GB/T 28897-2021Steel-plastic compound pipes and fittings for fluid service (English PDF)

3.6 Maleableiron fittingsofliningplastic

The malleable cast iron pipe is lined with an injection molding process with a plastic core connected by the interface core (3.7) and the lining plastic layer. Accessories.

Note: Referred to as plastic-lined pipe fittings.

3.7 Interfacecore

The part in the plastic core of the plastic-lined pipe fitting that is connected with the (lined) plastic-coated composite steel pipe nozzle and prevents the pipe end from being corroded by contact with water.

3.8 Grooved pipe fittings

Pipe joints and pipe fittings used for pipe groove connection.

Note: Grooved pipe joints refer to quick-assembled joints composed of split clamps, rubber seals and fasteners; grooved pipe fittings are mainly grooved connections The general term for pipe fittings such as elbows, tees, crosses, and reducers used in piping systems.

4.1 Classification and code of steel-plastic pipe

4.1.1 The classification and code of steel-plastic pipes according to the composite process of the inner and outer anticorrosive layers are as follows.

a) Plastic-lined composite steel pipe, codenamed SP-C;

b) Plastic coated composite steel pipe, codenamed SP-T;

c) Composite steel pipe covered with plastic, codenamed SP-F.

4.1.2 The steel-plastic pipes are classified as follows according to the conveying water.

a) The plastic material color of steel-plastic pipes for cold water and steel-plastic pipes for drinking water should be white or blue; steel-plastic pipes for rainwater or other drainage The color of the plastic material of the tube shall be negotiated between the supplier and the buyer;

b) The color of the plastic material of the steel-plastic pipe for hot water should be red;

c) The color of the plastic material of the steel-plastic pipe for fire fighting water should be red.

4.1.3 The classification and codes of steel-plastic pipes according to lining, coating and plastic coating materials are as follows.

a) Polyethylene, codenamed PE;

b) Heat-resistant polyethylene, codenamed PE-RT;

c) Cross-linked polyethylene, codenamed PE-X;

d) Polypropylene, codenamed PP;

e) Rigid polyvinyl chloride, codenamed PVC-U;

f) Chlorinated polyvinyl chloride, codenamed PVC-C;

g) Epoxy resin, codenamed EP.

4.1.4 The product mark of the steel-plastic pipe is composed of the code of the composite process of the anti-corrosion layer, the code of the material of the plastic layer and the nominal size. Example 1.

The plastic-lined composite steel pipe with nominal size of DN100 and lined with chlorinated polyvinyl chloride is marked as. SP-C-(PVC-C)-DN100. Example 2.

The plastic-coated composite steel pipe with nominal size of DN80 and epoxy resin coated is marked as. SP-T-(EP)-DN80. Example 3.

The plastic-coated composite steel pipe with nominal size of DN50 and plastic-coated polyethylene is marked as. SP-F-(PE)-DN50. Example 4.

The steel-plastic pipe with nominal size of DN100, lined with chlorinated polyvinyl chloride and coated with plastic polyethylene, is marked as. SP-C-(PVC-C)-F-(PE)-DN100.

4.2 Classification and code of pipe fittings

4.2.1 Steel-plastic composite pipe fittings are classified as follows according to the internal and external anti-corrosion layer composite process.

a) Plastic-lined pipe fittings;

b) Plastic-coated pipe fittings;

c) Covered with plastic pipe fittings.

4.2.2 The classification and code of steel-plastic composite pipe fittings according to lining, coating and plastic coating materials are as follows.

a) Polyethylene, codenamed PE;

b) Heat-resistant polyethylene, codenamed PE-RT;

c) Cross-linked polyethylene, codenamed PE-X;

d) Polypropylene, codenamed PP;

e) Rigid polyvinyl chloride, codenamed PVC-U;

f) Chlorinated polyvinyl chloride, codenamed PVC-C;

g) Epoxy resin, codenamed EP.

4.2.3 The classification and code of steel-plastic composite pipe fittings according to the connection mode are as follows.

a) The classification and code of plastic-lined pipe fittings should meet the requirements of Appendix B;

b) The classification and code of grooved pipe joints should meet the requirements of Appendix C;

c) The classification and code of steel butt-welded pipe fittings should meet the requirements of GB/T 13401 and GB/T 12459;

d) For other connection methods, the classification and code of pipe fittings should meet the requirements of the corresponding product standards.

6.1 Steel plastic pipe

6.1.1 Base pipe size and allowable deviation

The size and allowable deviation of the base pipe shall comply with the requirements of the documents implemented by the base pipe.

6.1.2 Length

6.1.2.1 Normal length

The usual length of steel-plastic pipe is 3000mm~12000mm.

6.1.2.2 Cut-to-length length

The cut-to-length length of the steel-plastic pipe is generally 6000mm or 12000mm. When the nominal size is not greater than DN200, its allowable deviation It is 150 mm; when the nominal size is greater than DN200, the allowable deviation is 500 mm.

6.1.2.3 Range length

Steel-plastic composite seamless steel pipes can be supplied in a range of lengths, and the range length should be within the usual length range.

6.2 Fittings

6.2.1 The size and shape of plastic-lined pipe fittings should meet the requirements of Appendix B.

6.2.2 The size and shape of the grooved pipe connection shall meet the requirements of Appendix C.

6.2.3 The size, tolerance and shape of butt-welded pipe fittings should meet the requirements of GB/T 12459. The outer diameter series of pipe fittings should be selected in accordance with the outer diameter of the pipe.

The diameter series are the same or determined through negotiation between the supplier and the demander.

6.3 Plastic layer of steel-plastic pipes and fittings

6.3.1 The thickness and allowable deviation of the plastic layer of the plastic-lined composite steel pipe and the plastic-coated composite steel pipe shall meet the requirements of Table 1.

6.3.2 The minimum thickness of the plastic layer of the plastic-coated composite steel pipe shall meet the requirements of Table 2.

D.1 Principle

Under the program control temperature, the relationship between the power difference (such as in the form of heat) input to the sample and the reference substance and the temperature is measured. Differential scan The curve recorded by the calorimeter is called the DSC curve, which is based on the rate at which the sample absorbs or releases heat, that is, the heat flow rate dH/dt (unit mJ/sec) as the vertical position.

Mark, with temperature T or time t as the abscissa, used to determine the glass transition temperature Tg and heat of reaction deltaH of epoxy powder.

D.2 Test instruments and tools

D.2.1 Differential scanning calorimeter (DSC instrument) with refrigeration equipment. D.2.2 Analytical balance, accurate to 0.1mg.

D.2.3 Specimen sealer

D.2.4 Aluminum sample cuvette with lid.

D.3 Test procedure

D.3.1 Take (10±1) mg of epoxy powder as a sample, put it into the pre-weighed sample cuvette, close the lid, seal the sample, and weigh it. The mass is accurate to 0.1mg.

D.3.2 Put the sample and reference into the measuring cell of the differential scanning calorimeter protected by dry inert gas.

D.3.3 Complete its thermal scan according to the following operating procedures.

a) Heat the sample at a rate of 20°C/min, from (25±5)°C to (70±5)°C, then quench the sample to (25±5)°C

5)°C;

b) Heat the same sample at a rate of 20°C/min, from (25±5)°C to (285±10)°C, and then quench the sample to (25±5)°C;

c) Heat the same sample at a rate of 20°C/min, from (25±5)°C to (150±5)°C.

D.4 Test results

Correspond to each thermal scan line obtained in b) and c) in D.3.3, determine its corresponding Tg value, these values are extrapolated at the low temperature end At the intersection of the baseline and the tangent at the turning point of the curve. In addition, determine the corresponding reaction heat deltaH (see Figure D.1).

G.1 Principle

After the epoxy resin coated composite steel pipe sample is soaked in high temperature hot water, the surface coating of the sample is peeled off with a suitable tool.

The size of the coating area evaluates the adhesion performance of the coating.

G.2 Test instruments and tools

G.2.1 Beaker with a diameter of more than 100mm. G.2.2 A thermometer with a range of 100°C. G.2.3 A cutter that can cut through the plastic layer.

G.3 Sample

The sample should be a part of a straight plastic-coated tube, the length of the sample is about 100mm, and it should be longitudinally cut along the axis; if a test plate is used instead, The length of the test panel is 100mm, and the width of the test panel is 50mm. For epoxy resin composite steel pipes with a nominal diameter of not less than DN200, available DN150 steel pipes of the same material and coating process can be used instead of testing, and the same coating process can also be used on steel plates of the same material and thickness. Art's test board is used to make samples instead.

G.4 Test procedure

G.4.1 Put the sample into the beaker, and add distilled water to the beaker to completely immerse the sample.

G.4.2 Heating to (75±3)°C for 4.8h or heating to (95±3)°C for 24h, then take out the sample.

G.4.3 When the sample is still warm, immediately use a knife to scratch a rectangle of about 15mm×30mm on the coating, and the knife mark should penetrate the coating.

It reaches the base tube and then cools to room temperature naturally in the air.

G.4.4 Within 1h after taking out the sample, insert the tip of the knife under the coating from any corner of the rectangle, and peel off the coating with horizontal force.

Push the tip of the knife until the coating inside the rectangle is all pried off or the coating shows obvious pry resistance.

G.5 Evaluation of results

Evaluate the adhesion level of the rectangular inner coating according to the following classification standards.

a) Level 1-the coating obviously cannot be peeled off by prying;

b) Level 2-the coating being pried off is less than or equal to 50%;

c) Level 3---The coating that has been pried off is greater than 50%, but the coating shows obvious prying resistance;

d) Level 4-the coating is easily peeled off into strips or large pieces;

e) Level 5---the coating is peeled off as a whole piece.

I.1 Principle

This method uses NaCl solution to accelerate the corrosion of the joints of the plastic-lined pipe fittings composing the pipeline system, and judges that the plastic layer of the plastic-lined pipe fittings blocks the transmission The index of the ability of the conveying medium to contact iron.

I.2 Test equipment

I.2.2 Iron hollow cathode lamp

I.2.3 Acetylene cylinder or acetylene generator.

I.2.4 Air compressors should be equipped with water removal, oil removal and dust removal devices. I.2.5 General laboratory glass and plastic utensils.

I.3 Specimen

I.3.1 Plastic-lined pipe fittings. DN20 outer joints, 2 in number.

I.3.2 Lined (coated) plastic steel pipe. 4 sections of DN20 lined (coated) plastic steel pipe, the length of the short pipe is 600mm. For other specifications of steel and plastic pipes, pipes The length of the segment is determined when the internal volume of the assembled component exceeds 300mL. According to the requirements of GB/T 7306.2, pipe threads are processed at one end of the pipe.

I.3.3 The rubber sealing ring or pipe thread anaerobic sealant that meets the requirements of this document.

I.4 Sample assembly

I.4.1 The two sections of lined (coated) plastic steel pipe are a group, the thread length of one group is the standard length, and the other group is the standard length minus 2 teeth.

I.4.2 As shown in Figure I.1, assemble two sets of sample groups according to the normal construction requirements. I.4.3 Thread sealing adopts raw PTFE tape.