Hi everyone,

At our plant we have 3 Nos Frame 9e GTs connected to their respective 3Nos HRSGs feeding one ST.
I've query regarding logic of GT trip with HRSG DD closed.

At our plant, logic is that GT trips the moment HRSG trips . i want to know what's the standard procedure applied elsewhere, will GT trip if any HRSG protection operates(Drum Level HH,LL etc)

Secondly will GT continue running run on open cycle if DD shuts down 100% on Normal HRSG shutdown or Emergency trip ?

I''ve read somewhere that GT continue on open cycle if HRSG taken normal shutdown and DD closes 100%, and if there is an emergency shutdown then there is a timer set of 40-50 sec within which DD should shutdown if not then HRSG fault will travel towards GT causing GT to

 

Hi

Best answer can be found on app code or any kind of documents from GEEPE about Matrix tripping diagram

 

there is no matrix tripping diagram actually that's why looking for others to share their experiences. please share any useful document if you have one.. Thanks

 

How about OEM manuals do you have read Operation &Maintenance manual ?

There should be some informations on these documents ,regarding your question

 

I have seen GEEPE Projects with Matrix tripping diagram...
You may ask them if they can provide it.. According to the project..

By the way who is Packager of these units? Ge Belfort.. Nuovo pignon.. Or other..

 

How about OEM manuals do you have read Operation &Maintenance manual ?

There should be some informations on these documents ,regarding your question

its actually installed/commissioned by Chinese Company called Dongfang. Their operation manuals are about its general working i.e., Hydraulic skids, sealing fans, control and general operations. it doesn't say anything about its interlocking with GT tripping...

kindly share your experience/SOP; my question is:
1. will GT run on open cycle if we undergo normal HRSG shutdown and Diverter Damper closes 100% under normal conditions ?
2. What happens if HRSG trips under some protection, will it cause GT to trip also or is there some timer set within which DD should close to avoid GT tripping.
3. if there is a timer set by I&C team then What happens if HRSG trips and DD doesnt close within that time frame ?

 

I have seen GEEPE Projects with Matrix tripping diagram...
You may ask them if they can provide it.. According to the project..

By the way who is Packager of these units? Ge Belfort.. Nuovo pignon.. Or other..

This project is long before handed over to us and O&M manuals were shared later but these manuals doesnt state anything about GT interlocking with HRSG tripping.

 

My advise will be to review app code see which signal name or case will trip GT /ST..

 

Typically, if some HRSG protection encounters a condition that warrants an HRSG trip condition (low-low drum level; high-high drum level; loss of boiler feedwater pump or feedwater flow; etc.) the HRSG should be tripped because exhaust will continue to go into the HRSG which would lead to very serious consequences for the HRSG and/or the steam turbine (carryover). And, most diverter dampers are very large and can't close quickly enough to prevent the exhaust heat from getting into the HRSG to avoid some kind of catastrophe.

Typically, the HRSG manufacturer defines how the HRSG is to be protected--remember, at least when the HRSG is new it is covered under warranty by the manufacturer and so they want it be protected as best as possible. The construction of the HRSG and the materials used in the construction of the HRSG will affect the decision about how long an HRSG might be able to continue with exhaust heat in some kind of emergency. And, if a low-low or high-high drum level is the cause of a trip they are usually each preceded by an alarm (low drum level or high drum level) and the operator should be taking some kind of action to determine if they need to close the diverter damper or lower load (exhaust heat), etc., before the trip level is reached. So, there's usually some time that has passed before the trip is actually initiated.

Most combined cycle power plants have operations manuals that describe how the plant is designed to be operated (including protection). Unfortunately, many plants don't make those manuals available to plant personnel to study and learn from.... I suggest you start with those manuals (NOT the GT manuals) and if the HRSG manufacturer/supplier provided manuals they probably have something in there that can be used to understand how the equipment was designed to be operated and protected.

At the combined cycle power plants I have worked at equipped with diverter dampers the gas turbines are designed to continue operating in simple cycle (open cycle) if an operator or condition closes the diverter damper (NOT a trip condition). BUT, the diverter damper usually has a time limit in which it must reach the fully closed (100% closed) condition OR the unit will trip. AND, at most of the combined cycle plants equipped with diverter dampers the damper mechanism is usually pretty "frail" and doesn't get the require maintenance and will not close fully within the prescribed time, resulting in a GT and/or HRSG trip. (Lack of ubrication of the mechanism/actuator is usually the main cause of this, as well as the design of the diverter damper causes it to "twist" during opening and closing when the GT is running and exhausting into the HRSG which can cause it to get stuck. Also, internal plates on the side of transition piece where the diverter damper moves can loosen and cause the door to get stuck in one position. This results in a lot of operational problems when trying to close (or even open) the diveter damper when the GT is running.

If you are experiencing a number of what you feel are "nuisance" trips of the HRSG/GT due to diverter damper issues, the best course of action is to examine why the trips are occurring and work to resolve them (root cause analysis) instead of trying to understand if the unit should be tripping when this or that condition occurs. That switched the emphasis to reliability--which is (or should be) the real reason for the efforts--not understanding if it should or shouldn't trip.

Again, the HRSG manufacturer/supplier usually defines when the HRSG should trip, and that information is provided to the GT supplier to help in protecting the HRSG (by shutting off the flow of exhaust heat, by tripping the GT if necessary). BUT, the parameters for the equipment at YOUR site should be the ultimate arbiter of how the equipment at YOUR site should be working. And, if it's not working as intended and that can be resolved with better sensors and operating procedures to improve reliability and availability of the equipment that should be the ultimate focus with the efforts directed to those ends (improving reliability and availability).

And if your efforts and discovery reveals that it's the tripping scheme that is at fault (the sensors are all working and calibrated properly and the diverter damper mechanism/actuator is working properly (when the GT is running and when it's not running), then you can certainly ask the GT and HRSG suppliers--and possibly the plant architect/engineer/designer--to get involved with improving reliability and availability.

Seriously, though, diverter dampers are typically very weak links in combined cycle plant operation (as weak as the water treatment facility/method, and any natural gas compressors). I have gone to sites where the diverter damper mechanism/actuator cables had snapped, the motor operator had burned out (it's pretty hot usually where the motor is located), the door has too much flex and twists while opening and closing--especially when the GT is running, and limit switches just wouldn't last in the heat and were also poorly mounted (cheaply and almost as an after-thought instead of as the critical sensor(s) it(they) are). If your diverter damper is unreliable, look into the reasons for that and work to resolve that issue (or those issues--it's often a combination of two or more things).

We would appreciate hearing back about how your are working through the issue(s) to improve reliability and availability.

 

hassan.faraz123...
Welcome to Control.com.
Short Story. One Plant I worked in called their "HRSG" a "Flue Gas Cooler" to avoid paying Energy Taxes. The Authorities of the country in which it was located issued a heavy fine instead!
The Limit-Switch wiring issue was solved using MI (Mineral Insulated) Cable!
Regards, Phil Corso

 

Typically, if some HRSG protection encounters a condition that warrants an HRSG trip condition (low-low drum level; high-high drum level; loss of boiler feedwater pump or feedwater flow; etc.) the HRSG should be tripped because exhaust will continue to go into the HRSG which would lead to very serious consequences for the HRSG and/or the steam turbine (carryover). And, most diverter dampers are very large and can't close quickly enough to prevent the exhaust heat from getting into the HRSG to avoid some kind of catastrophe.

Typically, the HRSG manufacturer defines how the HRSG is to be protected--remember, at least when the HRSG is new it is covered under warranty by the manufacturer and so they want it be protected as best as possible. The construction of the HRSG and the materials used in the construction of the HRSG will affect the decision about how long an HRSG might be able to continue with exhaust heat in some kind of emergency. And, if a low-low or high-high drum level is the cause of a trip they are usually each preceded by an alarm (low drum level or high drum level) and the operator should be taking some kind of action to determine if they need to close the diverter damper or lower load (exhaust heat), etc., before the trip level is reached. So, there's usually some time that has passed before the trip is actually initiated.

Most combined cycle power plants have operations manuals that describe how the plant is designed to be operated (including protection). Unfortunately, many plants don't make those manuals available to plant personnel to study and learn from.... I suggest you start with those manuals (NOT the GT manuals) and if the HRSG manufacturer/supplier provided manuals they probably have something in there that can be used to understand how the equipment was designed to be operated and protected.

At the combined cycle power plants I have worked at equipped with diverter dampers the gas turbines are designed to continue operating in simple cycle (open cycle) if an operator or condition closes the diverter damper (NOT a trip condition). BUT, the diverter damper usually has a time limit in which it must reach the fully closed (100% closed) condition OR the unit will trip. AND, at most of the combined cycle plants equipped with diverter dampers the damper mechanism is usually pretty "frail" and doesn't get the require maintenance and will not close fully within the prescribed time, resulting in a GT and/or HRSG trip. (Lack of ubrication of the mechanism/actuator is usually the main cause of this, as well as the design of the diverter damper causes it to "twist" during opening and closing when the GT is running and exhausting into the HRSG which can cause it to get stuck. Also, internal plates on the side of transition piece where the diverter damper moves can loosen and cause the door to get stuck in one position. This results in a lot of operational problems when trying to close (or even open) the diveter damper when the GT is running.

If you are experiencing a number of what you feel are "nuisance" trips of the HRSG/GT due to diverter damper issues, the best course of action is to examine why the trips are occurring and work to resolve them (root cause analysis) instead of trying to understand if the unit should be tripping when this or that condition occurs. That switched the emphasis to reliability--which is (or should be) the real reason for the efforts--not understanding if it should or shouldn't trip.

Again, the HRSG manufacturer/supplier usually defines when the HRSG should trip, and that information is provided to the GT supplier to help in protecting the HRSG (by shutting off the flow of exhaust heat, by tripping the GT if necessary). BUT, the parameters for the equipment at YOUR site should be the ultimate arbiter of how the equipment at YOUR site should be working. And, if it's not working as intended and that can be resolved with better sensors and operating procedures to improve reliability and availability of the equipment that should be the ultimate focus with the efforts directed to those ends (improving reliability and availability).

And if your efforts and discovery reveals that it's the tripping scheme that is at fault (the sensors are all working and calibrated properly and the diverter damper mechanism/actuator is working properly (when the GT is running and when it's not running), then you can certainly ask the GT and HRSG suppliers--and possibly the plant architect/engineer/designer--to get involved with improving reliability and availability.

Seriously, though, diverter dampers are typically very weak links in combined cycle plant operation (as weak as the water treatment facility/method, and any natural gas compressors). I have gone to sites where the diverter damper mechanism/actuator cables had snapped, the motor operator had burned out (it's pretty hot usually where the motor is located), the door has too much flex and twists while opening and closing--especially when the GT is running, and limit switches just wouldn't last in the heat and were also poorly mounted (cheaply and almost as an after-thought instead of as the critical sensor(s) it(they) are). If your diverter damper is unreliable, look into the reasons for that and work to resolve that issue (or those issues--it's often a combination of two or more things).

We would appreciate hearing back about how your are working through the issue(s) to improve reliability and availability.

Thanks for your detailed answer and sorry for late reply. I checked with other Control Room Operators and they shared their experience that here at our plant, GT gets trip command as soon as HRSG is tripped due to some abnormal condition (as you mentioned Drum Level HH etc). Actually at our plant, main contractor is Chinese Team and most of the time spare aren't available from their end to our Maintenance team for proper operation of Diverter Damper and if available are of poor quality. As a result our IC Engineers have forced alot of Logics and limits including limits of HP Pumps and Diverter Dampers to male the system work...&Manuals aren't maintained, trips points are forced to their limits. Sometimes our DD remains open even if GT is standstill, because of its opening closing issue during startups. I cross checked with my IC Engineer and they also confirmed that time limit within which DD should close under tripping condition is not commissioned at our plant meaning GT initiates trip command as soon as HRSG trips

I got your point that as per standard procedure damper should close and GT should continue running on Open Cycle.

 

My point about the GT continuing to run should the diverter damper close is that should happen ONLY when an operator initiates a damper closing while the machine is running. If there's an HRSG trip, then probably the GT should not continue to run. But, if there's a Drum Level High alarm and an operator decides to close the diverter damper IF THE DAMPER MECHANISM/ACTUATOR IS WORKING CORRECTLY then it's likely the GT should continue to run. IF THAT'S THE WAY THE PLANT WAS DESIGNED TO OPERATE.

What's happening with Chinese-engineered power plants right now is like what happened 50 years ago with Japanese equipment and engineering. It was not very good, but the Japanese worked VERY hard to learn from their mistakes and make quality a top priority. That was hard in the Japanese culture--a culture of decisions by committee. There were LOTS of opinions but one thing everyone agreed on was: Quality was the key to success. Full stop. Period. Designs were quickly changed and equipment improved very fast.

It remains to be seen if the Chinese will come to that realization. I watched as 10-inch steam piping was welded to a 100 meter long pipe rack during installation with no expansion capability. When steam was admitted to the piping for blow-down, the welds popped and piping buckled very quickly. The next day the piping was welded in place again. And when steam was readmitted, the same thing happened. That was 30 years ago. The heavy fuel oil for the GTs was also heated and the heavy fuel oil piping was installed it had no expansion capability and was also welded in place.... AND it had no vents for removing air in the piping....

Best of luck!

 

Better if GT not trip if Damper closed. This will save some load on simple cycle mode. GT should trip if hrsg/stg trip but damper still open/fail to close after time delay. On some Plant, protection such as level high high /low low is handled by safety guarding system and have coordination IO with GT controller