Number of turns in gear operated valves. 2

[Kudroli]

Hello:

Is there any industry guidence for the maximum number of turns (from fully open to close position) allowed in case of gear operated valves.

In one of my previous project, vendor had offered valves with 750 turns (of course it was 80" valve).

Advice on this issue is higghly appreciated.

Cheers.

Kudroli

 

[JimCasey]

No, usually the gear ratio is set by a limitiation of the rim pull force. 750 turns is greater than I have ever seen; tHe greatest trduction I have seen was on a 16" Noble Alloy Valve with 450 turns for 90 degree valve travel.

 

[gerhardl]

In addition to what Jim says: the necessary number of turns is then also of course influenced by the gear construction.

For larger valves a wormwheel construction, or wormwheel with linked arm, is often used to obtain the largest ratio of reduction with the least number of turns.

Have a look at the inner construction of the gear and check if the offered (supplied) type is the optimal gear construction for the valve.

 

[Kudroli]

Jim and Gerhardl

Thank you very much for the valuable knowledge shared.

Regards
kudroli

 

[BillBirch]

Companies like Shell generally specify actuators for all ball valves 16" and over simply to overcome the physical effort of "tags teams" having to turn a handwheel for an inordinate ammount of time, even if only one a year or so.

In a small independant oil company, we considered the frequency of operation and decided that large valves in what we called maintenance isolations applications (and operated less than once a year)could be maintained as manual gearbox driven, but the gearbox would be fitted with an input drive nut for operation with an air gun.

 

[JimCasey]

I'd hate to be watching a plant fire and knowing that all I have to do is to spin a handwheel sixteen jillion times before the flames get there.....