How Does Vertical Vibration Concrete Pipe Machine Works?
Vertical Vibration Concrete Pipe Machine uses half-dry concrete as aggregate, the mandrel vibrator and inner mold vibrating together to form the pipes vertically. There are eccentric blocks inside the vibrator located in the inner mold. These blocks rotate in high frequency to generate vibration and the force of vibration passes to the concrete through the inner mold.
There are 3-4 eccentric blocks in the vertical vibration machine along with the vertical shaft. The vibration force generated by the rotation of blocks is right-angled with the axis of the concrete pipes. This force is circumference vibrating, it likes a vibrator which diameter equals to the inner diameter of the pipe, vibrating continuously and form the concrete into shape.
This method is done by the machine to reduce the adhesive property, internal friction, and the engaging force of the particle from the mixed concrete. Along with all these things, it also helps to form a filing structure and to compact the concrete to a high-density level for gaining expected strength and other specifications.
During the process of manufacturing, while adding concrete, the pipes are compacted by vibration force. The upper end of the pipes is made with the vibration force and the hydraulic press force by the joint forming plate. It helps to give the upper end of the pipe a good density, higher strength and good dimension accuracy.
The mold could be removed vertically after production without curing them. The subsidence could happen to the concrete pipes before the initial-set, and they may deform easily, especially the upper end of the pipes. So we should strictly follow the manufacturing technology to make sure that the finished pipe could bear the gravity, and the deformation would not be greater than the tolerance. To ensure the accuracy of the upper end of the concrete pipes, it should be protected with steel or GRP header during the natural curing.
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What is good of this vibration concrete pipe machine?
● This machine is automatic and maintains a high mechanism. With its high frequency, it has helped a lot to save labor time. Keeping this machine in hand, this industry has turned itself from being labor-intensive to a fully technical manufacturing.
● Adjustment of vibration is solely dependent upon the dimension of concrete pipes. So the making of high quality of concrete pipes has become a lot easier.
●Traditional machines, like the horizontal concrete pipe machine, used to have more than one mold for each of the sizes. But this revolutionary machine uses only one mold for each size. Thus the concrete pipes made with this machine are highly accurate in nature.
● This machine is totally Eco- friendly as it has decreased the usage of cementing materials. And half-concrete is really cost effective in comparison to the traditional materials.
● The strength and density of the concrete pipes made with this machine are undeniable. Additionally, the water absorption cannot be more than 6%.
● With only one mold for each size, Vertical Vibration Concrete Pipe Machine has not only reduced the investment expenditure, rather it has made the machine highly efficient for mass production and urgent projects. Now, the number of molds cannot limit the output.
● This machine makes use of natural curing process (30-40℃) which helps to save energy.
● The machine is a multi-tasking one. For example, it can make pipes with basement as well as it is an expert in the making of other non-circular pipes.
● This machine is a savior to the environment.
● It can also produce lining pipes such as pvc lining concrete pipes, steel lining concrete pipe and GRP lining concrete pipes.
● It requires less equipment for the making of pipes. And it has also shortened the processing time of pipes.
● This machine can successfully manufacture pipes with the diameter bigger than 2400mm.
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Bothered by the air-pocket? Here is the solution!
Why there are air-pocket on the surface of pipes made by vertical vibration concrete pipe machine?
The vibration compacting process uses the vibrator for generating vibration and then passing it to the mixed concrete. During this process, the particles of the mixed concrete come closer to each other which extrudes the air out of the concrete. Thus air bubbles come out to the surface of the concrete as well as the surface where the steel molds got attached with the pipes. These air pockets worsen the look of the pipes.
The bubbles which raise up to the surface of concrete are the ones having a specific diameter. On the other hand, the other bubbles, which cannot conquer the conflict with their buoyancy force, remain inside the concrete and thus form the air pockets inside the pipe body.
Now, the question arises, where does the air come from?
The air not only comes from the concrete batching, delivery and filing process; it also comes from the air absorption during the vibration force. How much air gets absorbed into the concrete depends on the vibration technology, which matters a lot to the quality of finished concrete pipes.
The volume of air absorbed into the concrete is depends upon the vibration frequency, the vibration amplitude, and also the mixed concrete matters.
- During the vibration compacting, the higher vibration amplitude results in more air absorption.
- During the vibration compacting, the higher vibration frequency results in less air absorption.
- The longer will be the time of vibration, the more air will be
- The worse will be the surface adhesive between concrete and mold, the more air will be absorbed.
- The looser the concrete, the more air is absorbed.
- The more Viscosity of the concrete, the more air is absorbed.
Solution to the problem.
The most efficient way to decline air absorption while making pipes with half dry concrete is to use the high vibration frequency in lower vibration amplitude, and make the vibration time as short as we can.
Is there any test could support our theory?
We made a test that can completely approve our theories about the influence of vibration frequency to the concrete density.
The tests used same vibration force, same aggregates, but four different vibration frequency to make concrete pipes. We took 3 samples from the top end of the pipe, the middle of the pipe and the bottom of the pipe, and made a water absorption testing. The results are shown below:
From the test above we can learn that:
● Concrete pipes made by Vertical Vibration Concrete Pipe Machine have different water absorption from top to bottom which also becomes less from top to bottom.
● The water absorption in the middle and the top of the pipe body becomes lower with improving the vibration frequency; while the bottom of the pipes vibrates for long, the vibration frequency becomes less effective to the water absorption.
When the vibration frequency is at 4166rpm, the water absorption of middle pipe and the bottom pipe become higher; it is proved that after the high-frequency vibration, the middle section of the pipe becomes completely compacted. Increasing the vibration time does not improve the density of the bottom section of pipes continuously. So, we could use the variable concrete-filling-speed during the production, accelerate the speed of fill concrete when filling the bottom of the pipe and increase the volume of filling concrete, in order to reduce the vibration time of the bottom of the pipe. Slow the concrete filling speed gradually from downside to up to increase the vibration time of the upside concrete pipe, then to balance the density of the concrete pipe from downside to upside.
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The requirement to the concrete manufacturing concrete pipe by vertical vibration machine
When Concrete pipe is made by Vertical Vibration Machine, mold could be removed instantly after production, and it could even be cured without mold (with other machines like spun pipe machine, the pipe have to get cured with the mold). Without the support of the mold, the concrete pipe will deform under the gravitational force until and unless it becomes solid. So in order to prevent the pipe from deforming, the concrete must have enough cohesiveness, the finished concrete pipe will have the ability of self-supporting to bear the gravity without deformation.
From the above, we can learn that the cohesiveness of concrete is very important. From the selection of aggregate to giving it the right proportion - all the steps should aim to improve the cohesiveness of concrete. And the compression of vibration could guarantee the concrete to have sufficient cohesiveness too.
The technology of vibration concrete pipe machine uses high-frequency vibration to make the concrete particles moving, filling the mold and compacting; the upper end of the pipe takes its shape by hydraulic compressing and vibration force. So the concrete for vibration machine should be dry which is suitable for both vibration and hydraulic compacting. The well-designed concrete for vibration machine is easy to compact to the right shape, and has the good cohesiveness, and it will also have fewer air pockets. The end of the pipe is easy to compact to the designed shape in 2-3 mins without air pocket and appearance of stones.
According to your experience and test, the specifications of concrete are below:
- Water cement proportion
Water cement proportion is very important for the mixed concrete, and it matters a lot to the workability. The vibration technology requests the concrete to compact firmly during vibration for higher density; meanwhile, the concrete should be half-dry with no lumps; it could get squeezed to clumps by hands and could be collapsed when you will touch them. Usually, the water-cement ratio is 0.36-0.39
- Volume of cement
The volume of cement affects the bonding strength of aggregate. Improving the volume of cement within certain limits could also improve the strength of concrete along with the workability making it easy to liquefy and flow. But the usage of too much cement will not improve the strength, rather it will increase the cost.
Usually, the cement volume for C30 standard concrete is 320-370 kg/ m; the cement volume of C40 standard concrete is 340-380 kg/ m³; the cement volume of C50 standard concrete is 360-400 kg/ m³. If any chemical or other mineral additives are used in the concrete, the volume of cement could be reduced accordingly.
- Sand percentage
The sand percentage is the main factor to the cohesiveness and workability of the concrete.
Usually, the proportion is 0.40-0.48.
- The volume of sand and stone
The aggregate grading and sand percentage is the main factor to the workability of half-dry concrete. The aggregate grading should be strictly controlled during the production to get high quality and well-designed concrete product while reducing the consumption of cement.
In the production, we should adjust the proportion and aggregate grading according to the aggregate quality, seasonal climate and the dimension of pipes, to meet the required quality.
Quality of mixed concrete has a significant influence to the vibration concrete pipes. Controlling the quality and stability of concrete are the most critical, so it’s better to keep all the material quality stable and it's also better not to change them frequently.
Specification of Vibration Process
The structure of half-dry concrete is very loose. During the vibration and liquify process, the tiny space gets fulfilled with small particles and the concrete become compact squeezing most of the air out of the concrete. The vibration have to be strong enough to let the particle’s move speedily up to the specific limit of velocity to liquify the concrete for getting the ideal compaction. Whether the concrete could liquify or not, depends upon the frequency and the amplitude of vibration, and the other specifications like the quality of cement, water cement proportion, the surface of aggregate, and the aggregate grading, temperature etc.
There is very little cement paste in the half-dry concrete. Low-frequency vibration is not enough to liquify the concrete and make the half-dry concrete flow and full fill the pipe mold. So we have to adopt high frequency and strong vibration to liquify the concrete, and make it flow and get compressed to the designed density.
In the concrete pipe making the process by vibration machine, the diameter is from 15mm to 25mm; the most abundant amongst them is 15mm; If the diameter of sand is within 5mm, take the diameter of aggregate and the energy decrement of concrete into consideration, to make the dry concrete liquify. The most proper annular rotating vibrations should be more than 6000 rpm.
The quality defects may happen to vibration concrete pipe machine and the resolutions
The main quality defects that happened to vibration concrete pipe machine is that the rough surface and the air pockets on the appearance, the pore space inside the pipe body, and the crack of upper end of the pipes. But if we operate the machine properly with gentle care and make the mixed concrete for the production accordingly, all these defects can be eliminated from the machine.
Solutions to quality defects:
1.Make the mixed concrete strictly according to the standard and guarantee the workability of the concrete.
When the mold is released from the concrete pipes, during the curing process, the subsidence could happen to the pipes and cause the pipes to deform. The main reason of this being:
- unstable lifting and striking happened to the mold and pipe during the mold release process.
- the bottom ring and pipe are not completely vertical to the ground.
- pipes are too tall and thin.
- too much water in the concrete.
In order to avoid these defects, stable demoulding is a way to protect the pipe from impacting. Make the ground surface flat enough, and use the accurate dimension of mold. This process is to make sure about the high workability of mixed concrete.
Self-support is an important specification to guarantee the accuracy dimension of concrete pipes. The volume of water for mixed concrete should be adjusted according to the dimension of pipes, material, climate.
Vibration force is the main force to form the concrete pipe. Vibration specification should be adjusted according to the dimension of pipes, and the quality of concrete to acquire higher density, high strength with the perfectly finished product.
3.Coordination of concrete filling and vibration.
Vibration machine uses the rotating belt to fill the concrete while vibrating; the vibration and concrete filling should be coordinated. The vibration specification should be adjusted according to the dimension of the pipe which is being produced; meanwhi,le adjust the concrete filling speed and the volume.
If filling the concrete becomes too fast, the concrete will not be liquified and full fill the pipe mold; the air will not be squeezed out of the concrete because of the continuous process going on and on. The cement paste could not fulfill all the space among these aggregate. And the hole formed inside the pipe body causes the low density and strength of the pipe.
In order to solve this, the concrete filling speed should be different from bottom to top; fill faster in the bottom, while slow down gradually from bottom to top. This helps to completely compact the concrete and improve the producing time circle.
Improve the frequency of vibrator to 6000 rpm or more, to improve the density, strength, and reduce the air in the concrete as less as possible. It will also help you to save energy, shorten the production time circle and improve the efficiency.
4.Time of starting vibration
The vibration concrete pipe machine uses the technology of inner mold vibration which lasts for the whole concrete filling process. The obvious consequence of this is the bottom of the pipe vibration being more than the top of the pipe; and the bottom may even over-vibrate while the top may experience lack of vibration. So, depending upon the specification of the concrete pipe and the vibration of the machine, start the process and fill up about 1/3-1/4 of the pipe mold.
If we start the vibration early without material, the noise will be loud and the vibrator as well as the mold can break anytime by the powerful vibration. on the contrary, If we start the vibration too late, the air in the bottom of the pipe will be hard to squeeze out, and too much air will remain in the concrete while forming the air pockets, holes, and reduce the density of the whole pipe.
Unlike the bottom of the pipe, the vibration for the top of the pipes are not that longer. In order to improve the density, strength and form the joint of pipe, we use hydraulic pressing while vibrating. During the operation, the pressing should be slow and gradual avoiding any sudden press force to the top of the pipes.
The main character of vibration pipe machine is that
- Using half-dry concrete
- Removing the mold instantly after production.
So the concrete pipe made by vibration machine requires more attention during the curing process after production. Protective-header must be set on the top joint of the pipe after removing out the mold. Cover the pipe with the plastic cover to prevent water from steaming away. Natural curing and steam curing are the options according to the climate and temperature.
7.Quality of steel mold
The vibration force of vibration concrete pipe machine is passed to the concrete though the steel mold; so the steel should be of good quality, light-weight, and should have good resilience power.
The design of steel mold is quite important
- The reinforced bar of outer mold should be in the right quantity and well-designed position
- The steel should be of lightweight and have good resilience power in order to make the concrete liquified by the most efficient vibration, to guarantee the uniformity of the pipe quality.
- The dimension should be accurate as designed, and should be leak proof.
- The surface of mold should be smooth enough, the welding line should be polished with no dent and accurate dimension. Make the cone with a diameter of 3mm to guarantee the mold to be removed smoothly without resistance.
8.Installation of the machine
The installation of vibration pipe machine has significant influence to the vibration efficiency. The foundation should strictly abide by the designs, to guarantee the accuracy of the machine and the vertical of mold.