API RP 4G:2012 pdf free download.Operation, Inspection, Maintenance, and Repair of Drilling and Well Servicing Structures
5.2 Loading
The safe operation of drilling and well servicing structures depends on whether the foundation is adequate for the load imposed (see Section 11). Environmental and dynamic loads should be considered. The design load for foundation requirements should be the sum of the weight of the drilling or well servicing structure, the weight of the machinery and equipment on it, the maximum hook or rotary load of the structure, forces due to external guywire loading, and the maximum setback load (see Section 15). During erecting and lowering operations utilizing the rig drawworks, the slowest practical line speed should be used. Loads due to impact, jarring, acceleration, and deceleration may be indicated by fluctuation of the weight indicator. The operator should keep the indicator readings within the nameplate hook load capacity rating. Some rig designs require that the mast base structure be restrained against uplift from the application of mast hook load.
5.3 Bolted Structure
5.3.1 General Each part of a bolted structure is designed to carry its share of the load. Parts omitted or improperly placed may contribute to the failure of the structure. During erection of bolted structures, bolts should be left loose enough, in way of erection, to allow proper fit of adjacent mast/derrick members without distortion and locked in stress. This procedure permits correct alignment of the structure, which results in proper load distribution. At completion of erection, all bolts should be checked for proper torque.
Periodically, all bolts should be checked for proper torque. Suitable instructions regarding the proper installation of clamps, pins and bolts used for tie downs shall be developed for existing structures by a qualified person utilizing manufacturer’s guidelines when available. Tie down components incorporating bolts which are expected to be tensioned multiple times shall be designed with specified pretension no greater than 50 % of the bolt material minimum ultimate strength times its nominal cross-sectional area. Clamp installation instructions shall include pretension values and tolerances. Bolt tensioning shall be achieved using calibrated tensioning methods. Bolts that are specified to be pretensioned to a higher value than 50 % of the bolt material minimum ultimate strength shall only be used once.
The length of bolts shall be such that the end of the bolt will be flush with or outside the face of the nut when properly installed. While it may the responsibility of the manufacturer to give guidelines on erection and bolt installation, it is the responsibility of those performing the actual work that are accountable.
5.3.2 Bolt Pretensioning The use of the turn-of-nut method is always acceptable for use on bolts which are not to be reused. Reuse of bolts is acceptable if so specified in the manufacturer’s instructions or by a professional engineer. This method yields a more consistent pretension without the need for calibration. AISC’s Research Council on Structural Connections document Specification for Structural Joints Using ASTM A325 or ASTM A490 Bolts may be used as a reference in addition to AISC 335-89.
5.4 Racking Platforms A well-constructed pipe racking support, which is designed to prevent pipe from falling, should be provided in the mast/derrick. Pipe-racking fingers should be kept straight and secured with a safety device.
The working platform should be made of a nonskid material and should not extend into the travel path of the hook and block, swivel, top drive system, and motion compensator. If the platform is not constructed of nonskid material, it may be applied to the surface as necessary.
Fall protection should be properly secured and provided at all times.API RP 4G pdf download.API RP 4G:2012 pdf free download
