SPED Piping Design Principles & Standards 3 — Questions and Answers
Question 1: Which document defines the piping material requirements for a specific service, including pipe grade, fittings, and valves?
- Plot Plan
- Piping and Instrumentation Diagram
- Piping Material Specification (PMS) (Correct answer)
- Isometric Drawing
Correct answer: Piping Material Specification (PMS)
A Piping Material Specification (PMS) or Piping Class document defines all materials, ratings, end connections, and components approved for each service class.
Question 2: What is the standard flange pressure-temperature rating class used for low-pressure steam service in many refinery applications?
- Class 150 (Correct answer)
- Class 300
- Class 600
- Class 900
Correct answer: Class 150
ASME B16.5 Class 150 flanges are commonly used for low-pressure steam and moderate-pressure services in refineries and process plants.
Question 3: On a P&ID, what symbol is typically used to represent a control valve?
- A circle with an arrow inside
- A bow-tie or butterfly shape with a circle on top indicating the actuator (Correct answer)
- A rectangle with diagonal lines
- A diamond shape
Correct answer: A bow-tie or butterfly shape with a circle on top indicating the actuator
Control valves on P&IDs are shown as a bow-tie (globe valve body) symbol with an actuator circle above, per ISA 5.1 symbology standards.
Question 4: What is the recommended slope for steam condensate return lines to ensure proper drainage?
- 1/8 inch per foot minimum (Correct answer)
- 1/16 inch per foot minimum
- 1/4 inch per foot minimum
- No slope is required
Correct answer: 1/8 inch per foot minimum
Steam condensate lines are typically sloped a minimum of 1/8 inch per foot in the direction of flow to prevent water hammer and ensure proper drainage.
Question 5: Which fitting type provides the strongest and most leak-resistant joint for high-pressure piping?
- Screwed (threaded) fitting
- Socket weld fitting
- Butt weld fitting (Correct answer)
- Compression fitting
Correct answer: Butt weld fitting
Butt weld fittings, when properly welded, create a full-penetration joint that is as strong as the pipe itself and is preferred for high-pressure, high-temperature service.
Question 6: What is the primary purpose of a pressure safety valve (PSV) in a piping system?
- To regulate flow rate to downstream equipment
- To relieve overpressure and protect equipment from exceeding design pressure (Correct answer)
- To prevent reverse flow in the line
- To reduce upstream pressure to a set point
Correct answer: To relieve overpressure and protect equipment from exceeding design pressure
A PSV is a last line of defense that automatically opens to vent fluid when system pressure exceeds the design limit, preventing vessel or piping failure.
Question 7: What is the term for the allowable distance a pipe can span between supports without excessive deflection?
- Span length
- Support span (Correct answer)
- Pipe reach
- Cantilever distance
Correct answer: Support span
Support span is the maximum allowable distance between pipe supports, determined by pipe size, material, fluid weight, and deflection limits.
SPED Piping Design Principles & Standards 3
Which document defines the piping material requirements for a specific service, including pipe grade, fittings, and valves?