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[verithingeoff]

Hi guys, looking for a bit of advice about a servo application. I want to turn a lever valve [steam] through 360 deg with a servo. Any ideas about how to?

[malcolmfrary]

Replace the lever with a gear.  Servo city do a range of gears to output from a servo for their robotics customers, it should be possible to gear up to 360°, get any fine adjustment using a servo stretcher.

[Ken G121]

Not sure it will work here but to to rotate guns I use a pulley system with a belt. If your servo has a 90 degree sweep put a large pulley on the servo and a smaller one on the item to be operated. If the large one is 3 times the diameter of the small one (ratio 3:1) then you get 3 x 90 degrees at the other end 4 times dis will give 4 x 90
Degrees = 360, as long as the drive belt does not slip this should work as long as the thing you are turning is low friction. I bond the large pulley directly to the servo arm ( the x shaped one works well) I have a hole in the centre of the pulley to give access to the servo arm screw

Regards. Ken

[verithingeoff]

Hi Guys, thanks for the replies I just checked with the valve supplier and although the valve rotates through about 400 degrees it delivers full pressure at 90, so the solution is much simpler

[derekwarner]

....ahah  ......I think Geoff really wanted say.......

"Hi Guys, thanks for the replies I just checked with the valve supplier and although the valve rotates through about 400 degrees it delivers full pressure at 90, so the solution is much simpler"

Well a 400 degree rotary motion valve certainly must be unique in construction with some form of helical design to add the extra 40 degrees without being back to .dot +40 degrees from where you started from

Is the valve hydraulically balanced internally?.......using steam to assist or overcome the movement of the valve against the boiler relief valve setting?

Derek

[verithingeoff]

Hi Derek
I just had another look at the valve and it actually rotates more than 400, more like 585 . I don't know how it works, I'll ask the supplier

[steamboat66]

most steam valves are needle type. with a fine point and thread, they may have several turns to fully open. with a short point and thread, they may have less than one turn.

[derekwarner]

I certainly am aware our boiler mounted steam isolation valves are usually needle valves with a conventional hand wheel, however we don't see too many which are servo operated apart from steam regulator valves which appear to be limited to -90 degrees movement and with internal physical stops

So hence my wonder of the design..............Derek

[verithingeoff]

Here's the valve on question http://www.clevedonsteam.co.uk/products.html#Lever Valve. 

[derekwarner]

Geoff....is this not the same boiler from another WEB site but with a different valve?........... Derek

[verithingeoff]

Well spotted Derek  
This is how it finished up