WRC 107 Thrust Load Design vs Operating Pressure

[hawksy]

For calculating the thrust load for nozzles; is it required to use the design pressure or is it common to use the normal operating pressure?

Thanks

 

[TGS4]

Design.

 

[pennpiper]

I am sure there is going to be a lot of controversy on this one.

I say use Maximum Operating Pressure.

I also say use Maximum Operating Temperature for calculating liner expansion in Pipe.

By using Max. Operating criteria for these you will prevent "Over Design" and the unnecessary added cost to the Project.

 

[Crompto29]

Pennpiper,

That sounds like taking short cuts.

What if the next owner of the equipment spots the higher design pressure and makes the decision for whatever reason to increase the operating pressure?

An Engineer may not go looking through the design manuals (if they still exist) because they know a competent engineer will have DESIGNED equipment to DESIGN conditions.

I am currenty working with 3rd hand 40 year old 30bar hyperbaric diving chambers. No Docs, no drawings etc. Just a name plate.......

 

[TGS4]

Actually, the answer depends on whether you are trying to satisfy the primary stress limits or the secondary stress limits?

If primary, then use design. If secondary, use operating. For an explanation, I will simply point you to Section VIII, Division 2, Part 5. The requirements there are very clear on this point.

 

[hawksy]

Thanks for all of the input. This is a secondary stress and after a long discussion with the end user we have agreed to use the maximium operating pressure.

 

[Crompto29]

Figure 5.1 says it all. It does make sense. Understanding the difference between Operating and Design Conditions is important.