Designing a Machine Foundation for a 10.89 MW Diesel Generator
Machine Design I
Submitted to: Engr. Rosello Lyndon H. Roble, PME
Submitted by: Rickle Vincent B. Pilongo Mil-rey Enriquez
September 2010
Designing a Machine Foundation for a 10.89 MW Diesel Generator Generator Specifications: Nameplate MAN B&W Engine Type 18V40/45 Provenance Germany Rated Power 10.89MW Suitable Fuel 180CST/50C Already Run Hours 40,000h Number of cylinder 18 Rated Speed 600 Cylinder bore/Piston 400/450 Fuel Consumption 200+5% G/KW.H (Under ISO Condition, Lev=42700kj/kg Engine Dimensions( mm) 10,150×4,750×3,300(mm) Engine Weight 128,000Kg Solution: 1. Weight of the Machine Foundation, WF WF = e × We × √N Where: WF
= weight of machine foundation, kg
We
= weight of the engine, kg
e
= empirical coefficient, [Table 2.4, 2.3(4) PSME Code]
N
= engine speed, rpm
Given: We = 132 tons;
N = 600 rpm;
e = 0.11
Substituting, WF = 0.11 × 128 × √600 WF = 344 888 kg
2. Volume of the Machine Foundation, V F VF = WF / 2406 density of concrete, ρ = 2406 kg/m³ substituting, VF = 344 888 / 2406 VF = 143. 345 m³
3. Lower width of the machine foundation, b b = N (WF + We) / Sb × L where: Safe Soil Bearing Capacity = 78 – 98 tons/m² N, factor of safety, usually = 2 WF = 344.888 tons We = 128 tons Safe Soil Bearing Capacity = 78 – 98 tons/m² clearance, c = 0.3 m machine bedplate length, L = engine length + 2c = [10.15 + 2(0.3)] L = 10.75 m substituting, b = 2 × (344.888 + 128) / 88 × 10.75 b = 1.0 m finding: a = bedplate width of machine, m a = w + 2c a = 4.75 + 2(0.3) a = 5.35 m since, b
4. Depth of machine foundation, h h = 2 VF / ( a + b ) × L h = 2 × 143.55 / (5.35 + 5.35) × 10.75 h = 2.496 ≈ 2.5 m
5. Quantity of sand and gravel in 143. 345 m³ concrete foundation with 1 : 2 : 4 concrete mixture: given: Material
Relative Density
Density (kg/m³)
Cement Sand
3.10
1428 2.64
Gravel
1680 2.50
1525
Using: 26 liters of water per bag of cement; assuming one bag of cement as 0.028 m³ per bag of cement, loose volume Let: Vc, Vs, Vg, Vw = compact volume of cement, sand, gravel and water respectively Then, Vc = 1428 (0.028) (1) / 3.10 (1000) = 0.0129 m³ / batch Vs = 1680 (0.028) (2) / 2.64 (1000) = 0.0356 m³ / batch Vg = 1525 (0.028) (4) / 2.50 (1000) = 0.0683 m³ / batch Vw = 26 / 1000
= 0.0260 m³ / batch Vtotal = 0.1428 m³ / batch
Total no. of batches
=
143.345 / 0.1428
= 1003.82 batches
Volume of Sand required = 1003.82 (0.028) (2) Vs = 56.214 m³ Volume of Gravel required = 1003.82 (0.028) (4) Vg = 112.428 m³ Volume of Cement required = 1003.82 (0.028) Vc = 28.1 bags Volume of Water required = 28.1 × 26 Vw = 730.8 liters
6. Steel Bar reinforcements requirement (to avoid cracking): Weight of steel bars (½% - 1% total weight) = ¾ % Using ½ in. steel bars with a weight of
= 0.668 lb/ft
Therefore, Weight of steel bar = (0.0075) (344 888) WSB = 2586.66 kg. = 5702.6 lb Length of steel bar = 5702.6 (0.668) LSB = 3809.34 ft.
Recommendations 1. Foundation should be isolated from floor slabs or building footings by at least 25 mm around its perimeter to eliminate transmission of vibration.
2. The machine should not be placed on the foundation until seven (7) days have elapsed and operated until seven (7) days have passed 3. Anchor Bolts should be imbedded in the concrete at least 30 times the bolt diameter.
4. Foundation bolts specified size should be used and surrounded by a pipe sleeve with an inside diameter of at least 3 times the diameter of the anchor bolt and a length 18 times the diameter of the bolt. No foundations shall be less than 18 mm diameter. 5. Machine should be leveled by driving wedges between the machines base and concrete foundation and with the aid of a spirit level. Grout all spaces under the machine bed with a thin mixture of one part cement and one part sand. The level wedges should be removed after the grout thoroughly set and fill wedges holes with grout.
Reference: •
Prime Review Center Mechanical Engineering Reference Manual: Machine Foundations
