frequently asked questions about the purchase and use of bending springs
Why the bending spring becomes an indispensable tool in the hands of a plumber
In professional installation practice, where every centimeter and every degree of bending counts, working with thin-walled pipes is often the biggest challenge. When it comes to copper or plastic pipes in heating systems, the ideal solution for maintaining the pipe's geometry without flattening it is the bending spring. These seemingly simple tools, however, hide a wealth of technical details that determine whether the installation will be successful or end up with damaged material and unnecessary repairs.
I often hear from colleagues questions like: "Why did my spring get stuck?", "How do I choose the right diameter?" or "Why does the pipe twist after bending?". These problems are not random. They arise from a lack of knowledge about the spring material, incorrect selection of type (internal vs. external), or ignoring the physical laws of metal deformation. This article will help you understand the principle of operation of these tools, teach you how to avoid common mistakes, and provide practical procedures that have been tested by thousands of plumbers in real conditions in Slovak apartments and houses.
Difference between internal and external spring: Which one to use?
One of the most common questions from both beginners and experienced craftsmen is the difference between the two main types of springs. While they may look the same at first glance – like long spirals made of carbon steel – their function and method of use differ significantly. The division depends on where the spring is placed in relation to the pipe during the bending process.
Internal bending springs are inserted inside the pipe. Their main task is to prevent the inner wall of the pipe from collapsing during bending. When you apply force to bend the pipe, the inner side is compressed and there is a risk that the pipe will flatten. The spring inside balances this pressure and maintains a circular cross-section. This type is ideal for pipes with small to medium diameters, where the spring can be easily inserted and then pulled out. When using an internal spring, it is important that the spring is slightly shorter than the length needed for the bend, but long enough to cover the entire bending area.
External bending springs are placed on the outer circumference of the pipe. They work on the principle of counter-tension. When you bend the pipe, the outer side is stretched and there is a risk that the pipe wall will tear or become too deformed. The external spring holds the outer radius of the bend and prevents excessive stretching of the material. This type is often used for thick-walled pipes or where the inner space of the pipe is already occupied (for example, already installed insulation) or where an internal spring could damage the inner surface.
From practice, I know that the most common mistake is using an internal spring on very thick-walled pipes, where the spring cannot be inserted, or conversely, using an external spring on thin pipes, where it could cause local stress. For common installations of water and heating pipes with a diameter up to 28 mm, the most commonly recommended is Bending spring - 20x2; external, which is ideal for copper pipes with a wall thickness of 2 mm. Conversely, for larger diameters such as 32 mm, Bending spring - 32x3; internal is often chosen, because the internal space allows better control of the shape without the risk of damaging the outer shell.
How to correctly choose a bending spring according to the pipe diameter
Choosing the right spring is not just a matter of chance. You must take into account two key parameters: the outer diameter of the pipe (D) and the wall thickness (S). If you choose a spring that is too large in diameter, it will not have sufficient contact with the pipe walls and will lose its support. If you choose a spring that is too small, you will not be able to insert it into the pipe or you will have to force it in, which can lead to its deformation or damage to the pipe.
Rule number one is: The outer diameter of the spring must be 0.5 to 1 mm smaller than the inner diameter of the pipe. This means that if you have a pipe with an outer diameter of 22 mm and a wall thickness of 1 mm (inner diameter of 20 mm), you need a spring with a diameter of around 19-19.5 mm. Most manufacturers indicate the spring diameter as the outer diameter of the spiral itself.
Another factor is the length of the spring. The length must be sufficient to cover the entire bent part plus a few extra centimeters for handling. If you bend a pipe at a 90-degree angle with a radius of 3 times the pipe diameter, the length of the bent part will be approximately 1.5 times the diameter. Therefore, the spring length should be at least 20 cm longer than this distance, so you have enough space to insert and remove it. Example: for a DN20 pipe (diameter 20 mm), you need a spring at least 300-400 mm long. For long pipe sections where you have to bend multiple times in succession, it is necessary to use Bending spring - 26x3; internal with sufficient length to be able to slide it along the pipe without having to remove it completely.
When choosing, do not forget the type of material. Copper pipes are soft and require springs with higher strength, while plastic pipes (PEX, PERT) can be bent without a spring, but a spring is necessary for precise angles and long sections. For small diameters, such as 16 mm or 18 mm, the ideal choice is Bending spring - 16x2; external and Bending spring - 18x2; external, which are designed to easily fit onto thin walls and ensure a stable bend without the risk of breaking.
Gradual bending of pipes without damaging the walls
One of the most common questions in practice is: "Why does my pipe twist or have an irregular shape after bending?" The answer is often incorrect bending technique. The pipe should not be bent in one single motion. This is a key principle that many beginner plumbers ignore. Bending in one step leads to localized material stress, which causes cracks or flattening.
The correct method is gradual bending. Divide the total bend angle into smaller segments (for example, 10-15 degrees). After each segment, release the spring, move it a little further, and continue with the next bend. This ensures even stress distribution along the entire length of the bent section. The spring should always remain in contact with the pipe in the area currently being bent, and at the same time, it should support adjacent sections to prevent the formation of "wings".
An important aspect is also temperature. When working with copper pipes, it is advisable to slightly heat the pipe before bending (for example, with a blowtorch), which increases the metal's plasticity and reduces the risk of cracking. On the other hand, plastic pipes should not be overheated, as they may deform or lose their mechanical properties. When bending plastic pipes, it is essential to maintain the minimum bend radius specified by the pipe manufacturer (usually 5 to 6 times the pipe diameter).
This method is especially important for installations in tight spaces, where it is necessary to bend pipes at sharp angles or in complex configurations. Using a high-quality spring, such as Bending spring - 20x2; external, allows you to perform these operations with maximum precision and minimizes the risk of material damage.
Why the spring gets stuck in the pipe and how to remove it
No plumber has not encountered the situation where the spring gets stuck. It is a frustrating situation that can stop the entire work. The causes of jamming vary, but the most common are the wrong type of spring or pipe damage before bending.
Causes of jamming:
- Wrong diameter: If the spring is too large, it can catch on irregularities inside the pipe or on joints.
- Combination of internal and external spring: If you use an internal spring on a pipe that has internal obstructions or joints, the spring can get caught.
- Pipe damage: If the pipe is already damaged before bending (for example, cut with shears that leave sharp edges), the spring can get caught in these edges.
- Wrong type: Using a spring made of too hard steel for a soft pipe can cause the spring to "bite" into the material.
Solution:
If the spring gets stuck, never pull it with force, as this could completely destroy the pipe. Try gently rotating (twisting) the spring back and forth to reduce friction. If that doesn't help, try gently pushing the spring forward while simultaneously twisting it. In the case of a completely jammed spring, you can try using a second spring that you insert behind the stuck one and attempt to push it out. As a last resort, you can use a special spring extraction tool or, in the worst case, cut the pipe and start over.
To prevent this problem, it is important to thoroughly clean the pipe ends before installation and use the correct type of spring. For copper pipes with a wall thickness of 2 mm, the best choice is often Bending spring - 18x2; external, which is designed to easily fit and not dislodge during bending.
Maintenance and storage of bending tools for long life
Bending springs are an investment worth protecting. Proper maintenance not only extends their lifespan but also ensures safe work. The most important rule is cleaning and drying. After each use, thoroughly clean the spring from dirt, oil, and moisture. Moisture is the biggest enemy of springs, as it causes corrosion, which weakens the steel and can lead to spring breakage during further use.
Storage:
- Store springs in a dry and well-ventilated environment.
- Avoid storing near chemicals or salts, which accelerate corrosion.
- Do not store springs in a bent or deformed state. Ideally, store them in flat boxes or on hooks.
- Regularly check the condition of the springs. If you notice signs of corrosion, cracks, or deformations, replace them immediately.
For long-term durability, it is advisable to apply a thin layer of protective oil to the springs after each use. This not only protects against corrosion but also reduces friction during further use, making insertion and removal easier.
Common mistakes when installing bending springs
Other common mistakes include using the spring for the wrong type of pipe. For example, using a spring to bend hard pipes that should be bent in a different way can lead to unnecessary material damage. Another mistake is ignoring the minimum bend radius. Each pipe has its own minimum bend radius that must not be exceeded, otherwise permanent deformation or cracking will occur.
Another common mistake is lack of time for bending. Plumbers often try to work quickly and bend the pipes too fast, leading to uncontrolled stress. Bending should be slow and controlled. It is also important not to use the spring as a lever. The spring is meant to support the pipe, not to be used as a lever. This can lead to its breakage or pipe damage.
To conclude, it is important to emphasize that the quality of the spring is key. Cheap springs made of low-quality steel deform quickly and lose their functionality. An investment in high-quality springs, such as those from trusted manufacturers available in the category tools and installation aids, is definitely worth it. A quality spring will save you time, nerves, and money on repairing damaged pipes.
Bend radius and its impact on pipe cross-section
A key parameter determining the functionality of a spring is the minimum bend radius. If you attempt to bend a pipe under an overly sharp angle without sufficient spring support, it will result in significant flattening of the cross-section (so-called "flaring"), which reduces the internal opening and restricts water or gas flow. The spring acts as an internal core that forces the material to maintain a circular shape even under maximum stress.
In practice, this means that for each wall thickness there is a limit beyond which the spring can no longer prevent deformation if the radius is too small. Therefore, always verify the minimum bend radius for a specific type of pipe before starting the work. Using a spring with optimal stiffness allows you to achieve precise angles without compromising the pipe cross-section.
Surface treatment technology and corrosion resistance
We cannot talk about springs without mentioning their material treatment. Most high-quality springs designed for heating systems are made from high-strength carbon steel, which, however, requires protection against moisture. The most common surface treatments for springs are phosphating or oil coating. Phosphating creates a thin layer that prevents rapid rusting, while the oil layer provides an immediate hydrophobic barrier and also acts as a lubricant when inserting the spring into the pipe.
Why is this important? In installations in bathrooms, underfloor heating systems, or outdoor piping, the pipe may be exposed to increased humidity. If the spring's surface becomes damaged and starts to corrode, it could break inside the pipe or leave rust particles inside the system, which could clog valves or radiators. Therefore, when purchasing, it is important to look for springs marked as suitable for more humid environments or to ensure proper lubrication after use.
When purchasing from our online store, you can be sure that the springs we offer are made from materials that meet these standards. Regular inspection of the surface condition and subsequent application of protective oil after each use is a simple step that will extend the tool's lifespan by several years.
FAQ: Most frequently asked questions about purchasing and using bending springs
What is the difference between a bending spring for copper and plastic pipes?
Although the physical principle is similar, the difference lies in the material stiffness and wall thickness. For copper pipes, you need springs with higher strength and corrosion resistance, as copper pipes are often exposed to higher temperatures and pressures. For plastic pipes (PEX, PERT), springs with lower stiffness are sufficient, as plastic is less resistant to high temperatures and pressure. It is also important to observe the minimum bend radius, which is larger for plastic pipes.
Can I use one spring for all types of pipes?
This is not recommended. Although universal springs exist, each pipe has specific requirements for diameter and wall thickness. Using the wrong spring can lead to pipe damage or insufficient support. It is best to have a set of springs for different diameters and pipe types.
How long does a bending spring last?
The lifespan of a spring depends on the frequency of use, material type, and storage conditions. With proper maintenance and storage, a spring can last for years. However, if it is frequently used for bending hard materials or is exposed to moisture, its lifespan is reduced. It is recommended to regularly inspect it and replace it if signs of wear are visible.
Why is my spring not fitting into the pipe?
This is the most common mistake when selecting a spring. Make sure the spring diameter is 0.5 to 1 mm smaller than the internal diameter of the pipe. If the spring is too large, it will not have sufficient contact. If it is too small, it may not provide enough support. Check the pipe dimensions and choose the appropriate spring.
Can I bend the spring manually without a tool?
Not at all. The spring is designed to be inserted into the pipe and bent together with it. If you bend it manually, you risk deforming or breaking it. Bending should be done using special tools or manually, but with gradual bending and monitoring of the radius.
Is it safe to bend pipes with a spring at low temperatures?
Yes, but caution is needed. At low temperatures, metal becomes more brittle, increasing the risk of cracking. It is recommended to slightly warm the pipe before bending to increase its plasticity. For plastic pipes, it is necessary to follow the temperature range specified by the manufacturer.
Conclusion
Bending springs are an invaluable tool in the arsenal of every professional installer. The correct selection, use, and maintenance of these tools ensure high-quality and safe installation of heating systems. Do not be afraid to experiment with different types of springs and methods, but always follow professional advice and experience. With quality products like those offered in our online store, your work will become more efficient and safer.
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