Heatecx Limited
Cold Pins (also known in the industry as Terminal Pin or cold pins) are critical electromechanical components specifically designed for the manufacture of tubular electrical heats. Their main function is to act as an electrical conducting bridge between the external power source and the nichrome spiral (resistive wire) located in the core of the metal tube. Unlike the internal heat, the design and materials of the Cold Pins ensure that they conduct electrical current efficiently without generating heat (“cold zone”). This is fundamental to prevent overheating at the connection ends of the heat, ensuring the integrity of the seals, user safety, and the durability of the heating element in industrial and commercial applications.
In the heating element assembly process, precision is vital. Terminal sets generally consist of two complementary pieces that facilitate automated manufacturing, especially when using an MgO (Magnesium Oxide) filling machine. In the upper part of the assembly, a Hook Pin (Pin with Hook) is used, whose bend or hook at the end allows for perfectly hanging and centering the nichrome spiral inside the metal tube. This centering is crucial to prevent the heat from touching the tube walls and causing a short circuit during the pouring of the insulating powder. On the other hand, at the base of the tube, a Plug Pin / Bottom Pin (bottom pin or plug) is used, which lacks a hook to allow for a cleaner and more uniform powder flow, sealing and positioning the spiral at the bottom before filling. Together, these terminals ensure controlled thermal distribution and a robust internal structure, capable of withstanding subsequent rigorous compaction processes.
Extreme Mechanical Resistance: Designed to withstand the rolling or reduction process. After filling with the MgO filling machine, the tubular heat passes through compression rollers to compact the insulating powder. The Cold Pins possess the necessary hardness not to deform, bend, or break under this extreme compression, maintaining the structural integrity of the element.
Controlled Electrical Conductivity: Manufactured with specific alloys that present significantly lower electrical resistance than the heating spiral. This guarantees that heat generation is concentrated exclusively in the center of the tube (active zone) and not at the ends (cold zone), protecting external electrical connections from damage due to thermal stress.
Filling Process Optimization: The differentiated design of the Hook Pin (Pin with Hook) and the Plug Pin / Bottom Pin is ergonomically conceived for modern production lines. They facilitate automatic centering of the heat and homogeneous pouring of the magnesium oxide, reducing cycle times on the MgO filling machine and minimizing the rejection rate due to internal short circuits.
Contaminant-Free Surface: The pins undergo strict cleaning processes to guarantee a surface free of oils, greases, or machining residues. This surface purity is indispensable for the magnesium oxide to adhere and compact correctly around it, avoiding contamination of the dielectric insulation which could lead to current leakage.
Corrosion Prevention: Depending on the base material, the terminals have surface treatments (such as nickel plating) that prevent oxidation both during storage and throughout the service life of the final product, even in high-humidity environments or corrosive atmospheres.
The specifications of the Cold Pins / Terminal Pins vary according to the load requirements and dimensions of the heating element, but standard industry parameters include:
|
Parameter |
Standard Specification |
|---|---|
|
Base Material |
High-quality carbon steel or Stainless Steel (AISI 304, 316, 321) for humid or corrosive environments. |
|
Surface Treatment |
Electrolytic nickel plating (3 to 5 microns) on carbon steel pins to prevent corrosion. |
|
Pin Diameter |
From 1.5 mm up to 6.0 mm (Typical tolerance of ±0.02 mm). |
|
Total Length |
Variable, typically from 30 mm up to more than 300 mm. |
|
"Cold Zone" Length |
Customizable. Determines the distance of heat penetration towards the tube ends. |
|
Dielectric Compatibility |
Degreased surface, optimal for adhesion of high-purity MgO. |
|
Tensile Strength |
> 400 MPa, withstands elongation during the reduction/rolling process. |
To adapt to the diverse machinery configurations and heat designs, we offer the following main models:
Upper Model - Hook Pin (Pin with Hook):
Description: Terminal equipped with a bend or notch on its inner end.
Application: Hooks onto the nichrome spiral. Essential for maintaining tension and perfect centering while the MgO filling machine pours the insulating powder from the top.
Lower Model - Plug Pin / Bottom Pin (Blind or Base Pin):
Description: Terminal with a straight design on its inner end, without a hook.
Application: Acts as a lower anchor. Its smooth design allows the MgO powder to flow cleanly to the bottom of the tube, ensuring dense compaction at the base without creating air voids.
Threaded Pin Model (Threaded Terminal Pin):
Description: Incorporates a machined thread on the outer end (connection zone).
Application: Facilitates direct connection of electrical cables using nuts and washers, ideal for industrial furnace heats or water heaters.
Smooth Pin / For Soldering Model (Plain Terminal Pin):
Description: Smooth outer end.
Application: Designed for connections using faston-type terminals (crimping) or spot welding.
We understand that each heating element manufacturer has unique needs. Therefore, our Cold Pins can be completely customized to optimize your production line:
Custom Dimensions: Manufacturing of specific total lengths and cold zone lengths according to customer drawings, allowing exact thermal control for special applications (e.g., plastic injection molds, hot runner nozzles).
Hook Design (Hook Design): Customization of the angle, depth, and style of the hook on the Hook Pin to adapt to different nichrome wire gauges (AWG) and guarantee a secure grip that resists the vibration of the filling machine.
Special Material Selection: In addition to standard carbon steel and stainless steel, we offer special alloys such as Incoloy or Monel for applications subjected to extreme temperatures or highly aggressive chemicals.
Special Machining: Inclusion of grooves, retention grooves, or recessed necks on the pin body to improve the mechanical anchoring of the sealing plug (epoxy resin, silicone, or glass) at the tube end.
Industrial Packaging: Anti-humidity and anti-oxidation packaging options (VCI bags) for sea shipments or prolonged storage, ensuring the pin surface arrives in optimal conditions for MgO adhesion.
The ideal material depends on the working environment of the tubular heat and the budget:
Nickel-Plated Carbon Steel: It is the industrial standard. The nickel coating offers excellent conductivity and basic protection against oxidation at a low cost. It is ideal for air heats or immersion in oils.
Stainless Steel (AISI 304/316): It is the best option for high humidity applications, contact with water, or corrosive environments. It prevents the formation of oxide that could contaminate the MgO powder and cause insulation failures.
Incoloy or Special Alloys: Reserved for extreme temperatures where the terminal pin is also exposed to high residual heat.
