Pourquoi utiliser un robinet-vanne plutôt qu'un robinet à boisseau sphérique ?

When installing valves for liquid or gas systems, most people default to robinets à boisseau sphérique. And there’s a good reason for that — ball valves are versatile, durable, and provide reliable shut-off.

But ball valves aren’t always the best choice. In some applications, old reliable Vannes are a smarter pick.

What Exactly is a Gate Valve?

Before we get into reasons for choosing gate valves, let’s quickly cover what they are and how they work.

Gate valves consist of a valve body that the gate slides into. When fully lowered, the gate seals against seats within the valve body to stop flow. To open the valve, you use the valve stem to raise the gate and allow fluid to pass through.

Gate valves derive their name from the gate-like sliding action of the wedge. And while ball valves operate with a simple 90 degree turn, opening/closing a gate valve requires rotating the stem several turns.

5 Key Advantages of Gate Valves

Now that you know the basics of gate valves, let’s look at five areas where they beat out ball valves.

1. Regulation of Flow

One of the biggest advantages of gate valves over ball valves comes down to flow regulation.

Ball valves really only function fully open or fully closed. But gate valves allow precise regulation of flow rate by adjusting stem position. This gives you exact control over liquid or gas velocity through the valve.

For applications where you need to choke flow rather than stop it completely, gate valves are the only choice. Think process piping systems that require accurate flow control.

2. Full Bore Design

Gate valves suit high flow rate systems because their opening matches pipe diameter when fully open. This full bore design eliminates flow restrictions or pressure drops associated with reduced openings.

So if your piping needs to handle large fluid volumes, gate valves are less likely to impede flow. Ball valves might require a significantly oversized valve — increasing costs — to match the uninhibited flow from an equally sized gate valve.

3. Ability to Throttles Viscous Fluids

Throttling flow refers to partially closing a valve to restrict — but not completely stop — flow. It’s an invaluable tool for managing the conveyance of viscous substances like wastewater sludge.

Gate valves throttle these heavy fluids much better than ball valves. Ball valves would allow minimal passage of the media before sealing it off completely. Gate valves give you broader control over allowance and avoidance of clogs.

4. Resistance to Effects of Cavitation

Cavitation refers to vapor bubbles forming in areas of low pressure that collapse when reaching higher pressure. It can severely damage valves and piping.

Gate valves better withstand the damaging effects of cavitation than ball valves. At high-flow velocities, the torturous path through a ball valve makes them more prone to separating fluid and cavitating.

5. Lower Initial Cost

For valves of equivalent size, gate valves also win out when it comes to upfront expenses. But cost analysis should consider total lifecycle value rather than just initial pricing.

And gate valves often require more routine maintenance to keep them functioning properly. So taking the long view, operational costs could balance out or even favor ball valves.

Still, if budget limitations drive the decision-making process, gate valves provide welcome relief. You can always replace them with more sophisticated ball valves down the road.

Inconvénients des vannes à vanne

I’ve focused primarily on why gate valves beat ball valves for certain functions. But ball valves also claim some advantages that are worth noting.

Limited Pressure Ratings

Ball valves typically support substantially higher pressure applications than gate valves of the same materials and dimensions. So if your system design pressure exceeds gate valve limits, ball valves become the better alternative.

Lack of Backup Sealing Method

Most ball valves utilize both metal-to-metal seals and elastomer seals. The elastomer seals protect the metal components should the upstream seat fail. Gate valves don’t provide this kind of backup protection.

No Visual Position Indication

With ball valves you can tell at glance whether the valve is open or closed. Gate valves offer no such visual verification because the gate resides inside the valve body. You verify gate valve status through feel of the handwheel or stem nut.

Why Might Someone Choose a Gate Valve Today?

Ball valves shine when you need to start and stop flow quickly. That’s why you find them throughout residential, commercial, and industrial facilities. Gate valves live on mostly in niche roles centered around flow regulation.

Take irrigation systems for example. Farmers use gate valves at pipeline ends to manage dispersal rates to fields. They also throttle flow to prevent overwhelming discharge at any one emission point.

For handling something like pressurized chlorine gas, plants choose gate valves over ball valves. Plant engineers can precisely calibrate chlorine injection rates to balance with downstream water flow volumes.

Really, anytime automatic control over flow rates takes priority over quick cut-off convenience, gate valves get the nod. Their ability to finely adjust passage through variation of slide gate position makes them perfect for flow regulation roles.

Pourquoi utiliser un robinet-vanne plutôt qu'un robinet à boisseau sphérique ?

When precision control trumps convenience, gate valves regulate flow better than quick-closing ball valves. Though ball valves excel at reliably stopping liquid and gas flow on a dime, gate valves handle throttling jobs that require more nuanced flow manipulation.

Their declining use doesn’t diminish gate valves’ capabilities for certain functions. You’ll continue to find them whenever exact flow control matters most.