Guidelines for man-machine interface design

During the past years the 1eve1 of automation has considerably increased in modern process plants. One of the consequences has been the changing role of process operators. The operators have to make decisions on a quite abstract level and with abstract conceptions concerning plant ecnomy, safety, availability and product quality. Threfore control room design has becme an important factor related to plant safecy, economy and reliability. The disturbance and accident anlysis in process plants indicate that most of the deficiencies in existing process control rooms can be avoided by improving the design prcess itself and by ensuring that the Jesigners include to an adequate degree all factors which are relevant and essential to the man-machine interface (MMIF) system and to the operation of the plant at different design stages. The guidelines are intended to provide support in ensuring that everything essencial is included in MMIF design. Application design is a long process involving several persons from various corporate organization levels. It is also usual that outlines are created at different orgnization levels for delegating tasks and for use by lower levels in designing concrete activities. From the viewpoint of automation and instrumentation projects, three essentially separate decision-making levels can be discerned, i.e. preparation of outlines and making of decisions at different levels of detail; the levels are also critical node points in MMIF design. At the top level, Level I, decisions are made concerning the launching of the project. This level can appropriately be called the top management level. This level creates the general outlines, concepts and criteria for later project phases. The top tevel arranges studies on such items as productional aims and the suitability of different implementation alternatives, including automation, and uses these to decide on the design project and its implementation method. Consultants and preliminary projects can be used in the studies This is the case especially in the areas that seem to become crucial and problematic. Leve1 I has the highest number of degrees of freedom, and This is why correct and exact selection of aims and criceria can have a strong effect on the conditions and implementation of MMIF design. At a decision-making level, Level II mainly corresponds to automation and instrumentation project management, which makes the decisions scheduled according to Level I outlines or to suggestions from project members. This level concretizes the Level I outlines as a concrete automation system concept, and ensures that the practica1 design work proceeds according to the outlines specified. Decisions made at this level naturally carry a great importance to MMIF implementation. Typical topics decided at this level include the level of automation, basic MMIF design, coding system, instrument selection, procedures, etc. Level III corresponds to the design and implementation work carried out by project members according to the Level II and project management decisios and guidelines. Tied to schedules, the work involves the practical implementation of specified sub-areas, such as cntrol system parmeter design, detailed MM1F design, instrumentation scale design, etc. At this level the nmber of choices and the degrees of freedom are at a minium. The designer is forced to follow the technical conditions and Level II criteria. The structure of guidelines and checklists should correspond to that of the decision-making system. This is why these guidelines and checklists are divided into three concretion categories according to the decision-making level for which they are written .The guidelines are mainly intended for use as a decision-making aid to ensure that the background factors affecting decision making will be taken into consideration at a sufficiently early stage, and that the requirements of the goals set will also be properly reflected in the decision-making process. Checklists are used at different decision-making phases to ensure that the design has been implemented according to the specified aims and outlines.