Part 1: What Steam Is, How Steam is Used, and the Properties of Steam

Steam is the gaseous phase (state) of water and has many domestic, commercial, and industrial uses. There are two categories of steam - wet steam and dry steam. In dry steam, all the water molecules stay in the gaseous state. In wet steam, some of the water molecules have released their energy (latent heat) and begin condensing into water droplets.

Steam, usually created by a boiler burning coal or other fuels, became the primary source of energy for mechanical movement during the industrial revolution, ultimately being replaced by fossil fuels and electricity.

Steam has many commercial and industrial uses. In agricultural, steam is used to remediate and sterilize soil. In power generation, approximately 90% of our electricity is created using steam as the working fluid to spin turbines. Autoclaves use steam for sterilization in microbiology labs, research, and healthcare facilities. Many commercial and industrial pieces of equipment are cleaned with steam. Finally, commercial complexes, campuses and military buildings use steam for heat and humidification.

The following video, the first part of a three part series titled “What Steam Is, How Steam is Used, and the Properties of Steam” provides the viewer with an exceptional basis to build from. Special thanks to Armstrong International who created the original work.

For more information on any industrial or commercial steam application, contact:

Mead O'Brien, Inc.
www.meadobrien.com
(800) 892-2769

Coriolis Flowmeter Reduces Sucrose Losses with Better Molasses Production at Sugar Mill

Molasses Production at Sugar Mill

A sugar mill typically loses between one and two percent of its incoming sucrose to factors such as poor clarification, sugar crystal elongation, reduced crystal growth rates, filter cake loss, and loss to molasses. Of these, loss to molasses is most significant — and one of the most difficult to prevent. Loss to molasses results from inaccurate flow measurement that causes more than the required amount of sucrose to pass into the molasses recipe. Wasting valuable sucrose can directly affect profitability of molasses batch yields, so new strategies to control this loss are constantly being investigated.

Improved control begins with a reliable measurement of molasses production, but getting that is indeed a challenge. Estimating undetermined sugar loss to within 0.1 percent, for example, requires molasses loss measurement that is accurate to at least one percent.

There are a number of methods that have been employed to measure molasses quantities in sugar mills around the world, each with distinct advantages and limitations. Measuring storage tank levels on a regular basis is probably the simplest method, but readings are inconsistent and unreliable. The error in the mass estimate affects the undetermined loss directly. Further complicating accuracy are chemical reactions that produce carbon dioxide, which affects both density and tank levels.

Another method is production tank dipping, which involves detecting changes in ow based on changes in torque at various measurement points. While this may be adequate for reporting on a volume basis, most molasses production balance is based on mass. Also, molasses is usually aerated, which creates two-phase flow conditions, further compromising density and accuracy.

Foxboro Coriolis Flowmeter

Engineers at this sugar mill compared measurements made by tank dipping and batch weighing to conventional and digital Coriolis measurements at various points over a three-year period. Years earlier, they installed a competitor’s conventional Coriolis meter. Shortly after, they installed a Foxboro CFT50 digital Coriolis transmitter from Foxboro in series with the existing unit. The Foxboro meter uses digital flowtube control that overcomes flow interruption or stalling caused by two-phase flow. And finally, a short time later, as a benchmark for accuracy, they installed a set of molasses batch scales. Valve leaks notwithstanding, they assumed that the scales would provide the most faithful measure of flow.

The measurements from tank dipping were ten to fifteen percent lower than estimates obtained from either of the Coriolis meters tested.

Later, with the batch scales installed, both Coriolis meters recorded consistently higher estimates than the scales readings. On average, the Foxboro meter gave readings that were three percent higher, and the conventional meter read nine percent higher.

It was clear that the Coriolis meters followed the batch scales much more closely. This strongly indicates the unreliability of tank dipping measurements and suggests that the Coriolis meters are also more responsive to real changes in flow rate. An unanticipated result also indicated that the digital Coriolis meter might be the most responsive to sudden changes in flow rate.

While acknowledging the need for additional study, the researchers concluded that Coriolis measurement is the only suitable alternative to batch scales for measuring sucrose loss to molasses. They found that the conventional Coriolis meter tended to estimate higher than the Foxboro Coriolis meter and that the Foxboro meter had a significantly faster response time in on/off applications.

Conductivity Sensors Improve Biodiesel Production Quality and Production

Biodiesel production improvement
with conductivity sensors.

Biofuel products are made from a variety of feedstocks, primarily soybean oil, vegetable oil and animal fat derivatives. Biodiesel is a safe alternative fuel replacement for traditional petroleum diesel.

The biodiesel production process is done through a chemical reaction that combines vegetable oil or animal fat as a raw stock, methanol, and a catalyst of sodium methylate in proper proportions. The process, called transesterification, involves chemically converting triglycerides to smaller methyl esters that resemble diesel fuel with extra oxygen atoms that make it oxygenated diesel fuel enabling it to burn cleaner.

Producing biodiesel fuel is a difficult task that requires precise separation at various stages. Effective separation is critical to the success of the process and the quality of the product.

The plant has four 20,000-gallon reactors and approximately 15 process vessels of various sizes, as well as large field storage tanks used in the delicate separation process.

When emptying the reactors its very important to know exactly where the interface is between the biodiesel and byproducts. If byproducts are left in the fuel, product quality standards are not met and material have to be reprocessed. If your pour out biodiesel, you’re throwing money down the drain.

Conductivity sensors (courtesy of Foxboro)

There are a number of ways to detect phase changes, but conductivity sensing seemed ideal for this application. A conductivity measurement system is relatively inexpensive, very clean and maintenance free, since there are no moving parts.

Foxboro, a world-class manufacturer of process control equipment was called in for a consultation. The initial application is in a batch mode where the company has a pump on the bottom of the reactor. Directly downstream of that pump is a “T” configuration that houses the Foxboro conductivity sensor. At this stage, the biodiesel company needs to separate glycerin, which has a relatively high conductivity, approximately 4,000 to 5,000 microsiemen/cm.  The Foxboro probe monitors the conductivity of the fluid passing by and, as the interface occurs, it immediately detects a dramatic drop in conductivity because the methyl ester phase has a conductivity of less than 20 microsiemen/cm. The conductivity sensor then triggers a signal to stop the pump and close the valve. The remainder of what is in the reactor is methyl ester that contains contaminants including excess methanol, glycerin, soaps, catalyst and other impurities.

The second application involves removing these components from the biodiesel fuel before it can be released as a final product. The crude biodiesel is mixed with water to scrub out the impurities, and then the water is allowed to settle to the bottom of the reactor. Because wash water has a high conductivity of about 2,500 microsiemen/cm, the Foxboro sensors can immediately detect the interface between methyl ester and wash water.

After the washing, the biodiesel goes to the final phase where a vacuum dehydrator warms the wet biodiesel and draws out any residual water. In this third application the Foxboro conductivity sensing probe is used to determine when the appropriate amount of water is removed. At that point what remains is finished biodiesel fuel.

Conductivity sensing technology allowed the successful automation of critical phase separation processes and will allow additional and ongoing process improvements such as automated and continuous processing, and further improvements in production efficiencies and more consistent product quality are expected.

Types of Pressure Measurements Used in Process Control

Pressure gauge
(courtesy of Ashcroft)

Pressure, the measure of a force on a specified area, is a straightforward concept, however, depending on the application, there are many different ways of interpreting the force measurement.

As with any type of measurement, results need to be expressed in a defined and clear way to allow everyone to interpret and apply those results correctly. Accurate measurements and good measurement practices are essential in industrial automation and process environments, as they have a direct effect on the success of the desired outcome.

When measuring pressure, there are multiple units of measurement that are commonly used. Most of these units of measurement can be used with the international system of units, such as kilo, Mega, etc.

This white paper (courtesy of Turck) will identify the various units of pressure measurement, while discussing when and why certain pressure measurements are used in specific applications.

Explanation of the Types of Pressure Measurements Used in Process Control from Mead O'Brien, Inc.

Using Eductors for Non-Powered Tank Mixing

Eductor for tank mixing
(courtesy of Jacoby Tarbox)

An eductor is a pump that uses a fluid to perform the work of pumping another fluid (or solid). The fluid doing the work is termed the motive fluid, and the fluid being pumped is the suction fluid. The motive fluid employed can be liquid. gas or steam. The suction fluid can be liquid. gas or steam. Other names for eductors include jet pumps, ejectors, Venturi pumps, siphon pumps, steam siphons, and injector pumps. Eductors operate on basic principles of flow dynamics.

Eductors require no power, which means no moving parts. The design of the eductor creates pressure differential allowing fluid to flow naturally within the device - creating suction, mixing, and pushing the liquid throughout the tank.

In-line eductors are the next generation of jet pumps, ejectors, and Venturi pumps providing in-line mixing, pumping, or heating in various process lines. Eductors reduce costs as there are no moving parts and require no direct power.

The video below, while marketing oriented, does a great job at demonstrating how tank mixing is accomplished efficiently and thoroughly with an array of eductors by calculating tank size and volume along with material properties to develop a mixing profile.

For more information, contact:

Mead O'Brien
(800) 892-2769
www.meadobrien.com

Theory of Operation for MOVs (Motor Operated Valves)

Limitorque SMB MOV

This presentation, provided by the NRC, provides an introductory look at motor operated valves, with a focus on the manufacturer Limitorque. The document includes the theory of operation of MOVs, plus descriptions of valve types, such as gate, globe, ball, plug and butterfly.

This document also provides detailed descriptions of Limitorque SMB actuators and Limitorque SB actuators with full assembly and subassembly breakdown and illustrations.

NRC Course on Motor Operated Valves and Limitorque from Mead O'Brien, Inc.

Document provided by NRC.gov

The Rack and Pinion Style Pneumatic Valve Actuator

Rack & Pinion Actuator
(courtesy of Flowserve Automax)

Three primary kinds of valve actuators are commonly used: pneumatic, hydraulic, and electric.

Pneumatic actuators can be further categorized as scotch yoke design, vane design, and the subject of this post - rack and pinion actuators.

Rack and pinion actuators provide a rotational movement designed to open and close quarter-turn valves such as ball, butterfly, or plug valves and also for operating industrial or commercial dampers.

The rotational movement of a rack and pinion actuator is accomplished via linear motion and two gears. A circular gear, referred to a “pinion” engages the teeth of a linear gear “bar” referred to as the “rack”.

Pneumatic actuators use pistons that are attached to the rack. As air or spring power is applied the to pistons, the rack is “pushed” inward or “pulled” outward. This linear movement is transferred to the rotary pinion gear (in both directions) providing bi-directional rotation.

Visual of rack and pinion
(courtesy of Wikipedia)

Rack and pinion actuators pistons can be pressurized with air, gas, or oil to provide the linear the movement that spins the pinion gear. To rotate the pinion gear in the opposite direction, the air, gas, or oil must be redirected to the other sides of the piston, or use coil springs as the energy source for rotation. Rack and pinion actuators using springs are referred to as "spring-return actuators". Actuators that rely on opposite side pressurization of the rack are referred to as "direct acting".

Most actuators are designed for 100-degree travel with clockwise and counterclockwise travel adjustment for open and closed positions. World standard ISO mounting pad are commonly available to provide ease and flexibility in direct valve installation.

NAMUR mounting dimensions on actuator pneumatic port connections and on actuator accessory holes and drive shaft are also common design features to make adding pilot valves and accessories more convenient.

Fully automated valve with rack
and pinion actuator, solenoid, and
limit switch.

Pneumatic pneumatic rack and pinion actuators are compact and save space. They are reliable, durable and provide a good life cycle. There are many brands of rack and pinion actuators on the market, all with subtle differences in piston seals, shaft seals, spring design and body designs.

For more information on any pneumatic or electric valve automation project, contact:

Mead O’Brien, Inc.
www.meadobrien.com
10800 Midwest Industrial Blvd
St. Louis, Missouri 63132
Phone (314) 423-5161
Toll Free (800) 874-9655
Fax (314) 423-5707
Email: meadstl@meadobrien.com

Steam Trap Testing Guide for Energy Conservation

Annual steam trap testing schedule

Below is a steam trap testing guide (courtesy of Armstrong International) to maximize efficiency and conserve energy. This guide discusses:

• Steam Trap Testing Procedure 
• Tips On Listening 
• Inverted Bucket 
• Float & Thermostatic Trap 
• Disc Trap 
• Thermostatic Trap 
• Sub-Cooling Trap 
• Traps on Superheated Steam

CAUTION: Valves in steam lines should be opened or closed by authorized personnel only, following the correct procedure for specific system conditions. Always isolate steam trap from pressurized supply and return lines before opening for inspection or repair. Isolate strainer from pressurized system before opening to clean. Failure to follow correct procedures can result in system damage and possible bodily injury.

Steam Trap Testing Guide for Energy Conservation from Mead O'Brien, Inc.