Q&A for Ultrasonic Level Switches

Ultrasonic level switches with single
and multiple level measurement points
Courtesy Magnetrol International

Ultrasonic level switches appear, at first glance, to be a renamed version of a vibrating tuning fork level switch. They have a similar appearance and tank mounting scheme, but a closer look at the technology of the two instruments reveals that they rely on different operating principles to indicate when liquid level reaches their fixed switch point.

A previous article , with an accompanying video, provided some comparison between the two detection methods. Here is the operational difference summarized. A vibrating tuning fork device monitors the resonant frequency of the vibrating fork and responds when the frequency shifts due to immersion of the fork in liquid. An ultrasonic level switch transmits an ultrasonic pulse across a gap, measuring the intensity of the received signal and determining whether the signal passed through liquid (high level received signal) or air (low level received signal). While both technologies are effective, the ultrasonic level switch can be applied over a wider range of liquid density and does not require recalibration or adjustment for a change in media density.

Magnetrol International, globally recognized innovator in level measurement technology and instruments, recently answered a few application questions in their blog about their Echotel ultrasonic switches. The questions, along with answers penned by Magnetrol's product manager Tom Kemme, are shared here.

Question: Can ECHOTEL be used in applications that have entrained air?

Answer: Yes, ECHOTEL ultrasonic switches can be used in applications that have entrained air. All ECHOTEL gap switches feature a tip-sensitive transducer that provides superior performance over side gap transducers that are offered by other companies. Side gap transducers allow gas bubbles to adhere to the upper surface of the gap, which cause false dry gap alarms. Tip sensitive transducers allow these bubbles to pass through the gap. Applications with severe turbulence or entrained air should use the Model 961 switch, which offers a time delay adjustment. Up to 10 seconds of delay can be used to disregard entrained air and reliably detect the true liquid level.

Question: We are considering adding level alarm switches to our process to provide high-high level indication in several tanks. Instead of switches with relay outputs, we are considering the current shift output. What are the advantages of a current shift output?

Answer: Current shift electronics simply shift the current output from 8 mA when the level switch is in the normal operation, to 16 mA to indicate a level alarm. ECHOTEL Model 961 also has a user selectable fault signal of 3.6 or 22 mA. Current shift switches are 2-wire loop powered, which allows them to be offered with intrinsically safe approvals. This allows these switches to be put into hazardous area locations at a lower cost since rigid conduit is not necessary. Since current shift switches provide constant indication of either a normal (8 mA), alarm (16 mA), or a fault (3.6 or 22 mA) condition, they are sometimes referred to as a transmitter for the price of a switch.

Share your level measurement requirements and challenges with process measurement specialists, combining your own process knowledge and experience with their product application expertise to develop effective solutions.

Applying Coriolis Flowmeters

Coriolis Flowmeter
Courtesy Yokogawa

Coriolis mass flow meters are widely used throughout the process measurement and control field. Their basic operating principle, combined with modern sensor and signal processing technology, provide a list of potential application advantages.

• Directly measure mass flow based on the principle of measurement.
• No "moving" parts (except the slightly vibrating sensor tubes).
• Coriolis sensors have the ability to measure flow of non-conductive fluids.
• Measure the mass flow rate with high accuracy.
• Instruments can be applied across a wide usable measurement range.
• Deliver density measurement based on oscillating frequency.
• Not materially impacted by fluid viscosity or density.
• Coriolis flow meters also do not need lengthy straight pipe sections upstream or downstream of the sensing unit.

SELECTION AND INSTALLATION RECOMMENDATIONS

Some considerations for product selection and installation of Coriolis mass flow meters:

• Rapid temperature changes within the measured medium can impact measurement accuracy.
• Wide ranges of connection types are available, specify the best match for your system.
• Select sensor tube construction material to accommodate media characteristics.
• For liquid measurement, the sensor tube will extend downward from a horizontal pipe run. 
• As with most industrial products, there may be restrictions on where the device may be used. For example, not for use in aircraft. Assure that your application conforms with the intended usage of the instrument.
• Install at least one tight shutoff valve adjacent to the instrument for purposes of zeroing. Isolation valves for inlet and outlet are preferred.
• Follow manufacturer recommendations for pipe supports, if required, at inlet and outlet sides of the unit
• Avoid installation at locations with high levels of vibration or strong electrical fields.
• Locate the sensor unit at the lowest practical level in the piping system. This helps avoid collection of gas bubbles in the sensor tubes.
• Sensor tubes need to be completely filled with subject medium to obtain accurate measurement.
• Avoid the use of flexible connections and reducers at the unit connection points, unless in accordance with specific manufacturer guidelines.

The Coriolis flow meters of different manufacturers may have some particular recommendations, all of which should be followed to insure the best available performance, safety, and longevity of the unit.

Share your process instrumentation challenges and requirements with process measurement specialists, combining your process knowledge and expertise with their product application experience to develop effective solutions.

Specialty Valves for Biotech and Pharma Applications

Stainless steel ball valve for sanitary applications
Courtesy Habonim USA

Sanitary fluid process operations require the use of valves with unique characteristics that make them suitable for use. Materials of construction, FDA approved materials for seals, clean draining, and no retainage of the process fluid are some of the requirements for sanitary valves. Pharma and other bioprocess industries, including food and beverage, will also have stringent requirements for sterilizing or cleaning in place.

One manufacturer, Habonim, a globally recognized manufacturer of high quality ball valves, offers a complete line of ball valves specifically designed for sanitary process applications.

The TuBore™ valve series is available in line sizes from 1/4" to 6" with clamped or welded connections and available with manual operator, pneumatic or electric actuation.

The datasheet included below provides more detail and specifications. Share your sanitary fluid process control requirements and challenges with product specialists. Combining your process knowledge with their product application expertise will produce effective solutions.

Sanitary Ball Valves for Biotech and Pharma Applications from Miller Energy, Inc.

Succeeding: Engineer as Peacemaker

Make Allies, Not Adversaries

Let's take a step away from the technical, but still focus on an important aspect of our work.

As engineers involved in process measurement and control, we are accustomed to everybody else looking to us for answers and solutions. We are the people that make things work. Occasionally the pressure and stress can get a little intense and strip away some of our civility in our dealings with those around us. You may have bitter experience with this as either victim or perpetrator. It never ends well. With a private and candid self-assessment about how we view and interact with other stakeholders in our projects, we may be able to scale down some of our stress and better focus on the reality of the task at hand. Consider the points below. Comment and add a few points of your own.

You are an expert, but so are they.

Accept that, just as you have specialized knowledge that others do not, they have specialized knowledge or insight you may lack. Encourage the sharing of knowledge with those you interface with on a project. Try to be proactive and ask gently probing questions to ascertain the comprehension level of others involved in the project in various roles. Their increased understanding of key project technical concepts will promote more effective communication throughout the duration of the project. It can also help to avoid missteps in your own progress. Good people appreciate the time you take to provide basic explanation of concepts they may not fully understand, but need to know. Make valuable allies of the other project stakeholders by freely contributing your expertise. It is an investment that costs you little, but may pay immense dividends at some future time.

Everybody else's job usually looks easier than it really is.

All jobs have their own special challenges and responsibilities that generate stress. Accept the notion that you probably do not fully comprehend the burdens on those around you. Your portion of the project is certainly critical, but no more so than that of anybody else. Everybody needs to perform or nobody succeeds. Try not to view your project tasks as compartmentalized, but rather as part of the combined joint effort of all stakeholders. Help out others whenever you can. Again, make allies.  

Everybody is somebody's customer.

Whomever you deliver your work product to is your customer. The people delivering their work to you should view you as their customer. Make your customers happy by adjusting aspects of your procedures to better satisfy their needs. In a more technical sense, your modified process output becomes an improved input to their process. Small changes in your delivery may produce comparatively large returns in customer satisfaction. Allies.

Do not embarrass or demean others...especially in public settings.

Embarrassment breeds anger, a desire for revenge, and other bad and unproductive things. Avoid words and deeds that will make a coworker or stakeholder look bad in front of others. If there is a problem, if there is a mistake, try to deal with it discreetly whenever possible. Giving a someone a chance to repair a mistake before it becomes public builds value in your relationship. Certainly, there can be instances where more is at stake than someone's pride. Use good judgement to recognize when you can privately give someone an opportunity to amend a situation without causing harm.

Reach a common understanding of project scope and technical details

Your organization's management or your company's client, whatever the case may be, will likely have project expectations which will be clearly understood in their mind, but perhaps not fully described to all those tasked with specific performance. It is also possible, even probable, these same stakeholders will have misconceptions or a lack of technical knowledge about certain facets of the project. Omissions from the project specs and gaps in the common understanding of technical aspects related to the work requirements can easily turn a fairly straight forward task into a wildfire of organizational mayhem. The way in which these situations are handled must be diplomatic. Injured egos can do more damage to project harmony and progress than the facts ever will. The delivery method for the facts will likely be more crucial than the facts themselves.

It's not about being right. It's about being successful.

At our company we recognize customers are more than merely people that buy things from us. They are people to whom we contribute our time and talent to help achieve their success,... which inevitably will lead to ours. Never hesitate to let us know how we are doing, or how we can help.

Miller Energy - Industrial Instrumentation and Process Control Solutions

Miller Energy is a Manufacturer's Representative and Distributor of industrial instrumentation and process control equipment.  Miller is committed to exceeding customers expectations by providing an unparalleled level of customer service and local technical support.

Miller offers the most comprehensive line of measurement, control, and communication solutions in industry today. The products provided by Miller solve challenging applications in the industrial gas, power, refining, chemical / petro-chemical, food & beverage, water/wastewater, and pharmaceutical markets.

Welcome to the Process Measurement, Instrumentation and Control Blog, sponsored by Miller Energy

Welcome! We hope (over time) you find this blog interesting to visit and it becomes a trusted resource for process measurement and control. We plan on weekly educational and informative blog posts innovative process control solutions, insight to how industrial controls work, and new products that solve tough engineering challenges. Please come back often!