Industrial processes rely on multiple valves that require proper maintenance for sustainable operation. Valves provide means to control the direction and flow rates for different fluids. The deterioration of these devices due to mechanical stress, wear and tear, or fatigue results in inconsistent fluid flow control, increasing safety risks, and reducing the reliability of other equipment in the system.
The demand for valve maintenance varies depending on the process valve used. Each valve has unique performance characteristics affecting its durability and maintenance requirements. For instance, ball valves are preferable for most industrial processes because they are fast-acting flow control devices with fewer internal parts, and require minimal maintenance. Process engineers use valve cycles to estimate the durability of industrial valves and customize their maintenance schedules.
Although valves have an estimated lifespan, some fail earlier. The failure can occur anywhere—the valve body may rupture, seals weaken and cause leakages or emissions, or the flow control mechanism (disk, ball, or flapper) wears and becomes unresponsive to pipeline pressure changes. The premature failure is usually a result of improper valve installation, exceeding recommended valve operation limits, of poor sizing, and service media incompatibilities.
A reliable valve maintenance program prescribes timelines for routine inspections, implementing preventive measures like lubrication and cleaning, and corrective tasks like component replacements. Although maintenance increases the total cost of valve ownership, it is crucial for enhancing the efficiency and quality of industrial processes. How can facilities lower maintenance-related valve costs? Does the selection of a durable valve offset these costs?
CORRECTLY SIZE AND SPECIFY VALVES
There is a vast number of different valves in the market, ranging from manually-operated ball valves to solenoid valves. These valves are available in different sizes to suit any industrial fluid application. The availability of options in the market complicates the selection process—several valve types can perform the same function, but only one particular alternative is the most suitable for each fluid application and a certain role in the pipeline. Proper valve sizing and specification extend durability and can minimize costly valve failures.
When sizing valves, process engineers need to calculate the optimal fluid flow conditions, factors of safety, and the desired valve characteristics, including sealing efficiency and sensitivity. Once they define these properties, they explore the operating principles of different valve options. It helps them to narrow down their choices and optimize valve sizes. Manufacturers assign pressure and temperature classes to every valve in their catalog. However, engineers cannot depend solely on these specifications to select process valves. They must evaluate other fluid flow conditions like viscosity, fluid velocity, allowable pressure drops, and temperature variations.
For example, using a smaller valve in an industrial process increases its risk of failure. The valve is subjected to high flow velocities that increase internal valve wear and tear rates. The valve also limits fluid flow quantities past it, increasing congestion. An oversized valve is more sensitive to pipeline operating conditions and can result in inconsistent flow rates, affecting the quality of subsequent processes. Oversized valves are more susceptible to water hammer, which compromises the valve stem leading to premature damage caused by repetitive stress.
Proper valve sizing optimizes flow rates, and reduces the impact and effect of flow-related component wear. It also reduces friction on the sealing components, guaranteeing valve reliability in the longer term. It helps companies to decrease valve failures, the frequency of repairs and component replacements, thus reducing maintenance costs.
CONFIRM THE QUALITY OF VALVE MATERIALS
The choice of valve materials significantly affects its durability. Industrial valves convey fluids bearing different physical and chemical characteristics. Some fluids are acidic, while others contain suspended particles that raise their viscosities. Process engineers also deal with several process variables that can alter the stability of valve materials.
For example: If a valve is required to sustain elevated process temperatures and fluctuating fluid pressure, the build material for all the components must be compatible with the service media and the required conditions.
How is a ball valve designed for chemical or cryogenic fluid service different from the one used for potable water service? Potable water valves should provide excellent shutoff characteristics and utilize durable, non-hazardous materials that do not impact human health. Valve materials for water distribution should be corrosion-free and meet the minimum chemical resistance requirements. Extreme fluid service requires valves with excellent chemical resistance and strength. These processes handle highly corrosive fluids and operate at high temperatures and pressure. Cryogenic applications operate at very low temperatures. These conditions can deteriorate valves rapidly.
When choosing industrial valves, process engineers must understand the qualities of the service fluids, and the level of temperature and pressure fluctuations in the system. It allows them to identify the most compatible valve materials. Internal valve components, including closure mechanisms, packings, stems, and seals, should provide adequate chemical and frictional resistance to fast-moving service media. They must sustain duty cycles without failure, and depict consistent performance as the operating conditions change.
The valve body should be fabricated using resilient materials that accommodate extreme temperature and pressure changes. A weaker valve shell may rupture due to increased fluid pressure and frequent thermal expansion and contraction. The correct quality of materials extends the useful lives of valves and enhances their safety. The valve will offer predictable performance while lowering the need for frequent repairs to replace worn-out components or overhaul valves.
USE THE RIGHT ACTUATION MECHANISMS
Automating the operation of industrial valves enhances their performance and provides more consistent flow control through different types of actuators. The choice of the actuator depends on the availability of power, the size of the valves, and torque requirements. Multiple mechanisms for automating valves include electric, hydraulic, and pneumatic actuators. Each actuator has its advantages that also influence the selection process.
Using the wrong actuator size increases the demand for valve maintenance. To size actuators correctly, process engineers should calculate the limits of fluid supply pressure in the system, and the required valve operation torque. They also need to evaluate the desired temperature variations and stem packing friction limits to estimate torquing requirements. In the end, engineers should select the right size of an actuator, actuators that operate valves at required speeds, are safe, and cost-effective to run and maintain.
An oversized actuator delivers excessive torque that can easily damage valve stems. It also increases energy consumption and the cost of the actuator. An undersized actuator struggles to deliver valve actuation forces. It causes erratic fluid control and impedes emergency valve shutdown procedures. It increases the probability of valve and other equipment failures, raising maintenance costs further. The correct actuator sizing enhances valve operations and reduces failures and component breakdowns that can increase process downtimes and repair costs.
IMPLEMENT A PREDICTIVE VALVE MAINTENANCE PROGRAM
Modern facilities are implementing digital technologies to improve the autonomy and quality of industrial processes. The utilization of these technologies transforms asset maintenance strategies and schedules. Implementing these technologies is equally beneficial to valve operations and maintenance. Some companies may still rely on a run-to-failure valve maintenance strategy, which is costly and increases safety risks.
Companies can enhance the durability of valves and minimize maintenance costs by establishing a predictive maintenance program. By installing industrial sensors, and leveraging existing data networks to monitor the performance of valves in real-time, they can identify potential valve defects using this abundance of data. The sensors monitor vibrations, temperature fluctuations and flow rates, and generate alerts when changes exceed the recommended limits.
Through predictive maintenance, companies can identify and rectify valve defects in good time. That reduces maintenance workloads and the number of replacement parts. Such strategies can significantly minimize valve maintenance costs.
Companies can reduce the total cost of valve maintenance by choosing the right valve sizes made using high-quality materials. They can reduce maintenance costs by establishing the best valve installation, operation, and maintenance practices. Operators should adhere to the recommended valve operating procedures and implement proactive measures to reduce the level of damage. Companies should also allocate sufficient valve maintenance budgets to ensure teams have access to the correct inspection tools, technologies, and spare parts whenever needed.
FOR MORE INFORMATION
Gilbert Welsford Jr. is the founder of ValveMan.com and a third-generation valve entrepreneur. He has learned valves since a young age and has brought his entrepreneurial ingenuity to the family business in 2011 by creating the online valve store. Welsford’s focus is building on the legacy his grandfather started, his father grew, and he has amplified.
MODERN PUMPING TODAY, November 2022
Did you enjoy this article?
Subscribe to the FREE Digital Edition of Modern Pumping Today Magazine!