370 Series Level Controller and Vapor Eliminator

Diesel fuel testing equipment

Recirculating Fuel and Efficient Bubble Elimination Increases Fuel Measurement Accuracy

In an attempt to measure actual fuel consumption, early designs of fuel measurement systems employed two flow meters; one would measure supply fuel and the other, return fuel. By subtracting the return fuel from the fuel supplied, a consumption rate was derived. This technique is subject to large errors—especially during idle or lower rpm settings.

Example, using two flow meters, each with nominal 0.5% measurement error, a supply rate of 100 lb/hr and a return rate of 90 lb/hr produces a potential error of 0.5 lb/hr and 0.45 lb/hr respectively. Combined, these become a potential error of 9.5% when compared to the actual 10 lb/hr consumed.

Max recommends a fuel measurement system that avoids these errors by recirculating the return fuel into a Series 370 Level Controller before returning it to the engine.


When plumbed in the Vapor Eliminator configuration, the Model 370 products remove bubbles from the fuel which would otherwise cause measurement errors as they pass through the flow meter. Bubbles may be caused by the low boiling point components in gasoline or by hot vehicle fuel lines. A design featuring a series of screens and a float mechanism effectively separates the vapors from the fuel. The Model 370-170-000 is offered for diesel consumption rates to 3500 cc/min, the Model 372-200-000 is specified for diesel consumption rates to 1000 cc/min. (gasoline flow rates are 50% higher) 

When plumbed in the Level Controller configuration, the Model 370 products serve as a vented, recirculation tank to collect return fuel and route it back to the supply side of the engine. A float-activated, precision valve opens to control the flow of "make-up" fuel into the Level Controller. This "make-up" fuel passes through the single Max flow meter, providing accurate measurement of the actual fuel consumed.
  • Internal plumbing reduces turbulent flow and consequent foaming.
  • Efficient venting of return fuel vapors.
  • Open to atmospheric pressure – eliminating back-pressure on the engine return line.
  • Smooth float action maximizes stability of instantaneous readings.
  • Models sized to consumption of 1.9 and 2.2 liters per minute, with recirculation rates of 2 and 3 liters per minute, respectively.


PDF icon 370 Series Fuel Measurement Accessories722.15 KB

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