In designing basket offshore we use DNV No.2.7-1 Standar for Certification Offshore Containers April 2006.
Basket purpose to transported :
Know the equipment to be transported Material with weighing max 1500 kg
1. Determine SWL, based on the weight of the load that is 2000 kg, with 500 kg added clearance, then the SWL is 2500 kg.
2. Determine the appropriate dimension to the basket offshore,. So the appropriate dimensions are, length 2180mm, 1570 mm Width, and 1430 mm Height.
3. Frame from hollow size 150 x 150
3. base on material calculation the weight of this basket is 1000 kg. Tare mass then this is it.
4. To get the value of the Rating we must Summarize between SWL and Tare Mass. So the rating is 2500 kg 1000 kg plus or equal to 3500 kg.
Padeye Calculation
Calculations to determine the pad eye thickness is based on DNV 2.7-1 standard. Here calculation for offshore basket with a rating of 3500 kg, 4 lifting points with a lift angle of 45 °.
Based on the value rating 3500 kg then we get the value of WLL is 8410 kg (Table 8.1 Standard DNV 2.7-1). Furthermore, from the value of WLL we can determine the value of working load limits for shackles (WLLs).
WLLs = WLL ÷ ((n-1) . cos θ)
= 8410 ÷ ((4-1) . cos 45°)
= 5336,4 kg
So, the shackles that shall be used is shackle with size 7 / 8 “(6.5 tons)
The next step is we set the value of RSL (Resulting Sling Load).
RSL = (3 . R . g) ÷ ((n-1) . cos θ )
= (3 . 3500 . 9,81) ÷ ((4-1) . cos 45°)
= 65293,2 N
Before going any further to calculate the tear out stress and contact stress, there are four parameters that we have to specify in advance:
1. Specify the material to be used for the pad eye. In this calculation material used is the yield strength of A36 at value of (Re) 250 MPa.
2. Holes on the pad eye to enter pin Shackle (DH)
DH = B + (0,06 . B) , where B is the diameter of shackles pin
= 25 + (0,03 . 25)
= 25,75 mm , so we shall set the value up
= 26 mm
3. Padeye distance from the center hole to the top (H) we set in H = 50 mm
4. For the thickness (t) we also specify in advance = 19 mm.
Once all the parameters we’ve got and we set, then we do the calculations to determine the tear out stress criteria and contact stress criteria.
Tear Out Stress Criteria
Re ≥ (3 x RSL) ÷ ((2 X H X t)-(DH X t))
Re ≥ (3 x 65293.2) ÷ ((2 X 50 X 19)-(26 X 19))
Re ≥ 332965,6 ÷ 2160
250 ≥ 139 MPa —-> OK
Contact Stress Criteria
Re ≥ 23,7 * (√(RSL ÷ (DH X t)))
Re ≥ 23,7 * (√(65293.2÷ (50 X 19)))
250 ≥ 196 MPa —-> OK
From the above calculation we can know that the criteria for tear out stress and contact stress with the material A36 is OK. Therefore padeye thickness 19 mm can be used for basket offshore with a rating of 3500 kg.
Padeye Calculation
Calculations to determine the pad eye thickness is based on DNV 2.7-1 standard. Here calculation for offshore basket with a rating of 3500 kg, 4 lifting points with a lift angle of 45 °.
Based on the value rating 3500 kg then we get the value of WLL is 8410 kg (Table 8.1 Standard DNV 2.7-1). Furthermore, from the value of WLL we can determine the value of working load limits for shackles (WLLs).
WLLs = WLL ÷ ((n-1) . cos θ)
= 8410 ÷ ((4-1) . cos 45°)
= 5336,4 kg
So, the shackles that shall be used is shackle with size 7 / 8 “(6.5 tons)
The next step is we set the value of RSL (Resulting Sling Load).
RSL = (3 . R . g) ÷ ((n-1) . cos θ )
= (3 . 3500 . 9,81) ÷ ((4-1) . cos 45°)
= 65293,2 N
Before going any further to calculate the tear out stress and contact stress, there are four parameters that we have to specify in advance:
1. Specify the material to be used for the pad eye. In this calculation material used is the yield strength of A36 at value of (Re) 250 MPa.
2. Holes on the pad eye to enter pin Shackle (DH)
DH = B + (0,06 . B) , where B is the diameter of shackles pin
= 25 + (0,03 . 25)
= 25,75 mm , so we shall set the value up
= 26 mm
3. Padeye distance from the center hole to the top (H) we set in H = 50 mm
4. For the thickness (t) we also specify in advance = 19 mm.
Once all the parameters we’ve got and we set, then we do the calculations to determine the tear out stress criteria and contact stress criteria.
Tear Out Stress Criteria
Re ≥ (3 x RSL) ÷ ((2 X H X t)-(DH X t))
Re ≥ (3 x 65293.2) ÷ ((2 X 50 X 19)-(26 X 19))
Re ≥ 332965,6 ÷ 2160
250 ≥ 139 MPa —-> OK
Contact Stress Criteria
Re ≥ 23,7 * (√(RSL ÷ (DH X t)))
Re ≥ 23,7 * (√(65293.2÷ (50 X 19)))
250 ≥ 196 MPa —-> OK
From the above calculation we can know that the criteria for tear out stress and contact stress with the material A36 is OK. Therefore padeye thickness 19 mm can be used for basket offshore with a rating of 3500 kg.
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