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Grating Mezzanines
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24 April 2013:
Grating Mezzanines
LGMI R
As we have stated previously, we are going to be taking the ideas developed in this column over the last couple of years and developing them into design practices.  This is how it works.  We will provide the basic narrative here for one design practice each week.  We will keep it open for comments for one month.  After that, we will finish it in formal form and offer it for sale at a modest price.  Here is where you come in.  If you make a substantive contribution to a standard, the organization for which you work will be granted a pro bono license to use that standard with its current issue number for as long as you like.  We have had good response so far!  Contribute, please.

This week's:
Grating Mezzanines (LGM 2013.016.01
when issued)

Reference:

Traditionally, mezzanines and other infrequently traveled surfaces are provided with concrete floors just like the rest of the mill, despite being subjected to low foot traffic, minimum load, and limited maintenance activities. Why is this?

 

Objective:

To eliminate the use of concrete by utilizing alternate materials for mezzanines and other infrequently traveled surfaces.

 

Consideration:

Modern galvanized steel or fiberglass grating with anti-skid surfaces provide a suitable alternative, offering significant weight reduction and better access (the grating can be removed when necessary to hoist motors or fans to the mezzanine exactly where needed).


So, give us your comments by 21 May 13, please!

Still open for comments: Electromagnetic Press Rolls (Open until 14 May 13)

Still open for comments: Cantilevered Dryers (Open until 7 May 13)

Still open for comments: Variable Speed Pump Drives (Open until 30 April 13)
  
As always, your comments will be appreciated.
Think light!

 

Brian Brogdon, Ph.D.
Executive Director

 

or

 

Jim Thompson
Founder
_____

LGMI Feedback

Brian,

 

Variable speed drives are a great investment in most pumps of any size, at the initial installation stage, since the extra capital cost is lower than retrofits.  Unfortunately, most project managers are more oriented to low capital costs than to low long-tem costs.  They are gone by the time the plant is in production.

 

Most discussions and analysis evaluate power consumption by properly sized pumps.  However, in my experience, about 80% of pumps are seriously oversized for normal service.  Some times there is a reason for a large margin, but usually it is just because engineers know that if it does not work they are in trouble, whereas if it wastes energy nobody notices.  

 

You have mentioned pumps oversized by 20%.  I have seen MANY oversized by much more than that.  Worst was over 500%, where we replaced a 100 HP pump with a 20 HP motor, slower speed and trimmed impeller.  It still ran with the control valve half open, but at least the noise level dropped and the valve did not require regular replacement.

 

All mills should survey control valve normal positions and analyse pumps operating well below full-open, with a view to variable speed conversion.

 

A supplementary benefit of variable speed pump drives is a great reduction in nose level in the mill.

 

Many agitators could benefit from variable speed drives too.  The lack of reliable design criteria for most agitator service leads to overdesign in many cases.  When you vista several mills, it is striking how much agitator size varies for equivalent service.  clearly the larger ones are too big.

 

Neil McCubbin

 

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Disclaimer

 

LGMI Weekly Ideas are presented for your consideration and inspiration only.  It is solely your responsibility to check for engineering correctness, applicability, standards, insurance policy and local, national or any other legal compliance required before implementing.  Neither The Light Green Machine (TM) Institute, Paperitalo Publications, Talo Analytic International, Inc., nor any individual associated with these entities accepts any responsibility for your application or compliance issues.

 
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