Valves such as ball valves, plug valves and butterfly valves continue to be of crucial importance in reliably controlling the inflow of process media, particularly in chemical or petrochemical processes. The automated actuation of these valves, which are often summarised as “quarter turn valves”, using electric and above all pneumatic actuators offers plant operators numerous advantages.
The valves can be opened and closed remotely. The user can also check their current position at any time via the system control without direct access. This saves working time, especially in difficult-to-access or large, complex installations. When used in hazardous areas, remote control also offers greater safety for system operators. In addition, operation is usually faster than manually using a handwheel or lever. And in emergency situations, the valve can automatically assume a safety position.
Demand for automation solutions is growing accordingly among suppliers such as Armaturen Vertrieb Alms GmbH. When realising customer requirements, the wholesaler for industrial valves often combines components from different manufacturers to create a suitable overall package. “In many process applications, automated shut-off valves are an ideal addition to our extensive portfolio of manual valves”, explains Frank Alms, Managing Director of the family-run company. “Our customers benefit from short delivery times, which we realise thanks to very large stocks of standard components.”
Valve automation for safety-relevant applications
AVA first invested in an expansion of storage capacity to 11,000 square metres at its German headquarters in Ratingen in 2023. Thanks to close partnerships with the relevant drive manufacturers, vendor parts are also always available at short notice and reliably. If the worst comes to the worst, AVA is able to offer particularly fast replacements for failed system components and help to get the system up and running again quickly - effectively reducing interruptions to production.
Before the ready-to-install valves are delivered, production is certified in accordance with ISO 9001, ISO 14001 and ISO 45001. Technical customer specifications set the tone for a customised design that integrates smoothly into existing industrial environments and control systems. Based on the specifications for line diameter, control pressure, connection standards and possible explosion protection requirements, the valve, actuator, solenoid valve and sensor assemblies are designed, constructed and assembled entirely in-house.
The vast majority of automated shut-off valves manufactured by AVA have a pneumatic actuator for opening and closing. “Single-acting and double-acting double-piston quarter-turn actuators offer a very efficient and safe solution for automated actuation”, explains Martin Klug, Head of Automation at AVA.
Reliable in any environment
“As our valves are mostly used in safety-relevant applications in the chemical or petrochemical industry, we primarily install actuators that immediately switch to a predefined safety position in the event of a power supply failure.” Whether this is open or closed depends entirely on the application in question. “It is crucial that a safety system is set up that safely interrupts the process in the event of a drop in control pressure or loss of the electrical power supply”, says the expert. For example, the filling process of a boiler or reactor can be stopped automatically - safety position “closed” - or pressure relief can be initiated - safety position “open”.
Single-acting actuators are used in both cases. They are only moved in one direction with control air or a neutral, inert gas. They are moved in the opposite direction by spring force. The end stop of the spring-loaded direction then defines the safety position. In some applications, the actuator even holds the valve permanently in this position. Only if the control air fails does the actuator immediately move to the fail-safe position.
With double-acting actuators, both opening and closing are operated with compressed air. The actuator then remains in its current position in the event of a power failure. Regardless of the design, solenoid valves control the compressed air and thus the direction of movement of the actuator and valve. Depending on the application, they are flanged directly to the actuator as NAMUR solenoid valves or mounted externally and connected via a pipe. They are electrically controlled via the PLC of the overall system. In corrosive environments - such as in a maritime climate or in an atmosphere containing chlorine - where the penetration of ambient air into the actuator is to be prevented, the spring chamber can also be pressure equalised with exhaust air from the solenoid valve. If necessary, the incoming control pressure is adjusted using a pressure reducer. A limit switch box at the top of the assembly houses the sensors for detecting the current position of the actuator and valve. From there, the signal is transmitted to the controls of the entire system.
Every unit delivered is comprehensively documented and subjected to an independent internal functional test. As proof of quality assurance, the customer receives a detailed, customised functional test report. This comprehensibly records all relevant specifications, such as safe functionality at the specified control pressure, perfect signalling of the end positions or the correctness of the safety position.
