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1 Journal of the Korea Academia-Industrial cooperation Society Vol. 17, No. 11 pp , ISSN / eissn 스프링클러시스템에서조도계수에따른 CPVC 배관마찰손실영향의연구 강웅일호남대학교소방행정학과 A study on the effects of Friction loss of CPVC pipe according to Roughness coefficient in a sprinkler system Ung Il Kang Department of fire Service Administration, Honam University 요약배관내에유체가흐를때사용되는유체의물리ㆍ화학적성질에따라배관재질이선택이결정된다. 수계소화설비에사용하는유체는대부분물을사용하므로물속에용해된각종이물질들은관벽에스케일을발생시키고부식및배관노후화를촉진하여마찰손실을증가시켜펌프의효율을저하시킨다. 이러한요인을가져오는강관의대체가능한 CPVC 배관은부식에강하고, 매끄러운조도를가지고있어서유체이송능력이뛰어나고배관무게가가볍고접착제결합방식의배관작업으로시공성이우수한점을들수있다. 그래서설계및시공단계에서마찰손실을줄이기위해 Hazen-Williams 식을 CPVC(Chlorinated Poly-Vinyl Chloride) 배관에적용하여조도계수에따라마찰손실을조사하였다. 실제아파트현장에서의적용사례를통해조도계수의차이에따라손실수두를조사한결과조도계수의수치가 120 인강관일때마찰손실은 76.64MPa 이고 150 인 CPVC 배관일때마찰손실은 MPa 로서 34% 정도의마찰손실이개선되었음을확인하였다. 또한시공비절감차원에서는강관으로시공할때 1,585,158 원이고 CPVC 배관으로시공시에는 931,842 원으로 41% 정도의시공비가절감되는것을확인하여전체설비용량의감소로인한소화시스템의안정성향상및시공비를절감할수있는것을알수있었다. Abstract The pipe material is selected according to the physical and chemical properties of the fluid flowing within it. Because the fluid used in fire extinguish systems is water, the various foreign substances dissolved in it cause scale to form on the pipe wall and accelerate the corrosion and aging of the pipe itself. This results in an increase in the friction loss and eventually degrades the efficiency of the pump. The use of CPVC (Chlorinated Poly-Vinyl Chloride) pipes was confirmed to reduce the friction loss compared to conventional steel pipes in the design and stages. The friction loss was found to be 76.64MPa with a C-value of 120 for the steel pipe and MPa with a C-value of 150 for the CPVC pipe in an actual apartment environment. It was confirmed that the friction loss was improved by about 34% when using the CPVC pipe. When the steel and CPVC pipes were employed in the, the costs were 1,585,158 and 931,842 won, respectively. Therefore, it was shown that the cost was reduced by about 41%. We investigated the safety of the fire extinguishing system and the improvement in the economic performance due to the reduction in the total installed capacity by studying practical applications in the field Keywords : Construction cost, Chlorinated Poly-vinyl chloride, Economic improvement, Friction losses, Pipe material. 본논문은한국전력공사학술연구용역 ( 과제번호 : E ) 과제로수행되었으며연구비지원에감사드립니다. * Corresponding Author : Ung Il Kang (Honam Univ.) Tel: uikang@honam.ac.kr Received September 26, 2016 Accepted November 10, 서론 스프링클러설비에서소화배관의재질선택은제반성 능을발휘하는데매우중요하다. 소화배관재질에따라마찰손실을줄일수있어최근에는기존강관재질대신 CPVC 배관을사용하는현장들이증가되고있다. 기존 Revised (1st October 18, 2016, 2nd November 3, 2016, 3rd November 9, 2016) Published November 30,

2 한국산학기술학회논문지제 17 권제 11 호, 2016 강관은용접및절단작업시기계마찰소음이많고작업장주변으로방출되는용접가스와쇳가루등으로공사현장의환경저해요소가많으며용접절단작업등으로화재가빈번히발생하여인명과재산피해등의손실을가져오는경우가많다. 반면, CPVC배관은배관자재비가강관에비하여저렴하고부식및스케일에강하여배관수명이길어건물철거시까지는배관을교체하지않아도되고, 프라이머및솔벤트시멘트 (Solvent Cement) 접착제결합방식으로배관이음을하므로시공이간단하여비숙련작업자도현장에서쉽게배관이음작업을수행할수있어공사기간단축과인건비절감의효과가있으므로더욱확대되어적용될것으로보인다 [1,4]. CPVC배관에대한국내의연구사례를살펴보면현재까지국내의소방설계진행방식으로규약배관방식 (Pipe Schedule System) 의안전계수의초과적용으로인한과다설계가도출되어최근에는소방시설공사의원가절감을위한차원에서창의적사고를갖고비용절감과성능실현을함께고려하는 VE(Value Engineering) 개념을도입하여화재방호역할을위해건물에설치되는스프링클러시스템에대한 VE설계를수행하기위하여다양한수리해석방식의연구와스프링클러의효과적인소화성능을구현하기위한소화배관, 펌프, 헤드등의상호배치구성방식에따른스프링클러소화설비를효과적으로설계하기위한수리해석접근방식을제시하였다 [1,2]. 국외에서는 NFPA의 13(2010 edition) 스프링클러시스템의표준화된설치기준을마련하였다. 제6장에서스프링클러시스템의구성요소와하드웨어의올바른사용에대한요구사항이제시되었고 ASTM F 442 특별한나열염소화폴리염화비닐 (CPVC) 파이프비금속배관사양 을표준으로하고있다 [3 * ]. 또한이론식을두가지로정리하였고, Hauzen-williams식을통한배관의선형길이당압력강하를배관별유량에따라정리하여마찰손실을개선할수있는방법을알아보았다 [4]. 따라서본연구에서는스프링클러시스템의강관에서발생하는부식및스케일에따른관경축소로인한마찰손실이커지므로매끈한관조도로배관조도계수가큰 CPVC배관을 Hazen-Williams식에적용하여전체소화배관시스템에서마찰손실을줄일수있는개선방안에대한방법을제안하고, 실제아파트현장에적용하였을때구체적인마찰손실과시공비의절감효과에대하여제 시하였다. 2.1 유체역학적고찰 2. 본론 Hazen-Williams식은배관유동의흐름영역이주로천이영역및난류영역에서적응성이뛰어난실험을바탕으로얻어진마찰손실계산식이다. 배관마찰에대한이론적기반이취약한시기에개발된실험식으로서현재까지도물을사용하는유동ㆍ에너지손실관계식으로배관의수리계산시에가장널리사용되고있다. 배관의선형길이당압력강하에대해정리하면다음과같다. 위식을 SI단위로표현하면, (1) 여기서, 배관 1m 당압력손실 (L/min) : 관의유량 D(mm) : 관의내경 C : 배관의조도본식을적용하기위한전제조건으로사용유체는물이고수온은 7.2~24 정도비중량 9,800N/ m3유속은 1.5~ 5.5 m/sec 범위의유동상태에서결과값이잘들어맞는배관마찰계산식이다. 화재안전기준 (NFSC103 제8조 3 항 ) 에따르면배관의구경은수리계산에따르는경우가지배관의유속은 6m/s, 그밖의배관의유속은 10m/s를초과할수없으므로속도수두를무시하고이식으로적용할수있다. 이식은 Darcy-Weisbach식에서의 " 관마찰계수 ( )" 에대응하는 " 관조도 (C-value)" 항목이있고, 손쉽게계산할수있도록배관재질에따라유체공학자들이이미정해놓은값들이있다 [5]. 일반적인배관의마찰계수값은 Hazen-Williams 식을적용하여 Table. 1과같이규정하고있다. 또한, NFPA 13(2010년 ) 에따라 Table. 2와같이적용하여배관마찰손실압력을계산해낼수있다. 유체가배관내를흐를때마찰손실을구하는이론식은여러방법이있으나일반적으로유체역학에서는배관의마찰계산에서 Darcy- Weisbach의식을사 용한다. 실험에의하면실수두는속도수두 ( ) 와배관 길이 (L) 에비례하고관경 (d) 에반비례한다. 1) NFPA 13(2010 edition) May ( 주석확인 ) 356

3 스프링클러시스템에서조도계수에따른 CPVC 배관마찰손실영향의연구 Table 1. Value of friction losses for the pipe Type of pipe "C" Value Copper pipe, CPVC 150 Galvanzing Zincing pipe, Black steel pipe (wet, deluge) 120 Black steel pipe (dry, Pre-action) 100 Table 2. Hazen-Williams C values Pipe or Tube "C" Value Plastic(listed) all 150 Copper pipe or stainless steel 150 Black steel (wet systems including deluge) 120 Galvanzing Zincing pipe, Black steel pipe (wet, deluge) 120 Black steel pipe (dry, Pre-action) 100 이때비례상수를 ( 관마찰계수 ; Friction factor) 라하면 는유체의밀도, 점성등에관계되는무차원의값으로이를정리하면다음과같은공식이된다. ㆍ ㆍ (2) Table. 3에서는 Hazen-Williams 식과 Darcy-Weisbach 식을비교하여나타내었고 Table. 4는마찰손실의원인및개선방법을나타내고있다. 2.2 배관의설계방법소화배관의재질선택은사용조건과환경에따라배관의진동, 충격, 수압, 사용유체의온도, 부식성, 용접절단등의가공성등을고려하여야한다. 사용온도는 -1 5~350 에서는일반탄소강관을사용하고, 그밖의고온, 극저온에서는특수합금관을사용한다. 사용압력은 1.2MPa 이하에서는일반배관용탄소강관, 1.2~10MPa 에서는압력배관용강관을사용한다. 유속은고속흐름일수록배관동압이증가되어소음진동이발생하고, 관벽 Table 3. Comparison between Hazen-Williams and Darcy-Weisbach equations Division Hazen-Williams equation Darcy-Weisbach equation Objective fluid Using only water Using all fluid Characteristic Friction losses calcination by physical characteristic for pipe Friction losses calcination by physical properties and fluid properties for pipe Advantage, Disadvantage Be easy to use "C" as friction losses Using the Reynolds number, apply Table 4. Cause and Improvement of friction losses Division The main cause of friction losses Improvements Friction losses in pipe Local resistance loss Friction between the fluid and the surface in pipe Turbulent fluid Viscosity of the fluid Change of diameter Bending of the tube valve fittings in pipe Using a large pipe with values of roughness The flow of fluid is the laminar flow The temperature of the fluid is lower The rapid expansion and reduction of diameter To minimize bending places To minimize bending fitting in short pipe 357

한국산학기술학회논문지제 17 권제 11 호, 2016 (a) Passing of seven years (b) Passing of thirteen years (c) Passing of seventeen years (d) Passing of twenty-one years Fig. 1. The process of passing of year for steel pipe Table 5.

(self-extinguishing) 1,427~1,538 1,427~1,538 Maximum ambient termperature Installation site Specific heat (cal/g ) Heat conductivity (w/m K) 66 No limit No limit wet sprinkler (semi nonflammable over

12 52 247 Corrosion sensitivity low high medium Flow coefficient (C value change) Weight (Kg/25 code) Bonding method 150 (no change) 120 (decrease) 130 (decrease) 0.401 2.46 0.

강관은유속 1~2m/s이하에서는부식의우려가없으나 9~10m/s 이상에서는부식방지대책을수립해야한다. Fig. 1은강관의부식에따른경년변화를나타낸것이다. 동관이나 CPVC의경우상대적으로부식의우려가적다 [6].

4 한국산학기술학회논문지제 17 권제 11 호, 2016 (a) Passing of seven years (b) Passing of thirteen years (c) Passing of seventeen years (d) Passing of twenty-one years Fig. 1. The process of passing of year for steel pipe Table 5. Characteristic comparison of the pipe Heat resistance Corrosion protection flow Performance Construction ability Durability Piping material CPVC Steel pipe Copper pipe Melting point 160 (self-extinguishing) 1,427~1,538 1,427~1,538 Maximum ambient termperature Installation site Specific heat (cal/g ) Heat conductivity (w/m K) 66 No limit No limit wet sprinkler (semi nonflammable over insulation place) No limit wet sprinkler Corrosion sensitivity low high medium Flow coefficient (C value change) Weight (Kg/25 code) Bonding method 150 (no change) 120 (decrease) 130 (decrease) solvent adhesives joint type screw type, welded type, grooved type welded type (solder, braze) life span semipermanent 10~20 yeras 40~60 years Replacement cost none occurrence none 에서는부식이가속화된다. 강관은유속 1~2m/s이하에서는부식의우려가없으나 9~10m/s 이상에서는부식방지대책을수립해야한다. Fig. 1은강관의부식에따른경년변화를나타낸것이다. 동관이나 CPVC의경우상대적으로부식의우려가적다 [6]. 현행국가화재안전기준 (NFSC 103 제8조제1항, 제2항 ) 에등록된소화배관종류로는일반배관용탄소강관 (KS D 3507), 압력배관용탄소강관 (KS D 3562), 이음매없는동및동합금관 (KS D 5301), 배관용스테인리스강관 (KS D 3576) 성능시험기술기준에적합한소방용합성수지배관 ( 일명 CPVC 배관 ") 이있다 [7]. Table. 5는현재가장많이사용되는강관, 동관및 CPVC배관의특성을비교한것을나타내고있다 [8]. 3. 결과및고찰아파트단위세대 (84형) 의스프링클러설비를 Fig. 2 와같이설계하고 Table. 6으로수량을산출을하여 Hazen-Williams식에적용하였다. 배관의마찰손실을개선하기위하여강관과 CPVC배관을비교한결과, Table. 7과같이마찰손실의변화를나타내었고마찰손실값의변화를 Fig. 3으로나타내었다. 그리고실제로 CPVC배관과강관공사에필요한재료비와인건비를보여주는일위대가표를 Table. 8과 9로나타내었으며, 강관으로설계하였을경우마찰손실이커짐에따라펌프의전양정및전동기용량이커지게되어전체설비의비용또한증가하므로 CPVC배관으로변경할경우, 시스템의비용절감이가능함을알수있었다. 아래의 Fig. 4, 5는설 358

5 스프링클러시스템에서조도계수에따른 CPVC 배관마찰손실영향의연구 계도면에의한강관과 CPVC배관을현장에서시공한사례를보여주고있다. 또한, 시공비측면에서도 CPVC배관을사용하였을경우, 배관결합방식이나사및용접, 플랜지, Grooved, 분기배관방식을적용하는강관에비해본드결합방식으로좁은공간에서도시공이편리하며, 열전도율이매우 낮아결로현상이발생하지않으므로보온재를생략할수있어 Table. 10에서와같이세대당자재비와인건비를대략 41% 가량원가를절감할뿐아니라장기내구성이우수하여시간경과에따른배관의수명및교체비용등의유지보수비용이거의발생하지않아강관에비하여유리하다는것을알수있었다. Fig. 2. The design drawings of sprinkler system for apartment units Table 6. Calculate of quantity the fire pipe in household Diameter (A) Flow (LPM) 90 Elbow 90 divided flow TEE 90 direct flow TEE Conversion length(m) straight pipe (m)

6 한국산학기술학회논문지제 17 권제 11 호, 2016 Table 7. Comparison of loss of head between Steel pipe and CPVC pipe Loss of head : (MPa) Diameter(A) Steel pipe CPVC pipe 합계 Fig. 3. Comparison of friction losses between steel pipe and CPVC pipe Table 8. Breakdown cost table of CPVC Pipe Names of goods Standard Unit Amount unit cost Material cost Labor costs Total cost sum unit cost sum unit cost sum Pipe, Φ50mm m 34 9, , , ,500 Pipe, Φ40mm m 1 6,300 6, ,300 6,300 Pipe, Φ32mm m 4 4,550 18, ,550 18,200 Pipe, Φ25mm m 3 3,900 11, ,900 11,700 CPVC Tee, Φ50mm m 11 5,600 61, ,600 61,600 Tee, Φ40mm m 1 3,453 3, ,453 3,453 Tee, Φ32mm m 3 2,600 7, ,600 7,800 Tee, Φ25mm m 13 1,800 23, ,800 23,400 Elbow, Φ50mm m 6 4,500 27, ,500 27,000 Elbow, Φ32mm m 2 2,300 4, ,300 4,600 Elbow, Φ25mm m 13 1,200 15, ,200 15,600 Pipe component 5% for pipe ,557 25, ,557 25,557 Miscellaneous cost Normal 3% for main material cost general ,334 15, ,334 15,334 person ,882 99,882 99,882 99,882 Plumber general person , , , ,854 Hand cost 3% for labor ,062 11, ,062 11,062 Total 563, , ,

SPP(white pipe), Φ40mm SPP(white pipe), Φ32mm SPP(white pipe), Φ25mm white Tee, Φ50mm, white Tee, Φ40mm, white Tee, Φ32mm white Tee, Φ25mm white elbow, Φ50mm white elbow, Φ32mm white elbow, Φ25mm

7 스프링클러시스템에서조도계수에따른 CPVC 배관마찰손실영향의연구 Table 9. Breakdown cost table of Steel Pipe Names of goods Standard Unit Amount Carbon Steel pipe for pipelines Screw steel pipe connection iron Pipe lagging (atiron, super magic 303) SPP(white pipe), Φ50mm SPP(white pipe), Φ40mm SPP(white pipe), Φ32mm SPP(white pipe), Φ25mm white Tee, Φ50mm, white Tee, Φ40mm, white Tee, Φ32mm white Tee, Φ25mm white elbow, Φ50mm white elbow, Φ32mm white elbow, Φ25mm unit cost Material cost Labor costs Total cost sum unit cost sum unit cost sum m 34 7, , , ,800 m 1 5,074 5, ,074 5,074 m 4 4,417 17, ,417 17,668 m 3 3,440 10, ,440 10,320 ea 11 5,100 56, ,100 56,100 ea 1 4,000 4, ,000 4,000 ea 3 3,100 9, ,100 9,300 ea 13 2,500 32, ,500 32,500 ea 6 4,000 24, ,000 24,000 ea 2 2,200 4, ,200 4,400 ea 13 1,800 23, ,800 23,400 25TxD50 m 34 3, ,400 6, ,344 9, ,744 25TxD40 m 1 2,700 2,700 5,285 5,285 7,985 7,985 25TxD32 m 4 2,555 10,220 4,573 18,292 7,128 28,512 25TxD25 m 3 2,298 6,894 3,879 11,637 6,177 18,531 Pipe component 5% for pipe ,893 13, ,893 13,893 Miscellaneous cost Normal Plumber 3% for main material cost general general - 1 8,335 8, ,335 8,335 person , ,764 99, ,764 person , , , ,708 Hand cost 3% for labor ,124 22, ,124 22,124 Total 601, ,030 1,585,158 Fig. 4. Construction case of steel pipe Fig. 5. Construction case of CPVC pipe 361

8 한국산학기술학회논문지제 17 권제 11 호, 2016 Table 10. Comparison of cost between Steel pipe and CPVC pipe Type 84 Division Material cost (the amount per household: won) labor costs (the amount per household: won) Sum (the amount per household: won) Steel pipe 601, ,030 1,585,158 CPVC 563, , , 결론본연구에서는소방배관의마찰손실을개선하기위하여기존강관대신 CPVC배관으로설계및시공하였을경우, 조도계수에따라손실수두의차이가있음을조사였다. 조도계수의수치가강관 (120) 일때마찰손실은 76.64MPa이고 CPVC배관 (150) 으로적용할때마찰손실은 50.72MPa로서결론적으로 34% 정도의마찰손실이개선되었음을확인하였다. 또한, 시공비절감차원에서는강관으로시공할때 1,585,158원이고 CPVC배관으로시공시에는 931,842원으로 41% 정도의시공비가절감되는것을확인하였다. 기존에는일반적으로높은압력에서는강관을사용하였으나, 화재안전기준의개정에따라소화설비저압축의습식소화설비에는지하에매설하는경우나내화구조로구획된덕트또는피트의내부에설치하는경우, 천정과반자를불연재료또는준불연재료로설치하고그내부에습식으로배관을설치하는경우에는소방용합성수지배관인 CPVC배관으로설치할수있으므로마찰손실을줄여소화펌프및입상배관의관경을줄일수있어, 전체설비용량의감소로인한소화시스템의안정성유지및시공비를절감할수있는것을알수있었다. system, [6] D. J. Kim A study on corrosion of sprinkler systems in fire protection, pp , Master s thesis, [7] NFSC 103 National Fire Safety Code for Sprinkler system, [8] GOLEE Pipe Co Article for CPVC Pipe Available from: (2014) 강웅일 (Kang Ung Il) [ 정회원 ] 1991 년 2 월 : 전남대학교공과대학화학공학과 ( 공학사 ) 1993 년 2 월 : 전남대학교대학원화학공학과 ( 공학석사 ) 2001 년 2 월 : 전남대학교대학원화학공학과 ( 공학박사 ) 2014 년 2 월 ~ 현재 : 셀텍 ( 벤처기업 ) 대표 2015 년 3 월 ~ 현재 : 호남대학교소방행정학과교수 < 관심분야 > 신재생에너지, 재난안전, 고분자합성 References [1] S. J. Lee, A study on Hydraulic Analysis method for Optimizing VE Design of CPVC Pipe pp Master s thesis, [2] KSFPE, Fire Protection Engineering Handbook Version 4, pp , [3] NFPA 13 ASTM F 442 (2010 edition) [4] E. M. Seong, I. S. Eo A study on improvement stragies of friction loss according to roughness coefficient in sprinkler system pp Master s thesis, [5] NFSC 103 National Fire Safety Code for Sprinkler 362

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The Korean Journal of Applied Statistics (2014) 27(1), 13 20 DOI: http://dx.doi.org/10.5351/kjas.2014.27.1.013 Maximum Tolerated Dose Estimation by Stopping Rule and SM3 Design in a Phase I Clinical Trial