Answer: For Viking pump 23579: @400 RPM flow rate is 6 GPM, @1750 RPM flow rate is 33 GPM.
Answer: As long as there is pressure during operation, gearbox should be receiving sufficient amount to maintain lubrication. At set up, 31 psi is expected. If pressure falls below that, could be rise for concern.
Answer: Amarillo Gear does not recommend the use of an additive.
Answer: Amarillo could offer another gear (Double reduction gear) but this would require significant structural changes.
Answer: There are many factors that affect the surface temperature of the gear drive. Examples of these are air velocity, air temperature, humidity, and radiant heating from exposure to sunlight. Because these variables are outside of our control, we do not set limits on the surface temperature of the gear drive.
The lubricant film strength is the most important factor for assuring the longest operational life of the gear drive. Proper film strength assures separation of metal surfaces and prevents premature wear. Since the film strength is determined by the oil temperature, it is the parameter that should be monitored during operation of the gear drive. The lubricant used in our gear drives is selected to provide adequate film strength at 200°F (93.3°C).
Again, many external factors can affect the oil temperature. There is no maximum value, only different solutions based on the actual operating oil temperature. For example, if the oil temperature is between 180°F (82.2°C) and 200°F (93.3°C), a mineral oil has adequate film strength, but it oxidizes at a faster rate. In this case, the oil must be changed more frequently. (Many users will not do this, so our O&M Manual cautiously recommends synthetic oil above 180°F (82.2°C).) At temperatures, above 200°F (93.3°C), we recommend using a synthetic product that provides greater film strength than a mineral oil. Only in extreme circumstances should the oil temperature reach or exceed 200°F (93.3°C).
Answer: The weight of internal components is small compared to the load capacity of the bearings, so “Brinelling” of the bearings is not a concern unless the gear is installed and has heavy components attached to the shafts. The only reason to rotate the shafts periodically is to distribute the oil on internal parts exposed to air to reduce oxidation and corrosion. Our long-term storage procedure requires filling fan drives completely with oil which dispenses with the need to rotate the shafts. On pump drives, it is recommended to rotate the shafts every month as stated on the nameplate.
Answer: The spherical roller bearings are spring loaded which increases the torque required to turn the shaft. In addition, the thrust bearing outer race can be knocked off-center during shipment, so the gear drive would be very hard to turn. The thrust bearing is self-aligning once it rotates with an applied load.
Answer: The maximum value for lateral vibration is 0.3 in/sec (8 mm/sec) peak, filtered reading. This means that on a vibration spectrum, with frequency on the X-axis, none of the peaks should be above the 0.3 in/sec (8 mm/sec) level. Reference AGMA 6000 for more information.
Answer: Cortec VCI-358 is applied to exposed shafts prior to shipment. This product may be removed from the shafts using a cloth soaked in mineral spirits, alkaline cleaners, aliphatic solvents, or vapor degreasing solvents.
Answer: Typical acceptable values for continued use of a gear oil are:
|Viscosity||AGMA 4 – greater than 135 cSt and less than 165 cSt at 40°C
AGMA 5 – greater than 198 cSt and less than 242 cSt at 40°C
|Water Content||less than 400 ppm|
|Total Acid Number (TAN)||less than 2.0|
In addition, if the viscosity increases 10% or more between samples and the TAN increases, the oil should be changed. This is an indication that the oil is oxidizing at a rapid rate.
Note: TAN is the amount of KOH required to neutralize one gram of oil and is a measure of the oxidation. This is sometimes called the neutralization number (NN). Another measure, the oxidation number, is a product specific value and is performed on an infrared spectrometer. The units for oxidation number are absorbance/cm. To use oxidation number, the oil manufacturer must specify the acceptance limits for the specific product. As an example, Mobil Gear 630 has an upper limit of 8.0.
Answer: Amarillo Gear does not recommend placing the breather inside the fan shroud. This placement could potentially draw humid air into the gear case and contribute to oil contamination. Ideally, the vent line should slope downward to the outside of the fan shroud with the breather at the lowest point. Piping that forms “traps” should be avoided to prevent the vent line from filling with oil or water and preventing the gear drive from breathing.
Answer: Yes. Amarillo Gear Drives are designed specifically for the demanding environment of cooling towers. Therefore, the drives may be physically larger than many of the “industrial” gear drives that have been adapted for use in cooling towers. Some tower modifications may be required to replace the existing gear drive with the Amarillo model. Some of the items that must be considered are: shaft sizes, location of the fan in the shroud, height of the input shaft from the base, required coupling length, and bolt hole pattern.
Answer: In general, lubricants that meet AGMA #5 are recommended for use in our cooling tower fan drives. In addition, lubricants must be compatible with nitrile and viton seals, Amarillo’s lacquer-based gear case sealer, and sprag-type backstops. Extreme pressure lubricants are not recommended. Assuming a product meets these requirements, it may be used in our cooling tower gear drives.
Answer: Oil heaters with thermostats are recommended whenever the fan drive will be started with an ambient temperature around the gear drive of 20°F and below. If hot water flowing through the tower maintains the ambient temperature above this limit for a period of time prior to start-up, then heaters are not required.
It is important that the oil is above its pour point temperature prior to start-up. Starting the fan drive when the oil temperature is below the pour point will result in no oil flow to the upper bearings and possible damage to internal components. Very viscous oil can cause oil slinger screws to shear and can overload the shaft on optional positive displacement oil pumps.
Synthetic oil has a much lower pour point than mineral oil. The synthetic oils listed in our O&M Manual may be used in our fan drives, without a heater, when the gear drive ambient temperature is -20°F and above. However, keep in mind that synthetic oil is expensive. Additional advantages are listed in our O&M Manual.
Below -20°F, synthetic oil and heaters are required.
|Ambient Air Temperature||Recommendation|
|Greater Than 20°F||mineral or synthetic oil|
|20°F to -20°F||mineral oil with a heater / thermostat, or synthetic oil|
|Less than -20°F||synthetic oil with a heater / thermostat|
|Ambient Air Temperature||Modification Required|
|Less Than 120°F||None|
|120°F to 150°F||Synthetic Oil or Viton Seals|
|Greater than 150°F||Synthetic Oil, Viton Seals, External Cooling|
Answer: The main benefit of an oil filter is that it removes most of the particles that cause abrasive wear on the gears and bearings. This will extend the service life of the gear drive if oil is changed at recommended intervals. It is important to understand that an oil filter does not prevent oil contamination from water or oxidation. The main causes of premature failure in cooling tower fan drives is low oil level or poor oil quality, not abrasive wear. Oil filter elements require replacement, so maintenance costs are higher when using an oil filter, and the external plumbing increases the potential of an oil leak.
Answer: The filtering system used on a double reduction fan drive utilizes a positive displacement pump that is driven by the intermediate shaft. The pump forces oil through the filter mounted on the outside of the gear case. The filter contains a 75 micron, acrylic fiber element that has low pressure drop. The filter housing has a built-in bypass valve to ensure oil flow with a clogged filter. After filtering, the oil is routed inside the gear case where it is distributed to the bearings and gears using a manifold system.
Answer: A customer may elect to use an Extreme Pressure (EP) lubricant; however, Amarillo Gear Drives do not need the EP additives to operate properly. In fact, EP additives will prevent our sprag non-reverse devices from properly functioning.
In the past, data from bearing manufacturers had suggested that EP lubricants might extend bearing life. At that time, we recommended EP lubricants in gear drives without a sprag type backstop. However, current research indicates that some EP additives may reduce bearing life. Because Amarillo Gear has a long history of gear drives in service using non-EP oils, we conservatively decided to take EP oils out of our O&M Manual.
Answer: Often, mechanical oil pumps are specified because many of our competitor’s gear drives require the oil pump for lubrication. This is because they sell multipurpose, “industrial”, gears that are adapted for use in cooling towers. Amarillo Gear Drives are designed specifically for cooling towers and use an oil slinger system that operates in either direction. A mechanical oil pump on our fan drives is an extra cost option, but is not required. The oil slinger is installed and functional, even when the oil pump is added.
Our oil pump is truly bi-directional. It will pump in either direction while using the same suction and discharge ports. Many years ago, we worked with Viking Pump to design and manufacture this bi-directional oil pump. The reason other gear drive suppliers warn against running in the reverse direction is that they use a standard unidirectional oil pump and they do not have the oil slinger as a redundant system.
Answer: The minimum oil level below the center of the sight glass is shown for each model below. These should be considered absolute minimums (3/4” of oil on slinger); oil levels below those shown may result in loss of lubrication and gear failure.
|Model||Min Oil Level Below Normal|
Answer: During short periods of several hours, wind milling of the fan poses no problem for the gear drive. During wind milling, the speeds are low and the load on the bearings is light so the existing lube film is adequate. If the fan windmills for extended periods of time, it is possible that the bearings could lose their lube film causing damage. In these situations, our optional mechanical oil pump is recommended on double reduction fan drives, and the optional electric oil pump is recommended on single reduction fan drives. Both options will supply fresh oil to the bearings regardless of the wind milling speed, direction, or duration.
Answer: Gearbox alignment is critical for a smooth and quiet running gearbox with a long trouble free service life. If the gearbox is grossly misaligned, the driver (motor or engine) cannot transmit uniform rotation to the gearbox. Consequently, the following problems may occur:
Basically, the input shaft of the gearbox and the output shaft of the driver should be parallel and the centerlines of both shafts should be in a common vertical plane.
Many different types and makes of drive shafts are being used. The tolerances for the shaft angular misalignment vary. Typically, a gearbox can tolerate larger misalignment than can a drive shaft. Consequently, Amarillo Gear does not set the tolerances for shaft alignment. Rather, the tolerances should be obtained from the drive shaft suppliers.
Answer: L10a rating life is the life that 90% of a group of identical bearings will exceed before a fatigue spall develops, with adjustments for material, reliability, and operating conditions.
Answer: It is recommended that vibration transducers be placed at the locations shown on Form 612 (fan drives). If specified at the time of order, we will drill / tap / spot-face vibration transducer locations on the gear drive. In the field, however, to avoid the possibility of drilling through the gear case and creating a possible oil leak, it is recommended to attach sensors using epoxy mounted thread blocks in the specified locations.
Answer: Hardware and torque is specified in Amarillo Gear Engineering Form 551.
Answer: Both a new and renewed AGC gearbox have a warranty of 12 months from install date or 18 months from shipment date. Marley warranties can be extended to up to 24 months.