Interview questions for pipeline stress analysts; anyone willing to help answer them?

The following list provides some of the interview questions asked in various interviews for the Piping Stress Engineer position. I hope you’ll be able to find the answers in ASME B31.3, as well as in any textbooks on piping stress or piping handbooks. If you cannot find a specific answer, please reply in the comments section. This is part one of this collection; keep checking the website regularly for subsequent parts. How do you create a critical line list or flexibility log? How do you determine the critical line list using ASME B31.3? Generally, the determination of critical pipelines is based on the design requirements specified by the client or on past experience; if none of these are available, then domestic standards or PIP standards are used. b. It is sufficient to refer to the range specified in the PIP standard. In addition, the toxicity characteristics of the medium are evaluated using the tables in the appendix of ASME B31.3; stress analysis is generally recommended for Class M fluids. How to determine the stress-critical systems for analysis using Caesar II? General stress design specifications include classification into different categories; when classifying stress pipelines in the previous question, they were divided into three categories based on their importance: those requiring detailed calculation, those that can be calculated simply, and those that can be assessed visually. The computer-based part requires the use of software for analysis. Additionally, PIP has this classification into 3 categories. Which lines can be eliminated from formal stress analysis? ASME B31.3 specifies the conditions under which stress analysis can be waived; analysis can be omitted for pipelines that have been in successful operation before, or when a stress engineer determines that the stress conditions are significantly safer compared to those of similarly functioning pipelines. Simple piping systems can be deemed acceptable using flexible formulae. Can you create a typical sketch along with supporting elements for column piping? How do you determine how many load-bearing clip supports are needed? Diagram A will not be shown; pipe supports for tower piping are quite common. The number of weighing clips actually depends mainly on the strength of the equipment and the external loads applied to the pipes, and it isn’t entirely determined by stress engineers. If necessary, measures such as increasing the wall thickness of the tower or providing local reinforcement may be required. How to draw a typical sketch and supporting arrangement for pipeline systems in a tank farm? In what way is the analysis of tank pipelines different from that of pipeline systems in ordinary pressure vessels? a Diagram omitted. b The pipeline stress issues in tanks are mainly caused by uneven settlement; such stress is unidirectional, non-cyclic, and non-variational, allowing the allowable stress to be increased during design. What is SIF? What are the formulas for in-plane and out-of-plane SIF for elbows (B31.3)? SIF is an abbreviation for stress intensification factor; it represents the ratio of the external load required to cause failure after the same number of cycles under alternating loading, as compared to a branch pipe of equal diameter. It reflects the significance of stress concentration in components such as elbows. Place the elbow flat on a surface; if the surfaces are parallel, it is within the plane, while if they are perpendicular, it is outside the plane. What is the value of the flexibility factor for bending? The stress increase coefficient and flexibility coefficient are primarily determined through experiments. The relevant calculation formulas can be found in the appendices of ASME B31.3. What are the necessary documents required for stress analysis? a) List of pipes; b) Stress diagrams; c) Information on the equipment; d) PID; e) Pipe grades; f) Insulation specifications; g) Weight requirements for large-diameter manual and control valves; h) Engineering specifications for stress analysis; i) It is advisable to have 3D review files as well. Why is a spring hanger used? Can you write the formulas for spring HL, CL, and variability? Springs are used to provide support that can handle thermal displacements, and they also help to reduce some of the thermal stresses. HL-CL/HL = rate of load change. What are the different types of supports used in piping systems? There are mainly three types: load-bearing, limiting, and vibration-damping. What do you know about expansion joints and their types? When are they used? An expansion joint is a flexible component designed to absorb displacements; the main types include the simple universal type, the hinge type, and the pressure balance type. b The medium is not hazardous; when the pipe diameter is large and the pressure is low, or when there is significant thermal displacement due to high temperatures, expansion joints can be considered for use. What are the normal types of load cases? List the load cases for a typical stress system using the static methods for seismic and wind loads. There are three basic operating conditions: cold operation, hot operation, and hot operation minus cold operation. The load cases can be expressed as W+T+P+H+U1/U2/U3/U4 or W+T+P+H+Win1/Win2/Win3/Win4. What is slug flow? What parameters are required to calculate the slug force? Slug flow is a type of flow in which the fluid contains both gas and liquid phases; the gas and liquid separate and flow along the pipeline in columnar pulses. The force and flow rate of plug flow are related to the density of the medium and the flow area. What are the dynamic restraints? What is a snubber and when is it used? A dynamic restraint bracket is a type of bracket used to prevent excessive deformation that could lead to damage or the effect of external forces, when there are dynamic changes or trends in the piping system. B-shock absorbers are used in situations where slow deformations of the pipeline, such as those caused by thermal expansion or wind effects, are not to be restricted, but rapid deformation responses must be controlled. I have used them in scenarios involving earthquakes, water hammer and air hammer effects, as well as during the opening and closing of safety valves. What is the minimum allowable swing for a top-mounted hanger? What will you do if that amount exceeds the limit in a typical piping system? Suspended tie rods, which include suspended springs, have strict requirements regarding the angle of swing; generally, a value of around 4 degrees is sufficient. The specific values can be found in GB standards or specified in engineering requirements. What is cold drawing and why is it used? Cold-drawn pins are mainly used in situations where alignment is necessary near sensitive machines. What is the difference between a variable hanger and a constant hanger? What is the variability of a constant spring hanger? The load exerted by a constant spring hardly changes with displacement; generally, the rate of change of this load is required to be very small. MSS-SP-58 specifies that this rate should be 6%. What are the inputs required for stress analysis? What factors are considered in the Caesar analysis of a piping system? The first question and the eighth question are repetitive, so they will not be discussed in detail here. The main factors include pressure, pipe diameter, temperature, weight, density, and similar elements. There are many things to check: input conditions, model errors, and output results – these are the main three categories. What do you mean by the term “liberal stress”? I’m not sure which Chinese literature uses the term \"affluence stress\" for it. Since the traditional methods for stress checking involve separate checks for primary and secondary stresses, there is a proposal that the remaining margin from the primary stress checks can be applied to improve the secondary stress levels. If you look at Dr. Tang’s book in detail, it’s explained very clearly. 20) What is the hot-cold philosophy for pumps? Have you heard of the term pump alignment? My understanding is that it refers to the design concept regarding the spring loads of pumps in hot and cold conditions, and this topic can be discussed in some detail. Thermal zeroing of the spring facilitates operation, while cold zeroing facilitates installation. On-site alignment of mechanical pumps and compressors is the most complicated and error-prone step in installation. Therefore, given the difficulty of installation, I personally recommend zeroing it using a spring in the cold state. For the specific procedures, you can refer to API-686, which contains detailed descriptions.