Valve selection 1

[breaker34]

Looking for ideas on a valve type. I have to install some valves on my city water intake. 6" steel lines. Its slightly filtered river water which can include debris, both small and medium size. I am thinking HP butterfly valve to get a good seal over knife gate. Any thoughts or experiences?
line pressure 80-100 psi, manual actuated
thanks,

 

[gerhardl]

You will have three choices:

1. Normal centric butterfly valve. Wafer, Lug or flanged.
Plus: price and mounting space. Acceptable to some sludge and debris.
Lifetime: 5- 25 years
Minus: Suspectible to debris.
Might be sticking if left longtime closed, might be untight if left longtime open and then closing.
Can not be used as 'end of line valves' if demounting and repair inhouse (if not built for it (threaded boltholes and allowed))
Note:anyway to be mounted with horizontal axis, evaluate hand gear instead of lever.

2. Soft lined gatevalve.
Plus: less suspectible for debris (flushed bottom), good for sludge.
Price (if not automated)
Lifetime: 10 - 30 years.
Minus: Mounting space.To be mounted with top up, not recommended for horizontal (will give skew load and longtime wetted top/spindle)
Might be heavy to operate if not tested and greased, say once a year.
Price: If automated or equipped with gear if this is not a standard option.


3. Double or trippel eccentric flanged butterfly valve with gear. (Variation: not flanged, see above)
Plus: Suitable for longtime tightness, even if let open for years.
Long lifetime without service.
(Slightly) better to debris and sludge than a normal centric BFL.
Can be used as end of line valves (local rules?)
Lifetime 25-50 years plus (depending on quality)
Minus: Price

Note 1: All three will be acceptable. At this size and pressure, and presumably not very cold water (under 10 deg C), the differencies will be less than at higher sizes, pressures and lower temperatures. Personally I would even then go for no.3 to minimize possible future trouble. Check price/lifetime. For all: go for well renowned valves with references rather than price. Lifetimes above are my personal estimations (Northern Europe) and might be higher or lower depending on quality and onditions.

Note 2: Marking/text on valve and pipeline. Full technical record in archive with adress to supplier/maker and service facilities.

 

[NGiLuzzu]

In general terms, I agree with gerhardl.

There’s only one thing I can't understand, I’m afraid: what’s the meaning of “Variation: not flanged, see above” at point 3?

Thanks,
‘NGL

 

[gerhardl]

Hello NGiLuzzu!

More clear if you simply cross out the sentence “Variation: not flanged, see above” at point 3"

Original my thought was that there are, after all, some (few) eccentric BFL valves on the market that are not flanged. In that case you will not have the pros' a flanged valve will have.

Apologies for a bit confusing sentence, and thank you for the note!!

 

[NGiLuzzu]

Hello gerhardl,
THANKS for the clarification!!

As a matter of fact, triple-offset valves are manufactured in double flanged, lug, wafer and also butt-weld end styles (and sometimes even butt-weld with top-entry or side-entry additional flanges as well, even if - in my humble opinion - that’s more to follow ball-valve-based Customer specifications or other marketing issues, than due to actual practical or technical reasons…!) ;-)

Regards,
‘NGL

 

[breaker34]

Thank you for the information. I am surprised to not see any recommendations for a gate valve. My thought was for a double offset BFV or a gate valve.
However, we are using a plug valve as there have been valves of this type in service that haven't had any problems.
thanks again,
breaker

 

[gerhardl]

Hello Breaker34!

Gatevalves:
If you see my main post, soft-lined gatevalves are included in point 2, in the european market mainly used for buried lines and in street constructions accessible through manholes both for drinking water and dominant for waste water. Depending on quality this is a good solution.

Plugvalves:
If this is a high-quality, soft lined,full opening double eccentric plugvalve, it is an excellent solution, probalby the best. Not included in my list, as this is a type not that ready available, highly priced and seldom used for this size in Europe.

Sorry! We all tend to forget there is somthing else beyond our own backyard!

 

[cvg]

a few missing details might help such as

[ul]
[li]above ground or below,[/li]
[li]how often and for what purpose will the valve be opened or closed,[/li]
[li]will it be used for throttling flow, and[/li]
[li]what does "slightly filtered" mean?[/li]
[/ul]