Fluid Menu

Low Viscosity Liquids - Pelton

 

Introduction

 

Litre Meter specialise in the design, manufacture and supply of flowmeters.The unique Pelton wheel based meter design ensures an inherent reliability which has been proven in more than three decades of operation.The meters measure many diverse fluids such as acids, chemicals, fuels, demineralised water and hot fats at both low and high flow rates.Temperature ratings up 135°C and pressure ratings to 2000 bar are offered, meeting most industries flowmeter requirements.

Compliance

 

For EMC, Electro Magnetic Compatibility legislation, Litre Meter flowmeters meet the lowest emissions requirement of EN 50081-1 for the residential, commercial and light industry environment (defined as where power is derived from the public AC mains). They meet the highest immunity requirements of EN 50082-2 for measurement and control equipment in the industrial environment (where power is derived via independent transformer systems). The machinery and low power directives do not apply to our flowmeters.

Chemically Resistant Flowmeters

 

Meters with all-sapphire bearings and no metal parts have been developed to measure aggressive fluids such as sodium hypochlorite, sulphuric and hydrochloric acids. Volatile fluids such as toluene and vinyl chloride may be measured in hazardous (flammable) areas. For 'high purity' requirements, meters in 440 PFA are available. Less onerous service can be met with meters having economic materials of construction. These retain the excellence of the bearing system and the other performance features that Litre Meter flowmeters offer.

Specialists In Low Flow

 

Litre Meter developed the Pelton wheel principle as the best to achieve accurate measurements of low flows. The LM01 size meter, for example, measures from 0.01 to 0.25 l/min. The LM003 measures from 3 to 60 ml/min. The meter range meets the requirements of the nuclear and aerospace industries and other high technology applications. Lloyds Register of Shipping certify specific meters to ASME B31.3 codes.

Electronic Instruments

 

In addition to the flowmeter transmitters, Litre Meter offer a complete range of electronic instruments designed to meet most flow measurement and control requirements.

The Litre Meter Micro, multi-function microprocessor based unit, provides up-to-date linearisation and data communication facilities. The quality of the products are backed by a first-class professional applications engineering and sales service to assist in the selection of the most applicable equipment.

Turbine Assembly

 

A single turbine ring size is common to all Litre Meter flowmeters. The turbine rotor is based on a highly efficient 'Pelton Wheel' design. It is available in various chemically resistant materials such as PFA (Teflon)and PVDF. The rotor ferrites are sealed to make them non-wetted parts. Sapphire bearings are offered for maximum chemical resistance as standard. These provide a very low friction mechanically-robust bearing with long life characteristics.

The rotation of the rotor is sensed by an electronic system using the interaction of ferrites in the rotor tips with a pickup coil. No drag is imposed on the rotor which assists in the measurement of extremely low flows. This, coupled with the efficient Pelton Wheel design and low friction bearings gives the meter major advantages. The complete turbine ring assembly can be easily removed with the meter remaining in line if cleaning is required.

 

Full Flow

 

The original rotor specified in the Litre Meter patents is a straight-bladed Pelton wheel. This proven design still forms the heart of the present flowmeters. The very large blade area compared with the flow inlet port size produces an exceptionally wide range flowmeter which can measure very low flows. The flow through the inlet of the meter is accurately directed onto the rotor which rotates at a speed in linear proportion to the flow rate. A small sensing coil which is part of the meter's transmitter circuit detects the ferrites mounted in the rotor blade tips as they pass. The transmitter electronics provides a current-limited pulse output signal. The signal has good noise immunity and can be transmitted for more than 1000m without difficulty. Most LM Series meters have screwed 1/4" or 1/2"BSP connections.

 

Standard linearities: ± 2% of reading over top 90% of range; otherwise ± 0.4% FSD

 

High linearity: ± 1% actual within a 40:1 range using linearising electronics.

 

Repeatability: Better than ± 0.25% for 90% of range

 

Rangeability (turndown): From 50:1 to 280:1 at 1 centipoise

Orifice/Bypass

 

The MM Series meter has an similar turbine ring assembly and signal output but is designed for larger flow rates. It achievesthis by mounting the pelton wheel turbine ring assembly in abypass chamber across an orifice plate. Flow tappings on either side of the orifice cause a proportion of the flow to drive the pelton wheel rotor. The speed of the rotor and the resulting output pulses are proportional in a linear relationship to the fluid flowrate through the meter. The large turndown characteristics provided by the pelton wheel design are retained and each meter is calibrated down to approximately 2% of maximum flow.

MM Series meters up to MM30 (1 1/4") size are provided with screwed or pipe connections and MM37 (1 1/2") to MM300 (12") size meters are designed for mounting between flanges.

 

Standard linearity: ± 2% of actual over the top 90% of flow range. Otherwise ± 0.4% FSD

 

High linearity: ± 1% actual within a 33:1 range using linearising electronics

 

Repeatability: Better than ± 0.25% for 90% of range

 

Rangeability (turndown): Better than 50:1 at 1 centipoise