THE BASICS OF INDUSTRIAL PIPING SYSTEM VALVES
In an industrial system, and in any piping system, valves are used to restrict, stop or control the flow of fluid. More specifically, some industrial valves are used to:
- Control the cooling rates of water through cooling lines to regulate the temperature.
- Manage the flow of concentrated acids or bases flowing through a line.
- Redirect flow from one line to another at a three-way valve.
- Restrict flow for system balancing.
- Prevent reverse flow (check valves).
- Automatically stop the flow in the event of a system failure.
When considering available valves for an industrial system, evaluation depends on both the short term and long term performance of a valve. And depending on the application, one valve may outperform another and provide a superior service life.
Types of Valves
Each engineer may have his or her own preference for a type of valve, but good engineering practices typically dictate which type is used based on the purpose of the valve. Regardless of the final decision, the choice is often based on several factors, including the:
- Type of service or medium (liquid, slurry, etc.).
- Expected frequency of operation.
- Size of the line.
- Cost of ownership (includes how often must maintenance is required for the seats and o-rings)
- Budget of project.
In any case, the main options for industrial piping systems:
Ball valve. The most common valve used for fluid flow, the ball valve, consists of a sphere with a hollow round hole in the center of the pipeline. When in the on position, the opening in the sphere is consistent with the line. In the off position, the ball turns 90 degrees and stops the flow.
Gate valve. Think of a gate valve (also known as a guillotine valve) like a medieval castle gate that moves straight up and down using a flat face, vertical disc or gate. The gate valve is a general service valve used primarily for on/off, non-throttling service and is most used where the frequency of use is low.
Check valve. Most industrial facilities install check valves as a result of the hazard review process, as it allows fluid to flow through it in only one direction. It remains open as flow continues forward, but closes if the flow halts or reverses. The moving component for a check valve may be a disc, stem, hinge pin, spring, ball or something else.
Butterfly valve. Unlike some other valves, butterfly valves can limit or regulate the flow without completely restricting it. In a butterfly valve, a disk rotates clockwise or counter-clockwise to permit or restrict the flow (similar to the ball valve). Depending on the desired flow rate or velocity, the disc can be stopped perpendicular to the flow, parallel to it, or somewhere in between. Two common variations include a wafer valve and a lug valve. In general, butterfly valves are less expensive and have a smaller footprint in the system, but create more pressure drop or flow restriction than other valve options listed.
Diaphragm valve. In this valve, a diaphragm lowers and raises to restrict or permit flow. These are excellent when the fluid being moved contains suspended solids. Additionally, these valves are more precise for controlling the flow volume than many alternatives, but tend to come at a higher price.
Other types of valves may be used for applications other than those listed above. Most materials work with a variety of valves, and plants use them differently depending on their own experience.
How to Evaluate Valves
Because a system relies on valves to control flow and often restrict it in times of need, valve selection is crucial. With dozens of types, materials, manufacturers and models to choose from, start by assessing each on the basis of simplicity, efficiency and safety.
Put simply, when a valve needs to open, it should easily open—or vice versa. While this single function may seem simple, it is not as straightforward in industrial plants.
Unfortunately, due to a number of factors—including corrosion, rust and moisture accumulation—valves can get stuck.
Whether the valve is automated or manual, it should work exactly as intended for years. Just like any other portion of the piping system, the expected service life of the valve is critical to the system’s performance. When a valve becomes inoperable, it causes costly downtime and repairs.
When considering various valve types and materials, choose the valve that will most consistently and seamlessly do its job, even if it were to remain unused for years.
Downtime can create tremendous costs for industrial plants—it was experienced by 82% of companies in the past three years and cost up to $260,000 an hour, according to analyst firm Aberdeen Research.
Valves are fundamental to efficiency on a small, continuous scale and, to a larger degree, help plants avoid downtime. A valve that does not move easily or on time, or one that is completely stuck, can cause:
- Harmful chemicals to mix inadvertently.
- Flow to continue towards a leak downstream.
- Fluid to reach temperatures above workable ranges.
- Injury to a plant operator trying to manually close it.
Another aspect of efficiency that valves impact is the system’s ongoing productivity. The point on the system with the lowest pressure or temperature rating becomes the limiting factor of the system. If a valve is incompatible with the line’s medium, or has a lower temperature or pressure rating than the rest of the system, the entire system can be compromised.
At installation it is easy to know what the system can handle, but wear on the valve—corrosion, erosion and more—can make it the system’s weakest link.
When considering various valve types and materials, choose the valve that will best maintain the temperature, pressure and compatibility of the system’s pipes and fittings over time.
Above all else, maintaining safety is a valve’s fundamental role. If one leaks or sticks, a number of issues can arise:
- If feeding a reaction, the reaction chemistry can be altered or continue longer than necessary.
- If a valve does not properly seal off a tank when disconnecting the pipe from the tank, a massive leak occurs.
- If an inadvertent flow reversal occurs, a check valve is the first line of defense.
- If a failure occurs downstream, a valve must engage to prevent further spillage and limit exposure to the chemical being conveyed.
- An inoperable valve may unintentionally allow two chemicals to mix, which can often become hazardous in an industrial plant.
In each case, depending on the pipes’ contents, a leak can create hazardous situations for workers in the form of an unsafe spill or airborne toxins. Additionally, inadvertent mixtures or chemical concentrations may create dangerous byproducts or accelerate wear on the pipe.
Learn About Industrial CPVC Piping
CPVC is an alternative pipe, fitting and valve material that has emerged as an advantageous choice in many industrial applications. When it comes to common chemicals such as hydrochloric acid, sulfuric acid, nitric acid, sodium hypochlorite, and many other chemicals, Corzan® piping systems have become the standard material of construction.
Learn more about the material itself, common use cases across industries and why many industrial professionals prefer it.