The chemical industry is one of the most demanding sectors from a component engineering standpoint. Its processes involve the handling of highly corrosive fluids, extreme temperatures, elevated pressures and, in many cases, the simultaneous combination of several of these factors. Industrial valves are not merely flow control elements — they are components whose failure can compromise the integrity of the installation, the safety of personnel and the operational continuity of the plant. Understanding what the chemical industry truly demands of its valves is the starting point for specifying correctly and avoiding costly problems in operation.
A working environment out of the ordinary
Unlike other industrial sectors, the chemical industry rarely works with inert or benign fluids. Process media include strong acids, concentrated alkalis, organic solvents, toxic or flammable gases and mixtures containing abrasive particles in suspension. Each of these fluids generates a different degradation mechanism in metallic materials: generalised corrosion, intergranular corrosion, stress corrosion cracking, erosion by cavitation or hydrogen embrittlement, among others.
Added to all of the above is the thermal demand. Many chemical processes operate at temperatures exceeding 300 °C, whilst others require components to maintain their mechanical integrity and sealing performance at temperatures well below zero — such as those involving liquefied gases or cryogenic applications. Cryogenic valves, for example, require designs with specific stem extensions and materials that retain their toughness at low temperatures, where conventional steels can become brittle.
Material selection: the key to durability
Given the hostility and severity of the environment, the choice of material for the valve body, seat and closure element is decisive. Standard carbon steel is ruled out in the majority of chemical applications, and the reference materials are austenitic stainless steel and, when conditions are more demanding, special alloys such as duplex and super duplex for chloride-rich environments, Inconel for high-temperature service with acid presence, Hastelloy for media containing hydrochloric or concentrated sulphuric acid, and stellite for seating areas subjected to severe wear.
Correct selection depends not only on the fluid, but also on the operating temperature, fluid velocity and type of service. A valve specified solely on the basis of body material, without taking into account the behaviour of that material at the actual service temperature, may fail prematurely even if its chemical composition appears adequate on paper.
Sealing requirements and standards
The chemical industry also imposes strict sealing requirements on valve closure. The applicable reference standards define testing criteria, but in applications involving toxic or hazardous fluids, manufacturers and end users typically demand more restrictive standards, with leakage rates that are practically zero.
The quality of the machining of seats and closure elements is directly responsible for achieving and maintaining these sealing levels across thousands of operating cycles. An inadequate surface finish, a geometric tolerance out of range or an incorrect taper on the seat can result in premature leakage that forces unplanned maintenance shutdowns.
Types of valves most commonly used in the chemical industry
Whilst selection always depends on the specific process, certain valve types account for the majority of applications in chemical plants. Globe valves are the standard solution when precise flow regulation is required. Gate valves and butterfly valves are used primarily for isolation, with different selection criteria depending on nominal diameter, service pressure and fluid aggressiveness. Check valves protect equipment from reverse flow in lines where backflow can have serious consequences. In high-pressure applications with hazardous fluids, forged valves are the standard, as their manufacturing process eliminates the internal porosity of castings and guarantees greater mechanical strength. And when temperature, corrosion or pressure conditions fall outside conventional ranges, it is special valves — with high-alloy materials and geometries adapted to the process — that provide the appropriate technical response.
The role of precision machining
The quality of an industrial valve is not determined solely at the point of original manufacture. In many cases, valve bodies — whether forged or cast — arrive at the machine shop for final finishing or for repair and reconditioning after years of service. In both cases, machining is the process that defines the final geometric precision of the critical components: seats, closure elements and joint surfaces.
Working with special alloys adds considerable technical difficulty. Materials such as Inconel or duplex behave very differently under machining conditions compared to conventional steel: greater work hardening, a higher tendency for tool wear and greater sensitivity to cutting parameters. Having the experience, technical resources and appropriate tooling for these materials makes the difference between a component machined within tolerance and one that compromises the reliability of the valve in service.
ARRI: decades of machining valves for critical environments
At Talleres Mecánicos ARRI we have spent over three decades specialising in the machining of industrial valves for the most demanding sectors: oil & gas, nuclear, petrochemical and process chemistry. Our facilities in Beasain (Gipuzkoa) are equipped with Trevisan machining centres capable of handling parts from 2 inches up to Ø2,400 mm and 25 tonnes, enabling us to tackle both medium-sized valves and large-format projects to the same precision standards.
We routinely work with stainless steel, Inconel, duplex, super duplex, stellite and other special alloys, adapting our processes and tooling to the requirements of each material and each client. Our ISO 9001 certification underpins a management system oriented towards continuous improvement and full traceability for every machined part.
If you have a project in the chemical industry requiring high-demand valve machining, tell us about it. Our technical team will analyse your requirements and offer a solution tailored to your timescales and specifications.
