China Vigor Drill Collar

1. Size

Standard steel drill collars shall be furnished in the sizes and dimensions shown in Table 14 and illustrated in Figure 8.

1.1 Outside diameter tolerances

The outside diameter shall comply with the tolerances of Table 15.

1.2 Bores

All drill collar bores shall be gauged with a drift mandrel 3,05 m (10ft) long minimum. The drift mandrel shall have a minimum diameter equal to the bore diameter, d (see Table 14), minus 3,2 mm (1/8 in).

2. Surface finish

The minimum external surface finish shall be hot-rolled and mill-finished. Workmanship shall comply with ASTM A 434. Surface imperfection removal shall comply with Table 16.

3. Straightness?

The external surface of drill collars shall not deviate from a straight line extending from end to end of the drill collar, when the straight line is placed adjacent to the surface, by more than 0,5 mm/m (1/160 in/ft) of drill collar length.

EXAMPLE

On a drill collar of length 9,14 m (30ft), the maximum permitted deviation from a straight line is 9,14 × 0,5 = 4,6 mm (30 × 1/160 = 3/16 in).

4. Non-destructive examination?

Each bar or tube used to manufacture drill collars shall be examined for both surface and internal defects in accordance with Clause 10 of this part of ISO 10424.

5. Connections

Standard steel drill collars shall be furnished with box-up and pin-down connections in the sizes and styles stipulated for the OD and ID combinations listed in Table 14. The connections shall conform to the dimensional and gauging requirements of API Spec 7.

5.1. Connection stress-relief features

Stress-relief features are optional. If stress-relief features are specified, they shall conform to the dimensions specified in API Spec 7.

The surfaces of stress-relief features shall be free of stress risers such as tool marks and steel stencil impressions.?

Laboratory fatigue tests and tests under actual service conditions have demonstrated the beneficial effects of stress-relief contours at the pin shoulder and at the base of the box thread. It is recommended that, where fatigue failures at points of high stress are a problem, stress-relief features be provided.

The boreback design is the recommended relief feature for box connections. However, the box relief groove design has also been shown to provide beneficial effects. It may be used as an alternative to the boreback design.

Stress-relief features cause a slight reduction in the tensile strength of the pin and the section modulus of the connection. However, under most conditions this reduction in cross-sectional area is more than offset by the reduction in fatigue failures. If unusually high tensile loads are expected, calculations of the effect should be made.

5.2. Cold working of thread roots

Cold working of thread roots is optional. The method of cold working is at the discretion of the manufacturer.

As with stress-relief features, laboratory fatigue tests and tests under actual service conditions have demonstrated the beneficial effects of cold working the thread roots of rotary shouldered connections. It is recommended that, where fatigue failures at points of high stress are a problem, cold working be provided.

If threads are cold-worked, they shall be gauged to API Spec 7 requirements before cold working.

Gauge standoff will change after cold working of threads, and can result in connections that do not fall within the specified ISO gauge standoff if gauged after cold working. This does not affect the interchangeability of connections and improves connection performance. It is therefore permissible for a connection to be marked as complying with the requirements of API Spec 7 if it meets the standoff requirements before cold working. In such event, the connection shall also be stamped with a circle enclosing “CW” to indicate cold working after gauging. The mark shall be located on the connection as follows:

a) pin connection: at the small end of the pin;

b) box connection: in the box counterbore.

5.3. Low torque feature

If the 8 5/8 Reg connection is machined on drill collars with OD larger than 266,7 mm (10 1/2 in), the faces and box counterbores shall conform to the dimensions for low torque feature as specified in API Spec 7.

5.4. Slip and elevator grooves

Slip and/or elevator grooves are optional. If they are specified, they shall conform to the dimensions shown in Table 21 and Figure 9. It is permissible to specify only the slip groove or only the elevator groove, rather than both. Location and dimensions of single features shall be in accordance with Figure 9.

5.5. Gall-resistant treatment of threads and sealing shoulders

A gall-resistant treatment of zinc or manganese phosphate shall be applied to the threads and sealing shoulders of all end connections of drill collars manufactured from standard steel. Application of the treatment shall be after completion of all gauging. The treatment type shall be at the discretion of the manufacturer.

Gall-resistant treatments are not readily available for non-magnetic drill collars, therefore are not required.

6 Mechanical properties

6.1 Tensile requirements

The tensile properties of standard steel drill collars, as manufactured, shall comply with the requirements of Table 17.

These properties shall be verified by performing a tensile test on one specimen per heat per heat-treatment lot.

Tensile properties shall be determined by tests on cylindrical specimens conforming to the requirements of ISO 6892, 0,2 % offset method.

NOTE For the purposes of this provision, ASTM A 370 is equivalent to ISO 6892.

The tensile specimen may be taken from either end of the bar or tube. The specimen shall be machined so that the central point of the gauge area is located a minimum of 100 mm (4 in) from the end of the bar or tube. The tensile specimen shall be oriented in the longitudinal direction, with the centreline of the specimen located 25,4 mm (1 in) from the outside surface or mid-wall, whichever is closer to the outside surface.

6.2 Hardness requirements

In addition, a hardness test shall be performed on each drill collar as prima facie evidence of conformation. The hardness test shall be made on the OD of the drill collar (Brinell hardness in accordance with ISO 6506-1 is preferred although Rockwell C hardness is an acceptable alternative). The hardness number shall conform to the requirements of Table 17.

NOTE For the purposes of this provision, ASTM A 370 is equivalent to ISO 6506-1.

6.3 Impact strength requirements

Charpy V-notch impact tests shall be conducted on specimens conforming to the requirements of ISO 148 and shall be conducted at a temperature of 21 °C士3°C (70 °F士5 °F). Tests conducted at lower temperatures that meet the requirements stated in 8.2.1.3.4 are acceptable.

NOTE For the purposes of this provision, ASTM A 370 and ASTM E 23 are equivalent to ISO 148.

7 Specimens

One set of 3 specimens per heat per heat-treatment lot shall be tested.

Specimens shall be taken at 25,4 mm (1 in) below the surface or at mid-wall, whichever is closer to the as heat-treated outer surface.

The specimens shall be longitudinally oriented and radially notched.

7.1 Specimen size

Full size (10 mm x 10 mm) shall be used except where there is insufficient material, in which case the next smaller standard subsize specimen obtainable shall be used.

If it is necessary to use subsize test specimens, the acceptance criteria shall be multiplied by the appropriate adjustment factor listed in Table 2. Subsize test specimens of less than 5 mm are not permitted.

7.2 Acceptance criteria

The average impact strength of the three specimens shall be 54 J (40ft-lbs) or greater, with no single value less than 47 J (35ft-lbs).

8 Marking

Standard steel drill collars conforming to this part of ISO 10424 shall be die-stamped on the drill collar OD with the following information:

a) the manufacturer's name or identifying mark;

b) outside diameter;

c) bore;

d) connection designation;

e) “ISO 10424-1”

NOTE The drill collar number consists of two parts separated by a hyphen. The first part is the connection number in the NC style. The second part, consisting of 2 (or 3) digits, indicates the drill collar outside diameter in units and tenths of inches. Drill collars with 209,6 mm, 241,3 mm and 279,4 mm outside diameters are shown with 6 5/8, 7 5/8 and 8 5/8 REG connections, since there are no NC connections in the recommended range of bending-strength ratios.

EXAMPLE 1 ??A drill collar of diameter 158,6 mm (6 1/4 in) with 71,4 mm (2 13/16 in) bore and NC46 connections, manufactured by A B Company, shall be stamped:

AB Co. (or mark)???NC46-62 ???71,4 ????ISO 10424-1

EXAMPLE 2 ??A drill collar of diameter 209,6 mm (8 1/4 in) with 71,4 mm (2 13/16 in) bore and 6 5/8 Reg connections, manufactured by A B Company, shall be stamped:

A B Co. (or mark)???209,6 ?????71,4?????6 5/8 REG?????ISO 10424-1