How to Choose the Right Gate Valve: Technical Specs for the Right Choice

Choosing the right gate valve goes beyond a simple catalog browse-and-pick. It demands an in-depth understanding of the technical factors that can drive your project toward success or failure. If the myriad of options is overwhelming, you can always seek guidance from AlterValve, the leading gate valve supplier.

This article aims to guide you, focusing mainly on gate valves' technical specifications, their operational efficiency, and cost-effectiveness. We will analyse the design of the wedge and the quality of natural rubber used in gate valves and how these factors influence your choice. So, prepare yourself to make an informed decision through this detailed examination.

Understanding Gate Valves: A Technical Overview

Exploring the world of gate valves offers insights into their functionality and efficiency. It also provides information about their cost-effectiveness, a critical factor in choosing the right gate valve for specific applications. Let's proceed.

Functionality and Efficiency of Gate Valves

Gate valves, often known as water gate valves or sluice valves, emerge as a top pick for linear valves in pipelines. Their unique design lets you control the liquid flow and isolate a section of the pipe when needed. The gate valve, fitted in-line on a pipe, operates through a handwheel actuator that opens and shuts the valve.

Let's look at the main characteristics of gate valves:

• They can halt the water flow entirely, which proves useful for troubleshooting, maintenance, and pipe-cleaning tasks.
• They are bidirectional and can stop flow in both directions without a significant decrease in pressure.
• They are not built for fast opening or closing.
• They are unsuitable for partial opening or shutting to control flow.

Now, let's see where gate valves are typically used. They find application in various industrial environments, including oil and gas extraction sites, processing plants, and water treatment facilities. A fully open gate valve does not obstruct the flow path, resulting in a very low-pressure loss. This feature facilitates the use of a pipe-cleaning pig. Gate valves accommodate all types of fluids, including water and gas, and manage gases from -20 to 60 degrees Celsius at a maximum speed of 20 m/s. Depending on size, the valve operates within a torque range of 5 Nm and 30 Nm. Be wary of valves that operate with less than 5 Nm of torque as you might shut the valve too quickly, leading to water hammer and pressure surges in the pipeline.

When choosing the right gate valve, consider the fluid type, the required operating torque, and the temperature and flow velocity ranges. The diverse applications of gate valves and the industries that utilise them might affect your choice of gate valve. Now that we understand the technical aspects and applications of gate valves let's discuss an important factor – their cost-effectiveness.

Cost-effectiveness of Gate Valves

Understanding the choice of materials for gate valves holds the key to their cost-effectiveness. For example, gate valves made from GJS400-15 ductile iron offer enhanced durability. This increased durability reduces the chance of cracking and extends their lifespan. Although these valves carry a bit more weight due to a thicker wall, the extra weight balances out a slightly lower tensile strength.

Stainless steel proves to be the most resilient material for bolts, ensuring your gate valve endures longer. Knowing how to choose the right gate valve becomes critical, and material selection significantly influences this decision. Choosing an unsuitable valve type can result in high replacement costs and significant loss of time.

The cost consideration is not just about the initial price but also potential savings in replacement costs and time. Therefore, choosing materials carefully can greatly improve gate valves' cost-effectiveness. Now that we understand the cost-effectiveness of gate valves let's look at the importance of the gate valve wedge design.

Gate Valve Wedge Design: A Key Consideration

Choosing the right gate valve involves understanding the importance of wedge design. It's not just about identifying the range of designs available but also determining the one that fits your specific needs. Let's examine these aspects in more detail.

Types of Gate Valve Wedge Designs

The gate valve wedge design directly impacts the efficiency of the valve and determines its suitability for specific applications. Here are the main types:

• Solid Wedge Gate Valve: This design, known for its simplicity and strength, is most fitting for clean fluids.
• Flexible Wedge Gate Valve: Ideal for handling fluids with suspended solids or thermal expansion, this design can adjust to deformations or misalignments in the valve seats.
• Split Wedge or Parallel Disks Gate Valve: This design includes two discs that a spring forces apart against parallel seats at closure. The knife gate valve, a common variant of this type, achieves the necessary shut-off by placing a flat gate between two parallel seats.
• OS & Y Gate Valve or Rising Stem: This design includes a stem that rises above the handwheel as the valve opens and descends when the valve closes.
• Non-rising Stem Gate Valve or Insider Screw Valve: This design features a stem that threads into the gate at the lower end. When you rotate the handwheel on the stem, the gate moves up or down the stem on the threads, keeping the stem vertically stationary.

The wedge guiding system should incorporate low-friction, plastic-covered nose pieces with a groove in the body. This design ensures the valve is not difficult to operate or leak when the rubber gets damaged. For a more in-depth exploration of gate valve types, we encourage you to explore our comprehensive article titled "Types of Gate Valve."

We will discuss choosing the most suitable design for your needs.

Choosing the Right Wedge Design

When choosing the right gate valve for your system, consider several factors. These include pressure drop, shutoff requirements, and operating temperature/pressure. The wedge design is also essential, directly influencing the valve's performance.

Gate valves come in four main wedge designs:

• Solid Wedge Gate Valve: This is a straightforward and sturdy design, best for clean fluids.
• Flexible Wedge Gate Valve: This design can adapt to deformations or misalignments in the valve seats, making it perfect for fluids with suspended solids or thermal expansion.
• Split Wedge or Parallel Disks Gate Valve: This design features two discs that a spring forces apart against parallel seats at closure. A well-known type is the knife gate valve, which has a flat gate between two parallel seats.
• Wedge-shaped Gate Valves: These valves use two inclined seats and a slightly mismatched inclined gate for a tight shut-off. The split wedge design has inherent disc flexibility, which makes sealing easier and reduces stickiness between sealing surfaces when the valve seats are angularly misaligned.

Another critical aspect of wedge design is how the wedge nut attaches to the wedge. Is it a form-fit or a press-fit? Most people prefer form-fit wedges as they offer better flexibility and can usually absorb water hammers due to their freedom of play. However, this movement can irritate the rubber where the nut rests. A press-fit wedge nut can pass the force of water hammers to the spindle and the bearing, potentially bending the spindle.

The wedge nut connects the wedge to the stem. There are two basic designs: a loose design where the brass nut slides in a slot in the wedge core and a fixed design where the nut expands in the wedge core. These are suitable for moderate pressure-temperature applications to prevent the wedges from getting stuck due to metal expansion. A fixed wedge nut design is recommended as it reduces the number of movable parts, thus eliminating the risk of corrosion.

Now that you understand the importance of selecting the right wedge design let's consider another crucial aspect - the quality of rubber used in gate valves.

Also read: Exploring the Diverse Applications of Gate Valves

Quality of Rubber in Gate Valves: What to Look For

This section highlights the different types of rubber used and how they affect the valve's performance. Even more critical, you'll understand how to assess the quality of rubber in gate valves, a key factor in making a knowledgeable decision. Let's delve deeper into this topic.

Types of Rubber Used in Gate Valves

The choice of material, especially the type of rubber, directly affects the efficiency and functionality of gate valves. These valves, widely used in various industrial applications, often have seats made from resilient materials like rubber, brass, or stainless steel. The compatibility of these materials with the regulated fluid determines their selection.

Here are some important points about rubber-seated gate valves:

• The rubber in these valves can absorb and expel impurities during the valve's closure and regain its original form upon reopening.
• The zero-offset butterfly valve clearly displays this feature.
• The low-pressure rating of this valve, owing to the dependence on rubber's flexibility, emphasises the crucial role the type of rubber plays in the performance of gate valves, especially in resisting pressure.

When you are deciding on the right gate valve, it's important to keep in mind the specific requirements of your application. For example, if your application involves drinking water, you must ensure that the rubber parts that come into contact with the water have approval for drinking water use. The rubber components should have major approvals like DVGW/KTW, KIWA, or NF if local approvals are unavailable.

Knowing about the type of rubber used in gate valves and its effect on their performance can guide you in making a wise decision when choosing the right gate valve.

After discussing the types of rubber used in gate valves, it becomes crucial to understand how to assess their quality.

Assessing Rubber Quality in Gate Valves

The rubber quality in gate valves significantly affects their performance and lifespan. Confirm the type of rubber used in the gate valve first. It must meet the specific application requirements, such as the fluid type, operating temperature, and pressure conditions.

To evaluate the rubber quality further, you can:

• Inspect physically: The rubber should have no defects like cracks or blisters. It should show flexibility and resilience.
• Test performance: The rubber is of high quality if the operation runs smoothly without leakage.

Then, check the wedge's sealing behaviour. Apply chalk over the entire sealing area and operate the valve. If the chalk shows narrow lines, the valve might not reliably stop water flow long-term or might need high actuation torques, which could stress the surrounding components.

Another vital factor is the rubber’s compression set, or its ability to return to its original shape after compression. The EN 681-1 standard specifies the minimum requirements for the compression set value. However, the better the compression set, the more effectively the rubber returns to its shape. This ensures a tight closure year after year. The rubber should also withstand continuous impact from impurities and chemicals and absorb small impurities in the seat for a tight closure.

Now that we understand the importance of rubber quality in gate valves, we can compare gate valves with other valve types in terms of functionality, efficiency, and cost.

Comparing Gate Valves with Other Valve Types

Gate valves are renowned for their design, which involves linear motion. They employ a flat closure element that slides into the flow stream to provide shut-off. These valves successfully manage slurries and viscous liquids such as heavy oils, light grease, varnish, molasses, honey, and cream. However, they may not be optimal for low-pressure applications or scenarios that demand cleanliness or sanitary conditions.

In contrast, butterfly valves are quarter-turn valves. They utilise a metal disc mounted on a rotated rod to regulate fluid flow. These valves are versatile and can be employed in various applications, from general services to extreme conditions.

Gate valves are highly compatible with a variety of fluid types. They effectively work with water, steam, gases, and corrosive chemicals. This feature, along with their capacity to manage thick or viscous liquids, makes them a preferred choice in industries such as power plants, chemical processing, and wastewater treatment.

Before the resilient seated gate valve existed, gate valves with a metal seated wedge were preferred. These older designs needed a depression in the valve bottom to secure a tight closure.

• Key benefits of gate valves:
• They provide an unobstructed flow path, resulting in a very low-pressure loss.
• They are multi-turn valves, meaning you rotate the valve multiple times to open or close it, which helps to avoid water hammer effects.

Whether you require an electric or pneumatic actuator gate valve, a range of gate valve suppliers can cater to your needs. For larger gate valves, it's crucial to ensure that the valve can be actuated easily by the handwheel without a bypass, even at a pressure of 16 bar.

Making the Right Choice: The Power of Technical Specs

Throughout this exploration, you've understood the essential role technical specifications play in guiding you to the perfect gate valve. You've learned how the functionality, efficiency, and cost-effectiveness of gate valves are highlighted, focusing on the crucial role of wedge design and the quality of natural rubber. Remember, making an informed choice can lead to significant cost savings and improve efficiency. ‘

If you need more insights, experts from AlterValve are ready to help. We are one of India’s leading valve suppliers. Connect with our team for technical advice.

As the old saying goes, "The devil is in the details". Therefore, careful attention to detail is crucial when making wise choices.