What are marine valves?
For most of our customers, this may seem like a silly question. We get it salty dogs, this article isn’t for you. However, with a wave of millennials entering the workforce, someone needs to cover the basics. Today, I’m going to break down valves Barney-style so that when you start reading about different types of valves you have a good foundation to start on. So now, back to the question, what is a valve?
A valve is a device that controls the flow of a gas or liquid. Some valves are simpler than others and are intended only to fully stop or allow flow; other valves are more complex and may be used to slow down flow as well. When a valve limits flow but does not stop it completely, it is referred to as Throttling the flow. If a valve is in a position that allows a full flow to pass through, it is referred to as open, and if it stops flow completely, it is referred to as closed.
In the marine industry, the substances most commonly dealt with are sea water, fuels, and waste. Before considering any valves for use in your project, you must know what substance will be passing through it, what the pressure of the substance will be, and if pressure will be consistent or pulsating. It’s also important to know where the valve will be in use. The reason you need to know these things is that valves are made of many different materials. Knowing what substance passes through a valve will help you determine how resistant to corrosion the material must be. Knowing where the valve will be used will help you determine how ductile (how much a metal can bend before it cracks) or dampening (how much vibration a metal can withstand and how much soundproofing it provides) your material needs to be.
Most valves have similar parts, but there are small differences that change a valve’s function. Every valve has an inlet (the place where a gas or fluid flows into the valve), and an outlet (The place where a gas or fluid flows out of the valve). Valves also have a component that is used to throttle or close the flow of gas or fluid through the valve. This piece is commonly called the disc even though it sometimes is more parabolic-shaped, plug-like, or wedge-shaped. The other stopping component that may be used instead of a disc is a ball. A ball can be attached or detached, meaning that it can be attached to a stem and operated manually similarly to a disc, or it can be free-floating and held in place by a spring or gravity. A free-floating ball is used because it can rotate when fluid or gasses pass over it, which creates a more even wear over time and lasts longer.
There are different ways to move a disc or ball in a valve, and these methods are important distinguishing elements for valves. The most common method is by the use of a stem. A stem is the long, thin, threaded component protruding from a valve that has a handle on the end. Turning the handle of a stem applies pressure to the disc or ball which pushes it against the flow of fluids or gasses and closes the valve.
A stem can be either rising or non-rising. This is as simple as it sounds. Rising stems will move away from the valve as it is opened, making it appear as though it is growing or, “Rising.” The advantage to this method is that you can easily see if the valve is open or closed by looking at it. If the stem is extended, it’s open. If not, it’s closed. Non-rising stems do not move away from the valve when rotated. Many valves with non-rising stems have an indicator on them to display whether or not it is open, but this is not true in all cases.
Sometimes you may see valves operated with a lever instead of a handle, and this is fairly common as well. Normal lever-operated valves use a quarter-turn, which means that moving the lever in a 90° rotation will either fully open or fully close the valve. A lever functions in the same way that a handle does, but with a smaller motion. Turning the lever presses a disc into the flow of fluid or gas, closing the valve and stopping the flow.
There are some valves that open and close without the manual efforts of a person. Some of these are operated by gravity. In this case, the disc hangs on a hinge and falls over the inlet. The place where the disc and the inlet touch is called the seat. This is common in check valves. Similarly, these gravity-operated discs or balls can be assisted by a spring that holds it in the closed position. If pressure is applied by a gas or fluid passing into the inlet, it will lift the disc and move through. This method helps avoid backflow, which is when a gas or fluid travels backward through the valve. The result of backflow can be ruptured pipes, spilled materials, and other costly damages. Some of these spring or gravity-operated valves are intended for fluids flowing in certain directions, such as vertical flow (flowing either up or down). This is because they also rely on backpressure to close, which is the pressure created by a gas or fluid flowing into a valve through the outlet.
The last feature we’ll highlight here is the connection of a valve. This is the part of the valve that marries it with a pipe or other fitting. The easiest way to determine the connection you need your valve to have is to check what fitting it will be attached to. For example, if you are going to attach your valve to a flange fitting, your valve needs to have a flanged connection. This is yet another very simple aspect of valves. The only thing you need to be careful about is making sure that the drilling pattern and material match up. Connecting unlike materials may lead to faster corrosion. Drilling pattern refers to the way that holes are lined up on a connection. If the holes on the valve connection do not match the holes on the fitting connection, bolts will not go through and they will not fasten. If you have any doubts about what it is that you need, or your definitions seem to be mixed up, connect with the Marine Valve Experts™ at Tork Systems, Inc. We’re happy to share our knowledge with you, and we love to answer questions for our customers!