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Back Gouging - The removal of weld metal and base metal from the other side (root side) of a weld joint. When this gouged area is welded, complete penetration of the weld joint is assured. Back Pressure Regulator – A pressure regulator which controls upstream (inlet) pressure. Similar in function to a relief valve. Balanced Poppet (Balanced Valve; Balanced Stem) – A valve which has been designed to be pressure balanced; hence the valve spring provides the shutoff force. Used essentially to reduce or minimize decaying inlet pressure effect. Balanced Wave - An alternating current waveform that has equal negative and positive polarity current values. Bevel Angle - An angle formed between a plane, perpendicular to the surface of the base metal and the prepared edge of the base metal. This angle refers to the metal that has been removed. Beveled Butt Joints - When a butt joint is to be made with sections too heavy topermit a square butt joint, the sections are beveled, or chamfered, to an angle of approximately 90°. The choice of a single or double bevel will depend upon the thickness of the metal and whether the sections can be welded from both sides. A double bevel uses approximately one-half the amount of weld metal required for a single bevel. The essential factor, in the preparation for welding, is that no part of the joint is left unwelded. This applies equally to single or double bevels. These drawings show the correct preparation of a joint for welding. The angle of the bevel will vary according to the base metal and the electrode or torch alloy used. The sections should be separated by a distance of 1/16” to 3/32” to allow the weld metal to flow through the joint without burning the base metal. Sections should never be beveled or chamfered to a knife-edge because the sharp edge will inevitably be burned. An important precautionary measure is to clean the metal adjoining the weld area for a distance of at least 2”. This prevents oxides or foreign matter contaminating the weld. Boiling Point – The temperature at which the vapor pressure of the liquid is equal to the prevailing pressure of the atmosphere. The normal boiling point is the temperature at which the vapor pressure of the liquid is 14.7 psia (1 atm). Bonnet (Spring Housing) – The part of a regulator which houses the control spring. Bourdon Tube – A curved metal tube, sealed at one end, which flexes to a known degree when pressurized internally. Brass – Copper/zinc alloys of varying composition. Some brass also contains low percentages of other elements such as manganese, aluminum, silicon, lead and tin. Bursting Disk (Frangible Disk) – A metal disk which is part of a safety device, and which is intended to burst and allow gas to escape within predetermined pressure limits to prevent rupture of the device it is installed on. Similar in function to a safety relief valve, except it has no reseal capability. Burst Pressure – A design test pressure which allows for permanent deformation and leakage, but parts must remain assembled (i.e., no sudden ruptures). Normal industry standard is 4 times (400%) of maximum oper-ating pressure. See also “Proof Pressure” and “Maximum Operating Pressure.” Bursting Disk (Frangible Disk)– A metal disk which is part of a safety device, and which is intended to burst and allow gas to escape within predetermined pressure limits to prevent rupture of the device it is installed on. Similar in function to a safety relief valve, except it has no reseat capability. Butt Joint - A weldment where the material surfaces and joining edges are in or near the same plane.
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