Stainless Steel Bus Bodies : Cost Less & Last Long

Indian Stainless Steel Development Association

(ISSDA)

• Not for profit organization.

• Technical and market development arm of the stainless steel industry in India.

• Aim is to educate engineers, architects and material specifiers in the end use sectors and diversify the applications of stainless steel.

Indian Stainless Steel Development Association

(ISSDA) • Organises workshops, seminars and conferences.

• Technical information service.

• ISSDA is networked with all stainless steel development associations of the world

• Newsletters, Brochures.

• www.stainlessindia.org

How stainless steel works

Steel Stainless

Steel

Passive Film

Steel

Steel +

> 10-12% Chromium

Carbon

Steel

Rust

The corrosion resistance of stainless steel comes from the chromium-rich passive layer

STAINLESS STEEL: Cr-Oxide Layer

Passive Film

Stainless Steel Surface Damage Self Repairing

SELF REPAIRING SURFACE

India vis-à-vis World

Source of info : INSAPTRANS handbook

Fig: Per capita penetration : Buses per 1000 person

1940s

1980’s

Early 1990s

2000s

2012

Advantage of Stainless Steel

7

• High paybacks

• Fuel efficiency

• Lesser corrosion

• Lesser wear of floor

• Lower tare wt

• High Strength to wt ratio

• Higher payload

• High axle load

• Crash Resistance

• Fire resistance

• Low Maintenance cost

• Ease of cleaning

• Ease of repair

• No painting required

• Aesthetics Lower

maintenance Safety

Lower life cycle cost / Longer life

Design

Train crash in Australia at 80 kmph. Stainless steel saves lives !

Crush Behavior of stainless steel circular hollow section maximizes energy absorption in the event of a collision (Euro Inox 2006a)

Bus accidents 42,600 (in 2009)

Causalities Approx 13,000 people

Injuries 58,000

Source: Report on “Road accidents in India 2009”, Ministry

of road transport and highways

In the case of fire, the structural integrity of a stainless steel body remains intact much longer than that of carbon steel body and longer still that of an aluminium body. Low thermal conductivity of stainless steel tends to retard the spread of heat damage to structural components. No paint, No hazard

Variation of Young’s Modulus with Temperature for

Stainless Steel and Carbon steel

Source of info : ISSDA/NiDi architectural

workshop April 2001

SS

View of Stainless steel framework underneath bus. Approximately 10 years old

Severe corrosion of a mild steel bus structure

Technically, stainless steel is superior to mild steel

SS

vs.

MS

• Strength+Ductility

• SS with higher strength and comparable ductility is a better option

• Fully recyclable

• Fatigue strength of SS is better than MS

• Function of Cr content

• SS with high Cr content is much better than MS

Toughness Corrosion

resistance

Green

Material Fatigue resistance

Global References / Case Studies

Greyhound: United Kingdom

In 1968, Greyhound introduced its improved MCI-7 model using stainless steel in the chassis with stainless steel skins to address the rust problem.

Greyhound: United Kingdom

The model MCI 8 came next from 1973 to 1978. 4,475 units were built and it was squarer and more modern looking than the MCI-7 with more stainless steel in the sub chassis.

Greyhound: United Kingdom

Fig: MCI-9, a high mileage low maintenance intercity long haul over-the-road coach

Between 1979 to 1987 came the now famous MCI-9 model and it’s still being manufactured (as the MCI 12). The most successful Passenger Bus ever made, with over 9,000 have been produced. This coach's sub-frame and the rear section around the engine is 90% Stainless Steel.

Case Study: Volvo, Finland Since 1991, Volvo (Finland) is fabricating bus coaches for its 9700 model in

Stainless Steel for its two and three-axle coaches.

Coach Length: 10.4 -15 metres in length.

Both underframe and body are stainless steel, to ensure a long life.

Fig: A three-axle Volvo 9700 in at the IAA exhibition in Hannover in 2006 (Geoff Stephenson)

“This body construction is chosen to give the

customer the advantages of a corrosion-resistant

framework. Bus which is made of stainless

steel retains an attractive appearance for the whole

of its life, reduces maintenance and service costs and

ensures a high second-hand value.” – Volvo (Finland)

Case Study: Volvo, Finland

European bus manufacturers started using stainless steel in the early 1990s.

Development started specifically in Scandinavia, where a cold and humid climate, often

involving the use of de-icing salts, explains operators’ willingness to consider a corrosion-resistant material such as stainless steel.

According to 2008 data, 80% of the buses in Europe are in stainless Steel.

The buses are lighter with improved crash worthiness of the passenger compartment, require less maintenance, and are more fuel-efficient.

Europe: SS in Bus Body

Figure: Articulated bus with a skin in

ferritic stainless Steel (Van Hool 2007).

ASSDA initiative – Bus Tech Pvt. Ltd for Volvo, Australia

SS body shell 700 kg

reduction in tare wt.

15% reduction in production

time

Life period up to 15 years

• 200 m of square hollow sections

• 600 kg of SS sheet

• Finish : 2B

Australia’s first stainless steel buses were

manufactured by Bus Tech Pty. Ltd.

These buses were made for Volvo, Australia.

The interior & exterior panel along with the

tubular structure was made in stainless steel

• Savings of $2 per km in petrol cost

• Can Carry additional passengers

Case Study: Volvo, Australia

Case Study: Silver Eagle, USA

Silver Eagle Bus offers buses in a stainless steel chassis & stainless steel skins

It utilizes Stainless Steel panels for designing the bus bodies.

The features also include Stainless Steel Chassis Up to Floor Line Standard.

Recent developments in SS bus body frame show tremendous potential

Autokinetics, Inc.

(Ultra light stainless steel urban bus concept)

Goals

• Mass reduction

• Minimise cost

• purchase

• operation

•life cycle

• Improved performance,

usability & comfort

Methods

• Nitronic 30 grade SS

• UTS – 827 Mpa

• High elongation %

• High fatigue strength

• Forming process

• contour roll forming

• Joining process – spot

welding

Results

• Mass reduction

• 64% redn wrt conventional bus

• lower curb wt – 42% increase in payload within legal axle limits

• Cost reduction

• cost of Nitronic 30 less than 304

• Higher yield for roll forming process

• low tooling investment

Case study :

SS Success Story: Railway Coaches

Courtesy: RCF, Kapurthala

Courtesy: RCF, Kapurthala

SS Success Story: Railway Coaches

SS Success Story: Metro

Bus Body: Indian Initiatives

Indian Initiatives

Footsteps in SS cheq sheets

SS Bus Panel

Developments at Shillibear, Kerala

Floors in SS cheq sheets

Indian Initiatives Developments at Shillibear, Kerala

Floors in SS cheq sheets

Case Study: TNSTC-Coimbatore

TNSTC-Coimbatore introduced many stainless steel body city buses in its

Coimbatore, Erode and Tirupur regions.

SS body city buses have been launched with the name “City Express”.

Where Stainless Steel can be used

Tubular Structure

Properties required for Structural

High Strength to weight ratio – Lighter coach

Toughness – Formability & Crash resistance

Corrosion resistance – Longer Life

Fatigue resistance - Longer Life

In case of fire – Structural Integrity

No Paint – Passenger safety, Environment friendly

Structural members: Current Material

Carbon Steel : IS 4923 of 1997,

Grade: YST 210

Square Tubes (popular sizes)

Rectangular Tubes (popular sizes)

Properties Value

25 X 25 60 X 40 YS 210 MPa min

40 X 40 75 X 50 UTS 330 MPa min

50 X 50 20 X 50 Elongation 20% min

25 X 50

Source of info : Discussions with Ashok Leyland / Swaraj Mazda/Shillibear

Tubular Structure

YST 210

• Typical Y.S : 210 Mpa

Stainless Steel

• Typical Y.S : 280-320 Mpa

Weight reduction with SS is ~ 20%

Panels

SS stretch panel

SS skirt panel

Properties required for Panels

Resistance to corrosion

Resistance to vibration (drumming resistance)

Function of Panel Stiffness

Stiffness is ability of material to resist bending

Stiffness = Young’s Modulus

Aesthetic Value

Crash worthiness: SS bears very high impact resistance that makes it a safer material in case of accidents.

Panels: Current Material

Consumption in 12 m long bus: approx. 300 to 400 kg

Young’s Modulus: 74 GPa

Panel Thickness Length Width

Side Panel – Top 2.5/3.0 mm 20 m 850 mm

Side Panel – Bottom 2.5/3.0 mm 20 m 1200 mm

Source of info : Ashok Leyland / Swaraj Mazda / JCBL

AL Alloy

Panels: Stainless Steel

Stainless steel

Young’s Modulus

: 205 GPa

Based on Young’s Modulus comparison,

– 1.00 – 1.5 mm thick SS grades can be used

Footsteps & Flooring

Floorings: Current Material

Current Material: Al cheq plate

Thickness: 3.0 – 3.5 mm

Stainless Steel : 0.8 to 1 mm

SS chequered plates

Advantages

Yield Strength : High - 515 MPa Hardness : High – Vickers 275 Wear & Tear behaviour : Low due to high rigidity and hardness Fixing method : Assembly with screws, rivets and welding Weldability : Good Cleanability : Easy Expected life : High Relief : Double side (as compared to mild steel’s single side relief) Corrosion resistance : High

SS chequered plate

Applications: Floorings Foot steps Entrance Luggage Carrier

Other Applications

Roof Panels in SS

Other Applications

Back Support Frame

Seat Underframe

Hand Rails and Hand Holds

Fasteners

Guarding of Step wells

Other Applications

Life cycle cost Comparison

LCC

LCC = Acquisition cost+ Fabrication & installation cost+ Maint.cost (Periodic) + Replacement costs (Periodic) + Cost of downtime (periodic) + Residual (scrap) value

6

Cost (

Rs)

Time in years

8 4 0

1,64,000

2,80,000

3,28,000

2.2

Cost of the entire bus is

recovered.

MS Body Initial Cost

SS Body Initial Cost

Ove

rha

ul

Rebuilding

Fuel saving on SS body

Up to 15 yrs

The Taj Mahal would not have been so beautiful if Shah Jehan had asked for quotations and gone for the lowest.

Thank You

Cost

S.No Description UT Qty Rate AmountProposed

thicknessQty Amount Difference Landed cost of SS sheet

1 ALU.SHEET 3.00 MM KG 18.05 146.86 2650.823 1.0 MM 17.12 1712.15 938.67 Sheet price (basic, ex-Hisar) 86000 Rs/MT

2 ALU.SHEET 2.00 MM KG 50.80 146.86 7460.488 1.0 MM 72.65 7265.09 195.40 Add : Excise+cess @ 10.3% 8858 Rs/MT

3 ALU.SHEET 1.6 MM KG 53.88 146.86 7912.8168 1 MM 96.31 9631.08 -1718.26 Sub-total 94858 Rs/MT

Total 122.73 18024.128 186.08 18608.32 -584.19 Add : CST @ 2% 1897 Rs/MT

Sub-total 96755 Rs/MT

4 MSL 25x25x3 MM KG 24.25 36.00 872.856 2MM 16.16 1616.40 -743.54 Add : freight 3000 Rs/MT

5 MSL 40X40X3 MM KG 139.27 36.50 5083.428 2MM 92.85 9284.80 -4201.37 Total landed at A.P. 99755 Rs/MT

6 MSL 40X40X6 MM KG 225.24 35.00 7883.4 4MM 150.16 15016.00 -7132.60

7 MSL 50X50X6 mm KG 26.42 35.00 924.7 4MM 17.61 1761.33 -836.63 Landed cost of SS tubes

8 SAIL 100x50 CHANEL KG 318.03 36.00 11449.152 4MM 212.02 21202.13 -9752.98 Tube price (basic, ex-Gurgaon) 102000 Rs/MT

9 SAIL -75X40X6 CHANNEL KG114.23

36.00 4112.1 4MM 76.15 7615.00 -3502.90 Add : Excise + cess @ 10.3% 10506 Rs/MT

10 GI SHEET 0.91 MM KG 499.22 48.00 23962.416 0.80MM 443.75 44374.84 -20412.43 Sub-total 112506 Rs/MT

11 G.I.SHEET 0.91 MM SKINPASS KG 110.09 49.00 5394.557 0.80MM 97.86 9786.04 -4391.49 Add : CST @ 2% 2250 Rs/MT

12 MS PLATE 6MM KG 79.40 40.00 3176.04 4MM 52.93 5293.40 -2117.36 Sub-total 114756 Rs/MT

13 MS SHEET 0.91MM KG 43.93 45.00 1976.805 0.80MM 39.05 3904.80 -1928.00 Add : Freight 3000 Rs/MT

14 MS SHEET 1.22 MM KG 47.73 45.00 2147.67 0.80MM 31.30 3129.57 -981.90 Total landed at AP 117756 Rs/MT

15 MS SHEET 1.6 MM KG 46.39 45.00 2087.64 1MM 29.00 2899.50 -811.86

16 MS SHEET 2 MM KG 331.78 45.00 14930.1 1.6 MM 265.42 26542.40 -11612.30

17 MS SHEET 3.15 MM KG 111.61 42.00 4687.62 2.5 MM 88.58 8857.94 -4170.32

18 ERW PIPE 25X2 O/D KG 38.50 42.38 1631.52 1.6 MM 30.80 3634.40 -2002.88

19 M.S.SQ.TU.25X25X2 KG 14.10 56.06 790.38 1.6 MM 11.28 1331.04 -540.66

20 M.S RECT.TU.40X20X2 KG 195.00 56.32 10983 1.6 MM 156.00 18408.00 -7425.00

21 M.S RECT.TU.40X30X2 KG 33.87 56.93 1928.36 1.6 MM 27.10 3197.33 -1268.97

22 M.S.SQ.TU.40X40X2 KG 288.57 58.24 16806 1.6 MM 230.86 27241.01 -10435.01

23 M.S.REC.TU. 60X40X2 KG 411.75 54.46 22422.18 1.6 MM 329.40 38869.20 -16447.02

24 MS ROD 6 mm DIA KG 0.48 35.96 17.2608 0.48 17.26 0.00

25 MS ROD 8MM SIDE KG 2.31 36.00 83.052 2.31 83.05 0.00

26 MS ROD 16MM SIDE KG 1.57 36.00 56.628 1.57 56.63 0.00

27 MS ROD 25 MM SIDE KG 0.91 36.00 32.76 0.91 32.76 0.00

28 MS FLAT 25X3 mm KG 9.40 36.00 338.472 9.40 940.20 -601.73

29 MS FLAT 25X6MM KG 7.52 36.00 270.54 7.52 751.50 -480.96

30 MS FLAT 40X6 MM KG 41.49 36.00 1493.568 4 MM 27.66 2765.87 -1272.30

31 MS FLAT 50X6 MM KG 2.27 36.00 81.864 4 MM 1.52 151.60 -69.74

32 Total 3288.05 163648.2 2635.72 277372.32 -113724.13

33 DIFF KG 652.33

Additional cost towards SS material 113724

Additional cost towards forming & cutting SS material 10000

Less cost of hotphosphating & epoxy primer of mild steel -11334

Total 112390

Weight reduction with SS 652.33 kg 20%Savings on fuel : 2litres per 100 km of travel per 1000 kg wt redn.

ie fuel savings per km of travel per 1000 kg wt reduction 0.8 (considering diesel price as Rs 40/litre)

For the net wt reduction, fuel savings per km travel 0.52 Rs/km

Minimum distance traversed by bus per annum 100000 km/year

Thus, total fuel savings per annum 52186.68176 Rs/annum

Thus, the incremental cost of Rs 1,12,000 with SS can be recovered 2.2 years

Life of MS bus is 4 years, after which the entire body is changed.

Life of SS bus would be minimum 8-10 years.

Total cost of MS bus

a. Material cost with MS 163648.1966 Rs/bus

b. Cost of hot phosphating & epoxy primer 11334 Rs/bus

Thus, total RM+Hot phosphating cost of MS bus 174982 Rs/bus

Thus, total cost of MS bus over a period of 8 years 349964.3932 Rs/bus

Total cost of SS bus over 8 years 123724 Rs/bus

Thus, cost benefit with SS bus over MS bus 226240 Rs/bus

Fuel savings of SS bus over 8 years 417493.4541 Rs/bus

Thus, net savings with SS bus (I62+I63) 643734 Rs/bus

MILD STEEL STAINLESS STEEL 1.4003

Fabrication of Super Luxury Bus Body with Stainless Steel Grade-1.4003 Material - Costing Analysis