스프링클러설비의 배관 부식에 대한 원인 분석과 개선방안에 관한 연구

Abstract

In order to elucidate the causes of pipe corrosion in the sprinkler system, the problems were identified through the derivation of the planning stage problem and the analysis of the water quality in the fire safety water tank for maintenance, and through the experiments applying corrosion inhibitors as an improvement measure, the following conclusions were obtained.

1) The analysis using scanning electron microscopy(SEM) and energy-dispersive X-ray spectroscopy(EDS) to characterize the copper pipes in the sprinkler system showed that Cu was reduced by 30.12 wt%, and O and C increased by 19.85 wt% and 5.91 wt%, respectively, in the leaked pipe compared to the new one.

2) As for the problem of the change of pressure and flow rates due to aging of the pipe, when the friction loss coefficient of the pipe after 20 years of use was 90, the pressure was 0.0704 MPa and the flow rate 67.1 lpm at the terminal head, which did not satisfy the National Fire Safety Standards(NFSC).

3) In order to solve the problem of the 20-year-old pipe, the pump specifications of 2,600 lpm × 125 m were changed to 2,800 lpm × 155 m, and the use of the carbon steel pipe for pressure piping, which had been used only on the first basement floor, was expanded as the piping material up to 5 stories above the ground. It was confirmed that the pressure(0.1 MPa) and flow rate(80 lpm) at the terminal head required by the National Fire Safety Standards(NFSC) were satisfied.

4) As for the problem of the change of pressure and flow rates due to aging of the pipe, when the friction loss coefficient of the pipe after 30 years of use was 80, the pressure was 0.0584 MPa and the flow rate 61.1 lpm at the terminal head, which were inferior to the performances of the 20-year-old pipe.

5) In order to solve the problem of the 30-year-old pipe, the pump specifications of 2,600 lpm × 125 m were changed to 2,800 lpm × 155 m, and the use of the carbon steel pipe for pressure piping, which had been used only on the first basement floor, was expanded as the piping material up to 8 stories above the ground. As a result of such expanded application, it was confirmed that the pressure and flow rate at the terminal head conformed to the National Fire Safety Standards(NFSC).

6) The water quality analysis of the fire safety water tanks in three regions across the country confirmed that the water was in the quality that caused pipe corrosion as follows. (1) In the Busan region, 1,200 CFU/ml of general bacteria, which was 12 times higher than the value for the standard water quality, 100 CFU/ml or less, were detected, and the general E. coli was also detected. (2) In the Cheongju region, the turbidity was 0.99 NTU, which was approximately twice the standard value of 0.5 NTU. (3) In the Seoul region, 1,900 CFU/ml of general bacteria were detected, which was 19 times higher than the standard value for the water quality, 100 CFU/ml or less. (4) The water quality analysis in Busan, Cheongju and Seoul showed that pH 7 or lower and the water contained the components that could damage the protective film.

7) Through the experiment of injecting the fire safety water containing the corrosion inhibitor after discharging the existing fire safety water(tap water) inside the copper pipes for fire fighting facilities in 5 regions across the country, It was confirmed that the corrosion inhibitor is effective in improving the corrosion of pipes and reducing leakage. The following shows the experimental results of A (Jinju) area. (1) The water quality analysis showed that the average pH variated from 8.586 to 11.194 after the corrosion inhibitor injection into 5 copper pipes. (2) The average ORP decreased from -108.18 mV to -261.36 mV after the corrosion inhibitor injection into 5 copper pipes. (3) The average EC increased from 0.326 ms/cm to 4.889 ms/cm after the corrosion inhibitor injection into 5 copper pipes.

8) The results of analyzing the components attached to the surface of the sprinkler system according to the concentration and the impregnation period of the corrosion inhibitor in order to check whether the single molecule silica film was deposited on the copper pipe of the sprinkler system are as follows. (1) The component analysis after impregnation with 10,000 ppm of the corrosion inhibitor for 5 days showed that Cu decreased from 60.34 wt% to 20.57 wt% while O increased from 24.03 wt% to 62.28 wt%, and Si increased by 2.0 wt%. (2) The component analysis after impregnation with 10,000 ppm of the corrosion inhibitor for 10 days showed that Cu decreased from 67.72 wt% to 20.04 wt% while O increased from 23.71 wt% to 66.20 wt%, and Si increased by 1.97 wt%. (3) The component analysis on the surface after impregnation with 15,000 ppm of the corrosion inhibitor for 5 days showed that Cu decreased from 63.88 wt% to 2.61 wt% while O increased from 23.88 wt% to 85.96 wt%. (4) The component analysis after impregnation with 15,000 ppm of the corrosion inhibitor for 10 days showed that Cu decreased from 64.67 wt% to 6.38 wt%, while O increased from 24.34 wt% to 76.38 wt%, and Si increased by 4.59 wt%. (5) The component analysis on the surface of the copper specimen after impregnation with 100,000 ppm of the corrosion inhibitor for 10 days showed that Cu decreased from 55.93 wt% to 7.60 wt% while O increased from 24.65 wt% to 55.24 wt%, and the Si increased by 11.55 wt%.