Bailey CIU terminations and network Q's?


Thread Starter


Im looking for some answers to some CIU Q's.

Back ground info.

we have areas in our plant that utilize 2 redundant pcv servers with a single pcv client for control room monitoring/control. each server has a ciu connection and a bailey network connection, where the client has just the network connection.

Now the q's.

What is the purpose of the ciu connection?

With the ciu connection lost, will the server pull live data?

with the network connection lost, will the live data be lost?

I'm not understanding why i need the ciu connection in this case.
Please leave an email address so i can directly respond to your answers. thanks in advance.
The CIU connection physically connects the PCV Servers to the N90/Infi90 system.

If the CIU connection is lost live data cannot be "pulled" in.
The network connection is used to connect the client to the servers. If this connection is lost then the client becomes a paper weight.

Q. What is the purpose of the ciu connection?

A. The Computer Interface Unit (Acronym of CIU) is as the name suggests: the interface between the Bailey DCS network and the computer containing HMI software, such as PCV in your case. The CIU is specially designed to communicate between the computer and either an ‘Infinet’ if you system is Infi90 or ‘Plant Loop’ if it is the older Network 90 system.

The difference between the two is essentially the network performance, where Infinet transmits / receives 32 bit msg pkts at the rate of 10 MHz and the older Plant Loop does the same with 16 bit pkts at the rate of only 500 KHz.

It is easy to identify what type you have by the CIU modules and the PCU modules.

If you are using Infinet (therefore Infi90 system) you simply look for INNIS01 modules. If Plant Loop: you will see either NLIM02 modules or maybe INLIM03.

These modules are what make it either Infinet (Infi90) or Plant Loop (Network 90).

All other hardware in the system is still the same for either systems.

Q. With the ciu connection lost, will the server pull live data?

A. NO! This is essential, it is the only link between your HMI (or maybe an Engineering Work Station (EWS) You must have at least one server running and connected to a CIU for your HMI (PCV in your example) to work.

Q.with the network connection lost, will the live data be lost?

A. It would be lost on any clients, but would still be okay on a server, providing that server is still connected to the Infinet or Plant Loop (whichever you have) via its CIU.

In your system you have two servers for redundancy. Providing one of the servers is up and running and connected to its CIU your clients will still work. The other server will still pull its live data from the ‘online’ server - that is the one that is connected to the ciu, via the LAN. If you were to break the network connection between the two servers, the clients that are connected to that server (the standby one - the one that is NOT connected to its CIU), would have to be reconnected to the active (CIU connected) server again.
There is no DC or ‘active directory’ with PCV networking, just very simple peer to peer - server / client connections.

Providing one of the servers is connected to a CIU, your clients should all work over the network (LAN). It is normal to have all servers connected and ‘online’ to their CIU’s and if one of the servers or CIU’s fail, there’ll be no loss of data - redundancy...
Note: Only SERVERS are connected to CIU’s. This CIU interfacing is not available in any Bailey HMI client (not just PCV, but any Bailey / ABB HMI).

Way back in the ‘80’s there was no networking - ALL consoles had a CIU. There was no LAN as such until systems such as yours (PCV) were developed and released into the market.

I hope this makes things a bit clearer for you, but if not just reply to this post or my e-mail portert [at] transfieldservices