If you've ever read our blog, you may know a thing or two about valves. We've posted an overview of butterfly valves, guides to cleaning and fixing ball valves, and even a semi-comprehensive list of the most common types of valves. Until now, however, we have not mentioned block valves. But the term "block valve" describes many of the valves we've talked about.
The strictest definition of "block valve" (or shutoff valve) refers to it as "any valve that has the capacity to block movement in one or more directions." Usually, however, people use the term when referencing a valve that can totally prevent or allow motion. This means that a block valve should A) be able to completely stop flow when closed and B) allow fluid motion to happen unrestricted when open. Flow is either completely allowed or completely denied when a block valve is in action.
In this post we will cover the most common types of valves that fall under the "block valve" umbrella. This could help you when choosing block valves for your next project!
Types of Block Valves
An important detail about block valves is that their name is not an official classification of a specific type of valve. Rather, it is a broad description of several types of valves that are designed to block flow.
Several valves immediately disqualify themselves from being block valves due to their design. Globe valves are a type of control valve that, because of their design, limit flow regardless of how far open they are. The same is true of butterfly valves, which have discs right in the middle of the pipeline. The following are a few types of valves that have block valve characteristics.
Ball Valves
Ball valves are probably the most common type of valve there is, especially in the PVC applications we tend to see.These valves are usually used to totally turn on/off flow in a system using a spherical seating with a hole in it. This hole allows liquid to flow through when the valve is in the "on" position.
Some ball valves are available in "full-bore" configurations, which means the hole in the ball is the same diameter as the pipeline. Full-bore ball valves are perfect examples of block valves, as they are not ideal for slowing down or limiting flow, but excel at completely stopping it and letting it pass uninterrupted. Ball check valves are not block valves, as they typically limit flow even when being pushed open by liquid.
Gate Valves
Gate valves are another fantastic example of the different variations of block valves. They have a flat vertical gate that stops liquid in its tracks. The design of the typical gate valve makes it much more effective as a shutoff valve than as a control valve. When gate valves are open, the gate is completely out of the way in a full-bore configuration. This means that when the valve is open, flow goes unrestricted. Just like a ball valve, a gate valve is a textbook definition of "block valve."
Pinch Valves
Pinch valves are quite different than the other two types of block valves we have discussed. That is because pinch valves can operate as stop valves or limiting valves. They have a tube inside that is squeezed closed or left open (either fully or partially). This is different because ball and gate valves do not work effectively when only partially open.
The full-port nature of pinch valves lets fluid flow through without slowing down as long as the valve is completely open. They can also close and completely stop liquid, depending on how high the pressure is. All these factors make pinch valves unique block valve examples.
As you can probably see, there are plenty of options when it comes to block valves. Under each of these categories, there are different materials, sizes, gaskets, end types, and more, so this just scratches the surface! Check out our Resource Center for more helpful guides like this one!
