Making Concrete Pipe

There are a lot of ways to make a concrete pipe. In 1905 My great, great, great uncle John L. Ziedler came up with a pretty ingenious way to make pipe. it was a machine called a Packerhead, Europeans sometimes call this a radial-press. This method, which was developed almost simultaneously by McCracken (now Besser) was a significant step forward  in the production of concrete pipe in North America. This ability to mass produce quality concrete pipe help tremendously in the process of separating storm and sewer lines to create a cleaner healthier environment. it also gave access to the tools which would allow us to create the highway systems.

Today, however, a lot of pipe is made (in North America) with vibration, which is also a great method. I spent much of the beginning of my time with concrete equipment working with vibratory pipe production equipment. However, there are other methods for pipe production as well such as spinning and wetcast. What follows is a brief synopsis of these methods and my musings on the strengths and weakness' that I believe they offer.


Vibration:
The other methods are all very good, but if I were to choose one machine to run a pipe operation it would be a vibration machine. Most production methods incorporate vibration (with the exception of spinning) There are many vibration methods to choose from. The magic of vibration is that you can cast which ever shape of pipe the market demands. Round, Arched, elliptical, and even Box shapes can be accomplished with vibration. Below are descriptions of various vibration methods


Rising Core:
Only three machines I know of fit this description. The Pedershaab (now HawkeyePedershaab) Mastermatic series of machines and Hydrotile's (now Besser) Neptune which have now, all but vanished. There is one other which was called the Hydropac (also by Hydrotile). Only the Mastermatic is common today. The Mastermatic is a high output machine, that when pushed to its limit can produce in the area of 1000 8' joints per day, of pipe up to 24". Like the Packerhead machine it is generally limited to round pipe, unless it is equipped with header rings.

The Mastermatic has a vibrator mounted in the core of the mold, down about 2-3' from the top. this vibrator is mounted so that it distributes energy equally on all sides. at the top of the core the is a distributor (roller compactor) that pushes the low slump concrete that is being fed into the outer mold, and on top of the core, out to the edges and down. this material is then vibrated to get all of the entrapped air to rise up from the concrete as it is being compressed between the vibrating core and
the jacket of the mold.

This is a great machine for the fast production of reinforced concrete pipe as the concrete drops to the height of the core before being forced to the wall. This system is fast and makes excellent pipe, but it is a high maintenance system. It takes dedication and good operators to consistently run well.


Stationary Core:
In this method the core and the jacket of mold that forms the concrete pipe stand at roughly the same height and the concrete. This means that the concrete, usually a very low slump must fall a distance of 8' to go from the top of the mold to the bottom. With reinforcement this can be a slow process when compared to the Mastermatic or the Packerhead. it can also lead to excess air joining the concrete that will have to vibrated out to get a dense product. Despite these limitations these systems represent, what I consider to be, the best overall pipe production method.

When run with electric vibration mold can be quickly changed on a machine, so that a company can produce multiple shapes and sizes of pipe in a single shift. A few are even equipped with turn tables, which hold three molds, so that the filling process can happen at a natural rate while other processes such as vibration and demolding happen separately. Additionally with Electric vibration molds can be run with multiple cavities for making more than one pipe at a time.

This is an excellent method and if a company can have but one pipe machine to produce a full range for the North American market this is the one I would pick.


Jacket Vibration:
I am not a big fan of jacket vibration as it is very difficult to get and even vibration and will often leave spots that compact prematurely and create barriers that unwanted air cannot escape through. There may be advancements in jacket vibration, however,  that I am not aware of, and I have head lot of positive talk about Egg laying box culvert systems which use this vibration method. I think that jacket vibration is the necessary evil of having a system that can cast a large product and leave the product behind, rather than it being a superior vibration method. Feel welcome to rebute me on this as I am not an expert on jacket vibration, and I would like to give correct information.


Table Vibration:
Vibration tables are a reasonable method for producing large diameter pipe in all shapes. I have seen vibration tables making high quality pipe down to 24" in gang-forms (a form with cavities for more than one pipe. The important thing to remember with table vibration is that the vibration need to use the compacted concrete as a conduit to transmit it energy, so a small diameter pipe like a 12" provide a very narrow path, especially at heights of 8'.

Larger pipe 24"+ whether round, elliptical, or arched and box culvert are wonderful products for a vibration table. for a smaller producer or market where versatility is key, a vibration table and a packer combined could be a magic combination.

Vibration tables need to be made the right way for producing a concrete pipe. A vibrator can not just be strapped to a table with rubber dampeners. Making pipe on a table requires the ability to adjust both amplitude and frequency during the process of filling the pipe. The reason for this, as I see it, is that some of the energy of the vibration will be absorbed by the already compacted concrete, and this absorption or dampening effect will increase as the concrete height increase. However, if the lower levels of concrete are tightly compacted (with proper frequency and amplitude of vibration) this dampening effect maybe virtually erased.


Packerhead / Radial Press:
This system is near and dear to my heart, due to the family connection. The packerhead method of compacting concrete is about force. Not entirely about force, but mainly. The body of a packerhead pipe is made by compressing relatively low slump concrete between a steel outer form (jacket) and an interior roller head. This rollerhead is made to rotate by a shaft/shafts which connect the rollerhead to a driving motor. The roller heads distribute and compact the concrete as it is being fed into the mold working up from the pallet to the very top of the pipe. Below the rollerheads are a row of trowels whish smooth the compacted concrete

It used to be that the rollerhead could go only a single direction as there was only a single shaft running a single level of rollers. Today packerheads usually used stacked rollers that rotate in opposite directions as they are being run by two separate shafts.

Below the rollerhead is a vibration unit called the bellpacker. the pallet (usually a ring for forming the female connection) sit on the bellpacker, which vibrates, and helps compact the concrete. this has traditionally been a weak point for packerhead pipe as it is hard to get a tight compaction of concrete when the pallet jumps on the bell packer. I remember working on methods to secure the pallet to the bell packer to assure a tight compaction of the bell. This should be considered when looking at a packerhead.

Packerheads have the ability to make the highest quality concrete pipe with extremely low absorption rates, but they must be well run to accomplish this. They also can produce large quantities of a given pipe size as fast as any machine, but the are limited to round products and only a single size at a time.

There have been some notable improvements made to packerhead machines over the last 10-15 years. I would suggest that anyone who has a need to produce round pipe in high quanities look into packerhead production. Remember, however, that packerhead are good for round pipe only, and it would likely benefit any modern producer to be able to produce other shapes. My belief is that a packer head is a great machine to have in conjunction with another machine that offer the needed versatility.


Spun Pipe:
This method of producing concrete pipe is rarely used in the US for the production of RCP (reinforced concrete pipe). It is however used for pressure pipe manufacturing, especially by companies that are producing joints of 25'-50', where the concrete is being cast into a steel cylinder. Watching the spun pipe method is really amazing, as you see concrete defy gravity. This is because of the centrifugal force created by the rapidly spinning steel cylinder that the concrete is being fed into. the speed is so great that the concrete adheres to the wall of the cylinder and spreads evenly. furthermore, as the concrete materials shuffle to find the lowest possible point of order along the inner wall of the steel cylinder, the air and excess water is pushed out and away for the steel surface and what is left behind in a smooth dense interior finish.

I have heard that the pipe molds can on rare occasion come loose of the spinning systems. this sounds pretty terrifying to me.


Wetcast Pipe:
Producing concrete pipe with wet-cast was seen as old technology for a long time. Now, however, with improved automation and concrete production methods, wet-cast pipe production is again gaining popularity. SCC (self compacting concrete) is a big driver of this increased use of wet-cast. In other forms of pipe production it is hard to completely eliminate bug-holes (small voids) especially if you have a bell on the product. Air pockets under vibration can move fairly well (relatively) up a vertical surface of a mold, but often bog down when traveling a slope. SCC moves air far better than previous concrete, and when given even slight vibration the air quickly moves to the surface, leaving behind a very dense product with low absorption.

Companies have developed many new and improved ways to make and delivered high slump concrete to the molds. and quality benefits can outweigh the need to leave products in a mold to cure. There are a few North American pipe producers using wet-cast, but as the success of this method is more broadly realized, I expect that we will see it becoming a standard production method with large diameter pipe.

Final Note:
I do not work for or with any pipe machinery manufacturers. I worked with concrete pipe machinery for several years and enjoyed it immensely. I worked with Pedershaab, HawkeyePedershaab, and Teksam equipment, all of which made good quality pipe manufacturing equipment. I believe that most machinery producers selling in North America today are offering high quality equipment. My goal is to offer insight from a relatively neutral view in order to help current and future pipe producers know what methods are commonly available.

One More Thing:
If you need a mixing and batching solution to help with you pipe production... I do sell those, Mixer Systems. Please feel welcome to contact me to learn more about the process of making concrete.  262-893-8554  I look forward to hearing from you.