Case Study From CSB - Industrial Plant Heat Exchanger Failure

Shell and tube heat exchangers at industrial plant

Industrial accidents, whether minor or catastrophic, can serve as sources of learning when analyzed and studied. Operators, owners, and technicians involved with industrial chemical operations have a degree of moral, ethical, and legal responsibility to conduct work in a reasonably and predictably safe manner without endangering personnel, property, or the environment. Part of a diligent safety culture should include reviewing industrial accidents at other facilities. There is much to learn from these unfortunate events, even when they happen in an industry that may seem somewhat removed from our own.

The U.S. Chemical Safety Board, or CSB, is an independent federal agency that investigates industrial chemical accidents. Below, find one of their video reenactments and analysis of an explosion that occurred at a Louisiana chemical processing plant in 2013. A portion of the reenactment shows how a few seemingly innocuous oversights can combine with other unrecognized conditions that result in a major conflagration.

Check out the video and sharpen your sense of awareness for potential trouble spots in your own operation.

Industrial Wireless Communications Using a Single Transmitter and Multiple Receivers

Water treatment plant

In planning a wireless installation for connecting process measurement instruments and equipment to monitoring and control stations, keep in mind that it is not necessary to maintain a one-to-one relationship among receivers and transmitters. A transmitter broadcasts the process signal on a designated channel. All the receiving devices set to that channel will receive the 256 bit encrypted signal. Each can decrypt the signal and convert the value to a common industrial analog signal for use as needed. The key takeaway is to recognize that once the process signal is transmitted, you have the ability to receive and use the signal anywhere within range of the transmitter. Effective range can extend from a few feet to several miles.

The beneficial applications for industrial wireless are limited only by your imagination and ingenuity. Share your ideas and challenges with the industrial wireless experts at Analynk, combining your own process knowledge with their application expertise to develop an effective solution.

Wireless Communications For Process Control

The incidence of wireless connections between process measurement devices and their monitoring and control stations has been expanding for years, with costs receding and performance increasing. Designers, engineers, and operators of industrial processes and facilities continue to find new applications and create continuous wireless connections to devices and equipment that were previously isolated by distance or other barriers. They are also saving cost, promoting flexibility, and reducing "clutter" in facilities by eliminating cables, conduits, and junction boxes previously used to transmit measurement signals between instruments and control or recording gear.

Analynk Wireless builds the wireless transmission and receiving equipment needed to establish connections among your process measurement and control equipment and instruments. Transmitters, receivers, and repeaters that are rugged and uncomplicated in their application. Share your wireless connectivity challenges with the experts at Analynk, combining your process knowledge with their technical expertise to develop an effective solution.

New Wireless Access Point Enclosure For Hazardous Areas

New Model AP622 Access Point Enclosure

Analynk manufactures enclosures for industrial wireless access points, facilitating their installation in hazardous locations. Each access point enclosure is specifically targeted and designed to provide easy installation of specific wireless access points from a range of manufacturers. Every model is provided with UL listed explosion proof antennas, a mounting bracket designed for the target access point, and RF cables to make the antenna connections. Enclosures have penetrations specifically located to accommodate the target access point.The current offering accommodates a range of units from Symbol, Cisco, Meru, Aruba, HP, and Motorola, with more models added regularly to accommodate additional wireless access points.

The newly added AP622 is designed for the Aruba AP-304 dual band access point. Analynk Wireless specializes in industrial wireless communications. Your wireless communication challenges are welcome at Analynk, so make contact and share your application requirements. Combining your process expertise with Analynk's product specialization will produce an effective solution.

The datasheet for the new model is provided below. You can see all the models and their companion access points on the Analynk site.

Hazardous Area Wireless Access Point Enclosure from Analynk Wireless, LLC

Preventing Cavitation in Process Control Valves

Special valve trim can help prevent
cavitation
Courtesy Flowserve - Kammer

Cavitation in process control valves results from a rapid drop in pressure as liquid passes through the valve. The condition results in the formation of vapor spaces or bubbles within the valve cavity. When the bubbles move downstream into a larger cross-sectional area, velocity decreases and liquid pressure increases. The higher pressure now surrounding the bubbles causes them to implode, producing shockwaves which propagate through the liquid. These shockwaves can cause metal fatigue and excessive wear on the internals of the valve. The collapsing bubbles also make a discernible sound with accompanying vibration. The cumulative effects of cavitation can cause rapid deterioration of valve internals, resulting in reduced control function, frequent need for service, or premature failure.

There are ways to mitigate cavitation. Some involve changes in the process, others, incorporating a properly designed and selected valve with trim that reduces or prevents the conditions that cause cavitation. The paper below is authored by Flowserve, a globally recognized manufacturer of process control valves under several brand names, and provides an in depth examination of the causes of cavitation, then continues with explanation of how their specialty valves are designed to overcome the conditions that promote it. At Analynk Wireless, we are not in the valve business, but recognize many of our customers operate fluid processes and would find the knowledge useful. There are detailed illustrations showing specific valve trim features that impede cavitation.

Analynk Wireless manufactures a comprehensive line of wireless receivers, transmitters, and accessories that enable process operators to establish signal connections across the room, across the plant, and across the globe.

Cavitation Control in Process Control Valves from Analynk Wireless, LLC

Cooling Towers: Operating Principles and Systems

Cooling towers are found in a wide range of sizes
and configurations

The huge, perfectly shaped cylindrical towers stand tall amidst a landscape, with vapor billowing from their spherical, open tops into the blue sky. Such an image usually provokes a thought related to nuclear power or a mysterious energy inaccessible to the millions of people who drive by power plants every day. In reality, cooling towers – the hyperboloid structures most often associated with the aforementioned nuclear power plants – are essential, process oriented tools that serve as the final step in removing heat from a process or facility. The cooling towers at power plants serve as both an adjuster of a control variable essential to the process and also as a fascinating component of the process behind power creation. The importance and applicability of cooling towers is extensive, making them fundamentally useful for industrial operations in power generation, oil refining, petrochemical plants, commercial/industrial HVAC, and process cooling.

In principle, a cooling tower involves the movement of water through a series of different parts or sections to eventually result in the reduction of its heat content and temperature. Water heated by the process operation is pumped through pipes to reach the tower, and then gets sprayed through nozzles or other distribution means onto the ‘fill’ of the tower, reducing the flow of water to appropriate levels; this maximizes the amount of surface area for contact between water and air. Electric motor driven fans pull air into the tower, and when the air meets the water, a percentage of the water evaporates, carrying heat from the water to the air and resulting in the water being cooled. The cooled water then gets transferred back to the process-related equipment, and absorbs heat again, allowing for the cycle to repeat. The process and associated dispersion of heat allows for the cooling tower to be classified as a heat rejection device, resulting in waste heat being rejected to the atmosphere. Towers depend on either evaporation to remove the process heat (open loop) or solely on air (closed loop), without evaporation, to reduce the water temperature.

Thanks to their range of applications, cooling towers vary in size from the monolithic structures utilized by power plants to small rooftop units. Removing the heat from the water used in cooling systems allows for the recycling of the heat transfer fluid back to the process or equipment that is generating heat. This cycle of heat transfer enables heat generating processes to remain stable and secure. The cooling provided by an evaporative tower allows for the amount of supply water to be vastly lower than the amount which would be otherwise needed. No matter whether the cooling tower is small or large, the components of the tower must function as an integrated system to ensure both excellent performance and longevity of use. Additionally, understanding elements which drive performance - variable flow capability, potential HVAC ‘free cooling’, the splash type fill versus film type fill, drift eliminators, nozzles, fans, and driveshaft characteristics - is essential to the success of the cooling tower and its use in both industrial and commercial settings.

So, the next time an imposing tower cracks the horizon underneath a pillar of drifting vapor, imagine all the components inside working together in a beautifully aligned system towards a common industrial goal. Such is the ingenuity of technology.

Analynk Wireless manufactures wireless communications equipment that can be used to establish radio connections between remote located cooling tower monitoring equipment and central control stations. Fan motor current, air or fluid flow and temperature characteristics, and outdoor air conditions are just some of the cooling tower performance parameters that can be monitored.

Attaining Close Temperature Control of Flowing Process Liquids

Selection and placement of temperature sensors is a
critical element of achieving close temperature control.

Temperature control is a common operation in the industrial arena. Its application can range across solids, liquids, and gases. The dynamics of a particular operation will influence the selection of instruments and equipment to meet the project requirements. In addition to general performance requirements, safety should always be a consideration in the design of a temperature control system involving enough energy to damage the system or create a hazardous condition.

Let's narrow the application range to non-flammable flowing fluids that require elevated temperatures. In the interest of clarity, this illustration is presented without any complicating factors that may be encountered in actual practice. Much of what is presented here, however, will apply universally to other scenarios.

What are the considerations for specifying the right equipment?

KNOW YOUR FLOW

First and foremost, you must have complete understanding of certain characteristics of the fluid.

• Specific Heat - The amount of heat input required to increase the temperature of a mass unit of the media by one degree.
• Minimum Inlet Temperature - The lowest media temperature entering the process and requiring heating to a setpoint. Use the worst (coldest) case anticipated.
• Mass Flow Rate - An element in the calculation for total heat requirement. If the flow rate will vary, use the maximum anticipated flow.Maximum Required Outlet Temperature - Used with minimum inlet temperature in the calculation of the maximum heat input required.

MATCH SYSTEM COMPONENT PERFORMANCE WITH APPLICATION

Heat Source - If temperature control with little deviation from a setpoint is your goal, electric heat will likely be your heating source of choice. It responds quickly to changes in a control signal and the output can be adjusted in very small increments to achieve a close balance between process heat requirement and actual heat input.

Sensor - Sensor selection is critical to attaining close temperature control. There are many factors to consider, well beyond the scope of this article, but the ability of the sensor to rapidly detect small changes in media temperature is a key element of a successful project. Attention should be given to the sensor containment, or sheath, the mass of the materials surrounding the sensor that are part of the assembly, along with the accuracy of the sensor.

Sensor Location - The location of the temperature sensor will be a key factor in control system performance. The sensing element should be placed where it will be exposed to the genuine process condition, avoiding effects of recently heated fluid that may have not completely mixed with the balance of the media. Locate too close to the heater and there may be anomalies caused by the heater. A sensor installed too distant from the heater may respond too slowly. Remember that the heating assembly, in whatever form it may take, is a source of disturbance to the process. It is important to detect the impact of the disturbance as early and accurately as possible.

Controller - The controller should provide an output that is compatible with the heater power controller and have the capability to provide a continuously varying signal or one that can be very rapidly cycled. There are many other features that can be incorporated into the controller for alarms, display, and other useful functions. These have little bearing on the actual control of the process, but can provide useful information to the operator.

Power Controller - A great advantage of electric heaters is their compatibility with very rapid cycling or other adjustments to their input power. A power controller that varies the total power to the heater in very small increments will allow for fine tuning the heat input to the process.

Performance Monitoring - Depending upon the critical nature of the heating activity to overall process performance, it may be useful to monitor not only the media temperature, but aspects of heater or controller performance that indicate the devices are working. Knowing something is not working sooner, rather than later, is generally beneficial. Controllers usually have some sort of sensor failure notification built in. Heater operation can be monitored my measurement of the circuit current.

SAFETY CONSIDERATIONS

Any industrial heater assembly is capable of producing surface temperatures hot enough to cause trouble. Monitoring process and heater performance and operation, providing backup safety controls, is necessary to reduce the probability of damage or catastrophe.

High Fluid Temperature - An independent sensor can monitor process fluid temperature, with instrumentation providing an alert and limit controllers taking action if unexpected limits are reached.

Heater Temperature - Monitoring the heater sheath temperature can provide warning of a number of failure conditions, such as low fluid flow, no fluid present, or power controller failure. A proper response activity should be automatically executed when unsafe or unanticipated conditions occur.

Media Present - There are a number of ways to directly or indirectly determine whether media is present. The media, whether gaseous or liquid, is necessary to maintain an operational connection between the heater assembly and the sensor.

Flow Present - Whether gaseous or liquid media, flow is necessary to keep most industrial heaters from burning out. Understand the limitations and operating requirements of the heating assembly employed and make sure those conditions are maintained.

Heater Immersion - Heaters intended for immersion in liquid may have watt density ratings that will produce excessive or damaging element temperatures if operated in air. Strategic location of a temperature sensor may be sufficient to detect whether a portion of the heater assembly is operating in air. An automatic protective response should be provided in the control scheme for this condition.

Each of the items mentioned above is due careful consideration for an industrial fluid heating application. Your particular process will present its own set of specific temperature sensing challenges with respect to performance and safety. Share your requirements with temperature measurement and control experts, combining your process knowledge with their expertise to develop safe and effective solutions.