In air separation units (ASUs), thereexists a class of valves that typically operates in obscurity—yet a single malfunction can expose the entire compressor train to surge or even complete shutdown. These are the compressor anti-surge valves.
In recent years, we have received extensivefeedback indicating that anti-surge valve failures are far from rare, occurring across both Main Air Compressors (MAC) and Booster Air Compressors (BAC). Issues such as severe valve position oscillation, multi-second responsedelays, stem breakage, excessive vibration, and leakage have not onlycompromised unit stability but also, more critically, caused clients to lose control of their equipment at pivotal moments, creating significant safety risks.
Currently, systematic technical analysis ofanti-surge valves remains scarce. Most engineers must rely on trial-and-error experience, lacking deeper understanding of core issues such as selection logic, response speed, flow velocity control, piping layout, flow direction selection, and sealing class.
Why This Series?
Through sharing real-world field data,failure curves, and teardown analysis, we aim to help you:
Avoid repeating past mistakes by identifying design flaws early
- Understand critical decision points in anti-surge valve selection
- Master optimization methods for flow velocity control and piping arrangement
- Clarify how flow direction and sealing class impact safety and energy efficiency
- Series Overview
This series will focus on the followingcore topics:
I. Comprehensive Overview of TypicalFailures in MAC and BAC Anti-Surge Valves
II. Selection Dilemma: Globe vs. Butterfly?
III. Flow Velocity Control: Orifice Plates, Upstream/Downstream Piping, andInstallation Methods
IV. Flow Direction Selection: Often-Overlooked Details
V. Sealing Class and Leakage: Critical for Safety and Energy Efficiency
PART I. Comprehensive Overview of TypicalFailures in MAC and BAC Anti-Surge Valves
Case 1: 300,000 Nm³/h MAC, DN600Butterfly Valve
Issue 1: Atlarge openings, valve position could not stabilize.
Issue 2: Duringsurge testing with the vent valve closed and pressure increased:
- As pressure rose, the deviation between output and feedback signals increased. A 1–2% signal demanding valve closure produced no movement; only when the signal increased to 4–5% did the valve respond.
- Most critical problem: When the valve closed to ~43% opening, the air compressor surged. On-site personnel de-energized the solenoid valve and the control system increased the analog output signal—yet the valve did not move, failing to unload the compressor. Disconnecting instrument air at the valve produced no response. Only after manually reducing upstream pressure did the valve resume operation and automatically open fully.
Case 2: 310,000 Nm³/h MAC, DN500Butterfly Valve
- At 23% guide vane opening, with the vent valve fully open and then slowly closing, the compressor discharge pressure operated acceptably at 250 kPa with proper valve positioning. However, at 370–380 kPa operation, valve position instability occurred: at a 68% opening, the valve would oscillate approximately 3–5° between 61–65%.
- Upon solenoid valve de-energization, the valve was required to open fully within 1 second, but a 3–4 second delay occurred before any movement began.
Case 3: 110,000 Nm³/h MAC, DN350 Butterfly Valve
Severe excessive vibration.
Case 5: 110,000 Nm³/h MAC, DN400 GlobeValve
Leakage issues.
Case 6: 170,000 Nm³/h, 26 bar BACAnti-Surge Valve
High vibration.
Stay tuned for Part II: "Selection Dilemma: Globe vs. Butterfly?"