Pekka:
A little more information would be nice, if it's possible to share it. I understand about confidentiality agreements - been there done that.
In priciple, nothing too secret about it, but customer confidentiality is very high on my list.
Think of paper /cardboard or glasfibre processing, slitting, winding, cutting, sheeting etc.
You refer to a web processing machine. What's the problem, web not tracking properly? Or is the web not being processed properly through the rolls?
There are host of problems on high speed if the material web does not track properly. e.g. the web is slit and sheets are separated (this is intentional) and then material web does moves sideways over the guide rolls and end up incorrect location on cross machine direction. This side shift migh be only 1-2 mm at 5 meter distance (machine direction), but it will create problems.
The problem migh be because material web profile is not straight, surface structure problems or guide rolls (or other rolls) are not correctly aligned.
What are they trying to measure, roll diameter or alignment between rolls? A 10-15m tape would give you a roughly 3-5m roll which is a helluva roll under most conditions. Then again a 10-15m tape isn't much for a long machine.
Rolls might be anything from about 300 mm to over 1000 of dia. And distance between each of them can be from 200 to 5000 mm, and there might be stuctures between them to prevent simple linear measurement. Machines are tens of meters long.
1) To measure distance between two rolls left and right: This is like to measure diameter of one roll, but the tape is looped between twol rolls and measured left and right sides. Rolls are cylindrical i.e diameter does not vary cross machine direction (no barreling or bow) but they might be of different diameter. I.E. diameter is constant, only explanation to different measuremet is alingment problem (or measurement error).
2) To measure group of rolls like case#1, but looped tape mimics material web track and on two measuremet you can check alingment of many rolls at once.
Is this a new installation, or has it been sitting there for a while?
Don
On new installation we have our installation group with a tachymeter (or theodolite) and they have some special equipment to see over the corner.
This is purely for customers that have no highly specialized equipment and personnel.
I have found one cheap tape used in building industry and specification is nearly good enough for this one. I think I'm going to buy one for my personal use, smuggle it to work and test there against proper measurement equipment.
Pekka