Turbine Key Phaser Function

Key phaser in turbomachines are necessary to find phase angle of unbalance mass at the time of dynamic balancing. Balancing of turbine rotor is essential. Manufacturers at there shop can balance the rotors with some other means even if key phaser is not present. But when rotor is to be balanced at user's site, key phaser is required.

in our plant, for boiler feed pump & cooling water pump also having key phasor. what is the need of providing key phasor for these pumps?

Pump rotors are also dynamically balanced.

It isn't surprising that such costly equipment would employ redundant safety measures. This PDF (courtesy of TRIVENI ENGINEERING & INDUSTRIES LTD.) explains much about the operation of a steam turbine prime mover. You might find the manuals for your installation even more useful and informative. May I suggest that you read them.

Dear,

First of all let's look at the real defination of the key phasor as below;

"The keyphasor is an electric pulse, or trigger, which is derived from a point on a rotating shaft. It serves as a zero phase reference for determining where imbalance is on a rotor." Keyphasor is a trademark owned by the Bentley Nevada Company, but has almost become a generic term by popular usage.

The usage of key phasor is for online vibration analysis. Let's take your example wherein key phasor is used for turbine machine monitoring system.

You can monitor the machine health with vibration probes alone but if you want to analyse the cause of failuer of the machin you need three dimesional graph showing/analysing the vibrations at any point of time when machine is running. If you dont install the key phasor you will come to know that there are vibrations in the machin but you will not point out at what direction, at what point, at what angle.

When you are providing MMS for any rotating machin with key phasor means; you will have one notch on the shaft which will be referance point for analysis & with respect to that point vibrations will be measured (by knowing the displacment, velocity or acceleration). The key phasor will interact with the accelerometer type vibration probes & will plot 3 dimensional graph.

What is the purpose of keyphasor sensor in vibration monitoring sensor ?

tell me its working principle ..

Every reply is mostly correct and I'll add my two cents. The Keyphaser is used as a reference point of the shaft, 0 to 360 degrees. When analysis are performed via handheld, BN system or other, the viewing of the 1X and 2X signals are important, X is defined as the running speed of the machine. The monitors read overall vibration signals at all frequencies, the Keyphaser is used to determine the speed. Lets say your BFP is running at 5,000 RPM, with a Keyphasor, the instrument can filter the frequency to 5,000 rpm or 83.33 Hz. With this signal, one can view the shaft behavior or orbit inside the bearing. The phase is calculated as from the time the Keyphasor triggers to the first positive peak of the vibration signal. My recommendation, leave it installed in the event someone needs to analyze data whether inhouse or outside vendor.

Ken Hoellger

www.pdmcal.com

GA to last 2 posts.

I agree with answers. Please follow below link for detailed and comprehensive information for use of Key Phasor

http://www.slideshare.net/GE_MC_India/why-installkeyphasor