Flow Measurement

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Specialty Gases and Equipment

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Variable Area Flowmeter
Models Available

How They Work

Flowmeters are used in fluid systems (liquid and gas) to indicate the rate of flow of the fluid. They can also control the rate of flow if they are equipped with a flow control valve.
Rotameters are a particular kind of flowmeter, based on the variable area principle. They provide a simple, precise and economical means of indicating flow rates in fluid systems.
This variable area principle consists of three basic elements: A uniformly tapered flow tube, a float, and a measurement scale. A control valve may be added if flow control is also desired.
In operation, the rotameter is positioned vertically in the fluid system with the smallest diameter end of the tapered flow tube at the bottom. This is the fluid inlet. The float, typically spherical, is located inside the flow tube, and is engineered so that its diameter is nearly identical to the flow tube's inlet diameter.
When fluid —gas or liquid — is introduced into the tube, the float is lifted from its initial position at the inlet, allowing the fluid to pass between it and the tube wall. As the float rises, more and more fluid flows by the float because the tapered tube's diameter is increasing. Ultimately, a point is reached where the flow area is large enough to allow the entire volume of the fluid to flow past the float. This flow area is called the annular passage. The float is now stationary at that level within the tube, as its weight is being supported by the fluid forces which caused it to rise. This position corresponds to a point on the tube's measurement scale and provides an indication of the fluid's flow rate.
	One way to change the capacity, or flow range, of a rotameter is to change the float material, and thus its density, while keeping the flow tube and float size constant. Floats which are made from less dense materials will rise higher in the tube and therefore will yield lower flow capacities for the same diameter flow tube. Floats made from more dense materials will rise less thereby yielding higher flow capacities. Relative flow capacities for some common float materials are shown in Figure 1.
	Another way to change the capacity is to change the diameter of the flow tube and the size of the float.

Selecting The Right Flowmeter Size

There are certain factors which affect the measurement of a fluid's flow rate with a rotameter. The fluid's temperature, pressure and specific gravity all impact gas flow measurements.

Flow capacities (ranges) for the flowmeters described in this catalog are given for air at standard conditions --- 14.7 psia (101.3 KPa Abs) and 70°F (21°C). Sizing a meter for a gas other than air, or for your specific application pressure and/or temperature, requires that you first determine the equivalent flow capacity in air at standard conditions. Once determined, the flow capacity tables in this catalog can be applied directly. Reference Scale tables can be requested for each flowmeter ordered which will provide conversion to your desired fluid or conditions.

For your convenience, Table 1 provides correction factors for gases other than air at standard conditions. Call our Technical Service Line at (800)544-1658 if you require further assistance in sizing a rotameter for your particular application.

Table 1. Flow Rate Factors For Gases Other Than Air
To estimate which flow tube should be purchased when measuring the flow of a gas other than air, multiply the flow rate desired by its factor below to find the air flow equivalent. The flow tube whose range (capacity) covers this flow rate should be the one purchased. Be sure to keep units consistent. Air Equivalent= Gas Flow Rate Desired x Factor. These factors assume standard operating conditions. Temperature 70°F/21°C; pressure 14.7 psia (101.3 K Pa Abs).

Gas	Factor	Gas	Factor	Gas	Factor
Acetylene	0.95	Halocarbon-11	2.18	Hydrogen Chloride	1.13
Air	1.00	Halocarbon-12	2.05	Hydrogen Sulfide	1.08
Ammonia	0.77	Halocarbon-13	1.90	Isobutane	1.42
Argon	1.18	Halocarbon-13B	2.27	Isobutylene	1.39
1-3 Butadiene	1.37	Halocarbon-14	1.74	Methane (Natural Gas)	0.75
Butane	1.42	Halocarbon-21	1.89	Methyl Fluoride	1.09
1-Butene	1.39	Halocarbon-22	1.73	Monomethlamine	1.04
Carbon Dioxide	1.23	Halocarbon-23	1.56	Neon	0.83
Carbon Monoxide	0.98	Halocarbon-113	2.54	Nitrogen	0.98
Chlorine	1.57	Halocarbon-114	2.43	Nitrogen Dioxide	1.60
Cracked Ammonia	0.54	Halocarbon-116	2.18	Nitrous Oxide	1.23
CycloPropane	1.21	Halocarbon-115	2.31	Oxygen	1.05
DiFluoroethane	1.51	Halocarbon-142B	1.86	Propane	1.23
Dimethyl Ether	1.26	Halocarbon-152A	1.51	Propylene	1.21
Ethane	1.02	Helium	0.37	Sulfur Dioxide	1.50
Ethylene	0.98	Hydrogen	0.26	Sulfur Hexafluoride	2.25

For other gases or for non-standard temperatures and pressures, call our Technical Service Line at (800) 544-1658

Note that flowmeters calibrated at standard conditions with a valve on the inlet, readings on the tube are correct provided that the outlet pressure is close to atmospheric. When the valve is on the outlet, readings are correct if the inlet gas pressure is equal to the pressure for which the tube was calibrated.

Flowmeter Measurement Scales

Depending upon the model, a flow-meter's measurement scale can be either direct reading or in reference scale units.

Direct reading tubes are straightforward. The measurement scale on each of these tubes reads actual flow at standard conditions in a choice of English or Metric units. Tubes with direct reading scales include the following series' flowmeters:

FM-1000; FM-1100; FM-1127; PG-1000; PM-1000; VM-1000

Reference scale tubes, on the other hand, provide a uniformly calibrated scale in arbitrary millimeter (mm) units. Obtaining actual flow rates with these tubes requires the use of a reference scale flow correlation table (available from Matheson) which relates the mm scale reading to an actual flow rate. Reference scale tubes are useful when measuring flow rates for gases other than air and/or for non-standard conditions. Tubes with reference scales include the following series' flowmeters:

FM-1050; TF-1000; TF-1050; Shielded SF Series

A sometimes confusing matter in flowmeter size terminology is that variable area flowmeters are often defined by their measurement scale length, that is, the distance between the zero and full scale marking. Scale length is typically indicated in millimeter (mm) units. The FM-1050, for example, uses a 150mm tube and the FM-1000 uses a 65mm tube. Note that this scale length has no relationship at all with whether the flowmeter is a direct reading or a reference scale tube.

Flowmeter Calibration And Services

There are many formulas available, which calculate the flow of a fluid through a variable area flow-meter for which it is not calibrated. Moreover, these equations are used to generate correction factors for correlating other fluid flows to some known calibration, as shown in Table 1.

Matheson has conducted extensive experiments to determine the accuracy of these mathematical formulas. At best, calculated values estimate flow rates to about ±5% accuracy. If you require greater accuracy, it will be necessary to calibrate the flowmeter with the actual gas, or at the particular conditions (temperature/pressure), in question.

Matheson has a fully equipped laboratory and has developed many special procedures for calibrating flowmeters to different gases and/or conditions.

Over the years, we have built an extensive library of flow correlation tables and curves for dozens of gases at numerous conditions. Utilizing these flow correlation tables with a Matheson flowmeter will yield the accuracy specification listed for each flowmeter model in this catalog. (Ex. ±5% for FM-1050 or FM-1000). Request the tables when you order your flowmeter.

For accuracies better than ±5%, Matheson can directly calibrate your flowmeter(s) at a cost below what most laboratories would incur to do it themselves. To request a price quotation for your specific flowmeter application, please specify the gas, operating pressure and temperature, and flow rate or flowmeter model number to your nearest Matheson office, or call our Technical Service Line at 1-800-544-1658.

Overview of Flowmeter Models

Matheson offers a complete line of variable area flowmeters to meet your application requirements.

Model Series
Scale Length Scale Type¹
Comments

The TUBE CUBE

FM-1050 150mm Reference High accuracy; glass tube

FM-1000 65mm Direct High accuracy; glass tube

FM-1100 70mm Direct High capacity; glass tube

FM-1127 127mm Direct High capacity; glass tube

TF-1000 65mm Reference Teflon®; glass tube

TF-1050 150mm Reference Teflon®; glass tube

PG-1000 50mm Direct Acrylic body with glass tube

PM-1000 37mm Direct Acrylic block and tube

VM-1000 45mm Direct Economical Plastic

Shielded 100mm Reference Software flow correlation

Flow Kits 150mm Reference Flowmeter assortment

Replacement Parts 150mm Reference 2, 3, and 4-tube mixers Replacement parts

Mixers (7300 & 7400) 150mm Reference Flowmeter multitube mixer

Note 1:Direct Reading scales are available in both English and metric units.

Reference scales come with a flow correlation table for air at standard conditions. Request a correlation table for the gas(es) or liquid(s) you will be measuring.

General Ordering Information

The Model Number Generator Tables provided in each product section enable you to build your own custom flowmeter by allowing you to specify the exact model number you wish to purchase. While the Model Number provides all the necessary information in coded form, to ensure that you receive the correct model for your application, it is recommended that you specify on your order:

Model Number, per Model Number Generator Table
Gas to be measured
Specific gravity of gas if other than air (see Gas Section of catalog)
Operating, maximum and minimum flow rates
Operating and maximum temperatures and pressures
Scale type: Direct reading or mm reference If direct reading, English or metric units If mm reference, flow correlation table(s) needed
Number of metering tubes
End blocks and seal materials
Valve type, if any: Utility, high accuracy or none
Connection type, size, orientation
Accessories: bezel, baseplate, higher accuracy calibrations, clean for oxygen service, etc.
Shipping and billing information

Mass Flow Product Overview
Models Available

Introduction
8280-232/485 Flow Commander^tm	Matheson mass flow controllers and mass flowmeters are among the most sophisticated flow sensing and control systems available. These units feature 316 stainless steel flow sensing transducers and control valves. Mass flow measuring devices generate a signal which is proportional to the mass flow of gas by detecting heat transported in an area of the gas stream. Since the specific heat of any gas is a unique property of the gas and is essentially independent of pressure considerations, mass flow devices are absolute measuring instruments.
If the signal voltage is used only to indicate flow, the unit is considered a mass flowmeter. If the signal is used in conjunction with a reference signal and a controlling valve, the unit is considered a mass flow controller.
8170 Mass Flowmeter System	Matheson's 8170 Mass Flowmeter System consists of a flow transducer which senses the flow of gas and a digital readout box which converts the analog signal to a direct reading digital display. Accuracy is 1% full scale or one digit accuracy in flow control. Matheson's 8270 Mass Controller System consists of a flow transducer which senses the flow of the gas, an electronically linked control valve, and a digital readout and control box which converts the analog signal to a direct reading digital display. Accuracy is 1% full scale or one digit accuracy in flow control.
Since these systems sense or control mass flow of a gas, the indicated flow is independent of system pressure or minor temperature variations. The systems are also 100% calibrated to specific customer requirements.
Matheson offers many innovative mass flow configurations. The Model 8280 Series Dynamic Gas Blending Systems are used to prepare accurate mixtures of different gases. The Model 8350 Series Gas Standards Generators are also available for generating precise calibration standards. The Matheson Flow Commander^tm Series features RS-232/485 Control Boxes which are used in conjunction with mass flow controller transducers to control a variety of functions through a host PC. Matheson's Cal-MAT 4000 and 4040 Series provide gas blending or dilution capabilities, controlled via a user's PC.

Mass Flow Product Overview
Function	Features	Specifications	Applications
8170 Series Mass Flowmeter System
Flow Measurement	Includes: Flowmeter transducer (Model 8172/8173 Series) Digital readout power supply box Cables and connectors Swagelok fittings on inlet and outlet High/low alarm setpoints (user selectable) Rack or bench mountable	Accuracy: 2% full scale for units up to 200 slpm 2% for units 200 slpm and over Repeatability: 0.2% for units up to 200 slpm 0.5% for units 200 slpm and over	Applications requiring monitoring of a single gas flow. May also be used with Model 8124 Totalizer (see below).
8270 Series Mass Flow Controller System
Flow Measurement and Flow Control	Includes: Flow controller transducer (Model 8272/8273 Series) Digital readout power supply box Feedback circuit for flow control Integral control valve Cables and connectors High/low alarm setpoints (user selectable) Rack or bench mountable	Accuracy: 2% full scale for units up to 200 slpm 2% for units 200 slpm and over Repeatability: 0.2% for units up to 200 slpm 0.5% for units 200 slpm and over	Applications requiring monitoring and/or controlling a single gas flow. May also be used with Model 8124 Totalizer (see below).
8124 Series Totalizer
Compiles total amount of gas used over a period of time.	Includes: 6 digit LED readout 2 alarm setpoints Rack or bench mountable	Accuracy: 1% full scale for units up to 200 slpm 2% for units 200 slpm and over Repeatability: 0.2% for units up to 200 slpm 0.5% for units 200 slpm and over	Use with 8170 Mass Flowmeter System or 8270 Mass Flow Controller System to compile the total amount of gas used, regardless of varying flow rates over a period of time.
8112 Self-Contained Mass Flowmeter
Flow measurement; bridges the gap between standard flowmeters and higher priced mass flowmeters.	Includes: Adjustable zero Threaded mounting holes in body Self-contained direct reading of flow rate	Accuracy: 1.5% full scale Repeatability: 0.5% full scale	Use with non-corrosive gases to monitor flowrate
8175 Series Multiple Mass Flowmeter Readout Box
Flow measurement of up to four gas streams	Includes: Four position selector switch Digital display Power cord Four individual cables for transducers High/low alarm setpoints for each channel (user selectable) Rack or bench mountable Required: A Model 8172 or 8173 Series Mass Flowmeter for each channel	Resolution: 3.5 digit display Power: 110 VAC standard, 220 VAC optional Output: 0-5 VDC	Continuously monitors up to four mass flow meters (one flow meter at a time). It is not required to use all four stations at the same time; they may be reserved for future expansion.
8274 Series Multiple Mass Flow Controller Box
Flow measurement and flow control of up to four gas streams	Includes: 8 position selector switch (4 read and four set) Digital display Individual override control valve switches Flow potentiometers for setting flow rate Power cord Four individual cables for transducers High/low alarm setpoints for each channel (user selectable) Rack or bench mountable Required: A Model 8272 or 8273 Series Mass Flow Controller for each channel	Resolution: 3.5 digit display Power: 110 VAC standard, 220 VAC optional Output: 0-5 VDC	Continuously monitors and controls up to four mass flow controllers (one controller at a time). Each channel requires the use of a Model 8272 or 8273 Series Mass Flow Controller. It is not required to use all four stations; they may be reserved for expansion.
8280 Series Flow Commander
Flow monitoring and control via the user's PC	Includes: Integral RS-232 (Model 8280-232) or RS-485 (Model 8280-485) interface Utility software package Required: Model 8272 or 8273 Series Mass Flow Controller Transducer 9-pin serial cable or 25-pin serial cable to connect to the user's PC	Accuracy: 2% full scale for units up to 200 slpm 2% for units 200 slpm and over Repeatability: 0.2% for units up to 200 slpm 0.5% for units 200 slpm and over	Applications requiring remote operation/control of a single gas stream
8280 Series Modular Dyna-Blender
Gas blending	Includes: Mass flow controller transducer 8280 control box Power cord Cable for transducer Rack or bench mountable Required: Existing mass flowmeter, flow controller to feed the other gas stream to be blended	Accuracy: 2% full scale for units up to 200 slpm 2% for units 200 slpm and over Repeatability: 0.2% for units up to 200 slpm 0.5% for units 200 slpm and over	Low cost blending of two gas streams for laboratory and process applications. Several units may be used together to blend additional streams.
8284 Series Multichannel Dyna-Blender
Gas blending	Includes: Four channels with individual potentiometers and control switches Four position switch reading in % of range Power cord Cables for transducers Rack or bench mountable Required: Model 8272 or 8273 Mass Flow Controller transducer for each channel	Accuracy: 1% full scale for units up to 200 slpm 2% for units 200 slpm and over Repeatability: 0.2% for units up to 200 slpm 0.5% for units 200 slpm and over	Low cost blending of up to four gas streams for laboratory and process applications.
8350 Series Gas Standards Generator
Gas blending; gas dilution (Model 8356 two channel multiple mixing )	Includes: Self-contained blending system and integral mass flow controllers Packless shut-off valves Stainless steel check valves to prevent contamination of individual lines Eight position switch (four positions for reading % of range and four positions for setting controller flow rates) Available in 2 channel, 4 channel, or 2 channel with multiple mixing (re-mixes the blended gas with pure component to provide a lower concentration of blended gas) Rack or bench mountable	Accuracy: 2% full scale Repeatability: 0.2% Flow ranges: 0-20 sccm to 0-20 slpm	Blending of up to four gases to create precise calibration standards, used for calibration of gas chromatographs and other analytical instruments.
Cal-MAT Series 4000 Multi-Component Gas Blending System
Gas blending via integral mass flow controllers and the user's PC	Includes: One balance gas mass flow controller and one component gas mass flow controller standard (up to 4 mass flow controllers available as an option) RS-232 interface Three modes of operation: concentration mode (user enters target gas concentrations for each cylinder and desired output flow for the mix); flow mode (user specifies the flow rate out of each cylinder); or program mode (the instrument may be programmed for unattended operation) Required: User's PC	Accuracy: 1.0% full scale Repeatability: 1.0% full scale Flow: 1.0% full scale	Blends up to four gas streams (3 component gases, 1 balance gas) to create calibration standards for calibration of analytical instruments or process instruments. The standard unit blends 2 gases; 4 gases available as an option. See TB-357 for more details.
Cal-MAT Series 4040 Gas Dilution System
Gas dilution	Includes: One dilution gas mass flow controller and one component gas mass flow controller standard (up to four mass flow controllers available as an option) RS-232 interface Four modes of operation: concentration mode (user enters target gas concentrations for each cylinder and desired output flow for the mix); divider mode (user operates the unit as an automated 10-step gas divider); flow mode (user specifies the flow rate out of each cylinder); or program mode (the instrument may be programmed for unattended operation) Required: User supplied PC	Accuracy: 1.0% full scale Repeatability: 1.0% full scale Flow: 1.0% full scale	Dilutes a high concentration gas with a balance gas to create calibration standards for multi-point calibration of analytical instruments. See TB-358 for more details.

For further information, please contact MEGS at the number above.

Mass Flow Product Overview Models Available

Mass Flow Product Overview
Models Available