| Standard | Equipment / System | Applies To | Primary Use / Scope | Edition / Status | Notes |
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API 682 — Seal Arrangements & Annex G Piping Plans
API 682 is the reference for shaft sealing systems on centrifugal and rotary pumps in petroleum, natural gas, and chemical service. Below is a quick reference for the three seal arrangements and the standardized seal flush / barrier / buffer piping plans defined in Annex G of the standard.
Seal Arrangements
Arrangement 1
One seal per cartridge. Single mechanical seal sealing the process fluid directly to atmosphere.
Arrangement 2
Two seals per cartridge with a liquid or gas buffer fluid at a pressure lower than seal-chamber pressure. Used for low-leakage and emission control.
Arrangement 3
Two seals per cartridge with a liquid or gas barrier fluid at a pressure higher than seal-chamber pressure. Used for hazardous, toxic, flammable services and zero process emissions.
Annex G — Standard Seal Piping Plans
All standardized plans defined in API 682 4th Edition, Annex G:
Notes & Companion Standards
- Mechanical seals (centrifugal & rotary pumps): API 682. Dry gas seals (axial / centrifugal / rotary screw compressors and expanders): API 692.
- Gear units: API 613 (special-purpose, helical) for refinery duty trains; API 677 (general-purpose, extruder, epicyclic) for less critical drives.
- Couplings: API 671 covers gear, metallic flexible-element, quill-shaft and torsionally resilient couplings used on special-purpose machines.
- Lubrication / control oil: API 614 covers lube, oil-type shaft seal and control-oil systems; excludes dry gas seal supply systems and fuel systems.
- Pumps overview: API 610 (centrifugal), API 674 (PD reciprocating), API 675 (PD controlled-volume), API 676 (PD rotary), API 685 (sealless centrifugal), API 681 (liquid-ring vacuum / compressor).
- Compressors overview: API 617 (axial & centrifugal incl. expander-compressors), API 618 (reciprocating), API 619 (rotary screw), API 672 (packaged integrally geared air), API 673 (centrifugal fans), API 681 (liquid ring).
- Vibration / monitoring: API 670 for purchase specification of protection systems (vibration, axial position, bearing temperature). ISO 20816-3 for in-situ vibration evaluation on coupled industrial machines >15 kW, 120–30,000 r/min.
- Pulsation & vibration on PD machinery: API 688 for reciprocating compressors and PD pumps.
- Rotordynamics & balance tutorial: API TR 684-1 — companion technical report on the API standard paragraphs covering rotor dynamics and balance, with an introduction to lateral critical speed and train torsional analysis.
- Installation & repair: API RP 686 (installation / pre-commissioning); API RP 687 (special-purpose rotating equipment repairs).
- Risk-based machinery management: API RP 691 for HSE risk management across the machinery lifecycle for high-risk equipment.
- Electrical machines: NEMA MG 1 (motors & generators) and IEEE C50.13 (50/60 Hz cylindrical-rotor synchronous generators driven by steam & gas turbines, ≥10 MVA).