Here’s an interesting tidbit I picked up during my FS course in Bangkok.
There are two building blocks used in logic programming:
And logic associated with these is:
| Input | Output | |
| A | B | A AND B |
| 0 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
And
| Input | Output | |
| A | B | A OR B |
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 1 |
Now, think in terms of ‘energised’ as Boolean value 1, and ‘non-energised’ as Boolean value 0, then go through the logic of a “de-energise to safe” (DTS) system. Assuming that A and B are sensing elements of a one out of two (1oo2) voting system, then if A or B trip (de-energise), the logic output of an AND gate is 0, i.e. non-energised.
Hence, an AND gate acts as an OR gate in a DTS system. And an OR gate acts like an AND gate.
And Synergy can give you more from where that came from
Wata - Malaysian Oil and Gas Engineer 
I still get ETS and DTS wrong!
How come chemical engineer also have to learn about Gate???
for those that need to do functional safety, you need to do SIL verification calcs (61511/61508), which requires the calculation (derived from Reliability Block Diagram).
agreed with Jabba.. nowadays you need also to know about other disciplines in order to perform better in your own field.. for chemical engineer, one also need to know about piping, mechanical and instrumentation in preparing the works i.e. P&ID, C&EM, etc.
Yah, no matter in what discipline, you must know a bit in other field as well.
DTS = De-energize to Safe is more applicable for those Emergency Shutdown System philosophy which usually used in critical process safety application. It will bring the whole plant/platform into the pre-determined fail safe state in case of any fault happen to the system such as power loss, cable disconnection and etc.
For ETS = Energize to Safe is more applicable to Fire and Gas Application which the activation of the logic output is by voting of Gas/Flame/Heat Detector.
Just my 2 cents…. : )
ah, sheong80 did your TUV FSEng course? seems like that’s the exam answer.
Looking to collect more titles. got my FSEng. the CSP title seems to be cool. thinking of getting that one.
@ sheong80, correct if i’m wrong but judging from your explanation, I would say that you’re working in instrumentation field rather than process or safety.