How to review Anti-Surge Control Valve Designs from Compressor Vendor – Guide for a EPC/Engineering Contractor

For Engineering, Procurement, and Construction (EPC) contractors, the meticulous review of an Original Equipment Manufacturer’s (OEM) anti-surge control valve design is a critical step in safeguarding the integrity and operational stability of a centrifugal compressor. A failure in this single piece of equipment can lead to catastrophic compressor damage, resulting in significant financial losses and safety hazards. Therefore, a rigorous and systematic check is paramount.

This guide provides a comprehensive checklist for EPC contractors to meticulously review and verify an OEM-supplied anti-surge control valve design, ensuring it meets all project and industry standards.

1. Documentation and Compliance Verification

Before delving into the technical minutiae, ensure all necessary documentation is present, complete, and compliant with project specifications and international standards.

Check Point	Key Considerations
Vendor Document Register (VDR)	Confirm all required documents are listed and their submission schedule aligns with the project timeline.
Datasheet	Verify the datasheet is complete and all fields are filled. Cross-check with process data, P&ID, and control philosophy.
Piping and Instrumentation Diagram (P&ID)	Ensure the valve tag number, type, size, fail-safe position, and associated instrumentation are correctly represented.
Compliance to Standards	Verify adherence to relevant API standards, particularly API 670 for Machinery Protection Systems, which now includes guidance on surge detection. Other relevant standards may include API 6A or project-specific requirements.
Material Certificates	Request and review material certificates (e.g., EN 10204 3.1) for all wetted parts to ensure they meet the specified material requirements.
Inspection and Test Plan (ITP)	Review the OEM’s ITP to ensure all necessary inspections and tests are included and that there are opportunities for EPC and client witness points.

2. Process Data and Sizing Scrutiny

The correct sizing of the anti-surge valve is fundamental to its effectiveness. An undersized valve cannot provide the required flow to prevent surge, while an oversized valve may lead to instability and control issues at low openings.

Check Point	Key Considerations
Sizing Calculations	Independently verify the OEM’s sizing calculations. Pay close attention to the flowrate ( $C_{v}$ ) calculations for all operating cases, including start-up, normal operation, and emergency shutdown (trip) scenarios.
Operating Cases	Ensure the sizing considers the full range of operating conditions: maximum and minimum flow, temperature, and pressure at both the valve inlet and outlet.
Surge Line and Control Line	The valve must be sized to provide sufficient flow to move the compressor’s operating point away from the surge line to the more stable control line. This margin is critical.
Velocity and Noise	Check the calculated exit velocity to prevent erosion and high noise levels. The noise level should be within the project’s specified limits (typically below 85 dBA). Review any proposed noise attenuation trim designs.
Choked Flow	Verify that the valve has been sized to avoid choked flow conditions during normal modulating service, although it may be acceptable during a full trip scenario.
Turndown Ratio	The valve must be able to control effectively over the entire required operating range. A high turndown ratio is often necessary.

3. Mechanical and Material Integrity

The mechanical design and materials of construction must be robust enough to withstand the demanding service conditions of an anti-surge application.

Check Point	Key Considerations
Valve Body and Trim Materials	Verify that the materials of construction for the body, bonnet, and trim are suitable for the process fluid, temperature, and pressure. Consider potential for corrosion, erosion, and hydrogen embrittlement.
Trim Design	For high-pressure drop applications, a multi-stage or cage-guided trim is often necessary to prevent cavitation, flashing, and excessive noise and vibration.
End Connections	Ensure the end connections (flanges, butt welds) match the piping specifications in terms of size, rating, and facing.
Bonnet Type	The bonnet design (e.g., standard, extended, or cryogenic) must be appropriate for the operating temperature.
Seat Leakage	The specified seat leakage class (e.g., ANSI/FCI 70-2 Class IV, V, or VI) must be appropriate for the application. Tight shut-off is often a requirement.

4. Actuator and Positioner Performance

The speed and accuracy of the actuator and positioner are paramount for an effective anti-surge response.

Check Point	Key Considerations
Actuator Type	Pneumatic (piston or diaphragm) actuators are common. Verify the actuator is sized to provide sufficient force to overcome the maximum differential pressure and has a fast stroking speed.
Stroking Speed	The valve must be able to stroke from fully closed to the required open position in a very short time, typically 1 to 2 seconds, to prevent the compressor from entering a deep surge cycle. This is a critical parameter to verify.
Fail-Safe Action	Confirm the fail-safe action (e.g., Fail Open) as specified in the P&ID and control philosophy. This is a critical safety function.
Positioner	A high-performance, digital positioner with advanced diagnostics is essential. It should be capable of fast and precise control.
Volume Boosters/Quick Exhaust Valves	Verify the inclusion and proper sizing of volume boosters or quick exhaust valves to achieve the required stroking speed.
Air Supply System	Ensure the instrument air supply system (pressure, volume) is adequately designed to meet the demands of the fast-acting actuator.

5. Instrumentation and Control System Interface

The anti-surge valve is a key element of the compressor’s control system. Its seamless integration is vital.

Check Point	Key Considerations
Position Transmitter	A reliable position transmitter is required to provide feedback to the anti-surge controller and the Distributed Control System (DCS).
Solenoid Valves (SOVs)	If used for trip functions, ensure they are fast-acting and rated for the application.
Junction Boxes and Cabling	Verify that all electrical components and wiring meet the hazardous area classification requirements.
Anti-Surge Controller Compatibility	Confirm that the valve’s instrumentation is compatible with the dedicated anti-surge controller (e.g., CCC, Woodward).

6. Quality Assurance and Testing

Thorough testing provides the ultimate verification of the valve’s performance.

Check Point	Key Considerations
Factory Acceptance Test (FAT)	The FAT protocol should be comprehensive and include:
	– Hydrostatic testing
	– Seat leakage test
	– Functional test of the actuator and positioner
	– Stroking speed test (this is a critical witness point)
	– Dimensional checks
Specialized Testing	For critical applications, consider requesting additional tests such as fugitive emissions testing or cryogenic testing.
Painting and Coating	Verify that the painting and coating specifications meet the project’s environmental and durability requirements.

By systematically working through this checklist, EPC contractors can ensure that the OEM-supplied anti-surge control valve is fit for purpose, reliable, and will effectively protect the vital centrifugal compressor, thereby contributing to the overall safety and success of the project.

Tagged Vendor Documents Review - Guidelines