Industrial valves · Детали трубопроводных задвижек и затворов, включая затворы по API

Engineering Analysis of the Design and Components of Baihu Industrial Valves

Engineering Analysis: Key Components of Industrial Valves

An industrial valve is a precision-engineered product consisting of many functional units. The key components — body, bonnet, closure element (disk, wedge), seat, stem, stem packing assembly, and fasteners — are manufactured as individual parts with subsequent high-precision assembly at EV Group China manufacturing facilities. For each element, strict tolerances are set for geometry and surface quality, which is fundamental for achieving the required sealing class and operational reliability.

Valve Body: The Structural Power Element

The body is a fundamental structural component that bears all loads from the pressure of the working medium and the pipeline. Its internal geometry forms the flow channel and contains seating areas for the closure element. Depending on the design pressure and temperature regimes, EV Group China bodies are manufactured by casting, forging, or welding from standardized blanks. The choice of steel grade is determined by the chemical aggressiveness of the transported medium and the requirements for cold resistance.

The integration of the valve into the pipeline system is realized through standardized connection types: flanged (according to ASME/GOST), threaded (NPT/BSP), weld-end (BW/SW) or socket-welded. For compact systems, a wafer type mounting is also used.

The flow part is designed based on the functional purpose of the valve:

• Reduced bore body: The nominal diameter (DN) of the seats is smaller than that of the connecting pipes. This design is used to reduce the weight, dimensions, and cost of the valve in systems where an increase in hydraulic resistance is not critical.
• Full bore body: The diameter of the flow cross-section of the seats is equivalent to the internal diameter of the connected pipeline. This ensures minimal hydraulic losses and allows for unimpeded passage of in-line diagnostic and cleaning devices (scrapers, “pigs”).
• Split body: A design consisting of two or more parts joined by bolts. This design is typical for ball valves and some types of check valves, as it facilitates the installation and maintenance of internal elements.

Valve Bonnet: Sealing and Actuator Support

The bonnet seals the upper opening of the body, creating a closed, pressure-resistant volume. It also serves as a base for mounting the stem control assembly (yoke assembly) and the actuator.

Structurally, bonnets are made removable (for servicing the closure element) or as a single unit with the body in all-welded models. The “body-bonnet” assembly with bolted, threaded, or welded connection is a high-responsibility area where tightness is ensured by gaskets and the precision of the mating surfaces. To prevent temperature deformations and stresses, the bonnet material always matches the body material.

Trim: The Functional Core of the Valve

The term “trim” in international practice refers to the set of internal components that directly control the flow and come into contact with the working medium. The basic trim composition includes: a movable closure element (disk, wedge, ball, plunger), stationary sealing rings (seats), and a stem. Depending on the valve design, the trim may also include guide bushings, relief springs, and other elements subject to wear and corrosion.

“Disk-Seat” Pair: The Shut-off Unit

The disk is the movable element of the trim, which, by moving, blocks or regulates the flow. Its shape (wedge, globe, ball) determines the hydraulic characteristics and functional purpose of the valve. The seat is a stationary ring in the body with which the disk contacts to create a tight shut-off. The contact surfaces of the “disk-seat” pair undergo precision machining (grinding, lapping) and are often hardened by hard-facing with hard alloys (e.g., Stellite) to ensure wear resistance and the required sealing class according to API/GOST. For less severe conditions, seats with elastomeric seals are used.

Stem and Actuator Assembly: Transmission of Control Force

The stem is a rod that converts the rotational or linear motion from the actuator (handwheel, gearbox, electric actuator) into the movement of the disk. To ensure strength and corrosion resistance, stems are made from hardened stainless steels (e.g., AISI 410, 17-4PH). The connection of the stem to the actuator and disk is carried out through couplings and crossheads, which transmit axial force and torque. To minimize friction and control forces, anti-friction materials and thrust bearings are used in the yoke assembly.

Standardization of Trim Materials according to API: Trim Number

To unify and correctly select materials for trim components under specific operating conditions, API 600 standard introduces the “Trim Number” system. This number uniquely codes the combination of materials for the stem, disk, seats, and back seat, which eliminates errors during ordering and ensures compliance of the valve with project requirements. EV Group China strictly adheres to this classification.