As-Salaam alaykum MYousef,

You can succesfully use a pipeline pig for your

pnuematic cement pipeline very easily.

1. You must install a pig launcher tube at one end of the pipe and a pig receiver to remove it from the pipe.

There are many companies in your part of the world that do pipe line pigging work so the installation is no problem if you have adequate room for the pig launcher and pig retriever-before I forget it they clean bends in pipe very well when used.

2. The added benefit is that you could do it several times a year your self to clean the pipe and remove build up material.

The pipeline cleaning pigs have a proven track record and work very well.

I have one question though, why do you have 4 compressors feeding air to a screw pump?

Or are you using an air motor to driver the screw pump if so equiped?

Are you referring to an auger in the pipe as a screw pump?

I am assuming you are using a screw type blower to move cement- or am I missing something? Are you adding to the make up air flow to the blower to reduce the intake load on the screw pump and maintain a balanced air flow? to the thew transport pipe.

If the above is the case your blower is too small.

Regarding the air dryer anytime you have compressed air in any service application you will have temperature extremes from cold to hot and it will increase moisture in a compressed air system.

It also depends on how much moisture is in the air entering the system.

How often do you manually drain the air tanks for your ompressors and change air filters and the air oil separators? I am assuming you are not using piston type compressors.

To do this properly you should shut off all your compressors lock out the electrical panels to prevent accidental restart and drain the air tanks with the drain valves used in the bottom of the air tanks?

If you do not have drain valves on the bottom of the air tanks you have big problems and you need to install them to drain moisture from the air systems as this will increse the corrosion of the tank body.

To do this properly you must and I repeat must lock out the electrical power and drain off all the compressed air in the system-be sure to wear eye protection and hearing protection when doing this.

This must be done to be sure that no pressure exists in the system as it can and will cause injuries from the air blast if it is not drained properly and it can puncture human skin and cause death.

If possible and it is highly recommended that the drain valves be left open overnight to allow all the moisure to drain out of the system as the droplets of moisture will fall by gravity to the drain valve of each tank.

Air dryers are a good idea for any system and they are easily installed and should be installed in your systewm to reduce moisture and corrosion.

Assuming you have plenty of room you should really consider installing a one main air tank for your system where all four of your air compressors feed their air volume into one storage tank and install a big enough air dryer to handle the load or a battery of them in series parallel in the air delivery line or lines to increase the efficiency of the air dryer or dryers.

This also will help reduce the potential for corrosion of the air delivery lines and in the cement delivery pipe line.

If I have missed something or misunderstood something please tell me. If you have a diagram for your system you can mail it to me at:

lzaharis@lightlink.com ■

Dear Mr M Youssef,

Although your description is very limited, I understand the following:

12”pipeline – 300 m long

performance 100 tons/hr cement

4 compressors (air flow not given)

pump X-250 ( I assume that you operate a Fuller-Kinyon pump size 250)

Because you mention a pigging procedure and an air dryer, I think that you have problems with caking pipes and that you suspect condensation to be the problem.

Supposing that I am right, know that this can be calculated very easily.

Even up to the amount of cement, that is bonded with the moisture in the conveying air is calculable.

I would be glad, to make this calculation for you and find out whether this installation is a good design.

The additional data I will need are:

horizontal length

vertical length

number of bends

(or a description of the geometry of the pipeline, fi isometric sketch)

air volume of each compressor

how many compressors are operating

convey air after cooling y/n

capacity

conveying pressure

ambient temperature at compressor intake

cement temperature.

after that, it is a piece of cake.

If you have reasons to prefer this calculation outside this forum, e-mail me privately

best regards ■

Dear Mr Youssef,

Your cement conveying case is very interesting.

That the screw pump drive is failing at 100 tons/hr and works well at 85 tons/hr, is understandable because at 100 tons/hr the conveying pressure is higher and thereby the power demand of the screw pump.

From your description, I conclude that the 3 compressors are running at 1.9-2.3 bar(o), while the conveying pressure is 1.6 bar(o).

That means that there is a pressure loss between the compressors and the conveying installation of 0.3 – 0.7 bar.

The cement temperature of 120 Centigrade is high, causing also a high conveying air temperature, as the cement dictates the air temperature, due to the high heat content of the cement compared to the heat content of the air.

I calculated the installation, you described, giving the following output:

Lafarge Egypt youssef d 03-21-2006

Pressure discharge Cement

3 pumps running

Convey length = 256 m

Nu of bends= 7

Pump vol = 1.77 + 1.77 m^3/s

q-convey = 1.78 m^3/s

Dia begin = 274.3 Dia end = 274.3 m

Pipevolume = 15.12 m^3

Pipeline

Press. Cap. mu . v-begin v-end kWh/ton res.time

1.750 191 24 16.6 43.5 1.47 13.01

1.500 172 22 18.3 43.5 1.43 12.00

1.250 151 19 20.3 43.4 1.41 10.97

1.000 127 16 22.9 43.4 1.43 9.93

0.750 96 12 26.2 43.5 1.56 8.91

0.500 56 7 30.6 43.7 2.10 7.87

As you can see, the calculation gives a higher capacity then you stated.

180 tons/hr at 1.6 bar instead of 85 tons/hr at 1.6 bar.

The calculation gives 85 tons/hr at 0.672 bar(o)

Could it be, that the 1.6 bar, you measured, is before the orifices in the screw pump and that the orifices take about 1.6 – 0.672 = 0.928 bar. explaining the difference?

I also compared the installation with some local installations, I am familiar with and concluded that 85 tons/hr at 1.6 bar(o) at a 12” pipeline is very low.

Or is the pipeline diameter smaller, due to wall caking.

There is certainly something to investigate here.

As the calculated air velocities, using 3 compressors, are very high, I also calculated for 2 compressors.

That should work also very well, saving 30 – 40% of energy. (and wear)

Lafarge Egypt youssef d 03-21-2006

Pressure discharge Cement

2 compressors running

Convey length = 256 m

Nu of bends= 7

Pump vol = 1.18 + 1.18 m^3/s

q-convey = 1.19 m^3/s

Dia begin = 274.3 Dia end = 274.3 m

Pipevolume = 15.12 m^3

Pipeline

Press. Cap. mu . v-begin v-end kWh/ton res.time

1.750 187 35 11.0 29.3 1.00 19.81

1.500 171 32 12.1 29.3 0.96 18.32

1.250 153 29 13.4 29.2 0.93 16.83

1.000 133 25 15.1 29.2 0.91 15.31

0.750 108 20 17.2 29.2 0.92 13.78

0.500 76 14 20.1 29.1 1.03 12.19

Regarding the issue of moisture, there should be no problem at all, because the high temperature keeps the relative humidity in the pipe line below 15 and no condensation of water occurs.

p-intake (absolute)<1> = 1 bar 03-21-2006

temperature intake ... = 30 Degr.C.

relative humidity .... = 100 %

Water vapour pressure ...................... = 0.04186

Dry air pressure ........................... = 0.95814

Dry air density ............................ = 1.1162

Dry air specific volume .................... = 0.89588

Water-mass per 1kg of dry air .............. = 0.02717

Total mass of 1 kg of dry air + water ...... = 1.02717

Intake density ............................. = 1.1465

p-local (absolute) ... ... = 2.75

Temperature local .Degr.C. = 125

Relative humidity local .................... = 1 %

Water vapour pressure local ................ = 0.01910

Dry air pressure local...................... = 2.73090

Dry air density local ...................... = 2.4221

Dry air specific volume .................... = 0.41287

Water-mass per 1kg of dry air .............. = 0.02717

Total mass of 1 kg of dry air + water ...... = 1.02717

Local density .............................. = 2.4879

NO CONDENSATION

Note:

-I assumed cement of an average particle size of 50 micron, with a floating velocity of 1.8 m/sec.

-Further investigation is necessary, to find the difference between calculation and practice, because the calculation indicates that a better performance is possible.

Sofar for now. ■

dear Mr Youssef,

The condensation calculation is not a spreadsheet program, but a Quick-basic program.

But if you give the condensation conditions, I can calculate for you.

The reason for the fact that there is no condensation, is that the pressure is not high enough at the existing high temperature of 120 °C.

Condensation starts when the conveying pressure is 2.75 bar(a) (1.75 bar(o)) and the cement temperature drops below 49.5 °C.

In case the pipeline is of duty and no air is passing through, only the resting air can condensate when the pipeline temperature is cooled down below the intake temperature of that air.

With a pipe volume of 15.12 m3, that can only be a very small amount of water.

Maybe you should check the pipeline for leakages, where water can enter.

Seal the pipe ends off, pressurize it to f.i. 4 bar(o), close the filling valve and monitor how long it takes before the pressure disappears.

Pigging the pipeline, when it is blocked by water in the pipeline, that has bonded cement to concrete, is, I am afraid not feasible.

You can also measure the empty pipeline pressure when you are blowing a known amount of air into the pipeline. If this empty pipeline pressure is too high, it tells you, whether the pipeline is blocked or partly blocked.

success ■