Seam joint

All ductwork should be sealed in accordance with SMACNA Class A rating, which requires all seams, joints, fasteners, penetrations, and connections to be sealed. Sealant should be FDA acceptable for the application, and nonhydrocarbon based. Leakage rates as low as 1% total airflow are not uncommon. All ducts passing through a clean room wall or floor should be provided with stainless steel sheet metal collars and sealed at the opening. Details of sealing methods should be provided on the design documents. 

Built-up containers consist of at least two components, namely a base and a side wall, which are mechanically secured together by a seamed joint. With the exception of aluminium extruded bodies, the side wall itself also involves a seam. Frequently a third component is affixed permanently to the side wall and it is this extra component which accommodates the closure itself. 

Joints must then be sealed with an elastomeric sealer in order to prevent seepage through the seam or crack. To seal control joints and cracks, a chemically resistant joint sealer is applied in the seam joint. There are many different sealant materials and specifications for installation which should be considered at the design stage. 

Spiral butt welded pipe is being increasingly used in Europe. This product must not be confused with spiral welded pipe to ASTM A211, which may be lap or lock-seam jointed. The European material... 

This method is used for local examination of sections of seam joints. The surface of the specimens must first be cleaned and degreased. Then a penetrant solution is applied along the joint. Capillary action pulls the solution into any defect open to the surface. The penetrant on the surface is rinsed with a solvent, leaving the penetrant in the defects. A developer is then applied to draw back the penetrant to the surface. Because the penetrants are brilliantly colored, each defect is easy to see. ... 

More and more processes use microwaves for heating and drying. Maintenance personnel need a handheld microwave leakage detector to test seams, joints, and door seals to locate microwave leakage. The unit of measurement of microwave radiation is miUiwatts per square centimeter (mW/cm ). 

The characteristics of connecting constructions that form the concept lead to a four-step order matrix for seam joints. Explanations of the characteristics and the access component are given for permanent seam junctions to convey an impression of the variety of the joining technologies in sewing. 

The adhesives (qv) used to form tube seams and bag bottoms include unborated dextrin, borated dextrin, casein, latex—casein, latex, poly(vinyl acetate), vinyl acetate copolymers, and hot-melt materials (10,27). Dextrin and casein adhesives are more commonly used in the production of grocery sacks vinyl acetate-type adhesives are commonly used in ah paper multiwah bags. The hot-melt adhesives are typicahy used to tack the phes of the multiwah bag together and to form the seam and bottom joints when polymer film phes or coated paper phes are used in bag constmction. 

Weak roof-to-shell attachment for fixed roof tanks, as per API-Std-650 for Welded Steel Tanks for Oil Storage. The joint fails and excess pressure can be relieved (above the normal design provided). Such tanks do not require additional emergency vent equipment however, it can be provided in order to prevent the roof seam failure with its attendant replacement/ maintenance requirements. This type can only be used outside of a building, not confined. 

Horizontal cylindrical tanks should be installed on brick or reinforced concrete cradles with a downward slope of 1 in 50 from the draw-off end towards the drain valve, as shown in Figure 18.1. Cradles should be constructed on foundations adequate for the load being supported and the type of soil. A reinforced concrete raft equal to the plan area of the tank, and of adequate thickness to bear the load, is normally suitable for all but the weakest soils. Cradles should not be placed under joints or seams of the tank plates and a layer of bituminized felt should be interposed between the cradle and tank. The height of the tank supports should provide at least 450 mm space between the drain valve and ground level to allow access for painting or draining the tank. 

Some of the ultrasonic systems include ultrasonic transmitters that can be placed inside plant piping or vessels. In this mode, ultrasonic monitors can be used to detect areas of sonic penetration along the container s surface. This ultrasonic transmission method is useful in quick checks of tank seams, hatches, seals, caulking, gaskets or building wall joints. 

The design of pipework has to be such as to allow access to welds and bends for weld and surface preparation. It is preferable to use seamless tubing conforming to BS 806 1986. Where this is impractical, tubing in accordance with BS 1387 1985 is acceptable provided that the butt-welded joint seam does not restrict the bore by more than 0-25 mm. 

Effects of processing on the properties of the snap joints (orientation of the molecules and of the filler, distribution of the filler, binding seams, shrinkage, surface, roughness and structure)... 

Most builders use 4 in. schedule 20 PVC pipes. Other sizes can be used but 4-in. PVC is readily available and is commonly used by builders for other purposes. Fans made for use in subslab systems are available in a variety of sizes from many vendors. The fans normally used are rated in a range of 90-150 cfm at no static pressure. Manufacturers of fans used for radon reduction are fairly quick to improve their products on advice from the people who are using their products. When the radon industry first started, many of the fans leaked at seams and joints, and required disassembly of the fan to seal those openings. Most manufacturers now supply fans that do not leak, but builders should be aware that this problem did exist and may still exist in some fans. 

No. Type of Joint Type of Seam Examination Factor, 5... 

There are several methods of layering in common use ( ) thick layers shrunk together (2) thin layers, each wrapped over the other and the longitudinal seam welded by using the prior layer as backup and (3) thin layers spirally wrapped. The code rules are written for either thick or thin layers. Rules and details are provided for all the usual welded joints and nozzle reinforcement. Supports for layered vessels require special consideration, in that only the outer layer could con-triDute to the support. For lethal service only the inner shell and inner heads need comply with the requirements in Subsec. B. Inasmuch as radiography would not be practical for inspection of many of the welds, extensive use is made of magnetic-particle and ultrasonic inspection. When radiography is required, the code warns the inspector... 

The different methods to produce mulitlayer shrink-joints are based on the thermal contrac tion of welding seams, as well as the mechanical tension and thermal contraction during strip-wire- or coil-winding after cooling down. Fig. 4.3-4 D shows the ideal distribution of residual... 

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