Measuring Fluctuating Temperature Water Level Using Density

A thermal power plant needed to measure the liquid level in a water storage tank, but due to mounting restrictions and space limitations, they are unable to use traditional liquid level sensing products.

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Another approach for indirectly measuring level of water in a storage tank is by using a differential pressure transmitter to measure pressure, and then calculating liquid level through calculating the density. However, the density of water changes with temperature; when temperature increases the water expands in volume and vice versa. This causes the water level to rise without varying the amount of pressure being applied to the transmitter’s sensors. If only a pressure measuring device is used, the system will lack the temperature data required for correctly adjusting the density calculations. Temperature compensation is needed to accurately determine the level of water within the process.

SOLUTION

An SOR 815DT Smart Differential Transmitter combined with an SOR 1400 Series Temperature Transmitter Assembly gave the plant personnel all the necessary information they required to calculate the density, and therefore, indirectly measure the water level. With the SOR 815DT’s compact design, it was able to be installed into confined areas where other instruments would be too large.

Both transmitters constantly measure the temperature and pressure and the process data is relayed to a digital control system. The temperature transmitter data is used to compensate the level readings accordingly. The combination of transmitters provides the digital control system with the process parameters needed for precisely calculating the density and thus, it is able to accurately determine the water level within the storage tank.

For more information regarding any level, pressure, temperature, or flow requirement, contact Instrument Specialties, Inc. by calling 407-324-7800 or visiting http://isi.group.

Water Quality Monitoring for Environmental Studies and Compliance

The right package of water quality instrument features
enhances effectiveness of field deployment.
Image courtesy In Situ, Inc.

There are many reasons to measure and monitor environmental water quality, chief among them compliance with local, state, or federal requirements. Other applications may call for water quality monitoring for environmental studies of various types. A sonde is an instrument used to collect water quality measurement data in the field. Whatever the issues driving a need for gathering environmental water data, selecting an instrument that combines accuracy, ruggedness, and ease of use can minimize the time and cost involved. There are a number of features to look for.

• Corrosion resistant construction that tolerates a wide range of targeted water sources.
• Minimized and simple setup procedure for quick deployment
• Low maintenance burden
• Smart sensor technology for best accuracy
• Extended measurement range for all parameters to accommodate broad range of water sources
• Low training requirement for technicians to be proficient at deploying sonde in the field
• Minimal sensor drift to increase available time in field and accuracy
• Modest or low frequency requirement for sensor calibration
• Sensor measurement stability. Higher level allows longer field deployment intervals.
• Sensors that are easily changed or replaced without need for high levels of technical training. Also allows for reconfiguring measurement scheme to target different constituents in the water.
• Sensors available for RDO, pH/ORP, turbidity, conductivity, temperature, pressure
• On board diagnostics monitor instrument operation for error
• Active and passive anti-fouling systems to automatically clean sensors, removing foreign matter that can impact measurements
• Extended field deployment time with low power consumption
• Real time data access, as well as on board data storage and other options for flexible data delivery.

These are some of the features that can result in effective data gathering and reduced manpower requirements to accomplish the task at hand. Share your water quality monitoring requirements with instrumentation specialists. Leverage your own knowledge and experience with their product application expertise to develop an effective solution.

Use Electronic Pressure Controllers in Your Research Process Loop to Eliminate Droop, Boost, and Hysteresis

(re-blogged with permission from Brooks Instrument)

Gas pressure control is critical in many applications like life sciences and chemical/petrochemical research where flow is an integral part of the process. Brooks Instrument electronic pressure controllers can be used as they require flow to function. Compared to using a mechanical pressure regulator, electronic pressure controllers eliminate droop, boost and hysteresis, offering stable pressure control.

There are two configurations available for pressure control – upstream and downstream. This terminology is somewhat unique to Brooks Instrument electronic pressure controllers.

Downstream vs. Upstream Pressure Control

Downstream pressure controllers maintain the pressure downstream of the device itself, increasing flow to increase the pressure and decreasing flow to decrease the pressure. For this reason, this is called direct acting. This configuration is commonly called a standard pressure regulator. A downstream pressure controller acts very similar to a typical mass flow controller because they are both direct acting.
Upstream pressure controllers maintain the pressure upstream of the device itself, increasing flow to reduce the pressure and decreasing flow to increase the pressure. For this reason, this is called reverse acting. This configuration is commonly called a back pressure regulator in the industry.

Selecting and Sizing an Electronic Pressure Controller

The following information is required to select and size a Brooks Instrument electronic pressure controller:

• Process gas
• Maximum flow rate being used to maintain pressure -The “sweet spot” for pressure control is between 100 SCCM and 5 SLPM.
• Calibration pressure (maximum pressure to be controlled)
• Reference pressure (for upstream controllers the reference pressure is the downstream pressure and for downstream controllers the reference pressure is the upstream pressure)

As long as flow is present in a process you will typically find the need for some type of pressure control. Vessel sizes up to 30 liters commonly use flow rates up to 3 SLPM during their process steps. Brooks Instrument pressure controllers are a perfect fit for these services, offering stable pressure control with no droop, boost or hysteresis, which are commonly experienced when using a mechanical pressure regulator.

Typical Bioreactor Process Using an Upstream Pressure Controller