Tony, a knife valve is a gate valve. all a gate velave is, is a valve that a "gate" slides over the opening. the name Gate valve applies to several different types and is the name for a catagory of valves. the gate doesn't have to operate from the side, but can come from the top or bottom.
the main divisions of valves are gate, Ball, butterfly, and diaphram and most valve out there are one of these. there are a few that we use that don't fit into these groups which would be needle valves.
as for your original question, it is usaly a food grade silicon lubracant, but I would wipe it off and put it on your self so you know. and they adjust flow just fine. as for the metal in them.. hmm that might be a bit of a concern, if it is exposed and not stainless. what size are you looking for?
Steve
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Last edited by StirCrazy; 09-30-2010 at 02:39 PM.
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