Relief Valve: Reactive Force

This calculation determines the force at the point of discharge of a pressure relieving device. API 520 indicates that the equation is for elbow and vertical exhaust pipe.

where

𝐹 − Reactive force at the point of discharge to the atmosphere(lbf)

𝑊 − Flow of gas(lbm/hr)

𝑀 − Molecular Weight of Gas

𝐴 = Area of outlet at the point of discharge(in²)

𝑇 − Temperature at outlet(°R)

𝑘 − Specific Heat Ratio (𝐶_𝑃/𝐶_𝑣) at the outlet conditions

P − Static pressure within the outlet at the pint of discharge(psig)

Input Parameters

1. To create a new case, click the “Add Case” button
2. Select the Relief Valve Reactive Force application from the Pipeline Facilities section.
3. Enter Case Name, Location, Date and any necessary notes.
4. Fill out all required fields.
5. Make sure the values you are inputting are in the correct units.
6. Click the CALCULATE button.

• Relief Valve Set Pressure (psig)
• Gas or Vapor Flowing Temperature (F)
• Back Pressure (psig)
• Required Flow through Valve (MSCFH)
• Kd – Effective Coefficient of Discharge
• Kb – Capacity Correction Factor
• Compressibility Factor of Gas or Vapor
• Molecular Weight of Gas or Vapor
• Specific Heat Ratio

Outputs/Reports

1. View the results.
2. If an input parameter needs to be edited be sure to hit the CALCULATE button after the change.
3. To SAVE, fill out all required case details then click the SAVE button.
4. To rename an existing file, click the SAVE As button. Provide all case info then click SAVE.
5. To generate a REPORT, click the REPORT button.
6. The user may export the Case/Report by clicking the Export to Excel/PowerPoint icon.
7. To delete a case, click the DELETE icon near the top of the widget.

• t – Required Wall Thickness of the Header
• (H – t) – Excess Thickness in the Header Wall
• tb – Required Wall Thickness of the Branch
• (B – tb) – Excess Thickness in the Branch Wall
• AR – Reinforcement Required
• A1 – Reinforcement Provided
• L – Height
• A2 – Effective Area in Branch/Outlet
• A2 – Corrected Effective Area
• A3 – REQUIRED AREA
• AP – PROVIDED AREA
• Reinforcement of Welded Branch Connection is:

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