1) How to make critical line list or flexibility log? How will you decide critical line list with help of ASME B31.3? 2) How to decide Stress critical systems for analysis using Caesar II? 3) Which lines can be eliminated from formal Stress analysis? 4) Can you make a typical Sketch & supporting for column piping? How to decide how many load bearing clip supports to be used? 5) Draw a typical Sketch & supporting arrangement for tank farm piping? How tank Piping analysis is different from normal pressure vessel connected piping system analysis? 6) What is SIF? Formulas for In plane, outplane sif for elbow (B31.3)? 7) Value of sif, flexibility factor for Bend? 8) What are the necessary documents required for stress analysis? 9) Why a Spring hanger is used? Can you write the formula for spring HL, CL & variability? 10) What are the different types of supports used in piping systems? 11) What do you know about Expansion joints and thier types? When these come into picture? 12) What are the normal types of load cases? Write the load cases for a typical stress system using static method of seimic and wind? 13) What is slug flow? What parameters are required to calculate Slug force? 14) What are the dynamic restraints? What is snubber and when do you use a snubber? 15) What is the minimum swing allowed in top mounted hanger? What will you do if that amount exceeds in a typical piping system? 16) What is cold pull and why it is used? 17) What is difference between Variable Hanger and Constant Hanger? What is the variability of Constant Spring hanger? 18) What are the inputs required for stress analysis? What do you check in Caesar analysis of a piping system?
19) What do you mean by the term “liberal stress”? 20) What is hot-cold philosophy for pump? Have you heard the term Pump alignment? 21) Write equation for SE in terms of Sb and St from ASME B 31.3? 22) What are the major difference between WRC 107 and WRC 297? 23) How Anchor load for a rack is calculated at the initial phases of project? What are the normal guidelines assumed? 24) Draw a typical control station layout and show its supporting? 25) How pump piping is routed and supported? 26) How you will decide the position of anchor bay in rack piping? 27) Which side (suction or discharge) in case of pump piping system is more critical from stress point of view? Justify the answer? 28) What are the main factors that decides support span? 29) What does API610 explains about aloowable nozzle loads for a Centrifugal Pump? 30) Can you show the typical layout and supporting for PSV lines? 31) What is the effect of friction in Piping stress analysis? 32) How layout of a pump piping changes with changes in temperature? 33) Why the allowable for primary stress is different from that of secondary stress? 34) Is the stress due to seismic anchor movement an occasional stress ? Explain with proper reason? 35) What is meant by the sentence ”primary stress is not self relieving but secondary stress is”? Explain in detail the meaning of the term “ self relieving”. 36) Will SIF increase or decrease with increase in pressure, other parameters kept constant? Justify your answer. 37) What is the role of Y factor in the pressure thickness eqn. of B31.3 and B31.1?
38) Is the pressure thickness eqn. for bends same as that of straight pipe in B31.3? 39) How B31.3 defines the terms Weldolet, Sweepolet? 40) Between a short and a long radius bend, which one has higher flexibility and why? 41) What does B31.3 tell about SIF for sockolet and reducer? 42) Explain the role of Appendix V of B31.3? 43) Does B31.3 allow a stress limit of 1.33Sh in PSV pop up case or is it 1.20 Sh? 44) Explain how to model snubber in CAESAR II. 45) Briefly explain the modeling of Sway Brace is CAESAR II. 46) What is the basic difference between a snubber and a sway brace in terms of applicability? 47) Explain with reason as to what should happen to the SIF and Flexibility factor of a bend when a trunnion is attached to it? 48) Explain the terms SIF and FLEXIBILITY factor. 49) Why SIF is “not so significant” with primary loading? 50) What happens to SIF of a reinforced connection if thickness of reinforcement increases beyond 1.5 times header thickness? 51) What special note B31.3 provides for SIF of welding tees (B16.9) ? 52) Explain with reasons as to which one is having higher SIF: a 45 bend or a 90 Bend? 53) Explain with reasons as to whether for a non 90 degree branch the same SIF can be taken as that for a 90 branch? 54) If thickness of the header of a branch connection increases, what happens to its SIF, other parameters kept constant? 55) What are the methods for flange leakage checking? Write euations used for flange leakage checking in pressure equivalent method? 56) What are the major difference between ASME B 31.3 and B31.1?
57) Place the following lines in Rack and show the placement of expansion loop? a) A 16 inch High pressure steam line b) A 6 inch Low pressure steam line c) A 10 inch Medium pressure steam line d) A 30 inch flare line e) A 8 inch process line and f) A 24 inch cooling water line. 58) How to decide the Spring height for a top mounted Spring hanger? What are the attachments used? 59) How do you calculate SIF for 45 degree lateral connections entering into flare header? 60) What are the transfer lines? Why does the stress analysis of transfer lines considered critical? 61. If a power plant is designed inside a Process refinery then where the specification break between ASME B31.1 & ASME B31.3 should occur? 62.What is category M fluid service? Provide some examples? 63.What will be the consequences of a steam piping having low pocket but not having a steam trap? 64.When and why the reducer of a pump suction piping is installed in bottom flat condition? 65. If you found a specification break (at flange) between carbon steel and stainless steel in a typical P&ID. What are the additional arrangements which a piping engineer should make for this? 66.Assume a straight pipe of length L anchored at both ends. When a temp change occurs the anchor force at one anchor becomes F1. Now the length of the same pipw increased to L2 and with similar temp change anchor force becomes F2. What is the relation between F1 and F2?
67. What is Piping Speciality item? How many types of piping speciality items are used in piping engineering? Can we include them in standard piping specification, explain with reason? 68.Why does the sustained sagging for steam lines are limited within 3-5 mm? 69. What is a “Double block & Bleed” valve? When such type valves are required? 70.In a normal tie-in where do you insert the spectacle blind? a) before block valve and towards new plant or b) after block valve and towards existing plant . Explain why. 71.What is the difference between a pipe elbow and a bend? 72. Among the following which material have the highest co-efficient of thermal expansion? A) Carbon steel b) Cast Iron c) Duplex steel d)Stainless steel e) Galvanized Carbon steel 73.What are the major parameters to be reported in support tag for a Shoe/Saddle type support? 74.What are the Metallic expansion joints? When they are used and when they could be avoided? 75.What is hot sustained stress? Why do we check it? Do we need to chech expansion stress for hot sustained case? 76. What is the philosophy of arranging pipes in the Pipe rack and why? Normally what % of area is kept reserved for future expansion? 77.What are the major difficulties faced by a stress engineer while analysis two vertical rebolers connected with a single column? 78.What are the different types of combination methods available is Caesar II? What is the difference between Scalar and Absolute method? 79. Are process plant water lines considered pressure piping systems? 80. For what fluid service category may a hydro test be waived off as per B31.3? 81. Check the following load cases and tell me what is the difference between load case L3 and L4?
L1. W+T1+P1
OPE
L2. W+P1
SUS
L3. L1-L2
EXP
L4. T1
EXP
82. Which comes first?–Stress or Strain? 83. What is the difference between Stress and Pressure? 84. What are the major differences between a Pipe and a Tube? 85. What is seismic co-efficient? How this is decided? 86. What is wind shape factor? How the value of wind shape factor is decided? 87. Why does the manufacturer produce pipes with OD constant for a specific size and varying ID? 88. What are the major responsibilities of a stress engineer?89. What are the major differences between primary and secondary stresses in Piping? 90. Do you consider the vertical thermal growth for modelling fired heater in Caesar II? Explain with reason? 91. Why does the dummy of a piping system is also insulated for cold insulated piping system but not insulated for hot insulated piping system? 92. What are the major parameters and process inputs required for performing dynamic slug flow analysis? 93. Which parameters do you seek from civil department for performing underground piping analysis in Caesar II? Describe briefly the method of performing underground piping analysis using caesar II? What are the outputs to check and what to interpret from caesar results? 94. How to calculate pipe thickness for externally pressured piping system? 95. What do you mean by the term flexibility ? How to ensure that the flexibility of a piping system is appropriate? What are the means for increasing flexibility? What will happen if more flexibility is provided to a piping system?
96. As per code ASME B 31.3 how many types of fluid service is available? 97. What are the code cases for ASME B 31.3? 98. Describe step by step methods for modelling a sway brace in caesar II? 99. In which way PDS, PDMS and SP3D differs? Which one is the best user friendly? 101. Can we exceed the design pressure of a piping system more than its design pressure. If yes then in what condition? 102. What is the limitation of using PTFE slide plate? What can be done in such situation?103. How to decide whether hydrotest or pneumatic test will be performed for a piping system? 104. What is bourdon effect of Piping system? When this effect become critical? 105. How do you check dummy ot trunnions for any project? Can you write the formulas used for this checking? 106. What is the difference between pressure safety valve and pressure relief valve? 107. Why do you consider slug flow in a piping system as critical? 108. What is the function of a gasket in flanged joint? 109. Why sustained stress is considered as a primary stress? 110. What are the major differences between SIF and SCF (Stress Concentration Factor)? 111. Lets assume from a 24 inch pipe header two tapping, one 2 inch and other one 4 inch, are taken. At the interconnection point in which case the SIF will be higher? 112. What is the industry accepted procedure for transferring anchor load for intermediate anchors (anchor in between two loops) where normally caesar shows very less value? 113. How to analyze stress packages when D/T ratio for the pipe exceeds 100?
114. Arrange the following piping elements with respect to flexibility and SIF (either increasing or decreasing order). Assume pipe size and thickness are constant.: 1.5D bend, 1D bend, Straight Pipe, 4D bend, 10D bend. 115. What is primary membrane stress? 116. Which one is more flexible : 45° bend or 90° bend? Which one is having more SIF? 117. Can we call piping shoe a pipe component as per code? Explain with reason. What is your opinion about RF pad in this respect? 118. What does the piping code says about the operation and maintenance of piping system? 119. You want to make some changes in the existing plant and want to add a new line by hot tapping. From which point the ASME B 31.3 code will be applicable? 121. How to model Air fin Fan Cooler in Caesar II? Why do you consider equipment weight in AFC modeling while for other heat exchanger we do not consider? What code need to be followed for nozzle load checking and what the code says about nozzle load checking? Why do we need thrust blocks for air fin fan cooler? 122. Can you write the NEMA equipment nozzle equation sets? What are the major differences in between API 617 and NEMA SM 23 from stress point of view? Draw a typical steam turbine piping layout? 123. Which standard is used for designing plate fin heat exchanger? Which table is normally followed for nozzle load checking? 124. How do you consider tank settlement while stress analysis? Is it a primary or secondary stress? Do you add tank settlement with sustained load cases? If yes why? What code says about tank settlement? What is tank bulging and why does it happen? 125. Draw a typical layout of a line connected with fired heater (Heater Piping)? Which standard is used for allowble nozzle loads? 126. What are the major differences in between B 31.3 edition 2012 and 2010?
127. Which standard says about rotary equipment alignment check? What is the criteria mentioned in that standard? While alignment checking spring will be in locked or design condition? 128. Calculate the number of loops for a 400 meter long carbon steel pipe having a temperature of 400 degree centigrade running over a pipe rack? 129. How do you calculate PSV reaction forces in absence of reaction force in vendor data? What is the major difference in between pressure safety valve and pressure relief valve? 130. Do you perform trunnion check while analysing a stress system? What are the associated formulas for trunnion checking? 131. What is the equation for calculating seismic co-efficient? How to calculate the wind force? 132. What is guided cantilever method? What is the importance of this method? 133. What does the Appendix F of API 610 ensures? What are the equations? What the standard says for vertical inline pumps? 134. What do you mean by weld joint strength reduction factor and quality factor? What is the importance of these factors? 135. While providing preliminary rack loading what assumptions do you consider? 136. What was the most critical system you analysed in the last company? Draw the layout? What changes you recommended? What is temperature of that line? 137. What are the minimum load cases required to consider while performing stress analysis of a vertical reboiler connected piping system? 138. Have you performed stress analysis of reciprocating compressor connected line? What are the considerations? What is the minimum frequency you achieved before sending for pulsation study? How do you consider upto what length of piping is to be send for pulsation study? 139. What actually do you check during flange leakage checking by NC 3658 method?
140. Can we reduce the hydrotest pressure of pipe to less than 1.5 times the line design pressure? If yes then in what condition?
1. What is the scope of ASME B 31.3? What does it covers and what does not? 2. What are the disturbing parameters against which the piping system must be designed? Ans: The piping system must stand strong (should not fail) against the following major effects:
Design Pressure and Temperature: Each component thickness must be sufficient to withstand most severe combination of temperature and pressure.
Ambient effects like pressure reduction due to cooling, fluid expansion effect, possibility of moisture condensation and build up of ice due to atmospheric icing, low ambient temperature etc.
Dynamic effects like impact force due to external or internal unexpected conditions, Wind force, Earthquake force, Vibration and discharge (Relief valve) reaction forces, cyclic effects etc.
Component self weight including insulation, rigid body weights along with the medium it transport.
Thermal expansion and contraction effects due to resistance from free displacement or due to thermal gradients (thermal bowing effect) etc.
Movement of pipe supports or connected equipments etc.
3. How to calculate the allowable stress for a carbon steel pipe? Ans: The material allowable stress for any material other than bolting material, cast iron and malleable iron are the minimum of the following: 1.
one-third of tensile strength at maximum temperature.
2.
two-thirds of yield strength at maximum temperature.
3.
for austenitic stainless steels and nickel alloys having similar stress– strain behavior, the lower of two thirds of yield strength and 90% of yield strength at temperature.
4.
100% of the average stress for a creep rate of 0.01% per 1 000 h
5.
67% of the average stress for rupture at the end of 100 000 h
6.
80% of the minimum stress for rupture at the end of 100 000 h
7.
for structural grade materials, the basic allowable stress shall be 0.92 times the lowest value determined (1) through (6) above.
4. What is the allowable for Sustained, Occasional and Expansion Stress as per ASME B 31.3? Ans: Calculated sustained stress (SL)< Sh (Basic allowable stress at maximum temperature) Calculated occasional stress including sustained stress< 1.33 Sh Calculated expansion stress< SA = f [ 1.25( Sc + Sh) − SL] Here f =stress range factor, Sc =basic allowable stress at minimum metal temperature and SL=calculated sustained stress. The sustained stress (SL) is calculated using the following code formulas:
Here, Ii = sustained in-plane moment index. In the absence of more applicable data, Ii is taken asthe greater of 0.75ii or 1.00. Io = sustained out-plane moment index. In the absence of more applicable data, Io is taken as the greater of 0.75io or 1.00. Mi = in-plane moment due to sustained loads, e.g.,pressure and weight Mo = out-plane moment due to sustained loads, e.g.,pressure and weight Z = sustained section modulus
It = sustained torsional moment index. In the absence of more applicable data, It is taken as 1.00. Mt = torsional moment due to sustained loads, e.g.,pressure and weight Ap = cross-sectional area of the pipe, considering nominal pipe dimensions less allowances; Fa = longitudinal force due to sustained loads, e.g.,pressure and weight Ia = sustained longitudinal force index. In the absence of more applicable data, Ia is taken as 1.00. 5. What are steps for calculating the pipe thickness for a 10 inch carbon steel (A 106-Grade B) pipe carrying a fluid with design pressure 15 bar and design temperatre of 250 degree centigrade? Ans: The pipe thickness (t) for internal design pressure (P) is calculated from the following equation.
Here, D=Outside diameter manufacturer standard.
of
pipe,
obtain the
diameter
from pipe
S=stress value at design temperature from code Table A-1 E=quality factor from code Table A-1A or A-1B W=weld joint strength reduction factor from code Y=coefficient from code Table 304.1.1 Using the above formula calculate the pressure design thickness, t. Now add the sum of the mechanical allowances (thread or groove depth) plus corrosion and erosion allowances if any with t to get minimum required thickness, tm. Next add the mill tolerance with this value to get calculated pipe thickness. For seamless pipe the mill tolerance is 12.5% under tolerance. So calculated pipe thickness will be tm/(1-0.125)=tm/0.875.
Now accept the available pipe thickness (based on next nearest higher pipe schedule) just higher than the calculated value from manufacturer standard thickness tables. 6. How many types of fluid services are available for process piping? Ans: In process piping industry following fluid services are available..
Category D Fluid Service: nonflammable, nontoxic, and not damaging to human tissues, the design pressure does not exceed 150 psig, the design temperature is from -20 degree F to 366 degree F.
Category M Fluid Service: a fluid service in which the potential for personnel exposure is judged to be significant and in which a single exposure to a very small quantity of a toxic fluid, caused by leakage, can produce serious irreversible harm to persons on breathing or bodily contact, even when prompt restorative measures are taken.
Elavated Temperature Fluid service: a fluid service in which the piping metal temperature is sustained equal to or greater than Tcr (Tcr=temperature 25°C (50°F) below the temperature identifying the start of time-dependent properties).
Normal Fluid Service: a fluid service pertaining to most piping covered by this Code, i.e., not subject to the rules for Category D, Category M, Elevated Temperature, High Pressure, or High Purity Fluid Service.
High Pressure Fluid Service: a fluid service for which the owner specifies the use of Chapter IX for piping design and construction. High pressure is considered herein to be pressure in excess of that allowed by the ASME B16.5 Class 2500 rating for the specified design temperature and material group.
High Purity Fluid Service: a fluid service that requires alternative methods of fabrication, inspection, examination, and testing not covered elsewhere in the Code, with the intent to produce a controlled level of cleanness. The term thus applies to piping systems defined for other purposes as high purity, ultra high purity, hygienic, or aseptic.
7. What do you mean by the term SIF?
Ans: The stress intensification factor or SIF is an intensifier of bending or torsional stress local to a piping component such as tees, elbows and has a value great than or equal to 1.0. Its value depends on component geometry. Code B 31.3 Appendix D (shown in below figure) provides formulas to calculate the SIF values. 8. When do you feel that a piping system is not required formal stress analysis? Ans: Formal pipe stress analysis will not be required if any of the following 3 mentioned criteria are satisfied: 1.
if the system duplicates, or replaces without significant change, a system operating with a successful service record (operating successfully for more than 10 years without major failure).
2.
if the system can readily be judged adequate by comparison with previously analyzed systems.
3.
if the system is of uniform size, has no more than two points of fixation, no intermediate restraints, and falls within the limitations of empirical equation mentioned below:
Here, D = outside diameter of pipe, mm (in.) Ea = reference modulus of elasticity at 21°C (70°F),MPa (ksi) K1 = 208 000 SA/Ea, (mm/m)2 = 30 SA/Ea, (in./ft)2 L = developed length of piping between anchors,m (ft) SA = allowable displacement stress range U = anchor distance, straight line between anchors,m (ft) y = resultant of total displacement strains, mm (in.), to be absorbed by the piping system 9. How will you calculate the displacement (Expansion) stress range for a piping system?
Ans: Expansion stress range (SE) for a complex piping system is normally calculated using softwares like Caesar II or AutoPipe. However, the same can be calculated using the following code equations:
here Ap = cross-sectional area of pipe Fa = range of axial forces due to displacement strains between any two conditions being evaluated ia = axial stress intensification factor. In the absence of more applicable data, ia p 1.0 for elbows, pipe bends, and miter bends (single, closely spaced, and widely spaced), and ia =io (or i when listed) in Appendix D for other components; it = torsional stress intensification factor. In the absence of more applicable data, it=1.0; Mt = torsional moment Sa = axial stress range due to displacement strains= iaXFa/Ap Sb = resultant bending stress St = torsional stress= itXMt/2Z Z = section modulus of pipe ii = in-plane stress intensification factor from Appendix D io = out-plane stress intensification factor from Appendix D Mi = in-plane bending moment Mo = out-plane bending moment Sb = resultant bending stress 10. What do you mean by the term “Cold Spring”? Ans: Cold spring is the intentional initial deformation applied to a piping system during assembly to produce a desired initial displacement and stress. Cold spring is beneficial in that it serves to balance the magnitude of stress under initial and extreme displacement conditions. When cold spring is properly applied during initial operation; hence, it is materials of limited ductility. There is dimensions during initial operation, so far from their original settings.
there is less likelihood of overstrain recommended especially for piping also less deviation from as installed that hangers will not be displaced as
However now a days most of the EPC organizations does not prefer the use of Cold Spring while analysis any system. 11. How to decide whether Reinforcement is required for a piping branch connection or not? Ans: When a branch connection is made in any parent pipe the pipe connection is weakened by the opening that is made in it. So it is required that the wall thickness after the opening must be sufficiently in excess of the required thickness to sustain the pressure. This requirement is checked by calculating the required reinforcement area (A1) and available reinforcement area (A2+A3+A4) and if available area is more than the required area then no reinforcement is required. Otherwise additional reinforcement need to be added. The equations for calculating the required and available area are listed below for your information from the code. Please refer the code for notations used:
