Machine Foundation Design -Stone Crusher Plant Foundations( Small/medium)

[D.Jaya]

Dear Structural Engineers,

We need to install a small/medium sized crusher plant(Crusher size L=1500mm,W=1390 mm, H=1400 mm) at our site.
I was asked to give a structural detail design for the Supporting structure for Feeder, Crusher & separator etc. I am an intermediate level structural Engineer but haven’t design a Machine Foundation up to date.

Thereafter I studied the literature and other information related to M/C foundations and having a basic idea about this matter and a preliminary design also has been prepared(Pl. refer to the attached drawing). I took the RCC Base sizes for the crusher & feeder as to satisfy the 3 times (crusher & feeder) weight requirement as per the standard practice requirement.

The Crusher weight is about 2800 Kg and RPM is still not known (I was provided only the Weight of the crusher and the full specification still not received by me) therefore I assumed the RPM as around 300

A schematic drawing with the crusher dimensions and the required vertical distances that to be provided at the site has been issued to me. The respective levels (earth cutting etc)has been done (the RR masonry retaining wall is just an indication only. A proper design drawing will be prepared)

I am having the following doubts to clarify please

1)According to the requirements and the site situation a small gap of about 100 mm (max) is available between the Crusher RC Base and RC wall as well as the feeder RC base and RC wall.
Is the gap is enough /or any type of vibration isolation layer is required ? Is the vibration effect the
RC wall.

2)Do I need to carry out a dynamic analysis/Vibration study to design the reinforcement of the RC bases /RC supporting columns

Your views on this regard will be highly appreciated

Regards,
Dushyantha

 

[1503-44]

You should also obtain dynamic properties of the soil.

You need to do a dynamic analysis to ensure the machine-fdtn system operates outside of resonance. Operating rpm nees to be < 0.7 x Fr, or > 1.4 × Fr. Low frequency systems <1000 Hz husually have the most trouble with that. Maximum vibration amplitudes should be < allowable at all points.

Static analysis should ensure that center of soil pressure is directly below the center of gravity of the mach-fdtn.

 

[Ingenuity]

Definitely get more info on the crusher characteristics before you proceed too much further.

I am currently doing replacement supports and anchor rods to a 150 ton crusher. It is a hydraulic jaw-crusher and operates at about 3.7 Hz. The original installation used cast-in weld plates and whilst the sub-structure is adequate, the weld plates (that connect the sub-structure to the steel sub-frame skid) fractured due to fatigue.

A book that is worth reading is "GROUTING HANDBOOK - A STEP-BY-STEP GUIDE FOR FOUNDATION DESIGN AND MACHINERY INSTALLATION - HARRISON - 2nd EDITION". It does not delve into too much dynamic analysis, but it gives good details on the use of epoxy sub-frame grouting and anchor rods, preload etc.

 

[HTURKAK]

[quote

1)According to the requirements and the site situation a small gap of about 100 mm (max) is available between the Crusher RC Base and RC wall as well as the feeder RC base and RC wall.
Is the gap is enough /or any type of vibration isolation layer is required ? Is the vibration effect the
RC wall.

2)Do I need to carry out a dynamic analysis/Vibration study to design the reinforcement of the RC bases /RC supporting columns][/quote]

1)I would prefer to combine the foundations of crusher +retaining wall+ found. of feeder. But the use of Vibration Isolation for the Crusher found. should be an option..

2) Dynamic analysis is better . Otherwise follow the rule of thumbs.. ( reduce the safe soil bearing stress to 60% , provide weight of ftg 3 times of vibrating wt..

I will suggest you to look;
- FOUNDATIONS FOR INDUSTRIAL MACHINES, Handbook for Practising Engineers (K.G. BHATIA ),

- ACI 351.3R-04 Foundations for Dynamic Equipment,

And you may post more info. to get better responds ; for the crusher characteristics and plan of the sketch with sizes of proposed walls etc.

 

[WARose]

2)Do I need to carry out a dynamic analysis/Vibration study to design the reinforcement of the RC bases /RC supporting columns

Given this layout, I'd say: yes. (It will also help answer your first question on that gap.)

 

[D.Jaya]

Dear Gents

1503-44 (Petroleum), Ingenuity (Structural),HTURKAK (Structural),WARose (Structural)

Thanks a lot for your valuable comments