API 4F 3rd Edition Specification for Drilling and Well Servicing Structures

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API 4F 3rd EditionSpecification for Drilling and
Well Servicing Structures

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API 4F 3rd Edition

• Specification Scope
• All new designs of steel structures for drilling
  and well servicing
• Derricks
• Masts (Freestanding)
• Guyed Masts
• Crown Blocks

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API 4F 3rd Edition

• Product Specification Levels
• PSL1
• Minimum level within specification
• Reflective of typical current practices
• PSL2
• Includes all requirements of PSL1, plus
  additional requirements
• Heat treatment operations
• Through-thickness NDE
• Weld acceptance criteria
• Traceability requirements
• Nameplate markings

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API 4F 3rd Edition

• Nameplate Markings
• Requirements vary by type of structure
• Markings to be raised or stamped
• Nameplate to be securely fixed to structure in
  conspicuous place

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API 4F 3rd Edition

• Structural Safety Level (SSL)
• Classification of the application of a drilling
  structure to reflect degree of consequence of
  failure in light of
• Life safety
• Pollution
• Economic loss
• Public concern
• Expectation of environmental event

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API 4F 3rd Edition

• Structural Safety Level (SSL)
• Specified by agreement of purchaser and
  manufacturer at time of order
• Two SSLs required
• Expected event SSL (E1, E2 or E3) for events with
  adequate warning for preparations
• Unexpected event SSL (U1, U2 or U3) for events
  with insufficient warning for preparations
• E1, U1 represent high consequence levels
• E2, U2 represent medium consequence levels
• E3, U3 represent low consequence levels

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API 4F 3rd Edition

• Structural Safety Level (SSL)
• Expected and unexpected SSLs can be different
  e.g. A manned platform classified as a U1 could
  be classified as an E2 or E3 if the platform is
  to be evacuated for the expected event
• SSLs currently used only for design for wind
  loading, but could be useful construct for
  seismic, transport or erection design in future

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API 4F 3rd Edition
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API 4F 3rd Edition

• Design Specification Allowable Stresses
• Based on AISC 335-89 - Specification for
  Structural Steel Buildings, with modifications
• Plastic design not allowed
• Fatigue design not required unless specified by
  purchaser at time of order
• Increases in allowable stresses for secondary
  stresses and for extreme level wind, dynamic and
  earthquake loads

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API 4F 3rd Edition

• Design Specification Secondary Stresses
• Stresses resulting from elastic deformations and
  rigidity of joints
• Increase in allowables of 20 for all loadings
  except earthquake, as long as primary stresses do
  not exceed basic allowables
• Increase in allowables for secondary stresses is
  in addition to increases in allowables for
  extreme wind and dynamic loading

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API 4F 3rd Edition

• Design Specification Wind Dynamic Stresses
• No increases in allowable stresses for Operating
  and Erection load cases
• 1/3 increase in allowable stresses for low
  probability extreme events, provided that
  stresses for these loadings less wind and dynamic
  loads, meet basic allowable stresses of section
  8.1.1
• Increases for Transportation load cases to be
  specified with loadings by purchaser

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API 4F 3rd Edition

• Design Specification Wire Rope
• Wire rope assemblies for erection and guy lines
  to have nominal strength 2.5 times maximum design
  load
• Nominal assembly strength to be derated for end
  connection efficiencies and for small sheave
  diameters (D/dlt18) per API RP 9B

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API 4F 3rd Edition

• Design Specification Crown Shafting
• Allowable stresses per AISC 335-89 except that
  factor of safety for bending of shafts shall be a
  minimum of 1.67 to yield
• Wire rope sheaves and bearings are covered by ISO
  13535 or API spec 8

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API 4F 3rd Edition

• Design Specification Operating Loads
• Drilling Loads
• Hook load with fastline and deadline loads
• Rotary load
• Setback load
• Dead loads
• Fluid loads
• Additional loads as agreed by purchaser and
  manufacturer
• Rig instructions to include list of all items
  with their total dry and wet weights as used in
  the design, as well as a sum of the weights and
  the first moment of these weights about the base
  of the drilling structure for both dry and wet
  conditions

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API 4F 3rd Edition

• Design Specification Wind Loads Overview
• Wind environments to be considered
• Operational wind
• Erection wind
• Transportation wind
• Unexpected storm wind (storm with insufficient
  warning to lay down full pipe setback)
• Expected storm wind (storm without full pipe
  setback)
• Wind speeds specified by
• Purchaser for operating, erection and
  transportation environments
• Outside meteorological agency or specification
  for Expected and Unexpected environments
• Rig configuration in each wind environment must
  be considered
• Design wind speeds subject to minimums (Table 8.3)

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API 4F 3rd Edition

• Design Specification Wind Loads Overview
• Wind forces are calculated on member-by member
  basis with realistic shape factors
• All drilling structures to have identical design
  criteria for same storm environments
• Gust factor modifier Gf used to correct 3 second
  gust for spatial coherence effects i.e. larger
  structures are unlikely to have full gust on
  entire structure
• All equipment, windwalls and accessories must be
  included.
• Shielding is allowed
• Name plate and rig instruction changes required

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API 4F 3rd Edition

• Design Specification Wind Loads
• Design Reference Wind Velocity Vref
• Specified as 3 second gust at a 10 meter (33
  feet) reference elevation above ground or mean
  water level
• Different values for each wind environment
• Expected Storm (no setback)
• Offshore 100 year return period (RP) per ISO
  19901-1 and API-2INT-MET
• Onshore 50 year RP per ASCE/SEI 7-05 or
  similar
• Unexpected Storm (with setback) Same as Expected
  except
• Onshore 75 of Vref for Expected case
• Offshore GOM 78 knots (100 year RP for sudden
  storm)

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API 4F 3rd Edition

• Design Specification Wind Loads
• Maximum Design Rated Wind Speed Vdes
• Nameplate wind speed
• May be different for Expected and Unexpected wind
  environments
• Taken as Vref x aonshore (or aoffshore as
  applicable)
• Factor dependent on SSL and locale (offshore or
  onshore)
• Wind direction to be from any azimuth

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API 4F 3rd Edition

• Design Specification Wind Methodology
• Purchaser specifies SSLs and rig working
  locations
• Purchaser specifies Vref for operating,
  transportation and erection cases
• Designer determines Vref for Expected and
  Unexpected wind environments from outside
  meteorological sources
• Designer determines Vdes for each wind
  environment using SSL multipliers of Tables 8.1
  and 8.2, but subject to minimum design speeds of
  Table 8.3

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API 4F 3rd Edition

• Design Specification Wind Methodology
• For each wind environment and wind direction,
  designer calculates forces on members and
  appurtenances
• Determines local wind velocity at any elevation
  above ground or mean water level using elevation
  factors (8.3.1.3 and Table 8.4)
• Calculates wind forces on all members and
  appurtenances per section 8.3.3, using local wind
  velocity and
• Member inclination factor, Ki, to account for
  inclination of member to wind direction (8.3.3.2)
• Wind shape factors (8.3.3.4 and Table 8.6)
• Projected areas of members and appurtenances
  (8.3.3.5 and 8.3.3.6)
• Areas of members directly in front of or behind
  windwalls may be excluded

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API 4F 3rd Edition

• Design Specification Wind Methodology
• Designer calculates global wind forces and
  combined loading stresses with member unity
  checks
• Scales vector sum of all member and appurtenance
  wind loads using
• Shielding factor Ksh per section 8.3.3.1
• Gust factor Gf per section 8.3.3.3 and Table 8.5
• Total scaled wind loads for all members and
  appurtenances should not be less than sum of
  unscaled loads on primary structure
• Combines scaled wind loads with other loads for
  all load combinations
• Checks member unity checks under all load
  combinations with scaled global wind loads, but
  with full unscaled wind load on the particular
  member in question (as though that member is
  unshielded) as well as any appurtenances attached
  to that member

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API 4F 3rd Edition

• Design Specification Wind Loads
• Nameplate and Rig Instruction Changes
• Add structural base design elevation
• Include Vdes for expected and unexpected storm
  winds
• Nameplate graph of Hook load vs. wind velocity to
  have linear transition from 1.0 AMOD for
  Operating to 1.33 for Unexpected storm
• Rig Instructions to include detailed listing of
  wind areas for two orthogonal directions, with
  sum of areas and first moment of areas about base
  of structure

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API 4F 3rd Edition

• Design Specification Inertial Loads
• Purchaser to provide motion data
• Minimum dynamic load combinations
• Longitudinal forces of surge and sway, with heave
• Transverse forces of sway and roll, with heave
• Diagonal forces calculated as RMS of longitudinal
  and transverse forces, with heave, unless
  otherwise specified by purchaser
• Design loadings per specification and as
  specified by purchaser

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API 4F 3rd Edition

• Design Specification Dynamic Amplification
• Purchaser to supply motion information of
  supporting structure or vessel
• Analysis by rational methods appropriate to
  dynamic sensitivity of drilling structure to
  applied motions

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API 4F 3rd Edition

• Design Specification Earthquake Loads
• Earthquake design criteria to be specified by
  user including loading, analysis method and
  allowable response
• Land-based units can be designed per local
  building codes using equivalent static design
  methods
• Offshore rig design per strength level analysis
  guidelines of API RP2A with 1/3 allowable stress
  increase considering both primary and secondary
  stresses (secondary stress increase not allowed)

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API 4F 3rd Edition

• Design Specification Erection Loads
• Erection loads to be combined with dead loads and
  erection wind loads, with additional loads as
  specified by purchaser
• Fluid loads or added dead loads required for
  erection to be noted on nameplate and in rig
  operating instructions
• Crane erected structures to be designed per API
  RP2A, including dynamic factors

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API 4F 3rd Edition

• Design Specification Transportation Loads
• Transportation loads to be combined with dead
  loads and wind and inertial loads, as specified
  by purchaser

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API 4F 3rd Edition

• Design Spec. Overturning and Sliding
• Sliding coefficient of friction mf
• Soil, concrete, wood matting mf .15 max.
• Steel on steel mf .12 max.
• Alternate values allowed with testing and
  consistent rig operating procedures
• Factor of safety to inadvertent sliding
• Land-based structures 1.25 min.
• Offshore structures 1.50 min.

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API 4F 3rd Edition

• Design Spec. Overturning and Sliding
• Resistance to sliding and overturning
• Dead weights to limited to 90 of expected values
• Fluid loads and removable dead loads not allowed
  for consideration unless specified in rig
  operating instructions. Those required for
  erection stability shall also be specified on
  nameplate.
• Dead weights of offshore structures shall be
  further reduced by negative heave acceleration

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API 4F 3rd Edition

• Design Spec. Overturning Factor of Safety
• Freestanding structures
• Land-based structures 1.25 min.
• Offshore structures 1.50 min.
• Moments taken about common tipping line through
  centroid of nominal support reactions
• Nominal support reactions to be consistent with
  allowable ground bearing pressures or support
  structure allowable loads

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API 4F 3rd Edition

• Design Spec. Overturning and Sliding
• Clamped Structures
• Structures not meeting freestanding FS
  requirements for sliding and overturning must be
  clamped
• Clamps to resist overturning and sliding loads in
  all load combinations, calculated with 125 of
  overturning or sliding loads and minimum dead
  weights and restricted fluid loads and
  counterweights
• No increase in allowable stresses for wind or
  dynamic loadings for clamps
• Pretension of bolts intended for reuse limited to
  .5 Fu times nominal cross-section area

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API 4F 3rd Edition

• Design Spec. Overturning and Sliding
• Dual Load Path Elements
• Structural components, other than clamps, which
  have one load path for a given member load, and
  an alternate load path for a similar member load
  with the opposite sign
• Components to meet all design requirements
• Components also must meet design allowables for
  load case with overturning loads increased by
  factor of 1.25,
• with 2/3 increase in allowable stresses for
  expected and unexpected wind, dynamic and
  earthquake loadings
• with 1/3 increase in allowable stresses for
  operating, erection and transportation loadings

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API 4F 3rd Edition

• Design Spec. Overturning and Sliding
• Documentation
• Clamp installation instructions to be included
  with rig instructions, with bolt pretension
  values and tolerances
• Owner/operator to develop procedures for storm
  preparation to include proper clamp installation
  per manufacturers recommendations

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API 4F 3rd Edition

• Materials
• All materials to be suitable for application, but
  specification requirements cover critical
  components
• Materials must be produced to a written
  specification to include physical and chemical
  properties and material qualification
• Mechanical properties per ASTM A370 or equal on
  representative coupons from same heat with same
  working operations and heat treatment
• Wrought materials to be processed to produce
  wrought structure throughout component
• PSL 2 requires additional heat treatment QA/QC

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API 4F 3rd Edition

• Bolts
• If conforming to recognized industry standard,
  they must be marked per that standard
• Other bolts must meet chemical, physical and
  mechanical property limits specified by bolt
  manufacturer
• Wire Rope
• Must conform to ISO 10425 or API Spec 9A

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API 4F 3rd Edition

• Welding Requirements
• Spec requirements apply to critical components
• Welding and welding QA/QC per AWS D1.1
• AWS prequalified joints are acceptable
• All weld procedures must be written
• Includes prequalified joints
• All essential variables must be covered per
  specification
• Procedure Qualification Records must record all
  essential variables
• Consumables per AWS or manufacturers standards
• Consumables must be stored and controlled by
  written procedure per manufacturers
  recommendations

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API 4F 3rd Edition

• Welding Requirements
• PQR weld properties shall meet the minimums
  required by design, with test weldments in the
  applicable post-weld heat-treated condition
• When impact testing is required for base
  material, it shall be a requirement for PQR
• Tests shall be consistent with base metal
  requirements in weld and HAZ per Tables C-4.1 and
  C-4.2 of AWS D1.12002 or ISO 19902
• Attachment welds only require HAZ impacts
• Post-weld heat treatment shall be per weld
  procedure

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API 4F 3rd Edition

• Welding Requirements - Repairs
• Repair welds shall be made per qualified written
  weld procedure, with adequate access for
  evaluation, repair and inspection
• Repair shall be made to ensure complete fusion
  with base metal
• WPS shall reflect actual repair sequence and heat
  treatment imparted to repair item

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API 4F 3rd Edition

• Quality Control System
• Manufacturer must have written quality program to
  ensure that product quality is planned,
  implemented and maintained
• Issuance and revision of manual must be
  controlled
• Measuring and Testing Equipment
• QC equipment to be identified, controlled and
  calibrated at regular intervals per
  manufacturers written procedures to a recognized
  industry standard

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API 4F 3rd Edition

• Quality Control Personnel
• NDE personnel must be qualified to ISO 9712
• Inspector performing welding visual inspection
  must be qualified to
• AWS certified welding inspector
• AWS certified associate welding inspector
• Manufacturers written qualifications
• Other QA/QC personnel to be qualified per
  manufacturers written qualifications

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API 4F 3rd Edition

• Non-destructive Examination
• NDE activities for critical components, as
  defined by engineering, must be documented and
  approved by a level 3 examiner qualified to ISO
  9712
• NDE examinations shall be conducted after final
  heat treatment

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API 4F 3rd Edition

• Required NDE of Components
• All critical welds require
• 100 visual inspection
• 20 MP or LP inspection as designated by
  engineering
• 100 UT or RT of all full or partial penetration
  welds loaded in tension to 70 or greater of
  allowable stresses
• All inspections per AWS D1.1
• 100 UT for laminations and internal
  discontinuities of connections with
  through-thickness stresses greater than 70 of
  allowables, when PSL 2 is specified
• NDE acceptance per AWS D1.1 criteria for static
  structures for PSL 1 and per those for cyclically
  loaded structures for critical welds of masts and
  derricks when PSL 2 is specified

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API 4F 3rd Edition

• Workmanship and Finishing
• Structures per fabrication requirements of AISC
  335-89
• Castings cleaned and cored holes drifted
• Steel products to be protectively coated prior to
  shipment
• Socketing of wire ropes per API RP 9B and
  proof-tested

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API 4F 3rd Edition

• Purchasers Inspection and Rejection
• Manufacturer to provide purchasers inspector
  reasonable notice for available inspection dates
• Purchasers inspector to be afforded free entry
  at all times at place of manufacture prior to
  shipment
• Unnecessary interference with operation of works
  grounds for refusal of inspection
• Purchaser may reject defective material after
  shipment or after being properly put into service
  with written notice
• Destructive testing required by purchaser paid
  for by purchaser unless materials fail to meet
  requirements
• Purchaser or user may review all design and
  fabrication documentation at manufacturers
  location for compliance with standard

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API 4F 3rd Edition

• Testing
• Proof load testing not required except as agreed
  by manufacturer and purchaser per Supplementary
  Requirement SR2
• Design Verification by proof testing or by
  computer analysis modeling to show under design
  loadings
• Proof testing method and assumptions to be
  documented
• Computer modeling to be documented to show
  compliance with section 8
• Verification by qualified person other than
  designer of test
• Wire rope end connections proof-tested to 50 of
  nominal wire rope assembly strength
• Cylinders and winches to be pressure tested to
  1.5 times working pressure for minimum of 10
  minutes

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API 4F 3rd Edition

• Traceability
• MTRs required for steels with Fy greater than
• Structural shapes and plates 248 MPa (36 ksi)
• Tubing 317 MPa (46 ksi)
• Solid round bars 414 MPa (60 ksi)
• Material substitutions to be documented and
  traceable to specific unit, except for bolts made
  and marked per recognized standard
• PSL 2 Critical components to have full
  traceability
• PSL 2 Certified reports required for nonferrous
  materials and bearings

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API 4F 3rd Edition

• Documentation
• Records required by standard to be kept safe and
  retrievable for five years
• Documentation must be clear, legible,
  reproducible
• All QC records to be signed and dated, but
  electronic files can be signed with
  originators personal code
• Purchaser has right to review records for
  compliance with specification

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API 4F 3rd Edition

• Documentation Records
• Design records (section 8.5)
• Written specifications (sections 9, 10, 11)
• Qualification records welding to include
  procedures, welders, NDE personnel, and
  calibration of measuring and testing equipment
• MTRs
• NDE records (section 10)
• Performance test records for proof load testing,
  hydrostatic testing and slingline socket testing
• Special Process records

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API 4F 3rd Edition

• Documentation for Purchaser
• Operational features, block reeving diagram and
  lubrication points
• Instructions for raising and lowering of mast
  and/or substructure
• Facsimile of nameplate
• Tables summarizing wet and dry weights and first
  moments about structure base (section 8.2)
• Tables summarizing wind areas and first moment of
  areas about base of structure (section 8.3.2)
• Data Book per Annex A, SR3 if specified by
  purchaser

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API 4F 3rd Edition

• Supplementary Requirements
• SR1 Low Temperature Testing
• Minimum design temperature and impact-test
  requirements to be agreed upon by purchaser and
  manufacturer
• Critical components to be fabricated from
  materials meeting impact testing requirements
• Weld procedures for critical components to
  include impact testing consistent with
  requirements of base metals (section 10.5)
• Nameplate to include minimum design temperature
  and SR1
• Rig instructions to list required impact values
  for each base metal

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API 4F 3rd Edition

• Supplementary Requirements
• SR2 Proof Load Test
• Test load to be agreed upon by purchaser and
  manufacturer
• Structure to be visually examined after test per
  section 11.4.2
• Nameplate to be marked with SR2 and ratio of test
  load to design load
• SR3 Data Book
• Requirement to be specified by purchaser
• Minimum requirements per Annex A, SR3