Derrick

1 CONCEPTUAL DESIGN
2 TYPES AND CHARACTERISTICS
- DERRICK
- MAST
- RAM RIG
3 RIGGING UP
4 DRILLING LOADS
- Calculation of Drilling Loads at Crown Block
- Definition of Gross Nominal Capacity
5 INSPECTION

1 CONCEPTUAL DESIGN
- Derricks
Derricks and Masts consist of a steel framework with a square or rectangular cross-section.
Their purpose is to support the hoisting equipment and rack the tubulars while tripping.
The number of joints in a stand (single-double-triple) that the rig can pull is dependent on the height of the derrick.
- Manufacturer Specifications
Derricks are manufactured in accordance with API 4F or related ISO (International Organization for Standardization) 13626 draft.
This specifications covers the design, manufacture, and use of derricks, portable masts, crown block assemblies and substructures.
- Nameplate Information
Derricks built within API/ISO specs must have a specification nameplate attached in a visible place containing the following information:
a. MANUFACTURER’S NAME.
b. PLACE OF CONSTRUCTION.
c. STANDARD ADOPTED (ex. API 4F). d. SERIAL NUMBER.
e. HEIGHT ( ft ).
f. MAXIMUM STATIC HOOK LOAD ( lbs) FOR STATED NUMBER OF LINES TO TRAVELLING BLOCKS. g. MAX. RATED WIND VELOCITY (Knots) WITH RATED CAPACITY OF PIPE RACKED.
h. EDITION OF THE API  SPEC. USED
I.  GUYING DIAGRAM (when applicable)
j. The following note: “CAUTION: ACCELERATION OR IMPACT, ALSO SETBACK AND WIND LOADS WILL REDUCE THE MAXIMUM RATED STATIC HOOK LOAD CAPACITY.”k. LOAD DISTRIBUTION DIAGRAM.
l. GRAPH PLOTTING MAX. ALLOWABLE STATIC HOOK LOAD VERSUS WIND VELOCITY. m. MAST SETUP DISTANCE FOR MAST WITH GUY LINES.

2 TYPES AND CHARACTERISTICS
There are 3 different types of derricks:
- DERRICK
- MAST
- RAM RIG

- DERRICK
Pyramidal steel framework with square or rectangular cross section assembled as fixed structure.
- API Definition
A semipermanent structure of square or rectangular cross-section having members that are latticed or trussed on all four sides.
This unit must be assembled in the vertical or operation position, as it includes no erection mechanism. It may or may not be guyed.
Derrick Types
Derrick are normally used on Offshore rigs and can be divided into categories:
- Stationary Derrick
Derrick used on offshore fixed structures
- Dynamic Derrick
Heavyweight derrick used on floating rigs subjected to marine stress.
- MAST

Installation on offshore floating unit

A Mast is a steel framework with square or rectangular cross-section comprised of multiple sections assembled together.
Mast are normally used on land rigs; they are rarely used on offshore rigs.
Most masts have one side open (window side), while others have both the front and rear side open
(full view).
Generally masts are assembled on the ground in horizontal position and are raised using the drawworks. Some masts use telescopic sections and are assembled in vertical (boot strap).
- API Definition
3.16 mast: A structural tower comprised of one or more sections assembled in a horizontal position near the ground and then raised to the operating position.
If the unit contains two or more sections, it may be telescoped or unfolded during the erection procedure.
Mast Types
There are 2 different types of masts for land drilling and service rigs:
- STATIONARY BASE
- WITH GUY LINES
- RAM RIG
The RAM RIG is a new concept used to hoist the drill string.
The Drawwork and the drilling line are replaced with a system of hydraulic pistons and rams. Ram rigs can be used with singles or stands, depending on the height of the derrick.
They have only recently been developed and are not yet classified within API/ISO Specs

3 RIGGING UP
- Conventional Mast (Land rig)
Erection sequence
- Vertical Mast (offshore Rig)
- Trailer Mounted Rig
Rigging Up Sequence of a Trailer Mounted Rig
- a) Deploying of substructure base
- b) Anchoring of trailer to substructure base
- c) Extension of the telescopic sections
- d) Installation of the hydraulic rams
- e) Anchoring the mast to the substructure
- f) Raising the mast in vertical position
- Final Position

4 DRILLING LOADS
- Forces on the Derrick
Derricks are subjected :
- Weight of the derrick itself
- Wind load
- Stress induced by Floating hull motion
(for floating vessels)
- Horizontal component load of the drill string when racked back
- Hoisting load
5 INSPECTION
- Periodic inspections
The API applicable references are:
API RP 4G and API RP 54 (chapt. 9.2 and 9.3). and the Manufacturer's recommendations.
ENI policy is more strict and requires the API Category IV inspection (as per API RP 4G) every 5 years instead of 10.
Mast/derricks and substructures on mobile offshore drilling units or fixed platforms are exempted from the requirements of a Category IV inspection.