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Blockline and crown loads - Audit
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Blockline Loadings, release 5, issued 24 April 2008. AUDIT version.
The current release of this worksheet exists in different versions. They are identical apart from the way they are formatted. The Work version hides intermediate calculations and allows the user to see the results just below the inputs. This is useful for quick “what-if” games, changing various inputs to see what works best. The Audit version displays all intermediate calculations. The PDA version removes all text and formats the input and output fields for optimum viewing on a mobile, small-screen device.
This Audit version of the worksheet shows the formulae and intermediate results to allow auditing.
User input
1″ 6×19 IPS IWRC1″ 6×19 EIPS IWRC1.125″ 6×19 IPS IWRC1.125″ 6×19 EIPS IWRC1.25″ 6×19 IPS IWRC1.25″ 6×19 EIPS IWRC1.375″ 6×19 IPS IWRC1.375″ 6×19 EIPS IWRC1.5″ 6×19 IPS IWRC1.5″ 6×19 EIPS IWRC1.625″ 6×19 IPS IWRC1.625″ 6×19 EIPS IWRC1.75″ 6×19 IPS IWRC1.75″ 6×19 EIPS IWRC1.875″ 6×19 IPS IWRC1.875″ 6×19 EIPS IWRC2″ 6×19 IPS IWRC2″ 6×19 EIPS IWRC |
0 |
lbkg |
Either; select a blockline
OR, enter wire breaking strength
10 |
Number of lines strung. Nbl =
3.5 |
Safety factor required for the blockline. SFbl =
PlainRoller |
Select a block bearing type to determine API friction factor
1000000 |
lbkg |
What is the maximum crown load (eg derrick limit)? Fcllimit =
45000 |
lbkg |
Travelling block weight. mtb =
250000 |
lbkg |
Desired load carried under the travelling block. Fhlbb =
Click here when any values are modified to update the result.
Calculations
First calculate the limiting loads within the capacity of the line and the crown/derrick.
Reeving efficiency;
Max fast line tension;
Max hook load;
Dead line tension at max hook load;
Load on the crown at maximum hook load;
Now compare the limiting crown load with the crown load at the maximum hook load and return the lowest value;
Using the lower of the two, work out the hook load, fast line and dead line loads.
Calculate the maximum useable load below the block
Actual safety factor on the fast line at the maximum (limiting) hook load.
Second calculate the actual loads arising from the desired load under the hook.
Total hook load = load under the hook plus the travelling block.
Fast line load and dead line loads.
Actual safety factor on the fast line at the desired hook load.
Actual load on the crown.
Desired hook load as a percentage of maximum.
Results
1 – limits of the line and derrick; the limiting
Wire rope strength
Maximum hook load (including travelling block)
Maximum useable hook load (accounting for block)
2 – loads arising from the desired load under the travelling block, or
Fast line load
Dead line load
Crown load
Safety factor on the fast line
Specified hook load as % of maximum
Worksheet references
Institut Francais du Petrole. “Drilling Data Handbook” 6th Edition.
Release 1 of this worksheet was issued on 18 April 2008
