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  • Low-Speed, High-Torque Motor has Wealth of Features

    1. Applications requiring heavy loads to be accelerated from rest, such as this portable concrete mixer, stand to benefit from Fluidyne Fluid Power’s new 500 Series low-speed, high-torque motors.

    ​Geroler-type hydraulic motors have a great reputation for delivering low-speed, high-torque power. Their compact design also makes them the first or only choice when space is tight — especially because they drive loads directly without needing a speed-reducing gearbox.

    However, some designs of geroler motors exhibit internal leakage that prevents them from starting loads effectively from rest. The internal leakage allows fluid to bypass pressure chambers and some of it flow through the motor’s case drain. The result of this bypass is reduced starting torque.

    2. Fluidyne’s heavy duty 500-Series motors target low-speed, high-pressure applications.

    ​Fluidyne Fluid Power, Fraser, Mich., resolves this issue with its new heavy duty 500-Series Motors. The 500-Series motors are available in 11 nominal displacements from 125 to 750 in.3/rev. (7.20 to 45.45 cc/rev.). The motors’ valve-in-rotor design efficiently distributes oil and reduces overall motor length. A pressure-compensated balance plate improves volumetric efficiency at low flow and high pressures. They feature bi-directional rotation and a high-pressure Viton shaft seal that eliminates the need for a case drain.

    Joan Armstrong, engineering manager at Fluidyne, explains, “These motors are especially suited for low-speed, high-pressure applications with smooth rotation throughout speed transitions. The hydrostatic balance pressure plate flexes to allow for proper lubrication and high operating efficiency. Plus, the combination of shafts, mounts, and displacements let you configure these motors to almost any application requirements.”

    For more information on the 500 Series motors and other products, call (586) 296-7200, or visit www.fluidynefp.com.

    From hydraulicspneumatics Thursday, May 5, 2016
  • Hydraulics Serves Aussie Navy

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    The HMAS Canberra docks down in Sydney Harbor to receive an LHD Landing Craft containing a powerful hydraulic ventilation drive. (Courtesy of Royal Australian Navy)

    For nearly 40 years, Fluidmecanica SAU, Pontevedra, Spain, has designed and manufactured marine machinery, hydraulic controls and transmission, and pneumatic systems. Last year, four military landing craft worked on by Fluidmecanica were delivered to the Royal Navy of Australia at its HMS Waterhen Naval Base near Sydney. The landing craft operate in conjunction with two Canberra-class landing helicopter dock ships and are qualified under NATO requirements.

    Each landing craft is 23.30 meters long and can achieve speeds exceeding 20 knots. Fluidmecanica designed and built the ventilation system for the engine room of each craft. A ventilation system may seem like overkill for a hydraulic system, but the rigors of the application requires the high power density and durability of hydraulics.

    Hydraulics on the Move

    Two pairs of hydraulically powered blowers rotate at 2,900 rpm to move up to 17,000 m3 of air per hour (10,000 cfm). Each hydraulic gear motor (two connected in series) driving a fan is fed by a variable-displacement hydraulic piston pump powered from each of the landing craft’s two 809-kW (1,080 hp) engines. Hydraulic pressure for each circuit is 280 bar, and maximum flow is 10 lpm.  This is where the versatility of hydraulics is important, because fan speed must be controlled independent of engine speed.

    Fluidmecanica’s Francisco Oliver Rivera explains that a variable-speed electric drive would not have been practical for this application. “An electric drive is more bulky and weighs about 60% more. It would also be prone to failure under high shock and vibration. NATO shock requirements are especially demanding in boats like this, which may have to operate near shelling fire during operations.”

    Fluidmecanica tests a ventilation fan driven by a hydraulic gear motor. Two pairs of these fans are used in landing craft designed and built for the Royal Australian Navy.

    The pump that drives the fan has variable displacement, so its output per revolution increases or decreases inversely with engine speed, says Rivera. “Each pump has a load-sensing control, so we achieve fixed flow with a metering block. In this case, the flow remains fixed over the engine’s complete range of speed—from 1,000 to 2,800 rpm.

    Rivera also says that because the landing craft are designed for use in combat, simplicity and rugged operation were high priorities. “Each hydraulic pump is directly coupled to the engine, so the system automatically starts with the engine. There is no need to switch the fan on or off, because if the engines are not running, the fans are not needed.”

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    From hydraulicspneumatics Wednesday, April 13, 2016
  • ABB Inc: Current Limiting Miniature Circuit Breakers with Ring Tongue Connections

    The breakers conform to UL 489, CSA 22.2 No. 5 and IEC/EN 60947-2 standards. They are, the company says, currently the only UL489 MCB on the market with rated current up to and including 35 A for 480Y/277 VAC, and up to 63 A for 240 VAC. The Supplemental Protection conforms to UL1077, CSA 22.2 No. 235 and EN 60947-2 standards. Both ranges are available in 1, 2, 3 and 4 pole configurations, from 0.2 A through 63 A, and feature integrated captive screws that simplify the secure connection of cables, prevent installers from loosing the connection screws, provide extra protection and save time. All markings are permanent laser markings, clearly visible from the front even when mounted in position on the DIN rail. The breakers have a true Contact Position Indicator (CPI) that indicates the actual contact position, ensuring the display of fault conditions such as contacts that may be “welded” closed due to excessive fault current. They also comply with the latest UL requirement for barriers of MCBs fitted with ring tongue terminals, and their structural material is a flexible, recyclable thermoplastic.

    >>For more information on this product, click here
     

    From automationworld Thursday, January 10, 2013
  • Hose installation

    Figure 1. Make hose assemblies long enough and routed in a manner that prevents exceeding minimum bend radius recommendations.

    Most engineering efforts focus on ways to design and manufacture products that satisfy application requirements as inexpensively as possible. But you can make a satisfactory design better by making it more reliable and easier to maintain – and without spending a lot of money. How? Simply by following simple tips and recommendations offered by manufacturers. These fundamentals concern bending, alignment, motion, and similar basic guidelines.

    Application basics

    Unlike metal tubing, hose is flexible, so it is used primarily to allow relative motion between components at either end of the hose assembly and to simplify routing and installation. It is much easier to route a hose assembly over, under, around, or through a series of obstacles than it is to bend and install a rigid tubing assembly. Furthermore, replacing a hydraulic line by fabricating a rigid tube assembly often is more costly and time consuming than making a hose assembly.

    Figure 2. To prevent excessive strain at hose-to-coupling interfaces, make hoses long enough to allow for contraction and expansion.

    Most manufacturers offer hose that can be bent to a tighter radius than that published in industry standards. Still, bending hose to a smaller radius than recommended should be avoided to avoid shortening service life. Therefore, route hose in a manners that provides ample bend radius, Figure 1.

    Because hose is flexible, you must allow for contraction and expansion when cutting the hose to length. Manufacturers state that, depending on its type, hose can elongate up to 2% when pressurized, but, more importantly, can contract as much as 4%. This length differential can strain hose reinforcement wires and eventually lead to failure, especially at the hose-to-coupling interface. Therefore, cut hoses slightly longer than needed to compensate for contraction, Figure 2.

    Figure 3. Left-hand drawing shows how hose twists because it is bent in one plane while oscillating motion bends in a second plane. Rerouting the hose eliminates multi-plane bending.

    Bend hose in one plane only to avoid twisting its wire reinforcement, which would reduce the hose’s pressure capability. Manufacturers state that twisting a high-pressure hose only 5° can reduce service life by 70%, and 7° of twist can reduce service life up to 90%. Unfortunately, hose routing usually occurs late in the design process, so it may be difficult to find an ideal path. Multi-plane bending often can be avoided by reorienting the hose, Figure 3. If this is not possible, install a hose clamp between bends, Figure 4, and provide enough length on both sides of the clamp to relieve strain on the hose’s reinforcement wires. This length depends on the hose ID, degree of bending, and helix angle of the particular hose’s reinforcing wire, so manufacturers prefer to evaluate each application individually.

    Figure 4. When multi-plane bending cannot be avoided, install a hose clamp between bends and provide enough hose length on both sides of the clamp to relax torsion and compensate for hose contraction.

    Another alternative is to use a single section of hose for each bend and install a hose-to-hose coupling and hose clamp between bends. This technique is less preferred because it not only is more costly and time consuming to perform, but increases the number of potential leak points in the hose assembly. Also, to help ensure that technicians replace and secure hose assemblies properly, include detailed instructions on hose length, use of hose clamps, and special considerations in service manuals.

    Providing protection
    Figure 5. Hose clamps can prevent abrasion by holding hose away from surfaces it would otherwise rub against.

    Hose manufacturers now offer a variety of products with abrasion-resistant covers. No wonder: manufacturers state that about 80% of hose failures are attributable to external physical damage, with abrasion cited as the major culprit. Abrasion is generated primarily by hoses repeatedly rubbing against equipment surfaces or each other.

    To help prevent abrasion, use clamps to secure hose in place and keep it from rubbing against adjacent surfaces, Figure 5. The clamp should have a snug fit around the hose to prevent movement, but not be tight enough to damage the hose by squeezing too tightly. Be sure the hose is slack on both sides of the clamp to compensate for contraction and expansion.

    Additional protection can be provided by sleeves. Metal sleeves resemble springs that protect the hose from being crushed. Fabric sleeves help keep abrasive particles away from hoses, and both types can serve the added function of nestling multiple hoses into a compact bundle.

    Some types of sleeves must be installed from one unconnected end of the hose and slid along its length. Others have a longitudinal slit to enable installing the sleeve without having to disconnect either end of the hose assembly.

    Accommodating movement
    Figure 6. Design at left provides ample hose length when cylinder is pivoted, but bends hose in too small a radius when cylinder is vertical. Increasing hose length and providing greater clearance produces much greater bend radii.

    In addition to causing twisting and abrasive wear, motion can also quickly spell doom for hoses that do not properly accommodate equipment dynamics. For example, hoses connected to a cylinder that undergoes pivoting motion, Figure 6, must be of proper length and routed to avoid becoming kinked or bent beyond their minimum bend radius.

    An item that can make a good design better is a swivel joint, sometimes called a live swivel. Unlike standard swivel fittings, which connect hydraulic lines at any fixed angular position, swivel joints accommodate relative motion between the hose and the component to which it is connected. As Figure 7 shows, swivel joints permit pivoting motion that reduces the bending transmitted to the hose assembly and can reduce the length of hose required.

    Figure 7. Swivel joints can extend hose life by reducing the amount of bending caused by relative motion between machine elements. They also aid maintenance by simplifying hose installation and replacement.

    When multiple lengths of hose lie close to each other, and substantial linear motion will occur, hose carriers keep hoses neatly nestled to prevent tangling, twisting, and rubbing against each other. Depending on which particular type is specified, carriers can also isolate the hoses inside from potentially hostile conditions outside – impact from falling objects, abrasive particles, chemicals, or intermittent high temperatures.

    Other important considerations

    Most hydraulic hose is wire reinforced, which makes it an electrical conductor. For equipment that may be used near power lines or where hose will be in close proximity to flammable solutions that could be ignited by static electricity discharged from the hose, manufacturers offer non-conductive hose.

    In other applications, static electricity sometimes may be discharged through the hose wall to surrounding surfaces. This is caused by conducting electrostatic charges from the fluid through the hose’s metal reinforcement and cover to adjacent surfaces. Consequences can include localized burning that weakens the hose or even produces pin-size holes in the hose wall. In this case, hose with a conductive tube may be called for to conduct electrostatic charges to hose end fittings rather than through the hose.

    Just as twisting can dramatically shorten hose life, so can excessive heat. Heat from external sources, such as exhaust components on mobile equipment, can quickly soften or embrittle the hose wall from the outside in. Therefore, it is important to keep hose away from external sources of heat. If this is not possible, manufacturers offer insulated protective sleeves to partially block heat transmitted to the hose.

    Figure 8. Lack of planning produces cluttered hose routing, far left, that complicates maintenance and can even reduce hose life. Well-thought-out routing and choice of end fitting configurations, near left, makes assemblies that are more reliable and easier to maintain and troubleshoot.

    However, heat from an internal source — the hydraulic fluid itself — also can reduce the service life of the hose. Pumping hydraulic fluid at a temperature of only about 18° F over the maximum recommended temperature for a hose can cut its expected life in half. What makes this problem even more serious is that machine operators often are unaware that fluid temperatures may exceed manufacturers recommendations – especially if the high temperatures occur only intermittently.

    Finally, strive for neat appearance when routing hoses, Figure 8. This not only prevents tangling, twisting, and rubbing together (which can cause abrasive wear), but aids maintenance by making it easy to remove and re-install hose assemblies and trace circuit routing.

    Use adapters sparingly because they add to the number of components in an assembly. This increases assembly time, cost, and the number of potential leak points. However, when properly applied, adapters can simplify hose assemblies that use angled fittings (such as 90° elbows) at each end. Hose-end fittings on these assemblies must be carefully oriented to prevent twisting the hose during installation. So using an angled hose coupling at one end of the hose and a straight coupling connected to an angled adapter fitting on the other eliminates the need to carefully align hose ends during assembly.

    Clean hose prevents early contamination troubles

    When cutting hose to length, either a serrated or abrasive blade is used. Serrated blades cut one- and two-wire braid and textile-reinforced hose cleanly and efficiently, but usually are not recommended for use on spiral-reinforced hose because the blades would wear quickly or become damaged. Abrasive wheels cut all types of hose efficiently, but produce abrasive debris that usually finds its way into the hose. If not flushed from the finished hose assembly, this debris holds potential for serious wear and damage to sensitive components of the hydraulic system. Skiving and crimping can also produce debris that must be removed before putting the finished hose assembly into service. Skiving involves cutting a length of the outer jacket from the hose to prepare it for accepting a hose-end coupling. Crimping squeezes the coupling onto the hose’s inner and outer surfaces, so some residual plating material could come off and find its way into the hose.

    Compared to skiving and crimping operations, storage can introduce more and a wider variety of contaminants. During storage, dirt, water, metal particles, rust, abrasive particles, and any number of other types of contaminants may migrate into a hose sitting on a shelf. It should be obvious, then, that all hose assemblies should be cleaned before being put into service. At the very least, finished hose assemblies should be cleaned with a strong blast of compressed air. Naturally, this air should be clean and dry.

    The most effective cleaning technique is high-velocity, bidirectional flushing. This floods the hose assembly with cleaning fluid until the fluid comes out of the hose as clean as when it went in. However, the cost of this equipment and the time required to flush an assembly makes it impractical for many potential applications.

    A relatively new cleaning technique offers an effective and practical alternative to these procedures by using sponge-like projectiles that are shot through hose and tubing assemblies by a blast of compressed air. Equipment for this procedure is much more affordable than that for high-velocity flushing. Perhaps more importantly, though, it cleans assemblies much more effectively than compressed air alone and in a fraction of the time it takes for high-velocity flushing.

    Once the hose assembly has been cleaned, be sure to install protective caps or plugs at both ends to prevent contamination from entering the assembly. These should not be removed until the hose assembly is being installed on the equipment.

     

    From hydraulicspneumatics Sunday, January 1, 2012
  • Thermal Analysis of a Garbage Truck’s Hydraulics

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    A characteristic sometimes overlooked with hydraulic systems on industrial trucks, such as garbage trucks, is what happens when  they operate at high fluid temperature.  High fluid temperature can degrade the fluid, cause premature failure of components, rob system performance, and even pose safety hazards to personnel. 

    A finite-difference model for a typical garbage-truck hydraulic system was derived to predict these temperatures. Actual weather data for a sea-level southwestern American city in mid-summer were used as input parameters for the model to represent actual worst-case conditions. This model considered pressure losses in the hydraulic system from viscous effects and friction during operation. These losses increase internal energy of the fluid, resulting in higher fluid temperature. The model also incorporates calculation of heat transfer to and from the hydraulic system. The system receives solar radiation and expels heat by convection to the ambient air. 

    The model predicts fluid temperatures of up to 300° F during normal operation of each truck on a day when the ambient air temperature reaches 115°F. The 300°F temperature produced by a garbage truck under such conditions significantly exceeds the maximum recommendation of 180°F for hydraulic fluid. The conservative model also tends to underestimate pressure loss and thermal parameters that predict fluid temperatures. Actual fluid temperatures for the given meteorological parameters will be higher than those in the model output. 

    Building the Algorithm

    The algorithm in the model was based on the first law of thermodynamics, which states that the heat transferred to a system equals the sum of the increase in internal energy of the system and the work done by the system. If we consider hydraulic fluid to be incompressible, its specific heat is well documented.  The product of the fluid’s specific heat and the increase in its temperature yields the increased internal energy of an incompressible fluid. Therefore, we can calculate fluid temperature if we know the initial fluid temperature and the temperature change, which is determined by evaluating the heat transferred to or from the system and the work done by or on the system. 

    Heat transfer evaluated by the model includes solar radiation into the hydraulic system and convection of heat from the system to the ambient air.  Solar radiation data were obtained from a state meteorological database for a day when the ambient temperature reached almost 115°F.  These data give the amount of solar energy incident on a horizontal surface by hour of the day. We estimated that the hydraulic system absorbs 80% of incident radiation, based on documented emissivities of similar materials. 

    Both free convection and forced convection were evaluated as mechanisms for transferring heat from the hydraulic system to the air. Free convection is a process in which molecules of a fluid (ambient air in this analysis) in contact with a warmer body absorb heat, become buoyant, and are displaced by molecules with less internal energy.  For the sake of simplicity, we assumed that no temperature gradient exists between the hydraulic fluid and the ambient air and that the wall temperature matches that of the hydraulic fluid. 

    In reality, the walls of hydraulic reservoirs, hoses, and other components tend to absorb heat from the fluid. Therefore, wall temperatures are actually lower than the fluid’s, creating an insulating effect. The heat transfer rate varies directly with the difference between the wall temperature and the temperature of the air, so the actual heat transfer rate from the fluid to the ambient air by free convection will be less than that estimated by the conservative model.

    More on Convection

    Forced convection occurs when a fluid (ambient air) is directed at some non-zero velocity against a warm surface.  Heat is transferred by a combination of buoyant effects and momentum as energy from the warm surface by conduction to molecules of air. These molecules are then replaced by other molecules lower in internal energy. Wind promotes forced convection. Meteorological data for a sea-level southwestern U.S. city were inspected, and it was found that the maximum wind speed for many days stayed less than 8 mph during the hours of operation for the packer trucks. 

    In keeping with a conservative approach, we assumed that the wind blew directly across the hydraulic system and reservoir in the direction most beneficial for cooling the system. Furthermore, the outer wall of the reservoir is partially exposed to ambient air as the truck is driven. An average effective wind speed of 12.5 mph (relative to the reservoir) was calculated, based on the estimated truck speed and portion of the day during which the truck was moving. Forced convection of heat from this surface was calculated based on the higher effective wind speed. Because the rate of heat transfer varies directly with wind speed, these choices for wind speed values are conservative.  As in the free convection analysis, wall temperatures were equated with hydraulic fluid temperature.

    Pure conduction of heat from the hydraulic system and reservoir to another solid body was not considered a significant mechanism for cooling because the contact areas are small and because other nearby bodies are also heat sources (the truck engine and exhaust).  Conduction between solid bodies is proportional to the contact area and the temperature difference. Radiation and convection of heat from the road surface to the hydraulic system and reservoir also were not considered because of the difficulty in describing these mechanisms mathematically and because assuming them to be negligible is conservative. 

    Components of the Hydraulic System

    The hydraulic pump in these trucks is driven through a power takeoff (PTO). The difference between the input power from the PTO and the work performed by the hydraulic cylinders becomes pressure losses as the hydraulic fluid flows through the circuits. Empirical data relating pressure loss to fluid flow rate for different types of hose and tube are available in the literature.

    Hose sizes were taken from the specifications for an actual side-load compactor truck, and pressure losses were obtained from these data. Pressure losses for pipe and standard fittings (elbows, tees, sudden expansions, sudden contractions) are related to fluid velocity, density, and viscosity and are proportional to empirical factors reported in literature. The sizes of pipe and fittings were obtained from drawings, and losses were tabulated after calculations were made using this information. 

    Pressure losses through filters, hydraulic control valves valves were obtained from the actual manufacturers’  technical catalogs for each model. Properties of a typical hydraulic fluid recommended for use in such climates (Texaco Rando HD46) were obtained from literature published by Texaco for that fluid.  

    Setting up the Analysis

    Perfect data cannot be obtained for any analysis.  In cases in which directly applicable data for refuse truck specifications, drawings were not available, or calculation of input parameters or data was not straightforward, we made assumptions that could be reasonably supported. When no reasonable assumption could be made, data that would lead to higher predicted fluid temperatures were not used, in order that the analysis remain conservative. 

    We assumed that the packer trucks operate on a 10-hour daily shift. The actual time each truck is collecting (and, therefore, operating the hydraulic system’s boom and pack circuits) is approximately six hours per day. The pack circuit is continuously operating while the truck is collecting, then is turned off when the truck is driven to and from a landfill, transfer station, or fleet garage. 

    The boom operates intermittently while the truck is loading cans at a house. It is then inactive when the truck is driven between houses. Based on discussion with waste management personnel, it was determined that each truck collects solid waste from 1,200 to 1,300 houses per day. Using these parameters, duty cycles were evaluated for the boom and pack circuits and were applied by the model to the calculation of pressure losses because no pressure losses occur when the hydraulic system is not actuated. However, heat transfer occurs continuously. 

    For much of the time, the pack circuit is actuated, but the boom circuit is not.  During these times, the model calculates no losses for the boom circuit.  However, hydraulic fluid is still flowing through the control valve for the boom circuit and back to the reservoir, although no fluid flows through the work port on the control valve. In reality, though, some pressure loss from this flow still occurs when only the pack circuit is actuated. Omitting this loss tends to underestimate fluid temperatures and is conservative. 

    Examining the Results

    The finite difference model was run for three cycle times: 8, 10, and 14 seconds. Actual cycle times usually range from 10 to 14 seconds. The table above shows detailed results for the 8-sec cycle, whereas the graph below summarizes fluid temperatures during the day for a 10-sec cycle. The analyses account for the normal activities of the truck and operators during a typical shift,  including driving to pickup sites and back to the collection yard, collecting refuse in residential neighborhoods, break times, lunch time, and refuse dumping.

    This graph plots hydraulic fluid temperature for a 10-sec cycle time. Similar trends resulted with 8- and 14-sec cycle times.

    This scenario of activities is proposed as typical based on our experience for daily collection operations. It undoubtedly varies from day to day and from truck to truck.  We don’t expect these variations would alter the conclusions for this analysis. Solar radiation as energy incident on a horizontal surface per unit time was obtained for a southwestern U.S. city for the subject day and is shown on the table.

    The time increments shown generally conform to the operational activities for the truck, except in the early hours, where time increments were reduced to promote accuracy in exercising the model. During this early period, the thermal dynamics of the system are changing rapidly because the hydraulic system is starting to transfer energy to the fluid, and more data points are needed.

    The columns labeled Pack loss and Boom loss represent the energy put into the fluid by the  pressure drops in the pack-eject and boom circuits, respectively. The columns labeled Q-HS and Q-Res are the total rates of heat transfer from the hydraulic system (excluding the reservoir) and the reservoir, respectively, for all heat transfer mechanisms—solar radiation, free convection, and forced convection.

    The last two columns show the change in fluid temperature from the last time period and the fluid temperature for the indicated time period, respectively.  The model calculates the change in temperature due to the energy input to the fluid, less the heat energy transferred from the fluid, during the prior time period and adds the temperature difference to the fluid temperature for the last time period to obtain the value shown.

    The table shows that the temperature of the modeled fluid exceeds 180°F early in the day. Operator breaks and down time at the dump/transfer station promotes cooling because convection removes heat from the hydraulic system and no pressure losses are produced.  However, internal energy is generated at such a high rate from pressure losses in the system during operation that the fluid remains at excessive temperatures for almost the entire day because the heat transfer rate from the fluid is insufficient for cooling it. 

    Effect of Heat on Seals

    Standard seal materials for normal industrial applications have maximum allowable temperatures to 250 or 300° F, depending on the actual compound. For most of these, temperatures from 250 to 300° F are allowable for only brief periods. For Buna-S, the temperature range goes to 225°F. (Higher-cost Viton seals can sometimes be specified for hydraulic components, but the maximum temperature for Viton is only 250°F.) 

    This analysis indicates that fluid temperatures higher than 300° F can be expected on hot days in such climates. This means that seals in the hydraulic components should be expected to soften during operation of the packer trucks.  As the seals soften, they will tend to extrude into the space between the parts they are sealing and, eventually, break.  Hydraulic fluid would begin leaking when the seal extrudes, and possibly catastrophic leaks would likely occur when a seal breaks.

    However, the deleterious effects of high temperature degrade more than just seals. It also degrades the hydraulic fluid. Data for Texaco Rando HD 46 were used as a typical fluid for use in such hydraulic systems. Texaco’s literature for this fluid shows properties up to a maximum temperature of 180°F. Literature for similar fluids of the same grade indicate operating ranges for No. 46 grade fluid of 32° to 160°F.

    Parker Hannifin Corp. recommends a maximum reservoir fluid temperature of 145°F. Higher temperatures can produce oxidation products (varnish), which can clog orifices, corrode metal surfaces, form sludge, and cause rapid wear of metal parts.

    Peter J. Weller, P.E., is a consulting mechanical engineer providing engineering and design services to industry and expert testimony services. For more information, visit www.peterjweller.com.

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    From hydraulicspneumatics Friday, May 6, 2016