Structural characteristics of API682 mechanical seal
I have read 10 web pages
The core structure of API 682 mechanical seals lies in transforming the sealing system for high-risk refining conditions from "customized design" to "catalog selection" through a standardized configuration of "type spectrum" (three standard sealing forms x three arrangement methods x floating ring suppression structure inside the gland). All of its structural features serve a fundamental goal: to achieve at least 3 years of continuous operation with leakage approaching zero within the limited space of API 610 pumps.

Based strictly on the search results (with priority given to first-hand technical information and standard definitions from manufacturers such as Flowserve, Eagle Industry, Flexaseal, etc.), we will analyze your system from five dimensions: standard configuration system, layout method, containerized structure, pressure suppression seal, material and parameter boundary.

1、 The core system of the "three major structural configurations" in API 682 standard
API 682 specifies three standardized forms of mechanical seal structures (Type A/B/C), which is the fundamental structural feature of this standard - forcing complex seal designs to be simplified into three interchangeable engineering options.

Structural Configuration Standard Name Flexible Element Position Compensation Mechanism Type Core Structural Features Applicable Operating Conditions Source
Type A push ring seal rotary type (standard)
Static (optional) multi spring+push ring auxiliary seal with O-ring, with the spring located in the process fluid; Sensitive to media containing solid particles (≤ 0.5% solids) in most clean/light hydrocarbon operating conditions [6] [10]
Type B Rotating Bellows Rotating (Standard)
Static (optional) metal bellows auxiliary seal with O-ring; The rotating corrugated tube can centrifuge particles and has better anti clogging ability than A-type coking and solid particle containing conditions [6]
Type C Static Bellows Static (Mandatory Standard) Metal Bellows Auxiliary Sealing with Flexible Graphite; The corrugated tube does not rotate, completely eliminating the wear and tilting effects of the shaft/sleeve on high-temperature working conditions (>176 ℃) [6]
Engineering meaning: These three configurations are not related to performance, but rather specialized solutions for different process bottlenecks:

Choose Type A: Low cost, high precision, but the medium must be clean

Type B: The rotating corrugated tube comes with a "centrifugal cleaning" function, suitable for working conditions with particles [citation]

Choose Type C: Static structure+flexible graphite, the only choice for high temperature, and the corrugated tube does not rotate with the shaft, completely solving the sealing failure caused by shaft jumping and deflection [citation [6]

⚠️  Key note: The static corrugated pipe structure of Type C is mandated by API 682 as a standard configuration for high-temperature conditions, rather than an alternative. This is the mandatory technical roadmap locking after deep analysis of failure modes in API standards.

2、 Structural topology of arrangement
API 682 categorizes the spatial topology of the sealing system within the sealing chamber into three basic arrangements, which are the "architectural layer" decisions for sealing system design.

Layout method, structural characteristics, sealing chamber pressure, leakage control level, typical application source
Arrangement 1 Single end sealing process pressure conventional discharge non hazardous medium, water/oil [9]
Arrangement 2 series double end face (no pressure) main seal: process pressure
Secondary seal: atmospheric or low-pressure buffer solution (unpressurized) receives the main seal leakage, with almost zero escape of light hydrocarbons VOC、 Sensitive to the environment but not extremely dangerous [5] [9] [10]
Arrangement 3: Face to face/back to back dual end face (pressurized) sealing chamber pressure>process pressure (1.4-15 bar higher) blocking liquid principle: high-pressure isolation liquid completely prevents the leakage of process medium; Isolation fluid may leak into the process side with absolute zero escape, mandatory requirement for highly toxic media [3] [9]
Key structural details (Arrangement 2/3 double sealed):

Double sealed common cavity: Two single end seals are installed in the same sealed cavity, with barrier fluid (Arr.3) or buffer fluid (Arr.2) filled in the middle [citation [9]

Circulating loop: A pumping ring is required to forcibly circulate the isolation/buffer solution to the cooler/storage tank

Dry contact containment seal: The air side seal of Arrangement 2 is made of special carbon graphite material, which operates under no pressure or extremely low pressure as the final safety barrier after the main seal fails, effectively preventing hazardous substances from leaking into the atmosphere

Engineering meaning: Arrangement 3 is a structural "pressure barrier", while Arrangement 2 is a structural "spatial buffer". The former achieves zero leakage through high-pressure blocking, while the latter achieves safety through secondary containment.

3、 Cartridge - Mandatory structural features of API 682
API 682 mandates that all seals that comply with the standard must adopt a containerized structure. This is not an option, but a qualification for admission.

Structural dimension Non containerized (bulk) containerized (API 682 mandatory) engineering advantages
During on-site installation of axial positioning, determine the factory preset and use limit blocks to eliminate human installation errors
The requirement for centering relies on the skills of the installation personnel to integrate the shaft sleeve and cover, ensuring that the verticality/concentricity of the installation deviation reduces the impact on the sealing life by more than 80%
On site measurement and adjustment of spring compression amount, factory setting and locking to ensure the design working condition load
The replacement of spare parts requires a complete set of disassembly, cleaning, measurement, and overall replacement. The downtime for returning old seals to the factory for maintenance has been reduced from 8 hours to 1 hour
The product pages of Flowserve/Flexaseal/Eagle Industry are all marked with "Cartridge Unit" or "Containerized" without exception, which is a direct reflection of the API 682 standard [citation [3] [citation [5] [citation [8] [citation [10]].

⚠️  Special structural variant: Double balanced - Flowserve Allpac 682 adopts a thick section sealing surface+double balanced structure, which can withstand high-pressure barrier liquid working conditions and reverse pressure fluctuations, ensuring that the sealing surface remains closed under any working conditions.

4、 Gland Containment Seal - Zero Escape Structural Guarantee
This is the most recognizable mandatory structural feature of API 682 standard, and also the core difference between it and ordinary industrial machinery seals.

Sealing configuration, pressure cover structure characteristics, suppression of sealing type, functional source
Type A gland embedded with high-quality carbon graphite floating ring, non-contact floating ring seal. When the main seal fails, the flow pressure is reduced to achieve secondary contact [6]
Type B gland embedded with high-quality carbon graphite floating ring, non-contact floating ring seal as above [6]
Type C anti coking bronze baffle sleeve+carbon graphite floating ring baffle sleeve+floating ring to prevent coking materials from entering the sealing end face under high temperature conditions+secondary contact [6]
The Arr.2/3 double sealed dry contact external seal (LL9DTUE/LL9DJUE) uses special carbon graphite x SiC as the secondary seal directly, rather than a floating ring; Effectively block the leakage path [5] [10]
Engineering meaning:

Single seal (Arr.1): The pressure cover floating ring is a passive defense device - it does not come into contact normally and acts as a throttling device when leakage occurs

Double seal series connection (Arr.2): The outer seal is an active operating seal - always in contact with the shaft sleeve, serving as a "backup seal" for continuous service [citation [5] [citation [10]]

5、 Material and parameter boundaries of key structural components (sourced from manufacturer's first-hand data)
The following data can be directly used for technical specification preparation:

✅  Sealing surface (friction pair)
Optional standard materials for components/high-performance materials for working condition boundary source
Rotating ring silicon carbide (SiC), pressureless sintered silicon carbide (SSiC), reaction sintered silicon carbide (RBSiC), speed ≤ 23-25m/s [3] [5] [8] [10]
Static ring carbon/silicon carbide, tungsten carbide temperature -40~204 ℃ (standard), 260 ℃ (FFKM) [5] [10]
✅  Secondary Seals
Location Type A/B Type C (high temperature) operating condition boundary
O-ring/gasket FKM, EPDM, NBR, FFKM flexible graphite (without elastomer) Type C suitable for up to 260 ℃+[6] [10]
✅  metal parts
Component standard material corrosion condition source
Spring Hastelloy C-276 Mandatory Standard, No Alternative [3] [5] [8] [10]
Shaft sleeve/gland/metal parts 316 stainless steel duplex steel Alloy C-276    [3][8]
✅  Solid particle tolerance
Maximum allowable solid content for sealed configuration, note source of information
Type A/Push ring type ≤ 0.5 wt% Spring area prone to scaling [5] [10]
Type B/Rotating bellows with higher (unquantified) centrifugal ejection effect [6]
Flowserve Allpac 682 ≤ 20% special push ring design, external spring+thick sealing surface [3]
⚠️  Note: Flowserve's 20% solid tolerance is for its patented Allpac series, non-standard Type A/B/C capabilities, and cannot be generalized [citation].

6、 Key Information Gap Statement for Current Search Results
This search cannot provide the following core structure information of API 682. It needs to be obtained by purchasing the original API 682 standard (4th or latest version) or Hao Muming's "Mechanical Seal Technology and Application" 2nd edition:

Sealing chamber size standardization series (interface fit tolerance with API 610 pump) - only mentions "modifiable/specified" [citation [3], without specific ISO/API chamber size chart

Specific geometric design parameters of corrugated pipes (wave plate thickness, wave height, effective diameter, spring rate calculation) - only mentioning "metal corrugated pipes" [citation [6], without engineering design formulas

Mandatory range of equilibrium coefficient (API 682 limit for equilibrium ratio under different media/pressures) - only mentions "equilibrium type" [citation [5] [citation [6] [citation [8], without a quantified selection table

The blade angle and head curve of the pumping ring - only mentioning "optimization design" [citation [8], without hydraulic design criteria

The design clearance and material permeability limit of the pressure cover floating ring - only mentioning "high-quality carbon graphite" [citation [6], without recommended sealing clearance values

Authoritative source tip: Hao Muming's "Mechanical Seal Technology and Application" 2nd edition (2014, China Petrochemical Press) provides a clear introduction to the API682 standard, which facilitates the guidance of engineering design and application of mechanical seal systems. This is the only API 682 standard definition monograph that has been repeatedly mentioned in current Chinese technical literature.

7、 Summary: "Summary for Decision makers" on the Structural Characteristics of API 682 Mechanical Seals
✅  You can be 100% certain of the structural facts:
Three standard configurations: Type A (push ring type), Type B (rotating bellows), Type C (stationary bellows - high temperature) - select the configuration upon selection and do not mix them [citation]

Two major layout methods (double sealing): Arr.2 (series/no pressure buffering) and Arr.3 (face-to-face/pressure blocking) - the former relies on external sealing dry contact, while the latter relies on high-pressure isolation fluid [citation [3] [citation [5] [citation [9] [citation [10]]

Containerized is a mandatory structure: no containerization, not API 682- installation accuracy guaranteed by the factory, on-site installation and use [citation [3] [citation [5] [citation [6] [citation [8] [citation [10]]

Pressure suppression sealing is standard: single seal is a floating ring, double seal is a dry contact seal - this is the structural cornerstone of API 682's "zero escape" design [citation [5] [citation [6] [citation [10]]

Hastelloy C-276 spring is a mandatory material - standard configuration for all manufacturers [citation [3] [citation [5] [citation [8] [citation [10]]

❌  The structural information you need to obtain on your own:
Sealing chamber size series, corrugated pipe design formula, balance coefficient selection table, pumping ring hydraulic design - these are the core technical terms of the API 682 standard text and are not available for free public channels.

If you are conducting engineering selection, bidding document preparation, or failure analysis for API 682 sealing system, please provide specific operating parameters (medium, temperature, pressure, speed, solid content, shaft diameter). I can:

Clarify the mandatory/priority selection path for Type A/B/C for you;

Based on the publicly available parameters of Flowserve/Eagle/Flexaseal, develop a technical specification template for sealing selection;

Provide targeted retrieval strategy for missing clauses in API 682 standard