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Ball Valve Types (floating, trunnion)

Ball valves – what are they?

In the petrochemical industry, ball valves are key devices that shut off and regulate fluid flow (oil, gas, steam, etc).

Ball valves: advantages and disadvantages

The following advantages are associated with this type of valve:

  • Opens and closes quickly by turning the handle a quarter turn
  • Ensure tight seals without high torques
  • It has a compact design (that is the main difference between a gate valve and a ball valve – which are both on/off valves)

Among the disadvantages are:

  • The valve does not have good regulating and throttling capabilities since it is designed for pipeline shut-off, not flow modulation (this is an ideal function for globe valves): throttling causes the partially exposed seat to erode due to the high-velocity flow and pressure on the valve. As the valve wears, it may leak progressively.
  • As a result of the accumulation of suspended particles and debris, the valve cannot use for slurries. In the cavities near the ball and seats, these particles may solidify. Gases and other liquid fluids are handled much better by ball valves (even challenging chemicals such as dry chlorine, hydrofluoric acid or hydrochloric acid, and oxygen).
  • It may be difficult to clean (except for the top entry design) If you look at the position of the lever, you can tell whether the valve is open, closed, or partially open:
  • The valve opens when the lever is aligned with the pipe; when it is perpendicular to the pipe, the valve is closed;
  • In any other position, the valve is partially open (or partly closed), modulating the flow.

1/4 turn valves belong to the family of “quarter-turn” valves (along with butterfly and plug valves) since the opening and closing operation is accomplis by turning a lever connect to the disc by 90 degrees.

API 6D, BS 5351 (forged), ASME B16.34 (pressure and temperature ratings), ASME B16.5/B16.47 (flanged ends) and ASME B16.25 (butt welded ends) are the main ball valve standards.

What is the process?

When it is fully align with the two ends of the valve, the ball inside the valve has a hole through which the fluid can freely pass. The valve is completely seal when the hole is perpendicular to the ends of the device.

Alternatively, when the hole is in any other position (perpendicular to the ends of the valve, for example), the flow is totally or partially interrupted.

Gate valve vs ball valve

This valve performs the same function as a gate valve (shut-off). A ball valve uses a sphere to open/close the flow, while a gate valve uses a disc seated on a seat. Thus, the main difference between these two valves is their design and compactness.

Globe valve vs ball valve

In general, these valves do not throttle the fluid flow as precisely as globe valves, since they have positive (at 0, 45, and 90 degrees) instead of incremental positions. Moreover, partial openings (or repeated open/close operations) would damage the valve in the long run (not an issue for globe valves).

Ball Valve
Ball Valve

Types of ball valves

Multiple criteria can use to classify ball valves:

  • Design: Trunnion mounted, double bleed, and double block
  • Types of ports: two ports are standard (1 inlet, 1 outlet), but three-way designs can also be ordered (1 inlet, 2 outlets, or vice versa).
  • Sizes: full bore, reduced bore, and V-notch
  • Ball body assembly: unibody (the ball body is made from a single piece of cast or forged steel), 2 pieces or 3 pieces (the body is made up of two or three parts).
  • Ball access: side entry or top entry (depending on whether the ball can be accessed, for maintenance, from the side of the valve or the top)
  • Seat material: metal or soft (Teflon)

A ball valve, floating

Floating valves suspend the ball in a flow of fluid and hold it in place by compressing two elastomeric seats against it.

Using a quarter-turn of the shaft (90 degrees), the ball can switch between an open and close position.

When the shaft moves, a load is apply to the ball, which is press against its seats.

The lightweight and economical design, which is suitable for bore sizes up to 10 inches, would not be able to withstand heavier and heavier balls, and the valve would not operate safely and efficiently above this bore size.

A floating valve can shut off a flow in either direction (like a trunnion valve).

Trunnion ball valve

Trunnion valves have been introducing to overcome the size limitations of standard floating valves. In fact, in this type of valve, the shaft, the ball, and the supporting trunnion all form a solid assembly capable of withstanding the high loads generated by balls of large dimensions.

A trunnion valve also has the advantage of having a lower operating torque than a floating valve (which can become an advantage when the valve needs to actuate since it can use smaller and more economical actuators).

The difference between the side and top entries

What is the difference between a side entry ball valve and a top entry ball valve?

It refers to how the ball of the valve and its internal parts can access. Either from the side (side entry) or the top (top entry).

We offer floating and trunnion-mounted ball valves with both side-entry and top-entry designs.

When frequent inline maintenance activities are expect on the valve, the top entry design is specified.

The reason for this is that top entry ball valves allow easier and faster access to the ball as well as the valve trim compared to side entry valves (which require more maintenance time and space for the same operations).

The main differences between these two types of ball valves are:

  • Ball valves with top entry generally have cast steel bodies; valves with side entry generally have forged (robust) steel bodies.
  • The top entry ball valves have a monolithic structure (are made of a single piece); the side entry valves are made of two or three pieces.
  • Because of the cast bodies of top entry ball valves, more non-destructive tests are need than for side entry valves.
  • Ball valves with side entry are easier to assemble and manufacture than those with top entry, which require long experience and craftsmanship to function properly.
  • Due to the casting operations required for manufacturing the body, top entry ball valves are generally more expensive and have longer lead times than side entry ones.

3-WAYS

A ball valve usually has two entries (or “two ways”).

Some applications, however, may require a 3-way ball valve. Instead of two ports (entries), a 3-way ball valve has three.

Multiport valves are need to divert fluid from the main valve inlet to two different directions (instead of just one), each serve by a different valve outlet. The main flow line of a 3-way ball valve can also serve by two separate and alternative inlets.

The ball of a three-way ball valve can be either L-shape or T-shape. Also, this special type of ball valve is available in floating or trunnion designs, with any type of valve end (flanged, socket, or threaded), and in many different materials, including plastics, carbon, alloy, and stainless steel.

Reduced port vs full port

In this context, the bore diameter of a valve is related to a piping system’s diameter. For more information:

The “Full port” (FB) type possesses a bore size (the hole of the ball) that matches that of the connected piping. Full port ball valves minimize the pressure drop created by reduced port valves, but they are bulkier, heavier, and more expensive. FB ball valves are better suit for throttling applications than RB ball valves.

A “Reduced port” ball valve (RB) has a bore size that is smaller than the bore size of the piping connected to it (for example, a tube). The flow of media through the valve is limit to a percentage (generally between 70 and 80 percent) of the total flow through the pipeline. The reduced port ball valves cause a pressure drop in the pipeline.

Aira Euro Automation is the best quality industrial ball valve manufacturer in UAE. They offer various industrial ball valves like V port ball valve,  pneumatic ball valve, manual ball valve, UPVC ball valve, lined ball valve, 3-way ball valve, 4-way ball valve, and many more.

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