Why would you let it fall when the technology is there to stop it? Unless you enjoy destroying your equipment. http://www.horne-group.com/our-products/technogrid/ Watch the video on this page.

To answer your question is simple physics. As an object falls its gravitational potential energy (PE) is changed to kinetic energy. As it falls the initial kinetic energy is 0. Once the mass hits the ground the height is 0 therefore no potential energy as it is now kinetic energy.

C&P from The Engineering Toolbox

Impact Force from a Falling Object

The dynamic energy in a falling object at the impact moment can be expressed as

E = F_w h

= m g h



where



F_w = force due to gravity - weight (N, lb_f)

m = mass of the object

g = acceleration of gravitity (9.81 m/s², 32.17405 ft/s²)

h = falling height (m)



The equation can be combined with the equation of work:

F = m g h / s ■

Gary's answer is all that you need.

But please explain;

why the bend pulleys have different diameters;

what happens to the debris from the scrapers;

why there isn't a simple rope passage to allow the kentledge to work nearer to ground

and why you don't do like the clever lift shaft people do and fit arrestors?

This is one more nail in the coffin of GTU's not taking cogniscance of crane rules.

Re Technogrid

"After a full impact, the Technogrids simply need to be replaced and then the Technogrid arresting system is ready for the next impact."

This is not quite good enough. ■

You're right John. A thorough and fully detailed damage assessment of the take-up structure and arrestor frame needs to be performed as well. The Horne Group just sells the arrestor so that is where their responsibility lies. ■

Firstly through appropriate: design, selection, construction, and maintenance etc; ideally we may have already limited the likely hood of failure to an "acceptable" level.

Failing this, or if the assessed residual likely hood exceeds an acceptable level, in addition to others' suggestions, I have seen "load arresting" counter mass guides [guides with "bends" in them etc].

To expand on Gary's contribution in particular, the "Mass and Weight" section of the following document may be of interest [though please note I did not review in detail]:

http://www.pdhcenter.com/courses/s164/s164content.pdf

If this topic [impact loads] is of interest, it may interest you to review the various relevant threads over at eng-tips.com.

I have a feeling that it has been discussed previously on this forum, though I could not find it in a brief review just then.

In addition to others' observations, if the current arrangement is adopted, it may be worth considering if:

1. There is value in the counter mass being physically closer to ground [i.e. a longer length belt loop], and hence removing the risk altogether [?], and hopefully improving maintainability [though this may not be possible; and it has its own issues]. However I believe this is "similar" to what John suggested [and John's suggestion may be better].

2. If 1 is not an option, if you can supply more "user friendly" access [stairs, in lieu of ladders etc]. You will also need to consider construction [If the counter mass impacts something when the belt "snaps", how does it get in there originally? How do you remove the counter mass for maintenance etc?]

Regards,

Lyle ■

Hello,

Finding the impact force due to such falling object is by simple standard formula for linear motion: (V square) minus (u square) = 2as, where v is the final velocity, u is the initial velocity, a = deceleration and s is the distance the object will travel after impact. You know the fall height. Accordingly find the initial velocity u just prior to impact. This will be Squareroot of (2gh). The object is coming at rest during the impact process. Therefore, final velocity v = Zero. The stoppage distance to be considered or assumed initially and find the deceleration value. The deceleration value multiplied by the mass of the impacting body will give the average impact force.

It is closed circuit solution. Having found the impact force see that whether the medium taking the impact will deform by the assumed displacement due to the impact force. The consideration of the right value of displacement complementary to the shock absorbing medium require careful thought and experiment if need be. The shock absorbing medium should be deforming in nature and at the same time stiff enough to resist the deformation. After reviewing the above calculation, one has to choose the revised value of displacement s and do the calculation again to find satisfactory result.

The easier and practical solution is to opt for winch take-up (fixed length of belt during conveyor running). Functionally it behaves like a screw take-up. The winch take-up system will have load cell to set the correct tension periodically (say weekly after sufficient use). It seems your conveyor is not outdoor. So belt thermal expansion / contraction will be small and thereby least influence on tension setting.

The people have reservation about using winch type take-up for surface installation. But such winch type take-up arrangement is a standard feature for mine conveyors. At Neyveli India, 20000 mtph capacity conveyor and 6250 kW installed power, probably have winch type take-ups. Often there is too much fuss about wrap angle at drive pulley and engineers doing acrobatic arrangement to achieve it (the present day synthetic fabric belt require small pulley and thereby it poses a problem in having 210 degree wrap angle of cotton fabric era). Incidentally the drive pulleys of aforesaid conveyors transmit power of very large magnitude only by approximately 180 degree wrap angle.

Ishwar G. Mulani

Author of Book: ‘Engineering Science And Application Design For Belt Conveyors’. Conveyor design basis ISO (thereby book is helpful to design conveyors as per national standards of most of the countries across world). New print Nov., 2012.

Author of Book: ‘Belt Feeder Design And Hopper Bin Silo’

Advisor / Consultant for Bulk Material Handling System & Issues.

Pune, India. Tel.: 0091 (0)20 25871916

Email: conveyor.ishwar.mulani@gmail.com

Website: www.conveyor.ishwarmulani.com ■

Hello,

Following shorter and easier method suggested by Gary Blenkhorn will also give the result same as by the method described by me earlier:

Impact energy to be absorbed = m.g.h (Nm)

Suppose impact force is F which stops the impact motion within distance ‘s’, then

F.s = m.g.h Hence F = m.g.h ÷ s, where F is in Newton.

Some more information on the subject:

1) Use of steel cord belt will reduce take-up stroke remarkably, and thereby less fall and less impact energy / force.

2) Use of dual pulley drive at head end, constant acceleration start-up and drive without brake will result into bare minimum take-up force (counter weight) and thereby less difficult situation.

Having opted for 1) and 2), you may contact Gerb, Germany, who are maker of visco-damper vibration isolation systems for huge forces, and see if they have something to offer, if it is in their product range.

In such kind of impact situations, hope that everything does not turn out to be of one time use, because everything will be subjected to the stresses due to impact force.

Ishwar G. Mulani

Author of Book: ‘Engineering Science And Application Design For Belt Conveyors’. Conveyor design basis ISO (thereby book is helpful to design conveyors as per national standards of most of the countries across world). New print Nov., 2012.

Author of Book: ‘Belt Feeder Design And Hopper Bin Silo’

Advisor / Consultant for Bulk Material Handling System & Issues.

Pune, India. Tel.: 0091 (0)20 25871916

Email: conveyor.ishwar.mulani@gmail.com

Website: www.conveyor.ishwarmulani.com ■