DESIGN CRITERIA

                     FOR

        STAGE I VAPOR CONTROL SYSTEMS

          GASOLINE SERVICE STATIONS
    U. S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF AIR QUALITY PLANNING AND STANDARDS
EMISSION STANDARDS AND ENGINEERING DIVISION
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
                NOVEMBER 1975

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                CRITERIA  FOR STAGE I  SERVICE STATION CONTROL SYSTEMS
    Background

         Transportation  Control  Plans  (TPC's)  promulgated by EPA in 1973
    and  1974  include requirements for  the control  of gasoline vapors at
    service stations in  some 17  Air Quality Control  Regions (AQCR's)
    throughout  the  nation.   In all  cases, control  of gasoline vapors during
    storage tank  filling (.Stage  I sources) is  required.   In many areas,
    control of  vehicle fueling  (Stage  II sources)  is also required.  For
    storage tank  filling,  EPA regulations prohibit the release of more than
    10  percent  by weight of displaced  organic  vaoors.

         While  Stage I vapor control  systems are relatively new, there has
    been substantial testing which shows that  compliance with prescribed
    limits can  be accomplished at commerical service stations.  Tests by
    oil  companies,  '^'  EPA,  and a local control  agency^ indicate that
    efficiencies  greater than 90 percent are effected with simple balance
    systems- if  certain common design elements  are  employed and if the
    equipment is  properly maintained and operated.  Based primarily on this
    testing,  criteria have been  developed for  Stage I control systems.
    The  purpose of  this  document is to provide direction to operators
    who  are required to  install  vapor recovery systems.

         These  criteria  list the key features  of systems which have been
    found to  meet Stage  I requirements.  Systems incorporating different
    criteria  may be installed if test data are supplied to show that they
    meet the  emission limitation and other provisions of the Stage I
    regulations.

         All  current systems used to control emissions from storgage tank
    filling  return  displaced vapors to the tank truck.  Vapor balance
    (displacement)  systems release any excess vapors to the atmosphere;
    vacuum assist systems process excess vapors in secondary recovery
    units.

         As  shown in the vapor balance systems of Figures 1 and 2 and
    the secondary system in Figure 3,  flexible hoses carry liquid gasoline
    from the  tank truck down a drop tube to the underground tank.  Entering
    liquid forces the air-hydrocarbon mixture in the tank out through a
    flexible  hose to the tank truck.  Alternately, the vapors may exit from
    the underground tank through a vent  pipe (about 2 inches in diameter)
    extending at least 12 feet above ground level  (OSHA and National Fire
    Protection Code 30 requirement).  At the truck, the vapor hose is
    connected to a  piping manifold which may serve as a rollover rail to
    prevent damage to the tank in case the truck is overturned.  The roll-
    over rail piping is interconnected with the truck compartments by vents
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                                    - 2 -

which are opened selectively durinq truck unloadinq, allowina  returnina
vapors from the underground tank to enter respective product compartments
on the truck.

Two-Point Systems

    The most effective method of conductinq displaced  vapors from  the
underqround tank to the truck is by means of a separate  connection  to
the underground tank for the 3-inch vapor return hose, as  shown  in
Figure 1.  The vast majority of the tests showina comoliance with
prescribed limits are from systems utilizinq this feature.

Concentric or Coaxial Systems

    However, in some cases a separate entry is not  available or  the
operator desires to avoid the excavation necessary  to  reach an unused
entry.  For these cases, coaxial devices have been  developed to  remove
the vapors through the same opening through which the  fuel  is  delivered.

    In one system, shown in Figure 4, a droo tube of smaller diameter
is inserted in the existing fuel riser.  The vaqors exit through the
annular space.  A coaxial adaptor fits on the riser and  provides
connections for the fuel delivery hose and the vapor return hose.
In another system, shown in Figure 5, the fuel and  vapor passages
are separated in a "Y" fitting which  is permanently attached to  the
underground tank/" The fittings for the hose connections are located
in a  conventional manhole.  A 5-inch  coaxial fitting is  shown  in Figure  7.
Most  of these devices provides less cross-sectional area in the  vapor
return passaqe than do' separate connectors and tend to reduce  vapor
recovery efficiency to some extent.   Vent pipe restrictions will improve
efficiencies.

Manifolded Vent Lines

    Several  schemes have been used to manifold vents from two  or more
tanks- to a common vapor hose connection,  ^anifoldinq  may be above or
below grade.  A number of configurations are acceptable  for use  with
suitable vent restrictions  as shown  in Figure 8.  The  3-way connector
of Fiaure ?  provides  the most effective arranaement since connection
of the vapor  hose to  the common connector blocks flow  to the atmosphere
and routes all displaced vapor to  the tank truck.   In  any manifold piping
system, care  must be  exercised to  prevent contamination  of "no-lead"
gasoline product.

Objectives of Design  Criteria

    Design criteria presently included  in this document  pertain  primarily
to commercial stations where  filling  conditions  are most severe.  Here
there are usually two or three storage  tanks, each  of  which  ranqe UP to
10,000 gallons  in capacity.  They  are normally  filled  from a  tank truck

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                                    - 3 -

of about 4,000-gallon capacity if a sinqle tanker or 8,000-qallon  capacity
if a trailer is added.  Each truck and trailer  is compartmented  such  that
different grades of gasoline can be transported without  comingling.

    Normal practice at commercial stations is to fill storaqe  tanks at
a rate of 200 to 500 gallons oer minute.  Thus, a typical  4,000-aallon
droo may be accomplished in 10 to 20 minutes.   The  drop  rate  is  critical
since it governs the rate of vapor transfer.  Where slower fill  rates are
used, ft may be possible to use smaller transfer hoses and connections.
Also, leakage at storage tanks and tank trucks  tends to  be of  lesser
magnitude at slower filling rates.

    Criteria were developed to accomplish the following:
         assure submerged fill, i.e., discharge  liquid  below
    the gasoline surface in the storaqe  tank,

    (b)  assure that the vapor return line and connections
    are of sufficient size and sufficiently  free of  restrictions
    to allow transfer of vapor to  the truck  tank and achieve
    the desired recovery,

    (cj  assure that there are no  significant  leaks  in  the
    system or the tank  truck which  reduce vacuum in  the truck
    or otherwise inhibit vapor transfer,

    Cd)  assure that the vapor return line will  be connected
    during tank, filling.

    In addition, cognizance has been  taken of  safety requirements  of
the Occupational Safety and Health  Administration (OSHA)'  and  the
recommendations of  the  National Fire  Protection  Association.

Design Criteria

1.  Drop Tube Specifications.  Submerged  fill  is specifically  required
By certain TCP regulations wn.il a  others  are  silent on the method  of
filling.  All test  data submitted  to  EPA  were  obtained  from systems
utilizing submerged fill.  If submerged  fill  is  not  used, test data
must be submitted to show the required recovery  will be obtained.
The submerged fill  requirement is interpreted  to mean a drop  tube
extendfnq to within 6  inches of the tank  bottom.  Under normal  industry
practices, a tube meeting this specification will always  be submerged
sines  the tanks are not pumped dry.

    Deviation from  the  criteria will  be  allowed  if the  owner/operator
shows  that a shorter tube will guarantee  sufamerqed fill.   In  such
instance, the owner/operator is required  to  present  records which  show

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                                    - 4 -

that the level in the tank never falls below the drop tube.   Exceptions
also will be allowed for tanks which cannot be converted  to submerged
fill, e.g., tanks with offset fill lines or ooor accessibility.

2.  Gauoe Wei 1.   If a gauge well separate from the fill tube  is  used,
it must be provided with a drop tube which extends to within  6  inches
of the tank bottom.  This will prevent vapor emissions  in  case  the  gauge
well cap is not replaced during a drop.

3.  Vapor Hose Return.  Existing data indicate that a 3-inch  ID  hose
is needed to transfer vapors from the storage tank to the  truck  when a
4-inch drop tube is used.  Smaller diameter hoses may be  satisfactory
where fill rates are appreciably less than 400 aallons  per minute.
If a hose smaller than 3 inches is to be used, the owner/operator is
required to show that the hose will achieve the required  vapor  recovery.

4.  Vapor Line Connections.  Where separate vapor lines are used with
4-inch product tubes, nominal 3-inch or larger connections should be
utilized at the storage tank and truck-trailer.  When smaller product
tubes are used, a smaller vapor line connection may be  used,  provided  the
ratio of the cross-sectional area of the connection to  the cross-sectional
area of the product tube is 1:2 or greater.  If the ratio  is  smaller,  test
data must be provided to show the required recovery efficiency  will be met.

    Vapor lines from two or more tanks may be manifolded  to a common
vapor hose connector using configurations typified by Figures 8  and 9.

    For concentric or other tube-in-tube fittings, operatina  characteristics
are uniaue to the particular design.  To date, adequate test  data have been
supplied for 4-inch and 5-inch tube-in-tube adapters.   These  are listed
in Attachment A.  Other fittings will be added to Attachment  A when supporting
data are supplied.  If fittinas not listed are to be used, test  data must
Be provided.

5".  Type of Liquid Fill Connection.  Vapor tight caps are  required  for the
liquid fill connection for all systems.  A positive closure utilizing  a
gasket or other similar sealino surface is necessary to prevent  vaoors from
being emitted at around level.  Cam-lock closures meet  this requirement.
Dry-breafc closures also are acceptable, but are not required.

5".  Tank Truck^Inspection.  Vapor tiaht tank trucks are specifically required
by TCP regulations-,  fhis is interpreted to mean that the  truck  compartments
won^t vent gases or draw in air unless the settings of  the pressure-vacuum
relief valves are exceeded.  An inspection procedure should be  submitted to
include freouent visual inspection and leak testing at  least  twice  per year.
Leak testing should demonstrate that the tank truck when  pressurized to
5 inches W.C. will not leak to a pressure of 2 inches W.C. in less  than

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                                    - 5 -

3 minutes.   Frequent visual inspection is necessary to insure proper
operation of manifolding and relief valves.

7.  Closures or ^Interlocks on Underground Tank Vapor Hose Connectors.
Closures or interlocks are required to assure transfer of displaced vapors
to the truck and to prevent ground level gasoline vapor emissions due to
failure to connect the vapor return line to the underground tanks.
These devices must be designed:  (a) to keep the storage tank sealed
unless the vapor hose is connected to it; or (b) to prevent delivery of
fuel until the vapor hose  is connected, i.e., an interlock.  Tank openings
designed for combined fill and vapor recover shall also be protected against
vapor release unless connection of the liquid delivery line to  the fill
pipe simultaneously connects the vapor recovery line, e.g., an  interlock.
All connections must be vapor tight.

8.  Vaoor Hose Connection  to the Tank Truck.  A means must be provided
to assure that tne vapor hose is connected  to the truck before  fuel  is
delivered.  Acceptable means of providing  this assurance include:
(a) permanent connection of the vapor hose  to the truck; (b) an  inter-
lock which prevents fuel delivery unless the vapor hose is connected,
such as a bracket to which the product and  vapor hose are permanently
attached so that neither hose can be connected separately; and  (c) a
closure in the vapor hose  which remains closed unless the hose  is
attached to the vapor fitting on the truck.

9.  Vent Line Restrictions.  Vent line restrictions  improve recovery
efficiency and provide assurance that  the  vapor return  line will  be
connected durfng transfer.   If the  liquid  fill line were attached  to
the underground tank and the vapor  return  line disconnected, closures
would seal the vapor return  path to  the  truck forcing all vapors  out
the vent line.  Restriction  of the  vent  line through  the use of an
orifice or pressure-relief valve greatly reduces fill rate in  such
 instances warning  the operator that  the  vapor line  is not connected.

      Suitable restrictive  orifices  or  pressure-relief valves are required
wherever  the  systems would otherwise  be  incapable  of  achieving  90 percent
 control  or would otherwise not assure  that the vapor  return  line is
 connected.   For available  hardware  this  means that  these  restrictive  devices
 are necessary  for  all except systems  with  interlock  connections at both
 the truck  and  storage  tank.


      Either  of  the  following restrictive devices  are  acceptable:

      Ca)   Orifice  of  1/2  to  3/4  inch ID.

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                                    - 6 -

     (b)  Pressure-vacuum relief valve set to open at 8 oz. per
     square inch or greater pressure and 4 02. per square inch
     or greater vacuum.  The vacuum relief feature of a P-V valve
     is not required for Stage I recovery purposes but may be
     required by safety authorities.

The NFPA Interim Amendments (April 1975) to Code 30 require that when
vent restriction devices are used the tank and associated piping be
protected to limit back pressure development to less than the maximum
working pressure of the tank and equipment by the provision of pressure
vacuum vents, rupture discs or other tank venting devices installed in the
tank vent lines, and that these devices shall be protected to minimize the
possibility of blockage from weather, dirt, or insect nests.  Local fire
marshals should be consulted regarding the use of these devices in your
area.

References

1.  Performance of Service Station Vapor Control Concepts, Scott
    Research Laboratories for the American Petroleum Institute, Interim
    Report, June 26, 1974.

2.  Service Station Vapor Recovery, Atlantic-Richfield Company,
    April 8, 1974,
                    /
3.  Presten, J. E. et al, The "Displacement" System:  An Effective
    Method of Controlling Hydrocarbons, November 1973.

4.  TRW Contract Test,. June 1974, San Diego, California.

5.  Bay Area Air Pollution Control District, 1974.

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                                         -  7  -
       Comparcnenc
       Venc Valves
                                                Orifice or P-V Valve
                                                Unless Product and
                                                Vapor Hoses are
                                                Interlocked.
                                                   Orybreak,
                                                   interlock or
                                                   Permanent
                                                   Connection
 Figure  1.
 Vapor balancing with
 separate  liquid -  vapor
 risers.
       Coapartaenc
       VenC  Valves
                                                    Orifice or P-V Valve
                                                    Unless Product and -^.
                                                    Vapor Hoses are
                                                    Interlocked.
                                                               U. Q. Tank _
                                                               Vent Pipe
                                                               (usually 2")
                                                   Oryoreak,
                                                   interlock or
                                                   Permanent
                                                         tions
                                                              Co-Axial
                                                               Slbow
                                                             Connection
                 Vapor Return
                 Hose (3"  ID)
Figure 2.
Vapor balancing with single,
concentric liquid - vapor
riser.
        Compartaanc
        Vent Valves
                                                                           P-V Valve -
   Figure  3.   Secondary  recovery with
              separate  liquid  - vapor
              risers.
                                                                                              Secondary
                                                                                              Processing
                                                                                              Unit
                                                    Orybreak,
                                                    Interlock or
                                                    Permanent
                                                             ns
                 Vapor Return
                 Hose (3"  ID)

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  s.^.^nafieas?^
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                                Figure 4.   Coaxial  Fittin;
                                and Fill Tube Adapter.
                                Emco Wheaton  Inc.

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                                       -  9  -
  NEW OPW 306-AO-12" x  24" MANHOLE
  EXISTING CAP AND ADAPTOR
            OR
  NEW OPW S34-TT-4"  CAP
           AND
  633-T-4" x 4" ADAPTOR
            OR
  62-TT-4" CAP OR 52-4" CAP
           AND
  61-AS-4" x 4" ADAPTOR	
  NEW OPW 313-V-4" x 4" x 3"
        "Y" FITTING
  NEW OPW 61-TD-4" x lO'-O"
        DROP PIPE
Of
                 VAPOR  AREA
OPW 1711-TK-3" CAP
        OR
    OPW 1711-KV-3"
        CAP
   OPW 1611-AV-3"
      ADAPTOR
                                                EXISTING UNDERGROUND STORAGE TANK
                                                                 4  P/PE
                                                                       Figure  5.    "Y" Tube-
                                                                       Tube  Vapor  Return  F
                                                                       Dover Corporation/01
                                                                       Division

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                                       -  10 -
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               Figure 6.   Coaxial  Fitting for  6"  Riser Pipes.

                           Parker Hannifin,  Inc.

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                                   - 13  -
                                     Closes  when vapor hose
                                     is  attached.
Vapor Line
Product Line
                Figure 9.  Aboveground Manifolding of  Vapor Lines

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                               - 14 -
                            Attachment A*
                       (Revised November 1975)
Concentric and tube-in-tube couplers for which test data show acceptable
performance:

     1.  Emco Wheaton 4-inch Coaxial Fitting F-278, adapter and Drop
         Tube Assembly A70-001.

     2.  Emco Wheaton 4-Inch Coaxial Fitting F-278.  Adapter with a
         4-inch to 3-inch bushing and Drop Tube Assembly A70-003.

     3.  Dover Corporation/OPW Division 4-inch Tube-In-Tube Y-Fitting
         No. 318 with 61-TD-4 Inch Drop Pipe.

     4.  Parker Hannifin 6-inch Coaxial Fitting F-219 with a 6-inch
         Straight Riser or a 6-inch by 4-inch Riser.

     5.  Universal Valve 4-inch Fill/Vapor Return Fitting No. 715.
*This attachment has no relation to "two point" systems, i.e., systems
with a separate connection for the vapor return hose to the underground
tank.  Such systems are to be evaluated by the Criteria.

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