API 610 ALLOWABLES

Would like to confirm my assumption regarding API 610 pump nozzle allowables on existing pumps/piping. If we're tying into only one nozzle
say the suction and analyze and qualify per 1x the API tables,we can walk away and not look at the existing discharge. If we are between 1 and 2 times the table then we would have to analyze the existing discharge and
qualify both nozzles per the interactive equations F.1.2b and c. Or could we still walk away if we're below 2x the allowables?

In general, you have to analyze both the suction and the discharge for any API pump. This is because we often put very minimal flexibility into the suction lines to keep the NPSH requirement down - I have seen many more pump installations fail to qualify under API on the suction side than on the discharge side. Remember that, even for suction from a tank at ambient temperature, your pipe will have temperature fluctuations due to solar irradiation and normal ambient temperature fluctuations. We can ignore such small temperature variations for pipe, but sometimes our piping system is stiff enough that even small temperature changes cause nozzle allowables to be exceeded. Also, don't forget about tank and support settlement.

If both nozzle load sets are under the contractual load limit (many organizations now specify pumps with 2X API or higher allowable nozzle loads), you're OK. If not, and you're within 2X the contractual limit, you can use Annex F to calculate your way around the basic table limits. Note that you could easily fail to meet the equations in Annex F without any single load on any nozzle exceeding 2.0x the basic table allowable - for instance, all your loads could be 60% over, and you would then exceed the limits of equations F.1 and F.2 by about 6.7%.

I believe the API-610 nozzle allowable loads are the minimums that the pump must accommodate and higher allowables may possibly obtained from the manufacturer. I also believe these allowables are for when the pump is running. Is there a different allowable load for when the pump is not running, such as during steam-out conditions?

For example, I have an application where the service temperature is only 90 °F but the steam-out temperature is 350 °F. I believe that designing for the API610 allowable loads or even the manufacturer's allowable loads for the steam-out temperature would result in an overly conservative piping design. Do you have any advice on this subject?

Hi JohnSr

I think steam out can do done by disengaging piping from equipment.
So there will be no nozzle load issue on that case.

Regards

Habib