The Different Types of Gate Valves
Published April 10, 2023
The average cost of a gate valve replacement is between $300 and $600. That might not sound like much – particularly if you’re only replacing a handful of valves every six months. But there are hidden costs involved, too.
Read on for an in-depth understanding of the different types of gate valves and how you can save money.
What Is a Gate Valve?
Gate valves, “knife” valves, or sluice gates, are industrial components used for isolation. They do so by opening and closing the flow of a fluid and they have the appearance of a disc in the flow stream. Some specialist valves can block the flow of steam and gasses.
In piping, gate valves are a common type of valve used alongside others, including:
- Process valves
- Globe valves
- Check valves
- Plug valves
- Diverter valves
- Ball valves
- Butterfly valves
- Needle valves
- Pinch valves
- Pressure relief valves
- Bulk material valves
- Boiler blowdown valves
Typically, using a gate valve to limit – or throttle – the flow of a fluid is ill-advised. This is because it’s difficult to accurately gauge the flow with a partially open valve. Throttling fluid flow can also lead to erosion of the valve disc when used in this manner.
The Different Types of Gate Valves
Gate valves fall into different categories depending on who you ask. It’s easiest to split the valves into three categories:
- Stem movement
- Disc type
- Bonnet joint type
The stem can either be inside the valve or rise outside of it. These are referred to as “non-rising stem” and “rising stem” respectively. A rising stem has the advantage of visibility – you can see whether the gate is open or shut by looking at the stem’s position.
Non-rising stems are hidden from view inside the valve. However, they can be useful in situations where space is limited, which would cause a rising stem to collide with other machinery.
There are three types of discs used in gate valves: Flexible wedges, split wedges, and solid wedges. Like the stem, each disc has a specific use case.
Wedges allow the application of greater pressure, which is why the wedge shape is common.
Solid wedges are the most common. They’re simple and durable. Yet, they aren’t well-suited for thermal expansion, meaning solid wedges shouldn’t be employed in high-temperature use cases.
Flexible wedges are designed to counteract the disadvantages of a solid wedge. Cut around the edge to allow for thermal expansion, they’re often used for steam and cause trouble with fluids because those fluids tend to stick to the disc.
Finally, split wedges are comprised of two halves held together in the middle. Suited to a range of temperatures, liquids, and non-condensing gasses, split wedges tend to be more expensive. Some are loaded with internal springs to conform to the valve seating.
Bonnet Joint Type
Three factors affect the choice of bonnet joint – cost, pressure, and ease of maintenance.
Screwed bonnets are cheap, and used in simple applications. Bolted bonnets are popular, durable, and require a gasket seal. Welded bonnets are similarly durable and favored where disassembly isn’t needed.
Finally, pressure-seal bonnets handle high temperatures and pressures better than other designs.
Advantages of Gate Valves
Gate valves are best suited to situations where they need to be opened and closed infrequently. While it’s difficult to tell from a distance whether they’re open, they’re generally reliable and cheaper than ball valves. Gate valves offer multiple advantages:
- Little fluid resistance
- Many different applications
- Bidirectional flow control
- Effective when used with viscous fluids
Gate valves leave piping unobstructed, leading to minimal fluid resistance. And since a gate valve can control the flow of fluids from either direction, they’re versatile and have many different applications. They can function as shutoff valves, and are ideal for managing slurries and slow-moving fluids.
Heavy oils, molasses, and other viscous liquids are all examples of appropriate use cases.
Hidden Costs of Gate Valves
Harsh conditions and corrosive materials damage gate valves over time. The result is valves that fail, leak or get stuck in place. One of the biggest drawbacks to gate valves is when they fail.
The opening and closing process scratches the valve’s sealant over periods of extended use. While this wear and tear are at first subtle, it eventually impacts the functioning of the valve. Because gate valves are difficult to repair, they’re usually replaced when they become unreliable.
However, detecting a faulty gate valve can take time, causing damage to accumulate. The real problem is when the valve starts to fail. When this happens, the costs involved aren’t limited to the cost of a new valve.
Instead, those expenses trickle down and affect all aspects of production:
- Labor costs for replacement
- Costs from lost revenue due to non-functional machinery
- Damage to surrounding machinery if leaks go unnoticed
- Potential health and safety risks
- Damage to reputation owing to production delays
In other words, failed gate valves lead to unexpected and unpredictable expenses.
Alternatives To Gate Valves
Gate valves use simple engineering principles to work. That’s why they’re one of the oldest types of valves around. They’re popular and reliable – and in some cases, they’re out of date.
Process valves are self-cleaning and self-sealing. They work with an open-body design and rotating disc that clears out residue. Their key benefit is that they wear in over time (not out), generating better performance and tighter seals.
Process valves handle slurries and viscous fluids to the same standards as gate valves, but last for longer. They’re suited for hot line uses and are ideal for replacing ball valves to cut costs and improve efficiency.
Perfect for use cases where multiple gate valves control the flow direction of slurries and abrasive solids, diverter valves polish away scratches and form self-tightening seals using the same engineering as process valves.
The result is a valve that lasts far longer and reduces labor costs.
Extend Your Valve’s Lifespan
Knowing when to employ the different types of gate valves is vital to ensuring the longevity of your equipment. Newer, better-engineered valves cut costs, improve efficiency, and reduce downtime.
Our industrial valves are engineered for performance and they’re designed to replace pinch valves, knife gate valves, globe valves, and ball valves. They work harder and live for longer, reducing maintenance and repair costs. Click here to request a quote.