API 682 và ISO 21049 cho vành chèn cơ khí (Đệm kín cơ) (mechanical seal)

Overview
• Overview of API 682 and ISO 21049
• Designed to introduce the user to some of the significant features of the standard
• Module 1 of a four part series
• Each Module has an accompanying text which can bee seen by viewing the Notes Page (View/Notes Page from the Menu bar)

Module 1 Topics
• Review of API 682 First Edition
• Mission Statement
• API 682 Second Edition
• ISO 21049 and API 682 Third Edition
• Scope of Standard
• Key Concepts
• Seal Types
• Seal Arrangements
• Categories

Mission Statement “This standard is designed to default to the equipment types most commonly supplied that have a high probability of meeting the objective of a least three years of uninterrupted service while complying with emissions regulations.”

Seal Types

• Over the years, seal companies have released numerous designs and variations

• No standardization in seal designs, materials, or dimensions

• Challenge for API 682 Task Force was to create standard seal types defining seal design, materials, installation envelope, and operating windows

• Rotating flexible element, multiple springs, O-ring secondaries

• Silicon Carbide versus premium grade blister resistant Carbon

• Fluoroelastomer O-rings (FKM)

• Alloy C276 springs (316 for single spring option)

• Type 316 SS sleeve, gland, and other metal parts

• Throttle bushing in gland

• Rotating bellows, O-ring secondaries

• Silicon Carbide versus premium grade blister resistant Carbon

• Fluoroelastomer O-rings (FKM)

• Alloy C-276 bellows

• Type 316 SS sleeve, gland, and other metal parts

• Throttle bushing in gland

• Stationary bellows, flexible graphite secondaries

• Silicon Carbide versus premium grade blister resistant Carbon

• Alloy 718 bellows

• Type 316 SS sleeve, gland, and other metal parts

• Premium carbon floating bushing in gland

• Bronze anti-coke device

Rotating vs Stationary

• The default Type A and Type B seals have a rotating flexible element

• A stationary flexible element is an alternate

• The default Type C seal has a stationary flexible element

• A rotating flexible element is an alternate

• If surface speed at the faces exceeds 4500ft/min (23 m/s), a stationary flexible element must be used

Seal Arrangements

• The seal arrangement defines the

number or seals, their orientation, and

details about the seal’s operation

• Designations

• Contacting wet (CW)

• Containment seals (CS)

• Non-contacting dry-running

• Contacting dry-running

• Non-contacting (NC)

• Wet running seals

• Dry-running dual seals

Contacting Wet Seal - CW
• “Typical” mechanical seal
• Mechanical seal designed to run on liquid fluid film
• Does not intentionally create hydrodynamic forces
• Requires vapor suppression to keep fluid in a liquid phase
• Designed to run for a minimum of 25,000 hours

Containment Seal - CS
• Designed as a dry running backup seal
• Outer seal in a dual non-pressurized arrangement
• May be either a non-contacting or contacting design
• Operates on buffer gas or vaporized process fluid
• Run for 25,000 hours at 10 PSI and at least 8 hours under process conditions

Non-Contacting Seal - NC

• May be used as a primary seal or as a dual pressurized seal

• Seal is designed to create hydrodynamic forces to separate the faces under all operating conditions

• Designed to run for a minimum of 25,000 hours