
[Code of Federal Regulations]
[Title 30, Volume 1]
[Revised as of July 1, 2001]
From the U.S. Government Printing Office via GPO Access
[CITE: 30CFR7]

[Page 28-46]
 
                       TITLE 30--MINERAL RESOURCES
 
  CHAPTER I--MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR
 
PART 7--TESTING BY APPLICANT OR THIRD PARTY--Table of Contents
 
Subpart E--Diesel Engines Intended for Use in Underground Coal Mines

    Source: 61 FR 55504, Oct. 25, 1996, unless otherwise noted.

Sec. 7.81  Purpose and effective date.

    Subpart A general provisions of this part apply to this subpart E. 
Subpart E establishes the specific engine performance and exhaust 
emission requirements for MSHA approval of diesel engines for use in 
areas of underground coal mines where permissible electric equipment is 
required and areas where non-permissible electric equipment is allowed. 
It is effective November 25, 1996.

Sec. 7.82  Definitions.

    In addition to subpart A definitions of this part, the following 
definitions apply in this subpart.
    Brake Power. The observed power measured at the crankshaft or its 
equivalent when the engine is equipped only with standard auxiliaries 
necessary for its operation on the test bed.
    Category A engines. Diesel engines intended for use in areas of 
underground coal mines where permissible electric equipment is required.
    Category B engines. Diesel engines intended for use in areas of 
underground coal mines where nonpermissible electric equipment is 
allowed.

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    Corrosion-resistant material. Material that has at least the 
corrosion-resistant properties of type 304 stainless steel.
    Diesel engine. Any compression ignition internal combustion engine 
using the basic diesel cycle where combustion results from the spraying 
of fuel into air heated by compression.
    Exhaust emission. Any substance emitted to the atmosphere from the 
exhaust port of the combustion chamber of a diesel engine.
    Intermediate speed. Maximum torque speed if it occurs between 60 
percent and 75 percent of rated speed. If the maximum torque speed is 
less than 60 percent of rated speed, then the intermediate speed shall 
be 60 percent of the rated speed. If the maximum torque speed is greater 
than 75 percent of the rated speed, then the intermediate speed shall be 
75 percent of rated speed.
    Low idle speed. The minimum no load speed as specified by the engine 
manufacturer.
    Maximum torque speed. The speed at which an engine develops maximum 
torque.
    Operational range. All speed and load (including percent loads) 
combinations from the rated speed to the minimum permitted engine speed 
at full load as specified by the engine manufacturer.
    Particulates. Any material collected on a specified filter medium 
after diluting exhaust gases with clean, filtered air at a temperature 
of less than or equal to 125  deg.F (52  deg.C), as measured at a point 
immediately upstream of the primary filter. This is primarily carbon, 
condensed hydrocarbons, sulfates, and associated water.
    Percent load. The fraction of the maximum available torque at an 
engine speed.
    Rated horsepower. The nominal brake power output of a diesel engine 
as specified by the engine manufacturer with a specified production 
tolerance. For laboratory test purposes, the fuel pump calibration for 
the rated horsepower must be set between the nominal and the maximum 
fuel tolerance specification.
    Rated speed. Speed at which the rated power is delivered, as 
specified by the engine manufacturer.
    Steady-state condition. Diesel engine operating condition which is 
at a constant speed and load and at stabilized temperatures and 
pressures.
    Total oxides of nitrogen. The sum total of the measured parts per 
millions (ppm) of nitric oxide (NO) plus the measured ppm of nitrogen 
dioxide (NO<INF>2</INF>).

Sec. 7.83  Application requirements.

    (a) An application for approval of a diesel engine shall contain 
sufficient information to document compliance with the technical 
requirements of this subpart and specify whether the application is for 
a category A engine or category B engine.
    (b) The application shall include the following engine 
specifications--
    (1) Model number;
    (2) Number of cylinders, cylinder bore diameter, piston stroke, 
engine displacement;
    (3) Maximum recommended air inlet restriction and exhaust 
backpressure;
    (4) Rated speed(s), rated horsepower(s) at rated speed(s), maximum 
torque speed, maximum rated torque, high idle, minimum permitted engine 
speed at full load, low idle;
    (5) Fuel consumption at rated horsepower(s) and at the maximum rated 
torque;
    (6) Fuel injection timing; and
    (7) Performance specifications of turbocharger, if applicable.
    (c) The application shall include dimensional drawings (including 
tolerances) of the following components specifying all details affecting 
the technical requirements of this subpart. Composite drawings 
specifying the required construction details may be submitted instead of 
individual drawings of the following components--
    (1) Cylinder head;
    (2) Piston;
    (3) Inlet valve;
    (4) Exhaust valve;
    (5) Cam shaft--profile;
    (6) Fuel cam shaft, if applicable;
    (7) Injector body;
    (8) Injector nozzle;
    (9) Injection fuel pump;
    (10) Governor;
    (11) Turbocharger, if applicable;
    (12) Aftercooler, if applicable;
    (13) Valve guide;

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    (14) Cylinder head gasket; and
    (15) Precombustion chamber, if applicable.
    (d) The application shall include a drawing showing the general 
arrangement of the engine.
    (e) All drawings shall be titled, dated, numbered, and include the 
latest revision number.
    (f) When all necessary testing has been completed, the following 
information shall be submitted:
    (1) The gaseous ventilation rate for the rated speed and horsepower.
    (2) The particulate index for the rated speed and horsepower.
    (3) A fuel deration chart for altitudes for each rated speed and 
horsepower.

Sec. 7.84  Technical requirements.

    (a) Fuel injection adjustment. The fuel injection system of the 
engine shall be constructed so that the quantity of fuel injected can be 
controlled at a desired maximum value. This adjustment shall be 
changeable only after breaking a seal or by altering the design.
    (b) Maximum fuel-air ratio. At the maximum fuel-air ratio determined 
by Sec. 7.87 of this part, the concentrations (by volume, dry basis) of 
carbon monoxide (CO) and oxides of nitrogen (NO<INF>X</INF>) in the 
undiluted exhaust gas shall not exceed the following:
    (1) There shall be no more than 0.30 percent CO and no more than 
0.20 percent NO<INF>X</INF> for category A engines.
    (2) There shall be no more than 0.25 percent CO and no more than 
0.20 percent NO<INF>X</INF> for category B engines.
    (c) Gaseous emissions ventilation rate. Ventilation rates necessary 
to dilute gaseous exhaust emissions to the following values shall be 
determined under Sec. 7.88 of this part:


Carbon dioxide.........................  -5000 ppm
Carbon monoxide........................  -50 ppm
Nitric oxide...........................  -25 ppm
Nitrogen dioxide.......................  -5 ppm



A gaseous ventilation rate shall be determined for each requested speed 
and horsepower rating as described in Sec. 7.88(b) of this part.
    (d) Fuel deration. The fuel rates specified in the fuel deration 
chart shall be based on the tests conducted under paragraphs (b) and (c) 
of this section and shall ensure that the maximum fuel:air (f/a) ratio 
determined under paragraph (b) of this section is not exceeded at the 
altitudes specified in the fuel deration chart.
    (e) Particulate index. For each rated speed and horsepower 
requested, the particulate index necessary to dilute the exhaust 
particulate emissions to 1 mg/m<SUP>3</SUP> shall be determined under 
Sec. 7.89 of this part.

Sec. 7.85  Critical characteristics.

    The following critical characteristics shall be inspected or tested 
on each diesel engine to which an approval marking is affixed--
    (a) Fuel rate is set properly; and
    (b) Fuel injection pump adjustment is sealed, if applicable.

Sec. 7.86  Test equipment and specifications.

    (a) Dynamometer test cell shall be used in determining the maximum 
f/a ratio, gaseous ventilation rates, and the particulate index.
    (1) The following testing devices shall be provided:
    (i) An apparatus for measuring torque that provides an accuracy of 
<plus-minus>2.0 percent based on the engine's maximum value;
    (ii) An apparatus for measuring revolutions per minute (rpm) that 
provides an accuracy of <plus-minus>2.0 percent based on the engine's 
maximum value;
    (iii) An apparatus for measuring temperature that provides an 
accuracy of <plus-minus>4  deg.F (2  deg.C) of the absolute value except 
for the exhaust gas temperature device that provides an accuracy of 
<plus-minus>27  deg.F (15  deg.C);
    (iv) An apparatus for measuring intake and exhaust restriction 
pressures that provides an accuracy of <plus-minus>5 percent of maximum;
    (v) An apparatus for measuring atmospheric pressure that provides an 
accuracy of <plus-minus>0.5 percent of reading;
    (vi) An apparatus for measuring fuel flow that provides an accuracy 
of <plus-minus>2 percent based on the engine's maximum value;
    (vii) An apparatus for measuring the inlet air flow rate of the 
diesel engine that provides an accuracy of <plus-minus>2 percent based 
on the engine's maximum value; and

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    (viii) For testing category A engines, an apparatus for metering in 
1.0 <plus-minus>0.1 percent, by volume, of methane (CH<INF>4</INF>) into 
the intake air system shall be provided.
    (2) The test fuel specified in Table E-1 shall be a low volatile 
hydrocarbon fuel commercially designated as ``Type 2-D'' grade diesel 
fuel. The fuel may contain nonmetallic additives as follows: Cetane 
improver, metal deactivator, antioxidant, dehazer, antirust, pour 
depressant, dye, dispersant, and biocide.

               Table E-1--Diesel Test Fuel Specifications
------------------------------------------------------------------------
              Item                     ASTM              Type 2-D
------------------------------------------------------------------------
Cetane number..................  D613             40-48.
Cetane index...................  D976             40-48.
Distillation range:
    IBP  deg.F.................  D86              340-400.
        ( deg.C)...............  ...............  (171.1-204.4).
    10 pct. point,  deg.F......  D86              400-460.
        ( deg.C)...............  ...............  (204.4-237.8).
    50 pct. point,  deg.F......  D86              470.540.
        ( deg.C)...............  ...............  (243.3-282.2).
    90 pct. point,  deg.F......  D86              560-630.
        ( deg.C)...............  ...............  (293.3-332.2).
    EP,  deg.F.................  D86              610-690.
        ( deg.C)...............  ...............  (321.1-365.6).
Gravity, deg.API...............  D287             32-37.
Total sulfur, pct..............  D2622            0.03-0.05.
Hydrocarbon composition:
    Aromatics, pct.............  D1319            27 minimum.
    Paraffins, naphthenes,       D1319            Remainder.
     olefins.
Flashpoint, minimum,  deg.F....  93               130.
    ( deg.C)...................  ...............  (54.4).
Viscosity, centistokes.........  445              2.0-3.2.
------------------------------------------------------------------------

    (3) The test fuel temperature at the inlet to the diesel engine's 
fuel injection pump shall be controlled to the engine manufacturer's 
specification.
    (4) The engine coolant temperature (if applicable) shall be 
maintained at normal operating temperatures as specified by the engine 
manufacturer.
    (5) The charge air temperature and cooler pressure drop (if 
applicable) shall be set to within <plus-minus>7  deg.F(4  deg.C) and 
<plus-minus>0.59 inches Hg (2kPa) respectively, of the manufacturer's 
specification.
    (b) Gaseous emission sampling system shall be used in determining 
the gaseous ventilation rates.
    (1) The schematic of the gaseous sampling system shown in Figure E-1 
shall be used for testing category A engines. Various configurations of 
Figure E-1 may produce equivalent results. The components in Figure E-1 
are designated as follows--
    (i) Filters--F1, F2, F3, and F4;
    (ii) Flowmeters--FL1, FL2, FL3, FL4, FL5, FL6, and FL7;
    (iii) Upstream Gauges--G1, G2, and G5;
    (iv) Downstream Gauges--G3, G4, and G6;
    (v) Pressure Gauges--P1, P2, P3, P4, P5, and P6;
    (vi) Regulators--R1, R2, R3, R4, R5, R6, and R7;
    (vii) Selector Valves--V1, V2, V3, V4, V6, V7, V8, V15, and V19;
    (viii) Heated Selector Valves--V5, V13, V16, and V17;
    (ix) Flow Control Valves--V9, V10, V11 and V12;
    (x) Heated Flow Control Valves--V14 and V18;
    (xi) Pump--Sample Transfer Pump;
    (xii) Temperature Sensor--(T1);
    (xiii) Dryer--D1 and D2; and
    (xiv) Water traps--WT1 and WT2.
    (A) Water removal from the sample shall be done by condensation.
    (B) The sample gas temperature or dew point shall be monitored 
either within the water trap or downstream of the water trap and shall 
not exceed 45  deg.F (7  deg.C).
    (C) Chemical dryers are not permitted.

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[GRAPHIC] [TIFF OMITTED] TR25OC96.000

    (2) The schematic of the gaseous sampling system shown in Figure E-2 
shall be used for testing category B engines. Various configurations of 
Figure E-2 may produce equivalent results. The components are designated 
as follows--
    (i) Filters--F1, F2, F3, and F4;

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    (ii) Flowmeters--FL1, FL2, FL3, and FL4;
    (iii) Upstream Gauges--G1, and G2;
    (iv) Downstream Gauges--G3, and G4;
    (v) Pressure Gauges--P1, P2, P3, and P4;
    (vi) Regulators--R1, R2, R3, and R4;
    (vii) Selector Valves--V1, V2, V3, V4, V6, and V7;
    (viii) Heated Selector Valves--V5, V8, and V12;
    (ix) Flow Control Valves--V9, V10, V11;
    (x) Heated Flow Control Valves--V13;
    (xi) Pump--Sample Transfer Pump;
    (xii) Temperature Sensor--(T1); and
    (xiii) Water traps--WT1 and WT2.
    (A) Water removal from the sample shall be done by condensation.
    (B) The sample gas temperature or dew point shall be monitored 
either within the water trap or downstream of the water trap and shall 
not exceed 45  deg.F (7  deg.C).
    (C) Chemical dryers are not permitted.
    (3) All components or parts of components that are in contact with 
the sample gas or corrosive calibration gases shall be corrosion-
resistant material.

[[Page 34]]

[GRAPHIC] [TIFF OMITTED] TR25OC96.001

    (4) All analyzers shall obtain the sample to be analyzed from the 
same sample probe.
    (5) CO and CO<INF>2</INF> measurements shall be made on a dry basis.

[[Page 35]]

    (6) Calibration or span gases for the NO<INF>X</INF> measurement 
system shall pass through the NO<INF>2</INF> to NO converter.
    (7) A stainless steel sample probe shall be straight, closed-end, 
multi-holed, and shall be placed inside the exhaust pipe.
    (i) The probe length shall be at least 80 percent of the diameter of 
the exhaust pipe.
    (ii) The inside diameter of the sample probe shall not be greater 
than the inside diameter of the sample line.
    (iii) The heated sample line shall have a 0.197 inch (5 mm) minimum 
and a 0.53 inch (13.5 mm) maximum inside diameter.
    (iv) The wall thickness of the probe shall not be greater than 0.040 
inch (1 mm).
    (v) There shall be a minimum of 3 holes in 3 different radial planes 
sized to sample approximately the same flow.
    (8) The sample probe shall be located in the exhaust pipe at a 
minimum distance of 1.6 feet (0.5 meters) or 3 times the diameter of the 
exhaust pipe, whichever is the larger, from the exhaust manifold outlet 
flange or the outlet of the turbocharger. The exhaust gas temperature at 
the sample probe shall be a minimum of 158  deg.F (70  deg.C).
    (9) The maximum allowable leakage rate on the vacuum side of the 
analyzer pump shall be 0.5 percent of the in-use flow rate for the 
portion of the system being checked.
    (10) General analyzer specifications. (i) The total measurement 
error, including the cross sensitivity to other gases, (paragraphs 
(b)(11)(ii), (b)(12)(iii), (b)(13)(iii), and (b)(13)(iv) of this 
section), shall not exceed <plus-minus>5 percent of the reading or 
<plus-minus>3.5 percent of full scale, whichever is smaller. For 
concentrations of less than 100 ppm the measurement error shall not 
exceed <plus-minus>4 ppm.
    (ii) The repeatability, defined as 2.5 times the standard deviation 
of 10 repetitive responses to a given calibration or span gas, must be 
no greater than <plus-minus>1 percent of full scale concentration for 
each range used above 155 parts per million (ppm) or parts per million 
equivalent carbon (ppmC) or <plus-minus>2 percent of each range used 
below 155 ppm (or ppmC).
    (iii) The analyzer peak to peak response to zero and calibration or 
span gases over any 10 second period shall not exceed 2 percent of full 
scale on all ranges used.
    (iv) The analyzer zero drift during a 1-hour period shall be less 
than 2 percent of full scale on the lowest range used. The zero-response 
is the mean response, including noise, to a zero gas during a 30-second 
time interval.
    (v) The analyzer span drift during a 1-hour period shall be less 
than 2 percent of full scale on the lowest range used. The analyzer span 
is defined as the difference between the span response and the zero 
response. The span response is the mean response, including noise, to a 
span gas during a 30-second time interval.
    (11) CO and CO<INF>2</INF> analyzer specifications. (i) Measurements 
shall be made with nondispersive infrared (NDIR) analyzers.
    (ii) For the CO analyzer, the water and CO<INF>2</INF> interference 
shall be less than 1 percent of full scale for ranges equal to or 
greater than 300 ppm (3 ppm for ranges below 300 ppm) when a 
CO<INF>2</INF> span gas concentration of 80 percent to 100 percent of 
full scale of the maximum operating range used during testing is bubbled 
through water at room temperature.
    (12) For NO<INF>X</INF> analysis using a chemiluminescence (CL) 
analyzer the following parameters shall apply:
    (i) From the sample point to the NO<INF>2</INF> to NO converter, the 
NO<INF>X</INF> sample shall be maintained between 131  deg.F (55  deg.C) 
and 392  deg.F (200  deg.C).
    (ii) The NO<INF>2</INF> to NO converter efficiency shall be at least 
90 percent.
    (iii) The quench interference from CO<INF>2</INF> and water vapor 
must be less than 3.0 percent.
    (13) For NO<INF>X</INF> analysis using an NDIR analyzer system the 
following parameters shall apply:
    (i) The system shall include a NO<INF>2</INF> to NO converter, a 
water trap, and a NDIR analyzer.
    (ii) From the sample point to the NO<INF>2</INF> to NO converter, 
the NO<INF>X</INF> sample shall be maintained between 131  deg.F (55 
deg.C) and 392  deg.F (200  deg.C).
    (iii) The minimum water rejection ratio (maximum water interference)

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for the NO<INF>X</INF> NDIR analyzer shall be 5,000:1.
    (iv) The minimum CO<INF>2</INF> rejection ratio (maximum 
CO<INF>2</INF> interference) for the NO<INF>X</INF> NDIR analyzer shall 
be 30,000:1.
    (14) When CH<INF>4</INF> is measured using a heated flame ionization 
detector (HFID) the following shall apply:
    (i) The analyzer shall be equipped with a constant temperature oven 
that houses the detector and sample-handling components.
    (ii) The detector, oven, and sample-handling components shall be 
suitable for continuous operation at temperatures of 374  deg.F (190 
deg.C) <plus-minus> 18  deg.F (10  deg.C).
    (iii) The analyzer fuel shall contain 40 <plus-minus> 2 percent 
hydrogen. The balance shall be helium. The mixture shall contain 
<ls-thn-eq> 1 part per million equivalent carbon (ppmC), and <ls-thn-eq> 
400 ppm CO.
    (iv) The burner air shall contain  2 ppmC hydrocarbon.
    (v) The percent of oxygen interference shall be less than 5 percent.
    (15) An NDIR analyzer for measuring CH<INF>4</INF> may be used in 
place of the HFID specified in paragraph (b)(14) of this section and 
shall conform to the requirements of paragraph (b)(10) of this section. 
Methane measurements shall be made on a dry basis.
    (16) Calibration gas values shall be traceable to the National 
Institute for Standards and Testing (NIST), ``Standard Reference 
Materials'' (SRM's). The analytical accuracy of the calibration gas 
values shall be within 2.0 percent of NIST gas standards.
    (17) Span gas values shall be traceable to NIST SRM's. The 
analytical accuracy of the span gas values shall be within 2.0 percent 
of NIST gas standards.
    (18) Calibration or span gases for the CO and CO<INF>2</INF> 
analyzers shall have purified nitrogen as a diluent. Calibration or span 
gases for the CH<INF>4</INF> analyzer shall be CH<INF>4</INF> with 
purified synthetic air or purified nitrogen as diluent.
    (19) Calibration or span gases for the NO<INF>X</INF> analyzer shall 
be NO with a maximum NO<INF>2</INF> concentration of 5 percent of the NO 
content. Purified nitrogen shall be the diluent.
    (20) Zero-grade gases for the CO, CO<INF>2</INF>, CH<INF>4</INF> , 
and NO<INF>X</INF> analyzers shall be either purified synthetic air or 
purified nitrogen.
    (21) The allowable zero-grade gas (purified synthetic air or 
purified nitrogen) impurity concentrations shall not exceed <ls-thn-eq> 
1ppm C, <ls-thn-eq> 1 ppm CO, <ls-thn-eq> 400 ppm CO<INF>2</INF>, and 
<ls-thn-eq> 0.1 ppm NO.
    (22) The calibration and span gases may also be obtained by means of 
a gas divider. The accuracy of the mixing device must be such that the 
concentration of the diluted calibration gases are within 2 percent.
    (c) Particulate sampling system shall be used in determining the 
particulate index. A schematic of a full flow (single dilution) 
particulate sampling system for testing under this subpart is shown in 
Figures E-3 and E-4.
    (1) The dilution system shall meet the following parameters:
    (i) Either a positive displacement pump (PDP) or a critical flow 
venturi (CFV) shall be used as the pump/mass measurement device shown in 
Figure E-3.
    (ii) The total volume of the mixture of exhaust and dilution air 
shall be measured.
    (iii) All parts of the system from the exhaust pipe up to the filter 
holder, which are in contact with raw and diluted exhaust gas, shall be 
designed to minimize deposition or alteration of the particulate.
    (iv) All parts shall be made of electrically conductive materials 
that do not react with exhaust gas components.
    (v) All parts shall be electrically grounded to prevent 
electrostatic effects.
    (vi) Systems other than full flow systems may also be used provided 
they yield equivalent results where:
    (A) A seven sample pair (or larger) correlation study between the 
system under consideration and a full flow dilution system shall be run 
concurrently.
    (B) Correlation testing is to be performed at the same laboratory, 
test cell, and on the same engine.
    (C) The equivalency criterion is defined as a <plus-minus> 5 percent 
agreement of the sample pair averages.
    (2) The mass of particulate in the exhaust shall be collected by 
filtration. The exhaust temperature immediately before the primary 
particulate filter shall not exceed 125  deg.F (52.0  deg.C).

[[Page 37]]

    (3) Exhaust system backpressure shall not be artificially lowered by 
the PDP, CFV systems or dilution air inlet system. Static exhaust 
backpressure measured with the PDP or CFV system operating shall remain 
within <plus-minus> 0.44 inches Hg (1.5 kPa) of the static pressure 
measured without being connected to the PDP or CFV at identical engine 
speed and load.
    (4) The gas mixture temperature shall be measured at a point 
immediately ahead of the pump or mass measurement device.
    (i) Using PDP, the gas mixture temperature shall be maintained 
within <plus-minus> 10  deg.F (6.0  deg.C) of the average operating 
temperature observed during the test, when no flow compensation is used.
    (ii) Flow compensation can be used provided that the temperature at 
the inlet to the PDP does not exceed 122  deg.F (50  deg.C).
    (iii) Using CFV, the gas mixture temperature shall be maintained 
within <plus-minus> 20  deg.F (11  deg.C) of the average operating 
temperature observed during the test, when no flow compensation is used.
    (5) The heat exchanger shall be of sufficient capacity to maintain 
the temperature within the limits required above and is optional if 
electronic flow compensation is used.
    (6) When the temperature at the inlet of either the PDP or CFV 
exceeds the limits stated in either paragraphs (c)(4)(i) or (c)(4)(iii) 
of this section, an electronic flow compensation system shall be 
required for continuous measurement of the flow rate and control of the 
proportional sampling in the particulate sampling system.
    (7) The flow capacity of the system shall be large enough to 
eliminate water condensation.

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[GRAPHIC] [TIFF OMITTED] TR25OC96.002


[[Page 39]]


[GRAPHIC] [TIFF OMITTED] TR25OC96.003

    (8) The flow capacity of the PDP or CFV system using single dilution 
shall maintain the diluted exhaust at 125  deg.F (52.0  deg.C) or less 
immediately before the primary particulate filter.
    (9) The flow capacity of the PDP or CFV system using a double 
dilution

[[Page 40]]

system shall be sufficient to maintain the diluted exhaust in the 
dilution tunnel at 375  deg.F (191  deg.C) or less at the sampling zone.
    (10) The secondary dilution system shall provide sufficient 
secondary dilution air to maintain the double-diluted exhaust stream at 
125  deg.F (52.0  deg.C) or less immediately before the primary 
particulate filter.
    (11) The gas flow meters or the mass flow measurement 
instrumentation shall have a maximum error of the measured value within 
<plus-minus>2 percent of reading.
    (12) The dilution air shall have a temperature of 77 
deg.F<plus-minus>9  deg.F (25  deg.C<plus-minus>5  deg.C), and be--
    (i) Filtered at the air inlet; or
    (ii) Sampled to determine background particulate levels, which can 
then be subtracted from the values measured in the exhaust stream.
    (13) The dilution tunnel shall have the following specifications:
    (i) Be small enough in diameter to cause turbulent flow (Reynolds 
number greater than 4,000) and of sufficient length to cause complete 
mixing of the exhaust and dilution air;
    (ii) Be at least 3 inches (75 mm) in diameter; and
    (iii) Be configured to direct the engine exhaust downstream at the 
point where it is introduced into the dilution tunnel for thorough 
mixing.
    (14) The exhaust pipe length from the exit of the engine exhaust 
manifold or turbocharger outlet to the dilution tunnel shall not exceed 
a total length of 32 feet (10 m).
    (i) When the exhaust pipe exceeds 12 feet (4 m), then all pipe in 
excess of 12 feet (4 m) shall be insulated with a radial thickness of at 
least 1.0 inch (25 mm) and the thermal conductivity of the insulating 
material shall be no greater than 0.1 W/mK measured at 752  deg.F (400 
deg.C).
    (ii) To reduce the thermal inertia of the exhaust pipe, the 
thickness to diameter ratio shall be 0.015 or less.
    (iii) The use of flexible sections shall be limited to the length to 
diameter ratio of 12 or less.
    (15) The particulate sample probe shall--
    (i) Be installed in the dilution tunnel facing upstream, on the 
dilution tunnel centerline, and approximately 10 dilution tunnel 
diameters downstream of the point where the engine's exhaust enters the 
dilution tunnel; and
    (ii) Have 0.5 inches (12 mm) minimum inside diameter.
    (16) The inlet gas temperature to the particulate sample pump or 
mass measurement device shall remain a constant temperature of 
<plus-minus>5  deg.F (3.0  deg.C) if flow compensation is not used.
    (17) The secondary dilution portion of the double dilution system 
shall have:
    (i) A particulate transfer tube shall have a 0.5 inch (12 mm) 
minimum inside diameter not to exceed 40 inches (1020 mm) in length 
measured from the probe tip to the secondary dilution tunnel has:
    (A) An inlet with the transfer tube facing upstream in the primary 
dilution tunnel, centerline, and approximately 10 dilution tunnel 
diameters downstream of the point where the engine's exhaust enters the 
dilution tunnel.
    (B) An outlet where the transfer tube exits on the centerline of the 
secondary tunnel and points downstream.
    (ii) A secondary tunnel that has a minimum diameter of 3.0 inches 
(75 mm), and of sufficient length to provide a residence time of at 
least 0.25 seconds for the double-diluted sample.
    (iii) Secondary dilution air supplied at a temperature of 77  deg.F 
<plus-minus> 9  deg.F(25  deg.C<plus-minus>5  deg.C).
    (iv) A primary filter holder located within 12.0 inches (300 mm) of 
the exit of the secondary tunnel.
    (18) The particulate sampling filters shall--
    (i) Be fluorocarbon-coated glass fiber filters or fluorocarbon-based 
(membrane) filters and have a 0.3 <greek-m>m di-octylphthalate (DOP) 
collection efficiency of at least 95 percent at a gas face velocity 
between 35 and 80 cm/s.;
    (ii) Have a minimum diameter of 1.85 inches (47 mm), 1.46 inches (37 
mm) stain diameter;
    (iii) Have a minimum filter loading ratio of 0.5mg/1075 mm \2\ stain 
area for the single filter method.
    (iv) Have minimum filter loading such that the sum of all eight (8) 
multiple filters is equal to the minimum loading value (mg) for a single 
filter

[[Page 41]]

multiplied by the square root of eight (8).
    (v) Be sampled at the same time by a pair of filters in series (one 
primary and one backup filter) so that:
    (A) The backup filter holder shall be located no more than 4 inches 
(100 mm) downstream of the primary filter holder.
    (B) The primary and backup filters shall not be in contact with each 
other.
    (C) The filters may be weighed separately or as a pair with the 
filters placed stain side to stain side.
    (D) The single filter method incorporates a bypass system for 
passing the sample through the filters at the desired time.
    (vi) Have a pressure drop increase between the beginning and end of 
the test of no more than 7.4 in Hg (25kPa).
    (vii) Filters of identical quality shall be used when performing 
correlation tests specified in paragraph (c)(1)(vi) of this section.
    (19) Weighing chamber specifications. (i) The temperature of the 
chamber (room) in which the particulate filters are conditioned and 
weighed shall be maintained to within 72  deg.F<plus-minus>5  deg.F (22 
deg.C<plus-minus>3  deg.C) during all filter conditioning and weighing.
    (ii) The humidity of the chamber (room) in which the particulate 
filters are conditioned and weighed shall be maintained to a dewpoint of 
49  deg.F<plus-minus>5  deg.F (9.5  deg.C<plus-minus>3  deg.C) and a 
relative humidity of 45 percent <plus-minus>8 percent during all filter 
conditioning and weighing.
    (iii) The chamber (room) environment shall be free of any ambient 
contaminants (such as dust) that would settle on the particulate filters 
during their stabilization. This shall be determined as follows:
    (A) At least two unused reference filters or reference filter pairs 
shall be weighed within four (4) hours of, but preferably at the same 
time as the sample filter (pair) weighings.
    (B) The reference filters are to be the same size and material as 
the sample filters.
    (C) If the average weight of reference filters (reference filter 
pairs) changes between sample filter weighings by more than 
<plus-minus>5.0 percent (<plus-minus>7.5 percent for the filter pair 
respectively) of the recommended minimum filter loading in paragraphs 
(c)(18)(iii) or (c)(18)(iv) of this section, then all sample filters 
shall be discarded and the tests repeated.
    (20) The analytical balance used to determine the weights of all 
filters shall have a precision (standard deviation) of 20 <greek-m>g and 
resolution of 10 <greek-m>g. For filters less than 70 mm diameter, the 
precision and resolution shall be 2 <greek-m>g and 1 <greek-m>g, 
respectively.
    (21) All filters shall be neutralized to eliminate the effects of 
static electricity prior to weighing.

Sec. 7.87  Test to determine the maximum fuel-air ratio.

    (a) Test procedure. (1) Couple the diesel engine to the dynamometer 
and connect the sampling and measurement devices specified in Sec. 7.86.
    (2) Prior to testing, zero and span the CO and NO<INF>X</INF> 
analyzers to the lowest analyzer range that will be used during this 
test.
    (3) While running the engine, the following shall apply:
    (i) The parameter for the laboratory atmospheric factor, 
f<INF>a</INF>, shall be: 0.98<ls-thn-eq>f<INF>a</INF><ls-thn-eq>1.02;
    (A) The equation is f<INF>a</INF>=(99/P<INF>s</INF>) * 
((T<INF>a</INF>+273)/298)<SUP>0.7</SUP> for a naturally aspirated and 
mechanically supercharged engines; or
    (B) The equation is f<INF>a</INF>=(99/P<INF>s</INF>)<SUP>0.7</SUP>* 
((T<INF>a</INF>+273)/298) <SUP>1.5</SUP> for a turbocharged engine with 
or without cooling of the intake air.

    Where:
    P<INF>s</INF> = dry atmospheric pressure (kPa)
    T<INF>a</INF> = intake air temperature ( deg.C)
    (ii) The air inlet restriction shall be set within <plus-minus>10 
percent of the recommended maximum air inlet restriction as specified by 
the engine manufacturer at the engine operating condition giving maximum 
air flow to determine the concentration of CO as specified in paragraph 
(a)(6) of this section.
    (iii) The exhaust backpressure restriction shall be set within 
<plus-minus>10 percent of the maximum exhaust backpressure as specified 
by the engine manufacturer at the engine operating condition giving 
maximum rated horsepower to determine the concentrations of CO and 
NO<INF>X</INF> as specified in paragraph (a)(6)of this section.

[[Page 42]]

    (iv) The air inlet restriction shall be set within <plus-minus>10 
percent of a recommended clean air filter at the engine operating 
condition giving maximum air flow as specified by the engine 
manufacturer to determine the concentration of NO<INF>X</INF> as 
specified in paragraph (a)(6) of this section.
    (4) The engine shall be at a steady-state condition when the exhaust 
gas samples are collected and other test data is measured.
    (5) In a category A engine, 1.0<plus-minus>0.1 percent 
CH<INF>4</INF> shall be injected into the engine's intake air.
    (6) Operate the engine at several speed/torque conditions to 
determine the concentrations of CO and NO<INF>X</INF>, dry basis, in the 
raw exhaust.
    (b) Acceptable performance. The CO and NO<INF>X</INF> concentrations 
in the raw exhaust shall not exceed the limits specified in Sec. 7.84(b) 
throughout the specified operational range of the engine.

Sec. 7.88  Test to determine the gaseous ventilation rate.

    The test shall be performed in the order listed in Table E-2. The 
test for determination of the particulate index described in Sec. 7.89 
may be done simultaneously with this test.
    (a) Test procedure. (1) Couple the diesel engine to the dynamometer 
and attach the sampling and measurement devices specified in Sec. 7.86.
    (2) A minimum time of 10 minutes is required for each test mode.
    (3) CO, CO<INF>2</INF>, NO<INF>X</INF>, and CH<INF>4</INF> analyzers 
shall be zeroed and spanned at the analyzer range to be used prior to 
testing.
    (4) Run the engine.
    (i) The parameter for f<INF>a</INF> shall be calculated in 
accordance with Sec. 7.87(a)(3).
    (ii) The air inlet and exhaust backpressure restrictions on the 
engine shall be set as specified in Secs. 7.87(a)(3) (iii) and (iv).
    (5) The engine shall be at a steady-state condition before starting 
the test modes.
    (i) The output from the gas analyzers shall be measured and recorded 
with exhaust gas flowing through the analyzers a minimum of the last 
three (3) minutes of each mode.
    (ii) To evaluate the gaseous emissions, the last 60 seconds of each 
mode shall be averaged.
    (iii) A 1.0<plus-minus>0.1 percent CH<INF>4</INF>, by volume, shall 
be injected into the engine's intake air for category A engines.
    (iv) The engine speed and torque shall be measured and recorded at 
each test mode.
    (v) The data required for use in the gaseous ventilation 
calculations specified in paragraph (a)(9) of this section shall be 
measured and recorded at each test mode.
    (6) Operate the engine at each rated speed and horsepower rating 
requested by the applicant according to Table E-2 in order to measure 
the raw exhaust gas concentration, dry basis, of CO, CO<INF>2</INF>, NO, 
and NO<INF>2</INF>, and CH<INF>4</INF>- exhaust (category A engines 
only).
    (i) Test speeds shall be maintained within <plus-minus>1 percent of 
rated speed or <plus-minus>3 RPM, which ever is greater, except for low 
idle which shall be within the tolerances established by the 
manufacturer.
    (ii) The specified torque shall be held so that the average over the 
period during which the measurements are taken is within <plus-minus>2 
percent of the maximum torque at the test speed.
    (7) The concentration of CH<INF>4</INF> in the intake air shall be 
measured for category A engines.

                                          Table E-2--Gaseous Test Modes
-------------------------------------------------------------------------------
---------------------------------
                      Speed                                 Rated speed        
     Intermediate speed     Low-
-------------------------------------------------------------------------------
--------------------------  idle
                                                                               
                            speed
                    % Torque                        100     75      50      10 
     100     75      50   -------
                                                                               
                              0

-------------------------------------------------------------------------------
---------------------------------

    (8) After completion of the test modes, the following shall be done:
    (i) Zero and span the analyzers at the ranges used during the test.

[[Page 43]]

    (ii) The gaseous emission test shall be acceptable if the difference 
in the zero and span results taken before the test and after the test 
are less than 2 percent.
    (9) The gaseous ventilation rate for each exhaust gas contaminant 
shall be calculated as follows--
    (i) The following abbreviations shall apply to both category A and 
category B engine calculations as appropriate:

cfm--Cubic feet per min (ft<SUP>3</SUP>/min)
Exh--Exhaust
A--Air (lbs/hr)
H--Grains of water per lb. of dry intake air
J--Conversion factor
m--Mass flow rate (mass/hr)
TI--Intake air temperature ( deg.F)
PCAir--Percent Air
PCCH<INF>4</INF>--Percent CH<INF>4</INF> (intake air)
UCH<INF>4</INF>--Unburned CH<INF>4</INF>
PCECH<INF>4</INF>--Percent Exhaust CH<INF>4</INF>

    (ii) Exhaust gas flow calculation for category B engines shall be (m 
Exh)=(A)+(m fuel).
    (iii) Fuel/air ratio for category B engines shall be (f/a)=(m fuel) 
/ (A).
    (iv) Methane flow through category A engines shall be determined by 
the following:

PCAir=100-PCCH<INF>4</INF>
Y=(PCAir)(0.289)+(PCCH<INF>4</INF>)(0.16)
Z=(0.16)(PCCH<INF>4</INF>)<divide>Y
mCH<INF>4</INF>=(A)(Z)<divide>(1-Z)

    (v) Exhaust gas flow calculation for category A engines shall be (m 
Exh)=(A)+(m fuel)+(m CH<INF>4</INF>)
    (vi) Unburned CH<INF>4</INF> (lbs/hr) calculation for category A 
engines shall be mUCH<INF>4</INF>=(m Exh)(0.0052)(PCECH<INF>4</INF>)
    (vii) Fuel/air ratio for category A engines shall be (f/a)=((m 
fuel)+(m CH<INF>4</INF>)-(m UCH<INF>4</INF>))<divide>(A)
    (viii) Conversion from dry to wet basis for both category A and 
category B engines shall be:

(NO wet basis)=(NO dry basis)(J)
(NO<INF>2</INF> wet basis)=(NO<INF>2</INF> dry basis)(J)
(CO<INF>2</INF> wet basis)=(CO<INF>2</INF> dry basis)(J)
(CO wet basis)=(CO dry basis)(10<SUP>-4</SUP>)(J)

Where:

J=(f/a)(-1.87)+(1-(0.00022)(H))

    (ix) NO and NO<INF>2</INF> correction for humidity and temperature 
for category A and category B engines shall be:

(NO corr)=(NO wet basis)<divide>(E)
(NO<INF>2</INF> corr)=(NO<INF>2</INF> wet basis)<divide>(E)

Where:

E=1.0+(R)(H-75)+(G)(TI-77)
R=(f/a)(0.044)-(0.0038)
G=(f/a)(-0.116)+(0.0053)

    (x) The calculations to determine the m of each exhaust gas 
contaminant in grams per hour at each test point shall be as follows for 
category A and category B engines:

(m NO)=(NO corr)(0.000470)(m Exh)
(m NO<INF>2</INF>)=(NO<INF>2</INF> corr)(0.000720)(m Exh)
(m CO<INF>2</INF>)=(CO<INF>2</INF> wet basis)(6.89)(m Exh)
(m CO)=(CO wet basis)(4.38)(m Exh)

    (xi) The calculations to determine the ventilation rate for each 
exhaust gas contaminant at each test point shall be as follows for 
category A and category B engines:

(cfm NO)=(m NO)(K)
(cfm NO<INF>2</INF>)=(m NO<INF>2</INF>)(K)
(cfm CO<INF>2</INF>)=(m CO<INF>2</INF>)(K)
(cfm CO)=(m CO)(K)

Where:

K=13,913.4/ (pollutant grams/mole) (pollutant dilution value specified 
          in Sec. 7.84(c)).

    (b) The gaseous ventilation rate for each requested rated speed and 
horsepower shall be the highest ventilation rate calculated in paragraph 
(a)(9)(xi) of this section.
    (1) Ventilation rates less than 20,000 cfm shall be rounded up to 
the next 500 cfm.
    Example: 10,432 cfm shall be listed 10,500 cfm.
    (2) Ventilation rates greater than 20,000 cfm shall be rounded up to 
the next 1,000 cfm.
    Example: 26,382 cfm shall be listed 27,000 cfm.

[61 FR 55504, Oct. 25, 1996; 62 FR 34640, June 27, 1997]

Sec. 7.89  Test to determine the particulate index.

    The test shall be performed in the order listed in Table E-3.
    (a) Test procedure. (1) Couple the diesel engine to the dynamometer 
and connect the sampling and measurement devices specified in Sec. 7.86.
    (2) A minimum time of 10 minutes is required for each measuring 
point.
    (3) Prior to testing, condition and weigh the particulate filters as 
follows:
    (i) At least 1 hour before the test, each filter (pair) shall be 
placed in a

[[Page 44]]

closed, but unsealed, petri dish and placed in a weighing chamber (room) 
for stabilization.
    (ii) At the end of the stabilization period, each filter (pair) 
shall be weighed. The reading is the tare weight.
    (iii) The filter (pair) shall then be stored in a closed petri dish 
or a filter holder, both of which shall remain in the weighing chamber 
(room) until needed for testing.
    (iv) The filter (pair) must be re-weighed if not used within 8 hours 
of its removal from the weighing chamber (room).
    (4) Run the engine.
    (i) The parameter for f<INF>a</INF> shall be calculated in 
accordance with Sec. 7.87(a)(3).
    (ii) The air inlet and exhaust backpressure restrictions on the 
engine shall be set as specified in Secs. 7.87(a)(3) (iii) and (iv).
    (iii) The dilution air shall be set to obtain a maximum filter face 
temperature of 125  deg.F (52  deg.C) or less at each test mode.
    (iv) The total dilution ratio shall not be less than 4.
    (5) The engine shall be at a steady state condition before starting 
the test modes.
    (i) The engine speed and torque shall be measured and recorded at 
each test mode.
    (ii) The data required for use in the particulate index calculation 
specified in paragraph (a)(9) of this section shall be measured and 
recorded at each test mode.
    (6) A 1.0<plus-minus>0.1 percent CH<INF>4</INF>, by volume shall be 
injected into the engine's intake air for category A engines.
    (7) Operate the engine at each rated speed and horsepower rating 
requested by the applicant according to Table E-3 to collect particulate 
on the primary filter.
    (i) One pair of single filters shall be collected or eight multiple 
filter pairs shall be collected.
    (ii) Particulate sampling shall be started after the engine has 
reached a steady-state condition.
    (iii) The sampling time required per mode shall be either a minimum 
of 20 seconds for the single filter method or a minimum of 60 seconds 
for the multiple filter method.
    (iv) The minimum particulate loading specified in Secs. 7.86(c)(18) 
(iii) or (iv) shall be done.

                                        Table E-3--Particulate Test Modes
-------------------------------------------------------------------------------
---------------------------------
                      Speed                                 Rated speed        
     Intermediate speed     Low-
-------------------------------------------------------------------------------
--------------------------  idle
                                                                               
                            speed
                    % Torque                        100     75      50      10 
     100     75      50   -------
                                                                               
                              0
-------------------------------------------------------------------------------
---------------------------------
Weighting factor................................    0.15    0.15    0.15     0.
1     0.1     0.1     0.1    0.15
-------------------------------------------------------------------------------
---------------------------------

    (v) Test speeds shall be maintained within <plus-minus> percent of 
rated speed or <plus-minus>3 RPM, which ever is greater, except for low 
idle which shall be within the tolerances set by the manufacturer.
    (vi) The specified torque shall be held so that the average over the 
period during which the measurements are being taken is within 
<plus-minus>2 percent of the maximum torque at the test speed.
    (vii) The modal weighting factors (WF) given in Table E-3 shall be 
applied to the multiple filter method during the calculations as shown 
in paragraph (a)(9)(iii)(B) of this section.
    (viii) For the single filter method, the modal WF shall be taken 
into account during sampling by taking a sample proportional to the 
exhaust mass flow for each mode of the cycle.
    (8) After completion of the test, condition and weigh the 
particulate filters in the weighing chamber (room) as follows:
    (i) Condition the filters for at least 1 hour, but not more than 80 
hours.
    (ii) At the end of the stabilization period, weigh each filter. The 
reading is the gross weight.
    (iii) The particulate mass of each filter is its gross weight minus 
its tare weight.
    (iv) The particulate mass (P<INF>F</INF> for the single filter 
method; P<INF>F</INF>,<INF>i</INF> for the multiple filter method) is 
the sum of the

[[Page 45]]

particulate masses collected on the primary and back-up filters.
    (v) The test is void and must be rerun if the sample on the filter 
contacts the petri dish or any other surface.
    (9) The particulate index for the mass particulate shall be 
calculated from the equations listed below--
    (i) The following abbreviations shall be:

cfm--Cubic feet per min (ft\3\ min)
PT--Particulate (gr/hr)
m mix--Diluted exhaust gas mass flow rate on wet basis (kg/hr)
m sample--Mass of the diluted exhaust sample passed through the 
          particulate sampling filters (kg)
P<INF>f</INF>--Particulate sample mass collected on a filter (mg) at 
          each test mode as determined in Table E-3.
K<INF>p</INF>--Humidity correction factor for particulate
WF--Weighting factor
i-Subscript denoting an individual mode, i=1, . . . n
PI--Particulate Index (cfm)

    (ii) When calculating ambient humidity correction for the 
particulate concentration (P<INF>f</INF> part), the equation shall be:

P<INF>fcorr</INF>=(P<INF>f</INF>)(K<INF>p</INF>)
K<INF>p</INF>=1/(1+0.0133 * (H-10.71))

Where:

H<INF>a</INF>=humidity of the intake air, g water per kg dry air
H<INF>a</INF>=(6.220 * R<INF>a</INF> * p<INF>a</INF>)/
          (p<INF>B</INF>-p<INF>a</INF> - R<INF>a</INF> * 
          10<SUP>-2</SUP>)
R<INF>a</INF>=relative humidity of the intake air, %
p<INF>a</INF>=saturation vapor pressure of the intake air, kPa
p<INF>B</INF>=total barometric pressure, kPa

    (iii) When the multiple filter method is used, the following 
equations shall be used.
    (A) Mass of particulate emitted is calculated as follows:
    [GRAPHIC] [TIFF OMITTED] TR25OC96.004
    
(B) Determination of weighted particulate average is calculated as 
follows:
[GRAPHIC] [TIFF OMITTED] TR25OC96.005

(C) Determination of particulate index for the mass particulate from the 
average of the test modes shall be calculated as follows:
[GRAPHIC] [TIFF OMITTED] TR25OC96.006

(iv) When the single filter method is used, the following equations 
shall be used.
(A) Mass of particulate emitted:
[GRAPHIC] [TIFF OMITTED] TR25OC96.007

Where:
[GRAPHIC] [TIFF OMITTED] TR25OC96.008

[GRAPHIC] [TIFF OMITTED] TR25OC96.009

(B) Determination of particulate index for the mass particulate from the 
average of the test modes shall be as follows:

[[Page 46]]

[GRAPHIC] [TIFF OMITTED] TR25OC96.010

(v) When the effective weighting factor, WF<INF>E</INF>,<INF>i</INF>, 
for each mode is calculated for the single filter method, the following 
shall apply.
[GRAPHIC] [TIFF OMITTED] TR25OC96.011

(B) The value of the effective weighting factors shall be within 
<plus-minus>0.005 (absolute value) of the weighting factors listed in 
Table E-3.
    (b) A particulate index for each requested rated speed and 
horsepower shall be the value determined in paragraph (a)(9)(iii)(C) of 
this section for the multiple filter method or paragraph (a)(9)(iv)(B) 
of this section for the single filter method.
    (1) Particulate indices less than 20,000 cfm shall be rounded up to 
the next 500 cfm. Example: 10,432 cfm shall be listed 10,500 cfm.
    (2) Particulate indices greater than 20,000 cfm shall be rounded up 
to the nearest thousand 1,000 cfm. Example: 26,382 cfm shall be listed 
27,000 cfm.

[61 FR 55504, Oct. 25, 1996; 62 FR 34640, June 27, 1997]

Sec. 7.90  Approval marking.

    Each approved diesel engine shall be identified by a legible and 
permanent approval marking inscribed with the assigned MSHA approval 
number and securely attached to the diesel engine. The marking shall 
also contain the following information:
    (a) Ventilation rate.
    (b) Rated power.
    (c) Rated speed.
    (d) High idle.
    (e) Maximum altitude before deration.
    (f) Engine model number.

Sec. 7.91  Post-approval product audit.

    Upon request by MSHA, but no more than once a year except for cause, 
the approval holder shall make a diesel engine available for audit at no 
cost to MSHA.

Sec. 7.92  New technology.

    MSHA may approve a diesel engine that incorporates technology for 
which the requirements of this subpart are not applicable if MSHA 
determines that the diesel engine is as safe as those which meet the 
requirements of this subpart.
