Stabilizers
1.1 General
This section applies to drill stem stabilizers and near-bit stabilizers, with either integral-body or welded-blade
construction. The important dimensions of stabilizers are defined in Figure 15.
55
Rotary Drill Stem ElementsFigure 15—Measurement Definitions for Stabilizers
1.2 Material Requirements
1.2.1 General
Stabilizers may be made from standard steel or non-magnetic stainless steel. Standard steel shall be used
unless non-magnetic material is specified. Integral-body stabilizers or the core of welded-blade stabilizers made
from standard steel shall be quenched and tempered full-length.
1.2.2 Neck Regions
1.2.2.1 Tensile Requirements
The neck regions of an integral stabilizer and the core of a welded-blade stabilizer shall have tensile properties
equal to those of drill collars of the same size, as detailed in Table C.17 (Table D.17) or Table C.18 (Table D.18)
of this standard.
1.2.2.2 Impact Energy Requirements
The neck regions shall also meet the impact energy requirement of 8.2.1.3 or 8.3.2.3.4 of this standard.
Testing of standard steel stabilizers is required on each heat per heat treatment lot.
1.2.2.3 Special Testing Requirements of Integral Stabilizers
For an integral-blade stabilizer, the tensile and impact specimens shall be taken from a prolongation of either
neck, with the center of the specimen at least 101.6 mm (4 in.) from a free end and at least 25.4 mm (1 in.) below
the finished surface of the neck, as shown in Figure 16. The prolongation shall be the same diameter as the neck
at the time of heat treatment. The uniform region shall extend for at least 400 mm (16 in.) from each end of the
finished stabilizer or to within 25.4 mm (1 in.) of the stabilizer blades, whichever is less, as shown in Figure 16.
The extent of the area of controlled properties shall be verified by Brinell hardness testing of the neck outside
diameter with a minimum hardness of 285 HBW.
56
API Specification 7-1 When standard steel material is heat treated as a forging or bar, without knowledge of the final neck diameter, the
sampling location shall be determined by the largest diameter of the forging or the diameter of the bar.
In all cases, the radius of the sample location shall be reported.
Figure 16—Sampling Locations
1.2.2.4 Traceability
The manufacturer shall establish and follow procedures for maintaining material identity. The methods of
maintaining identity shall be at the option of the manufacturer. These procedures shall provide means for tracing
the stabilizer body to the relevant heat, chemical analysis report, and specified mechanical test results.
1.2.3 Body Regions
An integral-blade stabilizer shall be machined from a single piece of material. The core and necks of a welded
blade stabilizer shall be machined from a single piece of material. The material shall be inspected for defects
according to Section 12 and shall meet the acceptance criteria as defined therein. Mechanical testing shall only
be required for the neck region as defined above.
1.3 Blade Welding
For welded-blade stabilizers, there shall be a documented welding procedure (WPS and PQR) for the welding of
blades to the stabilizer core, and welders or welding machines shall have documented qualification (PQR) to this
procedure. The welds shall be inspected using a documented procedure of non-destructive evaluation.
NOTE
Transverse welding at the ends of blades is not recommended.
1.4 Abrasion Protection
The crown surface of the stabilizer shall be provided with protection against abrasion. The protection method
is optional to the manufacturer unless specified by the purchaser and is outside the scope of this standard.
However, a documented procedure for applying this protection shall exist (WPS for welded hard-facing), and
welders or welding machines shall have documented qualification (PQR) to this procedure.
1.5 Dimensional Requirements
1.5.1 General
The following dimensional requirements apply to all stabilizers covered by this standard.
57
Rotary Drill Stem Elements11.5.2 Neck Length
The length of upper and lower necks shall be as indicated in Table C.32 (Table D.32).
1.5.3 Neck Diameters
Upper and lower neck diameter shall be as described in Table C.33 (Table D.33); Figure 17 and Figure 18 are
referenced by Table C.33 (Table D.33). Tolerances shall be the same as those defined for drill collars in Table
C.15 (Table D.15).
1.5.4 Blade Dimensions
The blade diameter, length and number shall be as indicated in Table C.34 (Table D.34).
11.5.5 On Gauge Blade Diameter
For a gauge stabilizer, the blade diameter shall be defined using a ring gauge of the same dimensions as the bit
no-go gauge of 10.2.3.1 for the given nominal diameter. Other measuring methods may be used, with the ring
gauge as arbiter in case of dispute. The diametrical clearance to this gauge shall be 0 mm to 0.76 mm (0 in. to
0.03 in.).
1.5.6 Blade Spiral
The spiral shall be as defined on the purchase order and interpreted according to Table C.35 (Table D.35).
Unless otherwise specified, the spiral shall be right-hand.
1.6 Connections and Bevel Diameters
1.6.1 Size and Type
The connections shall be as described in Table C.14 (Table D.14). The bevel diameters for the upper connection
of all stabilizers and for the lower connection of drill stem stabilizers shall be the same as those defined in
Table C.14 (Table D.14). The bevel diameter for the lower connection of near-bit stabilizers shall be as defined in
Table C.20 (Table D.20) for a bit sub.
1.6.2 Gall Resistant Treatment of Threads and Sealing Shoulders
For standard steel stabilizers, a gall-resistant treatment of zinc or manganese or zinc-and-manganese phosphate
shall be applied to the threads and sealing shoulders of both the upper and lower connections. Application
of the treatment shall be after completion of all gauging. The treatment type shall be at the discretion of the
manufacturer.
58
API Specification 7-1
Figure 17—Blade Taper Geometry
Figure 18—Watermelon Geometry
1.7 Customer Information
1.7.1 Required Information from Customer
The following shall be provided by the customer:
a) stabilizer type: drill stem or near-bit,
b) integral or welded,
c) stabilizer (blade) diameter,
d) wrap: tight spiral, full spiral, open spiral or straight, and
e) neck size and connection.
1.7.2 Optional Requirements
The following may be required by the customer:
a) connection stress relief features, in accordance with API 7-2,
59
Rotary Drill Stem Elementsb) connection cold working,
c) connection surface treatment (optional for non-magnetic only),
d) non-magnetic,
e) abrasion protection type,
f) left hand spiral, and/or
g) float valve recess on near-bit stabilizer.
1.8 Marking
The following information shall be marked on a marking recess with steel stamps or milled lettering a minimum of
6 mm (0.25 in.) in height; this recess shall be located on the upper neck within 101.6 mm (4 in.) of the stabilizer
blades, as shown in Figure 15.
a) Manufacturer name or mark
b) Blade diameter (add “NM” for a non-magnetic stabilizer)
c) “API 7-1”;
d) Upper Connection size and style
e) Internal diameter
f) Serial number
g) Lower Connection size and style
EXAMPLE 1—A 447.7 mm (17-5 / 8 in.) stabilizer, with 76 mm (3 in.) bore, manufactured by AB Company, is
stamped:
— AB Co. (or mark) 447.7, API 7-1;
— 6-5 / 8 REG, 76, Serial No., 6-5/ 8 REG; or— AB Co. (or mark), 17-5/ 8 , API 7-1;— 6-5/ 8 REG, 3, Serial No. 6-5/ 8 REG.
EXAMPLE 2—A 209.5 mm (8-1/ 4 in.) non-magnetic stabilizer, with 71.4 mm (2-13/ 16 in.) bore, manufactured by AB
Company, is stamped:
— AB Co. (or mark), 209.5 NM, API 7-1;
— NC50, 71.4, Serial No. NC50; or
— AB Co. (or mark), 8-1 / 4 NM, API 7-1;
— NC50, 2-13/ 16, Serial No. NC50.60
API Specification 7-1