Using nozzle load tables by nozzle size and flange rating

The purchaser's specification or a company standard often gives allowable nozzle loads as a grid: nozzle size down the side, flange class across, and in each cell a radial force, two shears, two bending moments and a torsion. The vessel must take those loads at every nozzle of that size and class. Our notes treat such a table as an envelope: its values are the largest from many conditions, usually without signs.

So each row is an envelope. Its loads did not come from one condition, and nothing says which way each acts. The post on load envelopes explains what that means for the check.

The Nozzle Load Table page holds one row per NPS size and class, in metric or imperial units. Each row has six values and an optional note.

• A value can be typed with a unit, such as 15 kN or 2 kN·m; it is converted to the row's unit when the box is left.
• A box left blank is saved as 0, and the form says so. Anything that is not a number is refused at its box, with the reason, and nothing is saved.
• A size outside NPS 2 to 24 is refused; enter the loads of a larger nozzle in the calculator directly.
• Saving a row for a size, class and unit system that already exists replaces the old row.
• Metric and imperial rows are kept apart: the page and the calculator show only the rows in the unit system in use.

P is entered positive inward, toward the vessel, for every attachment kind. If the source table gives a sign for P, check that it means the same thing before typing it in.

In the calculator, the External Loading card has a picker for the table: choose the NPS, then the class, and click Apply to Loads. The six fields fill from the row, mapped as in the table above. They stay editable, so a value can be changed for the nozzle in hand without touching the stored row.

Before running, set where the loads act. If the table gives loads at the flange face, the calculator can take them at the nozzle end, with the nozzle length, and carry them to the junction. A row has no field for this, so the note on the row is a good place to record it.

Because a row has no signs, enter its values as given and tick the option that also runs the case with the radial load reversed. With torsion and a shear both present, run it again with MT negative. Check the row with the design pressure; that is how such tables are meant to be used.

The calculator checks one nozzle per run. A vessel with several nozzles of one size and class takes the same row on each, but each nozzle sits on its own shell course, with its own pad or none, so each is its own check.

A row can fail where the real loads on the nozzle would pass, because it adds up maximums that never act together. The usual routes are to ask the connected-line designer for the real loads on that nozzle once they exist, to add a pad or a heavier nozzle, or to agree a reduced load for that nozzle. The Find Max option in the calculator gives the largest value of one load, in each direction, with the others held as entered, which helps in that discussion.