New Pig Passability Test Standards for Ball Valves Released

I. The Importance of Full-Bore Ball Valve Pig Passability Testing

Ensuring Pipeline Cleaning Efficiency

Pigs must operate continuously for hundreds of kilometers within pipelines. If there are constrictions or steps in the valve passage, the pigs can become stuck or wear out, compromising maintenance operations such as wax removal, water removal, and inspection.

Avoiding the Risk of Production Interruptions

In natural gas and crude oil transportation, pig jamming can cause a sudden drop in flow, even requiring a pipeline shutdown for treatment, resulting in significant economic losses.

Meeting Industry Certification Requirements

Standards such as API 6D and GB/T 12237 explicitly require full-bore ball valves to undergo a pig passability test as a necessary verification step before product delivery.

II. Key Technical Requirements for Pig Passability Test

Test Conditions

* Pig Specifications: Diameter 95%-100% of the valve's nominal inner diameter (e.g., a DN300 valve requires a φ285-φ300 pig);

* Test Medium: Water or air, pressure ≤ 0.6 MPa;

* Valve State: Fully open, actuator-pipeline connection coaxiality error ≤ 2 mm;

* Ambient Temperature: Room temperature (extreme temperature simulation may be required for special operating conditions).

Test Equipment Configuration

* Pig Transmitter/Receiver: Includes a pressure buffer tank and signal trigger system;

* Monitoring System: High-speed camera (records the pig passability process), pressure sensor (monitors differential pressure changes);

* Auxiliary Tools: Magnetic particle detector (detects valve body scratches), endoscope (observes internal structure).

Test Procedures

* Pre-inspection: Measure the valve inner diameter and sealing surface clearance to ensure there are no burrs or weld residue.

* Static Ball Pass: Manually push a pig through the valve to check for mechanical interference.

* Dynamic Test: Simulate medium flow at a pressure of 0.2-0.6 MPa, recording pig passage time and pressure differential.

* Post-inspection: Disassemble the valve to inspect sealing surface wear and pig integrity, and take photos of any residual material.

* Acceptance Criteria

---Pig passage time ≤ 5 seconds (DN ≤ 600) or ≤ 8 seconds (DN > 600);

---Pressure differential fluctuation ≤ 0.1 MPa;

---No tearing or deformation of the pig, no scratches on the valve inner wall (depth ≥ 0.5 mm);

---No abnormal noise or sticking.

III. Structural Optimization Recommendations for Full-Bore Ball Valves

* Flow Channel Design

• Use an eccentric ball + dual-piston sealing structure to eliminate the step between the valve seat and the ball;
• Increase the flow guide angle (angle ≥ 30°) at the connection between the valve stem and the valve body to prevent pig impact.

* Material Selection

• Spray tungsten carbide or ceramic coating (hardness ≥ HRC60) on the sealing surface to reduce the coefficient of friction;
• The valve body is formed using a one-piece forging process to reduce the risk of welding deformation.

* Manufacturing Precision Control

• Internal diameter machining tolerance ≤ ±1mm (DN ≤ 400) or ±1.5mm (DN > 400);
• Use a laser alignment tool during assembly to ensure concentricity between the ball and the valve seat ≤ 0.1mm.

1. Maintenance and Verification Recommendations
2. Regular Re-Inspection

* Perform an online pig passability test every three years after commissioning;

* Use an intelligent pig equipped with ultrasonic thickness measurement to simultaneously monitor the corrosion of the valve body inner wall. 2. Digital Management

* Establish a full lifecycle archive for valves, recording data from each test;

* Apply CFD simulation technology to optimize pig path planning.

3. Track Standard Updates

* Monitor the new proposals from the ISO/TC 184/SC 5 Working Group on intelligent testing for full-bore valves;

* Participate in the revision of the API 6D standard to master the latest test methods.

Pig passability testing of full-bore ball valves is a critical step in ensuring the safe operation of long-distance pipelines. By strictly adhering to API, GB, and other standards, optimizing structural design, and implementing test verification, operational and maintenance risks can be significantly reduced. With the application of intelligent pigs and digital twin technology, future full-bore ball valve passability testing will evolve towards high-precision, predictive maintenance.