Submerged suction pipe position measurement

[Murec]

I am working on a floating suction system in a large tank.
Three articulated suction arms, made of 24" pipe, will be suspended from floats so the intakes are about 1m below the surface. The problem is to monitor the position of the suction pipes. The pipes should rise and lower with the liquid level in the tank, but they can also get stuck high or sink to the bottom.
One solution is to attach cables to the pipes and check the length of the cables. This requires pulleys, tesioning springs and other hardware.
Another solution, with (almost) no moving parts is a guided wave radar, with the cable threaded through a target disc attached to the pipe (one instrument for each pipe). Here the problem is to detect the disc itself and not the surface of the liquid.
Does anyone have any experience in similar applications?

Thank you

 

[DC1000]

How far will the pipe move vertically? If the pipe sinks to the bottom, will it be totally submerged with the tank full?

 

[Murec]

The max range of vertical movement is about 45 feet, however the normal variation in the pipe elevation is around 10 feet.
The pipe is supported by floats at about 3 feet below surface, the other end is close to the tank bottom, so the pipe is completely submerged all the time.
And the liquid in the tank is an oil product.

 

[itsmoked]

I would suggest connecting some rod/s to the bottom so the inlet can never get stuck on the bottom. Then if 'stuck up' is really a problem can you run two cables up from the inlet to either side and just keep track of their length with some OTShelf spool counter? That way if the pipe is up over on one side you can tell.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com