These are very intresting topic. Please read it and let me know your queries.
Video Surveillance Joins Forces with HMI/SCADA
It is going to be more exploring track for DCS system as now VMware is also a very good medium in DCS. This post seems to very intresting to me.
Please read this and let me know for any queries.
Carl’s pet peeve number three*: Ethernet is not a protocol.
IMS Research found that the number one industrial Ethernet protocol is “Ethernet TCP/IP.” [“Double Your Pleasure, Double Your PROFINET”]
VDC found the leading industrial Ethernet protocol is “Ethernet.”
Ethernet is not a protocol! I ranted about this before, way back in 2006: “Why Use Industrial Ethernet?” So today I’ve counted to ten and will move from rant mode to education mode.
Networking is characterized in the ISO/OSI reference model. Its seven layers define the functions of various aspects of networks. Wikipedia has a complete explanation: OSI Model. The Internet Model collapses the layers to four.
Layers 1 and 2 are defined by IEEE802.3 which we know as “Ethernet.” To overstate this: Ethernet is just the Physical layer and the Data Link layer. By itself Ethernet does nothing; it’s just the “pipe.” What comes down the pipe? Whatever IP sends down the pipe (when TCP/IP is used). IP is at layer 3. IP sends the message it received up to layer 4, TCP. So what do TCP and IP do? Just send the message on to where they’re told. Up at the top of the stack is the application layer, at layer 7. The application layer is where the protocol resides. Only the application layer actually does more than send the message along its way. (What happened to layers 5 and 6? They are neither needed nor used.)
Now, IP and TCP are not the only choices for layers 3 and 4, respectively. You can substitute UDP at layer 4 for example. Or you can skip them altogether like Address Resolution Protocol (ARP) does; it goes straight from layer 2 to an application.
PROFINET takes a lesson from ARP. It skips TCP and IP for real-time messages. TCP and IP (aka “the stack”) is implemented in software. Rather than let PROFINET real-time messages languish in the stack, we skip it. This improves speed and determinism. (See the Industrial Ethernet Book article for details: “Technical Article: Performance metrics for Industrial Ethernet”.)
So, when users respond to IMS and VDC and say their Industrial Ethernet protocol is “Ethernet,” what do they mean? I would not accept this answer if I were a market research company! So what do they mean? Do they mean web server? A real Industrial Ethernet protocol? A Proprietary protocol? “I have no blooming idea what a protocol is?”
What do you think they mean?
*Number one: Wireless is not monolithic: “Wireless or Wireless”
Number two: Why can’t Control Engineers and IT get along? (Although there is certainly improvement in this relationship from five years ago.)
There are two fails which are widely known in safety system. The first one is called a nuisance fail which does not put the plant system in danger. In fact some nuisance fails will result in spurious trip or unnecessary plant shutdown therefore they cost high as the production stops. The second one is fail danger which is undetected and does not cause a process shutdown. However, if there is an emergency demand, the safety system would be unable to respond properly therefore putting the plant system in danger.
Fail danger frequently occurs on the final elements i.e. actuated valve. One of several causes that make the actuated valve does not work properly upon demand is a failure on its solenoid valve (solenoid valve), either the solenoid coil or the valve. Dirt causes the solenoid valve to stick thus solenoid valve can not change state and unable to respond to emergency shutdown signal.
As mentioned earlier this situation is undetected, however the problem can be resolved by periodic maintenance which does not require shutting down the plant or actuated the main valve.
The following are design and accessories required to enable online testing of solenoid valve.
*Five-way valve shall be key protected to avoid unauthorized testing
During normal plant operation, the solenoid valve is energized, letting the pilot air flow through the solenoid valve, then it passes through the five-way valve and finally pilots the pneumatic pilot valve resulting the air supply is able to reach the actuator. In the meantime, pressure switch is also pressurized by pilot air.
When it is required to test the solenoid valve, five-way valve must be operated by key and hold until test is completed. In this condition, the solenoid valve is bypassed meanwhile the pressure switch is losing its pressure. When the pressure switch reaches its low set point, it signals the control room that the testing is in progress. Now the solenoid valve can be tested without affecting the main valve since the pilot air remains able to reach the pneumatic pilot valve and keeps the main valve in operating condition. By reading pressure gauge, check that solenoid valve is able to respond to emergency shutdown signal and changes its state).
Releasing the key will put the system into normal plant operation
*The purpose of installing a pressure swicth low is to avoid missoperation of
key operated override valve during plant normal operation.