Design of Relief and Vent Openings for Storage Tanks and Pressure Vessels

In Design of Relief and Vent Openings for Storage Tanks and Pressure Vessels, you'll learn ...

• The engineering principles and regulatory considerations governing relief and vent openings for storage tanks and pressure vessels.
• How to differentiate among common venting and pressure-relief devices and identify appropriate applications and installation considerations for each.
• How to apply fluid-flow principles to determine the required size and configuration of relief and vent openings and connections.
• How to evaluate storage-tank and pressure-vessel relief and vent connection designs using applicable operating conditions, equipment requirements, codes, standards, and accepted engineering practices.

Overview

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Credit: 3 PDH

Length: 45 pages

This course details the engineering principles associated with the openings for reliefs and vents used to protect storage tanks and pressure vessels from overpressurization or vacuum conditions. It distinguishes between vents, which handle compressible fluids like gases, and relief openings, which can discharge both liquids and vapors. The material emphasizes the vessel designer’s responsibility to ensure that vessel openings are compatible with protective devices while minimizing nonrecoverable pressure losses. The content is rich with graphics and provides practical example problems with step-by-step worked solutions.

Much has been written about vessel overpressure and under-pressure protection. The literature primarily focuses on identifying the sources (causes) of these conditions and estimating the mass or volumetric fluid flowrates associated with such events. Having knowledge of these two aspects enables the selection of appropriate devices or design of systems to prevent over- and under-pressurization of vessels. However, one important aspect often receives less attention: design of the vessel opening that facilitates the protective device or system. This course intends to address this shortcoming. To be clear at the outset, the purpose is not to concentrate on all of the potential sources that can cause damaging pressure excursions nor to determine the minimum required relieving fluid flowrates.

Key fluid dynamics concepts, such as Reynolds numbers, friction factors, and the Darcy-Weisbach formula, are provided to calculate flow behavior and pressure drops. Furthermore, the course outlines specific industry standards—including API, AWWA, and OSHA—that dictate the placement of safety apparatus like rupture discs and pressure-vacuum valves. Examples illustrate how to size openings for different roof types and service conditions to maintain structural integrity and safety. The course is intended for mechanical, chemical, and petroleum engineers who possess an elementary understanding of fluid mechanics. A cursory knowledge of pressurized process equipment is recommended but is not required to study this course.

Specific Knowledge or Skill Obtained

This course teaches the following specific knowledge and skills:

• Reclosing and non-closing pressure protection devices
• How to distinguish storage tanks from unfired pressure vessels based on operating pressure, geometry, service conditions, and applicable design considerations.
• The concept of compressible and incompressible fluids
• How to differentiate relief openings, vent openings, drains, and overflows according to their function and the characteristics of the fluid being conveyed.
• Major codes, standards, and regulatory requirements applicable to storage-tank venting and pressure-vessel relief systems.
• The effects of tank roof configuration, vapor space, liquid transfer, temperature changes, and gas blanketing on normal pressure and vacuum venting requirements.
• How to apply conservation of mass, Bernoulli relationships, compressible-flow equations, Reynolds number, friction factors, and minor-loss coefficients when evaluating relief and vent flow.
• How to calculate pressure losses and flow capacity through vent openings, nozzles, piping components, and pressure-relief-device inlet connections and the importance of non-recoverable pressure loss
• How to determine appropriate opening and connection sizes using required relieving capacity, fluid properties, operating pressure, allowable pressure loss, and connection geometry.
• How to select and evaluate nozzle, pipe, and flange configurations for compatibility with pressure-relief and vent devices and applicable design requirements.
• How to evaluate the location and orientation of relief and vent connections to reduce fouling, blockage, liquid accumulation, excessive inlet losses, and other conditions that could impair protective-device performance.
• Roles of the process engineer and the vessel designer
• Vessel and tank nozzle fabrication methods

Certificate of Completion

You will be able to immediately print a certificate of completion after passing a multiple-choice quiz consisting of 20 questions. PDH credits are not awarded until the course is completed and quiz is passed.