Drill pipe is furnished in the following length ranges, which include the upsets but not the tooljoints :-
Range 1 : 18 - 22 ft (5.49 - 6.71 m) — this is rarely seen
Range 2 : 27 - 30 ft (8.23 - 9.14 m)
Range 3 : 38 - 45 ft (11.58 - 13.72 m)
DIAMETER
Drill pipe is furnished in diameters ranging from 23/8"to 65/8". The designated, or nominal,
size of drill pipe is the actual outside diameter in inches of the pipe body when new.
WEIGHT
Drill pipe is furnished in different "weights", i.e. weight per unit length, corresponding to different wall thicknesses. This term "weight" is used to describe several different properties of a length of drill pipe, as follows:
Nominal weight: The designated, or nominal, weight does not now have a physical
significance; it is used only for the purpose of identifying the drill pipe referred to. It is actually the theoretical weight per foot of a 20 ft length of threaded and coupled pipe based on the dimensions of the joint in use for the class of product when that particu- lar diameter and wall thickness was introduced.
Plain end weight: Otherwise known as pipe body weight. This is the weight per unit
length of pipe having the nominal dimensions given in the specification. It is the nomi- nal cross-sectional area multiplied by the density.
Adjusted weight: This is the average weight per unit length of a length of drill pipe
including the end finish (upsets), but excluding the tool joints, based on a total length (excluding the tool joints) of 29.4 ft.
Approximate weight: This is the average weight per unit length of the drill pipe includ-
ing both upsets and tool joints, again based on a joint length (excluding the tool joints) of 29.4 ft. It varies with the type of tool joint used. This is the weight which must be used for the calculation of the total weight of a string of drill pipe (in air).
MANUFACTURING TOLERANCES
For drill pipe up to and including 4" the tolerance on the OD is ±0.031". For sizes of
41/2" and above the tolerance is +1%-0.5%.
The most significant tolerance is that on wall thickness, with a value of -12.5%. The strength of new drill pipe is always based on nominal OD with a wall thickness of 87.5% of nominal.
There is a tolerance of +6.5%-3.5% on the weight of a single joint of drill pipe which defines the limits of average ID and wall thickness for a single joint. For the total weight of the quantity used in a string the tolerance on the low side is reduced to -1.75%
YIELD STRENGTH
Each size and weight of drill pipe is furnished in a range of up to four standard strengths, known as grades. These grades are known as E-75, X-95, G-105 and S- 135. The steel from which these are manufactured has the following yield strengths: Given that strength is a critical
property it is always assumed that the yield strength has its minimum allowable value. This is referred to as the minimum yield strength. It must be emphasised that the "yield strength" of the steels is not the elastic limit - it is the ten- sile stress at which a specified
extension has occurred. This lat-
ter is 0.5% for E-75 and X-95 grades, 0.6% for G-105 and 0.7% for S-135, and is such that after removal of the stress a permanent deformation remains of the order of 0.2%.
USED DRILL PIPE
The API has established a classification for used drill pipe, according to the amount of
wear on the pipe wall. This is reproduced on page C-4. Note that drill pipe does not
remain "new" for very long, and that Class 2 is rarely used within Shell (Class 3 never), thus the majority of drill pipe strings in use within the group fall into the category of "Premium Class".
DESIGN FACTORS
Given the fact that taking drill pipe up to its minimum yield stress will result in perma- nent deformation, it is recommended that this should be avoided and that a design fac- tor should be applied to the yield strength when calculating allowable loads. The API recommends a factor of 0.90, but the usual factor used within Shell is 0.85.
The stresses resulting from tensile and burst loads are directly proportional to the load and the design factor can therefore be applied either within a calculation of maximum allowable load, or directly to the result.
Resistance to collapse under the loads caused by external pressure is not a simple function of yield point and a design factor is normally applied to the calculated collapse
load. A value of 0.9 is usually used.
No design factor is required for torsion, as the torque applied is always limited to the make-up torque of the tool joints, being either 50% or 60% of the tool joint torsional yield strength. Since tool joints are almost always weaker in torsion than the tubes to which they are attached, the latter never approach their limiting strength in torsion. In case of doubt, or critical cases, compare the torsional strength of the pipe as tabulated on page C-17 with the tool joint make-up torque tabulated on pages C-26/30.
Yield strength
Minimum Maximum
Grade psi MPa psi MPa
E-75 75,000 517 105,000 724
X-95 95,000 655 125,000 862
G-105 105,000 724 135,000 931
S-135 135,000 931 165,000 1,138
Drill pipe specifications have been taken from API Spec 5D, 4th Edition, August 1999.
PIPE CONDITION
A. OD Wear Wall
B. Dents & mashes
Crushing, necking C. Slip area Mechanical damage Cuts3, gouges3 D. Stress induced diameter variations 1. Stretched 2. String Shot E. Corrosion, cuts & gouges
1. Corrosion 2. Cuts & Gouges
Longitudinal Transverse
F. Cracks5
A. Corrosive Pitting Wall
B. Erosion & Wear Wall
C. Cracks
PREMIUM CLASS Two White Bands One centre punch mark1
Remaining wall not less than 80%
Diameter reduction not over 3% of OD
Diameter reduction not over 3% of OD
Depth not to exceed 10% of the average adjacent wall4
Diameter reduction not over 3% of OD
Diameter increase not over 3% of OD
Remaining wall not less than 80%
Remaining wall not less than 80%
Remaining wall not less than 80%
None
Remaining wall not less than 80%, measured from base of deepest pit
Remaining wall not less than 80%
None
CLASS 3 Orange Bands
Three centre punch marks1
Any imperfections or damages exceeding CLASS 2
None
None CLASS 2
Yellow Bands Two centre punch marks1
Remaining wall not less than 70%
Diameter reduction not over 4% of OD
Diameter reduction not over 4% of OD
Depth not to exceed 20% of the average adjacent wall4
Diameter reduction not over 4% of OD
Diameter increase not over 4% of OD
Remaining wall not less than 70%
Remaining wall not less than 70%
Remaining wall not less than 80%
None
Remaining wall not less than 70%, measured from base of deepest pit
Remaining wall not less than 70%
None
I. EXTERIOR CONDITIONS2
II INTERIOR CONDITIONS