Gas mass flow controllers and meters are specialized instruments for regulating or measuring gas flow. Providing the following information before purchase helps the manufacturer recommend a product that matches the application.
1. Brand and supplier
Imported and domestic products vary in features, quality, support, lead time and price. Compare these factors together and choose the product that offers appropriate performance and value for the process.
2. Flow range
The required operating range must match the instrument's usable measurement or control range. For example, an instrument rated at 10 SLPM is not an appropriate single-range solution for both 8 SLPM and 10 SCCM: those two operating points are too far apart for satisfactory control on that range.
Similarly, a user may currently need 3 SLPM of air but expect to test at 80 SLPM in the future. Selecting a 100 SLPM instrument may cover the future maximum, but it is a poor choice for accuracy at the current 3 SLPM operating point. Evaluate actual minimum, normal and maximum flows instead of simply buying the largest range.
3. Pressure
Operate within the pressure conditions confirmed when ordering. Reliable performance is not assured outside that envelope.
Specify the inlet pressure range and outlet pressure range separately, including any downstream backpressure. These conditions affect valve configuration and calibration. Stable pressure improves control; add appropriate pressure regulation when the source is unstable.
The maximum pressure the instrument can safely withstand is different from the pressure range in which it can regulate flow correctly. A pressure rating must not be treated as a guarantee of control performance at that pressure.
4. Accuracy
Accuracy, linearity and repeatability are separate performance requirements. Their importance depends on the process, and tighter specifications affect cost. Evaluate the required performance rather than assuming the most expensive instrument is the best match. Confirm whether each stated accuracy is relative to full scale or reading; current Flowmethod accuracy options are specified on a full-scale basis.
5. Mounting orientation
Standard configurations generally assume the agreed mounting orientation. If the instrument must be installed vertically, on its side or in another orientation to fit the equipment, tell the manufacturer before ordering. Confirm the effect on performance and arrange calibration in the actual mounting orientation when required.
6. Gas
Air and nitrogen, corrosive gases such as ammonia or hydrogen chloride, and gases with special safety requirements may require different wetted materials or seals. State the actual gas when ordering. It also determines calibration and gas-factor conversion.
Keep the gas dry and free of liquid water, oil and other contaminants. For multi-gas use, check the converted range for every gas, compatibility when corrosive and non-corrosive gases share an instrument, and the effects of residual gas between uses.
7. Operating interface
Choose the interface for the application: 0–5 V or 4–20 mA analog signals, RS485 / Modbus RTU digital communication, or local display and keypad operation. Controllers accept flow setpoints; meters only provide flow readings.
8. Power supply
Older instruments in the market may use a dual ±15 V supply or a single 24 V supply. Match the supply to the exact model rather than assuming they are interchangeable. The current Flowmethod flow products on this website use 9–36 VDC, commonly 24 VDC. Existing PLC equipment with a suitable 24 V supply may therefore simplify integration.
9. Gas fittings
Select the fittings before purchase. Common options include 3 mm, 6 mm and 8 mm tubing, 1/4 in. and 1/8 in. double-ferrule fittings, and 8 mm hose fittings. Confirm the size and connection form for the actual tubing. Fittings can be supplied in the agreed configuration; process tubing is not included.
Flowmethod designs, develops, manufactures and supports gas mass flow controllers, meters and custom gas-control and mixing systems. Configurations are matched to the customer's process and operating requirements.
For selection, installation or technical enquiries, contact Flowmethod: Mr. Dou, +86 180 3818 3381; doufeijin@hotmail.com. See Contact for the full contact list.