Ball valves vs. gate values

[falcondob]

Anthony Caflo recommends gate valves over ball values. Other than the more precise control that gate valves provide, are there any issues. Price? Dependability? Anything?
Thanks,
John

[WolfReef]

Wasnt he talking about the output of a skimmer? I think most companies use gate valves on skimmer outputs.

[eric]

Is there a difference in friction loss?

[Thunderkat]

Gate valves are better for isolation of flow. A gate valve if used properly is for isolation only. Its either fully open or fully shut.

You should NEVER throttle with a gate valve. Also if you use a rising stem gate valve you can tell at a glace if it is fully open or fully shut.

Ball valves tend to wear out quickly (especially if used for throttling) and should be used for isolation only.

When used properly both valves should have about the same friction.

Gate valves tend to last longer with less leaks (when used properly) and ball vavles are better suited when speed of operation is more important.

If you want to throttle use globe valves. Needle valves are the best if precise throttling is what you need.

Edit: Also you can tell the position of a ball vavle by looking at the handle when compared to the pipe/tubing it is on. If the handle is perpendicular to the line it is shut, if it is in line with the piping/tubing it is open.