I have one issue in 3500 BN system installed in power plant with Mark V control Turbine.

When I open MARK V HMI, I found one of thrust vibration alarmed (Yellow), but in corresponding BN 3500 rack there is no alarm (led are green).

Some time this thrust reach danger, but no trip happen, after all. when I check in configuration, there is no by pass.

Please advice me

 

GE, as a standard practice, does not use the Bently Nevada 3500 equipment for alarming and tripping. The BN equipment is for monitoring only, and, if you have additional BN equipment, it can provide extensive vibration analysis data.

The vibration protective functions are provided by the Mark V. You did not state whether the turbine is gas or steam.

In the case of gas turbines, the alarm and trip functions are derived from seismic sensors connected directly to the Mark V, not proximity probes.

In the case of steam turbines, the proximity probes are connected directly to the Mark V, and it provides the machine protective functions.

In either case, you do need to determine whether there is a problem with the turbine or a problem with the thrust position sensors.

 

djafer,

Thrust is not vibration, though both can be measured using proximity probes. The difference is that when measuring vibration the proximity probe looks at the shaft and when looking at thrust the proximity probe looks at a thrust bearing "runner" (usually). When measuring vibration the B-N Monitor needs to know shaft speed to calculate the displacement; when measuring thrust speed is not necessary to calculate how much the shaft moves axially.

I presume this is either a steam turbine or an F-class gas turbine, because the other GE-design heavy duty gas turbines don't usually monitor thrust in the Mark V. Another thing which is not clear from your post is when you say you "...open MARK V HMI, ..." What exactly do you mean--when you look at the Vibration Display (which is where thrust is usually displayed, even though it's not "vibration") or when you look at the I/O Configurator of the Mark V?

Sometimes the Mark V used buffered inputs (via 4-20 mA inputs, if I recall correctly) to display displacement from B-N proximity probes, and sometimes the calculation of thrust was done on the CIMPLICITY display and not in the Mark V turbine control panel. There was a special "display" function that allowed the display of vibration and thrust--but not to generate turbine trips. In this case, the same probes were used for both the B-N panel and the Mark V; they were kind of like using the same probes "in parallel." If the Mark V doesn't do anything other than accept the buffered inputs from the B-N probes to display them on the HMI, and the thrust measurement/zero reading is not the same as is being done in the B-N rack then there can be a discrepancy. (I make a very clear distinction between the Mark V turbine control panel and the Mark V HMI--there is NOT supposed to be any control or protection done in the HMI, it's only purpose is to view data and alarms and to send commands to the Mark V turbine control panel not to perform any control functions (such as speed control or fuel control) and not to perform any protection functions (like measuring vibration or thrust and generating a trip.)

My best guess from the information provided is that there is some difference in the way the thrust measurement is being done "in the Mark V" versus the way it's being done in the B-N Monitor. Probably the zero setting is not the same or something similar. It's very difficult to say, again, from the information provided. And, about the only way to say for sure what's going on is to shut the unit down and actually move the shaft (using a hydraulic ram) to observe the thrust readings on both the B-N Monitor and the CIMPLICITY display and then try to understand what the difference is, if any.

Again, there were several ways the B-N proximity probe information made it's way into the Mark V--and none of them were very elegant because the Mark V was design before GE assimilated B-N and was allowed to work directly with B-N algorithms and code in the turbine control panel (the way the Mark VI and Mark VIe can do now). It doesn't sound like you know how the "Mark V" is getting the B-N prox probe data and how it's being used (only for display purposes on the HMI, or also for protection purposes in the Mark V turbine control panel). It's very unfortunate but GE didn't document any of the methods they employed for this over the years. I wish I could refer you to the proper manual for more information, but it just doesn't exist.

Even if the proximity probes used for thrust were directly connected to the Mark V and used by the Mark V turbine control panel for protection and trip, the zero and total movement readings would have to be calculated any time the shaft was removed and re-installed for maintenance, or the thrust bearings were removed and re-installed or replaced during maintenance--the same is true for the B-N Monitor thrust probes, as well. The zero and total travel for the shaft must always be measured during reassembly or if thrust bearings were removed/re-installed and/or replaced.

 

Hello;
Many thanks for your help every time.

Just, I give you some information step by step:

When I have observed thrust vibration alarmed Cimplicity, but in BN 3500 RACK no alarm.

I proceed as below:

I click on Start in HMI MAK V
I open BN 3500 system configuration
I connect with BN 3500 Rack
I upload BN 3500 software from BN MONITORING
I click on utility in 3500 system configuration than I select verification. I found one of thrust vibration alarmed, but in BN RACK all are ok (no red led, all are green).

Some time this thrust reach danger, but the turbine not tripped.

NB: This alarm appear in Cimplicity too.

My question is: Why this thrust alarmed in 3500 system configuration and Cimplicity, but in BN 3500 Rack all are ok

I hope my question is clear.

Best Regards

 

Hello,
Once again, I'm confused. I'm not very familiar with B-N software, but I suspect it's a configuration issue--the card can be and has been configured differently than the software used on the HMI, which by the way is very non-standard for GE Mark V HMIs.

Just because a bar-graph turns yellow on a GE HMI display <b>does NOT</b> mean the value is in alarm. There were some extremely poor screen programming practices used for GE Speedtronic HMIs which lead to some very bad misunderstandings. And, again, many times the colors used for bar-graph are NOT tied to actual operating parameters (Control Constants) and so can cause all manner of confusion.

Just because you can access a B-N monitor rack with B-N software installed on a GE Mark V HMI does not make it part of the standard GE Mark V HMI applications. It's pretty unsual, in fact, to have B-N software accessing a B-N rack from a GE Mark V HMI.

And, as was stated before--there's nothing that makes the B-N configuration the same as the GE Mark V HMI configuration. The GE Mark V HMI and the B-N rack can't communicate with each other, and neither can the B-N rack or B-N software communicate with the Mark V turbine control panel. The B-N rack can share inputs with the Mark V turbine control panel, and the values of the inputs can be displayed on CIMPLICITY displays on the GE Mark V HMI. But, they don't share configuration values.

It's really a "legacy" to the time when control systems couldn't take to each other at all, mixed in with the ability for one control system to share inputs, and for an HMI to be able to display values from multiple control systems--but those control systems are still separate, stand-alone control systems (which may also share some discrete logic signals for alarm and tripping).

Wish I had better news for you! Sounds like you've landed on a really unusual Mark V site, mate! Best of luck!

By the way, what does NB: stand for???

 

NB stands for the Latin words nota bene (or something close to that), meaning Note Well.

 

otised,

Latin was omitted from the secondary school curriculum two years before I entered. I was happy at the time; not so happy about that now that I realize how useful it can be for so many things. I've seen a lot of different notations used by operators in logbooks, but never this one.

Thanks!

 

Many thanks;

Your information are very interesting.

NB stands for the Latin words nota bene.

Best Regards

 

If you are accessing a vibration rack by '3500 System Configuration', then you could:

- From 3500 System Configuration.
- load rack configuration file (.rak) from computer.
- Click on Toolbar on connect icon.
- Click on 'verify' from tool pallet, then click on card that you want to know about alarms or trip limit.
- You should be able to see the actual reading and actual setting in bently nevada 3500.

Hope this help,