§ 169.7. Equipment and instrumentation.
The following equipment and instruments shall be used for smoke emissions and service simulation tests:
(1) An engine dynamometer with adequate characteristics to perform the tests required by the provisions of § 169.5 (relating to smoke test cycle).
(2) Provide an exhaust system of proper diameter and suitable length for the engine being tested, with provisions for mounting the smoke opacimeter. Test data show that a range of length 4 to 20 feet (1.2 to 6.1 meters) does not change the meter reading. In the case of short exhaust systems, the opacimeter may be affected by the high temperature. The system shall be capable of being adjusted to meet the exhaust back pressure required to comply with the provisions of § 169.4 (relating to smoke emission test). Install a 2 foot (610 millimeters) section of smooth circular pipe, free of elbows and bends, prior to the smoke opacimeter location. If an opacimeter which mounts at the end of the exhaust system is used, the optical unit of the opacimeter shall be mounted radially to the exhaust pipe so that the measurement will be made at right angles to the axis of the exhaust plume. The opacimeter shall be located at the termination of the exhaust stack with the light beam of the opacimeter just clearing the stack termination point. The full flow of the exhaust stream shall be centered between the source and detector apertures, or windows and lenses, and on the axis of the light beam. If a muffler is needed, a conventional automotive muffler of a size and type commonly used with the engine may be installed in this system.
(3) Mount a full-flow, light-extinction, smoke opacimeter in or on the exhaust system at the location specified in paragraph (2). When dual exhaust systems are used, both systems shall be equipped with a smoke opacimeter measuring an exhaust stream of (127 millimeters) diameter or larger.
(4) Smoke opacity and engine speed shall be monitored continuously, using a strip chart recorder or equivalent, with a minimum speed range of .5—15 inches per minute (13—381 millimeters per minute), and a maximum full-scale response time for smoke opacity of .5 second. (Response time for 95% to 100% of full-scale within .5 second). The reading shall stabilize at 100% within 1 second. An automatic marker indicating 1 second intervals to verify chart speed is desirable.
(5) The various components, opacimeter, electronic filters and recorder, should comprise a system capable of data output within the following limits:
(i) The smoke opacity trace shall be linear when calibrated to read from zero to 100% (full-scale). The trace should have a resolution within 1% of full-scale reading.
(ii) The engine speed trace shall be linear when calibrated to read from the low idle speed to rated engine speed. The trace should have a resolution within 1% of rated engine speed.
(iii) The chart speed used to record smoke opacity shall provide a time resolution of at least .25 second.
(6) The use of general instrumentation for measuring engine speed, power, fuel rate, inlet air restriction, exhaust back pressure, inlet air temperature and humidity, barometric pressures and such pressures and temperatures while performing tests required in this chapter should not affect the recorded smoke opacity.
(7) A separate low-pass electronic filter with the following performance characteristics may be installed between the smoke opacimeter and the recorder to achieve high frequency attenuations:
(i) Three decibels point—10 hertz.
(ii) Insertion loss—zero, plus or minus .5 decibel.
(iii) Selectivity—12 decibels per octave above 10 hertz.
(iii) Attenuation—27 decibels down at 40 hertz minimum.
Source The provisions of this § 169.7 adopted August 26, 1977, effective August 27, 1977, 7 Pa.B. 2432.
Cross References This section cited in 67 Pa. Code § 169.4 (relating to smoke emission test).
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