When to use a trunnion mounted ball valve?

Author: Geoff

Apr. 29, 2024

Applications of Trunnion Mounted Ball Valves

By Carson Hu

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24 Oct, 2019

Right now, there are over 3,000 facilities on the Outer Continental Shelf involved in the collection and treatment of oil and gas. These oils and gases are collected from wells -- a process that's performed using certain types of high pressure valves. Of course, different types of American ball valves offer different results and it's crucial that the right projects are executed with the right types of valves. Quite often, the types of valves being used are ball valves, sometimes referred to as pig ball valves or pig vales (as they are used in conjunction with pipeline pigging systems). Before sourcing and investing in valves, it is important to understand the degree to which these valves may differ from one another. Let's delve into some of the defining characteristics of ball valve types. Ball Valve Body Styles Before getting into the exact types of ball valves that are available at the moment, it's important to remember that there are actually four separate types of body styles. These include the single body, split body, top entry, and welded styles. The styles of ball valves available differ from the types of ball valves available. This means that there are number of potential variations that you can see in ball valves. The great thing about this variety is that it means that there is more potential applicability in ball valves than there would be otherwise. Full Port Ball Valves: Turning to the different body types of ball valves, we can first look at the full port ball valve. A full port ball valve is defined by the fact that it has an oversized ball. The oversized ball has a purpose -- it is the same size as the pipeline. This means that there will be less potential friction less than there would be if the ball wasn't the same size as the pipeline, and the flow involved is unrestricted. The valve is larger as well. Standard Port Valves: As their name suggests, standard port valve are quite usual. This means they're less expensive than some alternatives. This type of valve has a smaller ball, and therefore the valve itself is smaller as well. The flow going through the pipe will in turn be smaller and will typically be about one pipe size smaller than the valve's pipe size. This makes it more restricted. The V Port Ball Valve: The V port ball valve is named after its V-shaped seat. What this means is that the orifice through which the product flows can be more easily opened and closed to change its direction. While many like this idea, the construction of this type of valve means that it can't be used just anywhere. It typically needs to be utilized in a more secure site. When the valve is opened, it is usually opened at the "small end" first, which helps stabilize the flow control. Trunnion Ball Valve: Then there is the trunnion ball valve, which doesn't exactly give much away through its name. This type of valve will actually anchor the valve at the top and the bottom through a particular mechanism. This would be applied on larger and more high pressure valves. While this type of valve isn't going to fit everyone's needs, it can definitely be used for particularly high pressure projects. Manually Operated Valves: Finally, these types of valves can be closed more quickly than their counterparts. Though this is an advantage in some cases, it also means that there can be a risk of a water hammer. These can include an actuator, which can be pneumatically or motor operated, which will in turn be used for on/off flow control. The valve will also have a positioner, which transforms the control signal into an actuator position. The flexibility of this type of valve is certainly an advantage to most projects. Now that you're more familiar with the styles and types of ball valves, you'll be in a better position to make decisions that will support your needs. For more information, please contact us today.

The floating ball valve vs the trunnion mounted ball valve

‘’Floating ball’’ and ‘’trunnion ball’’ are concepts which are used generally. But what are the exact difference between these two designs and when to use which one?

The most important difference between these two design is the construction of the ball and the way in which it is assembled inside the valve body. A trunnion ball is attached and centred inside the valve body through both a top shaft -the valve stem- and a bottom shaft – the trunnion. A floating ball is attached to the valve body only through the valve stem. As a result, the floating ball ‘’floats’’ in the valve seats.

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Further reading:
Bellows Seal Valve

In a floating ball design the ball is pushed against the downstream seat by the in-line pressure, resulting in tightness. When operated from closed to open position, the ball is to be rotated against both the in-line pressure (∆p) and the friction of the seats. In other words: the torque needed to operate the valve is created by both in-line pressure and the nature of the valve seats. The amount of torque required increases significantly when operating pressure (∆p) and/or valve size increase, and/or whenever the nature of the seat is made more robust. The latter applies in case of a metal seated valve design.

Floating ballTrunnion ball

In a trunnion design, the ball is inserted in a central bottom shaft which is called the trunnion. The ball is fixed between the stem and the trunnion, which inclines that the ball is not floating but fixed and centred. The inline pressure presses the seats against the ball, causing the tightness. This inclines that during operation, the ball does not have to be rotated against the in-line pressure (∆p) and the valve seats, but that is solely needs to be rotated against the pressure of the seats.

Floating ball & trunnion ball

As a result, the required torque of a trunnion mounted ball valve is generally lower than the torque required of a comparable floating ball valve. For example: a DN200 metal-seated floating ball valve would require a significantly larger actuator than a DN200 comparable trunnion valve, leading to significantly lower costs of the overall package. Also, in general the trunnion seat design offers higher stability which makes it more suitable for extreme conditions and especially varying pressure levels.

So, the trunnion-mounted ball valve is more suitable for high pressure applications and bigger dimensions compared to the floating ball. Another advantage of the trunnion design vis-à-vis the floating design is the fact that a trunnion generally is included with a drain or bleed connection, making it suitable to function as a dual safe device. Furthermore, it functions as an relief valve automatically whenever the pressure in the central cavity is higher than the spring force of the seats. When this happens, the seat springs relieve automatically in order to drain the excess pressure back into the main line. Because of these reasons, the trunnion is commonly used in offshore- & oil & gas applications, where extreme conditions pose the standard.

Off course, a large disadvantage of the trunnion compared to the floating design is associated with its costs; which are significantly bigger. Because of these costs, trunnions are used solely when they have to be used.

Our specialist happily assist you in advising the right ball valve design for your application.

Contact us to discuss your requirements of Pneumatic Forged Trunnion Mounted Ball Valve. Our experienced sales team can help you identify the options that best suit your needs.

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