One of the most interesting historical uses for oval gear meters was to detect the height of periscopes in submarines.
Hydraulic oil was used to move the top portion of the periscope up and down. The precise amount of oil passing through the lift mechanism was correlated to the exact height of the periscope. Accuracy was imperative.
Fast forward to modern process machinery. In paper machines, the inherent accuracy of oval gear metering technology can help to maintain steady flow of lubrication oil to multiple bearings. The biggest advantage over variable area flow meters in such applications is that oval gear meters are unaffected by temperature related viscosity fluctuations. During machine start-up, thicker cold oil will push the float in a variable area flow meter higher than after the oil warms up and the viscosity drops. This results in different flow indications depending on oil temperature. Experienced operators know that consistent and accurate monitoring of lubrication flows to individual bearings can help keep machines operating optimally to reduce downtime. Robust oval gear meters are ideally suited to challenging and variable operating conditions.
Oval gear technology - so how does it work? The basic operating principle of oval gear meters is positive displacement; measuring flow by counting the rotation of two meshed oval shaped gears in a sealed housing. Connected in-line with the process flow, fluid moving through the meter housing causes the meshed gear pair to rotate. Each rotation represents a fixed volume of fluid moving from the inlet to the outlet of the meter, regardless of the viscosity of the fluid. An inductive proximity sensor generates a pulse for each half rotation of the gears. Pulse counts per interval of time (typically 5 seconds) are retained in control systems for tracking purposes, providing historical flow information, trending, and high/low flow event info. Note, however, that oval gear meters are used to measure process flows and should not to be confused with oval gear pumps which are used to move fluid through a process.
Summary of advantages in a real operating environment
INSENSITIVE TO VISCOSITY CHANGES - The key advantage of oval gear-based lubrication monitoring systems is that oval gear flow meters are insensitive to viscosity variations over a wide range, resulting in consistent and accurate measurement.
QUICK VISUAL INDICATION - The transparent cover on the oval gear housing provides an immediate visual cue whether oil is moving through and the speed of spinning indicates how fast. Most proximity sensors are also equipped with an LED indicator, making it easier to verify speed of rotation from a distance.
CONSISTENT LUBRICATION & MEASUREMENT - Delivering consistent lubrication to all points lowers the likelihood of starving a bearing. Multiple alarm set points for high flows, low flows or absence of flow can be programmed into comprehensive monitoring systems. Trending and event info are retained for analytical process optimization purposes.
HOW CAN ESKO HELP?
ESKO Pacific is pleased to offer both small flow and large flow oval gear meters for installation in lubrication systems. Single manifold inlets, LED indicators and banked configurations are possible. Trogamid, aluminum, brass and stainless steel components are designed to withstand challenging operating environments. The experts at ESKO can design a system incorporating specific numbers of meters, various combinations of sizes, and flexible configurations which are mounted in custom lubrication panels with electronic monitoring stations.
Source: ESKO Pacific