Vitec Vibration probe

N

Thread Starter

NVS

Dear sir,

We are having GE Frame-3 machine with MARK-IV control system.
Actually we are planning to install Vitec 4033-500 velocity transducer in place of Vitec 4033-400 velocity transducer for BB4 and BB5 as they located at exhaust, as the temperature is high at exhaust Vitec 4033-400 were getting damaged periodically.

Major Diff b/w Vitec 4033-500 and Vitec 4033-400 impedance @25deg during normal/test condition is 320ohms for 500 series and 220ohms for 400series

So will this impedance changes reflect our control system or not ?
 
F
Impedance here referring to the electronic segment from your sensing element. 4033-500 is designed to work under higher temperature, 400-500F, therefore proper design in electronic segment results higher impedance to overcome the failing bias voltage.

Refer: http://www.modalshop.com/calibration.asp?ID=311

As summary, it does not impact to your control system.

Rgrds,
Franco Kew
 
NVS,

I don't believe the impedance difference will affect the Mark IV, but you should be certain the sensitivity ratings are the same. If they are not, you may need to change the input's sensitivity (if possible--some early Mark IV's could not be changed without a new PROMset) to match the sensor's if it's different from the old sensor's.

The Mark IV applies a small voltage/current to the seismic (velocity) pick-up circuits when the turbine is NOT running. This is done to ensure the circuit/loop is complete and not open prior to a start. (Velocity vibration pick-ups generate their own voltage when the turbine is running--in other words, they are "self-powered." So, to make sure the input loop is complete (the sensor is connected to the panel) prior to a start the Speedtronic applies a small voltage/current and monitors to see that there is current flowing in the circuit when the turbine is NOT running.

The change in impedance may have some impact on the off-line vibration test, but most likely not.

It's surprising the higher-temperature sensor wasn't provided as "original equipment." Having said that, many sites--in an attempt to reduce costs, try less expensive sensors. Some work; some don't.

In any case, please write back to let us know how you fare.
 
Dear CSA,

we gone with vitec 500 probe and as said during testing it impedance impact is there and during operation everything is normal.

Thank you for your valuable suggestion
 
HI,

please note that for this problem it is better to install high temp probes to solve your problems (exhaust temp may be around 500 degree C)
refer: WWW.Bently.com.

Best REGARDS
SARADHI
 
Dear sir,

please note that VItech probe is suitable for high temp application (MY experience with GE FRAME 5/3 EXHAUST TEMP IS AROUND 400 ABOVE Degree C).

IT is better consult bently nevada company

best regards
saradhi
 
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