Federal Motor Vehicle Safety Standards: Air Brake Systems

Topics:  National Highway Traffic Safety Administration, Federal Motor Vehicle Safety Standards

L. Robert Shelton
Federal Register
March 26, 1998

[Federal Register: March 26, 1998 (Volume 63, Number 58)]
[Proposed Rules]               
[Page 14674-14675]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr26mr98-36]


[[Page 14674]]

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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. NHTSA-98-3650]
RIN 2127-AF72

 
Federal Motor Vehicle Safety Standards: Air Brake Systems

AGENCY: National Highway Traffic Safety Administration (NHTSA), 
Department of Transportation (DOT).

ACTION: Termination of proposed rulemaking.

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SUMMARY: This notice terminates a rulemaking action in which NHTSA 
proposed amending the Federal motor vehicle safety standard that 
establishes requirements for vehicles equipped with air brake systems. 
The proposed amendment would have required that trucks, buses, and 
truck tractors be equipped with an automatic means of removing moisture 
and other contaminants from air brake systems, and would have deleted 
the current requirement for a supply reservoir since the reservoir's 
function would be performed by the automatic system. Moisture and 
contaminants can cause valves to stick, thereby preventing sufficient 
air pressure from being delivered to the brake chambers.
    NHTSA is terminating this rulemaking action because the agency has 
decided that it should address this issue through more broadly worded 
performance requirements that would give manufacturers flexibility to 
choose the type of air cleaning and drying system appropriate for their 
new air-braked vehicles. The agency will continue to study the issue 
with a view to initiate a future rulemaking proceeding for regulating 
the performance of methods for cleansing and drying the compressed air 
that supplies air brake systems.

FOR FURTHER INFORMATION CONTACT:
    For technical issues: Joseph P. Scott, Safety Standards Engineer, 
Office of Crash Avoidance Standards, National Highway Traffic Safety 
Administration, 400 Seventh Street SW, Washington, DC 20590; telephone 
(202) 366-2720; FAX (202) 493-2739.
    For legal issues: Walter Myers, Office of the Chief Counsel, 
National Highway Traffic Safety Administration, 400 Seventh Street SW, 
Washington, DC 20590; telephone (202) 366-2992; FAX (202) 366-3820.

SUPPLEMENTARY INFORMATION:

Background

    Federal Motor Vehicle Safety Standard (Standard) No. 121, Air Brake 
Systems, specifies braking performance requirements for vehicles 
equipped with air brake systems. The standard requires such vehicles to 
be equipped with, among other things, a ``condensate drain valve that 
can be manually operated'' (paragraph S5.1.2.4 for trucks and buses and 
paragraph S5.2.1.3 for trailers). Such valve allows contaminants such 
as water, oil, and dirt to be drained from the brake system's 
reservoirs.
    On July 28, 1994, Domenic F. Coletta, M.D., Deputy Medical Examiner 
of Salem County, New Jersey, submitted a petition for rulemaking to 
amend Standard 121 to require a condensate drain valve that 
automatically purges moisture and contaminants from the air supply 
reservoir. Dr. Coletta stated in his petition that currently available 
automatic drain valves would better ensure safety because reservoirs 
equipped with manual drain valves are usually not drained on a regular 
basis by vehicle drivers. He argued, therefore, that contaminants are 
present in reservoirs, thus creating unsafe conditions for operation of 
trucks and buses. He cited conversations with truck drivers and New 
Jersey state police to the effect that manual drain valves are normally 
not used to remove contaminants from the reservoirs. He supplied no 
data, however, on the extent to which requiring automatic drain valves 
could be expected to enhance motor vehicle safety.
    On February 21, 1995, NHTSA granted Dr. Coletta's petition and, on 
July 24, 1995, issued a request for comments seeking data on automatic 
drain valves and the effects contaminants in air brake systems before 
proceeding to rulemaking (60 FR 37864).
    The agency received 34 responses to the request for comments from 
vehicle and equipment manufacturers, industry trade associations, a 
safety advocacy group, fleet and individual truck operators, a U.S. 
senator, and numerous private citizens. In general, the manufacturers 
and trade associations stated that a Federal requirement was not 
necessary, that the current use of air dryers and the trend toward 
their widespread use was sufficient to maintain a safe level of 
performance. Several commenters stated that they had no record of any 
crashes caused by contaminated air in the brake system. The commenters 
were split, however, on whether contaminated air constituted a 
significant safety problem in an air brake system.
    Based on a thorough review of the comments, NHTSA published a 
Notice of Proposed Rulemaking (NPRM) on November 4, 1996 (61 FR 56652), 
proposing to amend Standard 121 to require that each truck, bus, and 
truck tractor be equipped with an automatic means of removing moisture 
and contaminants from its air brake system. The purpose of this 
proposal was to improve the safety of air-braked vehicles by improving 
the reliability and durability of ABS modulator valves and pneumatic 
control valves. The NPRM also proposed the deletion of the requirement 
for a supply reservoir since its function, the removal of moisture and 
contaminants, would be accomplished by the addition of such automatic 
means. Accordingly, NHTSA believed that the deletion of the supply 
reservoir would not adversely affect the safety of those vehicles. It 
is worth noting that S5.1.2 of Standard No. 121 provides the option of 
removing moisture and contaminants by using either a supply reservoir 
or a service reservoir(s) with automatic drain valves.
    The agency received 26 comments on the NPRM, the majority of which 
(17 of 26) supported the proposal to mandate a means of automatically 
removing moisture and contaminants from air brake systems. Others 
supported the use of such devices, but opposed mandating them.

Agency Decision

    The agency estimates that approximately 80 to 90 percent of new 
truck tractors and 75 percent of new single-unit trucks are now being 
equipped with some type of air moisture/contaminant removal system.
    There are 3 basic removal systems which currently can be used on 
new trucks, tractors and buses equipped with air brakes: automatic 
drain valves, supply reservoirs (wet tank), and air dryers. Each system 
has its advantages and disadvantages, as follows:
    a. Automatic drain valve. (1) Advantages. This is the simplest 
system for ensuring a clean and dry air brake system. It purges most of 
the contamination in the supply reservoir, thus preventing 
contamination from entering the service reservoirs and pneumatic drain 
valves farther downstream. Since drivers and maintenance personnel may 
not drain the reservoirs on a daily basis as they should, an automatic 
drain valve will systematically drain the reservoirs without the need 
for human intervention. Automatic drain valves on each reservoir could 
ensure a cleaner air brake system, especially in light of the 
requirements for ABS.

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    (2) Disadvantages. Automatic drain valves can become clogged and 
frozen, resulting in the danger of the valve sticking open or closed. 
Particularly in the southwestern United States, an automatic drain 
valve would add costs without providing any significant benefits. 
Unlike air dryers, such valves do not provide any significant dew point 
reduction. Thus, the air in the brake system could still retain 
sufficient moisture to degrade the pneumatic valves.
    b. Supply reservoir (wet tank). (1) Advantages. The supply 
reservoir or wet tank provides a means of collecting moisture and 
contaminants before they enter the air brake system, thereby acting as 
a buffer between the compressor and the service reservoirs. The supply 
reservoir traps most of the condensate and contaminants before they 
reach the service reservoirs and provides a backup for desiccant-type 
dryers in the event of failure.1
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    \1\ In a typical desiccant-style system, the incoming air is 
routed into the bottom end of an air dryer where a large portion of 
the moisture and contaminants falls to the bottom. The partially 
cleaned air then passes through an oil separator. The air, still 
moist, then is passed through a drying bed of desiccant material (a 
substance, such as calcium oxide, used as a drying agent) that 
absorbs the remaining moisture. These dryers are equipped with an 
automatic drain valve that periodically purges moisture and 
contaminants from the air system.
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    (2) Disadvantages. The presence of the wet tank complicates the air 
system and reduces the amount of compressed air available for the 
emergency brake system.
    c. Air Dryer. (1) Advantages. Air dryers with an integrated 
condensate drain valve are currently the most effective method of 
removing moisture and other contaminants from an air brake system. Air 
dryers also provide some filtration of the compressed air by removing 
some oils and contaminants from the air. Automatic drain valves do not 
provide any dew point reduction, while air dryers can provide a 10 deg. 
to 20 deg. Fahrenheit reduction. This is important because moisture can 
still be present even with automatic drain valves installed in the 
system.
    (2) Disadvantages. Air dryers can fail, and can increase the 
application times for service and parking brakes. Further, air dryers 
could place an unnecessary cost burden on some operators and fleets, 
such as those operating in the southwestern United States, where 
humidity is low and there is less need for air dryers.
    After much consideration and analysis of this issue, NHTSA now 
believes that it should address this issue through more broadly worded 
performance requirements that would give manufacturers flexibility to 
choose the type of air cleaning and drying system appropriate for their 
new air-braked vehicles. However, the agency is not yet ready to 
propose such requirements. Accordingly, NHTSA is terminating this 
rulemaking action.
    The agency's goal throughout its consideration of these issues has 
been, and remains, ensuring the removal of moisture and contaminants 
from air brake systems by improving the reliability and durability of 
ABS and associated modular valves and pneumatic control valves. To that 
end, the agency is actively working with the Society of Automotive 
Engineers (SAE) to establish an SAE Recommended Practice and associated 
test procedures for air drying and cleansing equipment used in air 
brake systems. These procedures would be valuable for testing the vast 
majority of new heavy trucks. NHTSA estimates that, currently, over 80 
percent of new air-braked heavy trucks are being built with air dryers 
and of those, more than 90 percent are the desiccant type dryers. 
Regardless of the results of SAE's efforts, however, NHTSA intends to 
propose performance requirements for the removal of moisture and 
contaminants from air brake systems, and provide comprehensive test 
procedures to measure that performance.
    Meanwhile, the agency notes that paragraph S5.1.2 of Standard 121 
requires that manufacturers provide ``either an automatic condensate 
drain valve for each service reservoir or a supply reservoir between 
the service reservoir system and the source of air pressure.'' This 
will assure that trucks and buses equipped with air brakes will have a 
means of moisture/contaminant removal adequate to maintain the safety 
of such systems. Completion of the SAE studies is estimated to be in 
the fall of 1998.
    For the reasons stated above, NHTSA is terminating this rulemaking 
action.

    Authority: 49 U.S.C. Secs. 322, 30111, 30115, 30117, and 30166; 
delegation of authority at 49 CFR 1.50.

    Issued on March 20, 1998.
L. Robert Shelton,
Associate Administrator for Safety Performance Standards.
[FR Doc. 98-7910 Filed 3-25-98; 8:45 am]
BILLING CODE 4910-59-P