Feature Article
Maintenance Feature on Refrigerated Trailers written
by Richard Stewart for Truckers News.
Big Rig BasicsKeeping Your Cool
Refrigerated equipment demands proper maintenance
and close attention to spot potential trouble.BY RICHARD STEWART
Photos by Richard StewartThe potential for loss is high in refrigerated hauling. When a reefer
system fails on the road, emergency repairs might not come in time
to save the load of perishable food or other valuable temperature-
controlled cargo on board. Surprisingly, this sophisticated cooling
unit is the most neglected piece of equipment on a refrigerated
trailer. That's because reefers are so reliable and operator-friendly
that they can give drivers a false sense of security. Properly
maintained, they rarely fail.Periodic servicing, cleaning of coils, and frequent visual checks
are required for trouble-free reefer operation. Be on the lookout
for low coolant or oil levels, dirty oil, slack or worn belts, signs of
leaks, frayed electrical wires, loose nuts and bolts, restricted vents,
blocked defrost drains, and corrosive buildup on the battery
terminals. Be aware of how much fuel is in the reefer's tank to
avoid running dry and having to bleed air from the fuel system to
restart it.The successful reefer operator also keeps his ears tuned to the
sounds that the system makes to detect unusual noises that might
indicate servicing is needed. This kind of close attention to the
refrigeration system is the best insurance against expensive
shippers' claims of spoilage due to reefer unit malfunction or
failure. It also helps extend the service life of the unit and ensures
good trade-in or resale value.How Reefers Work
Transport refrigeration systems are designed to maintain
temperature within a few degrees of the set point by cooling/
heating air and recirculating it over, under and around the load.
Core refrigeration technologies include heat transfer, compression,
air management and electronics. Microprocessors and other
electronic components monitor and control the cycling of the
system to hold the set temperatures.The heart of the system is the compressor. Powered by a small
diesel engine (9 hp to 35 hp), the compressor pumps refrigerant
to the condenser and evaporator coils to remove heat from the
air passing through, lowering its temperature. If warm air is
required to adjust the temperature, the compressor heats the
refrigerant by compressing it, and the evaporator is by-passed.
A defrost cycle eliminates ice buildup on the evaporator coil by
automatically switching from refrigeration to defrost. Reducing
the accumulation of ice keeps air moving efficiently over the coil.A fan recirculates the conditioned air back into the trailer through
a fabric chute attached to the ceiling that directs the air at the rear
door. Remote evaporators can be installed inside separate
compartments in the trailer to enable multi-temperature hauling
even of both fresh and frozen commodities at the same time.Carrier Transicold and Thermo King are the giants of transport
refrigeration. Both manufacturers maintain extensive dealer service
networks and offer a full range of products, from standard to high-
capacity units. A reefer's capacity is rated in British thermal
units/hour (Btuh), indicating the amount of heat the unit can
remove from the air in an hour based on ambient (outside) air
temperature of 100 degrees Fahrenheit.Ratings are given at several established cooling temperatures.
The capacity of a standard-performance trailer refrigeration unit
is 16,000 to 17,000 Btuh at minus-20, which is the temperature
at which deep-frozen food is typically maintained. Higher-rated
refrigeration units cool air faster. For example, a high-capacity
reefer set at minus 20 can remove 30,000 Btu of heat in an hour,
nearly twice as much as a standard unit.Capacities are also given for temperatures of 0 degrees and 35
degrees. High-capacity reefers not only provide faster pulldown
of temperature to the desired cooling setpoint; they also provide
faster temperature recovery after door openings and better fuel
economy, since the unit doesn't have to work as hard to maintain
box temperatures in hot climates.What Can You Do?
Having the unit serviced professionally at the recommended
interval is very important, emphasizes Rick Coffman, Service
Manager, Sunbelt Transport Refrigeration, Ltd., the Carrier
dealer in Tampa, Fla. But short of working on the refrigeration
components, which is best left to certified technicians, the reefer
operator can perform most preventive maintenance and some
repairs himself between services to keep the system running at
peak efficiency.“Breakdowns can be minimized just by routine maintenance and
visual inspections of everything,” says Coffman. He recommends
that drivers keep a supply of spare parts and hand tools in the
truck. “When we do a service and change the belts, we give the
old belts to the customer to keep on hand in case of an
emergency.” Diagrams on the door indicate how to install and
adjust the belts. He also suggests carrying spare filters for the
reefer's diesel. The same engine oil and coolant used in the truck
or tractor's main engine can also be used in the smaller powerplant.Coffman advises drivers not to attempt repairs to the refrigeration
system, particularly not out on the side of the road. “One thing a
reefer system can't stand is contamination, especially dirt and
moisture.” Getting air in the system also spells trouble, since air is
difficult to compress, he notes. Coffman recommends having the
reefer serviced every 1,000 hours, which typically includes an oil
and filter change.The standard preventive maintenance interval in the industry is
1,500 hours. Oil and filters are typically changed as part of the
PM service, but many drivers prefer to do their own engine oil
service. Using synthetic oil can extend the oil-change interval to
3,000 and even 4,000 hours on certain engines. Air filters should
be changed at least once a year, more often if the reefer operates
in damp conditions or in cold winter temperatures over wet, salty
roads. Moisture is the air cleaner's worst enemy.Both Carrier and Thermo King dealers sell remanufactured
replacement parts that are warranted and perform to original
equipment standards at much less cost than new parts. Thermo
King offers an extensive list of products, including “The Whole
Shebang,” a complete kit of parts needed to overhaul a compressor.Thermo King also sells a kit to convert refrigerant from the old
R-12 to the more environmentally acceptable and less expensive
R-401B. Converting TK units to R-401B can increase the reefer's
value and save money, says the company. Even using only 60 lbs.
of refrigerant a year would save more than $1,000 annually, more
than enough to pay for the cost of the conversion kits, according to
Thermo King.The company markets the Smart Cycle Sentry to add “smarts” to
older TK units with the Cycle Sentry feature. Equipped with the
new electronic module, the reefer will start automatically when in
null cycle to charge the battery when needed. It provides a low-fuel
shutdown, stopping the unit when it senses a drop in engine RPMs
to avoid running out of fuel. Smart Cycle Sentry also provides a
second attempt to start the engine if the first fails for added protection
of unattended units.Thermo King offers a rolling curtain wall that is designed to help
maintain the set-point temperature inside trucks and trailers despite
frequent door openings. The curtain mounts to the ceiling of the box
and is rolled forward as cargo is loaded or unloaded, reducing the
area that requires refrigeration. Another product, a remote controller
that mounts inside the box, enables the operator to control the unit
without leaving the dock.Dealer Provides Service
Both Thermo King and Carrier recommend that their units be
serviced by a dealer at the designated intervals. During a basic
service, a technician performs a series of checks to evaluate the
unit's condition and makes any needed adjustments. Belts are
inspected for proper tension and tightened to spec if needed. Worn
belts are replaced. Air and fuel filters are checked and replaced
if need be. The fuel-tank sediment bowl is drained and cleaned
along with the fuel transfer pump strainer.“We put a set of gauges on the unit to check the refrigeration
system and make sure it has plenty of refrigerant and that it isn't
leaking,” says Coffman. “If the condenser is clogged up with bugs
and debris, we blow it all out with dry nitrogen,” he explains,
noting the the unit is not pressure-washed because that can pack
the bugs and dirt into the condenser.” Dry nitrogen is relatively
inexpensive and effective for cleaning coils and in other places
where debris can accumulate. The dealership buys dry nitrogen
in 3000-psi cylinders and uses a regulator to reduce the pressure
to about 300 psi.“You need to make sure the condenser is clean, otherwise it will
lessen the efficiency of the unit by not getting the required heat
transfer,” adds Coffman. If a reefer has been sitting for an
extended period, it's a good idea to check for bird's nests inside
the unit before operating it. The nest material should be removed
completely so it doesn't get sucked into the radiator or get wound
around the belts and create a fire hazard.Dealer servicing includes checking inside the trailer to make sure
that the front bulkhead is in good condition and that the air chute
isn't torn or hanging down. “The chute can get ripped by forklift
operators during loading and unloading. We repair it and refasten
it to the ceiling and bulkhead,” he relates, noting that a torn or
hanging chute allows air to escape out the side, degrading
efficiency by not delivering the full volume of supply air to the
rear of the trailer.“The supply air that comes out of the unit is colder than the
return air. If the operator is hauling any kind of delicate product
such as strawberries, he stands the chance of top-freezing at the
point where the chute is damaged,” Coffman relates. He advises
drivers to pay attention to the condition of the air chute and to
repair any damage.During the dealer PM service, the unit is run through a pre-trip
inspection and the box is cooled to test all modes of operation.
The valves, relays and switches are checked along with the
system's components. (See sidebar for a complete list of service
items that are performed during a basic service.) The cost of
service depends on the dealer's labor rate, but typically it ranges
between $150 and $200 and takes about two hours.Loading the Reefer
Drivers should pay close attention during loading and should
not assume that the people doing the loading are paying enough
attention to do the job right, says Coffman. Space for air to
circulate throughout the load must be provided whether the
cargo is palletized or stacked on the floor. Tiered stacking of
boxes, leaving alternating air spaces in each row, is the
recommended method. Packing boxes tightly against the
sidewalls and above the load lines, too close to the ceiling,
must be avoided.Adequate space also needs to be left between the load and
the front wall and rear door. That allows the supply air coming
down the chute to hit the door, then flow in, around and
underneath the load, along the ribbed floor and back to the
reefer unit as return air. Before loading, the trailer should be
swept or hosed out to remove any dirt, shrink wrap and other
debris that can block the return air stream, he advises. “The
driver needs to get in there and inspect the load and make
sure there is enough return air capability to get back to the unit.”Performing a pre-trip inspection to make sure the unit is
operating properly is one of the most important tasks of the
reefer operator, says Andy Widay, Service Program Manager,
Carrier Transicold. “If the unit has a problem and the driver
doesn't find out about it until after the product is loaded and on
the road, it can become a very expensive problem,” he notes.
“Nothing should by-pass a very good pre-trip prior to loading.”Carrier's Advance® microprocessor control system
incorporates a pre-trip inspection feature that performs 15
critical tests, including a pump down, in about eight minutes,
says Widay. The Advance system displays alarms, instructions
and other messages in plain language rather than number codes.
It provides over 150 specific alarm messages in clear detail,
which facilitates routine maintenance, troubleshooting and repair,
according to the company.Thermo King reefers feature the Thermoguard® microprocessor,
which runs self-diagnostics, displays messages and alarms, and
performs a complete operational pre-trip of components and
functions in less than 20 minutes. The set point and return air
temperatures are displayed during normal operation.Checking the Temp
Prime Inc., a Springfield, Mo.-based reefer fleet with some
2,400 refrigerated trailers, performs its own maintenance,
servicing reefer units every 1,500 hours. The company runs
Thermo King units in Great Dane Thermocube® trailers.
Prime technicians are certified to handle refrigerant, which
must be carefully stored and accounted for.Drivers are expected to take the pulp temperature of
products before they are loaded by inserting a thermometer
into the product or the packaging. “The critical thing is to
confirm that the product being loaded has been stabilized or
brought to the temp that it's supposed to be,” says Les Hazen,
Prime's Director of Maintenance, who is also responsible for
the company's Operator Road Assist group. He advises
drivers to carry a durable pocket thermometer (Digital models
break too easily, he notes) and to keep it calibrated. “The
driver should pulp the product to make sure the customer has,
indeed, put it to that temperature,” he adds.Hazen tells drivers to mount or tape a thermometer in the
rear inspection door and to check it regularly to verify the
temperature is where it should be. “We have the indicator
lights on the outside of the trailer, but the drivers should
check that thermometer every time they stop.” He cautions
drivers against taking on the responsibility of pulling down
the temperature of a “hot” load that has not been stabilized
at the right temperature.“Produce people who have you load in the field are the worst.
Produce should be stabilized at 34 degrees, but out in that
field it might be 80 or 90 degrees. The driver needs to get a
statement from the customer that says he is not responsible
for the load since it hasn't been pre-cooled,” he says. A
worst-case scenario would be with warm strawberries or
lettuce.“These units are good for 20 below zero, and they will
top-freeze your load if you try to pull down the temperature
too quickly. Since the return air coming back on the floor
will be 80 degrees, the unit will be throwing out colder air
and get below freezing as it tries to lower the box
temperature,” he explains.“Instead of setting it for 34 degrees, which is the point
where you want to hold lettuce, you have to stage it down
gradually. Set it at 50 for a couple of hours, then at 45 for
a couple of hours. It will take forever to get that load
cooled down,” he notes. “I'd want to make sure my
customer agrees that it's okay to do that or to take some
liability on the load.”The company's driver's carry a recommended tool
package to handle “quick-fix” things on the road. It
includes Vise-Grip™ pliers, an adjustable wrench, box-end
wrenches, jumper cables, screw drivers, filter wrench, pocket
knife, electrical and duct tape, electrical wire, hose clamps,
spare bulbs and nuts and bolts.
Prime sends newly hired drivers who have no experience
in refrigerated hauling out on the road with experienced reefer
drivers for six to eight months. “We do about 15%-20%
more miles than the average reefer company, so they get a
good amount of experience in that time before we turn them
loose on their own,” says Hazen. “They need to understand
how the unit works and how to handle that temperature and
the product.”Buy A Used Reefer?
Used reefers can be a cost-effective alternative to buying
new equipment. “Generally, if a driver is looking at a piece
of used equipment that he has very little knowledge of, one
of the first things he'd want to do is look for the maintenance
records on the unit,” observes Carrier's Widay. “Most major
fleets that sell used equipment keep good records. They show
what's been done on the unit, when and how it's been
serviced, and any problems it may have had.” Having a
certified technician check it out before buying it is another
good move, he agrees.Carrier introduced its RoadCare Certified Pre-Owned
Equipment Coverage (CPEC) program last winter to take
some of the risk out of buying used reefers. The program
offers the industry's first factory-backed warranty on used
reefer units. CPEC covers major components for the first
year or first 2,000 hours. To qualify for certification, the
unit must be less than five years old with under 8,000 engine
operating hours. It must also pass a 49-point inspection
performed by a Carrier dealership technician.
Prime, Inc. keeps its Thermo King reefers five years before
turning them back to the dealership. “These units are good
for probably 7 or 8 years before the compressors and
engines have to be rebuilt,” says TK's Hazen. “That's not
to say they won't have some leaks or some other problems,
but they still have plenty of service life.”Widay advises drivers to carefully read the owner's manual
and make sure they understand how the reefer operates
before taking on temperature-controlled freight. Operating
procedures vary from one model to the next, especially on
the newer, more sophisticated “smart” reefers, he observes.“For the most part, we don't find drivers actually doing
repairs themselves. But they need to be cognizant of what's
inside the unit,” says Widay. “Watching and listening are an
important part of operating a reefer. When you hear squealing,
growling or other unfamiliar noises, that's usually a sign that
something is going wrong and you need to get the unit in for
service.”Both Carrier and Thermo King have excellent web sites
packed with information on dealer locations, products,
replacement parts and company news. Browse the TK site
at www.thermoking.com. Carrier's site is at
www.carrier.transicold.com. Quarterly e-magazines at both
web sites contain news and features on customers and dealers.
[SIDEBAR]
Trailer Refrigeration Equipment
Preventive Maintenance Inspection(Courtesy of Carrier Transicold)
Engine
o Change lube oil and filters
o Check for oil leaks
o Check low oil pressure safety
o Check high and low RPMFuel System
o Drain fuel tank sump
o Clean fuel pump strainer
o Change fuel filter
o Check fuel heater (if equipped)
o Check for fuel leaks
o Check fuel lines for chaffingCooling System
o Check antifreeze
o Clean radiator and condenser fin surface
o Check hoses and connections
o Check water pump
o Check water temperature sensor functionsExhaust System
o Check mounting hardware
o Check muffler and exhaust pipesAir Intake System
o Change air cleaner element
o Check air intake tubing and clampsStarting Circuit
o Clean battery cable connections and cable ends
o Check battery hold-down clamps
o Perform battery load test
o Check starter operation
o Check glow plug operationCharging Circuit
o Check alternator mounting bolts
o Replace alternator brushes
o Check alternator outputUnit
o Check unit mounting bolts
o Check engine and compressor mounting bolts
o Check door latches and hinges
o Check gauges, switches and electrical connections
o Check all belt tensions, adjust as necessary
o Check control panel door gasket & latch adjustment
o Check gearbox for oil leaks
o Check fan shaft, idler and gearbox bearings
o Check clutch air gap (adjust as required)
o Check clutch – no slip or unusual noiseRefrigeration System
o Check compressor drive coupling
o Check air switch and calibrate
o Check and clean evaporator coil
o Check compressor oil level
o Check refrigerant level (cool cycle)
o Check operating refrigerant pressure
o Perform Quick-Check procedure
o Perform Pre-Trip inspection
o Check and clear all defrost water drains
o Check Auto Start/Stop operation
o Check quench valve operation
o Check manual defrost operationMulti-Temp
o Check remote evaporator mounting bolts
o Check remote evap air switches & calibrate
o Check and clean remote evap coils
o Check and clear all remote evap defrost drains
o Check remote compartment switches and electrical connections
o Check remote compartment manual defrost operation
o Check remote evaporator heaters
o Inspect/replace remote evap fan brushes
o Clean 5KW generator air filter
o Check 5KW generator mounting bolts
o Check 5KW generator voltage outputOther
o Clean and adjust injector nozzles
o Clean crankcase breather
o Check engine compression
o Adjust engine valves
o Drain and flush cooling system# # #
Contacts
Carrier Transicold
PO Box 4805
Syracuse NY 13221
Tel. 706-357-7280
www.carrier.transicold.comThermo King Corp.
314 90th St.
Minneapolis MN 55420
Tel 612-887-2200
www.thermoking.com
Copyright © 1998-2008 Stewart & Associates Communication Arts. All rights reserved.
