Basic solutions of Point level measurements
Solutions with one detection block
are applied for tasks of non-contact point level indication, usually solved with the use of traditional radionuclide technology with constant and limited in value (up to 0.3 μGr/h) summary gamma-radiation of background and tested material in the zone of detection block setting.
Classical solution according to traditional radionuclide technology uses intensive radioisotope sources and based on the detection of change of gamma-radiation flow caused by tested material level change.
The Ecophyspribor solution is based on the application of ecologically safe radiation sources or background radiation. In dependence of the actual conditions (vessel dimension, wall thickness, opportunity to place the equipment) one of two variants is used.
Variant 1 (classical):
The source is located on the opposite from a detection block side (along the diameter or a chord) of a tested vessel. If the level of tested material is lower than the level meter horizontal axis, then the average frequency of statistically distributed pulses passing from a detection block to a data processing block (BOI-1) is equal to N1. When the level of tested material is higher than the device horizontal axis, then the radiation is partly shielded and average frequency is lowered to the value N0. In the block BOI-1 average frequency is compared with the threshold periodic frequency n01, being fixed during level-meter set-up between the values N1 and N0. If average pulse frequency from a detection block is higher than N01, then the output relay signal is being formed at the output of a block BOI-1.
Variant 2 (reflective) :
The source is located on the same side of a tested vessel with a detection block. In this case (reflective disposition) if the level of tested material is higher than the level meter horizontal axis, then intensity of gamma radiation is increased at the sacrifice of back-scattered by tested material gamma radiation. Thus, in contrast to the first disposition, the frequency N1 (higher) is corresponded to the upper position of the level and the frequency N0 is corresponded to the lower level. This solution can be used only when the wall thickness of a tested vessel not more than 12 mm (determined by steel), and Na-22 is used as a radiation source. Besides in this case the change in the level of tested material at which the switching of relay contacts is happened, increases up to + 50 mm.
Note. In dependence of the wall thickness of a tested vessel, the additional lead shield above the sense region of a detection block can be mounted. This shield can simultaneously serve as a radiation source Na-22 holder. The additional shield has sizes that depend on concrete problem and is delivered according to special order.
Solutions with two detection blocks :
are applied for tasks with alternative in time radiation properties of tested material and background, for heavy-wall vessels and vessels of large diameter (more than 5 m).
The solution is based on comparison of data of gamma-radiation flow thickness registration from source sodium-22 by two detection blocks:
BD-1, BD-3 or BPU-1K - registers radiation passing through the controlled vessel. Geometry of detection block and emitter location is like in case with one detection block (see above).
BD-2 - registers unimpaired radiation in strictly opposite (relatively emitter) direction (see figure).