How often should belt tension be checked?

[superdumpy]

Hello,

Just curious as to the intervals of checks on belts are for different plants. We run HVAC units on belt systems 24/7 on motors on average of 75kw and we have an interval of 6 months. I'm beginning to suspect this is not ample as we are experiencing belt failures.

Kind regards,
Thomas

 

[MetalworkerMike]

You check tension and alignment (not just tension) when you first install the belts, then I check it after one day, then after one week, in constant-running belts like that. This is because you want to catch any sheave creep early on, and belts stretch the most early in their life. After those two checks then every six months should be fine.
That's my opinion, anyway.

Mike

 

[stardelta]

Belt life depends on a number of factors. Age, condition, amount of loading they take, correct tensioning, enviromental conditions, condition of pulleys, motor starting methods (soft-starts or DOL etc)..... There is no simple answer to your question. The accepted practise is to monitor your failures, get to the root cause, look for any trends, formulate an average lifespan for the belt and learn to predict the failures.

If I had to give you a time period I would consider the implications a failure of your equipment would have and with this in mind say as often as production and financial constraints allow.

 

[controlsdude]

Belt failure or loose belt would mean that you would have varying current on the VFD. Could you have an additional alarm to look at the current when the it is at steady state current. If it is out of bounds then set a warning to check belt? Out of bounds would be a varying current that could point to a loose belt or a belt that is jumping on the pulleys?

 

[Tmoose]

What is the nature of the belt failures?

Are the belts the right section for the sheaves? Too narrow belts ride the groove bottom and can't transmit much power at all.

tAre the belt guards ventilated, and visible?

An infrared temperature check of belt and sheaves would help reveal slipping which is the main problem with "looseness."

If either sheave diameter is too small then cut belts can help a lot. Actually I like them on most equipment except garden equipment that uses an idler as a clutch, when only the wrapped green stripe belts will do.

 

[RRaghunath]

Superdumpy,

It is rather an easy one.

If the occupants of air conditioned area complain of inadequate cooling, the belt is loose.
If the thermal overload element of the motor protection is operating and tripping the motor often, that means the belt is tight.

I think the above comes under condition based maintenance and more preferable than periodic maintenance (I believe so).

 

[MetalworkerMike]

Just as an aside, I happened to be glancing through a manual for a vacuum pump, and the manufacturer specified that the guard be unbolted and the belt tension checked _every_ _week_. You won't see _me_ doing it that often!

Mike

 

[itsmoked]

Just check whenever your pants start slippin down.

LOL

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[rawelk]

One thing you might consider is getting a set of English and metric sheave check gauges. After x number of years (and especially if belts had been slipping for a while previous to replacement) sheaves become worn. This result in diminished power transfer capability, and, when severe, almost certain slippage, and/or the need to over-tighten belts to prevent slip.

Gates has a decent write-up on belt maintenance available at

http://www.gates.com/index.cfm?location_id=5011

(registration required).

Carlisle has a web page showing what these critters look like.

http://www.cptbelts.com/tools/sheavegauge/index.html

They also has several excellent maintenance and troubleshooting guides (registration required).

http://www.cptbelts.com/customercenter/literature/literature.html

 

[superdumpy]

All,

Thanks for the help. I've been off sick so didn't get back to you all. I've decided to get an allignment expert in to start from scratch. All currents and frequencies will be monitored.

And just for 'itsmoked' I've bought a lovely pair of red braces for my pants!!

Thanks again for all the responses.

Thomas.