Hydraulics

You may know that properly maintaining a hydraulic pump will ensure maximum efficiency and prevent damage, but did you know that it is especially critical to regularly monitor inlet conditions? Poor inlet conditions can result in cavitation—the second leading cause of pump failure.

While it’s common for people to think of a pump’s inlet as sucking in oil, in reality, it is atmospheric pressure doing the work. In essence, the weight of the atmosphere pushes the oil out of the reservoir and into a region of lower pressure—the inlet. Once the oil is forced from the reservoir and through the inlet, it then moves the volume of liquid into a region of decreasing volume to create flow. For this process to begin, there must be minimum pressure at the inlet of a hydraulic pump, as shown in the diagram below.

As you can see, the inlet of a pump plays a large role in how well it operates. Unfortunately, those designing and maintaining pump systems can become so focused on downstream flow that they overlook proper inlet maintenance. This can result in degradation of inlet function and serious problems such as cavitation.

Cavitation occurs when the absolute pressure on the inlet side of the pump is too low and air is drawn out of the solution, creating bubbles in the oil. As these bubbles get pushed around to the high-pressure outlet side of the pump, they collapse. This creates localized shock waves that blow bits of material out of the pump. It can also result in excessive heat and reduced lubrication that leads to friction and wear over time.

Cavitation can cause pump failure and it can damage other components of your system, which is why it is critical to examine the condition of the pump's inlet on a regular basis.

PSI versus PSIA. What’s the difference? PSI, or pounds per square inch, is a unit of measurement for pressure used in the United States. PSIA describes the absolute pressure in psi, including the pressure of the atmosphere. Absolute pressure is also referred to as total pressure. 

There are two areas you should monitor to maintain minimum inlet pressure on steady-state pumps:

1. The energy it takes to lift oil through the suction line (including pressure drop due to flow). We refer to this action as Phase 1 pressure, because it represents the amount of energy it takes to accelerate the fluid through the pumps internal pathways and keep the pump full. 

1. The minimum absolute pressure the pump must have in order to avoid damage.  This is known as the Net Positive Suction Head, or NPSH. 

In order for a pump to function, atmospheric pressure must be greater than Phase 1 pressure + NPSH. Every pump has its own specifications regarding acceptable minimum/maximum inlet pressure, but we can use the example below to illustrate how to calculate it.

To begin, assume that you are maintaining an 18 GPM hydraulic pump. The NPSH is equal to 12 PSIA with standard hydraulic oil and 1800 RPM per manufacturer’s specifications.

As you can see in the diagram above, the inlet line is 1.38” in diameter x 18.1” long with a 12.1” lift using standard petroleum-based fluid. 

Each foot of oil lift requires approx. = 0.4 PSI. Fluid velocity is 3.8 feet per second. A typical lookup table shows there will be a 0.05 PSI drop due to the flow through the pipe. 

Total loss of the inlet line during steady state is 0.4 PSI + 0.05 PSI, or 0.45 PSI. 14.7 – 0.45 = 14.25 PSI. Because this final number—14.25 PSI—is greater than the NPSH of 12 PSIA, you can rest assured the system is functioning well.

If we apply the same numbers to a variable-volume pump, the result will be less acceptable. Here’s why: Imagine the pump is not in demand and is therefore being held off stroke, meaning there is no flow. When the pump is suddenly needed, it will come on stroke, requiring the column of oil in the suction line to accelerate. This sudden change in demand requires the pump pressure to accelerate from static to a pressure that is strong enough to move the oil and prevent cavitation.

Let’s look back at our model, applying revised numbers.

Assume the pump strokes on in 70 milliseconds (msec). The volume of liquid that has to accelerate is 1.5in^2 x 18.1” = 27.1 cubic inch (cu. in.). Note: Since the entire column of oil in the pipe has to accelerate, we used a measurement of 18.1” instead of 12.1”.

To calculate the weight of oil in the inlet line, we multiply the volume (27.1 cu. in.) by specific weight (0.0314 lbs./cu. in.), equaling 0.85 lbs. Fg (gravity force) = 0.85 lbs.

Fa = mass x acceleration 

a = v/t = 3.8/0.07 = 54.3ft/sec^2

Fa = (0.85/32.2) x 54.3 = 1.4 lbs.

Ft = 0.85lbs + 1.4 lbs. = 2.25 lbs.

The available force in the pipe from the atmosphere (Fluid power (Fp)) = 14.7 PSIA x 1.5 sq. in. = 22.05 lbs.

Net force = 22.05 lbs. – 2.25 lbs. = 19.8lbs.

NPSH = 19.8 lbs./1.5 in.^2 = 13.2 PSIA 

These calculations reveal that the system is fine, because the pump requires a minimum 12 PSIA at its inlet to operate effectively. However, if this system was installed at 2,300 feet above sea level (13.4 PSIA), the pump would cavitate whenever it came on stroke.

           13.4 PSIA x 1.5sq in = 20.1lbs

            20.1 lbs. – 2.25 lbs. = 17.85 lbs.

            17.85 lbs./1.5 in.^2 = 11.9 PSIA, which is lower than the minimum 12 PSIA required.

The above example assumes no losses due to other plumbing, however, it is not uncommon to see elbow fittings on pump ports, which could add to losses in the inlet line.

In addition to maintaining good inlet conditions, any small leak on the inlet will entrain air, which is also bad for the pump. Small leaks will cause a pump to lose prime whenever the system is shut off, which means it will start dry and run dry until prime is re-established. For this reason, it is never a good idea to install hydraulic pumps above the fluid level. Rather, hydraulic systems designs should ensure that the pump inlet is flooded, i.e. the oil level is above the pump inlet. A ball valve can be used to isolate the pump from the reservoir in case it needs service, and a limit switch can be used on the ball valve to prevent the system from running if the ball valve isn’t fully open. 

For more information on hydraulic inlet maintenance or other topics, email us. Your pump will thank you.

This article contributed by Tim Beck, manager - system design and application, Parker Hannifin Corporation Hydraulic Pump and Power Systems Division.

Related articles:

Choosing an Efficient Electric Motor for a Hydraulic Pump: Part 1 of 2

Choosing an Efficient Electric Motor for Your Hydraulic Pump: Part 2

Benefits of Compact Closed-Circuit Pumps for Mobile Hydraulic Applications

Doing more with less is a common theme in business and the pump market for medium-duty applications is no exception. With the overall hydraulic system size becoming increasingly smaller and smaller, mobile, medium-duty end-users in industries such as oil & gas, construction, agriculture, transportation and material handling industries are in search of a flexible, high-performance compact pump.

With two hydraulic pump loop options, open circuit or closed circuit, a closed circuit loop saves valuable system space by offering continuous fluid flow without the need for additional parts. In comparison, an open circuit loop typically requires a larger reservoir and as a result, increases the system’s footprint. To fulfill the market’s need for smaller hydraulic components, Parker recently introduced the PC3 Compact Closed Circuit Pump. This article explores three primary benefits of the PC3 pumps:

1. Compact size

On trend with hydraulic mobile systems decreasing in size, each system component has to do more in order to save valuable system space. PC3 is a solution for this market trend with a closed-circuit design, resulting in fewer components than an open circuit hydraulic pump. In addition to the closed-circuit design, it also offers a built-in bypass valve and hot oil shuttle valve eliminating the need for third-party components, conserving valuable system space.

2. System efficiency and streamlined performance

To achieve greater system efficiency and streamlined performance, PC3 includes a variety of features, such as:

- A hydraulic pressure override to ensure that the prime mover is not loaded in excess

- A built-in hot oil valve to increase operational efficiency and reduce system complexity

- Cross port reliefs to prevent system overload by limiting the maximum pressure in your system

Each of these features ensure system performance and efficiently deliver the exact power required for each unique application.    

3. Flexibility

Finally, Parker’s PC3 offers the hydraulic pump market flexibility through various product features and sizes to use in a wide variety of applications.

PC3’s modular and interchangeable controls include options for a manual servo, hydraulic proportional and electric proportional controls, providing end-users with further customizations.

In addition, the product line offers ten standard displacements options: 7, 11, 18, 20, 25, 30, 35, 40, 45, 52 and in three different frame sizes to help customer choose the best option for their medium-duty applications ranging from turf care to transportation.

When designing hydraulic systems for mobile equipment, getting the right pump is crucial.  Resources are available to help ensure the right selection is made—use an online configurator for assistance in selecting the best compact closed-circuit pump for the application. Full system supplier such as Parker can also assist with overall system designs that optimize all of the components to work together. For more information, contact us.

Article contributed by Justin Wheeler, product manager, Hydraulic Pump and Power Systems Division
 

Related content:

PC3 Product Animation

Choosing an Efficient Electric Motor for a Hydraulic Pump: Part 1 of 2

Choosing an Efficient Electric Motor for Your Hydraulic Pump: Part 2

Bain’s projections show that the Internet of Things (IoT) market will grow to $520 billion in 2021. Specific to the construction market, 6.8 million connected heavy construction machines will be shipped between 2018 and 2025. Although no one in the industry has a crystal ball, it is predicted that the future of mobile IoT will be driven by machine learning and 5G networks to power further data collection and analysis, enable autonomous equipment operation and overall innovation in the field.

Technology that can remotely analyze millions of points of data in real time, make decisions and report on the data as necessary will enable machine intelligence to begin moving from the cloud to the machine itself. For instance, a recent case study by Parker’s Mobile IoT team illustrates how an OEM was able to improve their time-to-service, hydraulics-related efficiencies and customer loyalty with the use real time diagnostics and over the air programming. This is by contrast to the current method of telematics systems sending limited data to a server based on thresholds and events. 

The basis of competition is changing for OEMs, and it's important for organizations to monitor the basic assumptions of competition to redefine the space going forward. For the longest time, the industry was based on driving machines through engine power, however, electrification is changing how an OEM manufactures off-road equipment. Electrification, as well as remote monitoring, positively impacts the priorities during the engineering process such as the safety element. Furthermore, off-road machines have been operated by people for decades but with the development of robotics and other autonomous capabilities, those assumptions are changing. Electrification reduces the safety concerns centered around hydraulic and autonomous machines can eliminate the human safety factor during operation. 

Semi-remotely operated or semi-autonomously operated equipment opens up a host of possibilities in terms of machine design. But when you understand how connected machines will be sold or distributed, OEMs are not only looking at selling products but at offering services that can be remotely monitored, controlled or operated. This opens us up to a whole host of things in terms of business models. As part of Parker’s Tech Tuesday video series, Parker’s Business Unit Manager for Mobile IoT discusses the trend of IoT for off-road equipment and how the business model is evolving.

Although the push towards autonomous equipment follows in the path of the automotive industry, the challenges for autonomous machines in areas such as construction and agriculture differ from automotive. The environments these machines operate in lack lane lines, signage, sidewalks and other indicators that automotive vision systems rely on to guide cars. The additional “appendages” of booms and buckets must also be taken into account for their operation. In sectors like mining, autonomous equipment is highly attractive. It can take hours to properly ventilate an area after blasting to make it safe for operators to enter. Removing humans from that equation will increase productivity and safety in operation.

It will take time for this technological evolution for the off-road industry to occur, though, due to the uncontrolled environments in which off-road equipment is typically used. More advanced Artificial Intelligence (AI) will be required than what is currently available. The future of mobile IoT lies in building the fully connected environment where all elements of the contractor’s job are seamlessly integrated. 

With AI, users can learn patterns that lead to failures or how to operate the equipment to maximize its useful life, offering trade-offs between performance and longevity.

According to the Association of Equipment Manufacturers (AEM), AI will empower construction teams to handle critical tasks but there are challenges that must be overcome in order to achieve widespread adoption, including fear among workers of AI taking away their jobs, cultural resistance to new technologies and security. These are challenges that OEMs, suppliers and AI partners are already addressing in order to move their industries forward.

Embedded IoT systems rely on cellular communication technology. As 5G networks are being rolled out, it’s clear that they will change the way that data is transmitted via IoT systems. With the coming of 5G, telematics companies have spearheaded the development of Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) communications capabilities. This sophisticated level of machine-to-machine (M2M) communication will be critical to autonomous vehicle operations. It would very difficult to implement to implement autonomous today given so few data points going to the cloud. Data being sent to the cloud today is limited, simply because of the cost to not only send it, but to store it, process it and then drive decisions with it. The promise of 5G is the ability to send a lot more data with less latency, which will enable more real-time operations such as streaming video and the other necessary functions for autonomous mobile equipment.

In the future off-road machine operations will change from being hydraulic driven to more electrical driven, to more software driven. That means that our industry, not only in designing machines but also building, and servicing, and maintaining the machines is going to have to migrate to a having talent that is capable of operating in that software digital space. That's why you see a lot of companies in our space starting to hire more and more software engineers.. The addition of an IoT solution is positively impacting job responsibilities by increasing efficiencies at the same time IT job titles within OEMs are becoming more and more necessary to support IoT, electrification and the development of autonomous operated equipment.

The introduction of digital technologies in the off-road equipment industry is here. Therefore, organizations need to consider the following technology roadmap:

• Hire experienced professionals with IT skills
• Create strategies for effective deployment
• Allocate appropriate budgets
• Generate analytics to gain insights into the various industry trends
• Educate employees and customers about the positive impact

Digital disruption has already made multiple industries more competitive. Similar situations will be faced by the off-road equipment industry when digital technologies become more broadly leveraged.  Traditional operational and service-related tasks need to be executed faster and more efficiently, and mobile IoT solutions can help.

Article contributed by Clint Quanstrom, IoT general manager, Motion Systems Group, Parker Hannifin Corporation.

Related articles:

Modern Digital Ecosystems Take Mobile Hydraulic Systems to a New Level

When New Machines Have a Voice, What Will Old Machines Do?

Decoupling the Future of Electrification

The design and deployment of aerial lifts, truck-mounted cranes, telehandlers, scissor lifts, man lifts and other modes of vehicular material handling demands two requirements above all others:

• Safety for the operators

• Operational integrity for the vehicles

Achieving these dual goals requires constant monitoring of out-of-level conditions. For three-quarters of a century following the Industrial Revolution, analog technologies addressed this challenge with visual indicators at each axis, which an operator then had to diligently monitor, making mechanical adjustments to ensure personal safety and the safety of the load—a task that required extreme vigilance and precise execution.

By the last decades of the 20th Century, electronic controllers powering audio signals and flashing lights had arrived on the scene to help reduce a handling system’s dependence on the operator’s monitoring of individual gauges for each axis of control. Many of today’s material handlers continue to rely on such electronically powered alert systems.

But with the advent of the Internet of Things (IoT) and the near-limitless interconnectivity possibilities it presents, a seismic shift has occurred in material handling control. The Universal Tilt Sensor (UTS) technology was specifically designed to optimize operator and load safety while facilitating interconnectivity.

Download the Universal Tilt Sensor Technology white paper and learn how smart sensor technology optimizes operator and load safety while facilitating interconnectivity through the IoT.

Universal Tilt Sensors operate over a CAN bus using an industry-standard SAE J1939 communication protocol and an integral Deutsch DT four-pin connector. With UTS, OEM designers can deploy one product to achieve single, dual or three-axis mobile control, while it's plug-and-play connectivity with a full range of Parker hydraulics and electronic control components ensures system-compatible data collection, monitoring, and alerts. The communication scheme also facilitates daisy-chain-style single-harness configurations that reduce exposure to accidental cutting and pinching and other operators or environmentally induced damage.

For OEMs and their customers, this means one single part can perform the many functions that formerly required a multitude of individual products, slashing inventory requirements, simplifying both installation and replacement, as well as reducing related labor.

UTS technology features a low-profile form and three slightly offset mounting holes around its diameter that make it easy to install and remove, even in challenging field conditions. This fool-proof mounting profile ensures the UTS is properly and consistently mounted across a vast array of machines while enabling a full range of horizontal, vertical and angular mounting positions.

UTS technology features glass-filled hybrid-plastic construction with no moving components and is designed to resist corrosion and vibration. Its robust sensor technology can withstand rugged material handling environments. With a spin weld design and a sealed connector, environmental protection for outdoor as well as indoor applications is ensured. The UTS is rated IP68/IP69k in all orientations, and IP68 upside-down. For lifts working around electric or magnetic fields, UTS provides effective insulation against electromagnetic and electrostatic interference, meeting or exceeding EMI and ESD ISO environmental protection standards. In addition, customers who have field tested the UTS reported it providing predictable linearity over its specified operating temperature range (-40°C to 85°C) and without deviations experienced with competitive products.

Perhaps most exciting of all is the infinite possibilities for connectivity possible using UTS technology. This closed-loop electro-hydraulic solution communicates over an open, industry-standard protocol, enabling plug-and-play IoT connectivity to controllers, hydraulic components, data collection, and reporting software, as well as to the entire family of Parker hydraulic and electronic products and accessories.

• Ladder engines using UTS for auto leveling and boom elevation transmitting operational behavior back to an OEM design team, which they can use to analyze safety-lapse trends and improve next-generation vehicles

• Refuse trucks, dump trucks or forestry equipment operating on steep inclines transmitting individual route profiles back to the home office to identify problem areas and improve safety training

• Material handlers transmitting information on operator behavior to spot and intervene when irresponsible handling repeatedly requires override intervention

• Every mobile hydraulic vehicle’s field performance being monitored by OEMs to facilitate warranty reviews and reduce liability

As more and more components and processes attempt to leverage the IoT, UTS technology will become a drop-down configurable component within an increasingly complex, interconnected system that:

• Promotes operator safety

• Optimizes equipment performance

• Provides comprehensive reporting for analysis and improvement

• Increases productivity through predictable maintenance and improved uptime IoT connectivity

• Improves customer satisfaction and loyalty through proactive data-driven service engagement

• Selectively shares data across distribution and supply channels

Download the Universal Tilt Sensor Technology white paper to see the UTS technology solution in action from a multi-angle standpoint and operational point-of-view.

Article contributed by Marcel Colnot, regional application engineer, and Chase Saylor, product manager - sensors, Electronic Controls Division, Parker Hannifin Corporation.

Related, helpful content for you:

Smart Sensor Enhances Material Handling Systems Closed-loop Control

Modern Digital Ecosystems Take Mobile Hydraulic Systems to a New Level

Industrial IoT Solutions with Voice of the Machine at Bauma China

Position Sensing of Mechanical Components in Rail Increases Safety

Designing a Heavy-Duty Construction Vehicle Cab

For decades, the dump truck industry has been relegated to two sizes of dump pumps; a larger, higher flowing (up to 27GPM) C Series pump, and a smaller, lower flowing (up to 16GPM) G series pump. The smaller size of the G series pump is ideal for trucks with automatic transmissions. New drivers in the truck market are less familiar with manual transmissions, creating a need for more automatics. However, using the G series pump means slower dump cycles for trucks outfitted with automatic transmissions, when compared to their manual counterparts. Slower dump cycles mean less material is being transported and more time is spent onsite, which can diminish profits.

All dump pumps are connected to a power take-off unit (PTO), which is mounted to the truck’s transmission. The PTO draws power from the transmission and allocates it to the dump pump. The truck’s transmission is nestled between the frame rails of the truck chassis. On trucks with manual transmissions, the PTO and dump pump are mounted using an opening on the bottom of the transmission. However, on trucks with automatic transmissions, a PTO mount on the bottom side does not exist.

Automatic transmissions typically have PTO mounts on their side, with limited space between the frame rails for installation. This design creates a space problem. The large C series cannot fit between the side mounting and the frame rails. To fix this problem, a smaller dump pump was designed to fit in the limited space. The G series dump pump produces less flow with a smaller valve, solving the space constraint issue, but resulting in a slower overall dump cycle time.

To close the gap between automatic and manual dump cycles, Parker's Pump & Motor Division has launched a new dump pump that combines the best of both designs into one; a mid-size pump with a larger, integrated dump valve, that can be mounted to automatic transmissions. As a high flowing pump with a smaller footprint, the new pump was deemed the Super G (SG102).

For ideal performance, Parker recommends pairing the Super G with the 280 Series PTO, and SG102 series pump support brackets from Parker Chelsea. Compatible and easy to access equipment means less time is spent on installation of the Super G, meaning that retrofits are quick and easy. Once installed, the Super G provides drivers, using automatic transmissions, faster dump cycles and greater productivity.

The Pump & Motor Division is a market leader in gear pump and low speed-high torque gerotor motors, that continues to blaze a trail in the industry by developing new technologies, while maintaining the high level of service synonymous with Parker. Between its two locations in North Carolina and Tennessee, the division employs decades of industry experience to better serve you and your application.

This article contributed by CT Lefler, marketing product manager and Makenzie NeeSmith, marketing intern, Pump & Motor Division, Parker Hannifin Corporation.

Related articles:

Meeting Your Work Truck's Demand for More Hydraulics Space

Simplified Hydraulic Pumps for the Low Speed, High Torque Market

Hydrostatic Transmission Fluid Engineered for Low Maintenance

This is part two of a two-part post explaining how to determine the best size for a hydraulic pump motor and how to scale the size and cost with RMS loading and Hp limiting.

In Part 1 of this post, we discussed the correct way to size an electric motor for a hydraulic pump. Now we’re going to take things a step further by explaining how to safely scale down the size of your motor for increased efficiency and cost-savings.

There are two methods that you can use to safely put a smaller motor to work in your hydraulic pump. One is the Root Mean Square (RMS) method and the other is Hp limiting. Which you choose is based on how the hydraulic pump will be utilized.

Most hydraulic power units do not continuously operate using the same power load, and their flow and pressure levels are constantly changing as various actuators move during the machine cycle.

As an example, during a single cycle, a hydraulic pump might shift from 10Hp for ten seconds to 15Hp for five seconds, 4Hp for thirty seconds, 12Hp for ten seconds, and 5Hp for 20 secs. Although the pump reaches 15 Hp during the cycle, that is not its continuous operating zone. Rather, it is the upper range of the power demand.

In the chart below, you will see that the RMS value in this example is well below 10Hp. This means that as long as the power demand doesn’t exceed 150% of the motor’s rating—and the RMS value doesn’t exceed the motor nameplate rating—an 10Hp motor could be safely used in this application.   

We arrived at the above solution by calculating the varying amounts of power needed throughout the cycle as well as the amount of time that power is used. In short, RMS or root mean squared power represents the integral of the squares of the instantaneous values during a cycle. The mathematical calculation is as follows:

If we take the numbers from the example above and apply them to this equation, the resulting calculation would look like this:

Power (RMS) = SQ.RT. ((10Hp^2x10s + 15Hp^2x5s + 4Hp^2x30s + 12Hp^2x10s + 5Hp^2x20s)/(10s+5s+30s+10s+20s)) = 7.78Hp

NEMA motors can be sized using this technique, IEC motors typically cannot.  If in doubt, contact your motor vendor. When using a VFD make sure the drive can handle occasional overload current. 

Another instance in which a smaller motor may be appropriate is with applications that require high flow at low pressure and high pressure at low flow. In such a case, you can utilize a variable volume pump that is capable of limiting its own power requirements, thus enabling a smaller motor to be used.

Let’s say your system requires a 20 GPM @ 500 PSI during rapid advance and 3000 PSI at 0.5 GPM (clamping). Using the basic (flow x pressure)/(1714 x eff.) formula for sizing that we discussed in Part 1 of this post, you would probably consider selecting a 40Hp electric motor. But wait! Because this application requires high flow at low  pressure and high pressure at low flow, you can use an Hp limiting pump and safely scale down to a 25Hp motor.

Pumps that offer horsepower limiting or other control options can help make your hydraulic system much more efficient while enabling you to conserve energy. Contact your local Parker Hannifin distributor for more information on Hp limiting pumps or for help deciding whether or not choosing a smaller motor is smart choice for your hydraulic pump. And, in case you missed it, check out Part 1 of this post for more detailed information on determining the best motor size for your hydraulic pump.

For more information on Choosing an Efficient Electric Motor for a Hydraulic Pump, contact Parker's Hydraulic Pump and Power Systems Division. 

This article contributed by Tim Beck, manager - system design and application, Parker Hannifin Corporation Hydraulic Pump and Power Systems Division.

Related links:

Choosing an Efficient Electric Motor for a Hydraulic Pump: Part 1 of 2

Hydraulic Pump/Motor Selection Considerations for High-Production Shredding Applications

Essential Criteria for Selecting the Right Motor for your Hydraulic Application