Vapor control system

1. VAPORVAPOR
CONTROLCONTROL
SYSTEMSYSTEM

2. Vapor Control BackgroundVapor Control Background
 During tank vessel loading, ballasting, and
lightering, organic vapors contained in cargo tanks
are displaced by cargoes or liquids introduced into
Cargo Oil Tanks. Most cargo vapors are volatile
organic compounds (VOC) which attribute to the
formation of SMOG that may damage public health
and the environment.
 The Clean Air Act was passed in 1990 and it defined
provisions to control the emissions of VOC and
other air pollutants from tank vessel loading and
unloading operations.

3. U.S. Coast GuardU.S. Coast Guard
VCS RegulationsVCS Regulations
Marine Facilities
– 33 CFR 154
Vessels
– 46 CFR 39

4. Vapor Control SystemVapor Control System
PurposePurpose
Control vapors of crude oil, gasoline
blends, or benzene emitted from a tank
vessel’s cargo tanks, at the time of loading.

5. Typical Marine Vapor Control SystemTypical Marine Vapor Control System
Consists of the following:
– Tank Vessel Vapor Collection System
– Arrangement of piping and hoses on vessel and
facility
– Facility Vapor Processing Unit (Recover or
Destroy Vapors)

6. Vapor Control SystemVapor Control System
PrinciplesPrinciples
The typical marine Vapor Control System
(VCS) consists of a vapor collection
system; an arrangement of piping and
hoses; and a vapor processing unit to
recover or destroy the collected organic
vapors, or vapor destruction unit that
destroys cargo vapor by incineration.

7. Definitions:Definitions:
 Vapor Control System - An arrangement of piping
and equipment used to control vapor emissions
collected from a vessel. It includes the vapor
collection system and vapor processing unit.
 Vapor Collection System - An arrangement of
piping and hoses used to collect vapor emitted from a
vessel's cargo tanks and to transport the vapor to a
vapor processing unit.
 Vapor Processing Unit - The components of a
vapor control system that recovers, destroys, or
disperses vapor collected from a vessel.

8. Definitions:Definitions:
 Vapor Dispersion Unit – A vapor processing unit
which releases cargo vapor to the atmosphere through
a venting system not located on the vessel being
loaded or ballasted.
 Vapor Destruction Unit - A vapor processing unit that
destroys cargo vapors by a means such as
incineration.
 Vapor Recovery Unit – A vapor processing unit that
recovers cargo vapor by non-destructive means such
as lean oil absorption, carbon red adsorption, or
refrigeration.

9. Methods to Process VaporsMethods to Process Vapors
Recovery:
– Carbon Bed Absorption
– Refrigeration
Combustion:
– Open Flare
– Incinerator
Balancing:
– Return captured vapors to tanks being emptied

10. Typical VCS Diagram

11. VCS Diagram Key
Abbreviation Meaning
AE - Analytical Element -
Analyzer
DA - Detonation Arrester
DPH - Differential Pressure High
FA - Flame Arrester
FIC - Flow Indicator Controller
KO DRUM - Knock Out Vessel
LAH - Level Alarm High
LAL - Level Alarm Low
LI - Level Indicator
LSHH - Level Shutdown High
High
LSL - Level Shutdown Low
PAH - Pressure Alarm High
PAL - Pressure Alarm Low
PI - Pressure Indicator
PIC - Pressure Indicator Controller
PSHH - Pressure Shutdown High
High
PSLL - Pressure Shutdown Low Low
PVRV - Pressure Vacuum Relief
Valve
TSH - Temperature Shutdown High

12. VCS Major ComponentsVCS Major Components
 Vapor Destruction or Recovery Unit
 Liquid Knockout Drum/Vessel
 Vapor Blowers
 Compressors or Eductors
 Detonation Arresters
 Flame Arresters
 Oxygen or Hydrocarbon Analyzers
 Pressure/Vacuum Relief Valves
 Emergency Shutoff Valves

13. VCS Operating RequirementsVCS Operating Requirements
 Certificate of
Compliance
 Alarms and
Automated Shutdown
Systems
– Tested 24-hours prior
to transfer
 Verify valve
alignment prior to
transfer
 Specified Cargo
Transfer Rate
 Personnel Trained
 Remotely operated
cargo control valve
 Tank overfill control
system
 Pre-Transfer
Procedures

14. VCS Operating ProceduresVCS Operating Procedures
 24 hour checklist and testing
– Oxygen Levels below 8%
– IG pressure above desired
vapor control set point due to
facility and vessel systems
being made common.
– Deck seal and PV breaker
checks of liquid level.
– Vessels preliminary leak
tightness checks.
– IG and VCS valves tested for
proper operation and position.
– COT high level and overfill
alarms.
– Vessel Gauging System.
 Conduct a pre-transfer
conference and follow any
checklists.
 Determine loading and
connection process and crew’s
adherence to PPE for toxic
cargo.
 Follow company and terminal
procedures on VCS operations.
 Follow company and terminal
guidelines for cargo
completion.
 Follow abnormal operating
procedures, guidelines, and
ensure according to agreed
plan.

15. VCS HazardsVCS Hazards
 Fire or Explosion
 Vapor Over-pressurization
 Vacuum
 Liquid Overfill into VCS
– Fire/Explosion
 Misconnections of Hoses
– Cargo hose on Vapor Connection
 Use of Studded Flange to prevent misconnection
 Static Electricity
 Pyrophoric Deposits
 Vapor Exposure

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