The new radar-based measurement technology enables processors to squeeze higher-quality pipes with less material. Using an automated closed-loop control system, you will get more output and less waste, thereby significantly reducing costs. #pvc #monitoring

The iNOEX WARP measurement system on Jet Stream's C900 PVC pipe extrusion line.

Squeezing municipal pipes is often more like art than science. In fact, this is a good argument. Without reliable measuring instruments and process control, processors are forced to use rougher quality control methods. These methods are troublesome and usually lead to more than continuous production that meets all relevant industry standards. Higher material consumption rate is required.

iNOEX's new radar-based online measurement system finally brings data-based real-time process control to the pipe extrusion process. With the ability to accurately measure pipe wall thickness, diameter, and roundness, these systems enable processors to reduce the amount of material required to meet the most demanding quality standards and reduce waste, while virtually eliminating the production of substandard products. In addition, by integrating the measurement system with the iNOEX gravity feeder, you can close the loop in an automated system that automatically adjusts for process drift to keep the production line running continuously day after day. You can even increase throughput by feeding at the same speed while increasing the traction speed. This is how it works.

iNOEX's WARP radar sensor measurement system uses radar technology to accurately record all relevant dimensions of the pipeline based on echo detection. Transmitting and receiving radar waves do not need to contact the coupling medium, which makes the device very robust, reliable and immune to process fluctuations.

The working principle of radar measurement is to emit electromagnetic waves to an object and capture the elapsed time between the echoes when the electromagnetic waves meet the outer or inner surface.

In operation, the radar sensor calculates very precise physical measurements based on the time-of-flight principle. The sensor unit emits electromagnetic waves and echoes when it hits an object on the path. In pipe squeezing, the first echo appears when the pulse hits the outer diameter of the pipe, the second echo appears when it hits the ID wall (or more accurately, the air behind it), and then at the end of the pipe. Repeat on the other side. By measuring the elapsed time between transmission and echo, it is possible to calculate very quickly and accurately measurements of dimensions as small as 0.200 inches (5 mm) in wall thicknesses. Even at line speeds up to 50 feet per minute (15 m/min), measurements can be generated with accuracy of ±0.002" (0.05 mm) and repeatability of ±0.004" (0.102 mm).

The WARP 8 series uses 8 sensors and measures pipe sizes from 60 to 1200 mm (2.26-47.24 inches) in diameter. More sensors can be provided according to special requirements. The WARP 100 series brings sensors closer together to provide 100% measurement around the pipe to meet the highest quality standards for pipes with diameters from 90 to 630 mm (3.54-24.80 inches).

The WARP measurement unit includes an array of these sensors, which are located around the circumference of the pipe and can be placed in multiple locations on the extrusion line. The WARP 8 system can measure the wall thickness and diameter of 8 points around the pipeline in real time, and can use more sensors according to special requirements. For applications with the most stringent quality inspection requirements, the WARP 100 device uses more sensors to achieve 100% measurement of the pipe circumference and extrusion direction, and can also detect eccentricity and ovality. 

With these measurement data, pipe manufacturers will eventually have a powerful and user-friendly tool that allows them to see the real changes in the extrusion process for the first time. Once a repeatable process distribution is established, the material feed or traction speed can be adjusted to use the least amount of material to produce 100% pipes that meet quality standards. This allows processors to more safely approach the lower limit of the required wall thickness, thereby saving a lot of material on the mass extrusion line.

WARP technology reveals the true variability of the pipe extrusion process. This is a continuous measurement of wall thickness, the distribution is shown in the green and brown graphs, and the average value is shown in blue. Once the variability distribution is known, the process can be adjusted to bring it closer to the lower tolerance limit (red line) to save material. It also shows instances where the wall thickness is lower than the specification (red circle) or higher than the specification, so it can be adjusted to continuously extrude products that meet the requirements.

According to iNOEX, it is common to save an average of 2% or more. The investment in measurement technology is only calculated based on the historical raw material cost, and the return on investment is about one year, and given the current market pricing of raw materials, the return is even faster. But this is not the only saving. The measurement data enables processors to get their production lines to produce products that meet specifications more quickly at the start of the run, and it detects process drift early in order to find and correct problems before producing any defective products. Both of these factors will result in a substantial reduction in waste.

In addition, because fewer materials are required to produce a consistent product, you can continue to push materials into the system at the same or similar speeds and increase the pulling speed. This increases the throughput of the extrusion line usually in the range of 2%. Making more pipes with fewer materials is an excellent formula for a more profitable production line.

The next level of the technology is to integrate the measurement system with the iNOEX gravity feeder to achieve automated closed-loop process control. The system will now be able to self-monitor the operating mode compared to the established set point, and automatically adjust the feed rate or traction speed when the process begins to drift, maintaining quality and stability without manual intervention. More on this below.  

Jet Stream is one of the world's leading manufacturers of construction-grade piping systems. One of Jet Stream's specialty products produced at its Siloam Springs, Arkansas plant is C900 PVC pipe for high-pressure water distribution. The pipe extruder knows that this is one of the most demanding applications for large diameter pipes (Jet Stream's C900 diameter range is 4-24 inches), and the production of substandard pipes is absolutely unacceptable.

This video explains why Jet Stream decided to switch to radar measurements in a closed-loop control system and the results they have achieved so far.

Before having a WARP radar system (see video), Jet Stream did not have a good method to measure key pipeline attributes in the production process. Instead, they rely on inspection after sawing the pipe to its final length. Their C900 production line is very long, with two cooling tanks, a traction device and a sawing station behind the vacuum tank. Therefore, if a problem is found during the inspection, a lot of materials are already being processed.

The WARP system displays the operating conditions of the production line to operators, enabling them to correct excessive material usage or emerging process drift.

Once Jet Stream has installed the WARP device behind the vacuum tank, they can now see what is happening in the process in real time. According to Assistant Plant Manager Paul England, they can immediately see impending problems and make adjustments before non-conforming products are produced. In addition, England stated that they can see their process distribution and tolerance-related situations and make adjustments so that they "will not give up all these free materials." Jet Stream also discovered that measurement data allows them to enable startups to produce high-quality pipelines faster. Louie Bold, the plant manager, said that the initial forecast of the system's return on investment was very accurate. He said it is "recovering costs" by saving materials and reducing waste.  

The WARP dashboard provides easy-to-understand pictures of all the measurement characteristics of the pipe extrusion process and shows when and where the non-conforming event occurred.

The main disadvantages of online measurement systems in the past were that they were difficult to use, maintain, and remain stable for a long time. For example, an ultrasonic system requires a water coupling medium to work, and a contact seal on the pipe to retain water. These are worn parts, and changing the pipe diameter also requires replacement of seals. X-ray systems are non-contact, but the level of radiation they emit makes some users feel uncomfortable and is impractical for larger diameter products.

WARP systems are non-contact, and the electromagnetic waves they emit have less impact on humans than mobile phones. In the entire product line, they can be used for pipes with diameters from 60 mm (2.36”) to 1200 (47.24”) mm. A single measuring system can accommodate 4 to 7 times the smallest pipe diameter (depending on the model). To start a new run, the operator only needs to call up a pre-programmed product recipe with the appropriate piping specifications, and then click Start. Since the donut-shaped measuring sensor is automatically centered and automatically centered when needed, there is no need to recalibrate for each product or during a long production run.

Radar measurement technology can also be used in a handheld version called WARP Portable. For wall thicknesses of 0.200-4.33” (5 to 110 mm), the instrument includes data records with time stamps and measurement positions of the pipe circumference.

The easy-to-understand control dashboard supports the web, so it can be viewed on a mobile device in a factory or anywhere in the world. It is displayed graphically and numerically:

It will even show where the problem is. In the example image above, you can see instances where the wall thickness is below the set value (shown in red in the bar graph) and exceeds the maximum limit (shown in black). In the circular chart on the left, you can see exactly where these events occurred on the circumference of the pipe.

The system also generates reports to provide a historical view of extrusion line performance. This is very useful in process optimization projects and quality verification reports to assure customers that products meet performance requirements.  

Integrating measurement systems (such as Jet Stream) with iNOEX gravity feeders provides an unprecedented level of automation. Through this step, the measurement system can automatically calculate the most material-saving method to manage the process. It is called fine point control, in this case, the pipe is measured in the process after it comes out of the vacuum tank. First make sure that the process is stable and meets the wall thickness specification, the thinnest point will define the control step. The algorithm then calculates the new weight per meter set point to meet the minimum acceptable wall thickness specification.

Fine-point control can automatically calculate the most material-saving way to manage the process and adjust the feeding or hauling speed accordingly. View the full-size image.

The control system can automatically increase the traction speed instead of reducing the material feed speed. This obviously saves material costs, but the increased traction speed also means that you produce more meters of saleable pipe per unit time and material. This increase usually increases throughput by 2%, depending on the amount of material reduction achieved.

WARP hot die centering control can be used to directly control the melt speed at the die to reduce eccentricity.

Another automation option is to use WARP with thermal die centering control. In this case, you need a slicing die with a separate temperature zone. At startup, each zone has the same temperature. Using this sensor, you can detect thermal eccentricity by measuring wall thickness distribution. With this data, the controller can calculate the new temperature set point for each zone and directly control the melt speed at the die to compensate.

This real case study shows how effective the combination of these measurement and control loops is. The chart here illustrates the optimization of an extrusion line for manufacturing PVC pipes with a diameter of 250 mm (10 inches) and a wall thickness of 5.9 mm (023 inches). On the left side of the graph, you can see the initial distribution of the maximum and minimum wall thickness with respect to the upper and lower tolerances. In order to consistently meet the minimum tolerances, the processor has no choice but to use a large amount of material, which can sometimes cause wall thicknesses to exceed the maximum tolerance.

250mm PVC pipe process improvement process. View the full-size image.

Here are the steps taken to optimize the process.

In this case, the closed-loop system reduces material costs by an average of about 9%. iNOEX quickly pointed out that this is an extreme situation, but it still illustrates what this technology can do. In more common applications, they conservatively predict that the system will generally reduce material costs by 2% or more and increase production by a similar amount.

The economics of radar-based measurement and closed-loop control are of great significance to many pipeline manufacturers who achieve a return on investment within a year. Reducing material costs and increasing yields for higher-quality pipes is an unbeatable formula.

Please go here to learn more about iNOEX WARP's radar-based measurement system.

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