I attempted to get 1X amplitude/phase data from a fan we plan on balancing yesterday and could not get my optical tachometer to trigger. The tachometer in question is a Monarch SPS-5. Today I tried the tach on another piece of equipment (pump), and it works fine. This makes me suspect that the reflective tape on the fan is "bad", whatever that means for reflective tape.

I did verify that the fan had a piece of tape installed (last week) before the fan was started, but did not have a strobe to verify it's presence while in service.

This fan is not easy to get to (inside Containment - Nuke Plant), so I can't just run out and strobe it. I spoke with a HVAC tech familar with the fan and he indicated that the piece of tape was pre-existing.

Can reflective tape go "bad"?

I don't know for sure wheter tapes can go "bad".

Maybe the tape was a bit worn or dirty?. If the fan is off, you could replace the tape with a strap of new one and try again the tach.

Another thing could be that the fan turns with a velocity outside the span of measurement of your tach.

Again, i don't if the tapes go "bad" but, who knows? you might have discovered the first one that goes so.

Merry xmas

This message has been edited. Last edited by: mechanical pawn,

Yes - reflective tape does have a life span, typically rated at 5-7 years. I'd go with a waterproof tape to better endure an industrial environment.

http://www.reliabilitydirectstore.com/Waterproof-Reflec...t-p/mon-6180-079.htm

There are several types of reflective tape available... not sure they are all compatible with all tachs. Optical tachs have to be pretty close to the tape to work (~6" or so?). I think you will generally have better results with a laser tach (works further away, at more of an angle, etc). I have several of the Monarch PLT200's and they work well, especially for around $200.

You can also use a strobe with a TTL output to get your reference run data, and then add a fresh piece of tape when you shut down to do the trial run. This procedure has been covered before. Follow this LINK (be sure and scroll down to the links Bill Kilbey provided also).

This message has been edited. Last edited by: rustythevibeguy,

Another advantage of a Laser or Strobe is that you could use reflective paint as a trigger instead of tape.

Reminds me of time I was having trouble with Monarch plus tach.
I thought it was the tape but it turned out the light had moved out of its mount behind the magnifying lens.
A bit of glue and it worked like new. I like it when that happens!

Mike.

Steve,

I use the Monarch ROS sensor with the red light. I have used a lot of different targets with good success including several types of reflective tape, white tape, white paint and white-out correction fluid. The biggest issue is contrast with the target. I have used black spray paint, black duct tape and electrical tape as a background. The ROS has a green LED that lights when trigger occurs. You can even slowly wave the sensor by hand to see if it triggers and is working correctly.

I don't think degradation of the reflective tape is an issue. I balance an ID fan outdoors in a hostile environment. I wipe the crud off of reflective tape and it is good to go. If you can't easily change the background on the shaft and the tape is still in place, then try changing sensor distance, angle or orientation to avoid ambient lighting or poor contrast.

Walt

Thanks for the replies.

Dave - Do you know what the age related failure mechanism is for the tape?

Walt - We have the same ROS sensor with the red light. We have also had a lot of success with the sensor and tape. I could not get the green LED to light (trigger) on this fan. The next day, I took the same tach/sensor set up and was successful on a pump with a piece of pre-existing reflective tape.

I spent approximately 10-15 minutes trying to get the tach to trigger on the fan. I was manipulating the distance and angle between the sensor and tape. It wasn't a lot of fun (dressed out in protective clothing (PCs), fan running, wet floor, standing on a ladder, in the dark). That's one detail I left out, the light in the enclosure was burned out, so the ambient conditions were dark. It made it easy to see the red light.

Thanks,
Steve

quote:

(dressed out in protective clothing (PCs), fan running, wet floor, standing on a ladder, in the dark).

That being the case, I think I'd upgrade to a laser tach, and also get a small strobe light with a TTL output (PK2X Pocket Strobe or a Monarch Palm Strobe for instance) to have as a "backup" should you need it.

I blew a couple or runs recently on a cooling tower fan balance when someone snagged my tach cable (and didn't tell me). I prefer to mount the tach at the gearbox, but in the future I will put tape on the end of one of the blades, and mark a location on the shroud that is inline with the tape. Then I can drill a 1/4" hole in the shroud if necessary to go to a Plan B (a 2nd laser tach with a "virgin" cable that I know is good).

Hi all,
tachometer/phototach has limited range distance between tape and phototach itself and also limited speed range. To know how high speed your tool has, refer to manufacture spec.

Regards,
Rahardi, Minas Indonesia