SAN LUIS OBISPO COUNTY AIR POLLUTION CONTROL DISTRICT
RULE 431 - STATIONARY INTERNAL COMBUSTION ENGINES
This Rule applies to any stationary internal combustion engine rated at greater than 50 brake horsepower and
operated on any gaseous or liquid fuel, including but not limited to gasoline, natural gas, field gas, waste gas,
liquefied petroleum gas (LPG), or diesel fuel.
- "Diesel Engine": A compression ignited two or four-stroke engine in which liquid fuel injected into
the combustion chamber ignites when the air charge has been compressed to a temperature sufficiently high for auto-ignition.
- "Emergency Standby Engine": An internal combustion engine used only as follows:
a. When normal power line or natural gas service fails; or
b. For the emergency pumping of water for either fire protection or flood relief.
An emergency standby engine may not be operated to supplement a primary power source when the load capacity
or rating of the primary power source has been either reached or exceeded.
- "Lean-burn Engine": Any two or four-stroke spark-ignited engine that is not a rich-burn engine.
- "Location": Any single site at a building, structure, facility, or installation.
- "Maintenance Operation": The use of an emergency standby engine and fuel system during testing, repair
and routine maintenance to verify its readiness for emergency standby use.
- "Rated Brake Horsepower": The maximum brake horsepower rating at maximum revolutions per minute (rpm)
specified for the engine by the manufacturer. Alternately the rated brake horsepower of an engine shall be the
maximum allowable and enforceable rating specified by the District, stated in the Permit to Operate, and accepted
by the engine operator.
- "Retrofit": A modification to an existing engine in which an aftercooler, turbocharger, or emissions
control device has been added or the engine has been rebuilt to the extent that the crankshaft has been removed
- "Replacement": The removal of an existing engine and subsequent installation of a different engine
in its place.
- "Rich-burn Engine": Any four-stroke, naturally aspirated, spark-ignited engine or any spark-ignited
internal combustion engine that is operated with an exhaust stream oxygen concentration of less than four (4) percent
by volume before add-on controls. For engines using a catalyst, the exhaust gas oxygen content shall be determined
from the uncontrolled exhaust stream before the catalyst.
- "Stationary Internal Combustion Engine": Any internal combustion engine of the reciprocating type
that is operated at the same location for more than one year or is attached to a foundation.
With the exception of recordkeeping and reporting requirements necessary to justify an exemption, the provisions
of this Rule shall not apply to the operation of stationary internal combustion engines used under the following
- Engines rated at less than or equal to 50 brake horsepower.
- Engines operated less than 200 hours per calendar year.
- Emergency standby engines operated during either an emergency or maintenance operation. Maintenance operation
is limited to 100 hours per calendar year.
- Engines used in research or teaching programs.
- Engines used in agricultural operations in the growing of crops or the raising of fowl or animals.
- Engine test stands used for evaluating engine performance.
- Diesel engines used to power cranes and welding equipment.
- Spark-Ignited Engines: The owner or operator of a spark-ignited engine to which this Rule is applicable
shall limit emissions from that engine to no more than the following:
In lieu of compliance with a NOx emission limit in Subsection D.1, the owner or operator of a spark-ignited
engine may achieve and maintain a NOx reduction by volume percentage specified below:
NOx reduction by volume percentages shall be determined in accordance with Subsections F.1 and F.2. The emission
limits for CO listed in Subsection D.1 shall still be applicable.
- Diesel Engines: The owner or operator of a diesel engine shall limit emissions from that engine or its
replacement to no more than 600 ppmv NOx, or a NOx reduction by volume percentage of 30 percent as determined
in accordance with Subsections F.1 and F.2. In addition, and CO emissions shall be limited to 4500 ppmv.
All ppmv values shall be referenced at dry stack-gas conditions and 15 percent by volume stack-gas oxygen.
- No person shall allow the discharge into the atmosphere of ammonia (NH3) emissions in excess of
20 ppmv from any emission control device requiring NH3 installed and operated pursuant to
the requirements of Subsection D.1, D.2, or D.3 above.
- The owner or operator of any stationary internal combustion engine subject to the provisions of Section D of
this Rule shall demonstrate compliance with the emission limits at least once every 8760 hours of engine operation
or once every three (3) calendar years, whichever comes first.
E. ENGINE OPERATOR INSPECTION PLAN
The owner or operator of an engine subject to the provisions of Subsection D.1, D.2, or D.3 of this Rule shall
submit an Engine Operator Inspection Plan (Plan) for approval by the Air Pollution Control Officer (APCO). The
Plan shall be updated after any change in operation. The operator may request a change to the Plan at any time.
The Plan shall include the following:
- The manufacturer, model number, rated horsepower, and combustion type (i.e., rich-burn, lean-burn, or diesel)
of the engine.
- A description of the NOx control system installed on the engine (if any), including type (e.g., nonselective
catalyst, "clean-burn" combustion) and manufacturer, as well as a description of any ancillary equipment
related to the control of emissions (e.g., automatic air/fuel ratio controller, fuel valves).
- The facility-defined equipment identification number and the location of the engine on a map or plot plan of
the affected facility.
- A specific engine inspection procedure to ensure that the engine is operated in compliance with the provisions
of this Rule. The procedure shall include an inspection schedule and the inspection log format as required by Section
G below. Inspections shall be conducted every quarter or after every 2,000 hours of engine operation. In no event
shall the frequency of inspection be less than once per year.
- A description of each preventive or corrective maintenance procedure or practice that will be used to maintain
the engine and NOx control system in compliance with the provisions of this Rule.
F. TEST METHODS
- NOx and CO emissions, and oxygen content for compliance source tests shall be determined by using ARB Method
- Percentage NOx reductions shall be determined by measuring concurrently at the inlet and outlet of the emission
control device. For engines not employing emission control devices, percentage NOx reductions shall be determined
by measuring the uncontrolled NOx emissions prior to modification and comparing with NOx emissions after engine
modification. A source test plan for the measurement of uncontrolled NOx emissions shall be submitted to the District
for approval no less than 15 days prior to testing.
- Source test data point intervals shall be no greater than five (5) minutes and data points shall be averaged
over fifteen (15) consecutive minutes.
- NH3 emissions shall be determined using Bay Area Air Quality Management District Method ST-1B.
- An alternative source test method may be used provided the alternative method is at least as accurate as the
test methods listed above and further provided that the alternative method has been approved by the ARB and EPA,
and has received prior written approval from the APCO.
- The operator of any engine subject to the provisions of Section D of this Rule shall maintain an inspection
log that includes, on a monthly basis the following data:
a. Date and results of each engine inspection,
b. A summary of any preventive or corrective maintenance taken,
c. The total hours of operation,
d. The type and quantity of fuel used, and
e. Any additional information required in the Engine Operator Inspection Plan.
- The operator shall maintain the inspection log for a period of three (3) years after the date of each entry.
The log shall be available for inspection by the District upon request.
On or before March 1 of each year, each owner or operator with engines subject to the provisions of this Rule
shall submit a report to the APCO specifying the actual annual fuel usage and operating hours for each affected
engine. The report shall also include the engine manufacturer, model number, facility-defined equipment identification
number, and a summary of the maintenance reports as required in Section G.
J. COMPLIANCE SCHEDULE
- All subsections of this Rule shall apply to any new facility or source obtaining an initial District Permit
to Operate on or after November 13, 1996.
- Spark-Ignited Engines:
a. Any person required to modify or replace an existing, spark-ignited, stationary internal combustion engine
to comply with the requirements of this Rule shall submit a complete Authority to Construct application to the
APCO no later than May 1, 1999.
b. Any person with an existing, modified, or replacement, spark-ignited, stationary internal combustion engine
shall demonstrate final compliance no later than May 1, 2000.
- Diesel Engines: After May 1, 2000, any person with an existing stationary internal combustion diesel
engine to which this Rule is applicable shall comply with the requirements of Subsection D.3 upon retrofit or replacement
of that diesel engine. A complete Authority to Construct Application shall be submitted to the APCO at least 60
days prior to retrofit or replacement.
- The owner or operator of an engine subject to the provisions of Subsection D.1, D.2, or D.3 shall submit an
Engine Operator Inspection Plan no later than 60 days after the applicable compliance date listed in Section J.