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API RP 95F:2006 pdf download

API RP 95F:2006 pdf download.lnterim Guidance for Gulf of Mexico MODU Mooring Practice—2006 Hurricane Season.
Note: A minimum site-specific hindcast study for the tropical weather and winter weather parameters requires the following:
Hurricane Extremes: These will he based on a hindcast database of winds, waves, and currents derived from numerical models that have been validated against severe historical storms. That validation will show the wave and wind models have a coefficient of variation (COV) no more than 15°/o when comparing model peak storm values to measurements. The acceptable COV for the current model validation can be as high as 30%. Any bias between the model and data will be removed with at least a simple linear fitting process.
The hindcasted period will include at least the 56 year period beginning 1950. The numerical models will he based upon discrete finite element or finite difference solutions of the governing partial differential equations. arid not parametric models. Grid resolution will he a minimum of 15 km. and the overall domain will cover at least the northern half of the Gulf of Mexico.
An extremal analysis will be performed on the hindcast results using either a pooling method or a deductive model as described in Toro1. If pooling is chosen, then at least three sites in a general east-west direction will be pooled. with the pattern centered on the location of interest. These sites shall have a spacing of 75 to 150 km but will span a total distance of no more than 300 km. When pooling within 200 km of the coast, the pooled sites must be chosen to ensure that they have fetch and depth similar to the site of interest.
Winter Extremes: These will he based on either hindcast model results or analysis of nearby buoy data. i.e. the NDBC buoys. If hindca.st models are used, they will cover at least 15 years encompassing the months of October-April, and have been validated in the same manner as described above for the hurricane models. If buoy wind and wave measurements are used, they will cover at least five years of measurements covering the months of October-April. Currents can be based on one year of data collected during October-April. Measurements should have been taken in a similar water depth and preferably within a few tens of kilometers of the site of interest. A trained metocean specialist will review the measurements and apply adjustments for fetch arid water depth.
Operational Criteria: These will be based oii the same methods used for the winter extremes described in the previous paragraph.
All three criteria categories need to be included in derivation of site-specific studies due to overlap of seasonal information in determination of design criteria for any given location arid deployment period.
15. What type of mooring system is planned?
An inherent assumption of this checklist approach is that any system chosen is designed to the same level of utilization. Differentlevels of analysis may have been undertaken, and credit is given for that, but regardlessof the level of analysis, if two systems are“compared,” it is assumed that they will have the same safety factor in the same return period event. Hence differences are due tothose that are inherent within the design, be they features or disadvantages.
The type of mooring system has an impact on the probability of failure, and the consequences of failure.However, a system thatmay be good in one way may be bad in another. For example, a conventional catenary moored unit is likely to have a robustmooring system.There considerable experience with these, hence they are better understood, and they are generally more robustand less sensitive to small errors in either installation or analysis.However, a catenary mooring system will have a considerablequantity of chain at the seabed, and in the event of the MODU drifting,could do significant subsea infrastructure damage.


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