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Technical Guide
DAN-LIQ-Turbine Meter-TG-0807
August 2007
Page 6
TURBINE METER ROTOR AND BEARING DESIGN
The primary differences in turbine meter technology are in the design of the rotor and bearings.
The rotor is an assembly of up to twelve (in some designs this number is greater) blades locked into a hub, which rotates
on a bearing or bearings. For light liquid applications that require viscosities of 5 cSt or less, and specic gravities of less
than 0.75, the rotor does not normally need a rim (sometimes referred to as a shroud). For measuring the more viscous
liquids and in larger size turbine meters (i.e. 8” and above) a rim is tted to ensure sufcient rigidity in the rotor. A rim also
offers the advantage of higher pulse resolution; with a bladed rotor the number of pulses per revolution is limited to the
number of blades, and in a rimmed rotor the number of pulses per revolution corresponds to the number of buttons or
slots in the rim.
For intermittent duties on light, clean hydrocarbons that may be found at tank truck terminals, ball bearings may be used
for a rotor bearing. Proper design of rotors with ball bearings will use two ball races and a short axle upon which the rotor
is tted. Where space is constrained the ball races may be tted directly into the rotor hub. This design is particularly
suited to low and varying ow rate applications, and is utilized on the Daniel Series 1200 Liquid Turbine Flow Meter,
designed primarily for distribution applications such as load racks. In these installations, liquids handled are typically light,
rened products.
Pipeline applications often require continuous operation at xed ow rates. Here the design of the turbine meter must offer
sufcient longevity to minimize maintenance intervals. In these applications, tungsten carbide journal bearings are used,
which offer exceptional longevity. As tungsten carbide is extremely hard wearing, designs utilizing this sort of bearing are
often applied to more demanding measurement applications, such as crude oil.
It should be noted here that the limitations on viscosity are related to the rangeability of the turbine ow meter. As the
viscosity of the measured liquid increases, the K-factor variations at different ow rates increase. Thus to maintain the
linearity of the meter at the required level, as the viscosity of the measured liquid increases, the turn-down, or rangeability
of the meter must be reduced. So for typical pipeline applications, where the ow meter will operate at just one ow rate
(or a very limited range of ow rates) a turbine meter may be used to measure ows of high viscosity liquids. The Daniel
Series 1500 Liquid Turbine Flow Meter is designed for pipeline applications, and is equipped with robust internals suited
to continuous measurement of a wide range of liquids.
There may be a single hanger or hangers upstream and downstream of the rotor. In the Daniel Series 1200 Liquid Turbine
Flow Meter there is a single upstream support for the rotor, and in the Daniel Series 1500 Liquid Turbine Flow Meter there
are both upstream and downstream hangers.
Bearings may be either ball bearings or tungsten carbide journal bearings. Since ball bearings are used to provide
improved performance on low ow rates and on clean product, they are a reliable, cost effective solution.
The Daniel Series 1200 Liquid Turbine Flow Meter deploys a cantilevered twin ball bearing design. Utilizing a rotating
shaft on two ball bearing units, the Daniel Series 1200 Liquid Turbine Flow Meter is available in 1”, 1.5”, 2”, 3” and 4” line
sizes. For more demanding applications, a tungsten carbide journal bearing assembly is available as an option.
Lightweight bladed rotors of this type mounted on ball bearings are particularly suited to the intermittent duty cycles typical
in loading rack applications. The design application is limited to clean rened products. In the event that the turbine is
used on slightly dirty products, the use of tungsten carbide journal bearings is recommended. Tungsten carbide bearings
are extremely hard wearing and used in turbine meters on a range of applications from LPGs to crude oils.