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Abstract

Contents

Introduction

Modern production processes and devices are generally characterized by complexity and high performance. Increase of production makes the task of ensuring safe and trouble-free production process is particularly relevant. Dangerous situations at work can be fraught with a variety of consequences, including:

Because the best way to deal with the consequences is their prevention   the main task of security management in the technosphere is the diagnosis and monitoring of the technical systems, taking into account the damaging and destructive factors.

Considerable material and human resources expended to solve problems of security in the technosphere, systems are developed and implemented. Thus target security control process is shaped like minimize the risk of man-made accidents at minimal cost [1, 2].

All of the above fully applies to devices and processes of the chemical industry. Overall complexity of the process, unit's work with toxic, flammable or explosive substances, the flow of the processes under high temperatures or pressure, high corrosive effect on equipment   all this only makes it more urgent to avoid dangerous situations.

1. Description of the subject area

Evaporation – the process of evaporation of the solvent from the solution, this process can be followed by crystallization.

Evaporation of the solution used for the separation it into parts of greater and lesser concentration. Ideally, the solution was separated by evaporating the solvent to clean and high concentration solution.

Evaporation achieved the following main objectives: concentration of solutions, the selection of the solvent solution (distillation), the crystallization of dissolved substances. Evaporation is also to jointly achieve several goals. In some cases, the auxiliary function of evaporation plants is steam heating industrial customers. This increases the efficiency of energy use [5].

Evaporator units are widely used for the concentration of solutions in various industries (chemicals, food, metals, etc.) and for thermal desalination of salt water and produce high quality distillate. Great importance evaporators gain in connection with the problem of protecting the environment from pollution by industrial wastewater. They are important links in the technological systems that determine the quality and value of the products [5].

As part of the graduation project dual circuit evaporator unit is considered [6], whose scheme is shown at image 1.1.

Dual circuit evaporator unit

Image 1.1  –  Dual-circuit evaporator unit with one-dimensional control loops

2. The purpose and objectives of the study, expected results

Aim of this study is to investigate the security system for dual circuit evaporator unit.

Main objectives of the study:

  1. Analysis of the personnel operating the evaporator unit.
  2. Method selection of process simulation of incidents.
  3. Modeling dangerous situations that occur during the operation of the evaporator.
  4. Qualitative and quantitative analysis of the model. The definition of reliability models and systems.
  5. Development of the algorithm of evaporator unit's security control process.

Research object: dual circuit evaporator unit.

Research subject: security system of dual circuit evaporator unit.

3. Analysis of the operator evaporator unit

First of all, we agree that there are several possible options for working personnel evaporator unit:

  1. Management of key process parameters is in manual mode.
  2. Management of key process parameters occurs in semi-automatic mode.
  3. Management of key process parameters is automatic.

Manual mode control provides direct work of staff with evaporator unit:

Semi-automatic means managing evaporator unit by means of the operator.

Auto mode is to monitor the parameters of the unit. The operator is only an observer, all control takes over the automatic control system.

Each option of the work with the evaporator unit has a certain degree of risk of dangerous situations. This risk is defined as a human factor in the process control and degradation processes which take place in the evaporator.

To understand the possible dangerous situations, it is necessary to consider the operator's work in every detail of the options.

3.1 Operator's work in manual control mode

Manual control means as a manual start and manual control of evaporator units.

During start-up operator must open the valves according to the structural characteristics and requirements of the evaporator unit.

In the process of evaporation unit operator controls the main technological parameters at the desired level:

The operator is in close proximity to the evaporator unit.

Possible tasks of an operator can also include cleaning evaporator unit.

3.2 Operator's work in semi-automatic control mode

Semi-automatic mode is to control the parameters of the unit, but the operator is not in the close proximity to the evaporator unit, and located behind the operator panel, made in a separate room. Monitoring and control of key indicators is carried out remotely. The operator panel provides the necessary statistical information in conjunction with the taking of indications from the sensors in real time.

Task of the operator in this management scheme – monitoring parameters and adjust them directly from the operator panel, which signals to the actuators located on the evaporator unit.

3.3 Operator's work in automatic control mode

This scheme provides the same location of the operator of the unit, as in semi-automatic mode, but the control of the performance of the evaporator unit is not by a man, but the automatic control system. The operator has the task of monitoring operation of the control system and monitoring indicators, to avoid emergencies in the event of a system failure.

4. The choice of method of modeling

Improving production and environmental security is not possible without taking a single science-based methodology, established by objective view of nature, factors and patterns of accidents and injuries in the technosphere. Such a methodology should justify the choice of object, object and fundamental research methods and improve the safety of production processes [1, 2].

Energy-entropy theory meets the above requirements.

Essence of this concept can be represented by the following statements:

In accordance with the concept of energy-entropy theory and requirements of research problems, the most preferred is the modeling of hazardous processes using influence diagrams.

Influence diagrams represent the process of the emergence of individual premises and their development in the form of the corresponding diagrams of cause-effect relationships. Under such diagrams understand a formalized representation of the simulated categories (processes, goals, properties) as a set of graphic characters and relationships - the alleged links between them. Widespread chart in the form of graphs, trees, and functional networks for different purposes and structures.

As part of this work the influence diagram in the form of trees are considered.

5. Simulation of dangerous situations

Analysis of the object of study, as well as modes of operation personnel can allocate the following striking factors:

Consideration object within energy-entropy theory concepts and the use of the simulation of dangerous situations with the help of influence diagrams impact accidents allow build a tree.

Influence diagram is a cause-effect relationship diagram, which usually includes one parent event, connected by logical conditions with intermediate and initial preconditions. The parent event is an accident or disaster, and its branches – the respective sets of assumptions that form their causal chain. Leaves of the tree – the original event-premise (errors, failures, adverse effects) [1, 4].

The process of appearance a particular incident of this model is interpreted as the passage of a signal from any presuppositions, initiating a causal chain to a main event [1].

Thus, the diagram was built diagram of incidents to a dangerous situation – defeat of human by superheated steam shown at image 5.1.

Diagram of incidents to a dangerous situation - defeat of human by superheated steam

Image 5.1 – Diagram of incidents to a dangerous situation – defeat of human by superheated steam
(Animation: 6 frames, 5 cycles of recurrence, 27 kilobytes)

Legend: {A} –  a set of events, assumptions; {B} –  set of conditions that may result in a human operator; {C} –  set of intermediate events; {D} –  final set of events (accidents).

Incidents: D1 –  the defeat of the human operator with superheated steam.

Notes:

1. Environment – the space immediately adjacent to the evaporator units.

2. Considered that the evaporator unit is equipped with:

Here: A1 – refusal valve supplying superheated steam in the first loop of evaporator (jamming the valve in the closed position); A2 –  refusal of automatic level control loop of the first evaporation (control adjusts the steam valve to the closed position and will not react to changes in the input signal); A3  –  the human operator error (when starting the system does not open the valve supplying superheated steam in the first loop of evaporator); A4 –  failure of the valve supplying superheated steam in the first loop evaporation (jamming the valve in the open position); A5 –  the refusal of the first automatic level control loop evaporation (control adjusts the steam valve to the open position and will not react to changes in input signal); B1 – the human operator is close to the evaporation of the first circuit; B2 –  man-operator is close to the second circuit of evaporator; C1 –  hit the superheated steam into the environment of the first circuit of evaporator; C2 –  hit the superheated steam into the environment of the second circuit of evaporator.

Conclusions

Providing industrial and technological security of evaporator units is an important task, since the occurrence of dangerous situations, emergencies or disasters is the potential for a human, material losses, adversely affects the environment and the environmental situation in general.

Master's thesis devoted to the important problem of research security system evaporator units. As part of the research carried out:

  1. The operation of operators of evaporator unit with different control modes.
  2. Analysis of the object of research, identify potential factors affecting.
  3. The simulation research object using energy-entropy concept and influence diagrams.

Further research is focused on the following aspects:

  1. Reliability analysis of the model and the object of research [7, 8].
  2. Development of algorithm of dual circuit evaporator unit's security control process.

This master's work is not completed yet. Final completion: December 2013. The full text of the work and materials on the topic can be obtained from the author or his scientific adviser after this date.

Source List

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