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What are 'Toe Cracks' in welds? - correct answer ✔✔- Occur when the face of the weld terminates at the surface of the parent metal
- Thermal stresses are very high at this point and cracking often occurs in a direction normal to the parent What is 'Underbead Cracking' as a welding defect? - correct answer ✔✔- Occurs in either the weld or the heat affected zone Lamellar Tears? - correct answer ✔✔- Cracks that occur due to high restraint and high residual stress
- They appear on the interface of the weld and the base metal, or completely in the base metal Planar type defects, such as cracks and lack of fusion, pose high risk for metal failure. Pores and non-metallic inclusions on the other hand, are rounded and pose less of a potential for failure. True or False? - correct answer ✔✔True. What are the 3 types of defects that NDE testing is used for in the pressure equipment industry? - correct answer ✔✔1) Inherent defects: defects that are created during the initial production of the material
- Processing Defects: defects created in the metal during the construction of the pressure equipment
- Service Defects: defects created during the service of the equipment 4 most common types of NDE testing? - correct answer ✔✔- Liquid Penetrate Testing
- Magnetic Particle Testing
- Radiographic Testing
- Ultrasonic Testing
What is a prerequisite for a material to be tested using Liquid Penetrate testing? - correct answer ✔✔- Flaws must be open to the surface
- The examined surface cannot be rough or porous, since these conditions interfere with the PT inspection What is Capillary Action, and how does it relate to Dye Penetrate testing? - correct answer ✔✔- Cohesive forces between the liquid and the straw are greater than the cohesive forces within the liquid itself Other than Capillary Action, what is another principle that affects Penetrate Testing?
- correct answer ✔✔- The ability of the liquid to migrate and wet over the surface of the material
- Migration depends on the surface tension and contact angle of the material The liquid penetrant must not only be able to penetrate the material, but also withdraw from the material after inspection. True or False? - correct answer ✔✔True 4 types of possible materials Liquid Penetrant testing works for? - correct answer ✔✔Materials that are welded, cast, rolled or forged In brief, list the 6 major steps in Liquid Penetrant Testing. - correct answer ✔✔1) Pre Cleaning
- Penetrant application
- Excess Penetrant Removal
- Developer Action
- Inspection/Interpretation
- Post-Cleaning Cleaning surfaces before Liquid Penetrant Testing? - correct answer ✔✔- Use solvents or degreases to remove any contaminants 2 means of applying Penetrant (dye)? - correct answer ✔✔Spraying or Brushing
Magnetic Particle Testing can be used on ferromagnetic pressure components that are welded, cast, rolled or forged, and typical defects found are Lack of Penetration and Cracks. True or False? - correct answer ✔✔True. 6 general steps to Magnetic Particle Testing? - correct answer ✔✔1) Pre-cleaning the surface
- Magnetizing the component
- Applying the magnetic particles
- Interpretation
- Post-demagnetization of the component
- Post-Cleaning Magnetizing the test piece in a MT? - correct answer ✔✔- A longitudinal magnetic field is established by placing an electromagnetic yoke in contact with the test material and energizing the coil of the electromagnet Applying the magnetic particles in a MT? - correct answer ✔✔Dry Method: Dry Iron oxide particles are spread in the surface Wet Method: Magnetic Iron oxide particles are held in a carrier liquid, such as kerosene, and the liquid is sprayed or painted onto the surface Post-demagnetization of the component in a MT? - correct answer ✔✔- AC current is applied to the test piece after the defects have been marked
- De-magnetization is done with a special tool to prevent damage to moving parts, arc deflection during welding, interference with machining and interference with coating or painting Radiographic Testing identifies defects that are internal to the weld or base metal. True or False? - correct answer ✔✔True Principle behind Radiographic Testing? - correct answer ✔✔- Different amounts of penetrating radiation are absorbed in good material that in defective material
- Unabsorbed radiation passes through the test material and exposes film on the opposite side
X-rays v.s. Gamma rays? - correct answer ✔✔- Only differ in ways which they are produced
- X-rays: Produced when high speed electrons strike a metal target, causing a transfer of energy
- Gamma-rays: Emitted from the decay of radioisotopes, such as cobalt 60 and iridium 192 Benefits of using Radiographic Testing? - correct answer ✔✔- Can be used on all materials
- Best suited for detecting 3 dimensional internal flaws
- Useful for locating foreign objects stuck in hard to enter places
- Material thickness can be measured which can help to determine corrosion rates
- Most popularly used for weld examination Detecting Cracks and Flaws using Radiographic Testing? - correct answer ✔✔- Radiography will only detect cracks if they are PARALLEL to the radiation beam
- Flaws must be at least as large as 2% of the penetration thickness in order to be detected Most important consideration to take when using Radiographic testing? - correct answer ✔✔- Safety
- Large doses of x-rays or gamma rays are very harmful 4 major steps in Radiographic Testing? - correct answer ✔✔- Source Selection (x ray or gamma ray)
- Setting up
- Exposure of test component to radiation source
- Film development Setting up for a Radiographic Test? - correct answer ✔✔- About 60% of the test is spent on set-up
- Material should be cleaned and ground smooth
- Bursts Describe the procedure for Ultrasonic Testing using the REFLECTION process. - correct answer ✔✔- High frequency sound waves are generated by a transducer and moved over the tested surface area
- A thin film of liquid separates the test piece and the tester
- The transducer acts as the transmitter AND receiver
- Sound waves penetrate the material and give an indication of the intensity of reflection and the time to return to the transducer
- A high intensity indicates a defect and also gives an indication of the depth of the defect Describe the procedure for Ultrasonic Testing using the ATTENUATION process. - correct answer ✔✔- The transducer acts as the transmitter only, and a separate receiver is located on the opposite side of the material
- Sound waves pass through the material to the receiver and give an indication if there is defects present or not
- A reduction in received sound waves indicates a defect ASME Section IX (9) is divided in what 2 parts? - correct answer ✔✔1) QW - Requirements for Welding
- QB - Requirements for Brazing 2 reasons for establishing Section IX of the ASME codes? - correct answer ✔✔- Procedure Qualification
- Performance Qualification Purpose of the 'Procedure Qualifications' part of the ASME Section IX. - correct answer ✔✔- Procedure qualification determines if the material to be welded has the required properties for the intended application
- Tests evaluate the metallurgical and mechanical properties of the material, but not the SKILL of the worker performing the weld
- The welding procedure used must be qualified under code provisions
To qualify a welding procedure, what information must be submitted in order for it to pass the code? - correct answer ✔✔- Type of welding process
- Type of thickness of material to be welded
- Welding electrode specifications
- Method of material preparation
- Type of heat treatment to be used
- Test plates must be submitted which are subjected to tension and bend tests to prove their soundness What specific certificate must a Pressure Welder hold to perform work on boilers and pressure vessels? - correct answer ✔✔- Pressure Welders Certificate of Competency
- A performance qualification test must also be passed conducted by a boiler Inspector How long does a welders Certificate of Competency remain valid until it expires? - correct answer ✔✔2 years and then the individual apply to an accredited organization for re-testing 2 other reasons a welders performance certificate can expire? - correct answer ✔✔1) The individual has not welded with the process for 6 months or more
- Specific reasons exist to question the welders ability Performance qualification testing of welders must be in accordance with..? - correct answer ✔✔- Safety Codes Act "Pressure Welders Regulations"
- ASME Section IX - "Welding and Brazing Qualifications" What 2 components must be completed when conduction performance qualifications? - correct answer ✔✔1) Testing
- Documentation Testing and Documentation for pressure welders? - correct answer ✔✔- Must possess a Certificate of Competency before doing a performance qualification test
- Welding Procedures Specifications (WPS) test must be passes
Effects of pump Cavitation? - correct answer ✔✔- The impact of collapsing vapour voids can damage metal surfaces of the impellers and casing
- Noisy operation and vibration occurs Difference between Air Bubbles in a Liquid and Vapour Voids? - correct answer ✔✔- Air bubbles are undesirable in a liquid flowing through a pump, but air bubbles do not completely collapse like vapour voids
- Air bubbles become smaller when they are compressed, but will not do the same destructive damage as Cavitation To ensure maximum flow through a pump and prevent cavitation/vapour binding, what must be done? - correct answer ✔✔It is necessary to provide sufficient head on the pump suction so that suction pressure will always be greater than the vapour pressure of the liquid Available NPSH? (net positive suction head) - correct answer ✔✔- The head at the pump suction under operating conditions in the system Required NPSH? - correct answer ✔✔- The head necessary at the pump suction for the pump to perform properly The Available NPSH in a system must be calculated and checked to ensure that this is at least equal to (and preferably greater than) the Required NPSH specified by the manufacturer. True or False? - correct answer ✔✔True Pressure Vessels: Definition and Description? - correct answer ✔✔- Leak proof containers that have an internal or external operating pressure
- An unfired vessel is one having a design pressure between 103 kPa and 20 285 kPa and does not contain an integral source of heat
- Usually spherical or cylindrical in shape but may be oriented vertically or horizontally 2 standards which exist in Canada for the construction of pressure vessels? - correct answer ✔✔- The ASME Boiler and Pressure Vessel Code
- CSA B-51 Boiler, Pressure Vessel, and Pressure Piping Code
Between the CSA B-51 and the ASME Code, which one takes precedence over the other if a conflict exists? - correct answer ✔✔The CSA B-51 takes precedence over the ASME A manufacturer may apply a quality control program pertaining to the ASME codes, or comply to a quality control program following the codes of their local jurisdiction. True or False? - correct answer ✔✔True Which section of the ASME codes sets forth the requirements for design and construction of Pressure Vessels? - correct answer ✔✔The ASME Section VIII (8), Division 1 Who is responsible for performing the design calculations for a pressure vessel and making them available to the inspectors? - correct answer ✔✔The manufacturer The owner/operator of a pressure vessel is only responsible for its design requirements in relation to how that vessel is used in that particular system. True or False? - correct answer ✔✔True The Quality Control Inspector (QC) is responsible for verifying all details of construction, including...? - correct answer ✔✔Fit up; weld sizes, shell out-of- roundness, nozzle sizes, and fitting ratings. The final head on a vessel cannot be installed until all inspectors have completed a visual inspection of the interior of the vessel. True or False? - correct answer ✔✔True. This of course doesn't apply if the vessel is equipped with a manhole. The construction of pressure equipment is inspected or monitored by at least 2 parties with different interests and responsibilities. True or False? - correct answer ✔✔True 2 types of inspectors used for certifying a vessel? - correct answer ✔✔The jurisdiction inspector and the owners inspector
A vessel Nameplate should be located in a conspicuous location, and must be permanently applied to the vessel. True or False? - correct answer ✔✔True Design, fabrication and assembly of all pressure vessels follow procedures identified in what 2 parts of the ASME? - correct answer ✔✔1) ASME Section VIII, Division 1
- ASME Section IX List the A,B,C and D description from the Code Part UW of the ASME Section VIII, Division 1. - correct answer ✔✔A) - Longitudinal joints within the main shell, nozzles, flat head
- Circumferential joints connecting hemispherical heads to the main shell
- Any welded joint in a sphere B) Circumferential joints within the main shell, nozzles, torispherical, ellipsoidal heads and angle joints not greater than 30 degrees C) Welded Flanged joints; Van Stone laps, tube sheets, flat heads to main shell D) Welded Nozzle joints to main shell; spheres, flat-sided vessels What are the 5 types of formed heads? (Head Designs) - correct answer ✔✔a) Ellipsoidal b) Torispherical c) Hemispherical d) Conical e) Toriconical Describe a Ellipsoidal head design. - correct answer ✔✔- The long axis (D) is twice the length of the minor axis (2h) Describe a Torispherical head design. - correct answer ✔✔- Often referred to as flanged or dished heads
- The most common and commercially available design which has the minimum knuckle radius (r) equal to 6% of the inside crown radius (L)
Describe a Hemispherical head design. - correct answer ✔✔- Half of a perfect sphere (D = 2 x L) and calculated with the same equation used for spherical pressure vessels Describe a Conical head design. - correct answer ✔✔- Used when the apex angle ( x alpha) does not exceed 60 degrees Describe a Toriconical head design. (cone head with a knuckle) - correct answer ✔✔- Conical heads with transition knuckles, radius "r", which are used when the apex angle (2 x alpha) exceeds 60 degrees What topics are covered in the ASME Section VIII, Division 1, UW-15 and and UW-16?
- correct answer ✔✔a) UW-15: "Welded Connections" b) UW-16: "Minimum Requirements for Attachment Welds At an Opening" Why is Nozzle Reinforcement so important in Vessel design? - correct answer ✔✔- Stress loads are created from the piping and equipment attached to the pressure vessel to the nozzles
- A combination of internal pressure and stress loads can cause failure at the Nozzle if not accounted for in the design 4 means of providing reinforcement to Nozzle connections of a vessel? - correct answer ✔✔- Reinforcing pads on the shell
- Extra material thickness in the shell or nozzle
- An increase in weld metal
- Heavier shell plate in the section around the opening Materials used for Nozzle Reinforcement? - correct answer ✔✔- Reinforcement material must have an allowable stress value that is equal to or greater than that of the vessel material
- Lower strength material may only be used if the area of reinforcement is increased proportionately Describe what 'Area Replacement' is when referring to Nozzle Reinforcement. - correct answer ✔✔- Area replacement means that adequate reinforcement of the
Define "Operating Pressure". - correct answer ✔✔The normal operating pressure required by the process for which the vessel is designed Define: "Design Pressure" - correct answer ✔✔A higher pressure than the Operating Pressure and is used to determine the MINIMUM REQUIRED THICKNESS plus the CORROSION ALLOWANCE Define: "Normal Thickness" - correct answer ✔✔The design thickness that is commercially available in the material chosen to build the vessel Define: "Maximum Allowable Working Pressure" - correct answer ✔✔- Determined by the weakest element in the pressure vessel and its corresponding loading To establish the MAWP of a vessel, the vessel is assumed to be...? - correct answer ✔✔- Corroded
- Under adverse temperature conditions
- In operating position
- Under wind loading
- Under normal operating conditions for determining static head Which ASME section covers "Design Temperatures"? - correct answer ✔✔ASME Section VIII, Division 1, UG- The design temperature for a vessel is the expected normal operating temperature, with some factor of safety included. True or False? - correct answer ✔✔True Define: Thermal Stresses - correct answer ✔✔- Stresses resulting from restraints that prevent the natural expansion or contraction of a pressure vessel with changes in temperature
- Thermal stresses cause fatigue failures by repetitive cycling rather than stress failure due to rupture
Define: Creep (in metal) - correct answer ✔✔- At elevated temperatures, carbon steel will deform without any increase in stress
- Carbon steel decreases in strength with rising temperatures and becomes more brittle at low temperatures Define: Transition Temperature (referring to carbon steel) - correct answer ✔✔- Carbon steel has a temperature range below which it becomes susceptible to brittle fracture with little absorption of energy
- Abrupt transition from Ductile to Brittle behaviour 3 types of Static/Dead loads? - correct answer ✔✔1) Erection dead load
- Operating dead load
- Hydrostatic testing dead load Erection Dead Load? - correct answer ✔✔- The weight of the stripped vessel as it is hoisted at the plant site Operating Dead Load? - correct answer ✔✔- The weight of the vessel during operation Hydrostatic Testing Dead Load? - correct answer ✔✔- The weight of the vessel and the hydrostatic test loads weight Why do static/dead loads have the most effect on structure which are very tall? - correct answer ✔✔The dead load of a vessel results in compressive stress when the resultant force coincides with the axis of the vessel Factors to consider when designing a vessel for Wind Loadings? - correct answer ✔✔- Geographical location
- Maximum regionally measured wind velocity
- Vessel shape factors
- Height of the vessel and the possibility of varying wind velocities, at various heights
- Additional items attached to the vessel which will affect loading
- The environment or service the pressure vessel is in (corrosive environments)
- The total number of cycles combined with the level of stress, not time under load
- Material Surface conditions
- Local Stress concentrations which pose extra difficulty in design against fatigue Principle causes of incidents in relation to Pressure Vessels? - correct answer ✔✔- Poor equipment/system design
- Poor maintenance of the equipment
- An unsafe system of work
- Operator error
- Poor training/supervision
- Poor installation
- Inadequate repairs or modifications Operating personnel should be familiar with what conditions when handling types of pressure equipment? - correct answer ✔✔- Know what liquid or gas is being contained in the pressure vessel
- Know the process conditions, such as the temperature and pressures
- Know the safe operating limits of the pressure vessels and any equipment directly linked to, or affected by them
- Ensure there is a set of operating instructions for all the vessels and that these instructions contain what to do in an emergency situation What 4 items are to be considered in maintenance Quality Control program for pressure vessels? - correct answer ✔✔- Vessel and pipe metal thickness
- Signs of wear and corrosion
- Conditions of insulation and protective covers
- Signs of system problems, for example, a passing safety valve, etc. Pressure vessel protective safety equipment must be removed and inspected on an annual basic to make sure that...? - correct answer ✔✔1) They are in good operating condition
- They will function, as designed, at the correct preset operating condition
2 purposes of Pressure Testing vessels after they have been manufactured? - correct answer ✔✔- It verifies that the vessel can withstand the pressure for which it was designed
- There are not any leaks present Reason for pressure testing vessels which have already been in service? - correct answer ✔✔- Ensure the vessel can still safety withstand the operating pressure with a proven margin of safety
- Verify there are not any cracks which penetrate the vessel wall
- Ensure holes haven't developed Hydrostatic testing new vessels? - correct answer ✔✔- All connections and couplings must be closed off
- A drain valve must be equipped
- Filling connection must have an isolating valve and a vent valve is required at the top to allow air to be expelled during filling Hydrostatic Testing in-service vessels? - correct answer ✔✔- Vessels handling toxic or flammable fluids must be cleaned and purged before testing
- Vessel must be isolated from the rest of the system
- Existing valves may be used if their in good condition, if not, connections must be blinded
- Control line connections should be removed and closed off Safety Concerns with Hydrostatic Testing? - correct answer ✔✔- Liquids are used rather than air because they do not expand significantly when the pressure drops
- In the event of a failure, certain fittings and equipment may project from the equipment, so extra precautions should be taken Advantages of Hydrostatic testing equipment over pressure testing? - correct answer ✔✔- Inexpensive and safe, especially when using water
- Leaks through cracks and pinholes can easily be identified
