The Difference Between Hot Dip Galvanized Steel Pipe and Hot Dip Galvanized Steel Pipe SC

What are the differences between hot dip galvanized steel pipe and hot dip galvanized steel pipe SC? Let us have a look.

I. The expression of hot galvanized steel pipe and hot galvanized steel pipe SC is different:

1. Hot dip galvanized steel pipe generally refers to the standard nominal diameter of the water pipe, and the writing symbol is expressed with DN.

2. Hot dip galvanized steel pipe SC means that the wire is laid through steel pipe (low-pressure fluid welded steel pipe). SC is a common welded steel pipe, which is equal to DN of water pipe.  SC is the concealed welded pipeline. Generally, the wall of the pipe is thick. S stands for the pipe material and C stands for the laying method.

II. The technology of hot galvanized steel pipe and hot galvanized steel pipe SC is different:

1. Hot dip galvanized steel pipe has thick coating, so it has strong anti-corrosion ability. Hot dip galvanized steel tube SC is uniform, the surface quality is better, and the coating thickness is generally between a few microns to more than ten microns. Hot dip galvanizing is a chemical treatment and belongs to electrochemical reaction.

2. Hot dip galvanized steel pipe SC takes physical treatment. There is only a layer of zinc on the surface but no galvanization inside, so hot dip galvanized steel pipe SC is easy to fall off. Hot dip galvanizing is often used in building construction.

3. The common point of hot dip galvanized steel pipe and hot dip galvanized steel pipe SC is that they both belong to galvanized steel pipe.

III. Technical requirements for hot dip galvanized steel pipe

1. Brand number and chemical composition

The brand number and chemical composition of the steels for hot-dip galvanized steel pipes shall conform to the brand number and chemical composition of the steels for clarinets specified in GB/T3092.

2. Manufacturing method

The clarinet manufacturing method (furnace welding or electric welding) is at the manufacturer's option. Hot dip galvanizing method is adopted for Galvanization.

3. Thread and pipe joints

(a) For galvanized steel pipes delivered with threads, the threads shall be made after galvanized. The thread shall conform to YB 822.

(b) Steel pipe joints shall comply with YB 238; malleable cast iron pipe joints shall comply with YB 230.

4. Mechanical properties

The mechanical properties of steel pipes before galvanizing shall conform to GB 3092.

5. The uniformity of galvanized layer

Galvanized steel pipes shall be tested for the uniformity of galvanized coating. The steel pipe sample shall not turn red (copper plating) after being continuously impregnated in copper sulfate solution for 5 times.

6. Cold bending test

Galvanized steel pipes with nominal diameter not greater than 50 mm shall be subjected to cold bending tests. The bending angle is 90° and the bending radius is 8 times of the outside diameter. There should be no filling in the test, and the weld of the sample should be placed outside or upper of the bending direction. After the test, there should be no cracks and zinc spalling on the sample.

7. Hydrostatic test

The hydrostatic test should be carried out in the clarinets, and eddy current inspection can be used instead of hydrostatic test. The test pressure or the specimen size of the eddy current inspection should conform to GB 3092. The mechanical property of steel is an important index to ensure the final service property of steel.