Lifting Lug – WRC Calculation

Introduction:

All directly welded parts to the pressure parts like lifting lugs, support lug, trunnion etc. are need to be checked for WRC 107/537. All related calculations are carried out in PV Elite once given proper inputs. In some cases, it is not possible to build such directly welded parts in PV Elite due to software constrain. For example, adding lifting lug on top dish end of vertical equipment is not possible in PV Elite. In those cases, it is mandatory to perform WRC calculations by any other means. This article will help to perform such calculations with analytical solutions followed by CodeCalc calculations.

Inputs:

Consider an equipment with top 2:1 ellipsoidal dish end with directly welded lifting lugs. All necessary input data is given below.

VESSEL ODDm219.1MM
VESSEL THICKNESSt6.16MM
VESSEL WEIGHTWL304.7KG
VESSEL CG HEIGHTL31190.515MM
DESIGN LENGTH T-TL12105.9MM
CG TO TOPL2915.385MM
TAILING LUG OFFSETL4109.55MM
Fig.1 Loads acting on equipment during erection.

Solution:

To consider the maximum force acting on equipment, vessel is considered to be lifted from horizontal position to vertical. At all lifting positions forces acting on lifting and tailing lugs are calculated as given below and maximum of acting force is taken for the analysis. 

Lifting lug forces:

Maximum transverse load per lug     PT = P cosθ / N

Maximum longitudinal load per lug   PL= P sinθ / N

Where, N = number of lugs

Tailing lug forces:

Maximum radial load on a lug            PR = T sinθ

Maximum longitudinal load on a lug  fL= T cosθ

LIFTING ANGLE θTAILING LOAD T (KG)LIFTING LOAD P (KG)
   
5131.8458372172.8541628
10131.2420611173.4579389
20129.9847735174.7152265
30128.5839955176.1160045
40126.9063811177.7936189
50124.7141611179.9858389
60121.4986062183.2013938
70115.8832583188.8167417
80102.2730061202.4269939
901.55963E-13304.7
   
MAX131.8458372304.7
LIFTING LOAD COMPONENT
MAX TRANSVERSE LOAD PER LUGPTmax1.86651E-14KG
MAX LONGITUDINAL LOAD PER LUGPLmax304.7KG
TAILING LOAD COMPONENT
MAX TRANSVERSE TAILING LOADfLmax131.344124KG
MAX LONGITUDINAL TAILING LOADfrmax11.49112187KG

Therefore, 304.7kg force is taken for WRC analysis and its components acting on lug are calculated as given

h125mm
wl37mm
wb82mm
   
C5.752101mm
Fig.2 Lifting lug geometry and its fillet weld dimensions
Radial load acting on lugPrad0kgf
Longitudinal shear force acting on lugVC304.7kgf
Circumferential shear force acting on lugVL304.7kgf
Circumferential momentMC0kg-m
Longitudinal momentML0kg-m
Torsional momentMT36.33483487kg-m

Thus after calculation of forces and moments acting on lifting lug, WRC 107/537 analysis is carried out in CodeCalc in following steps

Step-1: Input lifting lug data in CodeCalc

Lifting lug data
Fig. 3(a) Lifting lug input data in CodeCalc
Fig.3(b) Lifting lug input data in CodeCalc

Step-2: Input WRC 107/537 data in CodeCalc

lifting lug data
Fig. 4(a): WRC 107/537 inputs in CodeCalc
Fig. 4(b): WRC 107/537 inputs in CodeCalc