Dealers who sell and service diesel-powered off-highway equipment and the operators who depend on this equipment know firsthand the problems cold weather can cause for newer emissions-controlled engines. When temperatures dip below freezing, many systems running emissions-controlled Tier 3 and Tier 4 diesel engines simply won’t start, or worse, start and then become marginally operable, or worst, start and then self-destruct. No matter where the equipment is being used, the end result is the same: Costly downtime and lost production. Most often the problem can be traced to a frozen emissions-control component that triggered the engine control module (ECM) to prevent the engine from either operating at full power, or even from starting.
In addition to the diesel engine components that have historically been problematic in cold weather—e.g., fuel filters and fuel injectors—today’s emissions-controlled engines add crankcase ventilation components such as filters, valves, and breather hoses, as well as DEF (diesel exhaust fluid) lines, to the mix of cold-weather offenders.
Although shore-powered (120 V ac and other mains-voltages) heating solutions for many of these problems have been available for some time, heating solutions for remote users—i.e., those who must rely on the equipment’s battery power at startup and alternator power while operating—have been, until recently, unavailable. By and large, OEMs have been slow to provide solutions, perhaps in part because an estimated 80% of all diesel-powered heavy equipment is sold in geographies that remain above freezing year-round. The upshot is that designing and implementing systems to combat frozen and freezing emissions-control engine components has been left primarily to the aftermarket.
Keeping diesel emissions-control components warm
To meet the challenge of frozen components on off-highway diesel engines, a number of equipment dealers and operators have found a new solution that retrofits emissions-control engine components with autonomous heating systems powered by direct current (dc). The new programmable and insulated systems combine an industry-proven thermostat and algorithms, insulated heating jackets and heated hoses, and a variety of heating elements for safe and efficient heating of emissions-control components.
The heart of today’s new heating jacket and heated hose systems is a solid-state thermostat with sophisticated temperature-sensing and control algorithms. The thermostat controls a dc-powered heating element that runs on 12- to 24-V power from the engine battery. The control algorithms allow the patent-pending systems to deliver heat as quickly as an emissions-control engine component can safely absorb it. The result is fast, efficient thawing of frozen diesel engine components—e.g., from a temperature of -58 to +23°F (-50 to -5°C) in less than five minutes, with minimal current draw—and energy-efficient temperature maintenance once the components have achieved a nominal operating temperature.
As an example, in-house testing measured thawing of a CCV (closed crankcase ventilation) unit from a canister temperature of -40 to +33°F (-40 to +1°C) in approximately 3.5 minutes using about 190 W of power. Once the component’s operating temperature is reached, the thermostat conserves dc battery power and leaves sufficient amps for normal engine starting by sending just brief pulses of heat into the thawed unit to maintain its required temperature.
How it works: Thermostat with temperature-sensing control
The thermostat’s temperature-regulating algorithms control the maximum surface temperature of the heating element in the heating jacket or heated hose system and the average temperature of the emissions-control engine component being warmed or thawed. By limiting the maximum surface temperature of the heater while simultaneously controlling the average temperature of the engine component, the programmed algorithms prevent the heater from producing temperatures that could melt or scorch engine component material and or damage the heater.
A solid-state thermostat with a resistance temperature director, or internal sensor, can be mounted directly on the engine component whose temperature is being controlled. For instance, the temperature of a PCV (positive crankcase ventilation) valve/filter can be measured directly through the body of the thermostat. Alternatively, an external thermocouple can be used, allowing the thermostat to be mounted elsewhere and the thermocouple to be applied to the item being measured.
The solid-state thermostat has dual temperature input channels, one to sense the surface temperature of the heater in the heating jacket or heated hose system, and a second to sense the average temperature of the engine component being heated. For example, on a DEF hose the average temperature sensor is placed on what appears to be the “worst case” location, which is very close to the coupling that connects the hose to the tank and then the SCR (selective catalytic reduction) system. The thermostat’s pre-programmed algorithms use these sensor signals for controlling the temperature of the heating element surface and the average temperature of the engine component being heated.
Compared to traditional bimetal thermostats, the solid-state thermostat offers several advantages:
• Set points as low as -40°F, while comparable bimetal units are not rated to function below 32°F (0°C).
• Estimated MTBF (mean time between failures) of greater than 5 million cycles, compared to bimetallic thermostat ratings of 250,000 cycles under alternating current (ac) and just 5000 cycles on dc.
• Ability to switch up to 30 A of current in a small and rugged temperature controller, while bimetallic thermostats are limited in the amount of dc they can carry, and in high-current dc applications, the thermostats tend to fail on the ON position quickly causing overheating and possible damage.
• Single-piece, solid-state construction means no arcing from the opening and closing of mechanical switches.
Bringing the heat to frozen components
While the thermostat and control algorithms are at the heart of the latest aftermarket heating systems, the design and construction of heating jackets and heated hoses is also critical for a reliable, complete solution for thawing and freeze prevention.
New aftermarket insulated heating jackets are made of durable, chemical-resistant closed-cell Nylon 6 foam selected for superb heat retention and other important performance characteristics. The polymer is exceptionally resilient against tearing and punctures, and is not affected by contact with gasoline or diesel fuel. The flexible jacket and a dc-powered heating element that conforms to the contours of the component being warmed allow heat to be distributed evenly and efficiently through the component. The heating jackets are highly configurable and can be made to fit odd shapes, and different heating element types are available to fit specific applications.
New aftermarket heated hoses are enclosed in EPDM (ethylene propylene diene monomer) foam insulation with a braided-nylon sleeve to improve heat retention and reduce battery draw. The durable sleeve withstands normal engine hazards such as accidental punctures, abrasion, and sharp edges. A flexible heating element attached to the insulated hose allows heat to be disbursed evenly and efficiently through the component.
By installing the latest heating jacket and heated hose systems, dealers and equipment operators can overcome the problems that previously accompanied efforts to heat engine components using dc power from an engine battery—high battery drains, slow heat-ups on systems without insulation or accurate temperature control, and frequent downtime to replace burnt-out mechanical thermostats.
Until manufacturers of diesel-powered off-highway equipment solve the cold-weather starting issues of emissions control equipment—or until diesel technology evolves once again—heavy equipment sellers and buyers need to find their own solutions for engine component thawing and freeze prevention. One place to look is the new dc-powered aftermarket solutions that combine unprecedented temperature control and engineered jackets and hoses for heating CCVs, PCVs, fuel filters, and DEF lines.
Whether upfitted at the dealer level or installed by operators in the field, an intelligent thawing and freeze prevention system will give heavy equipment users effective ammunition for the battle to start cold diesel engines.
Rick Garber, President of engenity, LLC, wrote this article for Off-Highway Engineering as part of the annual Executive Viewpoints series appearing in the June 2016 issue.Continue reading »