Preventing dirty-oil downtime

J.E. Myles Inc., a hydraulic systems distributor based in Troy, MI, worked with its sister company, Control Power-Reliance, to engineer the world’s largest six-axis transportation simulator back in 1996. Today, the simulator continues to run using the original hydraulic oil.

The simulator was designed to run five to six days per week, two shifts per day. The system included six high-speed servo valves that run up to 50 Hz.

J.E. Myles needed a 1,000+ gallon reservoir, and a cooling system to keep the oil temperature at 110°F or less. The simulator’s continuous operation was crucial — downtime had to be kept to an absolute minimum. With this in mind, the distributor specified that Parker KleenVents be installed on the reservoir to keep the hydraulic oil as clean as possible.

Even in the most sterile environments, constant airflow through the reservoir can raise the the Total Acid Number (TAN) of hydraulic oil, slowly degrading its properties and causing oxidation of the fluid. This, in turn, can lead to varnishing of system components and/or premature wear. Air is in fact one of the most detrimental hydraulic system contaminants. Containing moisture and metal particulate, it can condense inside reservoirs and fall into the oil as water. High ambient and operating temperatures, meanwhile, only serve to accelerate acidic build-up.

When the TAN exceeds a predetermined level, critical machines must be shut down, the oil drained and disposed of, and new oil purchased — a time-consuming and costly proposition that scheduled maintenance alone cannot prevent.

The KleenVent KV Series reservoir isolator could help ensure continuous equipment operation. KleenVents use an elastomeric bladder as a ‘lung’, where changes in gas volume in the reservoir can be contained and prevented from mixing with the outside air.

In operation, when the hydraulic reservoir is filled, the air on the top of the oil (Figure 1) goes into the KleenVent bladder. When the oil level in the reservoir goes down (Figure 2), it pulls the air from the bladder back over the top of the oil. This containment approach completely eliminates the potential of pulling in outside air. Instead, the atmosphere now acts against the outside of the bladder isolator, while internally the same air is continuously exchanged between the reservoir and the bladder.

This separation allows the system to operate normally, while preventing ingestion of airborne contaminants. Unlike conventional breather-vent filters, Parker’s reservoir isolator provides a positive separation without the possibility of clogging, making it maintenance-free. Importantly, with proper bladder material selection, KleenVents are compatible with virtually any type of hydraulic fluid

The J.E. Myles/Control Power-Reliance transportation simulator was put into operation in July 1996. At that time, the TAN of the 1,000+ gallons of hydraulic oil was 0.75. As of March 2011 — after 177 months and more than 620,000 hours of operation — the simulator continues to run using the original hydraulic oil.

“The TAN of the oil today is within 10% of what it was the day we purchased it, almost 15 years ago,” said Colin Myles, vice-president, J.E. Myles. “We’ve never changed the oil, thanks in large part to Parker’s KleenVents. Without them, we’d have purchased new oil at least three times by now.”

Myles added that the system has never experienced a servo valve or actuator failure — again partly attributable to consistently outstanding fluid cleanliness levels. He estimates between $1,000 and $5,000 as the potential cost to repair one of the simulator’s six 250-gpm servo valves, while repair of a single 50 KIP actuator — of which there are also six — would range from $3,000 up to $15,000.

“We would have likely repaired at least one servo valve and actuator to this point, had we not installed KleenVents from the start,” noted Myles.

By using KleenVent reservoir isolators, J.E. Myles has kept its simulator system free of airborne contamination and moisture that is usually introduced through a standard filler breather. As a result, filters are only needed to remove wear-generated particles, while varnishing of the servo valves has been non-existent.

The cost savings in hydraulic fluid, meantime, has been remarkable. Assuming an average cost of $18.00 per gallon for new oil, and an average disposal cost of $4.50 per gallon for old oil, the KleenVent solution has saved J.E. Myles more than $90,000 since 1996.

“The greatest benefit,” added Myles, “besides the cleanliness of the oil and the money saved, has been the uninterrupted system function we can count on day-to-day. Thanks to KleenVent, downtime due to dirty oil has never been a problem for us. IL

For more information, visit Parker Hannifin Corp. at www.parker.com/accumulator.

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