BOILER FORCED DRAFT FANS

Greetings Members,

The FD Fans on a tanker vessel attached the vibration spectrum and the photos of the FD fans.

Vibration on motor HVA is less than Vibration at fan foundation fitted on pads 3 nos on each side.

Appreciate your feed back and suggestions for repairs.

Kind regards

Chary

 

 

 

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Original Post

Greetings Mr. Shurafa,

 

Pleased to note your comments.

1. Yes -Impact test should be done- Good point 

2.Bump test- what is your opinion.

3. Monitor mode data - while tightening carefully, What about loosening and retightening with torque in sequence.

4. This is onboard a Tanker ship, 7 years old and according to crew onboard 2 years back the fan was overhauled and balanced.

5. The vibration, as you might have noticed, is high at foundation pads, floor  vibration is negligible 0.45 mm/s.

6. Please suggest corrective actions to overcome this vibration issue. As per IACS(International classification societies) maximum satisfactory limit is 7.0 mm/s for Horizontal FD Fans.

Once again we appreciate your reply and looking forward to share your expertise.

regards

Chary

 

This can be due to the stiffening or worn out condition of the pads on which the fan foundation is resting i.e., it is no more damping the vibration. External inspection of these pads can be done to look for indication of cracks. Of course this action assumes that there is no other maintenance job being performed on the motor/fan and the problem is of gradual nature.

What is the last maintenance job performed on the machine?

When is the last time the vibration values measured at the foundation is normal and what is the value?

chary tatta posted:

 

4. This is onboard a Tanker ship, 7 years old and according to crew onboard 2 years back the fan was overhauled and balanced.

 

regards

Chary

 

The fan overhaul and balance; this wasn't perhaps done in a drydock situation was it?  Sometimes an alignment in drydock doesn't prove to work out well when the vessel is in the water.

Greetings Ingenious & John from PA,

 

Pleased to note your input and thanks for your interest n the given issue.

1.Onboard this vessel, No vibration records available. 

2. Your suggestion about pads inspection and maintenance shall be informed to vessel management.

3. Other than greasing to motor and fan air damper lubrication, motor megger testing no maintenance done.

4. As Mr. John said, previous dock report not available and Vessel Stay in Anchorage was only few hours and simple test was performed for High vibration levels. 

5. The maximum data can be drawn through Photos, vibration readings and FFT /Time spectra.

Thanks for your input and appreciate your interests and in future I will present more case studies for our forums.

 

regards

Chary

 

Is this data and pictures you have posted on 2 different fans? One, I think, says "Port side" and the other says, "Starboard side". Is this correct?

If it is of 2 different fans, are both of them a problem?

Was data taken on the center and suction end points of the framing?Frame

 

Attachments

Photos (1)
Ralph Stewart posted:

Is this data and pictures you have posted on 2 different fans? One, I think, says "Port side" and the other says, "Starboard side". Is this correct?

If it is of 2 different fans, are both of them a problem?

Was data taken on the center and suction end points of the framing?

 

Ralph, I would put money on it being two fans.  The wording on the supplied data is not actually "Port side" and "Starboard side" but port boiler and starboard boiler FD fans.  In any given fan mounted off the longitudinal center line of the vessel one would refer to a position relative to the fan as being on the inboard or outboard side.

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