In what conditions do we need to fix a Butterfly Valve and in what conditions a Gate or a Sluice Valve?

Question

However a Gate Valve or a Sluice Valve is considered to be much safer as both allows Water to pass gradually as they are screwed up and also provide a full way, as for the Butterfly Valve would let the Water shoot through which could be harmful for the pipeline and it does not even provide a full flow passage to the Water as it has its Wafer type Shutter intact there in the way of the Water, in a vertical position, letting the Water flow from both the sides. But even then there is a large usage of the Butterfly Valves around the World.

Answer 1

1.The distinct feature of a gate valve is the sealing surfaces between the gate and seats are planar. The gate faces can form a wedge shape or they can be parallel. Gate valves are sometimes used for regulating flow, but many are not suited for that purpose, having been designed to be fully opened or closed. When fully open, the typical gate valve has no obstruction in the flow path, resulting in very low friction loss.
Gate valves normally have flanged ends which are drilled according to pipeline compatible flange dimensional standards. Cast Iron, Cast Carbon Steel, Gun Metal, Stainless Steel, Alloy Steels & Forged Steels are different materials in which Gate Valves are made available.
In short gate valves are used as a on-off switch.these valves cant be used in by-pass of control valve where throttling is reqired because throttling of gatevalves causes significant pressure losses and turbulence.
2.A butterfly valve is a type of flow control device, used to regulate a fluid flowing through a section of pipe. The valve is similar in operation to a ball valve. A flat circular plate is positioned in the center of the pipe. The plate has a rod through it connected to a handle on the outside of the valve. Rotating the handle turns the plate either parallel or perpendicular to the flow of water, shutting off the flow. It is a very robust and reliable design. However, unlike the ball valve, the plate does not rotate out of the flow of water, so that a pressure drop is induced in the flow.
Butterfly valves are widely used in water distribution and waste water processing (not recommended, as the debris may block the operation of the disc. Butterfly valves can come in two body types, affecting installation and maintenance: lugged or wafer. Wafer style valves are more common. They are typically installed between two flanges using bolts or studs and nuts. Lug style valves are also installed between two flanges but with a separate set of bolts for each flange. The lug style setup makes it possible to remove one side of the piping while the other remains intact.
3.A sluice is a water channel that is controlled at its head by a gate. A sluice gate is traditionally a wooden or metal plate which slides in grooves in the sides of the channel. Sluice gates are commonly used to control water levels and flow rates in rivers and canals.


Operation
Raising a sluice gate allows water to flow under it. (The term sluice gate refers to any gate that operates by allowing water to flow under it.) When a sluice gate is fully lowered, water sometimes spills over the top, in which case the gate operates as a weir.

Usually a mechanism drives the sluice gate up or down. This may be a simple, hand-operated, worm drive or rack and pinion drive, or it may be electrically or hydraulically powered.

The gates of a lock may work in a way similar to the way a sluice gate works, but traditional canal lock gates are hinged to swing like double doors.

Answer 2

Butterfly Valve Repair

Answer 3

The butterfly valve may be opened as gradually as a gate valve. that is why there is a locking handle that allows the valve to be cracked open..

Gate valves are not designed to be throttled, they are supposed to be either fully open or fully closed. Technically they are supposed to used to line up a system flow and/or isolate sections of pipe.

A butterfly valve may be throttled. I have seen many actuators installed on butterfly valves. Because the butterfly pivots about its center the flow impinging on it provides a balanced force. This minimizes the torque required to operate the butterfly.

Gate valves present an unbalanced surface as the flow strikes one side and presses the oppsite side against the disc. I have seen small 1inch equalization valves installed on bulhead isolation gate valves (8 in and larger) which are used to equalize steam pressure on both sides of the gate so they could be opened.

EDIT:
Valve replacement vs repair usually is a factor of size, for smaller valves its cost effective to replace instead of repair.
Larger gate valvels usually require lapping of the gate and if possible disc removal and machining

Butterfly valves have a replaceabe seal around the butterfly.

Replacing one type with another may be an issue as the gate valve requires a larger body width and distance between flanges.
The butterfly is in a wafer pack with a narrow width which is slipped inbetween two flanges.

replacing ontype with the other may require flange replacement or the inserting of a spool piece to make up for lost width.

Answer 4

I'm with Michael it is not a simple job and if you needed to ask where the valve is I don't think you should do it. When the system goes low and shuts down so of the oil will leak out with the Freon and if it isn't replaced you run the risk of ruining the compressor. And an overcharged system will put undue strain on the compressor which can have the same results.

Answer 5

I think it should be replaced when in no longer functions properly, or when it leaks. If you want a more un-intrusive valve use a ball valve.

L/D for a ball valve is 3
L/D for a gate valve is 8

Answer 6

butterfly valves are just more available and cheaper. Best to get the untreaded wafer style so that you can simply bolt it down.