Water ingress into an Amarillo pump drive is a common issue, but with an understanding of the issue and proper maintenance, these should easily be avoided. Listed in most to least common, the 3 main reasons for water ingress are:
Excessive Water from Pump Gland
Whilst some water is required to lubricate the pump gland, if too much water is flowing through the gland, the excess water can enter the gearbox through the oil tube at the base. The Amarillo pump drives use a dry well construction. Oil is retained in the sump by means of a bung and a stand pipe (the oil tube). There is no rubber or mechanical seal to stop contamination from getting in. Water can therefore enter through the oil tube.
Corrosion between water fittings and cooling coil fittings
All Amarillo pump drives supplied through Hebco Industrial are fitted with either an internal cooling coil, or an external heat exchanger. The case has 2 bosses located underneath the input shaft with tapped holes for cooling water. From the outside, hose barbs or similar fittings are screwed into the case. From the inside, a fitting is screwed into the case for connection to the internal cooling coil. Since these fittings do not physically meet, there is exposed cast iron.
Over time, the cast iron can corrode and water can get past the fittings and into the oil. Many people assume that it's the cooling coil itself that has sprung a leak but this is rarely the case in Australia. In fact, we have only ever seen a handful of cases where the cooling coil itself is leaking. Being copper, it is far more resistant to corrosion than the other materials the gearbox is made of.
Cracked Cooling Coil
In climates where the temperature drops below freezing it is possible for a cooling coil to crack. While farmers obviously aren't irrigating during these conditions, if cooling water is not purged from the cooling coil prior to the freezing conditions setting in, water can freeze in the cooling coil and if there is nowhere for it to expand, it can crack the copper tube. When the system is started up next season, water can then enter the gear drive.
Whilst some of our farming land does drop below freezing during the winter months, it is not cold enough for long enough to result in this type of failure. We have never seen a gearbox come into our workshop with a cooling coil failure due to frozen water.