Measurement Impossible: Three level measurement challenges in small vessels and how radar can overcome them
Small-batch production is no longer solely the domain of bourbon and whiskey distillers. Many chemical and pharmaceutical companies use batching as a means of increasing efficiency and lowering costs of manufacturing seasonal or low-demand products. Typically, these processes occur in smaller vessels that present unique challenges to level measurement.
Why radar for level?
Manufacturers have several methods of level measurement available to them, but this paper will focus on through-air radar instruments. The reason for this is simple: Radar is the best level measurement technology on the market. Able to operate effectively without contact, radar is invulnerable to corrosive media and it measures through glass and plastic. Furthermore, radar is impervious to the temperature changes, pressure shocks, and heavy vapors that are common to many chemical and pharmaceutical processes. Finally, modern radar level instruments are designed to become more reliable over time by virtue of self-learning echo processing. In terms of accuracy and reliability, through-air radar is the gold standard. This paper will look at three common challenges to level measurement in small vessels and what operators should look for in a radar device to overcome those challenges.
Challenge One: Internal obstructions
Regardless of the industry, vessels tend to get crowded. Agitators exist in process vessels for various products, everything from antibiotics to chemicals to ice cream. Heating coils take up valuable real estate at the bottom of tanks, and existing measurement devices leave little room for a radar beam. All of these internal installations have the potential to reflect a radar instrument’s pulses, resulting in inaccurate level measurement.
Solution: Higher transmission frequency
Avoiding internal fixtures calls for a using a radar beam that focuses more like a laser, so plant operators should look for radar with a high transmission frequency. Generally speaking, the higher the transmission frequency, the narrower the beam angle and the less susceptible a radar signal is to picking up interference from agitators, fittings, or buildup on vessel walls. A tight radar beam can be positioned to miss any internal installations and measure nothing but the media, even down to the very bottom of the tank.
Challenge Two: Media with poor reflective qualities
Some liquids are chemically difficult to measure; that’s just their nature. This is often due to a low dielectric constant. Liquids with a low dielectric constant, chlorine for example, are not easily polarized, making them resistant to radar technology.
Solution: High dynamic range
A sensor’s dynamic range is incredibly important, as large dynamic range ensures measurement certainty and makes a device suitable for a broader range of applications. The greater a sensor’s dynamic range, the more accurately it can measure media with poor reflective properties, including those with a low dielectric constant. Even foam, turbulent product surfaces, condensation, and antenna buildup are no problem for a radar sensor with large dynamic range, as market-leading instruments can overcome these difficult conditions.
Challenge Three: Limited space
This challenge is the Achilles’ heel of small batch producers, the constant thorn in their side. Space is at a premium for small production setups and limited quarters often prevent operators from even considering radar for level measurement. Radar pulses need to be focused with an antenna to ensure they direct at the media and don’t go scattering all over a vessel. Larger antennas, however, are close to half a foot long, and consume too much valuable space for practical use in a small vessel.
Solution: Smaller antenna
It behooves small-batch producers to choose a radar sensor with the smallest possible antenna. The VEGAPULS 64, for example, features the world’s smallest antenna; it is situated inside the sensor’s process fittings, allowing operators to capitalize on as much vessel space as possible.
Small-batch production is a trend with staying power for chemical and pharmaceutical manufacturers because it allows them to remain flexible and quickly meet changing consumer demand. It follows then, that if batching is here to stay, so is the use of small vessels and the need for accurate level measurement therein. Vessel size doesn’t preclude manufacturers from using radar technology for level if they find an instrument with the transmission frequency, dynamic range, and antenna size to meet their particular demands.