Even the smallest hydraulic oil leak costs money. The cumulative effect of external leaks from hydraulic machines can cost industrial producers tens of thousands of nonbudgeted dollars annually.
Studies show that the replacement cost of a fluid can be five times more than the cost of the new fluid.1 Major cost factors attributed to external hydraulic fluid leaks on industrial machinery include:
- Replacement fluid expense
- Product spoilage
- Plant safety
- Health and environmental issues
Bijur Lubricating Corporation has introduced a fluid recovery system that can be used to manage leakage and track oil recovery volumes. The system also can measure recovered fluid rates and offers industrial plant operators a method to control and monitor escaping fluid rates on individual machines. Changes such as increased leakage provide early detection of potential hydraulic seal failures. Early corrective action results in substantial maintenance, repair and operation (MRO) savings.
Table 1. Accumulated Leakage - Typical Machine Case History
Table 2. Cost for a 55-gallon Drum of Hydraulic Fluid
Machine Leakage Costs and Typical ROI
Depending on design, application and age, hydraulic cylinders and rotating equipment shaft seals will produce varying amounts of external leakage. Today, higher oil prices and operating safety factors place greater emphasis on hydraulic fluid leakage controls. Weekly costs in wasted fluid and disposal expenses from leakage can range from $30 to $100 for typical petroleum or synthetic hydraulic oil (Table 3). Collecting oil leakage through a simple air-powered vacuum device can improve plant efficiency, along with associated cost savings (Table 4).
Operational Overview
The fluid recovery system consists of a series of collection tubes attached to individual machine collection points. Each tube connects to inlet valves mounted on the centralized collection reservoir. When recovered fluids reach a prearranged level, the reservoir becomes pressurized to transfer the liquid to a remote point for disposal or conditioning for reuse.
On a typical machine, the fluid transfer action (blow-down) occurs at a predetermined level in the collection reservoir. As seal wear occurs and leakage rates increase, the blow-down fluid transfer frequency increases. This fluid loss rate can be monitored, alerting machinery users to operational changes. This feature supports increased equipment reliability through:
- Early detection of potential failure of seals. Increased fluid leakage normally indicates seal breakdown. This helps prevent unscheduled equipment failure, costly repairs and downtime.
- Seal condition monitoring supports ongoing productivity.
When the oil is removed from the reservoir, the liquid level switch float returns to the low-level position opening the low-level switch contacts. The vacuum exhaust valve is de-energized to the normally open position, the outlet check valve closes and the vacuum valve is turned on. The recovery function resumes.
Note: During the blow-down mode, the recovered oil is normally transported through a single feed line to remote collection point for recycling, reuse or disposal. During this phase, appropriate in-line return filters should be utilized in the delivery tube to remove contaminants that may have entered the fluid.
Multiline Recovery Systems
Because the unit’s operating principle is based on an air-powered vacuum generated from a central source, for proper operation of multiple recovery point installations, it is important to size and arrange the recovery system network to maintain an equally balanced collection tubing network. In centralized multiline recovery systems, a vacuum condition will recover fluid from the easiest source. In order to maintain a consistent collection characteristic throughout the network, it is important to ensure that recovery line tubing diameters are properly sized and recovery tubing lengths are as equal as possible.
Figure 1. Fluid Recovery System
Fluid Recovery System Benefits
The collection system readily adapts to various machinery situations to control external fluid leaks. Gravity-fed and vacuum-assist models provide simple solutions to a wide variety of industrial leakage problems. These systems have been adapted to a broad range of industrial machinery to control hydraulic, lubricant and water-based metalworking fluids.
Recovery systems for air and oil mix droplets offer users unprecedented control of this popular method of lubrication of high-speed antifriction bearings. Air/oil mix droplets exiting from various delivery points are collected to a common reservoir and simultaneously separated to deliver clean filtered air, as well as recovered reclassified lubricant in fluid form ready for recycling and reuse.
Several stand-alone product packages are available to control and monitor the number of blow-down cycles. Utilizing a controller/totalizer device in conjunction with the fluid recovery device offers benefits such as:
- Reduction in product spoilage
- Elimination of large messy drip pans
- Less fluid losses - reduces topping-up expensive fluids
- Reduction in equipment downtime (for repairs and clean-up)
- Longer intervals between machine inspections
- Cleaner, safer machinery
These achievements support industrial plant manager objectives to operate an efficient, environmentally friendly, safe operating facility.
Operation Sequence of the Fluid Recovery System
Step 1. Start-Up Mode (Empty Reservoir)
Power-Up - Air inlet valve is energized to ON position. The low liquid level float switch is at open contact position at the bottom of the reservoir. The vacuum exhaust valve is in the OFF position and the vacuum valve is energized.
Step 2. Filling/RetrievALL Mode
Air flows through the vacuum generator and exits to the atmosphere through the vacuum exhaust valve. This action creates a vacuum condition in the reservoir. Oil is drawn in through the individual collection tubes (vacuum valves). In operation, vacuum ports are normally cycled to suit individual requirements.
As recovered fluid fills the reservoir, the liquid level switch float moves up and the low liquid level switch closes.
Step 3. High Fluid Level Mode
Recovered hydraulic oil enters the reservoir and the level switch float reaches the high-level position. The high-level switch contact opens. The vacuum valve is shut off and the vacuum exhaust valve is closed. This action causes the incoming air through the inlet valve to build up the pressure in the reservoir.
Step 4. Oil Recovery Mode (Blow-down Condition)
When the reservoir is pressurized, the recovered oil is forced out through the discharge outlet check valve.
Reference
1. Slater, K. (November-December 2001). Detecting and Managing Hydraulic System Leakage. Machinery Lubrication magazine.
