"SYSTEM FOR MONITORING THE GASOMETER PISTON INCLINATION".

Fields of this patent:

■ Gasometers.

^■ Industrial and Work Security.

State of the Art.

Steel plants are industries that commercially compete at a world-wide level in which the prices are instantly made up by means of the computer science and whose products - steel of several shapes, compositions and destinations, even the most special ones - behave as commodities. Thus, the quality and productivity patterns are the fundamental elements that the companies make use of in order to keep themselves in the market, to accumulate resources in times of high demand and to survive in times of extreme offers and depressed prices.

The operational optimum level according to what was said above is that the plants operate "in line", that is, all their sectors have to be operating at their maximum level of production and continuity within the quality patterns.

However, as it is not a usual situation, in case a sector has to stop producing for accidental matters or for planned maintenance halts, . there are always intermediate stocks of input, either semi-finished or final products, in order to keep the condition of a trustyworthy supplier in the markets.

Experience determines the volumes of mineral coal, coke, ores, limestone, oxygen, ingots, billet and plates so that even if some intermediate productive sector has to stop for a reasonable time, the following sectors in the processes keep operating. One of the input that must be stored are the gases of the process, such as the coke gas, steel plant gas and blast furnace gas; they are valuable inputs and require special care when manipulated due to the fact that they are poisonous (in few parts per million), they are combustible and they bring about dust, water and hundreds of corrosive and solidifiable chemical products.

Such gases are stored in pieces of equipment called gasometers, which were developed and have been subjected to continuous improvements since the beginnings of the Industrial Revolution in the Eighteenth Century, but that nowadays are found to be set in a mature state of the art. The gasometers work as storeroom for equalizing the differences between the production and the instant consumption of the gases, thus keeping the distribution pressure constant.

Several models of gasometers have been developed throughout history, but, nowadays, the piston gasometers are the favorite type, due to matters of manufacturing costs and experience in managing them.

They are often extremely voluminous tanks of a cylindrical shape. Taking an integrated steel plant of 2.8 million of tons of steel a year for example, a coke gas gasometer has around 38 meters of diameter and 50 meters of height, with a useful volume that can store up to 50.000 cubic meters of gas at a pressure of 60 grams per square centimeter.

Such pressure is set in the beginning of the plant's project and it is a determiner of the diameter of the tubes and countless other pieces of equipment, it is constant and it is ensured by the relation between the gasometer piston weight and its area. The Figure 1 schematically illustrates, in a side view, a typical gasometer with its piston, which allows the production of the constant pressure that it makes over the gas that is stored in its interior.

In it, we can see the gasometer (1) with its piston (2), the seal ring (3), the entrance duct (4), the exit duct (5), the drainpipe of condensed (6) and the leveling weights (7) which are usually made of concrete blocks.

In the present example, the piston (2) is built of steel plate and has 10 millimeters of thickness, it has a great number of structuring profiles and leveling weights (7); it is its final weight that determines the constant operational pressure.

Despite their conceptual simplicity, the gasometers - especially those destined to coke gases - are pieces of equipment that require constant attention because any accident with them can potentially cause huge economical damages and human lives loss. The Figure 2 shows schematically details a cut view of the sealing system between the gasometer body (1) and the piston (2), constant of the lubrification system with grease of high stability and high viscosity and the polymer gaskets (8) generally made of synthetic rubbers.

Such sealing devices are projected so that the piston (2) can move up and down according to the balance of entrance and exit of the gases which is always leveled.

The biggest problem of the State of the Art is related to this movement of the piston (2): - in spite of the large areas of the piston (2), around 1 ,250 square meters as it is the case of the cited plant of two billion and eight hundred tons of steel a year, it has to go up and down absolutely parallel with the ground, leveled, without putting up any other resistance to this movement besides the weight, so that the pressure of the lines of gases keeps constant.

The State of the Art comprehends, therefore, the constant monitoring of the movement of the piston (2), so that it does not move inclinedly, and the strict maintenance of the operational conditions through the injection of grease into the gaskets (8).

Even with strict observation and maintenance, the inclined movement of the piston (2) is often; as for the coke gasometers, the gases and steams derived from the process of turning mineral coal into coke have, besides water and ammonia, over one thousand and two hundred substances such hydrocarbons and their derivatives, some such as tars, whose fusing, point exceed four hundred Centigrade.

These substances are not thoroughly dragged out by the sub-product plants, such as the ammonia, tars and BTX.

Now, besides producing corrosion, such substances adhere to the gasometer walls and to the seal ring (3) of the piston (2), sticking them in certain spots, which causes an inclined movement that can lead to catastrophes as the one cited above. It is important to record that the gasometers cannot allow leaks, both due to the risk of explosions and fires and due to the fact that the gases held in them are poisonous, which means that the seal has to be perfect, even if standing the friction of the constant ascents and descents of the piston (2).

The Figures 3A and 3B provide the necessary illustrations for understanding the monitoring way granted by the State of the Art that this patent comes to notably advance.

The current State of the Art is based upon the data provided by a piece of equipment called "inclinometer" (11) that has one of its shapes schematically illustrated in a side cut, in Figure 3, which basically consists of a pendulum (9) that can freely move in the interior of a cylinder (10) in whose walls there are about eight coils (12) that integrate oscilators whose oscilation frequencies are the function of proximity and distancing of the pendulum metallic mass.

The Figure 3B is a schematically horizontal cut of the "inclinometer" (11) in which the pendulum (9), the cylinder (10) and the coils (12) placed in equidistant positions can be seen.

The electrical analog signals derived from the coils (12) are carried to the gasometer (1) control panel where they are compared with a standard signal thus generating signals that indicate the inclination on the panel and alarms in case it is above certain limits. The repetition of the inclinations in certain directions, which occur when the piston (2) reaches certain heights, leads to other operations of correction, such as the redistribution of the leveling weights (7) and the lubrification of the gasometer walls, since the maintenance and change of the gaskets can only be made when the gasometer is empty, purged with gases in planned halts [GAI]

As the "inclinometer"' (11) is placed in the center of the piston (2) top of the gasometer (1) whose diameter is around forty meters, it is noticed that for the more sensitive the electromechanical "inclinometer" can be, it is necessary to have signals of a certain intensity for it to operate, that is, that the inclinations that may occur reach significant levels to be detected, which is always an undesirable situation and that constitutes one of the crucial points that this patent comes to eliminate, while it also advances by presenting a processing system and the aggregation of intelligence of a high operational and scientific value.

Advances introduced by this patent on the State of the Art.

With the "SYSTEM FOR MONITORING THE GASOMETER PISTON INCLINATION", object of this patent, one can obtain:

1 - a great increase of the security and accuracy of the gasometer piston leveling measuring data due to the replacement of the electromechanical "inclinometers" w ^' ύh highly accurate and reliable laser measurers;

2 - the automation introduction by a particular software, with a high level of integrated intelligence, for processing the data gotten from the laser measurer in real time, making it possible to provide the instant data and reports to the whole plant; 3 - increase of the gasometer useful lifespan;

4 - better lubrification between the piston seal system and the gasometer walls;

5 - a more accurate balance of the gasometer piston;

6 - reduction of the gasometer piston seal rings consuming;

7 - a great reduction of the risk of an uneven movement of the gasometer piston.

Description of the " SYSTEM FOR MONITORING THE GASOMETER PISTON INCLINATION".

The "SYSTEM FOR MONITORING THE GASOMETER PISTON INCLINATION", object of this patent, is consisted of three, or preferably four or

any other number, level laser measurers placed on the gasometer ceiling, away from each other at 90°, in the particular case of using four measurers, which provide preferably digital signals, but can also provide analog signals, to a Field Control Station where these signals are basically processed and from where they are sent , in a compatible interface, to the management and historical series database treatment system, usually called PIMS - Plant Information Management System, where by means of a particular software, they are compared to parameters and data of a historical series and whose results are sent to the Plant's operational net. The signals basically processed at the Field Control Station are immediately sent to the control panels in graphic images and/or numerical information as well as they will release alarm signals in case of exceeding the maximum allowed values.

The Figure 4 is a schematic illustration of the application and a flow chart of the "SYSTEM FOR MONITORING THE GASOMETER PISTON INCLINATION"; in it we can see the four laser measurers (13A)... (13D), which consisted its preferable construction, placed on the ceiling (21) of the gasometer (1), away at

90°, suitably connected to the hardware that runs the basic software (14) of the

Field Control Station (15), the gasometer (1) Control Panel (16), the alarm terminals (17), the PIMS (18) with its database (19) and specific software (22) and the operational net (20) to which the processed data are sent.

The operation of the "SYSTEM FOR MONITORING THE GASOMETER PISTON INCLINATION".

Taking into account that the "SYSTEM FOR MONITORING THE GASOMETER PISTON INCLINATION", now described, is consisted of a system in which the data about the inclination of the gasometer (1) piston (2) provided by laser measurers (13A)...(13D) are processed by a basic software (14) and by a specific software (22), we have actually an innovative automatic system of information and control consisted of the laser measurers (13A)...(13D), the basic software (14) and the specific software (22).

The measurers (13A)... (13D) are market pieces of equipment and they do without description; the softwares, both the basic software (14) and the specific software (22) are described next, with a priviledge focused on the aggregated operational intelligence. The basic software (14) alone is not an object of this patent in means of innovation, since it is actually about the classical interface of immediate availability of the data on panels, the alarm release and the supply of data for further processing and storage and, although it is part of the system, it is not the target of specific claims. The system that composes the "SYSTEM FOR MONITORING THE GASOMETER PISTON INCLINATION" supports the advances in the State of the Art that proposes the replacement of the electromechanical "inclinometers" with the laser measurers and it aggregates a great intelligent content in a specific software (22) as it is described as follows. Once the laser measurers (13A)...(13D) were installed, the problem of identifying the biggest unevennesses of the piston (2) arised since there wouldn't be any guarantee that they would occur at the same spots where they were installed.

The mathematical solution for solving this problem was to calculate algebraically, from the data provided by the laser measurers (13), the unevenness in each pair of asymmetrical columns; now, as the four laser measurers (13) provide, in real time, the distances between the gasometer (1) ceiling (21) and the piston (2) and, as only three points determine a plan, the particular software (22) gathers the signals provided by them into groups of three laser measurers (13), which produces four plans from which a medium plan is calculated, namely Piston Reference Plan.

The specific software (22) calculates the intersection of the Piston Reference

Plan with the points of the cylinder walls of the gasometer (1), which allows the attainment of the height of the other points throughout the piston(2) surface, referred to by the height of the cylinder columns that make up the gasometer

(1)-

Deciding for four - or over - laser measurers (13) rather than only three of these tools is due to matters of obtaining the maximum security as it is an absolute responsibility for the operation of plants, like the steel and petroleum ones, in which great numbers of poisenous and combustible and inflammable gases are manipulated. Although only three points determine a plan and, theorically, three reading points would be enough for operating the system, the aggregated intelligence goes further and it advises four - or more than four - and incorporates the possibility of diagnoses and the dispose of values that exceed the historical deviation of the measurements to trie specific software (22), being that the integrity of the system remains tentatively kept by the operation with only one reference plan determined by the three reading points.

Once the computer data that correspond to the heights of each point of the piston (2) surface related to the cylinder walls that form the gasometer (1) are obtained, they are processed by the specific software (22), addressed to the database (19) of the PMIS (18) and it makes the following reports and information available:

1 - Immediate and historical reports on the gasometer (1) operation that are made available online, in real time, for any period of time, indicating the unevenness of the piston (2), date, time and value of the event, in which column of the gasometer (1) it occurred, the level and the internal pressure of the gasometer (1).

2 - Reports related to the operational quality such as the occurrences of measurements above the security limits, valid performed measurements, discarded measurements and the percentage of the valid measurements above the security limit.

3 - Graphics of the behavior tendency of the piston (2), "radar" graphics of the inclination of the piston (2), bar graphics for historical analysis and parameters online, such as the inclination of the piston (2), internal pressure of the gasometer (1), the gasometer (1) level and the friction between the piston (2) and the gasometer (1 ) walls.

Another group of valuable information provided by the specific software (22), in real time and on historical bases, is the analysis of the graphic of the inclination of the piston (2) related to every filling level of the gasometer (1) for detecting lubrification flaws in certain points of the seal ring (3), since the interfaces and the graphic pages of the reports of the specific software (22) show that such flaws arise as momentaneous, abrupt and perfectly located inversions in the direction of the inclination of the piston (2) and the great value of this piece of information is the immediate possibility of correcting its causes, by making an extremely safe operation once such events may become alarm signals. Still due to the resources offered by the interfaces and graphic pages, the specific software (22) allows, in case the piston (2) is stalled as what happens when there are temporary interruptions or other events with ^' energetic demands at the steel plant, to identify its "natural" inclination level, which can be corrected right away by the distribution of leveling weights (7) along the perimeter of the piston (2).

The description above is enough to claim it as a presentation of a valuable evolution of the State of the Art and it allows us to ^' recognize that, by implementing it in the gasometers - applied to any kind of industrial plant - the following results can be acquired: 1 - the immediate attainment of information on the specific spots the lubrification must be made to prevent the piston (2) to produce inclination;

2 - a great increase of the gasometer operational security, performed in distant conditions from those critical ones and of an immediate recognition, being spread online through all the net in real time, supported by resources of alarms of various levels;

3 - Continuous maintenance of the piston at the correct balanced level;

4 - Reduction of the seal ring consuming,

5 - Increase of the gasometer useful lifespan.