Shandong qiaotai pipe technology Co., Ltd.

Double-wall wound pipe features corrosion resistance, light weight, easy installation, large flow capacity and long service life (50 years). It can replace pipes made of high-energy-consumption materials such as concrete, cast iron and ceramics, and is an eco-friendly green product.

The characteristics of double-wall wound pipe are as follows:

1. Safe and reliable ring stiffness. Compared with pure plastic pipes, the reinforced steel strip enables the pipes, especially large-diameter pipes, to achieve sufficient and reliable ring stiffness.

2. Smooth inner wall, with flow resistance 20~30% lower than concrete pipes. The inner wall of polyethylene (PE) pipes is smooth with a low friction coefficient; sediments are not easy to accumulate inside the pipe, and the friction resistance remains nearly unchanged after long-term service of HDPE hollow wall wound pipes. Flexible and leak-free connections (electro-fusion welding, butt welding), excellent sealing and environmental performance. Both sealing connection methods can be manually operated with simple tools without machinery, which is quite convenient and ensures reliable zero leakage.

3. On-site manufacturing greatly saves transportation costs. The strip material can be delivered in coils (ordinary cable reels). The pipe winding equipment is simple and compact, so manufacturers can transport the equipment close to construction sites to produce pipes on demand, greatly cutting customers’ transportation expenses.

4. Strong resistance to unexpected sudden loads. The pipe can release generated stress through elastic deformation, avoiding leakage or damage at pipe joints caused by excessive stress and deformation. Competitive overall cost. Combining the advantages of steel and plastic materials, this pipe delivers excellent comprehensive performance.

5. Corrosion resistance with a service life of over 50 years. High-density polyethylene (PE) pipes can serve up to fifty years.

6. Light weight, fewer joints, no heavy equipment required for easy installation and laying. Its light weight eliminates the need for large hoisting equipment during installation. With good axial flexibility, it has low requirements for the flatness and firmness of the trench base, and can withstand abnormal stress caused by improper installation.

The quality of any engineering project hinges on the details; therefore, drawing on the practical experience of others, we have summarized common issues to avoid in water supply and drainage pipeline construction, analyzed their causes, and proposed solutions. Rainwater pipes should not be connected using expansion joints or standard pipe couplings. Reason: Rainwater pipes typically have thin walls; during heavy downpours, a vacuum can easily form inside the line, causing the pipe to collapse or burst. 

Solution: Direct downspout connectors must be used during installation. These connectors serve two primary functions: connecting the pipeline and providing venting, overflow relief, and accommodation for thermal expansion. PE and PVC-U pipes are unsuitable for hot water applications: the standard operating temperature for PE pipe is below 40°C, and for PVC-U pipe, it is below 45°C. Case study: A D50 1.0 MPa PVC-U water supply pipe was connected to a solar water heater system. 

Failure to account for hot water backflow resulted in the pipe constantly containing hot water; consequently, the D50 pipe expanded due to heat, with its outer diameter swelling to 110 mm, causing severe deformation. Water supply pipelines should not be backfilled or concealed before undergoing pressure testing. Reason: Pressure testing verifies the pipeline's strength and airtightness, preventing leaks during operation that could lead to significant losses. 

Solution: After installation, water supply pipelines must undergo pressure testing in accordance with relevant technical specifications; backfilling or concealment should only proceed once it is confirmed that there are no leaks. Water supply pipelines with significant vertical drops require venting devices. Reason: When there is a large vertical drop or a long run, water hammer or negative pressure (vacuum) can occur within the pipeline, leading to collapse or structural damage.

Professionals in the piping industry are likely familiar with HDPE double-wall corrugated pipe. It is a new type of lightweight pipe made from high-density polyethylene, characterized by low weight, high-pressure resistance, good toughness, rapid installation, and a long service life. Due to its convenient and reliable connection methods, HDPE double-wall corrugated pipe is now widely used both domestically and internationally. 

Currently, double-wall corrugated pipes are primarily used in municipal drainage and sewage pipeline systems; underground drainage and sewage networks for apartment complexes and residential areas; embedded conduits for highways; underground seepage drainage networks for golf courses; agricultural water conservancy projects such as irrigation and flood drainage; fluid transport and ventilation in chemical plants and mines; and protective casings for underground pipelines and communication cables. 

During transport, loading, and unloading, double-wall corrugated pipes must not be thrown, dropped, subjected to heavy pressure, exposed to prolonged sunlight, or placed near heat sources; they must not be transported alongside toxic or hazardous substances; and coiled multi-hole pipes must not be transported lying flat. Double-wall corrugated pipes should be stored in a dry warehouse at ambient temperature. Straight pipes should be laid flat, with a stacking height not exceeding 2 meters. Fittings and coiled multi-hole pipes may be laid flat but should be protected from heavy pressure or crushing loads. HDPE double-wall corrugated pipes must not be stored together with toxic or hazardous substances. 

They should be kept away from heat sources, and prominent "No Fire" signs should be displayed in the storage area. The storage period generally should not exceed two years from the date of manufacture. Regarding the performance characteristics of double-wall corrugated pipes: they feature a unique structure, high strength, and resistance to compression and impact. The inner wall is smooth, resulting in low friction and high flow capacity. Connections are convenient, and joints are well-sealed and leak-proof. Their light weight facilitates construction and reduces costs. They offer an underground service life of over fifty years. Polyethylene is a hydrocarbon polymer with non-polar molecules, providing resistance to acid and alkali corrosion.

After the corrugated pipe is formed, it is necessary to inspect it for holes to prevent defective products from entering the market and to ensure manufacturing quality. Current inspection methods involve placing a light source inside the pipe and moving it along the interior, while a photosensitive element positioned on the outside tracks the light source's movement to detect light. If a hole exists in the pipe, light emitted from the source passes through the hole to the exterior; the photosensitive element detects this light and issues a signal indicating that the pipe is defective and must be discarded. However, due to the pipe's corrugated structure, adjacent corrugations can obstruct one another; if a hole is blocked by an adjacent corrugation, light cannot escape, leading to potential inspection errors and poor detection performance. 

This article aims to provide a hole detection device for plastic corrugated pipes to improve inspection accuracy. To achieve the aforementioned objective, the basic technical scheme of the product is as follows: a hole detection device for plastic corrugated pipes, comprising a detection platform. The detection platform includes a base plate provided with a frame and a through-hole extending vertically through the base plate. A metal bell housing is disposed beneath the base plate; this housing has an upper opening connected to the lower end of the through-hole and a lower opening at its bottom. A vibrating shaft is movably connected within the metal bell housing; one end of the vibrating shaft extends upward through the upper opening and the through-hole to a position above the base plate. A pull cord is attached to the section of the vibrating shaft located inside the metal bell housing, and a suspended ball is attached to the pull cord, positioned within the housing. The frame is equipped with a fixation mechanism comprising a central shaft tube rotatably connected to the frame. One end of the central shaft tube is connected to a bellows, and a pulley is fixedly mounted on the tube and connected to a first motor. The other end of the central shaft tube is fixedly connected to a threaded tube, upon which a central sliding block is threadedly mounted; a vertical rod is slidably connected to this central sliding block. An outer conduit is sleeved over the central shaft tube and rotatably connected to the frame; this outer conduit is connected to a second motor and has an upper inclined rod fixedly attached to it. An upper sliding block is slidably mounted on the upper inclined rod and is also slidably connected to the vertical rod.

The operating principle of this scheme is as follows: the fixation mechanism secures the corrugated pipe in place. When the first motor operates, it drives the rotation of the threaded tube via the pulley and the central shaft tube. When the second motor operates, it drives the rotation of the outer conduit, which in turn rotates the attached upper inclined rod, causing the upper sliding block on the rod to move accordingly. Since the vertical rod connects the upper sliding block and the central sliding block, the movement of the upper sliding block drives the central sliding block to rotate along the threaded tube. When there is a difference in rotational speed between the first motor and the second motor, a speed differential arises between the central sliding block (driven by the second motor) and the threaded tube (driven by the first motor), causing the threaded tube to push the central sliding block to slide along its length. As the central slider moves, it drives the upper slider to move in unison via the vertical rod; this shifts the upper slider to the end of the upper inclined rod—farthest from the central shaft tube—where it clamps the corrugated tube firmly in place, thereby automatically securing it. At this stage, air from the bellows is forced through the central shaft tube and into the threaded tube, from which it flows into the corrugated tube. The airflow travels from one end of the corrugated tube to the other; if a hole is present, air escapes through it onto the base plate of the testing platform, causing the vibration shaft to vibrate. As the vibration shaft oscillates, it swings a suspended ball against a metal bell housing, producing a sound that alerts the operator that the corrugated tube is defective (i.e., contains a hole). Conversely, if there are no holes, the air exits through the far end of the corrugated tube without triggering the bell, thus completing the inspection process. 

Once the upper slider has clamped the corrugated tube, it continues to rotate under the guidance of the upper inclined rod. This rotation turns the clamped corrugated tube, allowing different sections to be positioned near the vibration shaft for comprehensive testing, thereby ensuring inspection accuracy. 

The beneficial effects of this method are as follows: 1. This product utilizes airflow to detect holes in the corrugated tube. Compared to existing optical detection methods, airflow offers two advantages: first, because airflow lacks a fixed direction, it fills the entire interior of the corrugated tube, enabling a comprehensive inspection; second, the flowing air exerts force on surrounding objects, meaning that if a hole is obscured by an adjacent fold, the air can push the obstruction aside to escape through the hole, thereby enhancing detection precision. 2. The presence of a hole is determined by observing whether the airflow causes the vibration shaft to vibrate; the resulting vibration causes the shaft to strike the metal bell housing, producing an audible alert that notifies the operator, facilitating timely handling of the issue. 3. Rotating the threaded tube causes the central slider to drive the upper slider to slide, thereby clamping the corrugated tube securely in place; this rotation allows for comprehensive inspection of multiple sections of the corrugated tube, enhancing inspection accuracy. 

A lower inclined rod is fixed to the outer pipe, and a lower slider is slidably connected to this lower inclined rod; the lower slider is also slidably connected to a vertical rod. The lower inclined rod works in conjunction with the upper inclined rod to simultaneously clamp the corrugated tube, ensuring stable rotation and facilitating the inspection process. 

A water tank is positioned beneath the base plate, with the end of the vibration shaft distal to the base plate extending into the tank. A water pipe connects to the upper part of the tank and communicates with the central shaft tube; a water pump is installed on this water pipe. When the vibration shaft vibrates, it agitates the water in the tank, causing the water level to rise and fall continuously. During these fluctuations, some water flows into the water pipe and is pumped into the central shaft tube, subsequently flowing into the corrugated tube via the threaded tube. By observing the water surface fluctuations or checking for the presence of water inside the corrugated tube after the procedure, the operator can determine whether the tube has any holes; this provides a reliable basis for assessment and ensures accurate inspection. 

There are two sets of fixing mechanisms positioned opposite each other, with one set slidably connected to the base plate. These two sets simultaneously clamp and secure both ends of the corrugated tube. This arrangement prevents issues such as ineffective securing when the tube is heavy, or swaying of the unsecured end when the tube is light, thereby ensuring stable inspection conditions. 

Multiple perforations are arranged in a straight line between the two sets of fixing mechanisms. These perforations allow for the simultaneous inspection of multiple points on the corrugated tube, thereby increasing inspection precision. 

A conical opening is connected to the upper end of each perforation, specifically at the perforation's narrower end. Compared to a standard circular opening, the conical shape concentrates the airflow exiting the corrugated tube and directs it onto the vibration shaft, inducing significant vibration that facilitates easier inspection and observation. Stopper blocks are provided at both ends of the vertical rod and at the end of the threaded tube furthest from the central axial tube. These stopper blocks prevent the central sliding block, the upper sliding block, or the lower sliding block from detaching from the threaded tube or the vertical rod.

Unexpected quality issues often arise during PE pipe production, typically caused by equipment malfunctions or raw material defects. Qingdao Shunyide Plastic Industry Co., Ltd. has compiled a list of common PE pipe quality issues, their causes, and corresponding solutions for your reference.

I. Ripples on the pipe surface

Causes: 1. Insufficient cooling; 2. Improper sealing ring size, causing vibration.

Solutions: Increase water flow to the sizing sleeve or increase the distance between the die and the sizing sleeve. Check if the vacuum tank sealing ring is undersized; if so, replace it, or appropriately lower the vacuum level in the first vacuum tank while increasing it in the second.

II. Surface pitting (mainly on the inner wall)

Causes: 1. Impurities in the raw material; 2. Inadequate cleaning of the inner surfaces between the die and the mandrel; 3. Localized overheating leading to material degradation.

Solutions: 1. Inspect raw materials; 2. Clean thoroughly or allow a transition period; 3. Check temperature sensors.

III. Surface depressions/craters

Causes: 1. Moisture in raw material causing bursting air bubbles; 2. Uneven water flow in the sizing sleeve.

Solutions: 1. Dry the raw material; 2. Adjust water flow or replace the sizing sleeve.

IV. Surface bright spots

Cause: Insufficient water flow in the sizing sleeve.

Solution: Increase water flow or replace with a sizing sleeve that allows for higher water flow.

V. Axial roughness on inner and outer walls

Cause: Excessive moisture content in the raw material.

Solution: Dry the raw material.

VI. Lack of surface gloss

Causes: Improper melt temperature or issues with the raw material.

Solutions: Adjust melt temperature or replace the raw material.

VII. Scratches on the outer surface

Cause: Sand or grit adhering to the sizing sleeve, support plate, or sealing ring.

Solution: Clean the sizing sleeve, support plate, or sealing ring.

VIII. Water lines on the outer surface

Cause: Localized blockage of water holes in the sizing sleeve, causing excessive water flow from specific holes.

Solution: Clean the sizing sleeve.

IX. Grooves on the inner wall (common in thick-walled pipes)

Cause: Excessive wall thickness makes it difficult for the melt to cool, leading to material flow.

Solution: Try using an internal cooling system and lower the temperatures of the die and mandrel. X. Uneven pipe wall thickness

Causes: 1. Loose bolts on the die or mandrel, or improper adjustment of the die gap; 2. Uneven temperature of the die or mandrel, leading to inconsistent material flow; 3. Misalignment between the sizing sleeve and the die, or blockage of the spiral mandrel or screen pack.

Solutions: 1. Tighten bolts or adjust the die gap; 2. Check heating bands and temperature sensors; 3. Adjust the alignment of the sizing sleeve and die, or clear the spiral mandrel or screen pack.

XI. Low elongation at break

Causes: 1. Poor raw material plasticization; 2. Increased orientation.

Solutions: 1. Adjust process temperatures to improve plasticization; 2. Increase the distance between the die and the sizing sleeve.

XII. High ovality

Cause: Gravity

Solution: Install a calibration/correction device.

Only by establishing strict operating and process procedures—and strengthening process control—can PE pipe manufacturers achieve the dual goals of ensuring pipe quality and reasonably reducing production costs.