BRITISH & METRIC FLUID CONVEYING PRODUCTS

The Old Timer Part 18: Avoid unwanted intensification

The Old Timer

The Old Timer of Royal Oak, Mich., was a regular contributor to H&P years before we ever even heard of the internet. But most of his advice is just as useful — and interesting — today.

So rather than leave his wisdom printed on pages archived in our storage room, I pulled out issues from the late 1980s and early 1990s and have been reproducing relevant entries in this blog. Here is my 18th entry, which was originally published in the June 1989 issue:

Avoid unwanted intensification

Most hydraulics courses include an example to illustrate an intensification problem that occurs when holding vertical loads with a cylinder. Typically, such an example might specify a cylinder with 10-in.2 piston and 1-in.2 rod lifting a 5-ton load. A blocked-center directional control valve stops the cylinder in mid-stroke. The student usually is told that the piston has a small orifice drilled through it. (A more realistic condition is the inevitable leakage past worn piston seals.)

At the moment the valve stops the piston, gauge A reads 0 and gauge B reads 500 psi. What’s the new reading on A?

The force on the piston now is the load plus a pressure component generated by 500 psi acting on the 9-in2 annular area—or a total of 14,500 lb. A pressure of 1450 psi in the cap end of the cylinder is necessary to support this force.

When the pressure at A rises to 1000 psi, the pressure component increases to 9000 lb—for a total force of 19,000 lb. Gauge B now registers 1900 psi.

The ultimate question is, “How far will this intensification progression go? What will be the maximum pressure in the cap end of the cylinder?”

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Read more: The Old Timer Part 18: Avoid unwanted intensification 

Hydraulic hose maintenance: be proactive, not reactive

It’s often thought that hydraulic hose failure can’t be predicted, and as a fairly inexpensive component, many production managers accept failure as unavoidable. Equally, it’s common for hydraulics users to pre-emptively replace hoses that are still in safe working order, utilising unnecessary time and money. However, the low cost of the hose itself belies the considerable expense associated with oil clean-up and replacement, while a run-to-fail policy also fails to take into account the significant health and safety hazard posed by burst hoses. Yet, as we reveal here, there is always an indicator that a hose will fail, enabling maintenance engineers to act in time.

Hydraulic Systems

Hydraulic systems can contain as much as 2,000l of oil, which due to high pressures can completely drain out of a damaged hose within just 20 minutes. Even a small, pin-prick sized hole can quickly compromise an entire system as, due to pressures exceeding 100 bar or even 200 bar, a tiny hole can split or expand to the size of a golf ball within a very short space of time. Although many modern hydraulic systems sit within a bund to collect waste oil, bursts can be unpredictable. The oil may spurt out at an angle, missing the bund altogether and damaging surrounding equipment or worse – causing considerable and possibly life-changing fluid injection injuries to individuals.

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How To Avoid ‘Dieseling’ In Hydraulic Cylinders

I was recently engaged by a client to conduct failure analysis on a large (and expensive) hydraulic cylinder off an excavator. This hydraulic cylinder had been changed-out due to leaking rod seals after achieving only half of its expected service life.

Inspection revealed that apart from the rod seals, which had failed as a result of ‘dieseling’, the other parts of the hydraulic cylinder were in serviceable condition. The ‘diesel effect’ occurs in a hydraulic cylinder when air mixes with the hydraulic oil and explodes when pressurized.

Hydraulic Cylinder Maintenance

When a double-acting hydraulic cylinder retracts under the weight of its load, the volume of fluid being demanded by the rod side of the cylinder can exceed the volume of fluid being supplied by the pump. If this happens, a negative pressure develops in the rod side of the hydraulic cylinder. And this usually results in air being drawn into the cylinder past its rod seals.  The result of this is aeration — the mixing of air with the hydraulic oil.

As you have probably gathered, the term ‘diesel effect’ is a reference to the combustion process in a diesel engine.

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Read more: How To Avoid ‘Dieseling’ In Hydraulic Cylinders 

Fire-Resistant Fluids Need Unconventional Seal Materials

Water-based hydraulic fluids are widely used in oil and gas, mining, hot-rolling mills, and similar applications where the potential for fire could cause catastrophic consequences. The International Standards Organization (ISO) classifies fire-resistant, water-based hydraulic fluids into four categories:

Categories

  • HFAE, which includes oil-in-water emulsions, typically with more than 80% water content;
  • HFAS, which are synthetic aqueous fluids, typically containing more than 80% water;
  • HFB, which are water-in-oil emulsions typically containing more than 40% water; and
  • HFC (also known as glycol solutions, polyalkylene glycol solutions, and water glycols), which include water polymer solutions, typically containing more than 35% water.

HFC fluids (water glycols) are the most commonly used fire-resistant hydraulic fluids in and are increasingly being used instead of HLP hydraulic fluids in hydraulic oil and gas applications with a high fire risk. Certain sealing materials are proven and traditionally used with HLP fluids.

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Read more: Fire-Resistant Fluids Need Unconventional Seal Materials 

GROVE GRT8100, GRT880 ROUGH-TERRAIN CRANES

Rough Terrain Cranes

The GRT8100 and GRT880 rough-terrain cranes replace the RT890E and RT880E, respectively. The 90-tonne GRT8100 has a 47-meter boom and a maximum tip height of 49 meters. The 80-tonne GRT880 has a 41-meter boom. The GRT8100 has a hydraulic luffing jib that can be configured at lengths between 10 and 17 meters. A boom extension stowage system decreases erection and stowage time by 60 percent, the company says.

Both cranes have Manitowoc’s Crane Control System (CCS). An updated full-vision cab tilts to 20 degrees and also features a new ergonomic control arrangement including a tilting steering column, electronic joysticks, and a jog dial for simple CCS menu navigation.

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Read more: GROVE GRT8100, GRT880 ROUGH-TERRAIN CRANES 

Tough-Built Hydraulics Tackle Rough Terrain

Tough Built Hydraulics

Kalmar Global manufactures a wide variety of off-highway equipment, including the RT022 rough-terrain telescopic forklift. Compact enough to drive right inside a container, it features two-wheel, four-wheel, and crab steering modes for excellent maneuverability on the most challenging surfaces. With side-shifting forks for container loading, unloading, and a tight turning radius of just 30 ft., the RT022 is well-suited for lifting operations in tight spaces.

Specifications

The RT022 is powered by a 68-kW (91 hp) Perkins diesel engine, which drives DuraForce HPV pumps and HMV motors from Eaton Hydraulics, Eden Prairie, Minn.

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LANDOLL 900D TRAVELING TAIL TRAILER WITH HOSS SYSTEM, LIGHTING PACKAGE

LANDOLL 900D TRAVELING TRAILER

The 900D Traveling Tail trailer is equipped with the “HOSS” hydraulic operating system and a new Grote lighting package, giving the Traveling Tail both increased operational speed and a “High Visibility” lighting package that increases visual awareness and driver safety during night operations.

Operational speed increases with the HOSS system operating at 20 gpm, the company says. The control panel is located at chest height and allows other optional features to be installed directly into the panel.

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Read more: LANDOLL 900D TRAVELING TAIL TRAILER WITH HOSS SYSTEM, LIGHTING PACKAGE 

Tree Processor Comes Full Circle with Hydraulic Swivels

Southstar Equipment, a leading forestry attachment manufacturer based in Kamloops, B.C., Canada, designs and manufactures attachments that deliver efficient automated mechanized harvesting and processing for wood products. When Southstar engineers designed a full-rotation multi-tree processor, they needed to set the new logging attachment apart from others on the market. A 360° rotating head and the ability to accurately process multiple trees at once helped Southstar do just that.

Previous models of Southstar processors had a 340° rotational limitation. To implement the crucial 360° rotating head, Southstar partnered with United Equipment Accessories (UEA) on an electrical slip ring/hydraulic swivel combination assembly.

Benefits of Two-in-One Design

“Together, the combination assembly allows both electric and hydraulic power to flow without interruption throughout the full 360° rotation,” says Dean Flaig, Technical Sales Manager at UEA. The 20° difference between 340° and a continuous 360° makes a big difference. Because UEA’s combination assembly allows for full rotation, Southstar’s customers see improved efficiencies, decreases in snags, and less maintenance.

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Read more: Tree Processor Comes Full Circle with Hydraulic Swivels 

CATERPILLAR 6015B MINING SHOVEL

The company says fuel efficiency gains result from its proprietary integrated engine control technologies, a boom float feature that regenerates boom oil for reduced engine demand, an oil cooling system that’s independent of engine cooling, and regeneration of swing energy via its closed-loop swing system.

Technology

Cat automatic flow proportioning technology creates more efficient hydraulic pump utilization, reduced energy losses and increased fuel savings. Exclusive Cat Proportional Priority Pressure Compensating technology ensures that hydraulic flow is proportional, according to demands, so individual functions—boom, stick, and bucket—are automatically prioritized during simultaneous operations. This aids smooth, efficient operation and controllability. Pressure and flow compensation deliver only as much flow as needed. The result is reduced heat build-up and component wear.

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Read more: CATERPILLAR 6015B MINING SHOVEL 

CATERPILLAR 415F2 LOADER

The 415F2 Industrial Loader Tractor combines the basic design of the Cat 415F2. The backhoe­-loader purpose­-built components are designed for industrial ­loader applications, such as new pilot controls, three­-point hitch, and a box blade scraper.  A security key pad disables the engine, transmission and hydraulic systems at machine start­up until a pass­code is entered.

Functions

The standard three­-function loader valve uses mechanical controls, with single­-lever control for models with a general-­purpose bucket and two-­lever control for models with a multi­purpose bucket.

The five-­function valve for the box blade scraper uses low­-effort, pilot-­operated controls that feature a conventional operating pattern in a conventional control-­console location.

Technology

This differential lock can be activated with a floor­-mounted button or a button on the loader­-control lever. The standard-­shift, four-­speed transmission has a quick-­reversing, power­shuttle feature.

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Read more: CATERPILLAR 415F2 LOADER 

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