FIELD OF THE INVENTION
The present invention generally relates to Coal Fired Power Plants having Electrostatic precipitations for collection of produced fly ash. More particularly the present invention relates to an external device for monitoring of ash load in the Electro Static Precipitators (ESP).
BACKGROUND OF THE INVENTION
The combustion of coal for power generation produces fly ash, which must collected prior to discharge to the atmosphere. The most common method of collection of fly ashes is electrostatic precipitator. The collection characteristics of the fly ash will depend on the quality of coal and the combustion system. Electrostatic precipitators (ESP) are the most common, effective and reliable particulate control devices which can handle large gas volumes with a range of inlet temperatures, pressures, dust volumes and acid gas conditions. The particles, known as Fly Ash, are collected in hoppers below the ESP and are then removed for transportation on long term storage. Fly ash can be very sticky and tends to build up. Fly ash build up inside the hopper can lead to ESP failures which may result in air pollution, damage to the ESP equipment, lost production (i.e. Power) capacity, causing several implications.

Tracking the fly ash inside the ESP hopper presents quite a few challenges because the material is hot, sticky and abrasive. There is also a lot of suspended dust in the hopper. These properties have made the present system of level measuring with sensors provides inconsistent/inaccurate result.
Electrostatic precipitators are used to eliminate the dust particles from the flue gases generated due to combustion of pulverized material. The electrostatic precipitation process includes the phases of particle charging, precipitation, and removal. All of these phases are affected by the residual layer of particles on either the collecting surface plates or the discharge wires. Thus, periodic removal of this build-up is necessary to maintain the continuity of the precipitation process. Various systems such as Level Sensors, RF Admittance Switch and Mapping Systems utilizing Scanners are being used to monitor the ash in the hoppers. But all of these systems are installed inside the hoppers which makes them very susceptible to failure because of the high temperature environment. Presently the ash deposition in the hoppers are monitored by the level senores of each hopper. The temperature of the ash in the hopper is around 150° C, at this environment, level indicators are not showing consistent value, hence it may further leads to catastrophic failure of the entire structure.

Until now Level monitoring system is being used which measures the level of ash in ESP hoppers. But this system has proved to be inadequate at extreme operating conditions that prevail inside the ESP hoppers which lead to malfunctioning of this system.
The prior-art ash level monitoring system fails to accurately show the accumulation of the ash in the ESP hopper which leads to catastrophic failure of the entire ESP supporting structure including the loss of the infrastructure and power production
In view of the extreme operating conditions that prevail inside the ESP hoppers, it is deemed suitable to install a device outside the hoppers, such as load monitoring device and hence avoid the harsh working environment.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The above brief description, as well as further objects, features and advantages, of the present invention will be more fully appreciated by reference to the following detailed description of the illustrative embodiments in accordance with the present invention, when taken in conjunction with the accompanying drawings in which :

Figure 1 is front view of present invention.
Figure 2 is an Isometric view of the present invention of figure 1.
Figure 3 is sectional view of the present invention of figure 1 and groove details
Figure 4 is a Schematic diagram of strain gauge location of the Present invention Figure 1
Figure 5 is Calibration set up for obtaining the load versus strain of the present invention Figure 1.
DETAILED DESCRIPTION OF THE INVENTION
Referring specially to figure 1 including Figures 1(a), 1(c) and 1(d) of the drawings, the present invention will be described in connection with Electrostatic Precipitator for Coal fired Power Plants.

The advantages of the present invention may be fully appreciated by explaining the arrangement.
Figure 1(a) is a typical prior-art arrangement of a free floating bearing of ESP supporting structure, in which the level measurement instruments are directly connected to the hopper for ash level measurements. Figure 1(b) shows that forces acting on the circular plate of the bearing, these loads are unidirectional loadings by ESP structural weight and collected ash weight, directly acting on the plate through the hopper supporting beams. Figure 1(c) is the load bearing element modified to a measurement device in which strain of the load cell caused due to the ash collection on the hopper is measured. Figure 1(D) showing the FE analysis of the loads acting on the circular plate. Figure 4 shows the schematic arrangement of a measurement device to measure the strain caused due to the ash in the hoppers. Figure 5 shows the calibration of the load cell before installation to ESP supporting structure.
In the preferred embodiment, the device is made as a single module by welding a plurality of plates. The module consists of a bottom plate (1) which is welded to the foundation column of the ESP. A top circular plate (2) of concave shape acts as the main load carrying part taking the load of the hopper supporting structure including ash load acting directly through the ESP beams on the circular

ash Plate (2). In the preferred embodiment, a groove is provided throughout the circumference of the circular plate (2). At least four members of strain gauges (3) are provided to form a Wheatstone-Bridge for measurement of strain by using a stain indicator (4).
According to the invention, the measuring device is configured by converting a spherical bearing which is a part of an ESP structure into a load cell by installing strain gauges in a full bridge configuration. Verification of the performance of the device is successfully achieved by comparing the strain level results between FE analysis of the spherical bearing and experimental measurements in an UTM.
Thus, the present invention provides an external device for measurement of collected ash inside the ESP hopper, based on the strain measured by the strain gauges. Those skill in the present invention may be readily adapted to accommodate a variety of different locations of the hopper supporting columns.

WE CLAIM :
1. An external device for monitoring of ash load in the Electro-Static Precipitators (ESP) comprising at least a supporting structure with a free-floating bearing having a circular plate, and a hopper for ash collection, the circular plate sustaining forces due to unidirectional loading by ESP weight, hopper weight, weight of the support structure, and weight of the ash loaded in the hopper, the device comprising:-
- a single module consisting of a bottom plate (1) welded to the ESP foundation column, and a circular plate (2) disposed over the bottom plate (1) configured in concave shape with a step groove constructed along the circumference of the circular plate (2);
- two pairs of strain gauges (A, B,C,D) one each prior of the strain gauges operably connected being disposed at either side of the single module (1, 2) for measurement of strains generated on the circular plate (2),
where in the strain gauges forming a Wheatstone bridge for measurement of strain which is connected to a strain indicator (4).

2. The device as claimed in claim 1, wherein the load cell is calibrated for the stress vs strain data before installation for measurement of loads directed to the ESP structure.