advertisement
from the DCS opeartions department...
DeltaV Device Control Function Block operation
Continuous process industries, DCS questions. topic
Posted by Oren on 8 December, 2004 - 6:34 pm
Hi,

I have to define a DeltaV System and I am struggling with a few things.

I am trying to figure out the difference between "Interlock", "Shutdown" and "Permissive" of a DC function block. I know TDC very well.

If someone could explain it to me in that (Honeywell) language I would greatly appreciate it.

Is there a priority issue between them? It looks like the interlock and shutdown perform the same function. Is that so? Is there a way to interlock the active state(s)? Is there a way to permit the change to any state? or only to the active1 state?

If anyone knows of a DeltaV related group where I can post my questions it would be also great.

Thanks,
Oren


Posted by Lou on 8 December, 2004 - 11:01 pm
Hi Oren,

This is some explanation for DC Function block parameters I found in my Doc for DeltaV. I hopes it will help you. I think the SHUTDOWN_D is like the RED TAG parameter in Honeywell stuff, but not sure.

CAS_IN_D is the discrete value and status of a setpoint from another block used when the block is in Cascade mode.
SHUTDOWN_D is the Emergency Stop discrete value and status input that forces and holds the device in the Passive
state.

PERMISSIVE_D is the optional discrete input value and status that must be True when the Permissive device option is enabled to allow the device to be commanded to an Active state.

TRK_IN_D is the discrete input value and status that forces the block mode to Local Override and causes the output to follow the field value (FV_D).

SIMULATE_IN_D is the optional discrete input value and status that is used to simulate the field value.

INTERLOCK_D is the optional discrete input value and status that must be True when the Interlock device option is enabled for the device to remain in the Active state.

OUT_D is the discrete output value and status that reflects the current commanded device state.

Lou


Posted by sandeep on 18 January, 2013 - 7:39 am
Sir,
Can you please explain me about field I/O's related to DC function block and how to configure it to DI/DO channels?

thank you


Posted by Ashwini on 20 January, 2013 - 10:06 pm
Sandeep,

DC function blocks allow you to configure upto 4 outputs and 4 inputs -

if you look under parameter-list for this FB - IO_in1, 2, 3,4 and IO-out1 - 4. define the Dsts here.

if you want to bring the IOs in from an external module or FB - use parameters F_IN_D1 - 4 and F_OUT_D1 -4. these first have to be brought out of DC1 for connection to external blocks.

Ensure that your statemask is set up to define the relationship betwn discrete ins and outs.

I would recommend reading through books online more details.


Posted by Dave on 8 December, 2004 - 11:07 pm
I will give it a shot, here is the cut and paste from Delta V online help. The _D just stands for discrete.

SHUTDOWN_D is the Emergency Stop discrete value and status input that forces and holds the device in the Passive state.

PERMISSIVE_D is the optional discrete input value and status that must be True when the Permissive device option is enabled to allow the device to be commanded to an Active state.

INTERLOCK_D is the optional discrete input value and status that must be True when the Interlock device option is enabled for the device to remain in the Active state.

My understanding and usage like most controls a lot of people assume permissives and interlocks are the same, they are not.

You need permissives to start a piece of equipment and the interlocks to keep it running or not. So as an example if the tank level goes high, that might be a permissive to start the pump but of course if it were also an interlock, when the level dropped the pump would shut off (which may be desired). On the other hand it starts and then shuts off on the low level (interlock), or high amps, or a valve closing in the line etc.

In Delta V you need the permissive to start and then once running, it can go away. The interlock(s) must be true to continue running (in an active state as DV refers to it).

The shutdown on the other hand will hold the device off (inactive) until reset by the operator.

Hope this helps and if more is desired...just ask.

Dave
DAVCO Automation


Posted by Oren on 10 December, 2004 - 6:09 pm
Let me see if I got this right:

1. You must have a permissive to operate the acive state. That means that it is ONLY for the active state. There is no permissive for the passive,active2 state?

2. The Interlock action switches the device to the passive state when the value is False? Does it go back to the active state when it becomes true again? Is there an interlock action to switch to the active state?

3. The Shutdown action "forces and holds" the device to the passive state when True. How does that differ from the interlock above? this is acting on True and the other on False?

Is there a priority issue? or all these three action are acting on the same thing to the same direction and therefore there is no need for any?

You mentioned nothing about state2 permissive or interlocks. Do they exist somewhere? and if they do how are they prioritiezed?

Oren


Posted by Dave on 6 January, 2005 - 3:21 pm
Sorry , I have been gone most of the end of last month and am just getting back to catching up. sorry.

> Let me see if I got this right:
>
> 1. You must have a permissive to operate the acive state.
> That means that it is ONLY for the active state. There is no
> permissive for the passive,active2 state? <

Passive is off, active is true example start (active state) command versus stop command (passive state)

Why would you have permissives for the stop, they are just the opossites of start, if you have a permissive to stop, use it in the start as "not-my permissive" to start.

Give me an example of your thinking here, remembering that these are command states, go to active state, passive state, active 2 state etc....(2 state not used very often (as compared to active 1).

> 2. The Interlock action switches the device to the passive
> state when the value is False? Does it go back to the active
> state when it becomes true again? Is there an interlock
> action to switch to the active state? <

It will clear, if you do not want it to clear use the Shutdown.

> 3. The Shutdown action "forces and holds" the device to the
> passive state when True. How does that differ from the
> interlock above? this is acting on True and the other on False? <

This one latches and must be reset by the Operator from a faceplate (reset).

> Is there a priority issue? or all these three action are
> acting on the same thing to the same direction and therefore
> there is no need for any? <

Not that I know of or have seen, if you have them all being used the same you need to learn how to program... no spam intended.

> You mentioned nothing about state2 permissive or interlocks.
> Do they exist somewhere? and if they do how are they prioritiezed? <

Believe these are only for either state, in other words a two speed pump, fast slow still uses the same interlocks etc., of course the interlock, permissive could be "slow speed and permissive" or " fast and permissive", etc.


Posted by Bart Schaminee on 15 February, 2005 - 12:38 am
You can ask it to me.

Call me and I will couple you to one of our very best engineers.

Bart Schaminee
Emerson Process Management
+31-70-14136712.

Your use of this site is subject to the terms and conditions set forth under Legal Notices and the Privacy Policy. Please read those terms and conditions carefully. Subject to the rights expressly reserved to others under Legal Notices, the content of this site and the compilation thereof is © 1999-2014 Nerds in Control, LLC. All rights reserved.

Users of this site are benefiting from open source technologies, including PHP, MySQL and Apache. Be happy.


Fortune
Modern man is the missing link between apes and human beings.
Advertise here
Advertisement
our advertisers
Help keep our servers running...
Patronize our advertisers!
Visit our Post Archive