×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

API 616 overspeed trip setpoint specification

API 616 overspeed trip setpoint specification

API 616 overspeed trip setpoint specification

(OP)
API 616 5.4.4.6 states: An overspeed trip protection shall operate at 105% of maximum continuous speed. Multiple shaft turbines shall have individual overspeed trip protection for each shaft.
API 616 3.22: maximum continuous speed: The speed (revolutions
per minute) at least equal to 105% of the highest speed required of any of the operating conditions.
API 616 3.38:rated speed: The speed (revolutions per minute) of
the gas turbine output shaft at which site rated power is developed.
For a turbine with a rated speed of 10300 rpm, is it okay to have the overspeed trip at 11330 rpm (110% of rated speed)?

RE: API 616 overspeed trip setpoint specification

Section 1.1 of API 616 does allow a vendor to offer alternative designs. Therefore, an overspeed trip setting higher than 5% may be acceptable. However, please be certain that the turbine is designed for an appropriate maximum speed. For example, a turbine with an overspeed trip setting of 110% may need to be designed for a maximum speed of 120%. I would also suggest requiring an overspeed test at the maximum speed in the factory.

Best of luck!

RE: API 616 overspeed trip setpoint specification

(OP)
Thanks for your reply stgrme; What reference are you susing for the speed? Are those refering to the percentage of rated speed?

RE: API 616 overspeed trip setpoint specification

The OEM typically specifies what is the OS setting of their protection devices.

Also, classification societies (Lloyd's, ABS, Bureau Veritas, etc) and insurance companies have a lot of experience on this matter.

The over speed protection sttings for mechanical drives (e.g. compressors) is typically different than for power generation.

In power generation i've always seen the electrical overspeed protection setting at 110% (10% above rated speed) and the mechanical over speed bolt setting at 112.5%
Since the early 1990's the classification societies, insurance companies and construction codes have accepted the elimination of the mechanical overspeed bolt replaced with a second, independent, set of speed pick-ups for overspeed protection.

saludos.
a.

RE: API 616 overspeed trip setpoint specification

(OP)
Thanks for your input Albetio!
The number 110% seems to be very frequently evoked as overspeed shutdown setpoint!
I have a litle bit of confusion between the different terms used in the standard; what is the relation between the MCOS (maximum continuous speed) and the Rated Speed?
Stgrme, in view of API 614 section 1.1 (The vendor may offer alternative designs), how do you evaluate the compliance to the API614 standard?

RE: API 616 overspeed trip setpoint specification

(OP)
Read API 616 instead of API 614 in the previous post

RE: API 616 overspeed trip setpoint specification

API 616 covers both mechanical drive and generator drive applications. For mechanical drive applications, the gas turbine will operate over a range of speeds; therefore, the overspeed trip setting would be in relation to the upper limit of the operating speed range (MCOS). For a generator drive, the speed of the gas turbine will be constant and will be referred to as the rated speed. Therefore, for a generator drive, the overspeed trip setting would be in relation to the rated speed.

Generally, the gas turbine will be designed for a particular maximum speed. This maximum speed, determined by the gas turbine vendor, is selected based on the speed attained on a loss of full load event (perhaps, with a small margin added). The gas turbine vendor chooses an overspeed trip setting to avoid reaching this maximum speed. Setting the overspeed trip too low may result in spurious trips.

As abeltio noted, an overspeed trip setting of 110% of rated speed is quite common for large indutrial gas turbines in power generation service.

For vendor's alternative designs, you must evaluate each deviation from the API 616 standard. If you are not confident in making those judgments, hire a qualified consultant.

Best of luck!

RE: API 616 overspeed trip setpoint specification

Normal speed = 100% rated speed. that is for the rated or normal point of all driven equipment

Maximum Cont Operating speed (MCOS)= 105% of normal speed, This is the speed that would be required by any of the specified operating conditions.

Trip speed = 110% of of MCOS for steam, 105% MCOS for gas. in relation to normal it is 115.5% (of 100% normal)=105*1.1 for steam and 110.3% or normal = 105x1.05 for gas

The whole idea behind API machines is the ability to meet the process needs at all off design points,

RE: API 616 overspeed trip setpoint specification

(OP)
Thanks to all for your input!

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources