About Us

As global engineering projects in water treatment, oil & gas, power generation and chemical industries keep expanding, gate valves act as core pipeline isolation equipment. They cut off or connect fluid media reliably to protect pipelines, pumps, instruments and other key facilities. Assembly quality directly determines sealing performance, switching flexibility and long-term operational stability of gate valves. Working under severe service conditions such as high pressure, high temperature and frequent operation, international clients put stringent requirements on gate valve assembly workmanship.

As a professional manufacturer of industrial fluid control equipment, Yaxing Valve has built a standardized full-process gate valve assembly workflow. Every gate valve undergoes strict sequential assembly and intermediate inspection before pressure testing, to eliminate assembly defects and deliver fully qualified isolation valves for worldwide engineering projects.

Yaxing Valve adheres to the core philosophy that “quality lies in rigorous verification, and reliability comes from strict testing”. Precision assembly is defined as a vital quality control node after CNC machining and before hydrostatic pressure test. Unlike small-size gate valves, large-bore gate valves feature heavy cast bodies, large bonnet flanges and big gate plates. Contamination on sealing faces, misaligned valve seats, uneven bolt tightening or improper packing installation may lead to medium leakage, jamming or seal failure once the valve is put online. Cross-border EPC projects require compliance with unified international manufacturing specifications. To prevent these risks, Yaxing Valve equips dedicated heavy-duty assembly stations customized for DN50–DN2000 gate valves. All assembly operations follow GB/T 12234 national standard and API 600 international specifications, supporting customized assembly procedures for different materials, pressure classes and actuator configurations.

The complete assembly workflow covers component pre-inspection, seat installation, gate & stem assembly, bonnet mounting, packing installation, handwheel/actuator fitting and pre-operation functional check, realizing multi-dimensional quality control for gate valves.

Component Pre-Inspection & Cleaning: The First Gate of Assembly

All machined components including valve body, bonnet, gate plate, valve seat, valve stem, gaskets, packing and fasteners must pass incoming inspection before assembly. Inspectors check material certificates, dimensional tolerance and surface quality. Any burr, machining chips, casting residue or scratches on sealing surfaces must be thoroughly cleaned. Damaged or unqualified parts are rejected directly and will not enter the assembly line. Cleanliness protection avoids foreign particles trapped on sealing faces, which is the foundation of zero-leakage performance.

Valve Seat Installation: Secure Sealing Base

Qualified valve seats are pressed and positioned into the valve body cavity according to process torque requirements. Technicians check seat flatness and contact clearance to guarantee full fit between seat sealing face and gate plate. Improper seat positioning will cause uneven contact and early leakage under pressure. This step establishes the primary sealing pair for the gate valve.

Gate & Valve Stem Assembly: Ensure Smooth Opening & Closing

The gate plate is mounted onto the valve stem, with connecting pins and locking components installed and secured. Technicians test the cooperation between stem thread and gate plate, confirming no stuck, tilt or offset during lifting and lowering movement. For double-disc gate valves, parallelism of two gate discs is adjusted to ensure uniform contact with both seat faces. This assembly step guarantees flexible and accurate valve stroke movement.

Bonnet Mounting & Mid-flange Fastening

After gate and stem assembly, the bonnet gasket is placed correctly, then the bonnet is aligned and fitted onto the valve body. All flange bolts are tightened in cross sequence in three stages (50% → 80% → 100% target torque) to realize uniform gasket compression. This symmetric tightening method prevents flange warping and uneven gasket stress, avoiding mid-flange leakage under rated pressure.

Packing Installation & Gland Adjustment: Stem Dynamic Sealing

Packing rings are filled layer by layer inside the stuffing box, then the gland and gland flange are fitted and adjusted to proper compression. The compression force must be balanced: enough to stop fluid escape along the valve stem, without generating excessive friction that hinders valve operation. This ensures reliable dynamic sealing while keeping stem movement smooth during repeated opening and closing cycles.

Actuator / Handwheel Fitting & Functional Pre-check

For manual gate valves, handwheel is installed and fixed. For motorized, pneumatic or hydraulic gate valves, actuators are mounted and calibrated. Technicians adjust valve stroke, limit switches and opening indicator. Multiple full-stroke open-close cycles are carried out to verify the valve operates smoothly, without jitter, abnormal noise or position deviation. Any movement abnormality will be corrected before the valve moves to pressure testing.

Assembly Records & Traceable Quality Documentation

Standardized assembly records are essential for overseas project acceptance and full product traceability. Yaxing Valve assigns exclusive serial numbers to every gate valve. Certified inspectors record complete assembly data: valve model, nominal diameter, pressure class, material grade, bolt torque values, stroke test results and inspector signature. Photos of key assembly stages are archived. All assembly documents can be provided in bilingual versions to satisfy international engineering requirements.

The full documentation chain supports third-party witness inspection and factory acceptance test (FAT). It blocks products with assembly defects from entering pressure testing and shipment, greatly simplifying quality audits for EPC contractors.

From precision casting, CNC machining, sequential assembly to subsequent hydrostatic pressure testing, every manufacturing link safeguards gate valve reliability. Market competition for gate valves is no longer only about material compliance and dimension accuracy; it depends on stable sealing and cycle performance verified by standardized assembly.

Yaxing Valve keeps upgrading assembly workstations and training professional assembly teams. Besides continuous optimization of casting and machining technology, multi-stage intermediate inspections during assembly capture potential assembly defects at an early stage, ensuring flexible operation and reliable sealing of gate valves.

Going forward, Yaxing Valve will continue to optimize the assembly process to adapt to diverse international standards and complex working conditions. Through rigorous full-process quality assurance, Yaxing Valve supplies high-performance gate valves for water conservancy, power, chemical and oil & gas projects worldwide, and keeps promoting high-quality development of the industrial fluid equipment sector.