What is the norm / rule for setting a response time for an Electronic Over speed Detection system in a governor control a Steam turbine- Compressor system. A Woodward system with Protec 203 system in place. Is it advisable to use the signals from this PLC be directed to ESD system for the tripping? scan time for ESD system being 300 mili second.

 

Karthick... when Woodward first used our Smart-A-Larm modules in conjunction with their Over-Speed Detector, the delay was intentionaly set for 100ms!

Since the system is 2of3, the actual delay should be the time interval between detection of the the 1st detector and the 2nd detector plus 100ms added by our module.

Not so incidentally, Woodward only bought one set and then introduced their "own" version!

Regards, Phil Corso

 

Thanks for the reply. But I am trying to find a guideline on the maximum allowed response time required by an overspeed detection system to trip the governor. API 670 states it to be 40 millisec, is that industry standards or have you seen deviations from it.

Regards,
Karthik

 

Hi Karthik,

Please be aware that Standard API670 5th Edition is soon to be released and new requirements will require you to calculate how fast your total turbine overspeed system must respond to safely shutdown your turbine. It will also require that you periodically test and validate that your total system's response (overspeed occurrence to final element closed) is fast enough to safely shutdown your turbine. In this new edition we provided the related equations in a normative Annex ("O"). Alternatively you should be able to ask the turbine OEM to provide you the total required shutdown period allowed to safely shutdown your machine. Please note that API defines the time required to safely shutdown your turbine as the period of time after a complete loss of load to shutoff steam flow to keep rotor speed below 127% of rated turbine speed.

Regards,
Rich Kamphaus
Woodward Steam Turbine Control PLM
API670 Re-write team..

 

Hi Karthik,

Please be aware that Standard API670 5th Edition is soon to be released and new requirements will require you to calculate how fast your total turbine overspeed system must respond to safely shutdown your turbine. It will also require that you periodically test and validate that your total system's response (overspeed occurrence to final element closed) is fast enough to safely shutdown your turbine. In this new edition we provided the related equations in a normative Annex ("O"). Alternatively you should be able to ask the turbine OEM to provide you the total required shutdown period allowed to safely shutdown your machine. Please note that API defines the time required to safely shutdown your turbine as the period of time after a complete loss of load to shutoff steam flow to keep rotor speed below 127% of rated turbine speed.

Regards,
Rich Kamphaus
Woodward Steam Turbine Control PLM
API670 Re-write team..

Dear Rick,
Could you please let me know why API-670 stipulates that Independent probe system with triple redundancy should be used fro governing and over speed system. Since we have 3 MPUs installed in our Mark 5 connected with 3 main processor core and 1 protection core. Why do we need extra 3 probes to make it API complaint, sine we can jump over for both governing as well as overspeed system.

Regards,
Waqar Ahmad
Machinery Engineer
Engro Fertilizer

 

Dear Rick,
Could you please let me know why API-670 stipulates that Independent probe system with triple redundancy should be used fro governing and over speed system. Since we have 3 MPUs installed in our Mark 5 connected with 3 main processor core and 1 protection core. Why do we need extra 3 probes to make it API complaint, sine we can jump over for both governing as well as overspeed system.

Regards,
Waqar Ahmad
Machinery Engineer
Engro Fertilizer

 

Since MKV, Control & Protection were made totally separate to comply with various regulations. This means that the speed control & Overspeed Protection pickups need to be separate