Selecting the right industrial engine is a crucial process that demands a thorough analysis of usage conditions. This guide offers a structured approach to determining the appropriate rating tier level and selecting a suitable engine model for your engine application. By carefully evaluating the duty cycle—including load conditions, speed variations, and operational patterns—engineers can ensure the engine meets the specific demands of the application.

The rating calculation is based on key factors such as load and speed, which together determine the rating factor. This factor helps identify the correct tier level, ensuring the selected engine is well-matched to real-world operating conditions for optimal performance and efficiency.

The step-by-step methodology outlined below provides a clear framework for this calculation.

Step 1: Calculating Load Factor

Load factor, which represents the average demand on an engine, can be estimated using actual fuel consumption. It is calculated by dividing the fuel used during a work cycle by the maximum possible fuel consumption at the engine's rated capacity over the same period. This provides a practical measure of engine workload, helping to determine suitability for specific applications.

Duty Cycle Analysis

A thorough duty cycle analysis provides a more accurate calculation of load factor. It examines the time an engine operates at various powers and speeds, breaking it down into detailed segments—such as rated power, percentage loads, idle states, and different speed ranges. These values are crucial in calculating both load and speed factors (see below), ensuring an accurate assessment of engine performance and suitability for the application.

Example of a Simple Duty Cycle

*All idle (low & high) power is assumed as 10% of rated power
** Low idle speed is usually 25 - 40% of rated speed
*** High idle speed is usually 110% of rated speed

Load Factor Calculation

Load Factor = Total of % Power x % Time
1.00 x .50 = .50
.80 x .10 = .08
.50 x .20 = .10
.10 x .10 = .01
.10 x .10 = .01
TOTAL = .70 or 70% Load Factor

Step 2: Calculating Speed Factor

Speed Factor Calculation
Speed Factor = (Total of % Speed x % Time)²
1.00 x .50 = .500
.85 x .10 = .085
.75 x .20 = .150
.40 x .10 = .040
1.10 x .10 = .110
TOTAL =(.885)² = .78 or 78% Speed Factor

Step 3: Calculating Rating Factor

Multiplying the load factor and the speed factor together results in a rating factor. This rating factor helps determine the proper rating tier for this duty cycle.
Load Factor x Speed Factor = Rating Factor
Calculation: .70 x .78 = .546 or .55
Result: A .55 Rating Factor, which equates to a Tier C Rating with reference to the Tier Rating Factor Chart below.

Selecting the right industrial engine requires analysing duty cycles, load conditions, and speed variations. By calculating the rating factor, engineers can determine the appropriate engine tier level for optimal engine performance.

Our step-by-step methodology simplifies the process, ensuring the best engine choice.

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