CFO-ONE Automatic Critical Flow Orifice

Automatic Critical Flow Orifice

To comply with EPA CFR 1065.341 and E/ECE/TRANS/505 3.5. regulations, CVS sampling system accuracy must be regularly verified using one of the suggested methods. One such method is to inject a metered amount of propane into the system and verify the amount downstream of the CVS system.

The CFO-ONE injects a known amount of propane into the exhaust plenum system, comparing the calculated concentration with that is indicated by the CVS. Propane is passed through a critical flow orifice to give a specific propane flow rate, which is injected into the CVS. When the CVS flow rate is known, the expected propane concentration can be calculated from this flow rate.

Segment: Automotive

Division: Emission Measurement Systems

Manufacturing Company: HORIBA UK Limited

Internal automatic pressure regulator allows the operator to set the desired flow rate of the CFO-ONE to any value between 0.0022 to 0.0282 SCFM to an accuracy of ±0.4% FS.
AK control interface for automated testing capability & removal of potential human error associated with manual operation.
STARS VETS integrated driver for completely automated operation.
Lightweight design with included carry case for ease of transportation and storage.
Class leading accuracy and compact size.
Calibrated in an ISO 17025 compliant laboratory.

Frequently Asked Questions

Why is my calculation giving me the wrong figure?
You will need to use the CFO-ONE’s temperature reading in your calculation.

Why is the CFO-ONE’s temperature more than my test cell ambient?
The CFO-ONE temperature probe is located next to components which provide a certain amount of self-heating; however this will not affect your reading.

What pressure reading should I use?
The correct pressure to input into your CVS check calculation is either Orifice Pressure Low or Orifice Pressure High (depending on which orifice you have used)
Note: The APR feedback pressure is for reference only.

How do I know if the system is actively pushing propane through it?
The Low or High Orifice reading on the CFO will show a value higher than ambient pressure (example, at sea level 14.7psi is shown before the CFO is active, when active the value could be 60psi).

How do I select Auto Mode?
Use the AK commands or in the CFO Host software select the system button on the bottom left and choose Run Mode.

How do I select Manual Mode?
Use the AK commands or in the CFO host software select the system button on the bottom left and choose Manual Mode.

The pressure reading is different to the older CFO-202 systems.
The CFO-ONE has an absolute pressure sensor, therefore it will correct for ambient altitude conditions, so entering 60psi will inject at a pressure of 45.3psi + 14.7psi (example based on seal level pressure).

The CFO has a negative error vs my CVS reading.
Check the CFO outlet pipe is put deep into the CVS Inlet pipework / connected securely to the CVS quick connect this will prevent leaks that will mean the propane leaving the CFO does not enter the CVS system resulting in a negative result.

My CFO appears to be out of calibration.
Check the setup of your CFO, ensuring it conforms with the requirements listed in the user manual.

1. System Specification

Model	CFO-ONE
Application	Accuracy checker for CVS system
Dimensions mm (DxWxH)	298x340x150
Weight kg	10
Test media	Propane
System configuration	CFO Unit Stainless Steel Braided Hoses Carry Case
Measuring items	Gas temperature Gas pressure (Abs) Automatic Pressure Regulator
Control / Output Options	AK Host Protocol (LAN) STARS VETS (LAN)
Power supply	100V AC to 240V AC 50/60 Hz Build in AC to DC converter
Installation	Portable
Number of Orifices	2 (choice of 5 orifice sizes)
Orifice Range	See Section 3
CVS Flow Range	Calibrated for any single flow rate between 1.7 – 30 m3/min
Injection Gas Concentration	Calibrated for any single concentration between 1 – 800ppm
Injection Gas Pressure	Calibrated for gas supply pressure between 30 – 80psig (45-95psiA)
Orifice Pressure Indicator	0 – 100psiA
Orifice Temperature Indicator	0 – 100ºC
Output Connection	Swagelok quick connect ©2022 HORIBA UK Ltd 5
Connection Tubing	Stainless steel braided hoses
Environment for use	Temperature: 0ºC to 40ºC Humidity: Under 80% as relative humidity Altitude: 0 m to 1500 m above sea level
Approved standards	CE, RoHS compliant
Accuracy (Volume) _{ISO 17025 Calibrated & verified against Brooks Vol-U-Meter bore cylinder & piston}	0.0022 to 0.0282 SCFM ±0.4% FS

2. Accessory sensors

Gas temperature sensor	Thermocouple type:	PT100
	Measurement range:	0 – 100ºC
	Accuracy:	0.1% of reading
	Response time:	40 ms
Gas pressure sensor	Measurement range:	0 to 100psiA
	Accuracy:	±0.1 % of full scale
	Operating Temp. Range:	- 10 to +50ºC
Automatic Pressure Regulator	Operating range:	0 to 950 kPa
	Accuracy:	±1.0% of full scale
	Operating Temp. Range:	+5 to +50ºC

3. Orifices

Number of Orifices	Choice of 5 orifices depending on desired range
Orifice Sizes (diameter)	0.002”
	0.0025”
	0.004”
	0.005”
	0.0055”
Propane Flow Rate	Propane flow rate is dependent on orifice size and gas inlet pressure. See Section 2.3.1
Propane Concentration Range	Propane concentration is dependent on propane flow rate and CVS Flow.
	See Section 4

4. Propane Flow Rate

The following is an indication of the orifice flow rates for each size orifice at high and low CFO gas pressure.
(Based on ambient conditions of 14.7psiA and 20ºC)

Orifice Diameter	Propane Flow Rate at Given CFO Pressure
	SCFM		SLPM
	CFO Pressure (psiA)		CFO Pressure (psiA)
	40	80	40	80
0.002”	0.0022	0.0038	0.06	0.11
0.0025”	0.0034	0.0059	0.10	0.17
0.004"	0.0087	0.0150	0.25	0.42
0.005"	0.0135	0.0234	0.38	0.66
0.0055"	0.0163	0.0282	0.46	0.80

Size: 0.86 MB

CFO-ONE User Manual

CFO-ONE