1、 What is a true 'thin wall'? First, clarify the concept
In the field of electrical construction, "thin wall" is a relative concept, usually referring to galvanized steel pipes with a wall thickness of ≤ 2.0mm.
According to different processes and uses, thin-walled galvanized conduit can be roughly divided into three categories:
type
representative product
Typical wall thickness
core features
Buckling pressure
KBG tube
1.0 / 1.2 / 1.5 mm
Buckling connection, extremely fast construction, low cost
Tight type
JDG tube
1.2 / 1.5 / 1.6 mm
Screw locking, more secure connection, suitable for firefighting
Ordinary welded pipe
Fluid tube restructuring
1.5 / 1.8 / 2.0 mm
Need to self thread or weld, with a cost between the two
Many electricians equate "thin-walled galvanized conduit" with KBG conduit, which is not rigorous.
KBG is just a process school for thin-walled tubes, and there are significant differences among the three in terms of usage scenarios and acceptance standards.
2、 Three core missions of thin-walled galvanized pipes
Regardless of the process, thin-walled galvanized conduit must complete the following three tasks:
1. Mechanical protection (anti smashing, anti rodent, anti construction damage)
If the wires are directly buried in the ceiling, wall or underground, they are easily damaged by subsequent construction (such as nailing and drilling).
Although thin-walled galvanized pipes are not as hard as thick walled steel pipes, they are sufficient to withstand general trampling and slight impacts when the wall thickness is above 1.5 mm.
2. Corrosion and rust prevention (extending service life)
After hot-dip galvanizing treatment, a zinc iron alloy layer is formed on the surface of cold-rolled steel strip, which can effectively block moisture and oxygen in the air, prevent the wires inside the pipe from being damp or corroded by corrosive gases.
3. Auxiliary grounding (equipotential bonding)
Although TN-S or TN-C-S grounding systems are commonly used in modern buildings, metal conduits can still serve as auxiliary pathways for fault currents.
The conductivity of thin-walled galvanized pipes can provide additional leakage paths when the insulation of the wires is damaged.
3、 Selection guide: Don't let "thin wall" become a weakness
When purchasing and using thin-walled galvanized conduit, distinctions should be made based on the nature of the project.
1. Ordinary civil buildings (residential, apartment)
Recommendation: KBG tube (Φ 16, Φ 20)
Reason: Low cost, fast construction, meeting the needs of general lighting and socket wiring.
Attention: If there are heavy equipment (such as large lamps) inside the ceiling, independent supports should be installed at the lamp hanger to avoid relying solely on KBG pipes for load-bearing.
2. Public buildings and commercial complexes
Recommendation: JDG pipes (Φ 20, Φ 25)
Reason: There are dense pipelines in the ceilings of shopping malls and office buildings, and maintenance personnel often walk above. JDG pipes are more firmly connected and have stronger resistance to pulling.
3. Fire and emergency lighting circuits
Recommendation: JDG tube (must be clearly labeled)
Reason: Fire safety inspection has strict requirements for the mechanical strength and grounding continuity of the line, and the use of KBG pipes has been restricted in some areas' fire safety regulations.
4、 The "three checks and one test" of procurement acceptance
The unit price of thin-walled galvanized conduit is not high, but the usage is huge. Poor quality products often manifest as "collapsing and cracking at the first bend and buckle".
Look at the galvanized layer
The surface of high-quality pipes is uniformly bluish gray, with no obvious missed plating or black spots; Poor quality pipes have dark surfaces, flowing zinc nodules, and even localized exposed iron.
Monitor the straightness of the mouth
The pipe opening should be flat and free of burrs. If the pipe mouth is flared outward or severely curled inward, it will hinder wiring and scratch the insulation layer.
Check the compatibility of connectors
Randomly select pipes and fittings for trial installation:
KBG pipes should be able to be smoothly inserted into the fittings and securely fastened without loosening;
JDG pipes should be able to easily screw in claw nuts and can be tightened with a wrench.
Wall thickness measurement (key step)
Measure the actual wall thickness using a caliper.
The nominal pipe size of 1.5 mm shall not be less than 1.3 mm in actual measurement;
Below this value, it is easy to sag or deform under pressure when laid in the ceiling due to its own weight.
5、 Experienced professionals in construction and installation
The bending radius should be sufficient
Thin walled pipes have high elasticity, and a small bending radius can cause rebound, reducing the inner diameter of the pipe and increasing threading resistance.
It is generally recommended that the bending radius be no less than 6 times the outer diameter of the pipe.
Strictly prohibit butt welding
Thin walled pipes have relatively thin walls, and open flame welding is prone to burn through, which can damage the galvanized layer on the inner and outer walls and form a corrosion starting point.
All connections must use matching specialized fittings.
Install a protective sheath on the pipe opening
Before threading, plastic or metal protective covers should be installed at the pipe opening to prevent the insulation layer of the wire from being cut by sharp edges of the pipe opening.
6、 Technical Service Description
Thin walled galvanized conduit is widely used for the protection and management of building electrical systems, and its specifications and connection methods must strictly comply with the design drawings and relevant electrical acceptance specifications.
Before placing an official order, it is recommended to provide specific electrical construction drawings or bill of quantities so that we can assist in reviewing the specifications of the pipes used (such as Φ 16, Φ 20, Φ 25, etc.) and whether the wall thickness meets the design and specification requirements. On the premise of meeting the engineering acceptance standards, we can optimize the procurement plan as much as possible.
