PetroSense FAQs

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PetroSense Technology

What makes the PetroSense Fiber Optic Technology unique?

The PetroSense® products incorporate FCI's patented fiber optic chemical sensor (FOCS®) technology with digital electronics and a microprocessor to make PetroSense unique in the marketplace. The chemical coating on the fiber optic sensor has a specific affinity for hydrocarbons which makes the FOCS systems both repeatable and accurate for total petroleum hydrocarbon (TPH) measurements. The PetroSense product line will supply TPH measurements without the use of hydrochloric acid, freon, or any other solvents used for extraction. The PetroSense products are available today, have proven track records in the field, and are competitively priced.

How does the PetroSense technology work?

The PetroSense technology is based on the principle of a Fiber Optic Chemical Sensor (FOCS). A light emitting diode (LED) sends light through the chemically coated strand of optical fiber depicted below. As the outside of the fiber comes in contact with hydrocarbons, some of the light travelling through the optical fiber escapes. A reference detector at one end and a sense detector (PD) at the other end of the fiber measure that loss of light. This change in the refractive index (loss of light) correlates very well to the concentration of hydrocarbons present.

PetroSense Technology Operating System

What advantage does FOCS have over UV (ultraviolet), IR (infrared) or Fluorescence?

When using UV, IR or Fluorescence, each technology has limitations. UV and IR rely on the hydrocarbon's ability to adsorb a specific wavelength of light. Problems can arise when other contaminants in produced water may also adsorb at that same wavelength increasing your value of oil in water. This change in turbidity can have a pronounced effect on the accuracy of results.

Fluorescence can have the same limitations with a bit of a twist. Because specific filters have to be
used for control of the specific wavelength before and after the sample cell, changes in production
characteristics can lead to inaccurate results.

Fluorescence also has had problems with increases in turbidity similar to the UV and IR.
Also, the UV, IR, and Florescence technologies all require an extraction with freon or hexane before
the hydrocarbon can be measured. This means handling and disposing of more chemicals for your

Finally, in-line systems using these technologies can be cost prohibitive.

What can interfere with oil-in-water readings using the PetroSense products?

You should expect very little interference using the PetroSense technology. Turbidity and typical produced water flocculants and coagulants used to clarify produced water should have no effect on the PetroSense readings.

The key to success with your new PetroSense monitoring equipment is to keep it well maintained and clean as discussed in the operation procedures.



Although these sensors are non-specific, there is a relative response characteristic for the different compounds that are detected. The PetroSense sensors have a very strong response for aromatic and other large hydrocarbon compounds. This makes these sensors very useful for the detection of BTEX (benzene, toluene, ethyl benzene and xylenes), which is used as a tracer for TPH leaks/contamination. The characteristic relative response factors (RRF's) can be determined for specific sites. The sensors can be calibrated for specific compounds expected at a given site, or the non-specific readings can be converted to the concentrations of these specific compounds by use of the appropriate RRF's.

Word From An Independent Study:

Fiber Optical Sensor (FOCSTM) System – used to directly and quickly monitor concentration of total petroleum hydrocarbons in the air, at the air/water interface, and dissolved in water. FCI's hydrocarbon sensor is designed to monitor the concentration of dissolved BTEX in water, liquid product at the air/water interface , and BTEX in vapor.

PetroSense sensors are very sensitive to BTEX and its individual components dissolved in water. The Sensors are capable of detecting low concentrations of BTEX with a high degree of accuracy. FCI’s sensors match readings taken via the gas chromatograph with at least a 98% correlation." Based on a comparison with EPA Method 8020.



The PetroSense sensors begin to respond immediately to the presence of BTEX hydrocarbons dissolved in water. They provide quantitative results in ppm of the compound used to calibrate the system. When measuring blind samples of p-xylene the probes correlate with the GC at the 99% level. The blind samples run with benzene (RRF of 6.233) showed a quantitative correlationof 97% with the GC and UV. Toluene (RRF of 2.857) gave similar results with a correlation of 98%. Ethyl benzene (RRF of 1.034) had a correlation of 98%. And when run with a 1:1:1:1 mixture of BTEX the average RRF is 1.730 and the correlation was 98%.



And Quick In the presence of product, the sensors achieve a 95% detection level in approximately 5 minutes. When the sensors are removed from contaminated water containing a product and placed in chemical-free water, the fall back time to a baseline reading occurs in approximately 2 minutes.


Ken Wilcox Associates, Inc.