Starting Systems
Waukesha gas engines
Air Volume and Pressure Guidelines
for VHP* GL Engines with TDI Air Starters
Engine Cranking Torque at 125 Engine rpm
MODEL
TORQUE
(LB-FT)
P9390GL
880
L7042GL
700
L5790GL
650
F3521GL
540
F2895GL
510
Based on 70°F ambient and use of SAE 30 lube oil. For 50°F
ambient, multiply by 1.2. For SAE 40 lube oil, multiply by
1.15. Includes engine friction and accelerating torques.
TABLE 2.
Standard TDI 112V Air Starter Torque
Capability and Consumption at 125 Engine
rpm
AIR
PRESSURE
AT
STARTER
(psig)
AIR
GAS
AIR
GAS
70
1040
1473
75
98
80
1300
1733
84
109
90
1560
1993
93
121
100
1773
2247
102
133
110
1987
2502
111
144
120
2200
2756
120
156
130
2420
3037
129
168
140
2640
3319
139
180
150
2860
3600
148
192
NOTES:
1.
2.
3.
4.
5.
TORQUE
(LB-FT)
TYPICAL AIR/GAS
CONSUMPTION PER
START – SCF
TABLE 3.
Optional TDI 121V Air Starter Torque
Capability and Consumption at 125 Engine
rpm
AIR
PRESSURE
AT
STARTER
(psig)
AIR
GAS
AIR
GAS
40
884
936
85
111
50
1222
1612
101
131
60
1560
2288
116
151
70
1901
2750
131
170
80
2241
3212
146
190
90
2582
3674
161
209
TYPICAL AIR/GAS
CONSUMPTION PER
START – SCF
TORQUE
(LB-FT)
Curve 1 – Accelerating Torque for Driven Equipment
500
400
TORQUE LB-FT
TABLE 1.
300
200
100
0
0
100
200
300
400
500
600
WR2 OF DRIVEN EQUIPMENT lb-in2 x 1000
Assumed cranking time of 6 seconds for gas engines.
Recommend use of jacket water and lube oil heaters below 50°F ambient to hold a minimum of 70°F in engines. When
not used, increase air consumption 5% for each 10°F air intake temperature below 50°F.
If an air motor driven pre-lube pump is used, add approximately 20 ft3 per start for 6 and 12 cyl. engines and
approximately 35 ft3 per start for 16 cyl. engines.
Natural gas consumption is ~130% of air; Natural gas torque is ~110% of air.
Maximum pressure rating of the standard TDI 112V starter is 150 psig. Maximum pressure rating of the optional TDI 121V
starter is 90 psig.
Page 1 of 2
Air Volume and Pressure Guidelines for
VHP GSI and LT Engines with TDI Air Starters
EN: 141939
DATE: 7/08
Ref.
S
7447-9
Starting Systems
Waukesha gas engines
Instructions / Example:
To find the minimum required air pressure at the starter (PSIG), add the engine cranking torque from Table 1 and the accelerating
torque for the driven equipment from Curve 1 to the friction torque of the driven equipment. From Table 2 select the minimum air
pressure. Do not interpolate between pressures. Use the next higher pressure.
To find the air consumption per start (SCF), use the minimum air pressure at the starter (PSIG) from above and refer to Table 3.
Error! Bookmark not defined. Min.Sizeof AirReceiver,FT3
=
(Req'd number of starts)x (SCFofair per start) x (Atmos,press.,PSIA)
(Max.air receiverpress.,PSIG)- (Min.usable air receiverPress.,PSIG)
Example:
Given Information
•
P9390GL Engine with UG8 Governor
•
50°F Ambient
•
SAE 40 Lube oil being used
•
Driven equipment is a generator
•
Generator WR2 = 460,000 LB-IN2
•
Generator friction torque = Negligible
•
Air Receiver Pressure max = 150 PSIG
•
Piping Pressure Loss = 10 PSIG
•
No. of Starts Required = 4
•
Atmospheric Pressure = 14.7 PSIA
•
Air driven TDI 112V starter
•
Air driven pre-lube pump
Solution
•
Engine cranking torque, LB-FT = 880 x 1.2 x 1.15 = 1214 (Table 1)
•
Generator accelerating torque, LB-FT = 300 (Curve 1)
•
Generator friction torque, LB-FT ~ 0 (Given)
•
Total cranking torque, LB-FT = 1214 + 300 + 0 = 1514
•
Minimum air pressure at starter, PSIG = 90 (Table 2 – Note use of next higher pressure)
•
Typical air consumption per start, SCF = 93 (Table 2)
•
Minimum usable air receiver pressure equals minimum air pressure at starter plus piping pressure loss, PSIG=90+10=100.
•
Air motor driven pre-lube pump air consumption, SCF = 35 (per start – note 3)
THEN: Minimum air receiver size
FT3
=
4x(93+ 35)x14.7 =
(150− 100)
4x128x14.7
50
Error! Bookmark not defined. FT3
FT3
=
7526.4
50
= 150.5
Use a 150 FT3 air receiver or closest combination of sizes at a minimum.
If the high pressure compressor and receiver are not optimal for the customer, he may choose to use the optional TDI 121V starter
in Table 3. In that case the minimum air pressure at the starter is 60 PSIG and air consumption per start is 116 SCF. Using a 150
psig receiver regulated to 90 PSIG would result in the following receiver size:
FT3
=
4x(116+ 35)x14.7
= 111 Error! Bookmark not defined.
(150− (60+ 10))
This smaller, lower pressure receiver and compressor may be more suitable to the customer for this application.
NOTES:
If adverse starting conditions will be commonly encountered, increase the size of the air receiver by 25%.
Recharge of the air receive between starts is neglected.
*Trademark of INNIO. All other trademarks are the property of their respective owners.
Page 2 of 2
Air Volume and Pressure Guidelines for
VHP GSI and LT Engines with TDI Air Starters
EN: 141939
DATE: 7/08
Ref.
S
7447-9