Alliance Sensors Group
102 Commerce Dr
Unit 8
Moorestown, NJ 08057
Ph # 856-727-0250

www.alliancesensors.com

Co-located with CONEXPO-CON/AGG 2014, the largest international gathering place for the construction industries

HAWE Valves Assists Off-Road Motorsport Vehicles

HAWE’s reputation for long-lasting, durable products make them a perfcect match for this project. SG 1L – AKS valves were used for the racing vehicles. HAWE’s SG Directional Spool Valves allow up to 400 bar, 100 lpm and serves to control the oil flow and directional movements of the jacks. Since the valve system is entirely made up of steel the housing unit is resistant to pressure surges and leakages. This eliminates the chance of hairline cracks or other damages caused by the harsh desert conditions.

About HAWE Hydraulics North America:
Sixteen years ago North America was introduced to HAWE Hydraulik through its American subsidiary HAWE Hydraulics. Today, the partnership brings more than 60 years of German engineering and experience to North American mobile and industrial markets. HAWE provides integrated services that include design, manufacture, set-up, a distributor network, and local inventory. Based in Charlotte, NC, HAWE Hydraulics is positioned to respond quickly to service needs, as well as provide prototypes in a timely manner. Headquartered in Munich Germany, HAWE Hydraulik is an ISO 9001:2000 certified international supplier with a strong focus on supporting rapidly developing niche markets.

(Minneapolis, Minn.) – There’s no question the BP oil leak crisis takes engineering, thought and industry best practices. Intervention is rough according to James Miletich of Oceaneering’s ROV Division. “You’re always fighting something. It’s never easy,” he said.

Recently, hydrate ice crystals formed inside BP’s 40-foot-tall containment system aimed to capture leaking oil—and ultimately clogged the system. Hydrate gases crystallize like ice in cold waters and high pressure deep beneath the ocean’s surface.

Minnesota company Continental Hydraulics, in partnership with Jet Edge, Inc. and Chukar Waterjet, Inc. developed a solution to help fight the problem. The company’s DO8 valve was used to operate Jet Edge’s waterjet pump enabling the jet stream to blast away the hydrate crystals.

“The timeliness and schedule was intense—but we were pleased to deliver a modification to our product capable of withstanding the harsh undersea environment and enormous water pressure at a depth in excess of 5,000 feet,” said Continental Hydraulics general manager Jeff Brandt.

Jet Edge’s custom engineered waterjet intensifier pump was dropped into the sea to power a robot-operated waterjetting lance— eliminating the hydrates. This equipment is the first-known waterjet system capable of operating in water depths in excess of 5,000 feet, opening a new frontier for waterjet technology.

Chukar Waterjet, Inc. general manager Bruce Kivisto said, “We worried about 2300 pounds of force and the harsh exposure to that valve. Continental Hydraulics recognized the importance, the challenge and delivered a critical component to our success.”

Kivisto provided onsite application and engineering services throughout the project, recently returning from several weeks aboard a boat just 50 yards away from the Discoverer Enterprise. He says the solution appears to be working and will continually be monitored.

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Continental Hydraulics of Savage, Minn. is a manufacturer of high performance hydraulic pumps, valves and power units. Their products are used in some of the most severe conditions and their reputation for superior durability and performance continues to grow. The engineering staff at Continental is continually at work to improve current products and develop new fluid power technologies. In addition, Continental Hydraulics specializes in response time and delivery for challenging custom orders. For more information, visit www.continentalhydraulics.com.
 

GPM Hydraulic Consulting, Inc.
Box 1376
Monroe, GA 30655
(770) 267-3787
www.gpmhydraulic.com

Funny Noises

By Jack Weeks

Not long ago on a consulting job, I noticed a loud hissing sound coming from a machine (not the machine I had been called to help diagnose). I asked the man I was working with about it and he said, "It's done that as long as I've been here. I guess it's supposed to sound like that - the machine works fine.". But it didn't sound normal to me. Looking a little more closely, I noticed a very large, relatively new heat exchanger installed on the machine. The man I was with explained that the machine used to overheat, so they installed a larger heat exchanger and that fixed the problem. Watching and listening through a full cycle of the machine, I noticed that the hissing sound was much louder at idle than while the machine was running. Placing my hand on the relief valve, I found that it was so hot I could not keep my hand on it. The problem was obvious - at some point, someone turned up the pressure on the pump compensator and it was now adjusted above the system reliefvalve setting. The pump was operating at full stroke all of the time. Any flow not being used by the machine would dump across the relief valve. I suggested that he reduce the setting on the pump. I could tell that he didn't really want to, because he was afraid the machine would stall. So I told him to wait until the machine was idle again, then turn it down just a quarter turn. Once the machine was in an idle condition, he made the quarter turn counterclockwise on the compensator and, with a puzzled look on his face, noticed that the pressure reading on the gauge did not change. He made another
quarter turn. Still no change. Then another and another. "I don't think this valve is working - turning it has no effect on the pressure.". But I could still hear the relief valve dumping so I explained to him that the system pressure was currently being determined by the relief valve, not the pump compensator. After approximately one and one-half full turns of the compensator adjustment, the hissing sound stopped. The gauge pressure began to drop. I had him stop when the pressure on the gauge was about 250 PSI below where it had started. The machine was noticeably more quiet. "When it starts back, I don't think it will work without stalling now that we have the pressure this low.". I said,
"Let's see.". When the machine began to cycle again, not only was it quieter than it had been, but the actuators were moving faster than they had before. I also told him that the current draw from the electric drive motor would likely be considerably less than before, too. The original heat problem had never really been addressed, only one of the symptoms had been masked.

This is by no means an isolated incident. Hydraulic machines simply do not make unusual sounds unless something is wrong. Just because the machine still appears to be functioning normally does not mean that it needs no attention. And a strange sound coming from the machine is often one of the very first signs of impending trouble. It has always been amusing to me how the same person who would take his car immediately to a mechanic if he heard a strange sound will ignore unusual noises in a multimillion-dollar hydraulic machine. Of course, there is no such thing as a silent machine. All industrial machines make noise. But sound is a form of energy and any unusual sound is, at the very least, a waste of some of the energy applied to the machine. There are hundreds of abnormal sounds a machine may make and an exhaustive list of every possible one could probably
fill a book. All of them can mean trouble, but in a hydraulic machine, a few of them are harbingers of serious issues that can cost a lot of money in very little time.

Relief Valves and Other Pressure Controls

Relief valves, for the most part, are designed to open only when something is wrong. Typically they are installed to keep system pressure from reaching dangerous levels With only a few exceptions, hydraulic machines are not designed to dump across their relief valves continuously. The hissing sound described above and a significant temperature gain across the relief valve are the most obvious indications that a relief valve is dumping. Heat is also a form of energy, so when a relief valve dumps a corresponding increase in current draw will usually be indicated on the electric drive motor. The excessive heat will not only waste energy but will also degrade the hydraulic oil. Most relief valves are set well above normal operating pressure, so when they are dumping the system pressure is usually higher than normal. This causes excessive wear all over the machine. If left
unchecked, shock spikes attack hoses, fittings, pipe clamps and seals. Mechanical wear to bushings, bearings, supports and connectors is also accelerated. Other pressure controls, such as reducing valves and counterbalance valves are often intended to be open regularly. But this doesn't mean they should always make excessive noise. A whistling sound or erratic hissing often suggests that they are improperly adjusted or stuck open. A good rule of thumb is if it doesn't sound right, it probably isn't. Slamming of actuators, stalls and excessive heat generation are the early symptoms of problems with these valves.

Pump Cavitation

A pump that is cavitating makes a steady, high-pitched whining sound. Since the sound is steady and does not reflect changes in the movement of the machine, it is often confused with bearing wear in the pump. Often a pump is replaced unnecessarily because it is cavitating. Cavitation is caused when the pump is trying to deliver more oil than it can draw into its suction line. This may be because the oil is too cold and the viscosity is high or because the drive motor has been mismatched and is turning the pump too fast, but most of the time cavitation is caused by some blockage in the pump suction. Usually this is the result of a plugged suction strainer or filter. Naturally, when a pump is
replaced, its suction filter element is changed or its suction strainer is cleaned while everything is apart. The cavitation stops when the new pump is installed, but actually it was the cleaning of the strainer or the replacement of the suction filter element that stopped the cavitation.

In addition to the steady high pitched whining sound, another symptom of cavitation is a reduced flow from the pump, which will result in a reduced speed of the machine. Obviously, a pump can deliver no more oil than it can get into its suction line. The pump will destroy itself if the cavitation is not addressed.

Pump Aeration

Often confused with cavitation because of its similar sound, aeration occurs when outside air enters the suction side of the pump. The pressure in the pump suction line is below that of the surrounding atmospheric pressure, so a leak will result in air coming in, not hydraulic fluid coming out. It can be distinguished from cavitation by its somewhat more erratic whining sound. The sound of cavitation is from the implosion of air molecules suspended in the oil. Since the molecules are distributed very evenly throughout the oil, the sound of cavitation is very steady. But the amount of air that leaks into the suction side of a pump is heavily dependent upon the flow of hydraulic oil. The sound will
therefore change as changes occur in the machine. It will also likely be accompanied by a sound similar to gravel or marbles rattling around inside the pump. If you can view the oil in the reservoir (most reservoirs have screens and baffles that get in the way of seeing the oil) you may also note some foaming of the oil. If a pump is allowed to aerate it will wear rapidly. But beyond damage to the pump, the rest of the hydraulic components will also be at risk. Aerated oil causes a number of
problems. When air is in the line, the machine will perform sluggishly (think about the last time you had air in the brake lines of your car). Air viscosity is well below that of oil. The reduction in viscosity will result in leaks, faiure to lubricate and heat problems. Air also becomes somewhat unstable at the high pressures hydraulic machines are operated, so corrosion and seal damage are likely. Air that enters the suction line probably also brings with it a host of contaminants to damage components.
If a leak in the suction line is suspected, squirt oil along the line. If aeration ceases briefly, you have found your leak. A worn shaft seal on a fixed displacement pump can cause it to aerate. Spray some shaving cream around the shaft seal and see if holes are drawn into the foam. Sometimes there is no float switch to shut the machine down when the oil level is too low. If the level of the oil gets too close to the suction strainer, a vortex will develop drawing air into the suction line along with the oil. Aeration can also be caused by the wrong shaft rotation or by improperly aligned couplings.

Directional Valve Noise

For the most part, directional valves should operate quietly - no more than a faint "click" on very quiet machines. The small amount of noise a directional valve makes is almost always completely drowned out by the rest of the machine. If you can hear a directional valve spool shift, chances are very good that there is a problem. If the pilot chokes are improperly adjusted on a two-stage directional valve, it will audibly slam when it shifts. The spool can easily be damaged, but the greater issue is the shock it introduces to the machine. Sudden movement of the valve spool causes shock throughout the machine and the weaker points of the system will suffer. Adjust the pilot chokes for smooth shifting of the spool and greater component longevity.

Cylinder Noise

Cylinders should move with almost no noise. If a cylinder makes noise, it may be binding or slipping. A bent rod will wear seals and mechanical linkages rapidly. Slippage degrades the performance of the machine and sends contaminants from the resulting worn seals out to other components. A noisy cylinder should be rebuilt or replaced as soon as possible.

Hydraulic Motor Noise

Hydraulic motors can make many of the same noises as hydraulic pumps. Just as pumps can aerate and cavitate, so can motors. And the same results will develop. A motor that is cavitating will destroy itself rapidly. This usually occurs on motor drives that have loads that can be overcome by gravity, causing the load to "run away". A meter out flow control or brake valve can correct this.

Listening to a machine and paying attention to the sounds it makes can pay off in large dividends by catching problems early before they become outages.

Jack Weeks entered GPM’s organization in January of 1997 as a CAD draftsman and hydraulic instructor. He has trained thousands of electricians and mechanics in Hydraulic Troubleshooting methods. His computerized animations have made GPM's presentations and training CD's the recognized leader in the industry. He received his education from the Georgia Institute of Technology School of Electrical Engineering and the Department of State Foreign Service Institute. Jack is an experienced draftsman and taught telecommunications equipment operation and repair for the Central Intelligence Agency at American embassies overseas.
 

GPM Hydraulic Consulting, Inc.
Box 1376
Monroe, GA 30655
(770) 267-3787
www.gpmhydraulic.com

Floating Cage Pressure Controls

Pressure control is a major factor in the design and operation of safe, efficient and reliable hydraulic systems. Limiting the operating pressure to prevent damage to hydraulic components and other expensive equipment due to the resultant forces is one of the most important functions of pressure control valves. Pressure control valves may also be used to control sequence of operations, maintain critical holding forces, and prevent loads from "running away" due to the effects of gravity.

Types of Pressure Controls

Pressure controls are typically 2-way or 3-way valves, which are either normally closed (non-passing flow) or normally open (passing flow). The majority of them are infinite positioning, which means they can assume an infinite number of positions between their fully open and fully closed positions, depending on flow rates and pressure differentials. Some pressure controls are also available as pressure breaker valves, commonly referred to as kick-down valves. These valves are only two position, and are either fully open or fully closed. They open or close at a pre-determined pressure, set by the spring, then reverse their position when pressure to the valve is reduced to near zero.

There are four common types of pressure controls, three of which are discussed in this article: reliefvalves, pressure-reducing valves, sequence valves and counterbalance valves.

Relief Valves

The relief valve is the safeguard that limits maximum pressure in a system by diverting flow back to the tank when the valve’s setting is reached. Relief valves are normally closed, while, in contrast, pressure-reducing valves are normally open. Various types of relief valves include: direct acting, differential area, piloted and bi-directional.

Pressure Reducing Valves

Pressure reducing valves are used to reduce pressure in certain parts of a hydraulic circuit that may not be able to withstand the maximum system pressure established by the relief valve. With a pressure-reducing valve in the system, pressure can be reduced to an actuator downstream of the valve, without affecting the pressure in the rest of the system. Pressure-reducing valves are normally open, and are available in 2-way (non-relieving) and 3-way (relieving) types.

Sequence Valves

As its name implies, a sequence valve causes operations in a hydraulic circuit to take place in a given sequence, without the use of electrical switches and controls. Sequence valves can be normally open or normally closed, depending on the application in which they are used, but are typically 2-way normally closed valves, and are either internally or externally piloted. Some sequence valves are 3-way, and can be normally open or normally closed.

Counterbalance Valves

Counterbalance valves are used when there is a need to control a load. They maintain a set pressure opposite of the load, to keep it from free falling. They may also serve as a full-flow relief valve. Pleaseread our article on Counterbalance Valves for more information.

The Problems

Due to the nature of most cartridge-type pressure control valve designs, they typically require a very precise forming of the valve cavity to ensure reliable operation. If the valve cavity is not machined within required tolerances, the valve tends to bind against the walls of the valve cavity. This can cause distortion of the cage and subsequent valve failure due to binding or sticking of the spool or poppet. Often, the cartridge valve is removed, assumed to be defective, and a different valve is installed in the cavity with the same results.

After a number attempts with different valves it may be determined that the cavity must be reworked to solve the problem. It should be noted, however, that reworking a cavity might also create another problem in that the cavity may become oversized, and will not provide enough squeeze on the o-rings to ensure a proper seal.

Another problem with cartridge type pressure controls is that they are often used in an environment that is prone to significant changes in temperature. This causes thermal expansion and contraction of the manifold and valve parts. Valves with a minimal margin of concentric clearance between the cage and the cavity may function properly with cold oil, but when exposed to hot oil, will experience binding and sticking failures because of the thermal expansion of parts in the hot fluid.

And last, but certainly not uncommon, over-torqueing the cartridge into the cavity during installation is another problem that will cause a valve spool or poppet to stick. Naturally, it is desirable to torque the cartridge into the manifold as much as possible to prevent it from backing out.

The Solution

The patented floating cage concept, designed by Command Controls Corp. of Elgin, Illinois solves the age-old problem of valve spool binding in pressure control valves caused by cage distortion. The floating cage, used in many of Command Controls’ flow controls, allow the cartridge to be flexible enough to conform to the contour of the valve cavity independently of the cartridge valve threads. This allows the cartridge to fit into the cavity without putting any side load on the valve, even in
cases where the cavity may be non-concentric or out-of-round, thereby allowing the spool to move freely without binding. Distortion of the cage, due to the effects of thermal expansion, is also eliminated by the floating cage design.

In the floating cage concept, since the retainer and cage are not physically connected to each other, torque applied to the threads when installing the cartridge in the manifold is not transferred to the cage. This yields another side-benefit: Command Controls floating-cage cartridges can be torqued into manifolds with higher torques than most other cartridge valves, and as such, are less likely to vibrate loose and cause external oil leakage. The floating cage design, along with other unique designs and innovations, put Command Controls’ cartridge valves on the leading edge of cartridge valve technology.
- - -
Written by Connie Kosarzecki of Command Controls Corp., Elgin, Ill. Kosarzecki has worked in the fluid power industry since 1958. Command Controls Corp, established in 1993, manufactures a complete line of state-of-the-art, highpressure (5,000 psi/350 bar), high-performance, screw-in, cartridge-type, hydraulic control valves and manifold systems for the fluid power industry. For more information, please visit www.commandcontrols.com.

Rexroth Hydrostatic Regenerative Braking System (HRB) Makes Commercial Vehicles Up to 25 Percent More Economical

Rexroth hydrostatic regenerative braking system (HRB) reduces fuel consumption by up to 25 percent and can be retrofitted as an add-on system even in vehicles without hydraulics.

Hydrostatic regenerative braking system (HRB) stores brake energy in a hydraulic pressure reservoir and relieves the load on the main drive when the vehicle is accelerating – potentially reducing fuel consumption by up to 25 percent.

(Bethlehem, PA - www.boschrexroth-us.com) Bosch Rexroth’s hydrostatic regenerative braking (HRB) system includes a hydrostatic hybrid drive which uses the considerably higher performance of hydraulics compared with available batteries to substantially reduce fuel consumption even in heavy commercial vehicles.

When the driver presses the brake pedal, a hydraulic unit integrated in the drivetrain presses the hydraulic fluid into a high-pressure reservoir. The resulting resistance makes the vehicle decelerate. When accelerating, the hydraulic pressure reservoir is controlled electronically to release the pressure and it relieves the load on the diesel engine. As a result, the engine consumes less fuel, generates less exhaust gases, and functions more quietly.

The compact Rexroth HRB is ideal for use in various commercial vehicles. The HRB can be integrated and even retrofitted in the chassis as an add-on system, without major modifications.

The system reduces fuel consumption by up to 25 percent in vehicles used for very short distances such as urban buses, garbage trucks, fork lift trucks, or delivery vehicles driven in city traffic. Fuel consumption can also be reduced considerably in other commercial vehicles and trucks used for intercity service.

Each time a driver brakes, the HRB system stores energy which would otherwise be lost. The hydrostatic hybrid drive functions almost maintenance-free and wear-free compared with electric hybrid drives. For example, it is not necessary to regularly change the battery. In addition, the HRB also improves the acceleration of the vehicle. The additional drive energy allows vehicles to be equipped with smaller diesel engines and therefore further reduce fuel consumption and emissions.

All Rexroth HRB components are based on standard components from the manufacturer's current product portfolio. Prototypes of the Rexroth hydrostatic hybrid drive are currently being tested in on-road vehicles.

Bob and Dan's "boring" adventure

Cutting two eight-mile subway tunnels through varying Santa Monica Mountain rock formations is a dirty business. But someone had to do it.

 

Construction & Tunneling Services, Inc. (CTS), Kent, WA, an established design engineer and supplier of mechanical excavation equipment for the construction and mining communities, has kept two tunnel boring machines (TBMs) over 25 years old in service with the help of Bosch Rexroth.

The two TBMs were used by specialty underground contractor Traylor Bros., Inc., of Evansville, Indiana, on the Red Line Metro project owned by the Los Angeles County Metropolitan Transport Authority.

The Red Line Metro project required the construction of two 12,500-meter subway tunnels traversing the Santa Monica Mountains near the famous Hollywood sign. The final tunnel was a cast-in-place concrete lining of 5.44-meter diameter, so the job required two tunnel boring machines with a bore diameter of 6.3 meters.

CTS had to engineer and remanufacture two existing TBMs, resizing them with new cutterheads and shields and adding a hydraulic drive, taking advantage of Bosch Rexroth's broad technical product line.

"Hydraulic components consisting of pumps, motors, and valves were integrated with custom gearing and specialty hydraulic cylinders to provide the bulk of the critical pieces that the tunnel machine requires to operate at its peak," said Dan Nowak, CTS president. "Our experience with this job reaffirmed what we have known from previous work with Bosch Rexroth - they make good products that fit in major areas of machinery design, they understand how these parts perform and where they should be applied for best results. I don't think you will find an operating tunnel machine that doesn't have a Bosch Rexroth part on it."

The job was not without surprises. The first reach of these tunnels traversed soft rock, then encountered a soil-like material, almost plastic in places. Other materials included squeezing shales, sandstones, conglomerates, and granodiorites.

"The opinion of both the operating contractor and the CTS staff at the end of the job was that without the variable speed features and the higher torque capacity offered by the Rexroth hydraulics, the project would not have had such a mechanical success," according to Nowak.

If you've got a mountain of dirt to uncover and an unyielding deadline to meet, talk to the people with big ideas and the brawn to back them up. Bosch Rexroth.

Bosch Rexroth Corporation
2315 City Line Road
Bethlehem, PA 18017-2131
Telephone (610) 694-8298
Fax (610) 694-8339