe Intersections (Part 1)

L S THILL

External Loads on Nozzles and Pipe Intersections (Part 2)

L S THILL

Mr. Thill,

You are putting yourself at risk (lawsuit) by posting those copyrighted materials. I hope PRG gave you permission.