[Code of Federal Regulations]
[Title 40, Volume 18]
[Revised as of July 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR92.116]
[Page 443-445]
TITLE 40--PROTECTION OF ENVIRONMENT
CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
PART 92--CONTROL OF AIR POLLUTION FROM LOCOMOTIVES AND LOCOMOTIVE ENGINES--
Table of Contents
Subpart B--Test Procedures
Sec. 92.116 Engine output measurement system calibrations.
(a) General requirements for dynamometer calibration. (1) The engine
flywheel torque and engine speed measurement transducers shall be
calibrated with the calibration equipment described in this section.
(2) The engine flywheel torque feedback signals to the cycle
verification equipment shall be electronically checked before each test,
and adjusted as necessary.
(3) Other engine dynamometer system calibrations shall be performed
as dictated by good engineering practice.
(4) When calibrating the engine flywheel torque transducer, any
lever arm used to convert a weight or a force through a distance into a
torque shall be used in a horizontal position (5 degrees).
(5) Calibrated resistors may not be used for engine flywheel torque
transducer calibration, but may be used to span the transducer prior to
engine testing.
(b) Dynamometer calibration equipment--(1) Torque calibration
equipment. Two techniques are allowed for torque calibration. Alternate
techniques may be used if shown to yield equivalent accuracies. The NIST
``true'' value torque is defined as the torque calculated by taking the
product of an NIST traceable weight or force and a sufficiently accurate
horizontal lever arm distance, corrected for the hanging torque of the
lever arm.
(i) The lever-arm dead-weight technique involves the placement of
known weights at a known horizontal distance from the center of rotation
of the
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torque measuring device. The equipment required is:
(A) Calibration weights. A minimum of six calibration weights for
each range of torque measuring device used are required. The weights
must be approximately equally spaced and each must be traceable to NIST
weights within 0.1 percent. Laboratories located in foreign countries
may certify calibration weights to local government bureau standards.
Certification of weight by state government Bureau of Weights and
Measures is acceptable. Effects of changes in gravitational constant at
the test site may be accounted for if desired.
(B) Lever arm. A lever arm with a minimum length of 24 inches is
required. The horizontal distance from the centerline of the engine
torque measurement device to the point of weight application shall be
accurate to within 0.10 inches. The arm must be balanced, or
the hanging torque of the arm must be known to within 0.1
ft-lbs.
(ii) The transfer technique involves the calibration of a master
load cell (i.e., dynamometer case load cell). This calibration can be
done with known calibration weights at known horizontal distances, or by
using a hydraulically actuated precalibrated master load cell. This
calibration is then transferred to the flywheel torque measuring device.
The technique involves the following steps:
(A) A master load cell shall be either precalibrated or be
calibrated per paragraph (b)(1)(i)(A) of this section with known weights
traceable to NIST within 0.1 percent, and used with the lever arm(s)
specified in this section. The dynamometer should be either running or
vibrated during this calibration to minimize static hysteresis.
(B) Transfer of calibration from the case or master load cell to the
flywheel torque measuring device shall be performed with the dynamometer
operating at a constant speed. The flywheel torque measurement device
readout shall be calibrated to the master load cell torque readout at a
minimum of six loads approximately equally spaced across the full useful
ranges of both measurement devices. (Note that good engineering practice
requires that both devices have approximately equal useful ranges of
torque measurement.) The transfer calibration shall be performed in a
manner such that the accuracy requirements of Sec. 92.106(b)(1)(ii) for
the flywheel torque measurement device readout be met or exceeded.
(iii) Other techniques may be used if shown to yield equivalent
accuracy.
(2) Speed calibration equipment. A 60 (or greater) tooth wheel in
combination with a common mode rejection frequency counter is considered
an absolute standard for engine or dynamometer speed.
(c) Dynamometer calibration. (1) If necessary, follow the
manufacturer's instructions for initial start-up and basic operating
adjustments.
(2) Check the dynamometer torque measurement for each range used by
the following:
(i) Warm up the dynamometer following the equipment manufacturer's
specifications.
(ii) Determine the dynamometer calibration moment arm. Equipment
manufacturer's data, actual measurement, or the value recorded from the
previous calibration used for this subpart may be used.
(iii) Calculate the indicated torque (IT) for each calibration
weight to be used by:
IT=calibration weight (lb)xcalibration moment arm (ft)
(iv) Attach each calibration weight specified in paragraph
(b)(1)(i)(A) of this section to the moment arm at the calibration
distance determined in paragraph (b)(2)(ii)(B) of this section. Record
the power measurement equipment response (ft-lb) to each weight.
(v) For each calibration weight, compare the torque value measured
in paragraph (b)(2)(iv) of this section to the calculated torque
determined in paragraph (b)(2)(iii) of this section.
(vi) The measured torque must be within 2 percent of the calculated
torque.
(vii) If the measured torque is not within 2 percent of the
calculated torque, adjust or repair the system. Repeat the steps in
paragraphs (b)(2)(i) through (b)(2)(vi) of this section with the
adjusted or repaired system.
[[Page 445]]
(3) Option. A master load-cell or transfer standard may be used to
verify the in-use torque measurement system.
(i) The master load-cell and read out system must be calibrated with
weights at each test weight specified in paragraph (b)(1)(i)(A) of this
section. The calibration weights must be traceable to within 0.1 percent
of NIST weights.
(ii) Warm up the dynamometer following the equipment manufacturer's
specifications.
(iii) Attach the master load-cell and loading system.
(iv) Load the dynamometer to a minimum of 6 equally spaced torque
values as indicated by the master load-cell for each in-use range used.
(v) The in-use torque measurement must be within 2 percent of the
torque measured by the master system for each load used.
(vi) If the in-use torque is not within 2 percent of the master
torque, adjust or repair the system. Repeat steps in paragraphs
(b)(3)(ii) through (b)(3)(vi) of this section with the adjusted or
repaired system.
(4) The dynamometer calibration must be completed within 2 hours
from the completion of the dynamometer warm-up.
(d) Electrical load banks. Equipment used to measure the electrical
power output dissipated by electrical load banks shall be calibrated as
frequently as required by Sec. 92.115, using a calibration procedure
that is consistent with good engineering practice and approved by the
Administrator.