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API SPEC 4F 2nd Edition, January 1, 1995
Complete Document
Specification for Drilling and Well Servicing Structures
Includes all amendments and changes through Reaffirmation Notice , February 1, 2001
Page Count:24
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This specification covers the design, manufacture, and use of steel derricks, portable masts, crown block assemblies, and substructures suitable for drilling and servicing of wells. It includes stipulations for marking, inspection, standard ratings, design loading, and design specifications of the equipment. Definitions of commonly used terms are included in Section 3.


1.1.1 The purpose of this specification is to provide suitable structures for drilling and well servicing operations and to provide a uniform method of rating the structures for the petroleum industry. It is the intent that these specifications be applied to all new designs of all standard derricks, special derricks, portable masts and substructures.

1.1.2 Products manufactured according to API Standards 4A, 4D, and 4E may not necessarily comply with all the requirements of this specification. It is the committee's intention that this standard be written to meet the requirements of present and future operating conditions, such as deeper drilling, offshore drilling from floating devices, and the effect of earthquakes, storms, and other adverse operating conditions.

1.1.3 The standard is not a text book, but rather a guide by which the manufacturer and user will have a common understanding of the capacities and ratings of the various structures for drilling and well servicing operations.


This specification establishes requirements for two product specification levels. These two PSL designations define different levels of technical and quality requirements. PSL 1 includes practices currently being implemented by a broad spectrum of the manufacturing industry. All the requirements of this specification are applicable to PSL 1 unless specifically identified as PSL 2. PSL 2 includes all the requirements of PSL 1 plus additional practices currently being implemented by a broad spectrum of users.


Supplementary requirements shall apply only when contractually specified by the Purchaser. Appendix A gives a number of standard supplementary requirements.