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Transcript of Interlock-Diagrams
An Interlock Diagram (ILD), has the purpose to represent interlocks and operations in a process installation: LSA+ LICA 2013 LSA- Pos 2014 How can we secure this tank? Interlock-Diagrams
(ILD) Ferry Oostervink How would an ILD look like for
Pump 2014? DCS-screen The logic in an ILD is “positive” logic:
logical “1” = action mentioned in ILD is true.
logical “0” = action mentioned in ILD is NOT true. If the maximum (SA+) is reached we get logical “1” = TRUE, otherwise we get logical “0” = NOT TRUE If the minimum (SA-) is reached we get logical “1” = TRUE, otherwise we get logical “0” = NOT TRUE Input = condition Interlock Diagram Representation ILD through symbolism Output = actions Unambiguous so that different working groups can read and understand these ILD's (production, workshop, engineering,..) .
Independent of realization method (=usage of software or hardware). E.g.: most of the interlocks are programmed in the DCS, but some are in the HIMA-safety control, other are hard wired or in Package Units.
Through standardized symbolism
Independent of language except for some details
Easy and cheap to maintain true = logical “1” = “1”-signal
not true = logical “0” = “0”-signal
To improve the readability of an ILD, the possibilities the operator has to operate certain valves (open/shut- or control) are visualized. E.g. Action:
If LSA- is logical "1" the motor (pump 2014 stops) What and Why? Used Symbolism Example Interlock-Diagrams
(ILD) ? Analogue value from transmitter Push button or switch as hardware-function (Binary, local) Push button or switch as software-function (Binary, on DCS) Contact / end switch / … (Binary)
E.g. contact manometer, tuning fork/vibronic fork … Used symbolism: Inputs (conditions) Inputs (conditions) Outpup (actions) Relay / Permit-contact (Binary) Light / visualization (Binary: ON of OFF) Automatic valve (control valve) (Analogue: continuous control between 0 and 100%)
General: Y = 0% = Valve SHUT; Y = 100% = Valve OPEN Solenoid valve (SCV) (Binary: OPEN or SHUT) Used symbolism : outputs (actions)
An interlock in an ILD is visualized with different symbols and the functioning will be done (principally) with binary (0 or 1) signals : Represitation / symbolism ILD's Left = input(s), right = output
# inputs is not limited (2, 3, 4, …) Truth table: C B A C B A AND-function
Electric analogy: serial circuit OR-function
Electric analogy: parallel circuit Used symbolism : OR-function and AND-function C A or C A Truth table: Negation / inversion / reversal
Analogy: off-contact Used symbolism : Negation C B A Memory function
A memory function is used to activate interlocks for actuators. The signal coming from an interlock goes to the R-port (input) B A C
Each following state is a function of the present state and the input signals
With the simultaneous presence of a “1”-signal on S and R, R has priority.
In ground state comes the output in to the state that is indicated by the black bar. C A C A Impulse (duration = t, in which “t” is a time value)
Time starts when input signal becomes “1” and output immediately becomes “1”. The input may get back “0” or “1”, in both cases, only when time is finished, the output becomes “0”.
“C” will be activated for 5s, each time “A” is activated
Typical usage: creates a continuous signal from a pulse signal . Used symbolism: Timefunction - Impulse C A C A Switch on Delay (duration = t , “t” is a timevalue)
Time starts when input becomes “1”, whereas the output is still “0”. Only after time (t) is finished, the output becomes “1”, if the input is still “1”.
If input is “0”, the output immediately becomes or stays “0”.
“C” will be activated 10s after “A” is activated (and still active), “C” will be deactivated as soon as “A” is deactivated
Typical usage: Delay of a switch point that shows up with fast reacting variables. (e.g. Tuning fork / vibration fork before a pump). Used symbolism: Time function – Switch on Delay C A C A Switch off delay (duration = t , “t” is a timevalue)
If input is “1”, the output immediately becomes “1”.
Time (t) starts when the input is changed from “1” to “0”, while the output stays “1” until time is finished .
“C” will be activated as soon as “A” is activated, when “A” is deactivated it takes 10s for “C” to deactivate
Typical usage: Delay of one or several signals by simultaneous fall-out. (e.g. when tuning fork is off after it was on, then it takes some time (t) before you can start the pump) Used symbolism: Time function – Switch off delay Valve control block for an open/shut valve (SCV). MAN-FIX = open/shut-valve can be operated “open” or “shut” by operator as long as the interlock-input (R-port) = “0”. (no interlock)
As soon as the interlock-input (R-port) = “1” (interlock triggered) then the open/shut valve is going to its safety position (e.g. shut). Used symbolism: Open/shut valve controlmode MAN-FIX Valve control block for an open/shut valve AUT-FIX = open/shut-valve can NOT be operated by operator.
The open/shut-valve is always operated automatically open or shut (e.g. from DCS interlock), as long as the interlock-input (R-port) = “0” (no interlock).
As soon as the interlock-input (R-port) = “1” (interlock triggered) then the open/shut-valve is going to its safety position (e.g. shut). Used symbolism: Open/shut valve controlmode AUT-FIX Valve control block for an open/shut valve AUT-S/MAN-S = open/shut-valve can be operated by operator open or shut as long as there are no signals coming from e.g. DCS interlock control to set the valve to automatic.
The open/shut-valve can only be operated as long as the interlock input (R-port) = “0” (no interlock).
As soon as the interlock input (R-port) =“1” (interlock triggered) then the open/shut valve is going to its safety position (e.g. shut). Used symbolism: Open/shut valve controlmode AUT-S/MAN-S MAN-FIX = motor can be started/stopped by operator as long as the interlock input (R-port) = “0” (no interlock).
As soon as the interlock input (R-port) = “1” then the motor is going to its safety position and will be stopped automatically (interlocked). Motor control block. Used symbolism: Motor control mode MAN-FIX Control block for a control valve. AUT/MAN = Controller can work automatically or can be operated by operator on manual, as long as the interlock input (VER) = “0”.
As soon as the interlock input = “1” then the controller is going in MAN-VER mode and the valve is forced to go to its safety position Ey (e.g. 0%; 100%, or in between). This forced position cannot be changed by an operator. Used symbolism: Controller (PID) control mode AUT/MAN
Safety positions of automatic open/shut actors (control valves) is described in ILD after “Sicherheitsstellung: =” = "Safety Position"
e.g.: Centre: representation In ILD ‘s stands the logic part that is programmed in HIMA always at the bottom mentioned with: “Veiligheidssturing”.
This will not say that it is always a Z-function!
The HIMA also contains interlocks that don’t belong to Z-functions. These are interlocks that require a higher safety standard (e.g. level limit security or temperature limit protection for particular pumps according to the law ) In case it is a Z-function, it will be mentioned on FUP with a Z-symbol in a triangle.
= Equipment safety through EMR-technical measures. Logical programmed in HIMA: Z-functions and others ? Questions Any Thank you for your attention Used symbolism: Memory function Used symbolism: Safety position 0 0 0 0 0 1 1 0 0 0 1 1 Permit on 1 After start pulse Pump on 1 1 0 0 0 No Permit = Pump Off 1 1 1 0 Pump Off What would happen when LSA- is on? What would happen when none of these switch points is reached?