Static Equipment Interview Questions -
Here’s a detailed, insightful post on Static Equipment Interview Questions — designed for mechanical engineers, inspection professionals, and freshers alike.
Q13: What are the common roof types in API 650 tanks?
Answer:
- Fixed cone roof – self-supporting or supported by columns. For low internal pressure (1.0 psi).
- Dome roof – curved, self-supporting.
- Floating roof – internal (inside fixed roof) or external (open top). Reduces vapor loss.
- Umbrella roof – similar to cone but with sloped plates.
Part 8: Advanced & Scenario-Based Questions (For Senior Roles)
Part 6: Inspection & NDE (Nondestructive Examination)
Part 6: Scenario & Behavioral (The Problem Solver)
Q16: What is the difference between corrosion allowance and erosion allowance?
Answer:
- Corrosion allowance (C.A.): Extra thickness added to compensate for material loss due to chemical attack over design life (typical 1/16" to 1/4").
- Erosion allowance: Extra thickness for mechanical wear from particle impact (e.g., sand, catalyst fines). Often added only in high-velocity zones (elbows, inlet nozzles).
Q22: What is a "RBI" (Risk-Based Inspection) study and why is it relevant to static equipment?
Answer: RBI (API 580/581) prioritizes inspection intervals based on probability of failure (PoF) and consequence of failure (CoF). Instead of fixed intervals (e.g., 5 years), RBI allows extended runs for low-risk items (e.g., nitrogen service) and shorter, more rigorous inspections for high-risk (e.g., hydrogen reformers). It saves cost and reduces unnecessary shutdowns.
The Challenge: Materials and Corrosion
Since static equipment sits in one place for decades, material degradation is the primary enemy. static equipment interview questions
Common Question: What are the different types of corrosion, and how do you mitigate them?
How to Answer: You must move beyond general rust. Discuss specific mechanisms: Here’s a detailed, insightful post on Static Equipment
- Uniform Corrosion: Even metal loss. Mitigated by adding a "Corrosion Allowance" (e.g., 3mm extra thickness) during design.
- Pitting Corrosion: Localized deep holes, common in stainless steel exposed to chlorides. Dangerous because it is hard to detect and can lead to leaks.
- Stress Corrosion Cracking (SCC): The combination of tensile stress and a corrosive environment (e.g., chlorides in austenitic stainless steel). It causes sudden, brittle failure.
- Crevice Corrosion: Occurs in stagnant areas like flange faces or under gaskets.
Common Question: What is PWHT and why is it required?
How to Answer: PWHT stands for Post-Weld Heat Treatment. It is a process of heating the welded metal to a specific temperature and holding it there, then cooling it slowly. It relieves residual stresses created by the intense heat of welding. It is critical for materials like Carbon Steel above a certain thickness (usually >32mm) or alloy steels, as it reduces the risk of brittle fracture and environmental cracking. Q13: What are the common roof types in API 650 tanks