Pipe-thread joints

B. Pipe Joints. Good joints suitable for vacuum or pressure applications can be made by means of tapered pipe thread joints in heavy-walled tubing. Unlike all of the joints discussed so far, the seal is made in the threads of this joint. The threaded portions of both the male and female pipe joint are tapered, and as a result the inner and outer threads are wedged into each other when they are screwed together (Fig. 10.9). To achieve a good seal the male pipe threads are wrapped with two layers of Teflon pipe tape, which serves the role of sealant and... 

Fig. 10.9. Normal pipe threaded joint. Note the tapered threads on both the male and female components. Unlike most other joints, the seal is formed in ihe threaded portion of the joint.

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. 

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-... 

Another material used on pipe threads is sealant tape. This tape, which is made of Teflon, provides an effective means of sealing pipe connections and eliminates the necessity of torquing connections to excessively high values in order to prevent leaks. It also provides for ease of maintenance whenever it is necessary to disconnect pipe joints. The tape is applied over the male threads, leaving the first thread exposed. After the tape is pressed firmly against the threads, the joint is connected. 

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. 

Technical Drawings—Dimensioning-General Principles, Definitions, Methods of Execution, and Special Indications Pipe Threads Where Pressure-Tight Joints are Not Made on the Threads—Part I Designation, Dimensions and Tolerances ... 

The susceptibility of the piping material to crevice corrosion under backing rings, in threaded joints, in socket-welded joints, and in other stagnant, confined areas. 

Straight Pipe Threads These are confined to light-weight couplings in sizes 2 in and smaller (Fig. 10-132). Manufacturers of threaded pipe ship it with such couplings installed on one end of each pipe. The joint obtained is inferior to that obtained with taper threads. The code limits the joint shown in Fig. 10-129 to 1.0 MPa (150 Ibftin ) gauge maximum, nontoxic fluids. 

ISO 7, Pipe threads where pressure-tight joints are made on the threads. 

Piping for LNG service is connected via threaded joints, flanged connections, swaged fittings, or welded connections. Welding provides the most secure connection and should be used whenever possible. Flanged connections are suitable and should be used where welded connections cannot. Threaded connections... 

In a hood, 211 g. of powdered phosphorus(V) chloride (1.01 mols) is intimately mixed with 75 g. of powdered phosphorus ) sulfide (0.338 mol) in a 500-ml. beaker. This mixture is then transferred to the lecture bottle. Use of a 150-mm. short-stemmed funnel and a stirring rod facilitates this transfer and keeps the pipe threads clean. After treatment with pipe-joint compound, the pipe plug is screwed into place. (A satisfactory pipe-joint compound can be made by grinding litharge and glycerol together.)... 

Thermocouples often come with pipe threads for attaching onto vacuum systems. Avoid using these pipe joints entirely by attaching a thermocouple to a glass system by silver soldering the thermocouple to a premanufactured glass-to-metal seal. 

Metal tubing is often terminated in a pipe thread. This is an accurately tapered and threaded unit, and an assembly must be well tightened with a pair of wrenches in order to seat the joint. Small leaks can be sealed by wrapping the inner member with a thin film of Teflon tape, available as Teflon Tape (du Pont) or Tape Dope, before assembling the joint. 

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