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Controlling the flow of liquid, gas and sometimes solids, valves have a deceptively simple job. Like an on/off (or dimmer) switch for tangibles, every valve is designed and built to guide the movement of a specific material.
Industrial valves are used in thousands of products and systems, from water infrastructure to offshore oil rigs. Since they have such a wide variety of applications, it naturally follows that valves come in thousands, if not millions, of shapes and sizes. They also run the gamut from simple to highly complex.
Despite high levels of variation, most industrial valves can be broken down into the same basic components: body (or enclosure), bonnet, actuator, valve member and seat.
Valve Body
The body, or enclosure, of the valve is often the largest component. Material flows through the body between the ports, and all other valve components connect to it. For example, a standard gate valve has three holes: the upstream port, where material flows into the body; the downstream port, where material leaves the body, and another hole on top to connect the bonnet and actuator. Of course, many valves have three or more ports as well, but the basic configuration is similar.
Depending on the type, size and complexity of the valve, valve bodies may be comprised of a single piece or be fabricated from several separate pieces. Modern casting processes that make use of cores allow the addition of complex inner cavities. These processes, including shell mold casting, investment casting and permanent mold casting, are often used for casting valves.
Valve Bonnet
The valve bonnet isn't necessary for every valve, but most standard industrial valves include this component. The bonnet attaches to the top of the valve body using either threads inside the valve body or bolts attached to flanges on both the body and the bonnet. The internal characteristics of the bonnet allow additional components to be attached, like the actuator and the valve member.
The bonnet often remains stationary while the valve is in use, but can be removed to service internal valve parts or to clear the body of obstructions. In some cases, the bonnet is combined with the body as a single part. Even if they are separate parts, the bonnet is often considered a characteristic of the overall enclosure. Without it, the material flowing through the valve would leak, and it would be impossible to actuate the valve.
Valve Actuator
Actuators are, in a way, the most important valve component. They provide the ability to control flow; without that ability, a valve is only a channel or a container. Actuators can be as simple as a hand wheel or a handle, or as complex as a computerized, automated valve controller.
In a traditional globe valve, the operator turns the hand wheel at the top of the valve, and the actuator moves a stem up and down along a threaded channel within the bonnet. As the stem moves up, it frees the valve member from the funnel-shaped seat and allows material to flow through the valve body.
Valve Member
The valve member is the component that directly prevents material from flowing through the body. Depending on the type of valve, the valve member can take on many shapes. Globe valves often utilize a disc-shaped valve member with tapered sides, or even a ball-shaped valve member that tightens against a funnel-shaped seat. Ball valves are so named because they use spherical valve members, cut so that they allow flow when the valve is open. Butterfly valves use disc-shaped valve members that rotate to allow or obstruct flow.
Valve Seat
The seat is a characteristic of the valve body that acts as a counterpart to the valve member. When a valve is sealed shut, the valve member and seat should be in full contact, and the connection should be tight enough so that no material can pass through. In a globe valve, the seat matches the sides of the tapered, disc-shaped valve member so that when the two components meet they form a seal. Similarly in butterfly valves, the seats are built into the valve bodies and allow a seal to form when the valve members are in full contact. In many cases, valve seats are coated with rubber or teflon to allow a tight seal to form.
Interchangeable Valve Trim: You'll often hear valve manufacturers using the phrase valve trim. This refers to the combination of the valve member and valve seat. Some modern valve manufacturers offer interchangeable trim: the same valve body can be used with trim of different sizes and shapes, offering greater flow control.
Learn more about control valve trim on the Kimray Blog.You'll often hear valve manufacturers using the phrase valve trim. This refers to the combination of the valve member and valve seat. Some modern valve manufacturers offer interchangeable trim: the same valve body can be used with trim of different sizes and shapes, offering greater flow control.
Manufacturing Industrial Valves
Since valves are made up of a number of different parts, they cannot be manufactured using a single process. Metal casting is the method of choice to produce most valve components, but they nearly always need to be machined before they are finished.
In order to provide the greatest strength and sealing ability, valve bodies can be cast as single parts by using both molds and cores. Shell molding, investment casting and greensand casting all make it relatively easy to produce hollow parts with complex inner cavities. Because of this property, these three processes are often used for casting valves.
After casting valve parts, the next step is to use CNC machining to finish the parts. Ports–where material enters and exits the valve body–can be threaded to allow the valve to attach to pipes on both sides. The interface between the valve body and the valve bonnet is also often threaded, allowing the two parts to be connected and separated for maintenance. Depending on the valve mechanism, actuators may be produced using more machining than casting. The threaded stem between the actuator and the valve member in gate valves can sometimes be machined entirely from bar stock. If valve members are not entirely machined, they almost always require some machining to ensure a precise fit. Similarly, while the basic shape of the seat can be included in the valve body casting, it must also be machined to ensure a snug fit with the valve member.
For more information on casting valves and machining valve components, check out our "Valve Types and Applications" post.
Ever wonder how industrial valves are made? The pipe system is not complete without valves. Since safety and service lifespan are the top concerns in a pipeline process, it is crucial for valve manufacturers to deliver high-quality valves.
What is the secret behind high functioning valves? What makes them better in performance? Is it the materials? Do the calibration machines matter that much? The truth is, all of these matters. Before even understanding the minute details of the industrial valve, one needs to know more about how valves are made.
This article will discuss the manufacturing of industrial valves from beginning to end. This would provide readers information about valve manufacturing and processing.
1. Order and Design
First, a customer should put an order, whether that is a customized valve or something found in the list of already-available valve designs. In the case of a customized one, the company shows a design to the customer. Once approved by the latter, the sales representative puts an order. The customer also provides a pre-defined deposit to the company.
2. Inventory
Once the placing of the orders and design commences, the manufacturing department will look for the raw materials for the stem, spool, body, and bonnet. If there are insufficient materials, the manufacturing department will procure these materials from suppliers.
3. Completing the Checklist
Once the materials are all present, the manufacturing team goes over the list again to ensure that everything is complete. It is also at this time that approval for the final draft of the design happens. Additionally, the quality assurance team checks the materials thoroughly. This is to ensure that the raw materials are of the best quality.
4. Production Process
This encompasses the majority of the activities pertaining to the manufacturing process of industrial valves. Each major components are made individually. Often, there is a checklist that entails all the names of the spare parts and what material to use for each.
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It is at this point that the team leader provides a timeline for the actual manufacturing, from the start of the operation to the completion date. Also, the leader often draws up a detailed operational plan.
Discussed below are the two common methods of how valves are manufactured.
#1: Cast Method
The cast method can be summed up by looking at the illustration below. Note that this is not the complete process.
● Body
An initial pre-shaped material cleaned. A turning process is done after cleaning. Turning is the method of removing excess material by cutting using a lathe or a turning machine. It involves attaching the pre-shaped body to a mount and to the turning machine. This machine rotates at a high speed. While it rotates, a single-point cutter cuts the body into the desired and specific shaped. Other than that, turning can also create grooves, holes, among others.
The next step is to add a plating metal, usually, copper to different sections of the body. Copper plating ensures complete and proper sealing of the body.
The next step is the polishing of the body. Then, technicians create the threads that allow attachment of certain valve parts to other components or the pipes. Valves need holes so holing also happens after this. Take note that each valve has different hole sizes, depending on the requirement. This is where regulations and standards come into play.
Technicians then paint the valves with Teflon or other types of elastomer. After painting, baking ensues. Teflon bonds with the body through baking.
● Seat
The seat undergoes the same process as the body. Since the seat is inside the body and as part of its valve function- for better sealing- it needs perfect fit to its attachment. Whereas the body only has Teflon, the seat as an additional rubber wrapping to ensure tight fitness.
● Stem
As in the case of the stem, it does not need to have much manufacturing. Rather, cutting these in the right dimensions is important.
#2: Forged Method
The forged method can be summarized in this process below. Similarly, the process below only highlights what the forged method is.
● Cutting and Forging
After the selection of the material, the next process is to cut them into the required lengths and widths. The next step is to forge each part by partially heating them to a certain degree.
● Trimming
The next step is trimming. This is where excess material or the burr is removed. Next, the body is flashed to mold it in the right valve shape.
● Sandblasting
Sandblasting is the next step. This makes the valve smooth and clean. The size of the sand used depends on customer requirement or standards. The valves are initially sorted out to remove the defective ones.
● Machining
Machining further enhances the sizes and shapes of threads, holes and the likes, again, depending on the design and requirements of the customer.
● Surface Treatment
The valve undergoes some treatment of the surface using certain acids and the likes.
5. Assembly
Assembly is the phase where technicians attach all the valve components to one another. Often times, the assembly is done by hand. It is at this point that technicians assign the valves production numbers as well as designation according to the regulations it follows such as DIN or API and the likes.
6. Pressure Test
In the pressure test phase, the valves have to undergo actual pressure testing for leakage. In some cases, air with 6-8 bar pressure fills the closed valve for a certain number of hours. It could range from 2 hours to a day, depending on the valve size.
If there is a leak after the timeframe, valve repair happens. Otherwise, the valve will move on to the next phase.
In other cases, leakage is detected through water pressure. If the valve does not leak as the volume of water increases, it passes the test. This means that the valve can withstand the increasing pressure. If there is some leakage, the valve returns to the warehouse. The technicians will check for leakages before performing another set of pressure tests to this batch of valves.
7. Inspection and Quality Control
At this point, QA personnel would inspect the valves thoroughly for leaks and other production errors.
Take a look at this video to see how a ball valve is manufactured.
In Summary
The industrial valve manufacturing process is a complex endeavor. It is not just a simple creation of the valve. Many factors contribute to its efficiency: raw material procurement, machining, heat treatment, welding, assembly. Valves should undergo rigorous tests to ensure proper functioning before manufacturers hand them over to the customer.
One might ask, what makes a high-quality valve? One of the determining factors for knowing high-quality valves is the test of time. Long service valves mean they are of good quality.
On the other hand, when the valve shows internal leakage, chances are, the manufacturing methods employed are not within the required standards. Typically, better valves can last up to 5 years while the low-quality ones can only last up to 3 years.
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