PSI-2

Why Measure Flow?

The measurement of flow in a process increases the efficiency and safety of that process. Ultimately this has an affect on expenditure, as process efficiency and safety improve likewise plant running costs reduce.

Why Choose Differential Pressure Technique of Flow Measurement?

There are many flow measurement technologies available. Differential Pressure (DP), the most popular flow measurement technique, is the easiest and most comprehensive one.

DP techniques are easy to install, troubleshoot and calibrate. Alternate techniques are either very expensive or require specific dry, dust free environments .

DP is measured with a combination of a primary element which has to be in the duct to create a difference pressure and is connected to a secondary element, a transmitter, which records calculates and transmits the data to the control system.

Primary DP Elements

Venturi – Designed at the build stage of the plant, these ducts are big and can be difficult to set up.

Orifice Plate – A circular disc with holes inserted into the process duct can cause flow restriction which questions measurement reliability. Both venturi and orifice introduces restriction and hence pressure drop, which will at all time, add extra cost to operation of the fan.

Pitot Tubes – Inserted into the process duct at the desired place and time, DP is the difference in pressure measured at the front and back of the probe. Pitots have a wide operating process temperature range and have proven to be a very reliable method. Pitot tubes are the standard Primary element for accredited verification of flow profile

The Most Flexible DP Solution

The new PSI-2 FPU is a compact ALL in ONE flow monitor, fully assembled with fitted primary element. It provides three separate measurements in one simple, easy to use flexible solution in industrial applications. The static primary element component being either an S type or averaging pitot depending on application.

This fully assembled complete unit comprising of transmitter and integrated pitot tube reduces installation difficulties and costs whilst improving of accuracy. The pitot tube introduces a minimum of pressure drop in the duct – which can be ignored.

With installation via one simple insertion, it is able to acquire information from the process without disruption. Allowing correlation of flow data, which is calculated several times a second, with process changes enhancing process control.

Improved air/fuel ratios in combustion processors gives enhanced energy efficiency, reduced pollutant emissions and extended plant life.

Key Features

• Variables: Integrated Differential Pressure, Absolute Pressure, Process Temperature, Instrument Temperature
• Integrated S type or averaging pitot probe in a range of standard or custom length and mountings
• Operated as a fixed or portable device. Portable mode powered via the USB connection to a Laptop
• Inbuilt intelligent auto zero for very low speed applications
• Dynamic range 0 – 60m/sec at STP
• Tolerant to contamination such as dust and water droplets
• Programmable response time from 0.1 seconds to minutes
• Reports parameters in several units for example metre/second, feet/minute
• Reports process velocity, volumetric flow, mass flow, normalised volumetric flow, and mass flow and volumetric flow on a wet or dry basis
• Polynomial linearisation for changes in flow profile with process load
• Licence free Modbus communications over RS485 for long distances
• 4 – 20 mA analogue output, programmable for range and units
• Enhanced protection against electrical discharges such as near by lightening strikes
• Secondary USB service port for in-situ calibration and maintenance without disruption of normal communications
• IP69K rated allowing use in extremely wet and dusty external environments
• Extensive self diagnostics

Key Applications

• Flue gas flows
• Combustion air flow distribution
• Power generation
• Incineration plants
• Industrial ventilation systems
• Air flow distribution control
• Wet and mildly corrosive gas flows
• High temperature applications
• Food processing
• Air flows in air with high dust content

Specification

Instrument
Static pressure input	0 to 207KPa absolute
Operating differential pressure	+/-1000Pa	Approx 32m/s at STP [1]
Max. differential pressure	25KPa (250mbar)	No damage
Max. differential pressure	50KPa	Burst limit
Max. common mode pressure	207KPa Gauge all inputs	Burst limit of differential pressure transducer
Repeatability (transducers)	0.1% FS	[2]
Span drift differential & static pressure	+/-0.25% FS	[2]
Zero drift differential & static pressure	+/-0.2% FS	[2,3]
Ambient temperature range	-20°C to 70°C
Supply	8V to 30V 150mA maximum
Process temperature range	-20°C to 700°C	Higher temperature ranges available on request
Pitot
S-type style pitot tube	300mm to 2m
Averaging style pitot tube	300mm to 2m
Material available	316 stainless steel
Temperature range	-40°C to +700°C	Higher temperature ranges available on request
Back purge	Available for high dust applications

Miscellaneous
Outputs	Configurable analogue output assignable to any measured or calculated parameter
	Outputs are 4 – 20mA isolated
Serial interface	RS485 MODBUS RTU selectable baud, parity, and stop bit
	HART All internal parameters are available via the RS485 and the USB communication
	USB
Connections	IP69K 6-pole field connectors
	IP69K USB mini-B service connector
IP rating	IP69K

[1]	Specification based on standard differential transducer. Higher ranges are available but the burst common mode pressure remains at 207KPa gauge.
[2]	As the velocity calculation is based on the square root of differential pressure, velocity errors are non liner. For low velocity accuracy the actual error must be calculated based on the transducer performance applied to the velocity calculation formula.
[3]	The zero drift on the differential pressure is quoted with auto zero switched off. Improved zero performance can be obtained if the auto zero is enabled and configured for the application.