Tag Archives: bulk handling sector

DSI High Angle Conveyor Goes Mobile Down Under

There is no better example of the versatility of a DSI Snake than Australia’s first DSI Snake Sandwich High-Angle Shiploader at the Port of Adelaide on Australia’s southern coast.  Australia’s first Snake Shiploader elevates a variety of high value ores from trucks to ship.  Conventional conveyors would not have fit the limited dock space which required a smaller footprint.  Dos Santos International, being the world’s foremost authority on high angle conveying was able to fit the space easily by being able to elevate at a 50 degree angle.  If fitting the space wasn’t enough, DSI went a step above and created a mobile shiploader to elevate the materials with ease.

Materials for export are trucked to the dock and dumped onto a special trap loader type feeder.  The ore is fed continuously and uniformly onto the mobile snake’s receiving chute.  The Snake Ship Loader elevates the bulk over the ship’s deck to the hatch where it is discharged into the ship’s hold.  At the Snake’s discharge, a special telescoping chute, with rotating, pivoting spoon, facilitates even and complete filling of the holds.  The mobile Snake is carried on a tripod of twin motorized rubber tires.  Each set of twin tires is mounted at a vertical kingpin and can rotate 360 degrees about the vertical axis.  Thus, without repositioning, the Snake can set up to travel in any direction (by pryor).  With the tail tires fixed, the front tires can be oriented and traveled for a slewing motion.

This first DSI Snake Ship Loader for Australia has set the pace for many more high volume high-angle installations at materials handling docks and yards throughout the world.

For more information, visit www.dossantosintl.com

I have an issue with a materials handling system and now where do I go with it?

I have an issue with a materials handling system and now where do I go with it?

This experience and question is being considered all the time as any given materials handling plant is going through this frequently. It can be so painful because the plant management wants it fixed quickly and with as little as possible economic impact.  You and / or your internal resources are completely overwhelmed with the task of diagnosing the problem by yourself and you know that you need help.  You suspect that the original equipment manufacturer maybe offering the most expensive fix with the longest time frame attached to it.  Now what do you do?

At the root of the problem is surprisingly one key item:  You.  What I mean by that is that you let the situation get to you.  This is meant in terms of economic and time frame pressure exerted on you by either management and or the urgency of the project.  Now you make less strategic decisions due to not taking your time thinking through the problem at hand.  What happens is that you attempt fixing the issue yourself even though you do not know what you do not know.  In the end the problem can be made worse and now this can come back and reflect badly on your career.

Planning is everything here.  You do not plan, you plan to fail.  The following is a cheat sheet summary of what you can do to plan through your issue:

  1. Define the problem.  Seems a banality, but this is the top number one reason why no one will be ever be able to help you effectively.  What I mean is for you to define a problem statement and then what you believe the root cause is.
    1. The root cause emerges when you ask yourself and the plant personnel involved in the challenge fives times “why”.  For instance: Why do we experience a low conveying flow rate?  By the fifth why you will have really narrowed it down to the root cause.
    2. Develop a problem narrative in writing and sketch it out.  Sketches preferably should be to scale.  Photos do wonders!
    3. Stay to describing what the equipment status and condition is, rather than what should have been (some folks are afraid to admit that there are issues in the plant, this is no time to be timid!).
  2. This may surprise you, but I would speak with the original manufacturer first about your issue.  This may render totally positive responses and the fastest results to dealing with your issues.  At least you get to know the way how professionals would solve the issue and how.  You can still resort to the other methods of self-help, if the manufacturer blows you off or otherwise does not treat you like he should.
  3. Look at online resources like the Bulk Forum for help.  Here it will be helpful categorizing your issue correctly and with the detail knowledge from point 1 inserted in your request for help.
  4. Look around and ask friends and your connections in the industry.  If you are not connected, now would be a good time to get connected.  One excellent resource is LinkedIn.  It has excellent focus groups that deal with so many situations and if there is not one, start one.
  5. Finally, you can give the good old college try a chance.  Doing this yourself can be as scary as it can be rewarding when you solve the issue.  Point 1 really will come to your rescue as it helps eliminate as many as possible variables.  Make sure to not making changes too quickly and too many at a time such that you can study cause and effect of what you are doing.

Now that you have a pre-flight check list I will leave you to making a few important choices.  The first one is for you to choose actively whether or not you want to make a change.  Scan for the support of your management and their back up as well as their financial commitment.  Nothing is worse than having developed a detailed plan just to be told that neither money nor time will be made available to you.  Then choose to plan your remedy and the resources to do this with.  What problems will you start doing differently from now one?  Choose wisely.

Ralf Weiser

 

2009 – A year of opportunity

Yes, you are reading this correctly.  There is no doubt that 2009 will go down in history as a year full of challenges and will always be thought of as the year of recession.  Personally, I could have lived without having to think about furloughs and workforce reductions.  But this year has also been fascinating to me because of the many businesses that I have come across, which managed to not only survival, but even thrived under the most difficult conditions.  They have figured out that superior core ethics and flexible strategic risk taking can bring you back into the middle of the business opportunities.

Of course there are certain business segments – construction and thus cement being a few of them – that are as volatile as they come and the phone just stopped ringing.  For some of us the company size and product range may be too inflexible.  There are all kinds of good reasons why your business has suffered and you had to react however you had to react to at least stay afloat. Regardless, I assert that there are two omni important things you can do to get back into a blazing saddle:

Get your own core ethics in shape and make sure that people know you for it; it is useless how many people you know.  Now is the time where you have to have a lot of people that will give you the first call for any business that they may be able to afford.  Core ethics and values are essential in keeping and maintaining a great dependable and knowledgeable workforce that can manage to be friendly to everyone – who wants to deal with miserable people when there is so little to smile about to begin with?  Know what your brand is and make sure your people know and live it too.  This nimble workforce and your brand image is going to help you putting revenue into your business, and you know that cash is still king.

The second success factor is that you need to take controlled risks.  You must know what is going on with your customers.  Now is not the time to skimp with your sales and definitely not your marketing budgets.  Make sure that your management team hits the road and sees your customers – period.  This does two things for your organization.  On one hand your top leadership gets to know how a customer really perceives you.  You get the opportunity to see and feel the discrepancy with your board room decisions and strategies.  The other side of the equation is that you get to know how you can help putting cash into the pocket of your customers by solving their issues or perhaps you get to create a need they did not even know that they had.

Either way, you and your leadership team are coming home with a punch list that is more or the less the roadmap to your continuing success.  Now you need to be just brave enough to act upon it and you will be off to a stellar 2010.

Ralf Weiser

Copyright:  Ralf Weiser 2009

Pneumatic Conveying, Performance and Calculations!

In many industrial processes and transport, materials have to be stored and moved from one location to another location. For long distances, e.g. from one country to another country (or continents), modalities are used e.g. ships, aircraft, trains, trucks, etc.

Where changes are made in the transport (or storage) modality, various technologies are used to move the material from one modality to the other modality.

The basic applied technologies are :

  • mechanical systems
  • grabs
  • screws
  • belt conveyers
  • buckets
  • etc.
  • Carrying medium systems
  • Hydraulic systems using liquids as carrying edium
  • Pneumatic systems using gas as carrying medium

The bulk handling sector over the world is a key player in economics as it handles all kinds of commodities such as cereals, seeds, derivatives, cement, ore, coal, etc., which are processed in the industry to other commodities, which have to be transported and handled again.

To manufacture all the necessary equipment for the bulk handling alone a whole industry exists. The magnitude of financial investment is tremendous as well as the operating cost involved.

The importance of economic handling is not only a matter of the handlers, but also to third parties such as the transport sector.

The technology of bulk handling equipment is crucial to all the involved parties and therefore it is of the upmost importance that the bulk handling industry employs the best engineers and operators, who design, develop, build, calculate, operate the installations and do research and document their achieved knowledge and experience.

One sector of bulk handling is the pneumatic unloading and conveying of cereals, seeds, derivatives and powdery products such as cement, fly ash, bentonite, etc.

The first pneumatic unloaders were built around 1900. In 1975, there were still, steam driven, floating grain unloaders operating in the ports of Rotterdam and Antwerp. Unloaders, which even dated back from 1904.

How these installations were calculated is not really known as the manufacturers did not reveal their knowledge publicly for obvious (commercial) reasons. Trial and error must have played a significant role in the beginning of this industry.

Calculating a pneumatic system was, before computers were introduced, done by applying practice parameters, based on field data from built machines.

clip_image002.gif

Example 1975

Calculation grain unloader anno 1975

Set Capcity grain                                 440                  tons/hr

Bulk density grain                                0,75                tons/m3

Suction height (elevation)                     30                    m

Air displacement pump                        500                  m3/min

Vacuum air pump                                0,4                   bar

Absolute pressure vacuum pump          0,6                   bar

air density                                            1,2                   kg/m3

pressure drop nozzle                            0,16                 bar

Nozzle diameter                                  0,45                 m

Cross section nozzle                            0,1590             m2

Grain volume                                       9,778               m3/min
(Capacity/grain density/60)

Air volume at nozzle                            357,1               m3/min
(Air displ pump * abs press pump /(1-press drop nozzle))

Transport volume after nozzle               367                  m3/min
(Grain volume + Airvolume at nozzle)

Grain mass                                          7333                kg/min (capacity *1000/60)

Air mass                                              360                  kg/min
(Air displ pump * abs press pump * 1,2)

Transport mass after nozzle                  7693                kg/min (Grain mass + Air mass)

Specific density mixture                       20,97               kg/m3 (Transport mass after nozzle / Transport volume after nozzle)

Mean velocity of
mixture after nozzle                              2307                m/min
38,45              m/sec
(Transport volume after nozzle / Cross section nozzle)

Pressure drop nozzle                           1577                mmWC
11,98              cmHg
(specific density mixture * mean velocity^2 / (2 * 9,83))

pressure drop miscellaneous                  5                      cmHg

pressure drop vacuum pump                30,4                 cmHg
(Vacuum air pump * 76)

Available pressure drop elevation 1       3,416               cmHg
(press. drop vacuum pump – press, drop nozzle –
press, drop misc.)

Elevation per available press. drop        2,2361             m/cmHg (elevation / available pressure drop elevation)

Loading factor from diagram                24,45               kg/m3 (Loading factor = function (elevation per available pressure drop))

Calculated Capacity                            440,1               tons/hr
(60 * loading factor from diagram * air displ vacuum pump * (1- vacuum))

Table loading factor kg/m3 = function (elevation per available pressure drop)
image002.gif

Loading factor  elevation/cmHg
16                               3.6
17                               3.44
18                               3.28
19                               3.16
20                               3.0
21                               2.84
22                               2.64
23                               2.48
24                               2.26
25                               2.04
26                               1.74
27                               1.35
By changing the figures in this calculation, an iteration process is executed until the set capacity equals the calculated capacity The calculation can be started by assuming the pressure drop over the nozzle at 0.15 bar.

If a parameter is not known, assume this parameter and vary until an optimum is found.

It is clear, that this method is not really accurate, nor gives it a scientific insight how the physics of pneumatic conveying work.

Calculation of Pneumatic Systems using Gas as Carrying Media

Since computers are available, it became possible to build an algorithm that can execute calculations in a time domain, whereby the conveying length is divided in differential pipe lengths, which are derived from the elapsed time increment.

The physical principle of this technology is:
A gas flow in a pipeline will induce a force on a particle, which is present in the gas flow. This force (if of sufficient value) will accelerate and/or move that particle in the direction of the flow. (Impulse of air is transferred to particles) The particle is moved from location 1 to location 2.

Between pipe location 1 and pipe location 2 , impulse is transferred from the gas to the particles and to friction.

This transferred impulse is used for:

  • acceleration of particles
  • collisions between particles and from the particles to the wall
  • elevation of  the particles
  • keeping the particles in suspension
  • air friction

Bends are calculated only for product kinetic energy losses by friction against the outer wall and air friction pressure drop. The calculation of velocity losses in a bend are depending on the orientation of the bend in relation to the product flow.

There are 5 bend orientations to be considered:

  • vertical upwards to horizontal       (type 1)
  • horizontal to vertical downwards   (type 2)
  • vertical downwards to horizontal   (type 3)
  • horizontal to vertical upwards       (type 4)
  • horizontal to horizontal                (type 5)

All these energy transfers result in a change in the gas conditions (p,V,T) and changing velocities of the carrying gas and the particles.

All these energies, velocity changes and gas conditions can be calculated and combined into a calculation algorithm.

This algorithm calculates in the time domain (dt=0,01 sec)

The physical laws involved in this algorithm are:

  • Newton laws
  • Bernoulli laws
  • Law of conservation of energy
  • Thermo dynamic laws

From the original (start) conditions, the changes in those conditions are calculated for a time period  of dt. Using the average velocity over the period dt, the covered length dLn can be calculated. At the end of this calculation the energy, acquired by the particles, can be calculated.

By adding those changes to the begin conditions at location 1, the conditions at location 2 can be calculated for the particles as well as for the gas.

From there, the calculation is repeated for the next interval of time dt (and length dLn+1), covering the distance from location 2 to location 3.
The output of section dLn is used as the input for section dLn+1.
This procedure is executed until the end of the whole installation is reached.

All the conditions at the intake of a pneumatic conveying system are known. Therefore the intake is chosen as the start of the calculation.

In vacuum- and pressure pneumatic conveying calculations, the used product properties are identical. The only difference is the mass flow, generated by a compressor in vacuum mode or pressure mode.

The calculation result should be the capacity at a certain pressure drop.

However, both these values are not known. To calculate the capacity, the pressure drop must be set and the capacity must be iterated from a guessed value. The calculated pressure drop from a “wrong” guess will be different from the set pressure drop. Therefore the capacity guess is renewed in such a way that the new, to be calculated, pressure drop, approaches the set pressure drop. This iteration ends when the calculated pressure drop equals the set pressure drop. The capacity that resulted in this pressure drop equality is the wanted value. (Input and output are consistent) (Notice the similarity of the iteration process with the example 1975)

This iteration can also be executed, whereby the capacity is set and the pressure drop is iterated.

Example of a computer calculation 2007

image001.png

image002.png

Example of a modern computer calculation 2008

image0031.png

image004.png

The computer program is originally written in Q-basic under DOS and still operates, although some features are now lost under Windows

By changing the program from Q-basic to VisualBasic, the screens appear in a Windows form and more Windows features can be applied, but the program algorithm stays the same.

A very important feature of this algorithm is that performance data from existing installations can be used to determine the product loss factors for certain products. That opens the opportunity to build a database of various products that can be conveyed pneumatically and be calculated. As the used physics are basic, the calculations work as well as in pressure mode as in vacuum mode with the same formals, product parameters and product loss factors. (Adaptations are made for the different behavior of the gas pumps in pressure mode and vacuum mode)

As the pneumatic conveying calculation is basic, the calculation program can be extended with many other features s.a. booster application, rotary locks, high back pressure at the end of the conveying pipe line, heat exchange along the conveying pipe line, energy consumption per conveyed ton, Δp-filter control, double kettle performance, sedimentation detection, 2 pipelines feeding one pipeline, etc. Also it becomes now possible to evaluate product pneumatic conveying properties from field data and tests and also investigating operating machines for functioning. (Defects were found, just by calculating the actual situation).

Based on the properties of pneumatic conveying, derived from the above described theory, the used technology is chosen. The used technology and operational procedures are also depending on the type of application and product.

The above only describes the calculation of pneumatic conveying based on physics. The connection between theory and practice is made by measured and calculated parameters from field installations. In addition to this theory, there are many technological issues to be addressed, ranging from compressor technology to the structural integrity of a complete unloader as well as PLC controls, hydraulics, pneumatics, electric drives motors, diesel engines, filter technology, ship technology, soil mechanics (product flow), maintenance, methods of operation, etc.

The mathematical approach with the field verification (resulting in many corrections and extra features), documented description and creating the computational software is (was) a matter of many years of persistent labor but worthwhile. This approach also resulted in a better and still growing understanding of the pneumatic conveying technology. The influence of the various parameters and there effects (sometimes hidden by counter action) was revealed step by step.

July, 2008
Teus Tuinenburg
The Netherlands