Quality Control
Quality Control 1. Brief Introduction of Quality Control
The company has established ISO9000 system in 1997, and got ISO9001 certificate in 1998. We have got certificate for product Conformity by BUREAU VERITAS, the certificate for product quality BS EN545 by Singapore PSB successively. The import product got SGS certificate.
2. Chart of Quality Control System
 3. Each Section of Quality Control
3.1 Quality Control of Raw Material
For important raw materials such as pig iron, scrap steel, ferroalloy, silicon sand, sand, cement, bitumen and zinc, etc, only qualified suppliers will be nominated, and the suppliers should offer the quality certificate. The material will not be accepted before quality certificate issued and chemical contents and physical properties of samplings tested qualified.
3.2 Quality Control of Molten Iron- Matallographic Examination
Pig iron, scrap steel and ferroalloy must be tested qualified before put into induction furnace.
After adjusted for proper contents, molten iron will be analyzed by model ARJ-3460 vacuum digit spectrometer. Molten iron temperature will be raised to specifications, molten iron will be tapped after the temperature is taken by a quick temperature meter of type of thermocouple.
Molten iron spheroidization quality will be controlled in following ways:
a. To make a triangular sample just at furnace to check its section.
b. To make a sample from the tilting ladle the last moment before casting, quickly making the sample and checking metallurgical structure on the spot. If the grade of spheroidization is found to be over no. 4, the ladle of molten iron from which the sample is taken and the pipes made of with the molten iron in that ladle will be required to put back into furnace.
3.3 Quality Control of Pipe Casting
A high rate of qualified pipes will be gained by controlling casting temperature, skimming slags completely and adjusting the working data of casting machine
precisely.
Cast pipes must be weighted one by one. They will be qualified when their weights comply with requirements of ISO2531-1998 or GB/T13295-2003. And unqualified will be not allowed put into annealing process.
3.4 Quality Control of Core Making
Core contour will be checked one by one, unqualified core will not be permitted to use.
Cores will be checked, taking samples at specified ratio, for their strength, When results are found unqualified, mix proportion must be adjusted and a new batch of material must be prepared.
Core dimensions control includes mainly:
a. To check dimensions of core box periodically and make records. When dimensions are found beyond standard, the box should be repaired in time.
b. To make samples (at ratio of 2%) from a batch of cores. When unqualified cores are found, the rest of the batch must be checked and the dimensions of corresponding box must be checked also. Arrangements will be made to cure the box.
3.5 Quality Control of Mold
New molds must be checked before put in use, only qualified can be used.
After grinding and peening, check the demension and contour one by one, unqualified mold wiil not be permitted to use.
3.6 Quality Control of Annealing
Temperature in different sections of annealing furnace will be strictly controlled as per annealing curve.
After annealing, a ring of 100mm in width, will be cut off from spigot end to check for metallurgical structure. Unqualified must put back into furnace immediately.
After anneaing, pipes will be check for mechanical properties as per ISO2531-1998 or GB/T13295-2003, The requirements are given in table as follows:
When the samples are checked unqualified, double samples will be taken from the batch from which original samples are taken to have a check. When the results are still not acceptable, this batch of pipes must be checked one by one, unqualified will be put back into furnace.
3.7 Quality Control of Finishing
After finishing, each pipe will be checked for contour, the elipse should corrected, small defects on external surface will be repaired to meet the requirements of standard
Each pipe will be checked for dimensions of socket and spigot to meet requirements of ISO2531-1998 or GB/T13295-2003.
3.8 Hydrostatic Test
Hydrostatic testing will be applied to each pipe. Pressure and time of pressure holding required as follows: 5MPa for DN100-300mm, 4MPa for DN350-600mm, 3.2MPa for DN700mm. Pressure will be kept for 10 seconds at least.
The hydrostatic pressure test will be recorded as specification.
3.9 Airtight Test
3.10 Quality Control of Cement Lining
Cement lining thickness will be controlled as per ISO4179, measurement of thickness will be made as per specification, A steel pin will be used to measure when cement lining is wet, and ultrasonic thickness tester will be used when the lining is dry.
Each pipe will be checked for appearance of cement lining. Defects such as ridges, exposure of sand and lining damaged will not be allowed.
3.11 Quality Control of Zinc Coating
The mass of zinc layer will be 130g/m2 or more as per ISO8179.
Before zinc coating, the external surface of pipes must be dry, free from rust and non-adhering particles. The layer must be even without displaying bare patches.
3.12 Quality Control of Bitumen Coating
Average thickness of bitumen coating will be 70um or more as per requirements of ISO8179. A standard gauge will be used to measure when the coating is wet. When the coating is dry, thickness tester will be used.
Bitumen coating will be even and marks will be painted legibly and durably. Complying with relevant requirements.
Brand coating must be even triking and comply with relevant requirements.
3.13 Quality Control of Packing and Storage
Pack the products which need to be packed as per customas’ requirement. After packing, check for the fastness, qualified will be storaged.
The finished products should be checked before shipping, qualified will be shipped.
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