Hydraulic machines

 Hydraulic machines are a type of machinery that use fluid power to perform various tasks. They are widely used in industries such as construction, manufacturing, and transportation. These machines work by using a hydraulic fluid, typically oil, to transmit power from one location to another. The fluid is pressurized by a hydraulic pump, which then moves the fluid through hoses and valves to the desired location. Once the fluid reaches its destination, it is used to generate force or motion, depending on the specific application. Hydraulic machines are known for their high power density, precision control, and ability to handle heavy loads. They are used in a wide range of applications, including lifting heavy objects, operating heavy machinery, and controlling the movement of various mechanical components. Overall, hydraulic machines play a crucial role in many industries and have greatly contributed to the advancement of technology and efficiency in various sectors.

Roadkill Retriever Relies on Hydraulics

Talk about a niche market. It’s not unusual to see a raccoon, opossum, or other dead animal on the side of the road as you travel our nation’s highways. In most cases, ridding the landscape of these carcasses poses no great challenge. A crew of one can simply drive to the site, scoop up the roadkill with a shovel, and toss the critter into a waste receptacle. But what if the animal is too big or heavy to scoop up with a shovel? Deer fall into this category, but depending on their location, highway workers might also have to deal with disposing of elk, caribou, and even bears. That’s where the model S6-WSH disposal unit comes in handy. Designed and manufactured by Perkins Mfg. Corp., Bolingbrook, Ill., the S6-WSK consists of a 6-yd3 dumpster that fits into a standard pickup truck bed. The dumpster has two doors that can be opened and closed by hydraulic cylinders. Isolated unit This isolated view shows the workings of the S6-WSK, including some of the hydraulic cylinders that lift the doors and the bucket assembly. However, the business part of the S6-WSK is its shovel. The shovel is actuated by a pair of hydraulic cylinders and mechanical linkages that move it to ground level for easy loading of the animal. The shovel can lift loads weighing up to 1,200 lb. from a hydraulic working pressure of 2,100 psi. The hydraulic power unit is sized to provide a 16-sec cycle time—fast enough for quick operation at a safe speed. Designed by Carlos Arrez, of Perkins, the S6-WSK comes with manually operated hydraulic directional valves mounted at the rear of the unit. An operator can open and close either of two doors on the dumpster from this valve station. After opening a door, the operator actuates a valve to raise the shovel, which pivots 50 deg. to drop animal into the dumpster. Once the operator closes the doors, the hydraulic cylinders ensure that they stay closed. Perkins also offers optional remote controls for the S6-WSK that can be mounted in the vehicle cab or provide wireless remote control. Jimmy Rimsa, a design engineer at the firm, points out the S6-WSK doesn’t have to be used only for roadkill. It can also handle tree stumps and other landscaping, along with construction waste, trash, and other loose materials. He says that because the S6-WSK attaches to the bed of a standard pickup truck, it can be removed when not in use. And because the vehicle is a standard pickup, it can be deployed in areas too narrow or rugged for a garbage truck. Rimsa also acknowledges that the unusual application of the S6-WSK is somewhat of a novelty and drew a lot of attention at Waste Expo 2016. But, he says the goal was to showcase the S6-WSK as just one example of the custom-built machines Perkins Mfg. is known for—in addition to its extensive line of standard industrial and vehicle-mounted products powered by both hydraulics and pneumatics. Visit www.perkinsmfg.com for more information on their products, services, and capabilities. http://hydraulicspneumatics.com/cylinders-actuators/roadkill-retriever-relies-hydraulics

TOOLING: The Impact of Hydraulics on Tool Design

Hydraulic cylinders are used for a variety of purposes in injection molding tooling: slides, core pulls, ejection, reverse ejection, gas-assist overflows, gas-assist valve pins, valve gates, locks, unscrewing molds, etc. If you’ve worked with them, you know all about oil leaks and the headaches they create. So my preference is to avoid hydraulics whenever possible. That said, I will recommend hydraulic cylinders in situations where I feel they will perform better than mechanical features. 

In any situation where hydraulic cylinders are used, it’s important to have a better understanding of set/pull pressures and speeds. The set/pull pressure and speed can directly affect downtime with leaks and repairs. Pressure and speed can be both friend and foe. Time is money, so speed is your friend from that perspective. But it’s your foe if it causes an impact with a mechanical feature that you can hear when it is set or pulled. This will result in stress, wear, and at some point broken components in T-slot couplers or threaded rod ends. 

There are a few options to protect your components from the negative impacts of speed. Cushions can be added in the cylinder. On the pull direction, it’s better to have your cylinder bottom out instead of your component. On set position your component needs to be home, so you typically do not want your cylinder bottoming out, but there’s a solution to this that I’ll get to later. So you need to determine how speed will impact your component and potential failures.

Hydraulic pressures can also have a negative impact on your components. On the set position, if your component is relying on hydraulic pressure to overcome plastic/cavity pressure, you’ll typically need to set your pressures high. If your component is locked in place with a lock angle on the stationary half, you don’t need to use excessive hydraulic pressures—just enough to move your component. And for the pull position you’ll only need enough hydraulic pressure to pull it back. 

Over the years I have seen hundreds of failures caused by excess hydraulic pressures. In most cases this occurs with the pull position; the attachment point of the cylinder rod and component gets stretched/stressed (whereas in the set position they are compressed). One other thing to consider when using T-slot couplers: No sharp corners on the T or the slot, as they will increase your chance of failure from stress. You need to understand what hydraulic pressures are required both for movement or to overcome cavity/plastic pressure, the latter being the case where pressures are needed. 

In my experience, many setup technicians do not understand this,  and set pressures much higher than necessary. The opposite can also occur, as hydraulic pressure set too low can cause issues as well. This is not necessarily the technician’s fault; in most cases it’s the result of a lack of understanding of the tool. Sometimes even the tool shops do not fully understand these issues. Until I moved to the molding side of the plant and got exposed to hundreds of these issues, I had limited understanding of these problems when I was building what I thought was a robust tool.

There is a knowledge gap between tool shops and molding operations. The material being used, flow lengths, and wall stock can have a huge impact on the plastic pressures, facts that are not understood in depth by most tool shops. This is not a knock against designers or engineers, it’s just reflective of their lack of knowledge about the processing side. Both parties have valuable information that is not always shared in depth. 

With that being said, one area I feel needs to be examined more closely is cylinder sizing vs. cavity pressure. This is relevant in situations where the cylinder is being used to resist plastic pressure. (As stated above, if the component is using a locking angle with the stationary half, this does not need to be a consideration.) When the hydraulics need to withstand plastic pressure, the math is very simple and does not require a textbook to determine cylinder size.

In order to correctly size a hydraulic cylinder on a mold, follow these steps:
First, make sure the mold designers understand what the potential maximum plastic pressures are so they can accurately calculate the peak pressures (not just pack/hold) the cavity surface area will have on the component. You cannot just base this on the material being used; as I mentioned earlier, there are a few things that can drastically impact the pressures. If you are unsure round it up, but never round it down if you want a robust tool and process. Once you have determined the maximum plastics pressures, the rest is easy. 

You’ll need to calculate the cavity surface that is on the surface area of the component. Once you have determined the cavity surface area you multiply that by the maximum plastic pressure discussed. This result will be the pressure that you’ll need to design your cylinder around. 

At that point you can determine what bore size the cylinder should be. I typically will design the bore size so it exceeds the cavity-pressure force by 1.5 times to make sure it is robust. For example, if the expected cavity pressure is 10,000 psi and the cavity surface area of the component is 1 in.², you know that there will be 10,000 lb of force acting on the component. (10,000 lb per in.² × 1 in.²). If you multiply the 10,000 × 1.5 you’ll need approximately 15,000 lb of force to counteract the cavity pressure.

To determine the hydraulic cylinder bore size required you need the surface area of the cylinder bore size and the hydraulic pressure being used on the machine or hydraulic pump cart. Let’s say you will have 2000 psi of hydraulic pressure. Calculate the surface area of the bore diameter, which is 3.14 × R². If you use a 3-in. bore cylinder, take the radius: 1.5 × 1.5 × 3.14, which equals 7.065 in.² of surface area. Then multiply this by the 2000 hydraulic psi being used. This equates to 14,130 psi of holding force (7.065 in.² × 2000 hydraulic psi). So in this scenario a 3-in. bore cylinder should provide a robust condition.

Just like with cavity pressure, it is crucial to know exactly what hydraulic psi is going to be used. This is often overlooked or assumed. Keep in mind that on some machines the core pressure can be set up as pressure-limited with a pressure-relief valve. So even though you are changing the pressure on the controller, the actual pressure is not going up if the relief valve is set lower. So what your controller says may not be actual. 

The only way to accurately tell is to install an inline pressure gauge to measure the pressure. In the example above, if the pressure was limited to 1000 psi, you would blow back the cylinder since you would only be applying 7065 lb of force to counteract the 10,000 lb the cavity is applying to the core surface. I have witnessed this many times and have had to upsize cylinders. In one case, upsizing was not an option, so I had to add a second set of cylinders to activate a lock to hold the component in place, which made the tool more complex with a suicide condition.

One other thing that needs to be considered is the psi rating of the cylinder itself. If the cylinder is only rated for 1500 hydraulic psi and you are using 2000 hydraulic psi you will run into cylinder failures with leaks and blown seals. 

In my next column I will get into various reasons hydraulics are used, self-locking cylinders, sensors/switches, and some things to consider when designing the mold. 

http://www.ptonline.com/columns/tooling-the-impact-of-hydraulics-on-tool-design

Can Engine Oils Replace Hydraulic Oils?

"It is a common practice in the construction and mining industries to use engine oil SAE 10, SAE 20 or SAE 30 with the lowest API rating as a substitute for hydraulic oil ISO 32, ISO 46 or ISO 68, respectively for hydraulic systems of heavy equipment. Is it a problem to use these? What integrity or lack of it does it give to the machine and to the people working around the site?"
This is dependent on the equipment and manufacturer. There is a class of hydraulic fluids (DIN 51524) that contains dispersive and detersive additives much like engine oils. The use of these fluids is approved by many manufacturers and can offer several advantages in mobile equipment such as preventing varnish and sludge.
However, these detergents and dispersants can cause the fluid to emulsify any water that is present, rather than shedding water as you would want in a standard hydraulic system. The water is kept in suspension, which can cause a reduction in both lubricity and filterability, leading to the potential for corrosion and cavitation.
These problems can be avoided if the water content is maintained below 0.1 percent. Hydraulic fluid with the ability to emulsify small amounts of water can be beneficial in mobile applications. In some cases, the original equipment manufacturer even recommends using multi-grade engine oil rather than a single viscosity fluid.
Obviously, SAE and ISO use two different scales to measure viscosity. SAE 10W is equivalent to ISO 32, SAE 20 is equivalent to ISO 46 and 68, and SAE 30 is equivalent to ISO 100. As you can see, there is a bit of a difference between ISO 68 and SAE 30.
The viscosity of the fluid largely determines the oil temperatures within which the hydraulic system can safely operate. So if you use oil with too high a viscosity for the conditions in which the machine must operate, the oil won’t flow properly or lubricate adequately during a cold start. Likewise, if you use oil with too low a viscosity for the conditions, it won’t maintain the required minimum viscosity, and therefore adequate lubrication, on the hottest days of the year.
Some equipment manufacturers recommend using multi-grade engine oil in hydraulic systems for their mobile equipment. Viscosity index (VI) improvers extend the operating temperature range for the fluids. Just keep in mind that over time these VI improvers will "shear down," which will cause a change in the viscosity of the fluid at a given temperature. This will have an impact on the performance of the system.

http://www.machinerylubrication.com/Read/29715/hydraulic-engine-oils

Hydraulic Fracking Deserves Another Look

The United States faces a challenge in order to meet its energy needs. As the world’s population continues to grow, so does the need for energy. But the geologically rich U.S. need not be dependent on other countries.

Hydraulic fracturing well. Photo: James Wengler

Now that there are more advanced and greener production methods, hydraulic fracturing deserves another look. Hydraulic fracturing, or fracking, is a process by which water, sand, and a chemical mixture are pumped at high pressure deep into a shale rock formation, forcing it to crack and release its natural gas pool. Once harvested, the natural gas is transported to refineries and then to power plants, producing much-needed electricity. Fracking has proven to be less damaging than once feared. It is cleaner than other non-renewable resources, and is an especially viable replacement for so called clean burning coal.

When refined, natural gas emits considerably less carbon dioxide than coal (1,135 lbs/megawatt-hour (MWh) compared to coal’s emission of 2,249 lbs/MWh) and produces less than a third as much nitrogen oxide and one percent as much sulfur oxide at the power plant. Moreover, at a recent question-and-answer session on climate change at Columbia University, U.S. Secretary of Energy Ernest J. Moniz extolled the positive impact of natural gas on the environment and its contribution toward meeting President Obama’s greenhouse gas reduction goal. Moniz told the audience, “The natural gas revolution has been a major contributor to reducing carbon emissions. The president has a goal of 17% [reduction] by 2020, we are about half way there, and half of that is because of the substitution of natural gas for coal in the power sector, essentially driven by market forces.”

This shift from coal to natural gas has resulted in the lowest level of carbon dioxide emissions in recent years, leading to better air quality for all. Although this decrease in carbon dioxide emissions is clear, water contamination is another issue. Each fracking well requires two to five million gallons of water pumped underground to fracture the rock, and the water flowing back out carries toxic chemicals used in the fracking process that can contaminate fresh water supplies. New technology, however, issolving this issue as well. For example, GE recently developed a technique making it unnecessary to dilute the wastewater or transport it for treatment or disposal. Instead, at the harvesting site, it uses a “membrane distillation, which combines heat and decreased pressure to vaporize water using membranes to separate pure water vapor from salt water.” Also, nonfreshwater sources, such as brackish aquifers that cannot be used for drinking, agriculture or livestock, are increasingly being used in fracking. By reducing the potential for water contamination and by using greener and more advanced techniques, individual environments that depend on fresh water – habitats, ecosystems, and nature refuges –are protected as well.

Fracking also presents much needed opportunities for economic growth, especially in rural communities hit hard by the recession. In 2012 alone,fracking supported 2.1 million jobs nationwide and added $1,200 to overall household income. The Manhattan Institute for Policy Research recently performed a study comparing counties in Pennsylvania, which allow fracking, to counties in New York, which do not allow fracking. It found that Pennsylvania enjoyed significantly higher and faster economic growth between 2007 and 2011. In fact, per-capita income in Pennsylvania counties with more than 200 hydrofractured wells rose a staggering 19%, in counties with 20-200 wells and 14% in counties with fewer than 20 wells income rose 12%. In counties without any hydrofractured wells, income went up by only 8%. In addition, Pennsylvania counties with the lowest incomes experienced the most rapid economic growth.

In its analysis of nearly 5,000 wells in Pennsylvania, the Manhattan Institute also created data models for New York counties that shared similar geographic and economic indicators to determine potential economic growth. It then projected that the “income of residents in 28 New York counties above the Marcellus Shale [which includes western New York] has the potential to expand by 15 percent or more over the next four years – if the state’s moratorium is lifted.” They concluded that there was a direct connection between number of wells and higher economic growth and that “These results could equally well be applied to counties in New York and other states, from California to West Virginia, that have the potential to drill for oil and natural gas.”

These results match a similar study commissioned by the New York State Department of Environmental Conservation (NYSDEC) in 2009, whichanalyzed the potential job growth if the hydrofracturing ban was lifted in New York. It found that “hydraulic fracturing would directly create 25,000 jobs in well construction and operation, as well as 29,000 jobs in indirectly influenced industries, such as transportation. These 54,000 jobs would, in 2010, have represented approximately 0.7% of the labor force.” As demonstrated in these reports, fracking has the potential to lift communities out of their economic slumps, and provide states with much needed tax revenue.

Recent fracking measures have also helped the U.S. to achieve its highest energy output in over twenty years, thereby moving the U.S. closer to energy independence. In fact, the U.S. was able to meet 89% of its own energy needs during the first three months of 2013, while also increasing its exports. Bloomberg News reporter Asjylyn Loder explains, “Rising crude supplies from oilfields, including North Dakota’s Bakken shale and the Eagle Ford in Texas, have helped the U.S. become the world’s largest exporter of refined fuels, including gasoline and diesel. The shale boom has also helped cut world reliance on OPEC oil even as global demand gains.”

The U.S. has the resources it needs – natural gas pools and fracking techniques to harvest them – so there is no reason for the U.S. to be dependent on other countries for energy. Furthermore, because the U.S. is cutting its consumption of foreign fuel and emerging nations are expanding and developing their own resources, worldwide reliance on OPEC is declining. OPEC recently announced that “consumption of its crude will decline 300,000 barrels a day next year to 29.6 million, 2.6% less than the 12-member group is pumping now” even while “world oil consumption will advance by 1 million barrels a day, or 1.2%, to 90.7 million next year.” As the U.S. becomes more self-sufficient by tapping into its own natural resources, the power of OPEC will begin to dwindle.

The U.S.’s energy goal is sustainability – environmental and economical – and hydrofracturing meets that goal. It is the cleanest fossil fuel available, and it has the power to lift local economies. It is also a politically neutral solution, combining the left’s idealism of long-term sustainability with the right’s pragmatism of a short-term solution while moving the U.S. closer toward energy independence. Although it is a non-renewable resource and not in itself a long-term solution, it has the power to carry the U.S. into the next decades, giving science and technology a chance to catch up with renewable alternatives. It certainly deserves another look in order to meet America’s growing energy needs.

http://www.internationalpolicydigest.org/2014/02/02/hydraulic-fracking-deserves-another-look/

Rupture disc assembly for hydraulic braking system

Continental Disc Corporation has introduced a new rupture disc assembly for wind turbine hydraulic braking systems. This rupture disc assembly protects equipment from damage and down time in the event of overpressure conditions.

Specifically designed for the hydraulic braking systems and yaw brake controls of wind turbines, the rupture disc assembly provides accurate and leak-free overpressure relief for the control valve/hydraulic accumulator system. 

The hydraulic braking system rupture disc assembly is available in a wide range of sizes, materials, and burst pressure ratings for use in wind turbine protection applications.

Enter X at www.engineerlive.com/ies

Continental Disc Corporation is based in Liberty, MO, USA. www.contdisc.com

http://www.engineerlive.com/content/21862

TMC Industrial plans hydraulic machinery JV in Laos

TMC Industrial entered a memorandum of understanding yesterday with Laotian company SV Construction to establish a new company in Laos under the name TMC-Lao Assembly and Manufacturing Co to assemble and manufacture hydraulic machinery.

The joint venture will have registered capital of 1.43 billion kip for a total investment of about Bt5.72 million.

TMC Industrial will hold 70 per cent of the joint venture, while SV Construction will own 30 per cent.

Funding source

The source of funds for the investment is TMC working capital. TMC chief executive officer Surachet Kamolmongkolsuk said the JV would focus on both state and private customers and was expected to start operation next month.

TMC has targeted revenue growth this year of at least 25 per cent from its 2012 revenue of Bt1 billion. Its net profit last year was Bt135.5 million.

http://www.nationmultimedia.com/business/TMC-Industrial-plans-hydraulic-machinery-JV-in-Lao-30208733.html