Piping Piping Materials and Specifications 2 — Questions and Answers
Question 1: What does ASTM A312 specify?
- Seamless and welded austenitic stainless steel pipes (Correct answer)
- Alloy steel bolting for high-temperature service
- Carbon steel flanges
- Wrought steel butt-welding fittings
Correct answer: Seamless and welded austenitic stainless steel pipes
ASTM A312 covers seamless, straight-seam welded, and heavily cold worked austenitic stainless steel pipe for high-temperature and corrosion service.
Question 2: What is the purpose of a material test report (MTR) or mill certificate?
- To certify a welder's qualifications
- To document the chemical composition and mechanical properties of a specific heat of pipe or material (Correct answer)
- To record pressure test results
- To specify the required coating system
Correct answer: To document the chemical composition and mechanical properties of a specific heat of pipe or material
An MTR (mill certificate) is issued by the manufacturer and documents the actual chemical composition and mechanical test results for the specific batch of material supplied.
Question 3: What is Positive Material Identification (PMI) used for in piping?
- To measure pipe wall thickness in the field
- To verify that the correct alloy material is installed using XRF or OES analysis (Correct answer)
- To check the surface roughness of pipe bores
- To test pipe for internal corrosion
Correct answer: To verify that the correct alloy material is installed using XRF or OES analysis
PMI uses X-ray fluorescence (XRF) or optical emission spectroscopy (OES) to verify alloy composition of installed piping, preventing carbon steel substitution for alloy pipe.
Question 4: What is the key difference between seamless and electric resistance welded (ERW) pipe?
- Seamless pipe has no longitudinal weld seam; ERW pipe has a seam weld along its length (Correct answer)
- Seamless pipe can only be used below 300°F; ERW is for high-temperature service
- ERW pipe has thicker walls than seamless pipe of the same schedule
- There is no functional difference in pressure rating
Correct answer: Seamless pipe has no longitudinal weld seam; ERW pipe has a seam weld along its length
Seamless pipe is extruded or pierced from a solid billet with no weld seam, while ERW pipe is formed from strip steel and welded along one longitudinal seam.
Question 5: What is the purpose of impact testing (Charpy V-notch) for piping materials?
- To measure hardness of the weld heat-affected zone
- To verify adequate toughness and resistance to brittle fracture at low temperatures (Correct answer)
- To check tensile strength at elevated temperatures
- To determine fatigue life under cyclic loading
Correct answer: To verify adequate toughness and resistance to brittle fracture at low temperatures
Charpy impact testing measures the energy absorbed by a material during fracture at specified temperatures, verifying adequate toughness for low-temperature service applications.
Question 6: What is duplex stainless steel primarily used for in piping systems?
- Cryogenic service below -150°F
- Corrosive service requiring both high strength and chloride stress corrosion cracking resistance (Correct answer)
- High-temperature oxidizing service above 1000°F
- General utility water service
Correct answer: Corrosive service requiring both high strength and chloride stress corrosion cracking resistance
Duplex stainless steels (e.g., 2205) have a two-phase austenite-ferrite microstructure offering higher strength than austenitic grades and excellent resistance to chloride stress corrosion cracking.
Piping Piping Materials and Specifications 2
What does ASTM A312 specify?