GOST 8965-75 Steel Connecting Parts with Cylindrical Thread for Pipelines P=1.6 MPa.

GOST 8965-75 establishes requirements for steel connecting parts with cylindrical thread for pipelines with a working pressure of P = 1.6 MPa.

The standard applies to steel connecting parts with and without zinc coating, with cylindrical thread, intended for joining water-and-gas pipes using a sealant in heating, water-supply, gas-supply and other systems operating in non-aggressive media (water, saturated steam, combustible gas, etc.) at a medium temperature not exceeding 175 °C and a pressure of P = 1.6 MPa.

1. Range

The following range of connecting parts for pipelines is established.

STEEL CONNECTING PARTS WITH CYLINDRICAL THREAD FOR PIPELINES P = 1.6 MPa. Specifications Pipe steel connections with cylindrical thread for pipelines P = 1.6 MPa. Specifications	GOST 8965-75 Supersedes GOST 8964-59 and GOST 8965-59

Name of connecting part	Designation of the standard for basic dimensions	Nominal bore Dy, mm
Straight coupling	GOST 8966-75	8, 10, 15, 20, 25, 32, 40, 50, 65, 80, 100, 125, (150)
Nipple	GOST 8967-75	8, 10, 15, 20, 25, 32, 40, 50, (65), (80), (100)
Lock nut	GOST 8968-75	8, 10, 15, 20, 25, 32, 40, 50, (65), (80), (100)
Running nipple	GOST 8969-75	15, 20, 25, 32, 40, 50, (65), (80)

Notes:

1. Connecting parts with the Dy values given in parentheses are made to customer order.

2. The weight of zinc-plated connecting parts is 4% greater than that of uncoated (black) parts.

2. Technical requirements

2.1. Connecting parts are made of readily weldable steel per GOST 380-71 and GOST 1050-73.

2.2. The surface (external and internal) of connecting parts must not have cracks, laps or blowholes. Surface defects are permitted (on the faces of the lock nut — sink marks from stamping on the surface opposite the bearing surface, roll marks, scratches from clamping prisms and dies of the threading tool, etc.), provided they do not take the wall thickness beyond the permissible deviations. To blunt sharp edges, connecting parts may be processed in tumbling drums before threading.

2.3. The zinc-plated external and internal surfaces must have a continuous, even zinc coating (the thread and end faces are not zinc-plated) free of spots, blistering and oxide film inclusions. Slight roughness and local runs are permitted on the external and internal surfaces, but the coating must not flake off the base metal. Yellow or dark spots are permitted on the internal surface with a total area of not more than 5% of the entire internal surface.

2.4. The thread of connecting parts is made per GOST 6357-81 (grade B); chamfering of the internal thread is per GOST 10549-80. A reduction in profile height at the crest is permitted, but by not more than 15%.

Note. By agreement between the customer and the manufacturer, if 100% tumbling is performed before threading, additional chamfering is not required.

2.5. A reduction of up to 10% in the effective thread length (excluding the run-out) is permitted on the external thread.

2.6. Within the effective thread length, threads with incomplete or torn profile are permitted, provided their total length does not exceed 8% of the required thread length.

2.7. The deviation between axes of running nipples must not exceed 1°.

2.8. In couplings, both end faces, and in lock nuts, one end face on the chamfer side, must have a surface roughness parameter of Rz ≤ 320 μm per GOST 2789-73 and be perpendicular to the thread axis. Deviations must not exceed 1°.

2.9. The end faces of running nipples and nipples must be perpendicular to the bore axes. The deviation must not exceed 1°.

2.10. Permissible deviations for the overall lengths of connecting parts:

± 1.5 mm — for lengths up to 50 mm;

± 2.0 mm — for lengths over 50 to 100 mm;

± 2.5 mm — for lengths over 100 to 200 mm.

3. Acceptance rules

3.1. Connecting parts are submitted for acceptance in lots. A lot must consist of connecting parts of one size and one steel grade and must be accompanied by a single quality document per GOST 10692-80. The lot weight must not exceed 1 t.

3.2. Product units for quality inspection are selected by random sampling from different points in the lot.

3.3. Every connecting part in the lot is subject to visual inspection. For the visual inspection of connecting parts made from pipes that have undergone 100% non-destructive physical quality testing or a 100% hydraulic test, not less than 1% of the connecting parts in the lot are selected.

3.4. For checking thread dimensions, not less than 40 connecting parts are selected from the lot.

3.5. For checking the perpendicularity of the end face to the bore axis, the coaxiality of the thread axes, the outside diameter and the length, not less than 10 connecting parts are selected for each type of test.

3.6. For checking the quality of the zinc coating (thickness and continuity), not less than 5 connecting parts are selected from the lot.

3.7. For checking the strength of connecting parts, not less than 1% of the connecting parts in the lot are selected.

3.8. If unsatisfactory test results are obtained for at least one parameter, repeat testing for that parameter is performed on a doubled sample. The results of the repeat tests apply to the entire lot.

4. Test methods

4.1. Inspection of the surface (external and internal) is performed visually.

4.2. Checking of thread dimensions with a go gauge is performed per GOST 1623-61. When checking the thread with a no-go plug gauge, the engagement must be not less than 3.5 turns, and for lock nuts, not more than one turn.

4.3. Checking of the coaxiality of the thread axes and the perpendicularity of the end face to the bore axis is performed per GOST 24642-81 and GOST 24643-81.

4.4. Connecting parts (except lock nuts) are tested for strength under a test hydraulic pressure per GOST 356-80 for the time needed for inspection, but not less than 2 minutes.

Note. Connecting parts made from pipes that have undergone 100% non-destructive physical quality testing or a 100% hydraulic test are not subjected to test hydraulic pressure after manufacture.

4.5. The quality of the coating on zinc-plated connecting parts is checked per GOST 3262-75 or GOST 9.302-79, depending on the coating application method.

5. Marking, packaging, transportation and storage

5.1. Marking, packaging, transportation and storage of steel connecting parts are per GOST 10692-80.

5.2. Uncoated connecting parts and the threads of zinc-plated connecting parts must be protected against corrosion during transportation.