Industrial valves · Части клапана

Engineering Analysis of Pipeline Valve Components and Materials

A pipeline valve is a precision engineering device designed to control the flow of the working medium. Its reliability and durability are determined by the quality of its key components. The main structural elements include: body, bonnet, and trim, which includes the disk, seat, and stem. EV Group China manufactures cast and forged valves with flanged, threaded, or welded connections, in accordance with design requirements.

Valve Body: Materials and Manufacturing Technologies

The body is the main load-bearing element, absorbing the pressure of the working medium and external loads from the pipeline. It ensures the tightness of the entire structure. Investment casting and hot die forging (forging) technologies are used for its manufacture, which guarantees specified mechanical properties and geometry.

In the oil and gas industry, for high-temperature operating conditions, carbon steels ASTM A216 (cast bodies) and ASTM A105 (forged) are de facto standard. For cryogenic applications, where impact toughness must be maintained at extremely low temperatures, EV Group China uses specialized steels ASTM A352 (grades LCB/LCC) and ASTM A350 (grades LF2/LF3).

For operation in corrosive environments, austenitic stainless steels ASTM A351 CF8/CF8M (cast) and ASTM A182 F304/F316/F321/F347 (forged) are used. In extreme conditions characterized by high chloride or hydrogen sulfide content, super austenitic alloys (SMO 254), duplex steels (F44, F51, F53, F55), and nickel superalloys (Inconel, Incoloy, Hastelloy) are applied. For offshore platforms and systems operating with seawater, copper-nickel alloys such as Monel, Cupronickel, and Aluminum Bronze are optimal choices.

Types of Pipeline Connections: Engineering Choice

The choice of end connection type is a critical parameter that determines the method of integrating the valve into the pipeline system and the reliability of the assembly.

Flanged connections (ASME B16.5 standard) provide for disassemblability of the unit for inspection and repair, being the preferred solution for large diameter (DN) valves.
Welded connections (butt weld according to ASME B16.25 or socket weld according to ASME B16.11) create a non-separable, fully sealed unit, eliminating the risk of leaks. This method is mandatory for high-pressure systems and toxic media.
Threaded connections (NPT/BSP standards) are used for small diameter valves in low-pressure systems where strict requirements for tightness and vibration resistance are not imposed.

Bonnet Designs

The bonnet seals the body and provides access to the internal components of the trim for maintenance. Depending on the pressure class and valve type, bolted, welded, or pressure seal designs are used. The bonnet material is typically identical to the body material to ensure uniform thermal expansion.

Trim: The Heart of the Valve

The trim combines components that directly contact the working medium and perform the function of regulating or shutting off the flow. These include the disk, seat, and stem. The selection of materials for the trim is regulated by the API 600 standard and is a key factor determining resistance to erosion, corrosion, and cavitation, which directly affects the valve's service life.

Disk and Seat: Ensuring Tightness

The disk is a movable element that directly blocks the flow area. Its geometry depends on the valve type: wedge in gate valves, ball in ball valves. The seat is a stationary sealing surface in the body that the disk contacts in the closed position. EV Group China uses precision machining and hardfacing of seats with hard alloys (e.g., Stellite) to achieve the highest tightness classes according to API 598.

Stem: Transmitting Control Force

The stem transmits torque or linear force from the actuator to the disk. Main structural designs: rotary (for ball and butterfly valves), sliding, rising (OS&Y - Outside Screw and Yoke), and non-rising (IS&Y - Inside Screw and Yoke). The choice of stem design (e.g., OS&Y) is critical for visual monitoring of the closure position and protecting the threads from the working medium.

Sealing and Automation Systems

The packing assembly ensures stem sealing, preventing leakage of the working medium into the atmosphere. Graphite, PTFE, and other sealing materials are used. For automation of technological process control, valves are equipped with actuators (electric, pneumatic, hydraulic). EV Group China engineers calculate and select actuators from leading global manufacturers such as Rotork and Auma for integration into the customer's APCS systems.