Essential equipment for concrete pipe manufacturing

concrete pipe machine

Concrete pipes are widely used for their features of high strength and durable. More and more cities using large diameter concrete pipes as the utility tunnel instead of drainage underground while cable interlacing in the sky. As the development of industriousness and the mechanization, more and more factories adopted fully automatic plant instead of the traditional machine which uses more labor than the current system. Robotized by automatic accessories makes the plant more industrial, but the most essential parts for concrete pipe manufacturing remains.

What is the essential equipment for concrete pipe manufacturing?

Concrete pipe making machine.

Sure thing that this machine is the significant machines to make concrete pipes. There are several different machines which equipped with different technologies, centrifugal concrete pipe machine, roller suspension concrete pipe machine, the vibration concrete pipe machine, vertical concrete pipe machine and the radial press pipe machine.

Centrifugal concrete pipe machine is the only one uses wet concrete as the material, factories gradually abundant this process because it’s un-ecofriendly, and uses a lot of cement compared with the half-dry concrete technology. Labor cost is another reason people may dismiss this machine as we all know that labor cost is going high these days.

horizontal concrete pipe machineRoller suspension concrete pipe machine is invented by two engineers in AU, it’s still widely used in Asia for its simple structure, easy maintenance, and simple operation. However, this machine isn’t the perfection for mass production. As we can not open the mold instantly until the concrete becomes hard, it takes at least 8 hours to use the same mold for the next production cycle. Way to solve this is to have more molds for each size. The total investment will raise high when multiple molds are used in the plant.

Vertical concrete pipe machine uses the vibration technology, to compact the concrete to the maximum strength and density, and liquefy the cement paste during the production, it’s considered to be the most quality machine to produce the concrete product. Half-concrete as aggregate and after the high-frequency vibration force, the mold could be removed immediately after production, that enables us to have only one mold for each size. Because of the adjustable vibration force in this machine, the same machine can make concrete pipes, box culverts, manholes and other concrete products as designed.

Wire cage welding machine for concrete pipe manufacturing

Automatic wire cage welding machine is necessary for mass production. With only one worker’s operation, this machine could weld different sizes of wire cages in short time we can imagine.

 

Concrete batching plant.

For the traditional machine like roller suspension type, JS750 & PLD1200 batching plant is enough for use. But for the vertical vibration concrete pipe machine, the best choice would be the Planetary mixer. If the pipe plant is designed for automatic working, then the central controlled batching plant is the option.

Lifting equipment.

Crane plays an important role in mold lifting and pipe transportation. The span of the crane should cover the whole active area of the pipe plant. As the span and other specification of the crane are hard to be amended after installation, so the whole factory layout design should be made at the start.

Boiler.

The steam heat generated boiler used to shorten the hardness time of the concrete. It’s an important tool for making pipes in low-temperature area and in the urgent civil project. The boiler heat could make the concrete pipes to 70% strength in 4 hours or even more short. The capacity of boiler depends on the whole plant and the daily output.

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RCC Spun Pipe Manufacturing Machine

RCC spun pipe manufacturing machine is widely used in civil project and road construction, using the half-dry concrete as aggregate, compact the concrete into designed shape and sizes with the spun pipe making machine. The production cycle for each pipe could within 25 min, it's much efficient than the traditional manual process.

Proportion for RCC spun pipe manufacturing.

The cement, sand, stone is the main material for the aggregate, and the detailed proportion can be made according to the local standard, here are the details you main consider: concrete specification

The principle of pipe machine and the manufacturing manual.

Rcc spun pipe manufacturing machine is popular for its simple structure and easy maintenance. Consisting of machine structure, motors, roller, front frame, belt and control panel, assembles with different sizes of molds to make specific dimension of concrete pipes.

The steel mold rotates together with the roller and mold fills concrete into the high-speed spinning mold. the spinning force generated by this process compacts the concrete onto the inner wall of the mold. When the concrete thicker than the mold, the roller press the concrete in high strength. The concrete pipes forms during this process, spinning and compacting until the pipe becomes completely compacted and gained the smooth surface.

The main manufacturing flow is, concrete batching and mixing, delivery, start the pipe machine, adjust the rotating speed to 500rpm, then start to fill the concrete into the mold, turn the rotating speed to 1200rpm gradually to get concrete pipes compacted. Stop the machine when inner surface seems nice and smooth, lift the mold to the curing area. The steel mold cannot be removed until the concrete become hard enough. Water spreading curing still needed after the pipe in the stock area.

Quality issues may happen during the manufacturing process.

RCC spun pipe manufacturing machine is easy to operate, but the quality of the pipes mainly depends on the operation of the workers, unstable of the quality issue can happen is the worker is not experienced.

1.The inner surface is not smooth and even enough. why is this happen? The unconstant concrete filling could cause this problem. the resolution is filling the concrete in constant speed, when the roller touches the concrete, stop the filling and gradually turn the rotating speed to 1200rpm, to generate the centrifugal force and compacted the concrete, the pipe could acquire the high strength and density in 5-7 min.

2. The out surface is not smooth. There are two main reasons cause the defect of the pipe. The first one is the dry cement paste. Workers should clean the inner surface of the steel mold after demoulding to make sure there is no paste glue on the mold surface. The other reason causes the rough surface of the pipe is the concrete is too dry. make the concrete proportion strickaccordingg to standard, and shorten the delivery distance during production to prevent the water from evaporating.

 

 

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Tips for Concrete Pipe Installation

Concrete pipes have been playing an significant role in underground pipe line, installation of concrete pipes is quite common in civil projects. Here are some tips may help you to improve the installation efficiency during the project.

concrete pipes
  1. Seals for pipe joint. Usages of rubber rings at the joint of the pipes instead of rubber strip.
ditch

2. lay the pipes immediately after the ditch is made, and backfill the soil instantly after the pipes is well installed. In some civil project, the pipes installs long after the ditch are made, install the pipe prompt after the ditch is made, is a better way.

concrete pipe lifting

3. There is lifting hook on the excavator , lifting after excavating to improve the efficiency.

lifting of concrete pips

4.Timbering could be used during the installation. It is not necessary to use the timbering when the ditch is not deep. However, the timbering will helps a lot when install in deep ditch. Two sides timbering and the support of the steel tube is easy to make, but convenient to use.

5.The gutter channel on the bottom of manhole base is precasted.

precast manhole

6. Use the laser locate during the straight installation and total station during the reverse installation.

Concrete Box Culvert Manufacturing Process

The concrete box culverts are widely used in utility tunnel. How are the box culverts made?  The concrete box culvert mold is the main facilities during the manufacturing process.

Wet-casting and dry-casting are the main methods have been adopted worldwide at present.

We-cast concrete box culvert mold-Horizontal type.

The wet-cast concrete box culvert steel mold uses the inner mold stick bar to open and shut, it's easy to operate and de-mold.

 

We-cast concrete box culvert mold-Vertical type.

This method precast the box culvert vertically. The mold is designed to collapsed type,

with the connection of steel rod, it's easy to assemble and remove.

 

The out mold runs on the rails, which is very easy to open and shut.

Dry-cast Concrete Box Culvert Mold

Using vibration machine to produce concrete box culvert become more and more common, the same vibration machine can be used to make circular pipes and rectangular box culvert.

Another method to make box culvert is vibration table. The vibration table and dry cast concrete box culvert mold is suitable to make small concrete products.

Comparision of different concrete box culvert mold

  1.  wet cast concrete box culvert mold horizontal type is very suitable to make small box culvert, the mold is easy to assemble and open, the finished culvert has the feature of the nice surface, and small enough to easily transport.
  2. wet cast concrete box culvert mold vertical type can make concrete box culvert with different joint, to meet different requirement of varies projects; this mold is ordinary to make large concrete box culvert.
  3. vibration concrete box culvert mold use the half-dry concrete as aggregate, the finished product has high density and strength, and the mold removes instantly after production. This is very perfect for mass production and urgent civil projects.

Concrete box culvert manufacturing process

  1. Steel bar frame welding
     
  2. Lifting the steel frame to the box culvert mold.

3. Assembling the mold

4. Filling Concrete

5. Curing process

6. Demoulding

 

7. Finished Product

 

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Things You Should Know About Horizontal Concrete Pipe Machine

horizontal concrete pipe machine

How Does Horizontal Concrete Pipe Machine Work?

concrete pipe machine drawing
drawing of the roller suspension concrete pipe machine

The horizontal concrete pipe machine, also called roller suspension concrete pipe machine. The steel roller is driven by the motor, rotating at high speed along with the mold. Filling the concrete into the steel mold, the concrete spinning at high frequency, spread on the inner surface of the mold. With filling concrete, the thickness of concrete become thicker and thicker and starting compacted by the steel roller. Compacted with roller press and centrifugal force, the concrete forms the pipe shape and gains smooth surface.

The specification of horizontal concrete pipe machine is significant to the finished concrete pipes, the machine should be designed according to the pipe standard, accessories machinery, steel mold. One horizontal concrete pipe machine makes 3 or 4 specifications of pipes, according to the production experience, specifications of horizontal concrete pipe machines see below:

Diameter Span
(mm)
Pipe Length
(mm)
Roller Diameter
(mm)
Motor Power
(mm)
300-5002000-250011010
600-10002500-300025030
1200-15003000350-45060
1600-20003000450-50090
2200-24003000500-550120

How do we work out this? Its according to the roller and diameter. Roller: diameter=1:4~1:5, the smaller the roller diameter ratio, the smaller contact surface between roller and concrete, the bigger of the pressure; the bigger the roller diameter ratio, the smaller pressure between roller and concrete. However, if the roller & diameter ratio is too small, the concrete would difficult to form the pipe shape, and the defect may happen.

Pipe Diameter
(mm)
Rotation During Filling
(R/Min)
Concrete Filling Period
(Min)
Rotation
During Rolling
(R/Min)
Rolling Period
(Min)
300130-1403--5100-1102--3
400
500
600120-1304--690-1003--4
700
800
900110-1205--780-904--5
1000
1100
1150100-1108--1075-856--7
1200
1350
1400
1600
180085-9010--1370-808--10
2000
220070-7512--1560-7010--15
2400

Concrete specification for horizontal concrete pipe machine

  • Cement. High-early-strength portland cement is the priority to concrete pipes, the initial setting time should less than 100 min. In order to improve the production efficiency, rapid hardening sulphate cement is better than others in the winter season.
  • Sand. River sand which fineness modulus between 2.2-2.3 is good for concrete pipes, the silt content should within 2%.
  • Stone. Stone for horizontal concrete pipe machine should not too big, if the diameter of stone is too big, the cement and sand is not easy to full fill the space between stones, and the concrete pipe is hard to be compacted to high density and strength. The diameter of pipes should not too small too. Its good to the surface and the permeability resistance using small stone, but this will reduce the strength of the pipes. The best way is to choose the appropriate aggregate proportion, to improve the density and strength and gain the smooth surface at the same time. For large diameter pipes, the diameter of stone among 5-25mm; medium diameter of pipes use stone among 5-20mm, for small diameter of pipes, the diameter of stone should among 5-15mm.
  • Mineral admixture. Mineral admixture like coal ash, slag power matters a lot to improve the workability of concrete, and improve the durability and permeability resistance.
  • The concrete ratio for horizontal concrete pipe machine see specifications below.
Strength ClassCementSand
Fineness Modulus
Stone (Max Diameter)
mm
Workability
(S)
Mineral admixtureRatio
(cement:sand:stone:water:coal ash)
C30P.O42.52.3--3.02520--40coal ash1:2.54:3.97:0.38:0.12
(300:761:1191:114:35)
C40P.O42.52.3--3.02520--40coal ash1:2.07:3.52:0.39:0.14
(340:703:1198:132:46)

Curing of  horizontal concrete pipe machine

The concrete pipes made by horizontal concrete pipe machine cure with the mold together. The inner mold is circular and less water in the half-dry concrete, so the period of warm-up and cooling down will be shorter.

Curing
Process
Pre-curingHeat Upconstant
temperature
Cooling
Time(H)>235>2
Temperature
Portland
Cement
3535-7575±5to normal
temperature
portland slag cement4040-9595±5to normal
temperature

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Lined Concrete Pipe Making Machine

Corrosion-resistant Concrete Pipes

Concrete pipes are widely used in sewer drainage system. However, the sulfuric acid from wasted water can make the concrete pipes fracturing, to improve the lifetime of the underground concrete pipeline, corrosion-resistant concrete pipes are widely produced during these years, and PVC lined concrete pipes are common to see these days.

 

Lined Concrete Pipe Making Machine

concrete pipe machin
concrete pipe machine

Vertical concrete pipe machine is suitably qualified to make PVC lined concrete pipes, by vertical vibration force, the cement paste could completely cover the plastic stripe, and get the high tensile resistance. The lined concrete pipe manufacturing process is similar to the ordinary concrete pipes, but the concrete should more liquid, slow down the concrete filling speed and vibration longer than ordinary pipes.

Follow the regular making process after put the PVC lining to the inner mold.

 

 

The main material of PVC lining is polyvinyl chloride, there are two shapes of line.

 

Testing of PVC lined concrete pipe

  1. Strength testing. Strength testing of PVC lined concrete pipes is no difference with reinforced concrete pipes.
  2. Leakage inspection of PVC line. Edm machines are the professional tools to inspect the leakage. Testing with this machine, when there is spark appears between the PVC lining and steel broom, that proves there is a leakage.
  3. Tensile resistance testing of PVC lining. Tensile resistance test to the PVC lining is necessary, and the tensile resistance strength should no less than 14N/mm.
  4. remanding of PVC lining. When there is a small broken like small hole or scratch, we could weld PVC patch to the broken area, and the patch should 12 mm bigger than the broken area in diameter. When there is a big broken area, the best way is to cut off the broken part, and pain glue to the concrete put on the PVC patch and then weld them together.
  5. Special tool or lifting tool should be used during delivery or transport in case any damage to the PVC lining
lined concrete pipe manufacturing
pvc lining concrete pipes

Connection Of Lined Concrete Pipes

There are two ways to connect the lined concrete pipes.

  1. overlap joint. overlap the inner PVC lining when joint pipes, and weld together with fuse machine, the welding width should more than 500mm. The detailed connection sees drawing below.
  2. Butt Joint. Butt joint connects two ends together after the antiseptic treatment to the pipe ends. Antiseptic treatment material like coal tar epoxy, and the thickness should more than 0.2mm. The detailed connection sees drawing below.

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Vertical Vibration Concrete Pipe Machine Productin Manual

vertical vibration concrete pipe machine

How Does Vertical Vibration Concrete Pipe Machine Works?

vibrator
vibrator for vertical vibration concrete pipe machine

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.

  1. During the vibration compacting, the higher vibration amplitude results in more air absorption.
  2. During the vibration compacting, the higher vibration frequency results in less air absorption.
  3. The longer will be the time of vibration, the more air will be
  4. The worse will be the surface adhesive between concrete and mold, the more air will be absorbed.
  5. The looser the concrete, the more air is absorbed.
  6. 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:

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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:

  1. 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

  1. 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.

  1. 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.

  1. 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.

2.Adequate vibration

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.

5.Hydraulic Pressure

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.

6.Curing process

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.

Precast Concrete Manhole Design and Manhole Making Machine

manhole making machine

Introductin of Precast Concrete Manhole

The precast concrete manhole is widely used for its high density and strength, antiknock characteristic and impermeability are much much better than the concrete block manhole.

A manhole system consists of: the manhole cover, manhole base, manhole ring, and manhole top. The manhole body is ordinary circular, but it could be made to rectangular, flabellate, and in other irregular shapes too. The height of manhole could be adjusted by manhole rings to meet requests of different projects.

manhole making machine
manhole making machine

1. Manhole Top

There are different kinds of manhole tops such as: cylinder-shaped, cone-shaped, and horseshoe-shaped. When the manhole rings are normal size like 700mm, 800mm, cylinder-shaped top is commonly used. When the manhole rings are 1000mm, 1200mm, 1500mm, the cone-shaped top is an option.  When ladders are necessary for people to go inside of the manhole, the horseshoe-shaped manhole is considered the better option.

deisgn of manhole

2. Manhole Ring

There are manhole rings connecting the manhole top and basement, and manhole rings are used to adjust the depth of manhole too.

3. Manhole Base

Manhole base is the functional parts of the manhole system, and its dimension affects the function of the manhole system.

Ordinary there are to shapes of manhole base, circular and rectangular. Circular manhole base is easier to produce, and pipes can be inlet in 360°, but it takes more maximum plane size. Rectangular manhole base is commonly used in large pipelines and right-angled pipelines.

manhole and pipes

The distance between top of manhole base and the edge of inlet pipes should more than 150mm, the distance between the base bottom and the edge of inlet pipes should more than 50mm, and the distance between pipes should more than 100mm when there are several inlet pipes needed.

maholes

Concrete manhole with base: the base is precasted together with manhole body, reduced the lifting work during installation, but not very convenient to install.

manhole with base

Manhole without base: the manhole bottom base and manhole are cast separately, and installed together,

manhole without base

The most inconvenience during the project is that the manhole is difficult to lift and install. So the design of the manhole item should be focused on reducing the weight, the assembly of manhole system could be adjusted according to different project, larger manhole base could be made in half and half to make it easier to lift and install, and to meet the different requirement in different geographic places.

different manholes

The inlet for pipes in the manhole base can be circular shaped, U shaped, and blind pit. The blind pit is kind of reserved hole, only half depth of the inlet, need to open when needed.

inlet of manhole

The gutter is ordinarily designed in the manhole for the request of current fluency. The gutter can be cast together with manhole base or cast separately, and assembled together when necessary.

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4. Ladder

The manhole as a trance to the underground pipeline, installation of ladders are necessary, and the ladders should be safe, durable. There are steel ladder and steel reinforced plastic ladder, the steel ladder goes rust easily and is replaced by the other one gradually.

5. Joints of Concrete Manhole

Joints between the manhole elements are almost the same with concrete pipes, there are flat joints, as well as male & female joints. The seals for the gap are cement plaster, factice, and rubber seal.

joint of manhole

Concrete Manhole Manufacturing

There are ways to manufacturing concrete manhole, by dry cast vibration machine and wet cast manual mold. are the most common two methods.

 

concrete manhole mold

Wet Cast Manhole Mold

Wet cast manhole mold uses the steel mold to manufacturing precast manholes, using wet concrete as aggregate, the finished manhole will cure inside the mold until it becomes solid to remove the mold. This mold is suitable for Low-Rate Initial Production.

manhole making machine

Automatic Concrete Manhole Machine

Concrete manhole machine uses dry concrete as aggregate, and with the high-frequency vibration force, the finished manhole product has high density and strength, the mold could be removed instantly after production. This machine is suitable for mass production.

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Things You Should Know About Vibration Concrete Pipe Machine

One of my client Antonio from the Philippines came to inspect our pipe machine yesterday, the process he producing concrete pipes currently is using the manual mold, the reason he wanted to update his concrete pipe plant is to improve the efficiency.

On our way drive back to the factory from the airport, he said that Pony, I have learned so much about all the machines on the web, but there are so many types, how can you help me to work out the best solution?

There are types of machines outside there on the market indeed, but our purpose is to improve the daily output at the meantime, get qualified pipes with high density and strength of the civil project and selling.

In order to help him to wok out the solution for her requirement, I made some points that help him to make his option.

The first machine he requested is the horizontal concrete pipe machine

spinning concrete pipe machine

The horizontal concrete pipe machine has a long history, and widely used for its simple structure and operation. With the half-dry concrete as material spinning inside the mold to form the shape.

cocnrete pipe mold

The quality of pipe made by this machine mainly based on the skill and experience of the operator, the density and strength is lower than other pipes made by other machines. The main flow of pipes during the making process is that the steel cage may go deformed during rotating of mold; and the thickness may be thicker than designed, that because the pipe forms under the spinning force and the pressure between roller and mold, if we filling moderate concrete, the pipe is not completely compacted by roller and cause the unexpected quality, if we filling more concrete, the pipe could be compacted completely, but the thickness may more than we designed.

concrete pipe mold

Invest for this machine seems lower than other equipment, but we need multiple molds for each size to meet the daily output, as the mold cannot be removed until the concrete become solid.  As experiences, machine with multiple molds, the investment may equal to the vibration pipe machines.

The other issue you may take into consideration is that if the mold and the machine are not made inaccurate dimension, the machine and mold bounce a lot during the production, that could be a potential bomb to the safety of operators.

 

After the brief introduction of the roller suspension concrete pipe machine, Antonio said that, pony, I’m outdated using the manual mold, I don’t want to invest in another traditional facility once again. Please give more introduction of the vibration machine.

The next one I introduced to Antonio is the double shifts vertical vibration concrete pipe machine.

Vertical concrete pipe machine
double shift concrete pipe machine

Using the core mandrel vibrator to generate high-frequency vibration force to form the pipe into shape. The 6000rpm vibration frequency and powerful force is strong enough to liquefy the concrete during production, and make the particles of concrete full fil space between aggregate to acquire the high density and strength, which are very important for the durable of concrete pipes. With the central control panel and electric chart for delivering pipes, only two operators could run the whole production plant.

Antonio asked me why the 6000 rpm so important? Other companies vibration frequency could up to 3000-4000, are there any differences?

This is a technical issue some of the pipe machine user may ignore when they inspect the machine. The appearance of the machine and mold is quite obvious to see and check, but the frequency, its hard to tell until you actually operate the machine.

Why exactly high frequency like 6000rpm important? The diameter of aggregate we use during the production is 5-25mm, and most of them are 15mm particles, some sand particles are even within 5mm. take the range of the diameter of aggregate and the energy decrement of vibration force into consideration, 6000rpm is the best to liquefy the concrete and get the high density and strength concrete pipes. If the vibration frequency is less than 6000rpm, it's not strong enough to liquefy the concrete, and the small particles can not full fill all the spaces of the concrete, that’s the reason why there are so many air pockets on the surface of the pipes and the water permeability is too high.

I also showed this chart to Antonio to help him compare all these concrete pipe machines.

MachinesQuality of pipeAppearance of pipeEfficiencyEco-friendlyCement consumptionEnergy consumption
Centrifugal pipe machineGoodGoodLowLowHighhigh
Horizontal pipe machineMediumMediumMediumMediumLowhigh
Manual moldGoodGoodLowMediumMediumlow
Vertical vibration machinegoodmediumhighHighlowmedium
Radial press machineMediummeidumVery highhighlowmedium

After these detailed introductions, Antonio know which machine to choose as well as we all know.

Let me know in the comment if you have any questions.

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Can your vibration machine liquefy the concrete?

Liquefaction is an appearance during the compaction of dry concrete when making concrete pipes with vibration. Liquefaction is a process that airs are expelled out of the concrete, and the aggregate of concrete is compacted together firmly.

Why is liquefaction so important for making dry-precast concrete products by vibration machine? During the liquefaction, the extra air is expelled out of the concrete, and each element of the concrete are compacted and bonded with each other in high level. The mortar produced during the process could full-fill tiny gap and space, that enables to increase the strength and the density, as well as the low-permeability.

What is liquefaction looks like? Have you ever boil waters? The air bubbles keep coming out of the surface the of water. Liquefaction of concrete looks like that. But the difference is, liquefaction is a temporary scene when most of the air is expelled out of the concrete, the air bubbles are less and less visible.

You may wonder that liquefaction is very common in wet precast, but dry concrete? Not sure.

However, liquefaction happens in dry concrete too. The vibration is matters a lot for the appearance of liquefaction. Try to adjust the vibration to high frequency (5000-6000rpm) and low amplitude (close to the self-amplitude of concrete), you will get a perfect finish concrete product.

You may not tell the differences of machines whether they can make the concrete liquefy or not. But the finished concrete product won’t lie.

The concrete product that has been fully compacted and liquefied by high-frequency vibration has a smooth surface and visible density, while the one hasn’t been produced in this way came out with a surface full of pores.

concrete product hasn't been completely compacted.

concrete pipe with pore

concrete product has been fully compacted and liquefied

smooth surface

How exactly the liquefaction looks like? Alright, I took this video, not professional, but I think it’s enough to tell.