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On Flow Measurement F-0003

Measurement of Saturated Steam flow by V Cone Flowmeter

VM

Steam is widely used in different industrial processes for heat energy transfer, power source, sanitary flushing, etc. However, the precise measurement of such steam flow by existing measuring instruments involves several difficulties. Now, we Tokyo Keiso are able to offer a solution to the measurement difficulties of such application with our VM type Mass V Cone Flowmeter.

Difficulties in Steam Flow measurement with Volumetric Flowmeter

1. Pressure and Temperature variation

In general, flow measurement of steam by volumetric flowmeters theoretically results in measurement errors once such actual operating conditions as pressure and temperature vary from the design conditions. In actual steam line operation, pressure and / or temperature often fluctuate depending on the boiler's function and on steam consumption. This fluctuation results in measurement errors when volumetric flowmeters are used. To eliminate such errors, pressure and temperature compensation calculations are necessary.

The compensation is conducted by the following procedure:

Volumetric flowmeter, Temperature sensor and Pressure sensor are installed on the process line. These 3 different signals are sent to Control Room. A Flow Computer (to calculate compensation for these 3 factors) must be provided in the Control Room.

However, this flow compensation method has costly results:
 ・ The need for 3 different sensors means increased cost
 ・ As is the need for 3 separate wirings/cables from field to Control Room.
 ・ And the need for Flow Computer adds further to the cost.

Since steam flow measurement in the field by volumetric flowmeter has these measurement errors, the provision of this complex arrangement is inevitable.

2. Range ability
The other difficulty of steam flow measurement is "Range Ability". The consumption of steam may vary depending on "season". The difference of flow rate between summer and winter is rather large and one volumetric flowmeter cannot cover both "seasons".

3. Required straight runs for installation
Normally, flowmeters require straight run both for up and down stream for accurate measurement. In case of Orifice plate 20D for upstream and 10D for down stream are required.

4. Process Vibration
Process piping may often have mechanical vibration created by motors, pumps and other heavy electrical devices. This piping vibration may cause function error for flowmeters. Especially, it is pointed out that Vortex flowmeters may suffer such vibration seriously.

Conventional flowmeters and their measurement weaknesses

・ Orifice plates
Range ability, required straight runs, error caused by process change and pressure loss will be the main weak points.
・ Variable Area flowmeters (Rotameters )
Error caused by process change will be the main problem.
・ Vortex Flowmeters
Range ability, required straight runs, error caused by process change and effect of process vibration will be the main weak points.

Solution by VM type Mass V Cone Flowmeter

· What is V Cone Flowmeter ?

V Cone is, in theory, a Differential Pressure type flow sensor like Orifice, Venturi, etc. But, thanks to the patented unique flow restriction design, V Cone has the following advantages over the other types of differential pressure flow sensors:


Minimum straight runs
required for installation
Wide range ability
Low pressure loss

Fig.1

The detected differential pressure is output by a standard DP transmitter like in the ordinary orifice system.

· What is the special construction of VM type Mass V Cone Flowmeter ?

V Cone sensor, 3 way valve and differential pressure transmitter are assembled in one piece for easy installation in the field. By simply mounting the unit onto the process line and by connecting a two-core cable, flow measurement can immediately start up!


The assembled differential pressure transmitter is provided with integral automatic compensation function! This means that Steam Table is stored in the software of the transmitter and the change of operating pressure is automatically compensated according to the pressure data which is detected by the transmitter itself. Without any additional sensors, Mass flow measurement of steam, free from process changes, has now been achieved!

Fig.2
Examples of Successful Applications

· Precise and accurate steam flow measurement in magnetic tape production facility

A world famous magnetic tapes and floppy disc manufacturer in Japan is using steam for power source in a state-of-the-art cost-saving clean energy production system. The steam for the power source is produced by their Power Source Division and the cost of such steam is charged to the facilities where the steam is consumed. To cost the consumption charges, precise and accurate measurement of steam flow is absolutely critical as the pressure (temperature) of steam may vary depending on the load of process and simple volumetric flow measurement may not satisfy the requirement.

The manufacturer has installed VM type V Cone Mass flowmeters on all final lines as well as on the main steam line for proper cost sharing of steam consumption by the various facilities with results that completely satisfy Power Source Division's stringent requirements.

· High Quality Air Conditioning

Temperature control is the key to air conditioning. Accurate feeding of steam to air conditioning piping is a necessary condition! VM type V Cone Mass Flowmeter keeps watch on the mass flow of steam for accurate temperature control. We have plenty of supply records for Hospitals and large scale indoor sports stadiums for this application.

· Extraction processes in Food Industries

In food production processes, steam is sometimes used for extraction purposes. We supplied VM type V Cone Mass Flowmeters for:
  · Extraction of Coffee beans
  · Extraction of chicken bone soup
By the stable supply of steam to the process, the quality of the product and efficiency of production have been considerably improved.

These typical examples of trouble-free precise steam flow measurement by our VM type V Cone Mass Flowmeters have confirmed the superiority of this meter over all other commonly used existing types.

Catalogues and other descriptive and explanatory literature can be requested at:
overseas.sales@tokyokeiso.co.jp
(Kindly indicate clearly your postal address.)