Standard No.:	GB/T 17650.2-1998
Chinese Name:	取自电缆或光缆的材料燃烧时释出气体的试验方法 第2部分:用测量pH值和电导率来测定气体的酸度
English Name:	Test on gases evolved during combustion of materials from cables Part 2:Determination of degree of acidity of gases by measuring pH and conductivity
Professional Classification:	K13 Cable and its accessory
Professional Classification:	GB National Standard
ICS Classification:	29.060.01 Electrical wires and cables in general
Issued by:
Issued on:	1998-01-02
Implemented on:	1999-10-01
Status:	VALID
Language:	English
File Format:	PDF
Word Count:
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1 Scope

Part 2 of this standard specifies a method for the determination of the degree of acidity of gases evolved during the combustion of compounds taken from the components of electric or optical cables.

Note 1: The relevant cable standard should indicate which components of the cable should be tested, and which method of calculation (see clause 8) should be used in the case of dispute.

Note 2: For the purposes of this standard the term “electric cable” covers all insulated metallic conductor cables used for the conveyance of energy or signals.

2 Principle of the Method

A pre-determined quantity of the test material is burned in a tube furnace. The evolved gases are trapped by bubbling through bottles filled with distilled or demineralized water.

The acidity is measured by determination of pH value. The conductivity of the solution is also measured.

3 Test Apparatus

The principle diagram of the apparatus is shown in Figures 1 to 5.

The assembly of the components which constitute the test apparatus shall be leak-tight. The connections between the tube and the first wash bottle and between the first and the second wash bottle shall be as short as possible.

3.1 Tube furnace

The effective length of the heating zone of the furnace shall be 500 mm to 600 mm and its inside diameter 40 mm to 60 mm. It shall be equipped with an adjusted electric heating system.

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3.2 Tube

The furnace contains a fireproof tube made of silica resistant to the action of corrosive gases. The tube shall be approximately concentric to the tube furnace. The inside diameter of the silica tube shall be within the limits of 32 mm to 45 mm. The initial clearance shall only allow for thermal expansion. The tube protrudes on each side by a length L of:

— on the entrance side: 60 mm ≤ L ≤ 200 mm;

— on the exit side: 60 mm ≤ L ≤ 100 mm.

3.3 Combustion boats