how are you feeding the PVC powder into the system ???? ■

Dear pvcnewbie,

More info is needed.

Particle size of PVC powder

Are you referring to a pressure- or a vacuum system?

What are the inner diameters of the pipeline

At what distance the diameter change is located?

Is the air mover a positive displacement pump or a fan (approx. 12 m3/min)?

What is the air displacement of the compressor?

When conveying 400 kg/hr, what is the conveying pressure or vacuum)?

What is the volume of the rotary seal and the rpm?

Awaiting your reply

all for now

Teus ■

Dear newbie,

The PVC powder should have a suspension velocity of approx. 2.5 m/sec

This requires an intake velocity of approx. 10 m/sec

For a 4” pipe this corresponds with a blower displacement of approx. 0.125 m3/sec at 0.4 bar vacuum

According your information, the velocity is approx 21 m/sec with clean air, resulting in a blower displacement of approx. 0.155 m3/sec

Using your information, I calculate a solid friction factor for 400 kg at 0.4 bar vacuum, which is approx. 10^6 times higher than for other installations with a comparable material.

Also the exhauster data seem to be not in accordance.

I could not find a Roots blower in the gamma of Atlas Copco and the power of 16 kW also seems too high for a Roots blower of only 0.155 m3/sec at 0.4 bar vacuum.

I suggest that you check your data again and if they are correct, you should check your installation for defects or even blockages.

What is meant by “all valves running”?

I am interested

Teus ■

Hi guys,

Atlas recently bought up a Czech PD blower mfg so it is possible that this is a PD blower package. But they also make dry screws and turbos. Can you find out the model number and RPM of the blower?

How new is this system and has it ever worked differently for the worse or better?

Teus is correct in saying that 16 Kw is bit much power consumption wise. For the two volumina this should be more like 7.5 - 10 KW. ■

Dear newbie, hi Ralf

We are getting closer to the solution, I think.

First of all.

The compressor ZL1200 might be a blower mentioned by Ralf.

I could not trace it back on the website of Atlas Copco.

It might be a 1200m3/hr blower (# 20 m3/min)

If so, this could explain the 16 kW.

But, then the design velocities are far too high and should be re-evaluated.

Nevertheless the system should work properly, although with a far too high energy consumption and possible damage to the pvc powder.

My original calculation of your system , using a comparable product loss factor to previous installations, told me a capacity of approx 5 tons/hr

The same magnitude as your mentioned 4000 kg/hr.

It now looks like, that the rotary lock at the end of the conveying installation is leaking far too much air.

Not enough air is then left for the conveying system and sedimentation starts in the beginning of the pipeline as the air velocities are the lowest there.

Two things to check.

Blower data in m3/min and pressure.

Rotary lock condition at receiving hopper.

Let us know

Teus ■

Hi pvcnewbie, ■

Hi pvcnewbie,

All I can say is that your blower provides 14.5 to 15.7m3/min inlet air flow at 400mBar vacuum at the two blower speeds you mentioned. It is a DN100 / 4" discharge blower package so that matches the overall picture. That flow is much more that Teus calculated you need. Now comes the parts any of the bulkaholic experts aggree on: This is only a problem if the system was not designed for this condition or the material. Or is it a maintenance item after all?

I would go on by reviewing your conveying history and trend your material consistency along the way with it. If this turns up nothing you will have to bite the bullet and painstakenly record all operating conditions and the system layout as well as the material make up. Did you contact your system OEM? That would be my first trip in asking for their assistance in solving this issue.

If all else fails make good use of this forum to ask for free or paid consultancy in trying to figure out how you can alliviate the issue (or better issues). There are usually always multiple issues culminating into a bigger problem. Perhaps you can figure it out all by yourself.

Just make sure your research captures accurate operating conditions. The old adage of garbage-in-garbage-out will otherwise bite you badly. ■

Hi pvcnewbie,

I just remembered a post a while ago where someone had terrible plugs in a 4" line and they dicovered it had not been the system but ambient air and mositure had gotten through rubber pipe coupling and flanges which cause material build up in the ppes around those areas inside the pipe thereby causing the plugs. Did you ever look at the cleanliness of your pipes? ■

Hi newbie, hi Ralf,

I calculated the system now as built, with an Aerzen blower type GM 15L

Look at the pdf file attached.

Note the very high velocities etc.

Enjoy it

Teus

Attachments

newbie (PDF)

■

Hi Teus,

Cool. The high velocity causes higher than necessary system power consumption, but does this cause the plugs? ■

Hi Ralf,

I don't think so.

Due to the high velocities, the particles are moving far apart from each other and the loading ratio is not high (8.9).

Certainly not when the conveying rate is only 400 kg/hr.

That is why I think that there is conveying air leaking thruogh the airlock, causing too low velocities in the pipe line, resulting in sedimentation.

If my suspicion is correct, then the airlock must be in a terrible condition.

We will hear

Are you happy with your new president?

We expect a lot from him.

take care

Teus ■

Hi teus, ■

Hi Teus,

Sorry I pushed the send button too early again. A bad airlock would coincide with the system having gotten progressively worse.

I am ecited about having a new president. I am proud of the democratic system having worked as well as showing that anything is possible in the USA. ■

So you could be causing the slugs by loading the line with too much product? Perhaps I am misunderstanding the blowing seal you are talking about. What does that look like or which mfg is it? ■

Dear newbie,

Increasing the rpm of the blowing seal increases the material feed and thereby the SLR.

SLR = Solid loading ratio

If the SLR becomes too high, then the pressure drop also increases.

The vacuum on the blower increases also and as a result the blower displaces less air mass flow.

Then the air velocity at the beginning of the pipeline drops and can become too low.

Sedimentation is evident and eventually clogging.

As your installation performs worse and worse by time, there is something in your installation that is changing.

The first item, I think off is the rotary lock at the end of the pipeline underneath the filter.

If that rotary lock leaks too much air, the air mass flow along the pipeline becomes less.

This effect is increasing with the vacuum.

In that case, it is still possible to convey low rates at low vacuums, because then the airflow through the pipeline is still just enough.

That is why I asked you to inspect that rotary valve at the end for proper condition.

Additionally, it can be, that your filter is broken and that dust destroyed your blower clearance.

The internal blower leakage reduces the volumetric efficiency of the blower with the same effect.

Check your installation first.

success

Teus ■

Dear newbie,

Does it mean that there are 4 rotary locks paralel (4 silos) or are the silos under vacuum whe being filled?

In case there are 4 rotary locks in the system and when one is working, the others should be isolated from the system.

Otherwise the not used rotary locks would still contribute to the leakage,

The varying performance couls be caused by the feeding through the blowing valve.

Suppose the following.

Increasing the rpm of the blowing valve from zero upwards works fine.

You can reach 1500 kg/hr. (at approx 0.25 bar vacuum, see screen shots))

At this pressure the sedimentation is not hampering the performance.

Now you want to try a bit more.

Suddenly the increasing vacuum results in sedimentation, whereby the pipeline gets clogged.

The only way to start again at 1500 kg/hr is purging the pipeline and increase the feeding from zero up.

Still advising to check your system.

Take care

Teus ■

Oh my. That detail would have been really important to know up front. I am assuming this involves diverter valves? This means you have 4 airlocks? Do you have a flow schematic of the complete system? ■

Dear newbie,

Your additional information underlines the advise to go to the installation and check everything.

If you compare (and if possible calculate) the performance of the 4 pipelines, then you get insight of the differences.

If the found differences cannot be explained theoretically, you have to start further investigation in the installation.

I am sure that there is a lot of information, hidden in the installations operating parameters.

It only needs to be evaluated.

Apart from the 4 rotary locks, you now have also to check the functioning of 4 butterfly valves.

Success

Teus ■

Hi Teus

Great Salutation

After long time it comes to have the interction with you.

well what makes me to come on conclusion is the filter . As spelled by our first threader , he is using filter with the problemistic situation that ie Pressure drop across the filetr. In my view it could be quite abvious to accept that if there is some filter of specific area , would create some delta P . Problem been outlined is very simple, and requires some considerable concern over the filtaeration area, i mean could have possible that filter may get chocked

As if something i would make as a qualified guess, is the filteration problem.

Perhabs it is been experienced due to couple of the reason

1) As enlightened above

2) User should check the design parameter of pipeline layout.Lets be a more specific that Compressor has nothing to make any cause as is not being effected by any factor. What males the problem to be happen is something related to pipeline design

Indeed the problem is require steep attention but could be taken care

Cheers

All for now.....................

Rahul Chuabey ■