III. Manufacturing Process & Quality Assurance
The production of the TIANYU 2” 600LB DBB ball valve adheres to the most rigorous manufacturing processes and quality control protocols in the industry, aligning with API 6D, ASME B16.34, and ISO 9001:2015 standards to ensure every valve meets or exceeds design specifications and global industry requirements. From raw material procurement to final factory testing, every step of the manufacturing process is controlled and documented, with a focus on precision, consistency, and reliability—critical for a valve designed for high-pressure, critical isolation applications.
Raw Material Procurement & Inspection
Raw materials for the valve—A105 carbon steel billets and DEVLON polymer—are sourced exclusively from approved, ISO 9001-certified suppliers with a proven track record of producing high-quality materials for the oil and gas and petrochemical industries. All raw materials are accompanied by a mill test certificate (MTC) that verifies chemical composition, mechanical properties, and compliance with ASTM A105 (for A105 carbon steel) and proprietary DEVLON material specifications. Upon receipt, the raw materials undergo rigorous incoming inspection in TIANYU’s state-of-the-art quality control laboratory, including:
- Chemical composition analysis via optical emission spectroscopy (OES) to verify compliance with ASTM standards;
- Mechanical property testing (tensile strength, yield strength, elongation, hardness) via universal testing machine (UTM) and Brinell hardness tester;
- Non-destructive testing (NDT) including ultrasonic testing (UT) and magnetic particle testing (MPT) to detect internal and surface defects;
- For DEVLON, additional testing to verify chemical resistance, wear resistance, and thermal stability.
Any raw material that fails to meet the specified requirements is rejected and returned to the supplier, ensuring only high-quality materials are used in production.
Body & Ball Fabrication
The valve body is manufactured using a hot-forging process, where A105 carbon steel billets are heated to high temperatures (1100-1200°C) and shaped under extreme pressure using precision dies. This process enhances material density, eliminates internal defects such as porosity or inclusions, and improves mechanical properties, including tensile strength and impact resistance. After forging, the body undergoes normalization heat treatment (900-920°C) followed by air cooling, to refine its microstructure and relieve internal stresses, ensuring consistent performance across the component. The body is then machined to precise dimensions using CNC lathes and milling machines, with critical surfaces such as the ball cavity, stem bore, and flange faces finished to a roughness of Ra ≤ 3.2 μm to ensure proper sealing and alignment.
The ball is manufactured from A105 carbon steel or stainless steel, using a precision forging process followed by CNC turning and milling to achieve the required spherical shape and dimensional accuracy. The ball is then lapped and polished to a surface finish of Ra ≤ 0.8 μm, ensuring optimal sealing performance with the DEVLON seat assembly. After machining, the ball undergoes heat treatment to enhance its mechanical properties and corrosion resistance, ensuring long-term performance in high-pressure applications.
Seat & Stem Production
The DEVLON seats are fabricated from high-grade DEVLON polymer, which is molded and machined to precise dimensions using CNC lathes and milling machines. The sealing surface is polished to a roughness of Ra ≤ 0.8 μm, ensuring a tight, leak-proof seal with the ball surface. Each seat undergoes dimensional inspection and material testing to verify compliance with chemical resistance and wear resistance specifications. The stem is machined from A105 carbon steel or stainless steel using CNC lathes, with critical surfaces such as the sealing area and thread finished to tight tolerances to ensure compatibility with the packing system and ball connection.
Assembly & Testing
The valve assembly process is conducted in a controlled, clean environment to prevent contamination of internal components, with skilled technicians following detailed, step-by-step assembly work instructions. The assembly process involves:
- Installing the DEVLON seat assemblies into the valve body cavity;
- Inserting the ball into the body, ensuring proper alignment with the seats;
- Installing the stem through the bonnet packing and connecting it to the ball via a square drive or keyed connection;
- Mounting the bonnet to the body and torquing the bonnet bolts to the specified value using a calibrated torque wrench;
- Installing the stem packing system, including graphite or PTFE packing rings, to ensure a leak-proof seal;
- Attaching the manual handle and position indicator, and calibrating the position indicator to align with the ball’s open/closed status;
- Installing the bleed valve assembly and connecting it to the central cavity between the two isolation balls;
- Lubricating all moving parts with a high-performance, high-temperature grease compatible with the valve’s materials.
During assembly, critical dimensions and clearances are verified using precision measurement tools, including coordinate measuring machines (CMMs), dial indicators, and calipers, to ensure compliance with design specifications.
Factory Testing & Certification
Before leaving the factory, every TIANYU 2” 600LB DBB ball valve undergoes a comprehensive series of performance tests in accordance with API 6D, API 598, and ISO 5208 standards, with all test results documented in a factory test certificate (FTC) provided with each valve. The testing program includes:
- Shell Test: A hydrostatic pressure test conducted at 1.5 times the rated 600LB pressure (15.51 MPa) for a minimum of 30 seconds, to verify the body’s structural integrity and no visible leakage or deformation;
- Seat Test (Hydrostatic): A hydrostatic pressure test of the seat assemblies at 1.1 times the rated pressure for both upstream and downstream flow directions, to verify compliance with ANSI/FCI Class VI leakage standards;
- Seat Test (Pneumatic): A pneumatic pressure test at 0.69 MPa (100 PSI) to verify the soft-seal’s integrity in low-pressure applications;
- DBB Function Test: A functional test to verify the double block and bleed functionality, ensuring the two isolation balls can be closed independently and the bleed valve can safely vent trapped pressure;
- Operational Test: A functional test of the manual handle to verify smooth opening and closing, accurate position indication, and positive locking;
- Fugitive Emission Test: A test of the stem packing system in accordance with ISO 15848-1, to verify emissions are below the specified limit (≤ 100 ppm for Class A);
- Fire-Safe Test: A third-party fire test in accordance with API 607 and API 6FA to verify the metal-to-metal backup seal maintains integrity after fire exposure.
Only valves that pass all tests are certified and released for shipment, with the FTC including all test results, material certifications, and compliance standards for full traceability.
Quality Management System
TIANYU maintains a certified quality management system (QMS) compliant with ISO 9001:2015 and API Q1, the oil and gas industry’s premier quality standard for manufacturing facilities. The QMS covers all aspects of the manufacturing process, from raw material procurement to final delivery, with a focus on continuous improvement, customer satisfaction, and compliance with global industry standards. The QMS is supported by a team of experienced quality assurance (QA) engineers who conduct regular internal audits, process reviews, and supplier audits to ensure compliance, and a document control system that maintains all manufacturing, testing, and certification records for a minimum of 7 years—meeting the traceability requirements of the oil and gas industry.
