Federal Motor Vehicle Safety Standards; Air Brake Systems Control Line Pressure Balance |
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Topics: Federal Motor Vehicle Safety Standards
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Patricia P. Breslin
National Highway Traffic Safety Administration
July 13, 1994
[Federal Register: July 13, 1994]
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DEPARTMENT OF TRANSPORTATION
49 CFR Part 571
[Docket No. 85-07; Notice 9]
RIN 2127-AF23
Federal Motor Vehicle Safety Standards; Air Brake Systems Control
Line Pressure Balance
AGENCY: National Highway Traffic Safety Administration (NHTSA),
Department of Transportation.
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: In response to a petition for rulemaking submitted by Sealco
Air Controls, Inc., this notice proposes to amend the control line
pressure differential requirements in Standard No. 121, Air Brake
Systems, for converter dollies and trailers designed to tow another
vehicle equipped with air brakes. The agency has tentatively concluded
that the proposed amendments would improve the braking compatibility of
such vehicles by allowing the use of a relay valve known as a spool-
type low opening valve. The agency does not anticipate any adverse
safety consequences resulting from amending the pressure differential
requirements.
DATES: Comments. Comments must be received on or before September 12,
1994.
Proposed effective date. The proposed amendments in this notice
would become effective 30 days after publication of a final rule in the
Federal Register.
ADDRESSES: Comments should refer to the docket and notice numbers above
and be submitted to: Docket Section, National Highway Traffic Safety
Administration, 400 Seventh Street, S.W., Washington, D.C. 20590.
Docket hours are 9:30 a.m. to 4 p.m., Monday through Friday.
FOR FURTHER INFORMATION CONTACT: Mr. Chris Tinto, Office of Vehicle
Safety Standards, National Highway Traffic Safety Administration, 400
Seventh Street, S.W., Washington, D.C. 20590. (202-366-6761).
SUPPLEMENTARY INFORMATION: Standard No. 121, Air Brake Systems,
establishes performance and equipment requirements for braking systems
on vehicles equipped with air brakes, including requirements for
pneumatic timing. For purposes of compliance testing, the pneumatic
timing tests for trailers, including trailer converter dollies, are
conducted with the trailer connected to a test rig rather than an
actual tractor. The test rig delivers air to, and releases air from,
the trailer during the timing test. The timing tests for vehicles
designed to tow trailers are conducted with a 50 cubic inch reservoir
connected to rear control line coupling. This reservoir represents the
control line volume of the control trailer used in the compliance
testing.
On August 21, 1992, NHTSA published a final rule amending the
pneumatic timing requirements of Standard No. 121 with respect to the
control signal pressure balance for tractor trailer combinations. (57
FR 37902). The agency added S5.3.5 which specifies a new test procedure
for determining the control line pressure differential in converter
dollies and trailers designed to tow another trailer equipped with air
brakes. Specifically, the rule requires that the pressure differential
between the control line input coupling and a 50 cubic inch test
reservoir shall not exceed 1 psi at all input pressures between 5 psi
and 20 psi and 2 psi at all input pressures greater than 20 psi. Agency
research indicates that input pressures below 20 psi represent routine
braking applications, input pressures between 20 psi and 40 psi
represent moderate to heavy braking applications, and input pressures
above 40 psi represent severe braking applications. As explained below,
NHTSA is proposing to modify the limit above 40 psi to allow a 5
percent differential (which at higher pressures exceeds the current
limit of 2 psi) based on the Society of Automotive Engineer's (SAE's)
Recommended Practice SAE J1505, Brake Force Distribution Test Code
Commercial Vehicles.
The agency explained that the amendment is designed to ensure that
the control signal ``passes'' through a towing trailer or dolly without
being altered along the way. Since the control signal passes through
unaltered, each vehicle in a combination unit receives the same brake
control signal. This serves to increase the braking compatibility of
combination vehicles since each vehicle in a combination has comparable
braking performance.
Sealco Petition
On June 18, 1993, Sealco Air Controls, Inc. (Sealco), a valve
manufacturer, submitted to NHTSA a rulemaking petition to amend
Standard No. 121 with respect to the control line pressure differential
requirements in S5.3.5. Specifically, it requested that NHTSA amend
these requirements to permit the manufacture of its low opening valves
that serve to adjust air flow in control lines. These valves are used
as control line relay valves and service line relay valves in trailers
and converter dollies. The petitioner stated that unlike other relay
valves that use a common poppet,1 the low opening valves have a
balanced spool technology2 that incorporates a low pressure at
which the valve initially opens (i.e., crack pressure) of 1.5 psi.
According to Sealco, the spool technology enables the valve to track
closer between the input control air pressure and the output delivered
air pressure. As a result, it claimed that hysteresis3 is not so
prevalent with low operating valves as with the high crack pressure
poppet design valves.
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\1\ A rising and falling valve consisting of a disc at the end
of a vertically set stem.
\2\ A valve whose primary means of diverting pressure or flow is
through movement of a cylindrical valve mechanism along its axis.
\3\ The time lag in a system in reacting to changes in the
forces affecting it. With respect to braking, the relay valve's
output (apply pressure) lags more than a few psi behind ascending
control line (treadle) pressure, and stays more than one or two psi
above descending control line pressure. Complications may arise when
a second brake application is made before the first one is fully
released.
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Hysteresis in a valve may cause the valve not to track (i.e.,
follow closely) the control line pressure properly, which may cause the
brakes in the trailer to lag behind the control signal. For example,
when the driver applies the brakes, the valve's hysteresis may not
allow the same pressure to be applied to the trailer brakes, which will
cause less braking in the trailer and cause the trailer to ``push'' the
tractor. Similarly, when the driver releases the brake, the hysteresis
in the valve may not allow the brakes in the trailer to be released
quickly enough and will still have the brakes applied while the driver
is trying to accelerate, causing the kingpin to jerk on the inside of
the fifth wheel. On more extreme conditions where the driver goes
through several fast brake applications and releases in rapid
succession, the jerking and pushing of the trailer or trailers could be
difficult to control.
Sealco stated that the use of low operating valves would further
NHTSA's goal of ensuring balanced braking in combination vehicles.
However, the petitioner claimed that while its valve meets the
amendment's application requirements, it does not meet the provision
requiring release at high pressure ranges, given the valve's mechanics.
To comply with the amendment, Sealco has drilled a hole in the valves'
piston, thereby allowing pressure to bleed to the supply side. This
action prevents the valves from cracking open when tested according to
S5.3.5. Sealco believes that this modification to allow compliance with
the amendment has reduced the valves' effectiveness. Sealco also
criticized the test procedure which it believed did not simulate actual
braking conditions. It stated that slow and fast ascending and
descending control line pressures should be used to check the valves'
ability to respond appropriately.
Agency's Decision To Issue Proposal
After reviewing the petition, NHTSA has decided to propose an
amendment to Standard No. 121 to permit the use of low operating
valves. Specifically, the agency is proposing to amend S5.3.5 to
account for input pressures over 40 psi. Under the proposal, the
pressure differential would not be permitted to exceed 2 psi at any
input pressure between 20 psi and 40 psi and it would not be permitted
to exceed 5 percent at any pressure over 40 psi. In other words, the
pressure differential requirements would remain the same, except for
applications resulting in pressures over 40 psi. The agency requests
comments about whether the modification to pressure levels over 40 psi
is appropriate.
NHTSA is proposing the value of 40 psi based on SAE J1505, Brake
Force Distribution Test Code Commercial Vehicles. The agency has
tentatively determined that the safety problem addressed by the
requirement in S5.3.5, i.e., slow heat build up and brake fade caused
by long gradual down hill runs at relatively low air pressure, is not a
problem for severe brake applications over 40 psi. In formulating this
proposal, NHTSA contacted all the major valve manufacturers. Other than
Sealco, no other valve manufacturer stated that they had to drill holes
in the valve or otherwise modify the valve in a way that might
adversely affect their real-world dynamic braking performance in order
to comply with the test in S5.3.5. Aside from Sealco, the valve
manufacturers believed that the existing test was a realistic,
reasonable assessment of low pressure differential performance.
NHTSA has tentatively determined that this amendment would
facilitate the use of spool valve technology, while not being
detrimental to safety. The agency's primary concern in these
rulemakings addressing control line pressure differentials is brake
performance in the low end of the air pressure range since the vast
majority of stopping occurs there. Specifically, in the August 1992
rule, the agency sought to improve low end brake performance with
respect to slow heat build up and brake fading brought about by
relatively low brake applications during long gradual downhill
descents.
After further review, the agency now believes that the current
requirement may unnecessarily extend the 2 psi requirement into the
higher pressure ranges where it is not necessary for safety. As noted
above, the requirement is designed to prevent brake fade during
relatively low brake applications below 20 psi and is not applicable to
hard brake applications, i.e., those exceeding 40 psi. Accordingly, the
agency has tentatively decided to modify the differential requirements
at levels over 40 psi. Notwithstanding the agency's tentative
conclusion, the agency request comments about whether this amendment
poses any risk of adverse safety consequences.
However, NHTSA disagrees with Sealco's statements that the test
procedure in S5.3.5 does not simulate actual braking conditions. The
agency notes that this test procedure was based on the agency's own
testing and extensive test data and recommendations by trailer
manufacturers in response to previous agency proposals. Specifically,
the agency disagrees with Sealco's statement that ``Slow and fast
ascending and descending control line pressures should be used to check
CLV performance.'' As discussed in earlier notices, NHTSA sought
pressure rises and decays that were neither too fast nor too slow. As
trailer manufacturers and other commenters to the earlier proposal
stated, if the pressure rise were too slow, test personnel would waste
time waiting for the event to occur, and if the pressure rise were too
rapid, pressure differentials could not be read quickly enough. In
addition, pressure surges from a fast rate would likely result in a
loss of normal valve hysteresis and subsequent errors in crack pressure
readings. Accordingly, the agency believes that the test accurately
evaluates real-world dynamic braking without creating any significant
negative safety effects.
Rulemaking Analyses and Notices
1. Executive Order 12866 (Federal Regulatory Planning and Review) and
DOT Regulatory Policies and Procedures
This proposal was not reviewed under E.O. 12866. NHTSA has analyzed
this proposal and determined that it is not ``significant'' within the
meaning of the Department of Transportation's regulatory policies and
procedures. A full regulatory evaluation is not required because the
rule, if adopted, would have no mandatory effects. Instead, the
proposal would permit spool valve technology. Therefore, this
rulemaking would not have any cost impacts.
2. Regulatory Flexibility Act
In accordance with the Regulatory Flexibility Act, NHTSA has
evaluated the effects of this action on small entities. Based upon this
evaluation, I certify that the proposed amendment would not have a
significant economic impact on a substantial number of small entities.
Vehicle and brake manufacturers typically would not qualify as small
entities. This amendment would affect small businesses, small
organizations, and small governmental units to the extent that these
entities purchase vehicles. However, this amendment would not have any
cost impact on vehicles. For these reasons, vehicle manufacturers,
small businesses, small organizations, and small governmental units
which purchase motor vehicles would not be significantly affected by
the proposed requirements. Accordingly, no regulatory flexibility
analysis has been prepared.
3. Executive Order 12612 (Federalism)
This action has been analyzed in accordance with the principles and
criteria contained in Executive Order 12612, and it has been determined
that the proposed rule would not have sufficient Federalism
implications to warrant preparation of a Federalism Assessment. No
State laws would be affected.
4. National Environmental Policy Act
Finally, the agency has considered the environmental implications
of this proposed rule in accordance with the National Environmental
Policy Act of 1969 and determined that the proposed rule would not
significantly affect the human environment.
5. Civil Justice Reform
This proposed rule would not have any retroactive effect. Under
section 103(d) of the National Traffic and Motor Vehicle Safety Act (49
U.S.C. 30111), whenever a Federal motor vehicle safety standard is in
effect, a state may not adopt or maintain a safety standard applicable
to the same aspect of performance which is not identical to the Federal
standard. Section 105 of the Act (49 U.S.C. 30161) sets forth a
procedure for judicial review of final rules establishing, amending or
revoking Federal motor vehicle safety standards. That section does not
require submission of a petition for reconsideration or other
administrative proceedings before parties may file suit in court.
Public Comments
Interested persons are invited to submit comments on the proposal.
It is requested but not required that 10 copies be submitted.
All comments must not exceed 15 pages in length. (49 CFR 553.21).
Necessary attachments may be appended to these submissions without
regard to the 15-page limit. This limitation is intended to encourage
commenters to detail their primary arguments in a concise fashion.
If a commenter wishes to submit certain information under a claim
of confidentiality, three copies of the complete submission, including
purportedly confidential business information, should be submitted to
the Chief Counsel, NHTSA, at the street address given above, and seven
copies from which the purportedly confidential information has been
deleted should be submitted to the Docket Section. A request for
confidentiality should be accompanied by a cover letter setting forth
the information specified in the agency's confidential business
information regulation. 49 CFR Part 512.
All comments received before the close of business on the comment
closing date indicated above for the proposal will be considered, and
will be available for examination in the docket at the above address
both before and after that date. To the extent possible, comments filed
after the closing date will also be considered. Comments received too
late for consideration in regard to the final rule will be considered
as suggestions for further rulemaking action. The NHTSA will continue
to file relevant information as it becomes available in the docket
after the closing date, and it is recommended that interested persons
continue to examine the docket for new material.
Those persons desiring to be notified upon receipt of their
comments in the rules docket should enclose a self-addressed, stamped
postcard in the envelope with their comments. Upon receiving the
comments, the docket supervisor will return the postcard by mail.
List of Subjects in 49 CFR Part 571
Imports, Motor vehicle safety, Motor vehicles, Rubber and rubber
products, Tires.
In consideration of the foregoing, the agency proposes to amend 49
CFR Part 571 as follows:
PART 571--[AMENDED]
1. The authority citation for Part 571 would be revised to read as
follows:
Authority: 49 U.S.C. 322, 30111, 30115, 30117, and 30166;
delegation of authority at 49 CFR 1.50.
2. In Sec. 571.121, S5.3.5 introductory text and S5.3.5(a) would be
revised to read as follows:
Sec. 571.121 Standard No. 121; Air brake systems.
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S5.3. Control signal pressure differential--converter dollies and
trailers designed to tow another vehicle equipped with air brakes.
(a) For a trailer designed to tow another vehicle equipped with air
brakes, the pressure differential between the control line input
coupling and a 50 cubic inch test reservoir attached to the control
line output coupling shall not exceed the values specified in S5.3.5(a)
(1) and (2) under the conditions specified in S5.3.5(b) (1) through
(4)--
(1) 1 p.s.i. at all input pressures equal to or greater than 20
p.s.i., but not greater than 20 p.s.i.; and
(2) 2 p.s.i. at all input pressures from 20 p.s.i. to 40 p.s.i.;
and
(3) not more than a 5 percent differential at any input pressures
above 40 p.s.i.
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Issued on July 6, 1994.
Patricia P. Breslin,
Acting Associate Administrator for Rulemaking.
[FR Doc. 94-16913 Filed 7-12-94; 8:45 am]
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