Calculations

This topic has been intentionally excluded from the APM product documentation website. This topic is available to you via the product documentation that is provided within the APM system.

This topic has been intentionally excluded from the APM product documentation website. This topic is available to you via the product documentation that is provided within the APM system.

This topic has been intentionally excluded from the APM product documentation website. This topic is available to you via the product documentation that is provided within the APM system.

The inventory component mass of a component is calculated using the values in the following fields in the Criticality Calculator RBI Component record:

• Operating Pressure (P)
• Operating Temperature (T)
• Diameter (d)
• Length (L)
  Note: If the component type is Piping, then the value in the Piping Length field is used instead of the value in the Length field.
• Percent Liquid Volume (pc)
• Molwt (This value is stored in the RepresentativeFluids reference table for the fluid specified in the Process Fluid field in the Criticality Calculator RBI Components record)
• Fluid Density (This value is specified in the RepresentativeFluids reference table for the fluid specified in the Process Fluid field in the Criticality Calculator RBI Components record)

The inventory component mass of a component is calculated as follows:

Inventory Component Mass = (Liquid Volume x Fluid Density) + (Vapor Volume x Vapor Density)

Where:

• Liquid Volume = (pc/100) x Volume of the cylinder
  Note: The volume of the cylinder is calculated from the values in the Diameter and Length fields in the Criticality Calculator RBI Component record.
• Vapor Volume = (1-(pc/100)) x Volume of the cylinder
• Vapor Density = (Molwt x (P + 14.7)) / (10.73 x (T + 459.15) x z)

This value is populated in the Inventory Component Mass field in the Common section of the associated RBI 581 Consequence Evaluation.

Example for Calculating Inventory Component Mass

Suppose a component has the following specifications:

• Component Type: Heat Exchanger (Shell)

• Process Fluid : C6-C8

• Operating Pressure: 101 Pounds/Sq Inch Gage

• Operating Temperature: 121 Degrees Fahrenheit

• Molwt of CO: 28

• Diameter: 97.625 inches

• Length: 360 inches

• Percent Liquid Volume: 50 percent

• Fluid Density: 42.704

Given these values:

• Volume of the cylinder = (pi x (d/12) x (d/12) x (L/12)) / 4

  Volume of the cylinder = ((22/7) x (97.625/12) x (97.625/12) x (360/12)) / 4

  Volume of the cylinder = 1560.075 Cubic feet

• Liquid volume = (pc/100) x Volume of the cylinder

  Liquid volume = (50/100) x 1560.075

  Liquid volume = 780.038 Cubic feet

• Vapor volume = (1 - (pc/100)) x volume of the cylinder

  Vapor volume = (1 - (50/100)) x 1560.075

  Vapor volume = 780.038  Cubic feet

• Vapor Density = (Molwt x (P + 14.7)) / (10.73 x (T + 459.15) x z)

  Vapor Density = (100 x (101 + 14.7)) / (10.73 x (121 + 459.15) x 1)

  Vapor Density = 1.859 Pounds per cubic feet

• Inventory Component Mass = (Liquid Volume x Fluid Density) + (Vapor Volume x Vapor Density)

  Inventory Component Mass = (780.038 x 42.704) + (780.038 x 1.859)

  Inventory Component Mass = 34760.526 Pounds

  Note: The value in the Inventory Component Mass field on the RBI Component datasheet may slightly differ from the value that is shown in the example. This happens because of rounding off some of the values.

The inventory group mass is calculated as the sum of the inventory component mass values of all the individual components in an inventory group. This value is populated in the Inventory Group Mass field in the Common section in the associated RBI 581 Consequence Evaluation record. If the component is not linked to an inventory group, then the value in the Inventory Group Mass field is the same as the value in the Inventory Component Mass field.

For example, suppose you have created an inventory group, Group 1, and linked it to three components, Component 1, Component 2, and Component 3. The inventory component mass values for each of these components are shown in parentheses.

In this case, the inventory group mass is calculated as follows:

Inventory Group Mass of Group 1 = Inventory Component Mass of Component 1 + Inventory Component Mass of Component 2 + inventory Component Mass of Component 3

Inventory Group Mass of Group 1 = 120 + 100 + 130

Inventory Group Mass of Group 1 = 350 Pounds

Suppose you have created an RBI 581 Risk Analysis, Analysis 1, for Component 1. APM then calculates the inventory component mass of Component 1 based on the input values in Analysis 1. In the following diagram, this value is shown in parentheses next to Analysis1.

In this case, the inventory group mass is calculated as follows:

Inventory Group Mass of Group 1 = Inventory Component Mass calculated based on input values from Analysis 1 + Inventory Component Mass of Component 2 + Inventory Component Mass of Component 3

Inventory Group Mass of Group 1 = 150 + 100 + 130

Inventory Group Mass of Group 1 = 380 Pounds