Threaded joints

The Research-Production Company (RPC) Zond (city of Ivano-Frankivsk) now is a well-known centre for development, fabrication and introduction of the technologies and methods of NOT of oil and gas equipment and tools Its experts developed and introduced the technologies and equipment which enables control of the drill pipes, especially their threaded joints, oil and gas equipment, sort out the pipes into groups by the strength and yield point of the pipes material, etc. 

Production of carbon electrodes is a capital-intensive business. Two suppHers dominate the prebaked market. Carbon paste producers are more numerous and tend to serve local markets. There is no international standard for the threaded joints on carbon electrodes. Manufacturers of straight pin carbon electrodes have followed the physical specifications adopted for graphite electrodes (37). Unified standards do not exist for pinless joints resulting in limited interchangeability among brands. Electrode diameters are offered in both English and metric sizes with no restrictions on new or unique diameters. 

Threaded Joints Pipe with taper-pipe-thread ends (Fig. 10-128), per ANSI B2.1, is available 12 in and smaller, subject to minimum-wall limitations. Fittings and valves with taper-pipe-thread ends are available in most pipe metals. 

When both components of a threaded joint are of weldable metal, the joint may be seal-welded as shown in Fig. 10-130. Seal welds may be used only to prevent leakage of threaded joints. They are not considered as contributing any strength to the joint. This type of joint is limited to new construction and is not suitable as a repair procedure, since pipe dope in the threads would interfere with welding. This method provides tight joints with a minimum of welding labor. When threaded joints used to join materials with widely dinerent coeffi-... 

API standards established three types of threaded joints ... 

Avoid threaded joints for materials that are far apart in galvanic series. 

The geometry of the structure, e.g. riveted plates, welded fabrications, threaded joints. 

In areas where the water has a high natural alkaline hardness, the potential for contamination of the steam and condensate system by C02 may be very significant. And in those plants requiring a high percentage of MU water, the risk of serious condensate system corrosion to the steel pipework, valves, traps, threaded joints, and points where noncondensable gases can collect is very real. 

Corrosion of steel by carbonic acid is probably the most common problem in the post-boiler section, producing pipe grooving and general metal wastage, especially in threaded joints. This form of corrosion is not self-regulating and the reaction products can produce more carbon dioxide, thus perpetuating the corrosion problem. Typically, the condensate pH level is depressed to around 5.0 to 5.5. 

IP-9.14(c) Typical Threaded Joints Using Straight Threads. 109... 

Seal welds shall cover all exposed threads. Seal welding of threaded joints shall not be used for liquid hydrogen service. 

Seal Welding. Seal welding taper-threaded joints should be considered for hydrogen gas inside buildings. Taper-threaded joints shall not be seal welded unless the composition of the metals in the joint is known and proper procedures for those metals are followed. Thread sealants shall not be used and the weld material shall cover the full circumferential length of the thread. 

Threaded joints in which the tightness of the joint is provided by a seating surface other than the threads, e.g., a union comprising male and female ends joined with a threaded union nut, or other constructions shown typically in Fig. IP-9.13(c), may be used. 

Pressure design of straight-threaded joints shall be based on calculations consistent with design requirements of this Code. These calculations shall be substantiated by testing in accordance with to-be-determined procedures and protocols. The testing shall consider such factors as assembly and disassembly, cyclic loading, vibration, shock, hydrogen embrittlement, thermal expansion and contraction, and other factors to be determined. 

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