CSB Animation and Analysis of Torrance Refinery Explosion

The United States Chemical Safety Board investigates industrial accidents related to chemical processing. It is an advisory agency that provides recommendations for improving safety in chemical related operations.

Some accident events are illustrated with animated reenactment, along with the events determined to be contributory to the cause. In the case of the Torrance, CA refinery explosion, the animation shows how a worn valve that did not provide adequate shutoff was part of the string of events that ultimately led to disaster. Also of concern was the procedure followed in responding to the discovery of an unexpected condition indicating substantial process malfunction.

Fortunately, the flammable gases were detected by personal safety gear, enabling workers to clear the area before ignition occurred.

The video describes how the process operated and what failed. The key takeaway is that a single failure condition can reveal another that may have gone undetected. Also, operating under adverse conditions, trying to formulate strategy, is difficult and may not produce the most effective plan.

Industrial processing can be complicated and dangerous. Diligence in design, installation, and continuing maintenance of process equipment is part of the overall safety plan for every facility.

Consider your own process and where weaknesses may be lurking. Reach out to equipment and instrumentation vendors for advice and expertise regarding specific items of concern.

New Thermal Mass Flow Meter

The new model FT4A thermal mass flowmeter, shown
inserted in process pipe.
Courtesy Fox Thermal Instruments

Fox Thermal Instruments, manufacturer of thermal technology based mass flow instruments for industrial process measurement, has introduced a new more advanced product providing the accuracy and reliability users expect from Fox, along with some new features extending the ease of use and applicability of the instrument.

The basic operation involves measuring flow in relation to its heat dissipating effect on a temperature sensor. Higher mass flow produces a higher rate of heat transfer.

The mass flow measurement instruments are very popular for several reasons. They have no moving parts, have a fairly unobstructed flow path, are accurate over a wide range of flow rates, calculate mass flow rather than volume, measure flow in large or small piping systems, and do not need temperature or pressure compensation. While most thermal flow meters are used to measure flowing gas, some also measure flowing liquids.

The new model FT4A incorporates the latest feature updates and technology advancements. More information can be found in the datasheet provided below. Share your gas flow measurement challenges with instrumentation specialists. Combine your own process experience and knowledge with their product application expertise to develop effective solutions.

New Thermal Mass Flow Meter From Fox Instruments from Classic Controls, Inc.

In-Line Process Refractometer

Refractometry, a combination of physics, materials, and chemistry, is a measurement technique which determines the composition of known substances by means of calculating their respective refractive indexes (RI). RIs are evaluated via a refractometer, a device which measures the curve, or refraction, resulting when the wavelength of light moves from the air into and through a tested substance. The unitless number given by the refractometer, usually between 1.3000 and 1.7000, is the refractive index. The composition of the substance is then determined with a comparison of the measured RI to standard curves developed for the substance. There are four general types of refractometers: digital, analog, lab, and inline process. Although refractometry can measure a variety of substances, the most common group of known substances to calculate is liquids. Liquid based continuous processes benefit from the use of an inline process refractometer to provide real time data about process output or intermediate steps.

The ultimate focus of industrial refractometry is to describe what is in a final product or output of a process step. A field which relies directly on the results of refractometry is gemology. Gemological refractometry is crucial for accurately identifying the gemstones being classified, whether the gemstones are opaque, transparent, or translucent.

Other common examples of industrial refractometry uses include measuring the salinity of water to determine drinkability; figuring beverage ratios of sugar content versus other sweeteners or water; setting eye-glass prescriptions; understanding the hydrocarbon content of motor fuels; totaling plasma protein in blood samples; and quantifying the concentration of maple syrup. Regarding fuels, refractometry scrutinizes the possible output of energy and conductivity, and for drug-testing purposes, refractometry measures the specific gravity, or the density, of human urine. Regarding food, refractometry has the ability to measure the glucose in fruit during the fermentation process. Because of this, those in food processing can know when fruit is at peak ripeness and, in turn, also understand the most advantageous point in the fruit’s lifetime to put it on the market.

The determination of the substance composition of the product examples listed above all speak to the purpose of quality control and the upholding of standardized guidelines. Consumers rely on manufacturers not only to produce these products safely and in vast quantity, but to deliver the customer a consistent taste experience when the product is consumed. Brand marketing success relies on maintaining the standards for the composition of substances that comprise the product. One could argue that an in-line process refractometer is actually a marketing tool of some sort, at least to the extent that it is employed to maintain consistent product quality.

Equipment manufacturers have developed numerous refractometer configurations tailored to specific use and application. Each has a set of features making it the advantageous choice for its intended application. Product specialists can be invaluable sources of information and assistance to potential refractometer users seeking to match the best equipment to their application or process.

Continuous Liquid Level Measurement Technologies Used in Industry

Magnetic level indicator coupled with
guide wave radar level transmitter
Courtesy Vega

Although continuous level measurement technologies have the ability to quantify applications for bulk solids, slurries, and granular materials, liquid level technologies stand out as being exceptionally crucial to the foundation of process control. Called “transmitters,” these continuous liquid level measurement devices employ technologies ranging from hydrostatics to magnetostriction, providing uninterrupted signals that indicate the level of liquid in a vessel, tank, or other container.

Hydrostatic devices focus on the equilibrium of dynamic and static liquids. There are three main types of hydrostatic transmitters: 1) displacer, 2) bubbler, and 3) differential pressure.

The displacer transmitters utilize a float placed within the liquid container. With its buoyancy characterized to the liquid and the application, the float, a connecting stem, and a range spring or similar counterbalance represents the liquid level in terms of the movement of the displacer (float). The displacement, or movement, of the assembly is converted into an electric signal for use by the monitoring and control system.

Bubbler transmitters are used for processing vessels that operate at atmospheric pressure. This method introduces a purge gas or an inert gas, e.g. air or dry nitrogen, into a tube extending into the liquid vessel. Precise measurement of the pressure exerted on the gas in the dip tube by the liquid in the tank is used to determine the height of the liquid.

Differential pressure (DP) transmitters rely directly on, in a basic explanation, the pressure difference between the bottom and top of the container. Precise pressure measurement is used to determine the height of the liquid in the tank. One of the most advantageous aspects of DP transmitters is that they can be used in pressurized containers, whereas displacer and bubbler transmitters cannot.

Other examples of level transmitter technologies––which are not hydrostatic devices––are magnetostrictive, capacitance, ultrasonic, laser, and radar.

In magnetostrictive level transmitters the measuring device, a float, has a series of magnets that create a magnetic field around a wire enclosed in a tube. Electrical pulses sent down the wire by the transmitter head product a torsional wave related to the position of the float, which moves with changes in liquid surface level. The transit time of the torsion wave back to the sensing head is measured and the depth of the liquid, as indicated by the float position, can be determined.

Capacitance transmitters are best applied to liquids that have high dielectric constants. Essentially, changes in the capacitance of the sensor / tank / liquid assembly will vary proportionately with the liquid level. The change in capacitance is measured and converted to an appropriate electrical signal.

Ultrasonic level transmitters emit ultrasonic energy from the top of the vessel toward the liquid. The emissions are reflected by the liquid surface and them time required for the signal to return to the source is used to determine the distance to the liquid surface.

Laser level transmitters operate similarly to an ultrasonic level transmitter. However, instead of using ultrasound signals, they use pulses of light.

Radar level transmitters involve microwaves emitting downward from the top of the container to the liquid’s surface and back again; the measurement is the entire time-frame. One variable radar level measurement echoes capacitance measurements: they both involve dielectric contact of liquid.

The precise measurement of transmit time for a wave or pulse of energy is employed in several of the technologies, the measurement of pressure in others. Each technology has a set of attributes making it an advantageous selection for a particular range of applications. Share your liquid level measurement challenges with an application expert, combining you process knowledge with their product application expertise to develop effective solutions.