As winter approaches this year, northern commercial pavement sweeping companies once again face the seasonal challenge of keeping the functional parts of their road equipment working. That includes the hydraulics and the hydraulic motors. These critical components must operate efficiently throughout the winter months.
Regional Winter Issues with Hydraulics Motors
During the coldest months in the northern regions, the motors that power hydraulics on sweeper trucks must withstand the extra strain of managing heavier loads and longer hours in worse conditions without overheating. Farther south, operators may expect to deal with more rain, slush, and tree and landscape debris on pavement during fall and winter. That may mean longer operating hours than in summer. Coastal providers are confronted with even more extreme salt impacts on equipment in more turbulent winter weather and that’s an even worse problem along northern coastlines.
All these conditions can be punishing for hydraulic mechanisms and motors. Whether your street sweepers continue to operate as such year-round, or with snow removal equipment attachments, deicing material spreaders, etc., they need protective care to prevent hydraulic motors from overheating.
Daniel Strati, Canada Sales Director, Bailey Hydrauliques
Early on, Strati fell in love with hydraulics, became an outside sales rep in the industry, a buyer, even ran a shop for a few years, then opened his own company. He took a number of hydraulics courses through the years and studied under multiple academic leaders in the field, including Drs. Fitch, Tessman, Hong, and Porel in France.
Now, after 46 years designing hydraulics systems and consulting internationally in the US and Europe, Daniel offers the benefit of his wisdom to North American Sweeper magazine readers. Daniel is the resident hydraulics motor design expert of the Canadian division of US-based Bailey Hydraulics.
Here, he shares some critical insights and tips on hydraulic motor design selection, the best lubricants for various applications, ventilation systems installation for hydraulic motors, currently available temperature monitoring systems, and more.
Hydraulics Motor Design
Daniel explains that a motor converts energy to generate motion. He emphasizes that the primary factor to consider is the design of a hydraulic system. He notes that although you may be able to fix it later, the first priority is to ensure the motor is sized for the system properly in the design phase. He explains that a critical symptom of an improperly sized unit is that it is creating excess heat inside the motor.
Another emphasis is ensuring that there are no air leaks. These can lead to increased heat generation, which can produce bubbles and cause heat cavitation. Per Daniel, “A nightmare of hydraulic motors is a pump that will generate excessive heat. Once a bubble of air is created, and it smashes against a plate, it will burst the plate and run down the motor, make marks on the metal, and lead to less efficient aeration.”
A hydraulics system needs to run between 110०F and 130०F. So, if it’s operating properly, you can lay your hand on it and it will feel barely warm. Some systems run at around 150०F to 160०F due to the sweeper vehicle’s engine temperature.
Therefore, according to Daniel, when you design the motor, the question becomes, “Are we in a cold or hot situation in operating the vehicle?” He explains that when you design the motor, the fluids you use need to maintain their viscosity to have smooth operation. For optimum lubricity, additives to the oil may be necessary to avoid damaging parts.
As you gain in temperature, some of the oil will damage itself very fast. Some oils will maintain their viscosity at virtually any temperature. So, use only the best oil for your hydraulic motor. Don’t be cheap on this.
Try to use a very good motor, not a cheap one. Some are efficient at 70% and some at 90%. That is the measure of the flow outside, low pressure and high pressure, and how it remains in terms of the volume metric efficiency of the motor, i.e., if it can give you 100 gal per min, for example.
Further, Daniel points out, misalignment of a hydraulic motor during installation is obviously a serious error. “People often think they have no side load. When you have a load pushing on the side of the shaft, you can expect to have some efficiency issues.”
The other percent discussed is heat not being used. That input energy is not converting to work and is therefore causing heat inside your system. Size the cooler effectively. If the total input power loss to heat ratio is greater than the heat will dissipate, then the system will overheat 25-40% is the rule of thumb.
Proper Use of Your Hydraulics Motors
To avoid an excessive load working at the top end of the motor, try to use it at its most efficient range. It will develop a torque. It should not be at the minimum or maximum, but in the middle. If you use a motor at an extreme level, it won’t last as long. It will generate excessive heat and prematurely degrade, and lose efficiency.
Efficiency loss means generating additional heat, which accelerates the deterioration. So, remember:
- Don’t over speed a motor. Don’t look at it as a motor that can run at 3000 rpm, for example. Don’t run it too fast.
- Loss of efficiency causes heat generation.
- Control contamination. if you don’t have clean oil, you’ll have less efficiency, which, again, creates heat.
- If you underestimate the pressure and do an adj at 2000 psi for ex and in reality it’s 2200 psi. The 200 lbs of pressure you’re losing is causing heat generation.
- Improper adjustments create heat. We see this all the time. Have needed adjustments made by a hydraulics professional.
How to Keep Your Hydraulic Motors from Overheating
Hydraulic motors convert energy from pressurized hydraulic fluid into motion. So, per Daniel Strati, from design to installation to routine maintenance on the essential hydraulic components, there are factors for equipment owners to consider when designing a hydraulic system include:
- Size your system properly; do not undersize it to save money.
- Ensure against air leaks that can cause bubbles and generate heat in your system.
- Stay on the lookout for aeration and cavitation.
- The normal operating temperature to consider is 110०F to 130०F.
- Consider the ambient temperature.
- Avoid excessive load or over-speed of the motor.
- Size the cooler effectively. If the total input power lost to heat is greater than heat dissipated, the system will overheat. A rule of thumb is to cool 25% to 40% of input power.
- Prioritize quality in fluid selection.
- Ensure against misalignment of the motor during installation.
- Inefficiency results in losses of input power, which is converted to heat use in high-efficiency motors.
- Contamination control is paramount in the smooth operation of hydraulic motors and mechanisms.
Comprehensive Hydraulics Motor Management
Remember, the right design, materials, installation, and maintenance are all necessary to achieve the right oil pressure. Any input energy that is not converting to work will cause heat to be generated excessively and efficiency will be compromised. So reach out for help when needed.
Bailey Hydraulics’ engineering team of about 18 experts helps our customers’ engineers design and oversee the building of snow and ice-clearing equipment.
For more information about hydraulics motor design, installation, or maintenance, or to order parts, contact Bailey International LLC, Knoxville, TN, by calling (800) 800-1810, or visit baileyhydraulics.com.