Measuring and testing – Liquid analysis or analysis of the suspension of solids in a... – Content or effect of a constituent of a liquid mixture
Patent
1985-11-27
1987-07-07
Levy, Stewart J.
Measuring and testing
Liquid analysis or analysis of the suspension of solids in a...
Content or effect of a constituent of a liquid mixture
73 54, G01N 1100
Patent
active
046778462
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to measuring and regulating the concentration of a fibre suspension, particularly within the pulp and paper industry, although the invention may be used within other areas, such as measuring the dry substance content in sewage sludge, peat suspensions, mineral wool suspensions etc.
Three main groups of transducers may be recognised for measuring the concentration of fibre suspensions, namely shear force transducers, optical transducers and transducers working with pressure drop changes or flow speed changes depending on pulp concentration. There are further groups of subordinate importance. Transducers working according to the shear force principle may be divided into two main groups, namely rotating and static transducers.
The transducer of the present invention may be suitably placed in the group "static transducers", although there are certain principle differences compared with other devices in the group. Colloquially, these transducers are called static or stationary transducers, shark fins, blade transducers and fins. The static transducers compete to a minor extent with the rotating type, since the latter usually have better measuring accuracy, higher sensitivity, less flow sensitivity shorter unactivated times etc. Users install static transducers primarily in positions where performance requirements are not too high.
The static transducers known up to now include a pivotably suspended blade placed in the pulp flow. The suspension most usually comprises some form of mounting and a seal against the medium. Due to the flow speed in the conduit there is a shear force moment on the blade, this moment being converted to a standardized output signal, which may be pneumatic or electric. The moment converters work either according to the weighing balance principle or the force balancing principle. It is thus the front edge of the blade exposed to the flow which cuts through the fibre flow to generate the shear force moment. Since the working principle requires that the medium is in movement, it is easy to understand that a certain, undesired flow sensitivity occurs. The manufacturers have attempted to solve this problem by resorting to more or less sophisticated implementations of the blade. The results of these efforts vary, but the general opinion is that the dependency on flow in static transducers is one of three dominating problem areas for the group as a whole. The consequence has thus been that the manufacturers stipulate relatively tight flow ranges within which the transducers may be used, around 0.5-3 m/s and in some cases as tight as 0.3-1.5 m/s. To obtain a flow within these limits the conduit must be tapered diverging or converging in certain cases, which considerably increases the installation. The next problem area is also brought about by the measuring principle, since the blades are usually relatively voluminous and occupy 80-95% of a 100 mm diameter conduit. The formation of plugs or the presence of larger solid bodies moving with the fibre flow in the conduit quite often damages the blade and its suspension. The front edge of the blade cannot, of cource, be protected by a barrier placed too close it, since the measuring result would then be compromised. A smaller barrier protecting the suspension shaft of the blade is usually integrated in the structure, however. Effective damping systems cause some makes to be less sensitive to vibrations than others.
It was mentioned in the introduction that rotating transducers give greater sensitivity to concentration changes. This is a generally accepted fact, and the chief reason for there being little competitionbetween the groups. The higher relative difference in speed between sensor and fibre network in rotating transducers gives a higher moment level, in spite of the minor size of the sensor, and in turn this results in higher sensitivity and better signal
oise relationship. This becomes particularly noticeable for low concentrations. While static transducers may be used down to 1.5-1.75% concentration, the rotat
REFERENCES:
patent: 3286507 (1966-11-01), Moore
patent: 3474663 (1969-10-01), Whitmer et al.
patent: 4062226 (1977-12-01), Hietala
patent: 4148215 (1979-04-01), Hofstetter, Jr.
Eur-Control Kalle AB
Levy Stewart J.
Roskos Joseph W.
LandOfFree
Method of measuring and regulating the concentration of a fibre does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of measuring and regulating the concentration of a fibre , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of measuring and regulating the concentration of a fibre will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1655834