Inline process refractometers are a type of refractometer designed for the continuous measurement of a

fluid In physics, a fluid is a liquid, gas, or other material that continuously deforms (''flows'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot resist any shear ...

flowing through a pipe or inside a tank. First patented by Carl A. Vossberg Jr.br>US2807976A
- Refractometer US2549402A, these refractometers typically consist of a

sensor A sensor is a device that produces an output signal for the purpose of sensing a physical phenomenon. In the broadest definition, a sensor is a device, module, machine, or subsystem that detects events or changes in its environment and sends ...

, placed inline with the fluid flow, coupled to a control box. The control box usually provides a

digital Digital usually refers to something using discrete digits, often binary digits. Technology and computing Hardware *Digital electronics, electronic circuits which operate using digital signals ** Digital camera, which captures and stores digital ...

readout as well as 4-20 mA analog outputs and relay outputs for controlling

pumps A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by mechanical action, typically converted from electrical energy into hydraulic energy. Pumps can be classified into three major groups according to the method they ...

and valves. Instead of placing the sensor inline of the process, it can be placed in a bypass, attached by a thin tube. This

measurement Measurement is the quantification of attributes of an object or event, which can be used to compare with other objects or events. In other words, measurement is a process of determining how large or small a physical quantity is as compared ...

has been an important element in the

process control An industrial process control in continuous production processes is a discipline that uses industrial control systems to achieve a production level of consistency, economy and safety which could not be achieved purely by human manual control. ...

of the chemical and refining, pulp and paper, food, sugar and pharmaceutical industries for more than a century. For instance, the in-line concentration measurement can be used as a real-time predictive tool for the final

concentration In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', '' molar concentration'', ''number concentration'', ...

. A quick and accurate response is needed to optimize production. Cost reduction is possible by reducing the variation of mean average of the product concentration. The cost saving is related to the value of the component being measured. A digital inline process refractometer sensor measures the

refractive index In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium. The refractive index determines how much the path of light is bent, ...

and the

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

of the

processing medium In industrial engineering, a processing medium is a gaseous, vaporous, fluid or shapeless solid material that plays an active role in manufacturing processes - comparable to that of a tool. Examples A processing medium for washing is a soap soluti ...

. The measurement is based on the refraction of light in the process medium, i.e. the critical angle of refraction using a light source. The measured refractive index and temperature of the process medium are sent to the control box. It calculates the concentration of the process liquid based on the

and temperature, taking pre-defined process conditions into account. The output is typically a 4 to 20mA DC output or, increasingly, an

Ethernet Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 1 ...

signal proportional to process solution concentration, liquid density, Brix or other scale that has been selected for the instrument. The inline process refractometer consists of three primary components: the inline sensing head, the electronics console, and the process adapter. The inline sensing head is mounted on the adapter and contains a prism that scans the process solution through a transparent window and outputs a value relative to the refractive index of the solution. The electronics console houses all control circuitry, microprocessors, digital displays and calibration points and conditions the sensing head signal. The process adapter is the mechanical connection between the inline sensing head and the process piping, and is designed specifically to accommodate the pipe size and application. Inline process refractometers are used primarily in the pulp and paper industry; the food and beverage industry, the pharmaceutical industry, and the chemical industry as a means to assure consistency and quality. In the

pulp and paper industry The pulp and paper industry comprises companies that use wood as raw material and produce Pulp (paper), pulp, paper, paperboard and other cellulose-based products. Manufacturing process The pulp is fed to a paper machine where it is formed as ...

, inline process refractometers are used in the energy recovery from

black liquor In industrial chemistry, black liquor is the by-product from the kraft process when digesting pulpwood into paper pulp removing lignin, hemicelluloses and other extractives from the wood to free the cellulose fibers. The equivalent material i ...

recovery boilers by accurately measuring solids in the black liquor. In the food and beverage industry, inline process refractometers are used to measure dissolved solids, most often as sugar content, measured in

degrees Brix Degrees Brix (symbol °Bx) is a measure of the dissolved solids in a liquid, and is commonly used to measure dissolved sugar content of an aqueous solution. One degree Brix is 1 gram of sucrose in 100 grams of solution and represents the strengt ...

. In the pharmaceutical industry they are used to monitor and control concentration levels during supersaturation, a critical process in crystallization. In the chemical industry they are used in

Hydrochloric Acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid. It is a component of the gastric acid in the dige ...

applications,

Sulphuric Acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular for ...

applications, and boiler cleaning chemicals processes.

References

{{DEFAULTSORT:Inline Process Refractometer Refractometers