Dear DBT,

Verify if the unloader suction arm can lift a small frontend loader of approx 1100 kgs.

Also, check whether the applicable regulations allow this procedure (f.i. with or without testing)

The frontend loader is then used to clean the hold’s floor.

The handling of the barge covers should be possible with onboard facilities, otherwise, the use of that barge would be restricted too much.

Using the suction arm for this purpose is not the way to go as it is time consuming, due to the poor maneuverability of the unloader arm and the damage responsibility towards the barge owner.

How are your unloading procedures right now?

Have a nice day

Teus ■

Dear DBT,

Since I am retired, I operate the kitchen sink and spend more time on this forum.

From your description of the operation, I can say that you are following the same procedure as other cement unloader operators do.

Up till now this has proven to be the best way to do a cement unloading, whether a barge or a sea going vessel. Only the equipment size differs.

Whether the operational efficiency can be improved depends on the local conditions and the skill and motivation of the operators. They are mostly very inventive to do the job with as less labor as possible, which should be efficient. In those cases, the safety issue must be considered and watched.

In my professional career (designing, calculating, building, maintaining and operating pneumatic grain- and cement unloaders) I know that the most influencing factor in unloading efficiency is whether you are using the unloader up to its maximum performance capabilities.

This is easily checked by reading the reached vacuum and pressure.

If these readings are below the maximum or designed values, then the unit is underused.

Other parameters can also indicate where to gain capacity.

If discharging is waiting for suctioning, suctioning is the first problem

If suctioning is waiting for discharging, discharging is the problem.

Supply of the installation and performance data of the unit and the pipe routings makes it possible to calculate the installation’s pneumatic capabilities.

If you like, you can use the private messaging feature of this forum.

Have a nice day

Teus ■

Dear DBT,

The increase in suction time can have various reasons.

-Leaking air back into the suction vessel.

That could be through a discharge pinch valve, however, I doubt that this is a reason, because that would show itself in the fact that the pressurizing of that vessel is not possible anymore or at least takes a long time and it would influence the unloading time of the other vessel.

But there is possibly an equalizing valve between the kettles, although, not likely leaking.

I assume that the cement intake valve is a butterfly valve and that one can be worn out.

In that case the vacuum of the suctioning vessel is destroyed by the leaking intake valve from the discharging kettle.

Checking for a leaking kettle is simple.

Pressurize the vessel and just before it reaches the opening pressure, give “Stop discharging”. The pressure in the kettle must now be maintained for a longer period of time. If not, there is some leak.

-Worn out vacuum pump.

I assume that you are referring to pulling 15.2 to 16 inch Hg ( 5225 mmWC to 5500 mmWC) of blower vacuum.

I also assume that a higher vacuum results in lower capacities or oven choking the suction pipe.

Furthermore, I assume the design is a high vacuum design at a design vacuum of approx. 6500 mmWC or even 7000 mmWC

The reduction in capacity at such a low vacuum indicates a worn out vacuum blower.

This can be tested by loading the blower with vacuum by manually closing the vacuum by-pass valve until the spring safety valve opens.

If the vacuum valve is closed and the safety spring valve is not opened before, then the blower clearances are so big, that the internal leakage is far too high.

The air mass flow through the suction pipe at a certain vacuum is then not enough to maintain proper conveying.

The wear of a blower can also be noticed by a too high outlet temperature in relation to the vacuum.

The wear in a blower is almost always caused by cement dust leaking filters.

-The filters

Is your filter alarm a dust alarm or a filter pressure drop alarm?

Clogged filters cannot be the cause of your lower capacity, because that would result in a higher blower vacuum instead of a lower blower vacuum.

If the vacuum that you mentioned is kettle vacuum, that can be caused by a clogged filter at a constant blower vacuum. Check the difference between the kettle vacuum and the blower vacuum.

-Suction nozzle.

A worn hole inside the suction nozzle can short circuit the pick up air, resulting in less capacity and thereby lower vacuum.

If you can sent me the technical data of the installation and equipment (pipe geometry, blower, compressors, tank sizes, filter size), then I can calculate the parameter values as they should be. The differences of the measured values with the design values indicate the type of problems. This approach worked (almost) always with some remarkable results.

If you wish, use the private messaging feature of this forum.

Have a nice day

Teus ■

Dear DBT,

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Teus

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Dear DBT Docksider,

Please feel free to contact us at FLSmidth since we are the supplier of your Docksider. Our Brian Warmkessel has been to your site and can assist with whatever operational issues you have.

Please contact me.

Fred Wuertele

FLSmidth Pneumatic Transport Systems

610-264-6801

610-390-3961

fred.wuertele@flsmidth.com ■

Dear Fred,

The problem with the cement unloader is probably solved between October and now, because I had no response since then.

If you know the unloader and the operating site, why not take the initiative to contact them?

Have a nice day

Teus Tuinenburg ■

dear everybody,

i need to convey powder cement form barge to bank. elevation 7meter (flexible pipe) and length of horizotal 40 meter (steel pipe), 3elbows.

you can help to calculate system and vacuum pumpe.

My email: dcthanh@27mec.com.vn

thank you all.

Doan

Attachments

vacuum central cement model (1) (PDF)

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Dear Doan,

I have calculated your installation.

Using an Aerzen blower type GM 015L with pre-inlet at 4800 rpm as vacuum pump, the calculation result is:

Horizontal length = 38.5 m

Vertical length = 9 m

Nu of bends = 5

Pipe diameter 100 mm

approx. 10 tons/hr at 0.65 bar vacuum to approx 1 ton/hr at 0.41 bar vacuum.

Filter area in receiver = 28 m2 (pulse cleaned)

Using a flexible hose as intake is very hard labor.

Depending on the amount of annual throughput a more sophisticated installation, using a hydraulically articulated suction arm, is advised.

This suction arm can be mounted on a mobile platform.

Have a nice day

Teus ■