Power Engineering 2-A2 - Part 2 Graded A+ Correct Answers!!!

What is a Back weld? What is Backing? - ANS Back weld: A weld applied to the back side (root side) of a single groove weld AFTER the main weld has been completed. Purpose of this weld is reinforcement and fills where the main weld did not penetrate Backing: Applied to the back side of a single groove weld BEFORE the main weld is started. Its purpose is to fill the root opening and prevent melt through What is the purpose of Surfacing welds? - ANS - To increase the thickness of the of the surface for strengthening or anticipation of corrosion purposes. *No joining of pieces* What is an Edge Weld? - ANS - Used to join 2 pieces along their adjacent, exposed edges What is the purpose of the reference line on a Welding Symbol? - ANS - Contains any tags, symbols, notations that describe the type, dimensions, location of the weld. Purpose of the Arrow on a welding symbol? - ANS - Joins the reference line to the joint at which the weld will be applied. - Stem should not be horizontal Direction that the arrow points (up or down) in a welding symbol is irrelevant. True or False? - ANS True What is the purpose of the Tail in a welding symbol? - ANS - Attached to the opposite end of the arrow and contains supplemental information that is necessary for the welder to know; information that isn't included in the reference line is contained here The tail of a welding symbol is optional and may be left off. True or False? - ANS True The arrow side and the reference line are important pieces of information for what reason? - ANS These 2 things inform the welder which side of a joint the weld must be applied to Any information BELOW the reference line must be applied to the ARROW side of the joint. True or False? - ANS This is true. Any information located ABOVE the reference line is applied to the OTHER side of the joint. BELOWARROW ABOVEABOTHEROTHER Weld symbol for Melt Through? - ANS - Root weld that extends beyond the surface at the bottom of a groove weld - Solid black half dome symbol - *always placed above the reference side because it always occurs on the OTHER side* Weld symbol for a Field Weld? - ANS - A black flag pointing away from the arrow indicates a weld that has to be performed in its final location (not in a shop) Symbol for an 'All Around Weld'? - ANS - A circle at the end of a reference line Weld symbol for Backing? - ANS - Rectangular hollow box above the reference line which indicates a flat surfaced piece is to be placed on the back side of a root weld. This piece normally remains in place Weld symbol for a Spacer? - ANS - A rectangular box that straddles the reference line. - Spacers are used in between the members of a groove weld (butt joints). It acts as backing and keeps the joint root open during welding Weld symbol for a Consumable Insert? - ANS - SQUARE box placed on top of the reference line - Indicates a filler material should be used to the weld joint to add strength 3 possible symbols for Weld Contour? - ANS - Either a flat, convex or concave line is placed above the reference line. If the weld can't be completed with the desired contour naturally then machining or grinding may be necessary Information that can be contained on the reference line for Groove Weld Symbols? - ANS - In addition to the basic weld symbol, information like specific sizing and shaping of the joint surfaces, depth of penetration, use of backing, thickness of melt-through, etc. may also be included. Welding symbols for fillet welds include what information? - ANS - Location of the weld - Size of the weld - Surface finish required For lap (fillet) weld symbols, which side is the vertical ALWAYS on? - ANS - Vertical side is always on the left; angled side is always on the right. "3 - 5" What would these numbers mean in a welding symbol? - ANS - Staggered or in line welds where the individual welds are 3" long and the pitch distances are 5" apart (centre to centre) Mechanical vibrations can be propagated only in solid objects. True or False? - ANS False, these sound waves can be detected in solids, liquids and gases. Sounds wave range that is audible to the regular human ear? - ANS 10 Hz - 20 000 Hz. Above 20 000 Hz is considered ultrasonic. What is the Ultrasonic Principle based on? - ANS - Based on the fact that solid materials are good conductors of sound waves. - These sound waves are reflected at interfaces within the object as well as internal flaws (material separations/inclusions) What is the basic for Ultrasonic Testing? - ANS - Electrical pulses are transferred to mechanical vibrations and the conversion of returned mechanical vibrations back into electrical energy Electrical InputMechanical VibrationsElectrical Output Transducer converts what types of energy in Ultrasonic testing? - ANS Electrical energy to Acoustic energy, and vice versa Quartz crystal in an example of a polarized material. What is meant by polarized material? - ANS - Contains molecules that are positively and negatively charged. 2 electrodes are connected to each polarity in Ultrasonic testing equipment What is Electrostriction? - ANS - When an electric field is applied to a piece of polarized material (quartz crystal, Barium titanate) the polarized molecules align themselves with the electric field producing induced DIPOLES within the molecular/crystal structure - the alignment causes the material to change dimensions Piezoelectric effect? Inverse Piezoelectric effect? - ANS 1) Imposed mechanical force on a polarized material will induce a mechanical field within that material 2) Electrical energy applied to a piece of polarized material will induce mechanical force and create measurable stresses to that piece of material. Operating principle of a Ultrasonic Testing machine? - ANS - High voltage energy is applied to a piece of piezoelectric material attached to the test specimen. Ultrasonic waves transmit through the test specimen and rebound off a second piece of piezoelectric material. The rebounded ultrasonics are measured The time interval between the transmitted and reflected pulse's in a Ultrasonic test is a measure of distance to where the discontinuity is located. True or False? - ANS This is True. Furthermore, the intensity of the return pulse is a measure of the size of the flaw. The higher the frequency of the transducer, the smaller the discontinuities can be discovered with Ultrasonic testing. True or False? - ANS True Larger transducer produce more power output which permit the inspection of thicker specimens. True or False? - ANS True. Single crystal transducer act as the sending and receiving unit. True or False? - ANS True What is a Paintbrush Transducer? - ANS - Detects defects in specimens with a large surface area. If a defect is detected, a smaller transducer is used to find the specific location and size. - Transducer is approx. 150 mm wide Orientation determines the angle at which transducer pulses strike the specimen. How would you test longitudinally? How would you create a shear wave? - ANS - To test longitudinally, the transducer is located flat on the specimen - To create a shear wave, the pulse must enter the specimen at the desired angle by mounting the transducer on a plastic wedge which is part of the probe As long as opposing surfaces are parallel, when a transducer is aimed 90 degrees into the surface of an object, the pulse signals should rebound directly back to the transducer. True or False? - ANS True Refraction and Ultrasonic testing? - ANS - The pulse signals will refract when angled into a surface - Transducer is angled on a wedge until 2 waves are produced; a longitudinal wave and a shear wave - The critical angle is when 1 wave is 100% parallel to the surface and the other wave is still at the shear angle