Preference for Gate Valves vs. Butterfly Valves?

7/15/2020

Indicating valve (Butterfly vs Gate Valve) Requirement in Fire Water Mains:

NFPA 24, Section A.3.3.17.1 (Edition 2019), suggests to use OS&Y gate valves, butterfly valves, and underground gate valves with post indicators.

I understand that any type of valve are acceptable to use and I've seen frequent use of butterfly and gate valves in underground main. OS&Y requirement is quite clear.

Based on my understanding, butterfly valves are less prone to corrosion and ferritic buildup when compared to gate valves due to its body design.

My understand is that gate valves, due to buildup, might be prevented from closing and would require an entire systems or section of a system to do any maintenance. Yet, direct-buried gate valves are still preferred for underground mains and I'm not sure why.

The cost difference does is not enough in my case to use gate valves specially for 8", 10" 14" or higher sizes.

Is there some reason for gate valve preferences over butterfly valves?

If a butterfly is used I could possibly see a pit being required for maintenance, but NFPA standards do not address pit requirements for a butterfly valve.

Is there any other consideration would be helpful to consider when using butterfly vs gate valves, for underground or even aboveground applications?

Any suggestions would be much appreciated.

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9 Comments

Jonathan Sullivan

7/15/2020 10:07:15 am

Others can speak the the maintenance and installation points, but from a design perspective, butterfly valves have a higher pressure drop which may be undesirable because the disc is in the flow area in the open position.

7/15/2020 10:09:21 am

Should have proofed better. The higher pressure drop is because the disc is in the flow area in the open position. The higher pressure drop may be undesirable, not the disc location.

Casey Milhorn

7/15/2020 11:42:21 am

Cost is definitely less with a butterfly valve, especially when you consider the tamper switch. The tamper switch will be built in as part of the butterfly valve, the OS&Y valve will require a separate tamper switch. About $100 additional cost.
There is also the safety aspect in installation of the larger OS&Y valves, and also for replacement. In the past, OS&Ys were popular because people would try and maintenance them and replace individual parts and pieces. Now current trend is to just replace the entire valve.
In my opinion, butterfly valves are superior in just about every way. Cost, safety and ease of installation and replacement, etc...

Mr Glenn Scott Berger

7/15/2020 12:02:27 pm

When I first started in this business I was taught that butterfly valves were more prone to failure based upon the pressure being maintained in the system. This may not be case anymore.

Ron Morales

7/15/2020 12:41:46 pm

Hope this helps.

https://www.huameimachinery.com/gate-valve-vs-butterfly-valve/

Dan Hartel

7/15/2020 07:38:44 pm

I like OS&Ys especially the new Tyco ones that are Ductile Iron (lighter) and they have rubber O-Rings instead of graphite packing. They may take a little longer to install, but the larger hand-wheel makes using 2 hands to operate a little easier on the hands & wrists. We do use a lot of butterfly valves though.

For Fire Pump Test Headers, we only use OS&Y's because I believe they throttle the flows better.

Pete D

7/15/2020 08:19:44 pm

I have not seen buttefly valves listed for underground installation. Even if they were, it's not advisable to install them there. Butterfly valves operate on a worm gear. More moving parts = more to fail. Don't bury wimpy valves and cover them in concrete. The benefit of butterfly valves is the take-out and operating space for space constraints, as well as cost.. Think of a pump that has 8 control valves. If they were all OS&Y, you coukd never open them because the screws would hit each other. OS&Y valves must be used on pump suction per NFPA 20. They're more robust and less prone to trapping debris such as rocks. Buttefly valves are more commonly used for isolating valves, for maintenance on the pump bypass check valve for example, and as a system control valve.

7/16/2020 02:11:31 pm

While I appreciate everyone views, However, Butterfly valves are very common in underground mains with Indicator post. The only difference is it might need to be install in the PIT for maintenances. Now a day (specially in hydrocarbon industry) use of non-metallic pipes are very common for underground service due to ultraviolet effect in solar radiation, so all these valves need to be installed underground mains without jeopardizing UL listing or FM approval need.

Victoria Addington link

5/12/2022 10:30:54 pm

You made a good point when you discussed that butterfly valves are effective at resisting corrosion and ferritic buildup. My friend told me that their piping project needs valves. I should advise him to look for a supplier that offers a wide selection of pipe valves.

Preference for Gate Valves vs. Butterfly Valves?

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