sspds200401

Stainless SteelPlumbing and Drainage Solutions

Stainless Steel Pipes and Tubes for Water SupplyPublication No. SSPDS-2004-01

Issue No. : 01Date : 22 August 2004

This publication has been prepared by the Stainless Steel Plumbing and Drainage Solutions.

Although all care has been taken to ensure that the information contained herein is accurate and up-to-date, the contributors assumeno responsibilities on any error or misinterpretations of such data and/or information or any loss or damages arising from or relatedto their use.

Technical enquiries related to this publication should be directed to :-

Stainless Steel Plumbing and Drainage SolutionsUnit 11, 8/F., Kam Hon Industrial Building8 Wang Kwun RoadKowloon Bay, KowloonHong Kong

Tel. : 852-2757 9369Fax : 852-2757 9483

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Copyright © 2004 Stainless Steel Plumbing and Drainage Solutions

All Rights Reserved

P.1 of 10 Publication No. : SSPDS-2004-01


Introduction

The use of stainless steel pipes and tubes for water supply has been gaining acceptance in recent years,mainly because of the fall of lead and galvanized steel pipes, and the fact that the prices of stainless steelpipes and tubes have been in the downward trend due to larger demand.

Benefits of the use of stainless steel pipes and fittings include :-

– Good corrosion resistance for full range of potable water– High strength to weight ratio– Stainless steel is unaffected by high water flow rate– Low maintenance cost and life-cycle cost– Stainless steel is non-toxic– It is 100% recyclable– It has good appearance without any coating– It is not affected by sunlight, and can be used in tropical areas where the ambient temperature may be

above 40oC without derating.

Common types

The most widely used stainless steels used for water supply is the austenitic type 304 and 316. Compositionof these stainless steels are listed in Table 1. Although efforts have been made to harmonize the name of thedifferent stainless steels, different countries still use different names. The different designations for 304 nd316 stainless steels are listed in Table 2.

CommonName

UNS No. Nominal Composition (%)

C (Max.) Cr Ni Mo Fe

304 S30400 0.08 18.0-20.0 8.0-12.0 - Bal

304L S30403 0.03 18.0-20.0 8.0-12.0 - Bal

316 S31600 0.08 16.0-18.0 10.0-14.0 2.0-3.0 Bal

316L S31603 0.03 16.0-18.0 10.0-14.0 2.0-3.0 Bal

Table 1 – Composition of commonly used stainless steel for pipes and tubes for plumbing applications

CommonName

UNS No. EURONORMEN10088

British BS German DIN Swedish SS Chinese GB Japanese JIS

304 S30400 1.4301 304S31 1.4301 2333 0Cr18Ni9 SUS304

304L S30403 1.4306 304S11 1.4306 2352 00Cr19Ni10 SUS304L

316 S31600 1.4401 316S31 1.4401 2347 0Cr17Ni12Mo2 SUS316

316L S31603 1.4404 316S11 1.4404 2348 00Cr17Ni14Mo2 SUS316L

Table 2 – Designation of commonly used stainless steel for pipes and tubes for plumbing applications



Properties ValueSpecific Garvity 8.0

Average coefficient of thermal expansion (10-6/oC) (0-100oC) 16

Thermal conductivity (W/moC) (100oC) 15

Specific heat (1/kgoC) (0-100oC) 500

Electrical resistivity (ohm mm2/m) Room temperature 0.72

Young's Modulus (kN/mm2) 200

Magnetism NO

Table 3 – Typical physical properties of stainless steel

How to Choose

The choice between 304 and 316 stainless steels is mainly the degree of corrosion resistance. For watersupply applications, the major considerations are the residual chlorine level, which is the result ofdisinfection of water, and the chloride level, which indicates the amount of salt in the water. Table 3 lists therecommended choice according to the design chloride and residual chlorine level.

Application Chloride Level(ppm) Residual Chlorine Level(ppm) Recommended TypeCold Water <200 <2 304/304L

Cold Water <1000 <5 316/316L

Hot Water <50 <2 304/304L

Hot Water <250 <5 316/316L

Table 4 – Recommended choice of stainless steel pipes and tubes against chloride and chlorine level

Type 304L and 316L are the low carbon versions of 304 and 316. The use of these lower carbon versionsensures that the heat of welding will not sensitize the heat affected zone of the weld to intergranularcorrosion. Sensitization is used to describe the reduction in corrosion resistance that occurs in theconventional (.08 max C) grade stainless steel because of the precipitation of carbides during welding in theheat affected zone adjacent to welds.

Joints

Different jointing methods have been developed for stainless steel pipe and tubes, including :-

– flange joint– threaded joint – welded joint– capillary joint– compression joint– push-in joint– press joint



The most cost-effective jointing method for distribution pipework is the press joint, which utilizes thedeformation of the tubes and the fittings to ensure watertight, secure connections. The joints made arepermanent and are tamper-proof. An elastomer o-ring is inserted in the joint for water sealing. A typicalpress joint is shown in Fig. 1. Common fittings for press joints are shown in Fig. 2. The basic steps ofmaking a press joint is shown in Fig. 5.

For normal water supply applications, EPDM or NBR o-ring are used.

Fig. 1 - The Press Joint Fig. 2 - Press Joint Fittings

Tubes of different specifications are used for the press joint. The most commonly used tubes are listed inTable 5 and Table 6. Table 5 is for tubes to the German standard DVGW W541 which is used throughoutEurope. Table 6 is for tubes to ASTM269, JIS G3448 and KS D3595 which are common in their respectivecountries. As can be seen, these tubes are of thin wall construction and are more cost-effective than pipes forother jointing methods such as threading or flanging.

Designation Outside Diameter (mm) Wall Thickness (mm) Approx. Weight (g/m)

15 18 1 426

20 22 1.2 625

25 28 1.2 805

32 35 1.5 1258

40 42 1.5 1521

50 54 1.5 1972

65 76.1 2 3711

80 88.9 2 4352

100 108 2 5308

Table 5 - Dimension for tubes to DVGW W541, ISO1127, DIN EN 10312 and GB/T19228.2-2003 Series I



Designation Outside Diameter (mm) Wall Thickness (mm) Approx. Weight (g/m)

15 15.88 0.8 303

20 22.22 1 532

25 28.58 1 691

30 34.0 1.2 986

40 42.7 1.2 1250

50 48.6 1.2 1430

60 60.5 1.5 2210

75 76.3 1.5 2810

80 89.1 2 4370

100 114.3 2 5630

Table 6 - Dimension for tubes to JIS G3448, ASTM A269, KS D3595 and GB/T19228.2-2003 Series II

Fig. 3 - A press tool (fromMUPRO North America, Inc.)

The press joint is made with a tool for the compressing the joint. Thetool can be hydraulic, electric or manual.

An electric tool is shown in Fig. 3. Care should be taken to ensureadequate space is available for inserting the press tool. Manufacturer'srecommendations should be consulted.

The tool can be used for different pipe sizes by changing the tongs.

After making the joint, measure the shape of the joint with calibrationtool from the manufacturer to ensure proper joint.

Advantages of press joints

• Flame free installation • Economic, simple and quick • Reliable • Design life of 50 years • Secure permanent joint • Corrosion resistant • Slimeline and unobstructive • Maintains electrical continuity • Tamper resistant

Disadvantages of press joints

• Relies on use of press tool • Press tool need calibration • Cannot be demounted • Cannot be reused

Table 7 - Advantages and Disadvantages of the Press Joints



Fig. 5 – Basic steps of making press joint



Fig. 5 - Pressed joint used for water supply Fig. 6 - Welded stainless steel 304 pipes used forraw water pumping

Capillary fittings are available and they are joint using solder. The use of chloride-based flux is strictlyprohibited as this can cause serious pitting problem. Tubes to BS4127 are suitable for use with capillaryfittings. The major drawback of capillary fitting is that heating of the pipes and fittings is required and thetime of connection is longer than compression or press fittings.

Compression fittings are available. Common standards are BS4368:Part3 and DIN2353. Tubes used withBS4368:Part3 compression fittings are BS4127. The major disadvantage of the compression fitting is thehigh cost of the fittings. The use of compression fitting is also restricted to small size tubes. Coppercompression fittings can be used.

Push-in type fittings are available up to about 50mm diameters. The joint is sealed using elastomer o-ringand a plastic collar provides gripping strength. Tubes to BS4127 or DVGW W541 can be used. Specialsurface treatment has to be applied to the tubes.

Other jointing methods including welding, flanging and threading are commonly used for jointing of pipesof larger sizes, or where the application requires higher pressure ratings.

Commonly used pipes for flanging, threading and welding are listed in Table 8. These pipes are of differingwall thickness for different pressure ratings. For pipes of other specifications, please refer to themanufacturer's data. Other common pipe dimensions are ISO5252, BS3605, GB2270-80 and SSG1361.

During processing of stainless steel pipes for flanging (welding of flanges), welding and threading, ensurethat the tools are free from contaminations of other metal particles as these may cause surface rusting of thestainless steel and subsequent corrosion. Crevice features and all weld heat tints should be removed afterwelding for optimum corrosion resistance.



For flange joint, ensure that the gasket is compatible to avoid crevice corrosion and galvanic corrosion.Gaskets containing graphite or chlorides should not be used with stainless steel flanges.

NominalDiameter

(mm)

OutsideDiameter

(mm)

Designation

SCH-5S SCH-10S SCH-40S

Wallthickness

(mm)

Weight (kg/m)

304/304L 316/316L

Wallthickness

(mm)

Weight (kg/m)

304/304L 316/316L

Wallthickness

(mm)

Weight (kg/m)

304/304L 316/316L

8 13.72 - - - 1.65 0.50 0.50 2.24 0.64 0.64

10 17.15 - - - 1.65 0.64 0.64 2.31 0.85 0.86

15 21.34 1.65 0.81 0.81 2.11 1.01 1.02 2.77 1.28 1.29

20 26.67 1.65 1.03 1.03 2.11 1.29 1.30 2.87 1.70 1.71

25 33.40 1.65 1.31 1.31 2.77 2.11 2.13 3.38 2.53 2.54

32 42.16 1.65 1.67 1.68 2.77 2.72 2.74 3.56 3.42 3.45

40 48.26 1.65 1.92 1.93 2.77 3.14 3.16 3.68 4.09 4.11

50 60.33 1.65 2.41 2.43 2.77 3.97 4.00 3.91 5.50 5.53

65 73.03 2.11 3.73 3.75 3.05 5.32 5.35 5.16 8.72 8.78

80 88.90 2.11 4.56 4.59 3.05 6.52 6.56 5.49 11.4 11.5

90 101.60 2.11 5.23 5.26 3.05 7.49 7.54 5.74 13.7 13.8

100 114.30 2.11 5.90 5.93 3.05 8.45 8.51 6.02 16.2 16.3

125 141.30 2.77 9.56 9.62 3.40 11.7 11.8 6.55 22.0 22.1

150 168.28 2.77 11.4 11.5 3.40 14.0 14.1 7.11 28.5 28.7

200 219.08 2.77 14.9 15.0 3.76 20.2 20.3 8.18 43.0 43.2

250 273.05 3.40 22.8 23.0 4.19 28.1 28.2 9.27 60.9 61.3

300 323.85 3.96 31.6 31.8 4.57 36.3 36.6 9.52 74.5 75.0

350 355.60 3.96 34.7 34.9 4.78 41.8 42.0 - - -

400 406.40 4.19 42.0 42.3 4.78 47.8 48.1 - - -

450 457.20 4.19 47.3 47.6 4.78 53.9 54.2 - - -

500 508.00 4.78 59.9 60.3 5.54 69.3 69.8 - - -

550 558.80 4.78 66.0 66.4 5.54 76.4 76.8 - - -

600 609.60 5.54 83.4 83.9 6.35 95.4 96.0 - - -

750 762.00 6.35 119.5 120.3 7.92 148.8 149.7 - - -

Table 8 - Dimensions for pipes to ASTM A312 A358 A778 B36.19



Cost Comparison

According to the Steel Construction Institute's publication IGN-4-25-02 : Applications of Stainless Steel inthe Water Industry, cost saving can be achieved by using stainless steel pipes by the elimination of corrosionallowance and protection coating and the simplification of jointing and assembly. A comparison was madewith carbon steel and ductile iron for fabrication of a 6-metres runs for DN150, DN200, DN250 and DN300pipes, based on price in 1998, and the saving on installed costs of stainless steel pipes can be from 36% to78%. This had not taken into account the space saving of stainless steel pipes.

Operating costs for stainless steel piping are also expected to be lower because of the following :-

- smoother surfaces of stainless steel resulting in lower friction loss- reduced maintenance cost due to easier cleaning. No protective coating is required- reduced downtime and cost for inspection- longer service life

Residual value of stainless steel pipes and tubes are high as they are not subject to corrosion in normal useand are 100% recyclable. Life cycle costs, comprising the installed costs, the operating costs and deductingthe residual values, all adjusted to present values, are often used for cost comparison and stainless steelpiping systems always show cost advantages over carbon steel and ductile iron systems.

The British Stainless Steel Association had compared costs for stainless steel and copper tubes and fittings.Copper was found to be much cheaper in the smaller diameter (15mm to 22mm) pipes and fittings. The gapin price between copper and stainless steel decreased in the middle range of diameters (28mm and 35mm).The price of stainless steel nearly equalled, or was sometimes lower than copper, in the largest diameters(42mm to 108mm).

Stainless steel pipes can also withstand muchhigher flow rates without noticeable corrosion.Fig. 7 shows the rate of corrosion of stainlesssteel and copper against water flow rates. As canbe seen, the effect of water flow on copper ismuch higher than for stainless steel at high flow.

The ANSI/NSF standard confirms that stainlesssteels are highly resistant to leaching of anyspecies that might contaminate potable water.Stainless steel does not require a corrosionallowance as is needed for ductile cast iron andcarbon steel and thereby permits the selection ofminimum thickness solely based on structuralstrength and pressure requirements.

Fig. 7 - Velocity corrosion of stainless steel andcopper



References

1. Applications of Stainless Steel in the Water Industry, 1999The Steel Construction Institute

2. The Suitability and Use of Stainless Steel for Plumbing Applications, 2003British Stainless Steel Association

3. Stainless Steel in Water Handling and Delivery Systems, 1996Specialty Steel Industry of North America


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