How we use your application info to build a custom device
Alicat mass flow and pressure controllers and meters are custom built to meet specific application needs. Some of the most common considerations when building a custom Alicat solution include:
- Flow rate
- Fluid type
- Inlet and outlet pressures
- Process temperature
- Analog/digital communication
- Process threads and fittings
This article provides an explanation of each of these considerations.
It is important to indicate what parameters you need to measure and/or control in your process, so we can determine the right device(s) for your setup. Alicat makes a variety of instruments for:
- Measuring flow
- Controlling flow
- Measuring pressure
- Controlling pressure
Most Alicat mass flow instruments are differential-pressure based. These multivariate mass flow meters and controllers simultaneously measure mass flow, volumetric flow, pressure, and temperature. Controllers are additionally able to control on mass flow or volumetric flow while measuring pressure, or they can be set to control pressure while measuring flow. Alicat also offers Coriolis mass flow meters and controllers, for true mass flow measurement and control.
Pressure transducers or controllers are available for measuring and/or controlling absolute, gauge, or differential pressure.
Each device is custom ranged to a specific full scale flow rate, making it important to indicate which flow rates you will be flowing in your process.
- Differential pressure instruments can flow up to 5000 SLPM, with most devices having operating ranges of 0.01% to 100% of their full scale flow rate. Imagine the maximum flow rate in your process will be 18 SLPM. A device can then be ranged to flow 18 SLPM at full scale, and will provide in-spec readings down to 0.0018 SLPM (1.8 SCCM). If you know that your maximum flow rate will instead be 37 SLPM, a device can be ranged to flow from 0.0037 SLPM (3.7 SCCM) to 37 SLPM.
- Coriolis instruments can flow up to 100 kg/hr. Meters operate from 0.2% to 100% of full scale and controllers operate from 2% to 100% of full scale.
It is important to note that accuracy varies across the flow range, and in the case of Coriolis depends on whether you are flowing gas or liquid. Imagine, for example, that you order a standard differential pressure meter with an 18 SLPM full scale flow rate. Its accuracy spec is ±0.6% of reading and ±0.1% of full scale. The meter will be able to measure flow rates within device specifications from 18 SLPM down to 0.0018 SLPM (1.8 SCCM), however accuracy will decrease at lower flow rates. Whether or not you will need one or multiple devices is highly dependent on the flow range and accuracy requirements of your application.
Devices can be built using a variety of wetted materials, to ensure fluid compatibility. Two important questions are:
- Are you flowing gas or liquid?
- Is the fluid corrosive or non-corrosive?
Non-corrosive gases: If you are flowing non-corrosive gases, you can use most Coriolis or differential pressure instruments. Differential pressure mass flow meters/controllers are equipped with Gas Select™, a library of 98+ pure and mixed gas calibrations. This enables easy switching between process gases, without the need for recalibration. Custom gas mixtures can also be added to the library using COMPOSER™.
Corrosive gases: Many differential pressure devices can be configured to flow corrosive gases. In this configuration, the flow body, sensors, and elastomers are upgraded to materials that are compatible with 128+ gases, including 30+ aggressive gases. Coriolis devices can also be used to flow corrosive gases.
Liquids: When flowing liquids, use a liquid flow device or Coriolis mass flow instrument.
Inlet and outlet pressure
All devices have both minimum and maximum operating pressures. As a fluid flows through a device, some pressure will be lost. Process pressure must exceed the pressure drop of the device, but cannot be too high or the device can be damaged.
- Maximum pressure is the maximum pressure that a device can handle without risk of damage.
- Pressure drop is the difference between the flow rate at the inlet and outlet of the device. For example, if your inlet is 130 PSI and your outlet is 100 PSI, the pressure drop would be 30 PSI. Alicat devices have both minimum and maximum pressure drops. The minimum must be exceeded in order for the device to reach its full scale flow rate. If the pressure drop is too high, the internal sensors can be damaged.
Your process temperatures must also be compatible with your device.
- Most differential pressure meters/controllers can flow fluids ranging from −10°C to +60°C
- Most Coriolis meters/controllers can flow fluids ranging from −35°C to +70°C
Available communication protocols for most Alicat differential pressure devices include:
- Analog (4-20 mA, 0-10 Vdc, 0-5 Vdc, or 1-5 Vdc)
- ASCII over RS-232 or RS-485
- Modbus RTU
For Coriolis devices, the following communication protocols are available:
- Modbus RTU
Process threads and fittings
Threads and fittings are the inlets and outlets of our flow instruments. As with many threading and connecting designs, needs vary by mechanics and standards. Higher flow, higher pressure applications need more robust threads to withstand the forces involved, and the converse is true too.
For Alicat devices, the default thread is NPT (National Pipe Thread). We also offer a variety of other threads and fittings, including SAE, AN 37 degree flare, VCR, VCO, Swagelok compatible compression, and BSPP (or “G”).