Blow holes

The results are illustrated by figure 5 B-Scan, C-Scan and D-Scan representations show that there are two types of defects. On the left part of the weld, we remark a lack of fusion, while on the right part, we observe a nest of blow hole. 

Seams. As a defect, a seam is distinct from the seam resulting from a welding process. Seam defects can be found in nonwelded (seamless) tubes. They can originate from blow holes or nonmetallic inclusions in the ingot and are caused by crevices that have been closed by some rolling process but remain unfused. At times, they will appear in a spiral pattern in tubes. Seams can be very tight and appear as hairlines on the surface. They can cause failure when the component is pressurized. 

Whether the brushes are set concentrically on the slip-rings, and each individtial brush holder is set approximately 2-2.5 mm from the slip-ring surface. Slip-rings must be concentric and free from damage and blow holes. 

Pfeife, /. pipe whistle fife (in blasting) blown-out shot (Metal.) pipe, also blow hole. 

Gunpowder, already in use in China, is introduced into Europe. At first it is used primarily in crude siege cannons that can blow holes in castle walls, enforcing the power of the monarch over the nobles. 

Sudden and explosive expansion of air occluded in blow-holes of castings and that trapped in tubes, closed piping, or hollow metal work when immersed in molten baths without pre-warming... 

The material shall be clean and of uniform compn, and shall be free from segregations, dross, oxides, blow holes, hard spots, foreign material and other injurious defects. The material shall be furnished in commercial cylindrical ingots of specified dimensions Refs 1) Gmelin, Syst Nr 47, Teil -3 (1970), 905ff 2) Spec, Lead-Antimony (For Use... 

Weld seams should be continuously smooth, and free from porosities and blow holes, projections and burrs. These should be smoothened out by grinding. See figure 4.2 below. 

The Stone Fiddle is an original stoneware instrument that is a hybrid of three instruments from different musical families. It is created as a two-stringed bowed instrument, similar to the violin and the Egyptian rebabba, while the neck of the fiddle serves as a flute. In the photograph you can see the flute s blow hole and finger holes on the side of the fiddle s neck. 

The velocity of the polymerization front is 0.065 - 0.18 mm/s, and the temperature of the polymer at the end of the process is about 170 - 180°C. The degree of crystallinity reaches 40 -50%. The newly formed polymeric slab has no cracks, blow holes or crazing. The mechanical properties of the material are homogeneous throughout the entire volume and are close to those of a material synthesized in a stationary mold. 

Carbon steel substrates must be sandblasted to a near-white metal finish (SSPC-SP10 or NACE 2) and maintained at least 5°F above the acid dewpoint during installation. Concrete surfaces must be free of any imperfections such as blow holes or honeycombing. Old concrete must be free of oil, grease or chemical contamination. 

This impurity must therefore be estimated. Furthermore, a high percentage of alumina seems to favour the formation of blow-holes. For these reasons, the melting up of aluminium scrap, more or less oxidised, gives poor results. 

The original or acid Bessemer process had, however, two disadvantages-.—(1) phosphorus and sulphur could not be removed owing to the reduction of their oxides by iron and, therefore, only special Bessemer pigs, free from phosphorus and very low in sulphur, could be used (2) the ingots produced contained blow-holes. Science overcame the first of these disadvantages. In 1879 Thomas and Gilchrist found... 

This was the result not only of scientific methods of research but of the direct application of a scientific principle, viz., that of using a basic lining and adding lime, a basic material, to retain the acidic substances produced by the oxidation of phosphorus and sulphur. The second problem, however, was solved by tho empirical discovery that the addition of a very small quantity—5 to 8 oz. per ton—of aluminium to the molten metal minimised the formation of blow-holes. 

This high MW polypropylene oxide) (PPO) is a very dangerous contaminant. The polyether polyols obtained by using a PO with a content of high MW PPO (higher than 0.3-1 ppm), lead in the foaming process to very undesirable phenomena the foam collapse with a low foam rise and substantial blow hole formation. 

In order to avoid these extremely dangerous phenomena, methods of treatment of PO with adsorbents (active carbon, charcoal, attapulgite, diatomaceous earth) were devised. By the treatment at room temperature of PO with these adsorbents (0.1-1% adsorbent in liquid PO), after a short contact time of about 15 minutes the high MW polyether is almost quantitatively retained by adsorption. The PO resulting after the filtration of the solid adsorbent is practically free of high MW polymers, and the polyethers obtained with the treated PO can be used to manufacture resilient flexible foams which will not collapse, with high rise and free of blow hole formation. 

In conclusion, to obtain a good, resilient, flexible PU foam without collapse, with high rise and free of blow holes, it is necessary that the PO used for the polyether synthesis be free of high MW PPO contaminants. 

Aluminium is used in electric transmission in place of copper it is added to molten steel prior to casting to prevent blow holes. It... 

Key AD Accidental damage BH Blow hole Cg Crazing Cr Crack Cv Cavity... 

United States and Canada also apply them. Membranes come as two main types, a liquid that solidifies in place, and a sheet that is stuck to the concrete (see Section 5.3.3). The main problem with waterproof membranes is similar to that of epoxy coating rebars they must be applied without defects. Defects can occur as blow holes, penetrations or mechanical damage to the liquid applied types, or cuts, tears, bad joins or perforations in the sheets. Either type of membrane can be damaged by the overlay of asphalt, either by its heat or mechanical damage from the aggregate particles. 

GRP), where surface defects can cause blow holes in the paint coating during stoving. 

Polymeric aerogels based on RF were developed in the last years for application in foundry practice as a new nanostructured binder for foundry sands. Their properties allow, for instance, to replace conventional polymeric binders, since they solve certain problems of core removal, penetration, surface reactions, blow holes, and other casting defects especially in light metal casting. RF aerogels as polymeric binders are at the verge of being used by industry. 

Since vents leave a hole in the molded parts, correct placement is essential. They should he located in an area that may he cut out of the finished product or where a patch does not impair appearance. Vents must also be so located as to prevent water from entering the product while it is in the cooling cycle, because this may leave a water-track mark on the inside of the hot article. Improper venting can cause problems, such as blow holes in the parting line. 

After the fluxing step, the drcuit board passes through the preheat stage, which is comprised of a set of radiant heaters. As the circuit board is heated, this step evaporates volatiles from the flux coating (which if not adeqnately removed can lead to voids and blow holes) and activates the chemical reactions between the flnx and oxides on the component lead or termination and the circuit board conductor. 

Don t worry. Zip," I replied. "Man proposes, but God disposes." And suddenly divine intervention came to our rescue in the form of Ron Stover. Ron had returned from the storehouse with a pair of insulated gloves, a screwdriver, and a handful of brass wood screws. Ron climbed up to the leak, stuck an appropriately sized screw into the blowing hole, and twisted the screw in. The leak stopped ... 

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