Drill Stem Distance

[Reinhardt Burger]

Can anyone tell me how what other methodes there are to detemine drillstem insertion. We currently have magnet limits top-stop, drill-bit insertion and bottom-stop. Due to bent drillstems the magnets and/or limits gets broken off. I would like to know what other methods there are to do this if any.
Thanx

[Neelabh Sharma]

Usually there are Top & Bottom proximity sensors coupled with 2 nos. of ‘Drum in’ sensors…typical of Flowserve…….
Some also include a variation in which there is a drum washing limit sensor also incorporated which is higher thatn the ‘Drum-In’ signal
Position of the drill stem is determined by the rpm of the Wire-rope hoist drum having measured grooves whereby rpm is converted to distance covered and therby the drill stem position…
Bent drill stems are one-off problems…this should not ideally be the basis to change your system…look out for the reasons of Bent drill stems…get drill stems replaced
I hope i have answered your query….if not please elaborate some more…

[Ken Osment]

Your safety limits are typically physically mounted on the structure and some of the newer systems are also double redundant. As for where you are with the drum, a proximity counter or encoder mounted to either the crown sheave or idler sheave are quite accurate, these locations are not that good for the absolute safety limits as cable growth and or miscounts can effect the position. As an indicator they work fine. Eight of my cokers have encoders mounted on the winch drums. There is some error with this method as the payout rate differs with the number of wraps on the winch drum.

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