Sunday, January 31, 2016

Explosion Detection and Suppression Systems

explosion detection system
Explosion detection system (by Fike)
A typical explosion detection sequence begins when a spark or other ignition source ignites particulate in a vessel. The resulting deflagration grows at an exponential pace as the material burns. The pressure front preceding the deflagration expands, reaching the pressure detector connected to the explosion protection control panel, which processes 4,000 data points per second. The system alarms at a preset pressure level, and activates the gas cartridge actuators on the suppression and isolation devices. The system maintains a history event for future reference.

The gas cartridge actuator drives the piston on the isolation valve, closing the slide gate and provides mechanical isolation which prevents the propagation of the explosion through the duct work to interconnected vessels. The actuator opens a rupture disk on the suppressor bottle, that uses nitrogen pressurized to 900 PSI to drive suppressant into the vessel, filling the entire cavity and extinguishing the advancing deflagration.

It is also necessary to isolate the deflagration, preventing the transmission of the flame into interconnected vessels. The system simultaneously opens a rupture disk on an isolation container that uses 500 PSI of nitrogen to drive suppressant into the ductwork, providing a chemical isolation barrier that prevents the propagation of the explosion. Fike’s explosion protection system effectively saves lives and property from explosion damage.

Thursday, January 28, 2016

Advanced Differential Pressure Flowmeter Technology

McCrometer V-Cone
McCrometer V-Cone
The McCrometer V-Cone® flowmeter accurately measures flow over a wide range of Reynolds numbers, under all kinds of conditions and for a variety of fluids. It operates on the same physical principle as other differential pressure-type flowmeters, using the theorem of conservation of energy in fluid flow through a pipe.

The V-Cone’s remarkable performance characteristics, however, are the result of its unique design. It features a centrally-located cone inside the tube. The cone interacts with the fluid flow, reshaping the fluid’s velocity profile and creating a region of lower pressure immediately downstream of itself. The pressure difference, exhibited between the static line pressure and the low pressure created downstream of the cone, can be measured via two pressure sensing taps. One tap is placed slightly upstream of the cone, the other is located in the downstream face of the cone itself. The pressure difference can then be incorporated into a derivation of the Bernoulli equation to determine the fluid flow rate. The cone’s central position in the line optimizes the velocity profile of the  ow at the point of measurement, assuring highly accurate, reliable  ow measurement regardless of the condition of the  ow upstream of the meter.

The V-Cone is a differential pressure type flowmeter. Basic theories behind differential pressure type flowmeters have existed for over a century. The principal theory among these is Bernoulli’s theorem for the conservation of energy in a closed pipe. This states that for a constant  ow, the pressure in a pipe is inversely proportional to the square of the velocity in the pipe.

Simply, the pressure decreases as the velocity increases. For instance, as the fluid approaches the V-Cone meter, it will have a pressure of P1. As the fluid velocity increases at the constricted area of the V-Cone, the pressure drops to P2. Both P1 and P2 are measured at the V-Cone’s taps using a variety of differential pressure transducers. The Dp created by a V-Cone will increase and decrease exponentially with the flow velocity. As the constriction takes up more of the pipe cross-sectional area, more differential pressure will be created at the same flowrates.

Monday, January 11, 2016

Mass Flow Rate and More From Multivariable Transmitter - Process Measurement and Control

Multivariable mass flow measurement transmitter
Model EJX 910A Multivariable Transmitter
Courtesy of Yokogawa
Industrial process measurement and control is charged with continually producing better, faster, and cheaper results with increasing levels of safety. For applications requiring mass flow rate measurement of fluids or tank level, a multivariable transmitter has much to offer when it comes to improving outcomes throughout your industrial process operation.

The EJX 910 series from Yokogawa provides the latest generation of digital sensing and processing to provide fast and accurate process measurement of temperature, static pressure, differential pressure, and dynamically compensated mass flow. Flow accuracy as high as +/-1.0% is achievable, along with:

±0.04% Differential Pressure Accuracy
±0.1% Static Pressure Accuracy
±0.9°F External Temperature Accuracy

Some other highlights include:

  •  Industry leading fast response time for safe and accurate process control.
  • Yokogawa's specially developed DPharp digital sensor providing simultaneous static and differential pressure measurement, digital accuracy, and no A/D conversion error.
  • LCD display can be rotated in 90 degree increments. External zero adjustment screw and range setting switch enhance field setup.
  • Improved mass flow accuracy of +/- 1% from multivariable operation in one device with dynamic compensation.
  • Signal characterizer for measuring level in irregular shaped tanks.
  • Utilizes industry recognized open communication protocols for easy integration into existing installations.

The manufacturer's white paper, describing precisely how the unit works and how it can be applied, is below. Browse the white paper for some additional detail, but consult with a product specialist to explore how to improve your process measurement and control performance. They have even more information than is provided here which, when combined with your process knowledge, is sure to generate a positive solution to any challenge.

Process Control - Five Categories of Instrument Protection

Industrial process temperature and pressure gauges
Instrument protection is a key element of process design
and equipment layout
The performance of every process is critical to something or someone. Keeping a process operating within specification requires measurement, and it requires some element of control. The devices we use to measure process variables, while necessary and critical in their own right, are also a possible source of failure for the process itself. Lose the output of your process instrumentation and you can incur substantial consequences ranging from minor to near catastrophic.

Just as your PLC or other master control system emulates decision patterns regarding the process, the measurement instrumentation functions as the sensory input array to that decision making device. Careful consideration when designing the instrumentation layout, as well as reviewing these five common sense recommendations will help you avoid instrument and process downtime.

Process generated extremes can make your device fail.

Search and plan for potential vibration, shock, temperature, pressure, or other excursions from the normal operating range that might result from normal or unexpected operation of the process equipment. Develop knowledge about what the possible process conditions might be, given the capabilities of the installed process machinery. Consult with instrument vendors about protective devices that can be installed to provide additional layers of protection for valuable instruments. Often, the protective devices are simple and relatively inexpensive.

Don't forget about the weather.

Certainly, if you have any part of the process installed outdoors, you need to be familiar with the range of possible weather conditions. Weather data is available for almost anywhere in the world, certainly in the developed world. Find out what the most extreme conditions have been at the installation site....ever. Planning and designing for improbable conditions, even adding headroom, can keep your process up when the unexpected occurs
Keep in mind, also, that outdoor conditions can impact indoor conditions in buildings without climate control systems that maintain a steady state. This can be especially important when considering moisture content of the indoor air and potential for condensate to accumulate on instrument housings and electrical components. Extreme conditions of condensing atmospheric moisture can produce dripping water.

Know the security exposure of your devices.

With the prevalence of networked devices, consideration of who might commit acts of malice against the process or its stakeholders, and how they might go about it, should be an element of all project designs. A real or virtual intruder's ability to impact process operation through its measuring devices should be well understood. With that understanding, barriers can be put in place to detect or prevent any occurrences.

Physical contact hazards

Strike a balance between convenience and safety for measurement instrumentation. Access for calibration, maintenance, or observation are needed, but avoiding placement of devices in areas of human traffic can deliver good returns by reducing the probability of damage to the instruments. Everybody is trained, everybody is careful, but uncontrolled carts, dropped tools and boxes, and a host of other unexpected mishaps do happen from time to time, with the power to inject disorder into your world. Consider guards and physical barriers as additional layers of insurance.

Know moisture.

Electronics must be protected from harmful effects of moisture. Where there is air, there is usually moisture. Certain conditions related to weather or process operation may result in moisture laden air that can enter device enclosures. Guarding against the formation of condensate on electronics, and providing for the automatic discharge of any accumulated liquid is essential to avoiding failure. Many instrument enclosures are provided with a means to discharge moisture. Make sure installation instructions are followed and alterations are not made that inadvertently disable these functions. Moisture also is a factor in corrosion of metal parts. Be mindful of the extra degree of protection provided by special coatings or materials that may be options for your instruments.

Developing a thoughtful installation plan, along with reasonable maintenance, will result in an industrial process that is hardened against a long list of potential malfunctions. Discuss your application concerns with a knowledgeable instrument sales engineer. Their exposure to many different installations and applications, combined with your knowledge of the process and local conditions, will produce a positive outcome.