Hoffman Media EDD-4C manual Theory of Operation, Hourstime Elapsed

Section 4: Theory of Operation

General

The Dripmaster is a gravity-based oil lubrication system.

The common needle valve fed from an oil tank does not provide any regulation of the drip rate—the rate varies in response to variations in temperature (day versus night and time of year) and changes in the tank oil level (hydrostatic pressure). Another cause of rate fluctuation is temporary valve blockage.

The Dripmaster performs as an automatic needle valve that regulates oil flow (Figure 8).

Elapsed time (hours)

				Drops per minute												Drops per minute
0	20	40		60	80	100	120	140	160	180	200		0	20	40	60	80	100	120	140	160	180	200
0													0
2												(hours)time	2
4													4
6												Elapsed	6
8													8
10													10
12													12
			Needle Valve Dripper														Dripmaster

Figure 8: Common Needle Valve compared to Dripmaster

The components that make this possible are described below.

The servo motor regulates the needle valve aperture according to the preset drip rate value. A photoelectric sensor detects the drips and reports the drip count to the control circuitry. The control circuitry sets the mode of operation and generates the alarms and drip count information to the SCADA interface.

The Dripmaster EDD-4C incorporates a specially-designed needle valve connected to a servo motor which automatically compensates for rate fluctuations. The compensation magnitude is defined by the control circuitry. For example, if the drip rate set point is 40 drips/minute, and the drip rate drops below that level for any reason, the servo motor that attaches to the needle valve opens it to increase the drip rate to maintain 40 drips/minute. Conversely, if the drip rate exceeds the set point, the servo motor closes the needle valve to maintain the set point value (Figure 9).

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