GB2044966A - Apparatus for selectively reproducing engineering drawings by computer - Google Patents

Abstract

A computer has an address coded store of flow diagram symbols, circuit wiring diagram symbols and schematic circuits of the related instrumentation and control systems and interfaces, and other data relating to cable schedules for said systems. Input sheets are matrix coded so as to receive the symbols and data relating to the respective flow diagrams and circuit wiring diagrams whereby input data is transferred, with the aid of matrix coding, to the computer store. This provides the advantage that an engineer prepares the input sheets but these are readily interpretable by a teletype operator. A further advantage is provided in updating the drawings to show amendments, by collating input sheets prior to data transfer to the computer. A plotter and/or printout device reproduces the stored symbols and data, the computer being programmed to selectively reproduce the stored symbols and data. On a given input request, a drawing is reproduced in a single sheet format wherein designated areas contain a flow diagram, the wiring diagram showing the respective control/instrumentation interface, the schematic diagram and the cable schedule for the respective process or part process. Secondary drawings may be reproduced which illustrate a particular component or components which are in store for reproduction of one or more of the single sheet format drawings.

Description

SPECIFICATION Method and apparatus for reproducing engineering drawings by a computer The invention relates to a method and apparatus for reproducing drawings by a computer, which drawings represent the processes and process control systems of a process control plant.

It is customary, to produce separate sets of drawings for respective electrical and instrumentation systems forming parts of a process control plant. Interfaces between the two systems are usually shown by cross-referencing the two sets of drawings. As these sets of drawings are prepared by people working in different fields of engineering, similar components, shown on both sets of drawings, may be differently designated. Such an overlap of information requires changes to be made on one or other set of drawings and this can result in mistakes.

With the increasingly widespread use of computers and related equipment for controlling process plant, problems of interfacing electrical and instrumentation systems and depicting them on drawings have become accentuated. There are two main problems namely: (1) how best to represent the different process control systems on drawings which are suitable for design, manufacture, installation, commissioning and maintenance, and (2) how to ensure that interfaces between different systems are clearly defined and illustrated.

Automated information retrieval systems are known wherein stored information can be retrieved on request, for selective duplication. However, such retrieval systems are not known to be purpose designed to overcome the latter problems. On the other hand, the invention enables the reproduction of drawings, each of which represents, in singlesheet format, a process to be controlled, the related process control systems with interfaces and a schedule of some of the components used in the process control systems. Such drawings may be readily interpreted by engineers and by production and maintenance personnel. Moreover, some of the information, on each drawing, is prepared in a diagrammatic form in such a way that it can be readily transferred, by non-engineering personnel, to a computer.

More particularly, the invention employs apparatus for selectively reproducing drawings which represent respective processes, or part processes and related instrumentation and control systems with interfaces therebetween, the processes being those of a type with a centralised control, the apparatus comprising a computer which has an address coded store of flow diagram symbols, circuit wiring diagram symbols and schematic circuits of the related instrumentation and control systems and interfaces, and other data relating to cable schedules for said systems, a plotter and/or printout device being provided for reproducing the stored symbols and data, the computer being programmed to selectively reproduce the stored symbols and data, by the plotter and/or printout device, such that on a given computer input request a drawing is reproduced in a single sheet format wherein designated areas contain the flow diagram, the wiring diagram showing the respective control/instrumentation interface, the schematic diagram and the cable schedule for the respective process or part process.

The wiring circuit diagrams are preferably in block circuit form, the blocks representing the related electrical and electro-mechanical process control systems and the respective instrumentation and control system interfaces.

Preferably, the apparatus includes input sheets which are matrix coded so as to receive thereon the symbols and data relating to the respective flow diagrams and circuit wiring diagrams whereby input data is transferred, with the aid of the matrix coding, to the computer store. This provides the advantage that an engineer, in the discipline concerned, prepares the input sheet in a form readable by other engineers but also readily interpretable by a teletype operator, who is not an engineer in the discipline concerned, to transfer the data to storage in the computer. A further advantage is provided in connection with updating the drawing to show amendments.For example, if revisions are necessary on several drawings, these may be carried out and recorded on the appropriate input sheets which are then held, to collate all revisions, prior to transferring the data to the computer before the next issue of drawings is required. This facilitates updating of the drawings which would otherwise need to be amended, on a sheet to sheet basis, as each revision was produced.

The computer is of basically known construction so no detailed explanation is necessary in this respect.

Similarly, standard programming techniques may be employed to follow the teachings of the invention.

The computer is also preferably programmed so as to reproduce secondary drawings which each illustrate a particular component or components which are in store for reproduction on one or more of said single sheet format drawings. The components may be related, for example, by a common terminal strip. This enables maintenance or production personnel to obtain, on respective computer input requests batches of secondary drawings showing the components of interest.

The computer is preferably programmed to verify, with respect to the flow diagrams, the input/output connections of the wiring circuit diagrams. It is also preferably programmed to retrieve information from the store of the data of the wiring circuit diagrams so as to assemble some of the data on the cable schedules.

The cable schedules suitably show terminals of cable core ferrules cross-referenced by address codes to respective circuit wiring diagrams. The schematic circuits may illustrate, for example, motor control circuits used in the field of electrical process control engineering.

The invention also provides a method of selectively reproducing drawings which represent respective processes, or part processes and related instrumentation and control systems with interfaces therebetween, the processes being those of a type with a centralised control, the method being effected by a computer together with a plotter and/or printout device and the method comprising the steps of:: (a) storing address coded data representing flow diagram and circuit wiring diagram symbols; (b) entering said symbols on matrix coded input sheets in the form of flow diagrams and related circuit wiring diagrams of said processes or part processes; (c) transferring the information on the input sheets, with the aid of the matrix coding, to the computer store; (d) storing address coded data representing schematic circuits and information pertaining to cable schedules relating to said flow diagrams and circuit wiring diagrams; (e) programming the computer to reproduce, in a single sheet format for each process or part process, a drawing wherein designated areas contain the flow diagram, the wiring diagram showing the respective control/instrumentation interface, the schematic diagram and the cable schedule for the respective process or part process; and (f) making an input request or requests to cause the plotter and/or printout device to reproduce the respective single sheet format drawing or drawings.

One way of carrying out the invention is described in detail below with reference to the drawings which illustrate only one specific embodiment, in which drawings: Figure 1 illustrates an input sheet on which a flow diagram is to be entered, Figure 2 illustrates another input sheet on which a block circuit diagram is to be entered, Figure 3 illustrates the input sheet of Figure 1 in which a flow diagram has been entered to show a particular process to be implemented in a process control plant, Figure 4 shows the input sheet of Figure 2 in which the block circuit diagram components have been entered of a control circuit related to the process shown in Figure 3, Figure 5 is a continuation input sheet to that shown in Figure 4, and Figure 6 illustrates a reproduced drawing showing, in predetermined regions, a flow diagram (left-hand side), a block circuit diagram (centrally of the drawing), a component schedule in the form of a table (top right-hand side), and a schematic circuit diagram (beneath the table).

A description will first be given of Figure 6 since this represents a typical drawing reproduced by the computer. A description will then be given of how the data and information is prepared and transferred to the computer so as to reproduce such drawings. A description will not be given of the construction and operation of a suitable computer, which includes a plotter and/or other print-out mechanisms, as this will be known to those skilled in that art.

Referring to Figure 6, each drawing has predetermined regions 2,4,6 and 8. These regions are more clearly indicated by the broken vertical lines 10, 12 which are spaced by the distance indicated by the broken line 14, and by the horizontal broken line 16 defining a boundary between regions 6 and 8. These broken lines have been included merely to indicate the regions concerned.

Region 2 contains a flow diagram 18 which depicts, in standard symbolic form, a process to be controlled in the processing plant. Region 4 contains a block diagram 20 which depicts a control circuit and components therein for effecting the process shown by the flow diagram 18. The table in region 6 is a cable schedule related to the control ciruit represented by the block diagram 20. Region 8 contains a schematic circuit diagram 40 of motor control circuits used in the block diagram 20.

The regions 2, 4, 6 and 8 may contain different data or information, and may be of different shapes, but the data or information concerned always appears in the same region on each reproduced drawing.

The reproduced drawings best represent the processes and process control systems wherein control and interlocking functions are carried out by a computer or programmable controller. The following description assumes such a situation. However, with a few minor modifications to the foRrnt! the drawings would be suitable for representing systems having an alternative centralised control such as those employing relay or solid state logic.

Referring again to Figure 6, the flow diagram 18 in region 2 illustrates the steps in a process (as shown in more detail by the example on the input sheet of Figure 3). The flow diagram illustrates the process in such a way as to guide and to conform the design of the appropriate control circuitry represented by the block circuit diagram 20 and a schematic diagram 40. The flow diagram can be easily interpreted by all concerned, including, for example, a customer of a manufacturing company producing the equipment concerned. It may also indicate the requirements of the control equipment both in terms of a required program and the number of inputs and outputs to other equipment.In the example shown in Figures 3 and 6, the flow diagram 18 illustrates a process which involves stopping and starting a mixing drum, opening and closing the drum and ensuring that the process is running according to design with adequate supporting facilities such as lubrication and annunciation. This is but one example of a typical process. The flow diagram occupies the left-hand side of the drawing shown in Figure 6 and up to 25% of the width of the sheet and its full height The flow diagram symbols are in accordance with British Standards, or some other given standard, and are drawn on the matrix of 3 columns of 12 rows. These columns are designated B, D and F in the input sheet of Figure 1 and the rows are designated by the even numbering 2, 4, 6....etc. on the same input sheet.

Intermediate rows and columns on the input sheet to Figure 1 are used forthe interconnecting flow lines.

Flow drawings can continue from one drawing onto as many subsequent drawings as are necessary to complete each section of a process control. Within each flow symbol or box, is explanatory text to define the process logic. Each symbol, which corresponds to an input/output of the control equipment, is allocated a "bit" number or numbers which also appear within or adjacent the symbol. These numbers can be allocated in a numerical sequence commencing 001 or 0001 for a particular project.

The wiring block diagram 20 in region 4 also occupies the full working height of the sheet and up to 40% of its width. Down the right hand edge of this region is a column of twelve blocks 22, each of which is used to represent an input or output interface of the control equipment. The internal content of the control equipment may be considered to be right of this column and is not shown on the sheet. Its function is however described by the flow diagram 18. To the left of the column of blocks 22 are blocks which represent electrical equipment and wiring connected thereto. From each of the blocks 22 representing a respective input/output interface, there will be developed an external primary circuit. The total number of primary circuits on each diagram (maximum twelve) will be termed a "group".

It should be noted, that the space requirements, i.e. the number of drawings (as exemplified by Figure 6), required for a given flow diagram 18, may well vary from the number required for illustrating the associated wiring block diagram 20. When the flow diagram 18 and wiring block diagram 20 have different space requirements, certain input/outputs shown in a flow diagram 18 on one particular drawing also appear on the wiring block diagram of a different drawing. In order to prevent the two sections getting out of step to a degree that would create difficulties in reading the drawings, spaces can be left, at suitable intervals, to allow the more lengthy section to "catch up". For example, if a particular section of process required two flow diagrams but the associated wiring block diagrams amounted to three, the left hand section of the third drawing should be left blank.In other words the next section of the process would commence with both flow and wiring diagrams on the fourth drawing.

The column of input/output blocks 22 effectively divides the designated row boundaries (only one of which is indicated by broken line 24) of twelve rows each forming the boundary of the external circuitry. The circuits are drawn as connection diagrams with terminals and terminations identified and cross-referenced.

Some items of equipment are shown schematically, e.g. pushbuttons 26, solenoid valves 28, limit switches 30. Other items are shown as blocks 31 and input and output terminals 32,34. In the case of motor control cubicles 36, terminals 38 are cross-referenced to the schematic circuit diagram in region 8.

The development of each circuit starts with identification of an input or output from the flow diagram 18. In this example, the input or output to be identified is that of a flow diagram designated by bit numbers B301, B302...(see Figure 3). The first input/output B301 is allocated the first available block 22 on the wiring block diagram 20 and details of the interface are added, i.e. duty (from flow diagram 18), bit number (from flow diagram 18), contact rating or signal level, rack location (where known) and terminal numbering. The circuit is then completed by adding the required devices and cabling within the confines of the row containing the first block 22. Standard symbols are used and these are of a size which is an integral multiple of a given fixed size and have a maximum of five device terminals or five cable cores per row.

A device having more than five terminals is extended into adjacent rows. The input/output blocks 22 associated with these additional rows will then remain unused, unless the device concerned has multiple connections to the control equipment. For example a motor control panel may have an input to and an output from the control equipment which would occupy two rows. The secondary items may then "fan out" into say three rows for a motor, a pushbutton unit and a selector switch. The total number of rows used for this circuitry would therefore be three with the input/output block of the third row being unused.

To represent multicores on a drawing the engineer may require to show the cores joined together as one multicore or alternatively show them as a series of cores all carrying the same cable number.

This choice will be given every time a cable is entered. The computer will ask the operator how many blocks the device will take up.

If a series of cores are required then the answer would be one block.

The information concerning the number of blocks would be entered on the input sheet in the space allocated for free hand sketches.

When a particular circuit is too long to be accommodated on one row of the wiring block diagram 20, it is turned round at the end of the row and continues on the next row. The input/output block on this second row will remain unused.

Each type of drawing is designated with a drawing number obtained, for example, as follows: (1) 0-99 - General arrangement drawings, distribution drawings etc.

(2) 100-999 - Primary drawings (computer produced control etc. diagrams).

(3) 1000-1999 - Secondary drawings (computer produced drawings showing information which appeared on more than one primary drawing).

(4) 2000 - Drawings - manually produced drawings e.g. hook-up drawings etc.

Each item of equipment shown on the wiring block diagram 20 is identified by a unique number.

Each item on the wiring block diagram 20, with the exception of drive motors, forms part of the electrical and instrumentation of the plant, rather than being considered as part of one of the "mechanical zones".

Drive motors are considered as sub-units of the driven equipment and have their register numbers so derived.

The electrical and instrumentation zone number forms part of each drawing number thus: Drawing Number 185001/26/501 wherein, 185001 is the project number 26 is the zone number 501 is the group number.

The project and zone numbers remain the same for all drawings of a particular project. The group number is unique to each drawing and is designated by a number 100-999.

The equipment register number for each item comprises three part namely, Register Number (the number of a register on which the same types of item are listed).

Unit Number (the actual number of the item of a given type).

Zone Number (the zone as indicated by the drawing number).

For example, the equipment register number may appear as 26501 01.

Generally, the unit number of each item is the drawing number on which the item is shown. However certain items will be common to several different drawings and the number will be derived from the first drawing on which the item appears.

Thus, for each drawing, the first two parts of the equipment register number will be common to all items (with the latter exception). The third part of the number is unique to each item on the drawing and is allocated in numerical sequence from 01 to 99 for each drawing. The equipment register number shown against each item on the drawing is abbreviated to the last two parts, i.e. omitting the zone number. The full three-part number will however appear on an identification plate affixed to the item. In addition to the equipment register number, certain items shown on the drawing may be identified by a loop number. The loop number will be independent of the register number and will denote items having a common duty.

Cables will be identified by unique numbers, the number of digits being chosen to suit the size of project.

Five-core groups of the same cable will carry the same cable number.

An item of equipment which appears on more than one primary drawing e.g. control desk terminal rail, M.C.C., Junction Box etc., may be reproduced on a common drawing called a secondary drawing. The secondary drawings are designated by drawing numbers from 1000-1999 and are recorded on a short code specification sheet.

e.g. M.C.C.1. = 1000 M.C.C.2. = 1010 Control Desk= 1020 This enables a computer operator to call up all the information associated with any item of equipment i.e.

M.C.C.1 on a secondary drawing. It is possible that all this information may not be contained in a single drawing. Therefore, each item of equipment will be allocated 10 drawings, i.e. M.C.C.2 will commence on 1010.

The designated secondary drawing number for the equipment will appear on the input sheet i.e. for M.C.C.1 it would be 1000. If more than one secondary drawing is produced for any item of equipment it would be allocated a sequential number e.g. 1001, 1002 etc.

Terminals and cable core ferrules can have independent numbering systems which can be crossreferenced on the drawing concerned. Each set of terminals is numbered sequentially for each device or terminal strip. Thus the same terminal number may appear several times on one sheet or drawing but only once on each device or terminal strip. Cable cores will have unique numerical identification comprising of two three digit numbers. The first number will be a wiring prefix which will correspond to the unit (diagram) number of the drawing on which the cabling appears. The second number will range from 001 to 999 for each drawing. Only the second number will be shown against the cores on the drawing, the pefix being indicated at the top of the cable schedule. Ferrule identification need not be shown at every termination point.If the connections are clear and unambiguous by confining the identification to the extreme ends of the circuit, it may be omitted at intermediate terminal strips etc. However the installation contractor will ferrule every connection with the full six-digit identification.

The cable schedule represented in region 6 always appears (in this example) at the right hand side of the drawing and it occupies approximately 30% of the width and 50% of the height of the drawing. The schedule comprises a list, in numerical order, of cables which appear on the drawing concerned. The following information is included on the schedule: 1) Cable Number 2) Cable Route 3) Voltage 4) Load Current 5) Number of Cores 6) Conductor Size 7) Cable Length 8) Cable Type 9) Core Identification (ferrules).

Some cables will appear on more than one schedule because some cores are used on one drawing, other cores on different drawings. Only those cores appropriate to the particular drawing will be shown on each schedule.

If motor control equipment forms part of the content of the block diagram 20, a motor control schematic circuit 40 (region 8) is included on the drawing underneath the cable schedule table 6. It is important that the number of differing schematics be kept to an absolute minimum for each particular project, or ideally for each customer. The terminal numbering shown on the schematic circuit 40 will correspond to that on the block diagram 20, thus presenting the complete information for commissioning and fault-finding.

A description now follows with reference to data input for computer controlled plotting.

As the sheets or drawings are to be produced on a computer-controlled plotter, the content of each diagram 18 and 20 is defined by the design engineer in a form suitable for input to the computer via a teletype terminal. The actual input of data can be undertaken by non-engineering personnel after the engineer has completed a series of "input sheets" which can be readily interpreted by the teletype operator.

The data input technique is based on standard computer practice, for example, the computer will "question" the teletype operator who will answer in accordance with the data on the input sheets. Input sheets will be required for the flow diagram 18, and the wiring block diagram 20 and an input statement for the motor control schematic 40. The basic information to build up the cable schedule 6 will then be available to the computer although a secondary input of supplementary cable details will be required. The proposed methods of data entry for each region of the drawing are described below.

A desccription will first be given in connection with the use of the input sheets shown in Figures 1-5. These input sheets, are compiled by an engineer and the data is then entered from the input sheet into the computer by a teletype operator on a question and answer basis, the answers being obtained from the input sheet. The input sheet shown in Figure 3, which includes a flow diagram 20 drawn over the matrix of Figure 1,contains both coded and non-coded information about the process to be controlled and it can be read by other engineers who prepare the block diagrams 20 and schematic diagrams 40.

As shown in Figure 1, each input sheet is divided into a matrix of seven columns and twenty-five rows, the columns being lettered A-G and rows being numbered 1-25. Alternate columns A,C, etc are allocated for interconnecting lines as are alternate rows 1,3,5 etc. The other columns and rows are allocated for symbols and text. The symbol blocks will be defined by a short code, for example: D = Decision Block = = I/O Block The above blocks have five lines of digit positions as shown in Figure 3. These lines are: Line 1 (a) Top Left: Which is ##o digits long and is used to define the block type and its number of outputs.

e.g. D2 i.e. A Decision block with two outputs.

(b) Top right: Which is allocated for the bit number and is four digits long.

Line 2,3 & 4:Which are for the text inside the block.

The amount of text permissible on these lines is governed by the numbers stamped on the symbol stencil.

Line 5: Which is for output destination - i.e. 3 outputs of 3 digits each e.g. B22, C 18 etc.

This will enable the computer to check that all the outputs from the particular blocks are connected to correct inputs.

It may be necessary to go via many blocks to read a particular destination.

The method for preparing input sheets for the wiring block diagram 20 has been based on work carried out on the 'user' aspects of the system. The writing programs and the production of supporting documentation will suit the computer system employed. The following description of the proposed procedure makes certain assumptions for an exemplary system.

A library of symbols is first established. This will cover all the commonly-used symbols used within a manufacturing company for illustrating electrical and instrumentation control systems. The library is extendable to cater for the inclusions at later dates, of new or revised symbols. These symbols are stored by the computer in a suitable form and are addressable by a Library Reference (LR) number, unique to each symbol. These LR numbers will also appear on an index of symbols, available for reference purposes to the electrical and instrumentation engineers.

At the commencement of each particular project, the electrical and instrumentation engineers will develop a shortened version of the library. This shortened library covers only those symbols likely to be required for that particular project but is extendable to cover unforeseen requirements which might emerge during the engineering design. The chosen symbols are given a short aphanumeric device code which is cross referenced to the LR number on a short code specification sheet and entered into the computer. Thus the computer recognises each device code as a symbol from the library. Several device codes may correspond to the same LR number (and have the same symbol). This facility will enable the subsequent production of detailed schedules of devices.

Supplementary information relating to the devices may also be entered into the computer via the short-code specification sheet e.g. the engineer may wish to define three pushbutton units in the following manner: Sec. Drg. Short Description Type Library Index Code Ref PB1 Start/Stop-Lock AB LRS/01/10 Weatherproof Enclosure PB2 Start/Stop-Lock, Flame, BC LRS/01/10 proof Enclosure PB3 Start/Stop, Desk Mounting CD LRS/01/07 Note that PB1 and PB2 have the same LR number, i.e. the same symbol applies to each type but the descriptions differ so that the two types can be separately scheduled.

The amount of detail encompassed by the description is in accordance with the information available at the beginning of a project. Cables are considered to be "components", the various cable-forms being part of the library of symbols.

Having established a relatively short project library, the engineer is now able to call up symbols by means of a short device code and ask the computer to plot that symbol. Thus each wiring block diagram can be produced, provided that the relative positions of the devices are defined and the identification of cable cores, terminals etc is entered into the computer. Data is entered into the computer by a teletype operator on a question and answer bases i.e. the computer will question the operator about the wiring block diagram content, the answers being obtained from the input sheet. The completed sheet contains both coded and non-coded information about the wiring block diagram layout, content, equipment and cable identification and terminal and ferrule numbering.It will be in a form which is recognisable as a wiring block diagram and can be read by the engineers developing and checking the diagram.

As shown in Figure 2, each input sheet, two sheets being used for each block circuit diagram, is divided into a matrix of six rows and seven columns, plus a remarks column. The rows are numbered 1 to 6 or 7 to 12 and the columns identified by a letter A to G. Column A is at the right of the input sheet, after the remarks column. The two sheets at Figures 4 and 5 are used in order to keep the wiring block diagram 20 to a manageable size for desk top work. Each part (sheets 1 and 2) is of A2 size and corresponds to rows 1 to 6 and 7 to 12 respectively of the wiring block diagram 20. Thus, the effective input sheet for each wiring block diagram 20 is based on 12 rows corresponding with the blocks 22 in Figure 6.Each of the sheets has a facility for a signature and a date against each stage of the production i.e. completion of effective input sheet, checking the effective input sheet by electrical and instrumentation personnel and entry of data into the computer. All revisions on the individual sheets are recorded on sheet 1. The procedure for revising the input sheet will be described in due course.

Column A blocks correspond to the input/output units on the wiring block diagram 20. Within each block on the input sheet are spaces for entry of data by the engineer to define the requirements of the input/output unit namely: Three lines of eighteen digits (Maximum) for input/output duty to be reproduced on the wiring block diagram, plus two lines of sixteen digits to be reproduced and one line for the completion of the library reference.

Bottom line of four digits for the bit number to be reproduced and bottom line of five digits for the rack location to be reproduced on the wiring block diagram.

Five terminal blocks for terminal numbers to be reproduced on the wiring block diagram.

Thus by completing an input/output block on the input sheet, the engineer has provided sufficient information about the requirements for the input/output unit to enable the teletype operator to respond to the questions which the computer will ask.

The blocks in the remaining columns B to G are identical and are used for the definition of the successive circuit elements associated with each input/output unit.

At the top of each block on the individual input sheets are three lines of thirteen digit (Maximum capacity positions). On the first two lines the engineer enters descriptive text or legend which he requires to be reproduced above each symbol on the wiring block diagram. This could include the secondary drawing number and short code reference, for instruments the loop reference number would be prefixed with the word "loop". On the third line he enters the register number or cable number for each circuit element. This number is reproduced on the wiring block diagram and also stored by the computer as part of the data for subsequent production of schedules and secondary drawings.

Below the three lines is a space in which the engineer can draw a freehand sketch of the circuit element required. This sketch does not form part of the data input and is simply an aid to reading the input sheet.

Alongside the sketch the engineer enters the device code for the required symbol and it is this which will be entered into the computer.

Flanking the blank space at each side of the block are spaces for entry of up to five ferrule or terminal numbers.

Thus, when complete, each block contains data defining the circuit element type and symbol, legend, register or cable number and terminal or ferrule identification. The relative position of the circuit elements is defined by the "addresses" of the input sheet blocks.

To develop a circuit the engineer completes an input/output block and then completes the subsequent circuit element blocks in the same row of the input sheet for as many circuit elements as are required.

Definition of cable connections to terminals is achieved by lining up the terminal and ferrule numbers on the adjacent blocks. The computer has the facility to move the symbols on the vertical plane to line up the complete circuit.

The number of blocks on each row of the input sheet has been chosen to correspond to the number of circuit elements which can be accommodated on one row of the wiring block diagram, given that each element is of average size. From time to time, situations will arise when a circuit is too "long" to be defined on one row of the input sheet i.e. it will have in excess of six elements (excluding the input/output unit). This could correspond to one of two situations on the wiring block diagram.

(1) The elements of the circuit are all fairly small and although they number more than six they can still be accommodated on one row of the wiring block diagram.

(2) The elements are of average or larger than average size and will not fit on one row of the wiring block diagram.

In both cases the engineer must complete the right to left circuit by continuing into a second row of the input sheet, working from right to left indicating that this second row is a continuation of the first.

In case (1) the computer plots the circuit on a single row of the wiring block diagram and leaves the next row blank.

In case (2) the computer plots the circuit on two rows, just as the engineer used two rows of the input sheet.

A third case may arise where a circuit comprising of six or less large elements will not fit on one row of the wiring block diagram. The computer will therefore plot on two rows, thereby "wasting" one row. To avoid the situation of having insufficient room on a wiring diagram for the contents of a set of input sheets, it is advisable to leave at least one row of the sheets blank. This will give one row "leeway" for the above situation. It is likely that with experience the engineer will be able to assess the likelihood of the above situation arising as the circuits are developed and adjust the number of circuits on each input sheet accordingly.

Certain circuit elements, e.g. MCC panels will be extended vertically into two or more rows of wiring block diagram. It is necessary that the parts of the symbol in each row line up vertically on the final drawing even though they may not do so on the input sheet. The engineer must indicate to the teletype operator that certain elements are continuations of others by entering the input sheet "address" (row and column identification) of the first element in the space normally used for the register number. (The continuations will not have any legend or register number). The computer recognises certain device codes as being continations and will request the input sheet address of the first element and line up the items accordingly.

Multicore cables shown as several individual groups must be identified as common. They all carry the same cable number but to enable the computer to check that a mistake has not been made by using the same cable twice, the second and subsequent groups must be suffixed A, B etc. This suffix will not be reproduced on the wiring block diagram.

If a ferrule number or terminal number is known and is required to be shown on the wiring block diagram it will be entered into the appropriate location on the input sheet. If it is not known or if (in the case of ferrules) it is to be omitted to save space then a fixed symbol (say X) will be entered at the appropriate location. This defines the fact that an un-numbered terminal or termination is required.

Where less than five cores are used then a fixed symbol 0 will be entered into the unused space on the input sheet.

To produce a link between any terminals on the wiring diagram the short code identification word 'link' shall be included in the input sheet in the space reserved for the free hand sketch. The terminals to be linked shall be identified by the letters L1 and L1, or in the case of two links which are required in one block then L1, L, and L2, L2 would be used.

Equipment such as control desks etc., where many terminal connections are located, shall adopt the following system of identifying its own plant number. This plant number is included on the input sheet and reproduced on the drawing. This number will include the primary drawing number of the drawing on which the first terminal of that rail appeared. The number of terminals allowed on any terminal rail is decided by the engineers and numbered sequentially.

Revisions to the wiring block diagrams 20 are implemented as follows: As a revision becomes necessary, it will be carried out and recorded on the input sheet and the input sheet revision number will be raised by one. At this stage no further entry to the computer will take place, and the drawing revision letter will remain the same. Several input sheet revisions may take place before a re-issue of drawings is required and at that stage the latest revision of the input sheet will be entered into the computer and the wiring block diagram drawing number revision up-dated accordingly.

The computer can reproduce a series of drawings or a range of schedules and/or secondary drawings. A few examples of the documentation which might be retrieved are: (1) Composite cable schedules, combining all the individual schedules onto a single document.

(2) Schedules of devices, listed by device code and identified with register numbers.

(3) Composite drawings of all devices connected to common terminal strips (e.g. desk wiring diagrams).

These secondary drawings will be designated drawings numbers 1000-1999.

It is intended that a series of check lists be produced as an aid to the allocation of register, cable and terminal numbers. As a number is used it will be ticked off the list, thus avoiding the possibility of duplication. The cable check list could also include a core allocation section to enable a check to be kept on the size of multicores, e.g.

80840/26/526 The basic information for production of the cable schedule is in the computer once the wiring block diagram input sheet has been entered. Cable number, route and terminations are defined and the computer allocates cores. Supplementary data input is required for voltage, load current, number of cores, conductor size, route length and cable type. The computer collates the individual groups of multicore cables on each diagram making a single cable schedule entry. When a multicore appears on more than one wiring block diagram, the cable schedule entry is repeated in each case but only those terminations appropriate to the particular diagram is listed on each entry.

For the motor control schematic circuit 40, a library of standard schematics is established and held in store by the computer. At the beginning of a project the engineers will either select those standard schematics they wish to adopt or develop new ones and add these to the library.

Each schematic has a Library Reference Number and by means of a simple input statement the engineer can specify which schematic is to be plotted on each drawing.

Claims (10)

1. Apparatus for selectively reproducing drawings which represent respective processes, or part processes and related instrumentation and control systems with interfaces therebetween, the processes being those of a type with a centralised control, the apparatus comprising a computer which has an address coded store of flow diagram symbols, circuit wiring diagram symbols and schematic circuits of the related instrumentation and control systems and interfaces, and other data relating to cable schedules for said systems, a plotter and/or print-out device being provided for reproducing the stored symbols and data, the computer being programmed to selectively reproduce the stored symbols and data, by the plotter and/or print-out device, such that on a given computer input request a drawing is reproduced in a single sheet format wherein designated areas contain the flow diagram, the wiring diagram showing the respective control/instrumentation interface, the schematic diagram and cable schedule for the respective process or part process.

2. Apparatus according to claim 1 including input sheets which are matrix coded so as to receive thereon the symbols and data relating to the respective flow diagrams and circuit wiring diagrams whereby input data is transferred, with the aid of the matrix coding, to the computer store.

3. Apparatus according to claim 1 or 2 wherein the computer is also programmed so as to reproduce secondary drawings which each illustrate a particular component or components which are in store for reproduction on one or more of said single sheet format drawings.

4. Apparatus according to any one of the preceding claims wherein the computer is programmed to verify, with respect to the flow diagrams, the input/output connections of the wiring circuit diagrams.

5. Apparatus according to any one of the preceding claims wherein the computer is programmed to retrieve information from the store of data of the wiring circuit diagrams so as to assemble some of the data on the cable schedules.

6. A method of selectively reproducing drawings which represent respective processes, or part processes and related instrumentation and control systems with interfaces therebetween, the processes being those of a type with a centralised control, the method being effected by a computer together with a plotter and/or printout device and the method comprising the steps of:: (a) storing address coded data representing flow diagram and circuit wiring diagram symbols; (b) entering said symbols on matrix coded input sheets in the form of flow diagrams and related circuit wiring diagrams of said processes or part processes; (c) transferring the information on the input sheets, with the aid of the matrix coding, to the computer store; (d) storing address coded data representing schematic circuits and information pertaining to cable schedules relating to said flow diagrams and circuit wiring diagrams; (e) programming the computer to reproduce, in a single sheet format for each process or part process, a drawing wherein designated areas contain the flow diagram, the wiring diagram showing the respective control/instrumentation interface, the schematic diagram and the cable schedule for the respective process or part process;;and (f) making an input request or requests to cause the plotter and/or printout device to reproduce the respective single sheet format drawing or drawings.

7. A method according to claim 1 including the step of programming the computer so as to reproduce secondary drawings which each illustrate a particular component or components which are in store for reproduction on one or more of said single sheet format drawings.

8. A method according to claim 6 or 7 including the step of programming the computer to verify, with respect to the flow diagrams, the input/output connections of the wiring circuit diagram.

9. A method according to any one of claims 6-8 including the step of programming the computer to retrieve information from the store of data of the wiring circuit diagrams so as to assemble some of the data on the cable schedules.

10. A method of selectively reproducing drawings which represent respective processes, or part processes and related instrumentation and control systems with interfaces therebetween, the processes being those of a type with a centralised control, the method being effected by a computer together with a plotter and/or printout device and the method being substantially as hereinbefore described with reference to the accompanying drawings.