Nozzle - Area of Reinforcement Definitions

A: This is the required area of reinforcement.  The code specifies that the required thickness is what needs to be replaced (times the appropriate width).  However, if you set the vessel setting “For nozzle reinforcement calcs, replace full thickness of vessel wall” to true (checked), then the corroded host wall thickness will be used instead of the required thickness; this will increase the required area of reinforcement and make it harder to meet the requirement.  This setting defaults to false (unchecked) and can be found on the Design tab in the vessel screen.

A1: This is the available area of reinforcement from the host wall.  The code allows for reinforcement from the host; however, if the vessel setting “Use excess vessel wall thickness for nozzle reinforcement calculations” is set to false (unchecked), then the value of A1 will be set to zero.  This setting defaults to true (checked) and can be found on the Design tab in the vessel screen.

A2: This is the available area of reinforcement from the nozzle wall extending outside the host wall.  If the nozzle is attached by outside fillet welds only and reinforcement calculations are required, this value will be forced to zero per UW-16(f)(3)(b).

A3: This is the available area of reinforcement from the nozzle wall extending inside the host wall.

A41: This is the available area of reinforcement from the nozzle neck perimeter weld outside the vessel wall.

A42: This is the available area of reinforcement from the pad perimeter weld.

A43: This is the available area of reinforcement from the nozzle neck perimeter weld inside the vessel wall.

A5: This is the available area of reinforcement from the reinforcing pad.

C(A): For the determination of A, the value of C is set based on the following criteria.  If the host is a flat head/blind flange, the value is always set to 0.5 [see UG-39(b)(1)].  If the host is a cylinder, cone, or dished head and normal reinforcement calculations are being performed per UG-37 the value is 1 for internal pressure and 1/2 for external pressure [see UG-37(c), UG-37(d)(1)].  If the host is a cylinder or cone and compact reinforcement calculations are being performed per Appendix 1-7(a), the value is 2/3 for internal pressure and 1/3 for external pressure [see UG-37(c), UG-37(d)(1), and Appendix 1-7(a)].

C(A5): For the determination of A5, the value of C is set to 1, when the split repad penalty is not considered and it is set to 0.75 when the split repad penalty is considered.  To consider the split repad penalty, check the box “Apply Split Repad Penalty [UG-37(h)]” on the Area Info tab in the nozzle form.  The check box defaults to true (checked).

CLor: This is the custom limit of reinforcement as entered by the user.  This is a diameter value, so half of this value will be used to determine if the values of Lpar and Lpar17a need to be further limited.  It is only used when the user has activated the Custom Limit of Reinforcement field in the nozzle form on the Area Info tab.

d: This is the developed opening in the host as defined in the figure UG-40.  This takes into account the nozzle configuration and the angle in which it intersects the host.  The value used in the calculations are based on the corroded dimensions are required per UG-16.  In addition, the value used in the calculations may be entered directly if the user decides to use  a custom developed opening in the nozzle form on the Design Info tab.

dneck: This is the distance the nozzle neck extends past the outside surface for partially inserted nozzle configurations [Figure UW-16(k) and Partial Penetration].

Dp: This is the reinforcing pad diameter in the corroded condition (UG-16).

F: This is a factor that compensates for the fact that the circumferential stress in cones and cylinders is twice the longitudinal stress and the tr value is based on the circumferential stress.  When evaluating planes of reinforcement other than those parallel to the axis of the cone or cylinder, the value may be set to value between 0.5 and 1 assuming the opening is integrally reinforced.   The code defines integrally reinforced as a nozzle without a repad and attached by full penetration welds.

fr values: These are strength reduction factors that account for the fact that nozzle neck, weld, and repad materials may not have the same allowable stress that the host material does.  The values may not exceed 1.0; but they may be less depending on the strength of the nozzle and repad material.

L41pareff: This is the effective weld leg for leg 41 in the direction parallel to the opening axis.  It will be between zero and the value of leg 41 in the corroded conditions.  It can be limited by the Lpar and/or Lpar17a values falling in the weld leg or not even reaching to the weld at all.

L42pareff: This is the effective weld leg for leg 42 in the direction parallel to the opening axis.  It will be between zero and the value of leg 42 in the corroded conditions.  It can be limited by the Lpar and/or Lpar17a values falling in the weld leg or not even reaching to the weld at all.

L43pareff: This is the effective weld leg for leg 43 in the direction parallel to the opening axis.  It will be between zero and the value of leg 43 in the corroded conditions.  It can be limited by the Lpar and/or Lpar17a values falling in the weld leg or not even reaching to the weld at all.

L41noreff: This is the effective weld leg for leg 41 in the direction normal to the host wall.  It will be between zero and the value of leg 41 in the corroded conditions.  It can be limited by the Lnoro value falling in the weld leg or not even reaching to the weld at all.

L42noreff: This is the effective weld leg for leg 42 in the direction normal to the host wall.  It will be between zero and the value of leg 42 in the corroded conditions.  It can be limited by the Lnoro value falling in the weld leg or not even reaching to the weld at all.

L43noreff: This is the effective weld leg for leg 43 in the direction normal to the host wall.  It will be between zero and the value of leg 43 in the corroded conditions.  It can be limited by the Lnori value falling in the weld leg or not even reaching to the weld at all.

Lnoro: This is the normal limit of reinforcement extending outside the vessel as determined per UG-40(c).

Lnori: This is the normal limit of reinforcement extending inside the vessel as determined per UG-40(c).

Lpar: This is the parallel limit of reinforcement determined per UG-40(b).  It extends from the axis of the opening outward along the surface of the host.  It can never be higher than what is allowed in UG-40(b); however, it can be reduced by the custom limit of reinforcement, CLor.

Lpar17a : This is the parallel limit of reinforcement determined per UG-40(b) with further considerations from Appendix 1-7(a).  It extends from the axis of the opening outward along the surface of the host.  It can never be higher than what is allowed in UG-40(b) and Appendix 1-7(a); however, it can be reduced by the custom limit of reinforcement, CLor.

Rn: This has a conditional definition.  If the code year for the vessel is 2010, this is defined as ½ the developed opening.  If the code year for the vessel is 2011 or later, this is defined as ½ the nozzle neck inside diameter.  This value is fed into the calculation for the Lpar value, so going from a code year of 2010 to a later year could potentially reduce the limit of reinforcement.

t: This is the host wall thickness determined in the corroded condition (UG-16) and considering pipe undertolerance if applicable.

te: This is the nozzle repad thickness in the corroded condition (UG-16). 

ti: This is the nozzle wall thickness extending inside the vessel wall in the corroded condition (UG-16) but not considering pipe undertolerance when performing reinforcement calculations (see definition of tn in UG-37(a).  When this value is calculated considering corrosion, it uses the specified inside corrosion allowance on the inside of the nozzle neck and the specified inside corrosion allowance on the outside of the nozzle neck.

tn: This is the nozzle wall thickness extending outside the vessel wall in the corroded condition (UG-16) but not considering pipe undertolerance when performing reinforcement calculations (see definition of tn in UG-37(a).  When this value is calculated considering corrosion, it uses the specified inside corrosion allowance on the inside of the nozzle neck and the specified outside corrosion allowance on the outside of the nozzle neck.

tr: This is the required thickness of the host wall at the location of the opening.  If both internal and external pressure exist, then a value will be determined for each case.  Note that UG-37(a) defines this value in such a way to give as much advantage to the designer as possible to reduce its value, so in several cases this could be less than the tr value used to design the host itself.  For example, if the nozzle is placed in the center of an elliptical head instead of near the edge, the tr value will be reduced to less than what was used to determine the necessary thickness for the head itself.  Likewise it is more advantageous to place the nozzle in the dish of a torispherical head than in the knuckle.