We have two FT pair of CP60s installed in our operating units and in both
cases the Fieldbus has caused us numerous headaches until we figured out
the correct installation. In fact we are still having some problems. We
thought the coax ethernet cabling would be easy, but we discovered
otherwise. We have seen a lot of problems similar to yours. The coax
ethernet installation is very different from the previous Fieldbus cabling.
Basis our experience, the way the terminators were installed or connection
problems, is our best guess as to the source of your problem. Here is
what some of what we have learned the hard way:
1. Don't branch (split) the coax ethernet signal with tees. Wire in a
serial path - go in one leg of a FBI10E and then out the other (every
FBI10E has 2 cables). Put a terminator only at the end of the serially
wired leg. There should be only a total of 2 terminators on each coax
Fieldbus (A/B) segment - one is probably at the CP end and the other is
probably at the field (FBM) end.
2. If you are using coax to fiber media converters, the BNC connection at
each of the media converters has to be terminated. In our case using the
Black Box media converters provided by Foxboro, we had to put a tee with a
terminator.
3. We have a CP60FT installation that connects via coax to about 17 old
style FBMs using 3 pair of FBI10Es (3 different Field8 enclosures). These
have not been a problem after we got the terminators and Fieldbus cabling
installed correctly.
4. We have another CP60FT installation that connects to about 26 old style
FBMs (in an IE32) using a pair of FBI10Es and four 200 series I/O using a
pair of FCMs. A fiber optic segment (using 2 coax to fiber media
converters each) is used in the middle of each of the Fieldbus A & B
cabling. This installation has been a very big headache. Now that we are
cabled serially and have terminators installed in the correct places, we
are still experiencing intermittent Fieldbus B problems (usually only with
the 200 series I/O which is at the end of the leg). We punted on the
problem and called in Foxboro yesterday to look at it, the only thing
noticeably wrong with the installation is that we need a newer rev of
Fieldbus terminators that go on the 200 series I/O back plate. I am not
sure if the new terminators will solve our problem, but I hope so.
One of the early problems with this installation was that we had problems
with some of the FBMs in the IE32 enclosure and it was before we installed
the 200 series I/O segment. The FBMs in the enclosure were originally
split between 2 pair of FBI10Es and they were cabled serially. To solve
the problem, I removed 1 pair of FBI10Es and used local extension cables to
connect the Fieldbus in the upper portion of the cabinet to the lower
portion of the cabinet. Once we added the 200 series I/O then we had a new
set of problems.
5. Is your Fieldbus properly terminated within your I/O rack/enclosure.
If it is not properly terminated, you are more apt to have a problem with
the new Fieldbus than you previously did with the older slower one.
6. A bad coax terminator or tee could cause the problem. I have heard of
a few problems with the FBI10E heads - I guess the cables might get
strained.
7. Depending on your available slots, the number of FBMs involved, and the
number of different remote Fieldbus connections involved, I have found that
you can keep the old Fieldbus intact on the back end and only convert the
front end (CP end) by using both a Fieldbus Isolator and a FBI10E. For
instance, you can take a I/O rack and put an FBI10E in slot 1 and a FBI in
slot 2. Wire the FBI10E to your CP60 and wire your FBI to the old style
FBMs with the old style Fieldbus cabling. Even if Foxboro supported this
arrangement, they would probably tell you not to have communications for
more than 21 FBMs going through a single FBI.
I hope there is something in this list that can help you.
Campbell John C
<[EMAIL PROTECTED]> To: "Foxboro Casandra
(E-mail)"
Sent by:
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<[EMAIL PROTECTED] cc:
oject.org> Subject: CP30 to CP60
upgrade
05/03/01 07:44 AM
Please respond to "Foxboro
DCS Mail List"
We are currently upgrading one of our sites from a CP30FT to a CP60FT and
are experiencing some difficulties. The actual upgrade went relatively
smoothly but after the AW was placed back on line with the new CP60's we
started to receive numerous fieldbus failure alarms (PIOBUS A/B) that would
randomly come in and out. Sometimes we would have no alarms for about 1/2
hour and then continuous alarms for the next 20 minutes. There was no
pattern as to when the alarms would occur. Occasionally when the alarms
occurred we would lose communication to the fieldbus altogether (blue flu
on
the operator screen). Until we do some more detail investigations (with
Fox
Mass.) we have gone back to the old CP30 system.
Has anyone else experienced similar problems and what did you do to get
around it.
Some back ground information: The switchover is being performed at the
same
time as a revision upgrade from 6.1 to 6.2.1 on a AW/WP51B system. All
fieldbus modules are of the traditional rack mounted type (no din rail
mounted modules).
Much appreciation for any assistance.
John Campbell
Dofasco
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