As of January 2004, HydraForce has made design changes to the industry-leading environmentally-hardened Series E coils. The new design provides longer life under high-temperature conditions, as well as easier and more convenient interchange with our Series D standard-duty coils.
The Story Behind the Ratings
To appreciate the performance of the new Series E coils, it is helpful to have a working knowledge of the testing conducted to assure coil life in the harshest environments. Many OEMs request a coil that is IP67 or IP69 rated. These ratings do not address the issue of the effect of high temperatures on coil life and operation. Therefore they are of limited value in evaluating the suitability of a coil for use in typical mobile equipment applications.
Why temperature matters: When a coil is heated, the air inside the coil expands, creating internal pressure, causing the heated air to attempt to exit the coil. If the coil is then submerged in cold water, the air within the coil cools and contracts, drawing water into the coil through any seams or voids in the coil encapsulant. Eventually the water will find its way into the winding area, causing the coil winding to corrode or short-circuit, resulting in coil failure.
IP ratings are international specifications for electrical equipment which define various levels of protection against failure resulting from contamination by water or other foreign substances. The IP67 rating is based on submerging the coil one meter of water for 30 minutes. The coil is then inspected for evidence of water infiltration. The IP67 specification loosely states that “ingress of water in quantities causing harmful effect shall not occur.” The exact meaning of the phrase “harmful effect” is not precisely defined, and is therefore open to some interpretation. In this test, the coil is not subjected to high temperatures, so the effects of thermal stress are not considered.
The IP69 rating, which is currently only part of the DIN version of this specification, first requires that the coil pass the test for IP67 as described above. Beyond that, the coil and its integral electrical connector are subjected to a rigorous high-pressure water spray. The water is mixed with detergent, is held at a temperature of 80°C, and is sprayed at the coil from a distance of 100 mm (4 inches) at a pressure of 100 bar (1450 psi). Again, the specification does not precisely define the amount of water ingress that would be considered unacceptable.
Working with major mobile equipment OEMs, HydraForce
has developed even more rigorous tests that are designed to
assure that our coils will perform reliably under the harshest
real-world application conditions. Both our original and our
new Series E coils meet or exceed the requirements of what is
known as the “Thermal Shock Dunk Test.” In this test the coil
is thermally “soaked” for two hours in an ambient temperature
of 100°C. The coil is then immersed immediately in a 0°C saltwater
bath for two hours. This procedure is repeated ten times.
The coil is then inspected for water ingress. By Hydraforce’s
standards, the coil is considered to have passed this test if
there is NO detectable water ingress, as determined by visual
inspection and a “high pot” test. This standard requires a totally
sealed coil that is impervious to moisture infiltration, even
under widely varying ambient thermal conditions.
The new Series E coils can withstand at least 10
cycles of the “Thermal Shock Dunk Test.”
In addition to the requirements of the industry-recognized,
“Thermal Shock Dunk Test,” described above, HydraForce
further tests these coils for durability against failure due to
vibration, as well as against failure due to the application of
voltage above the coil’s standard duty rating while it is simultaneously
subjected to continually varying ambient temperatures.
Beyond enhancing the durability of the coils, we have
decreased the wattage by approximately 10%. This reduces
the power consumption and also allows the operating
temperature range to be extended. The new design also
improves the ease and convenience of interchanging these
coils with HydraForce’s Series D (standard duty) coils, the
original Series E coils, as well as the older “W-style” waterproof
option. The new Series E coils use the same retaining nuts as
the Series D coils, simplifying interchangeability, inventory and
assembly requirements and procedures.
See page 3.400.17 for detailed information describing the
differences between the original Series E coils and the new
Series E coils, including part number cross-references for the
coils, the retaining nuts, and the spacers used on the dual-solenoid valves.