Lloyd Lif

LLOYDS REGISTER OF SHIPPING

Guidance Notes for Module Lifting Criteria -----------------------------------------1.0 Lifting Design Cases 1.1 The design of the structure is to take account of the following lift cases: 1.1.1 1.1 .1 Balanced Lift - whereby the lifting sling origin coincides in plan view with the centre of  gravity of the structure, with the padeye loads to be direct function of their distance from the C.G. In this case a load factor of 2.0 is to be applied to all gravity loads for analysis purposes. Consider Consideratio ation n may be given to reducing this factor for m embers clear cle ar of the padeye region where a sufficient degree of structural redundancy is known to exist. 1.1.2 Unbal anced ance d Lift - whereby whereby the distributio distribution n of loads on the the padeyes due due to lifting lifting is made arbitrarily. arbitrarily. Submitted calculations calculations are to to demonstrate demonstrate the ability of the structur st ructuree to resist resis t any racking racki ng effect generated by diagonally opposite sling legs carrying a disproportionately high share of the lifting load. In this case the lifting weight should be distributed thus: 75% of lifting load carried by two diagonally opposite padeyes. 25% of lifting load carried by the other two padeyes. Each padeye's share of the respective percentage of load is to be  proportional  propor tional to its distance dista nce from f rom the t he C.G. C.G . of the th e lift as a whole. whole . 1.1.2 Consideration will be given to a reduction in the degree of imbalance for cases where lifting arrangements incorporate spreader bars, etc. The desig design n lift lift weight weight used for this c ase should be based on the lift weight we ight including contingencies, contingenc ies, factored by a dynamic factor of 1.33. Consideration will be given to the reduction of this factor to a minimum of 1.10 for heavy lifts. 1.2 Each of the lift cases given by 1.1.1 and 1.1.2 is to be considered as 'norm al operational' in the context of allowable stress. 1.3 Lifting padeyes are to be constructed from Grade D material. 1.4 Special consideration consideration will will be be given given to structures where the number numb er of lift lif t points is less than th an four. 2.0 Structural Appraisal of Padeyes 2.1 The following gives an acceptable method for the analysis of the padeye. 2.2 Padeye geometry.

2.2.1 The key padeye dimensions are shown in Fig.1. 2.2.2 The effective thickness, te of each cheek plate considered for the following padeye strength calculations should be limited to the smallest value of:a. Half the basic lug thickness, that is t b /2.

 b. Three times the weld length, that is 3W l.

c. The actual cheek plate thickness, that is tc .

For items a. and b. above, any greate r thickness proposed will be assumed to act as a spacer above. 2.2.3 The hole, diameter d, through the padeye should be finish machined after welding the cheek   plates to ensure a uniform bearing surface. 2.3 Load, directions of action. 2.3.1 Loading direction definitions are shown in Fig.2. 2.4 Padeye strength. 2.4.1 The allowable axial force on the padeye is the least of the following values where Fy is the S.M.Y.S.:Shear = 0.60 (atl + 2 bte ) Fy

Tension= 1.08 (ctl + (D-d)te ) Fy

Bearing =

.87 d (tl + 2te ) Fy

The following limitations apply:1.0 < ( d ) < 8.0 ( --------------) ( tl + 2te )

if ( d ) < 1.0, put (tl + 2te ) = d in the above formulae.   (-------------) ( tl + 2te)

2.4.2 The pin should be a reasonable fit in the hole, see fig.1 that is (d HOLE/d PIN) < 1,05. Should a greate r clearance be required the padeye may be treated as a curved beam under the action of a concentrated force, or of a force acting over a small area. 2.4.3 The cheek plate welds should be checked for the proportion of the applied force carried by the cheek plates based on the ratio of actual thickness and normally including half of the total weld length. If it should be necessary to utilise all of the weld length then the tension should be repeated with half  the cheek plate forces being transferred through the basic lug section. 2.4.4 Transverse and Oblique Forces should normally be dealt with where possible by re-orientation of the lug axis to bring the forces coincident with the lug axis to bring the forces coincident with the lug axis and then using the corresponding geometry relative to the new axis. If this technique is not  possible the padeye should be given special consideration. 2.4.5 Lateral Force. This force will normally determine the design sections of the padeye remote from the region of the cheek plates. In the absence of a specific lateral force a value of 5% of the design padeye sling force should be assumed to be acting at the edge of the pin hole, concurrently with the axial force.