CTI Controltech Industrial Combustion and Process Control Blog: 2014

Electric Actuator for Fuel Oil Control Valve

Control Valve Actuator

In a Power Station burning both low-sulphur fuel oil and natural gas, an electric control valve actuator was installed on an outdoor fuel oil control valve application. The existing 6” ball valves which utilized a pneumatic I/P positioner and spring diaphragm pneumatic actuator wasn’t performing well. A decision was made to use a ROTORK CVA electric control valve actuator because it provides extremely precise control-valve operation with repeatability and resolution performance at less than 0.1% of full scale.

Because the valve operates outdoors, and modulates frequently to control the flow of fuel oil held in storage tanks to the fuel oil pumps, its a difficult application to get precise control. The built-in Bluetooth communications makes it easy to set up, calibrate and monitor performance.

The valve failure mode is also very important, in both loses-of-signal and loss-of-power. The specified ROTORK Actuators use a charged super capacitor and the built-in programming of the actuator control to assure proper “fail-to” in any event.

Happy Holidays and Happy New Year from CTi Controltech

We at CTi Controltech believe the magic of the Holidays never really ends and the most important gifts we share are are family and friends. Thank you for a wonderful 2014 and we wish you peace, love, and prosperity in the upcoming year. Happy Holidays and Happy New Year!

High-integrity Pressure Protection System (HIPPS) Valves

A HIPPS (high-integrity pressure protection system) is a category of "instrumented system" designed to prevent an over-pressurization condition at a process plant.

For oil, gas and chemical producers, loss of containment is a critical matter. Over-pressure on a tank, vessel or pipeline can potentially cause explosive, flammable, toxic or hazardous chemicals to be released causing possible loss of life or adverse effects on the environment. Loss of containment can also have huge negative effects on the plants bottom line.

HIPPS will shut off the source of the high pressure before the design pressure of the system is exceeded, as opposed to a relief system which will open an alternative outlet for the fluids in the system once a set pressure is exceeded. A relief system attempts to remove any excess inflow of fluids for safe disposal, where a HIPPS is designed to stop the inflow of excess fluids and containing them in the system. Conventional relief systems are increasingly frowned upon because they typically vent, flare or discharge hazardous or toxic fluids in to the environment.

HIPPS valves are used as the final part of an instrumented system intended to prevent an unacceptably high pressure occurring in downstream equipment. They are always arranged to fail closed and spring/hydraulic actuators are usually the only practical alternative for operation.

You can see a full application note on HIPPS relating to valves and ancillary systems here.

Industrial Burners and Safety Systems - Part Three

Igniters

Igniters provide proven ignition energy to immediately light-off the burner. They are permanently installed. Igniters are classified as follows by NFPA:

Class 3 special: High energy igniter (HEI) capable of directly igniting the main burner fuel. Generally consists of a spark-rod, and power pack to deliver the high voltage pulse train, and required cabling. Operation time of igniter is no longer than required to light-off burner, within maximum allowed trial-for-ignition time.
Class 3: Low capacity igniter applied particularly to gas and oil burners. Ignites the fuel input to the burner under prescribed light-off conditions. The range of class 3 igniters generally do not exceed 4 percent of full load burner input. Operation time of igniter is not longer than required to light-off the burner, within the maximum allowed trial-for-ignition time.
Class 2: Medium capability igniter applied particularly to gas and oil burners to ignite the fuel input to the burner under prescribed light-off conditions. The range of class 2 igniters generally is 4 to 10 percent of full-load burner input. Class 2 igniters may remain in operation to support ignition under low-load or adverse operating conditions. Class 2 igniters cannot be used to extend main burner turn-down range.
Class 1: High capacity igniter used to ignite the fuel input through the burner. Supports ignition under any burner light-off or operating conditions. Its location and capacity provide sufficient ignition energy at its associated burner to raise any credible combination of burner inputs of both fuel and air above the minimum ignition temperature. Tests are to be performed with this ignition system in service to verify that the igniter furnished meets the requirement of this class as specified in its design. Class 1 igniters can be used to extend the main burner’s turndown, where they are in service and flame if proved.

Industrial Burners and Safety Systems - Part Two

Combustion

Combustion (or burning) is a rapid combination of oxygen with fuel, resulting in a release of heat. Air (the oxygen source) is about 21% oxygen and 78% nitrogen by volume. Most fuels contain carbon, hydrogen, and sometimes sulphur. A simplification of combustion could be listed in the following three processes.

carbon + oxygen = carbon dioxide + heat
hydrogen + oxygen = water vapor + heat
sulphur + oxygen = sulphur dioxide + heat

These products of combustion are chemical compounds. They consist of molecules, combined in fixed proportions. Heat given off in any combustion process is excess energy which the molecules must release.

Stoichiometric combustion results when no fuel or air goes unused during the combustion process. Combustion with too much (excess) air is said to be lean or oxidizing. The excess air or oxygen plays no part in the combustion process. In fact, it reduces efficiency. Visually, excess air produces a short and clear flame. Combustion with too much fuel is called rich or reducing, producing incomplete combustion. This flame appears long and some- times smoky. The oxygen supply for combustion generally comes from ambient air.

Fireye Burner Safety Systems

Burners are simple devices that convert fossil fuels into heat energy. In order to achieve safe and reliable operation, each burner must be equipped with a monitoring and control system. The complexity of a safe and reliable system is relative to the complexity of the process at hand. This system can be as simple as a single burner using a single fuel, to a complex multi-burner environment where many burners fire into a common combustion chamber where multiple fuels are burned simultaneously. Conditions affecting the complexity of control systems is not necessarily dependent upon large burner input, but IS dependent upon the following conditions:

Type of process.
Type of burner.
Multi- or single burner environment.
Multi or single fuel operation.
Safety hazard of fuel burner.
Local codes and standards.
Redundancy and reliability factors.
Continuous or intermittent burner operation.

Recent technological advances require knowledge of applications and systems and should be applied only by qualified technicians. Standards are set by local authorities and must be understood and properly operated in order to assure that safety requirements are met.

Valtek ControlValve

Flow characteristics, the relationship between flow coefficient and valve stroke, has been a subject of considerable debate. Many valve types, such as butterfly, eccentric disk and ball valves, have an inherent characteristic which cannot be changed (except with characterizable positioner cams). Flow characteristics of globe valves can be determined by the shape of the plug head.

Control Valve Flow
Characteristics

The three most common types of flow characteristics are quick opening, equal percentage and linear. The adjacent figure shows the ideal characteristic curve for each. These characteristics can be approximated by contouring the plug. However, inasmuch as there are body effects and other uncontrollable factors, plus the need for maximizing the flow capacity for a particular valve, the real curves often deviate considerably from these ideals. When a constant pressure drop is maintained across the valve, the characteristic of the valve alone controls the flow; this characteristic is referred to as the “inherent flow characteristic.” “Installed characteristics” include both the valve and pipeline effects. The difference can best be understood by examining an entire system.

Equal Percentage

Equal percentage is the characteristic most commonly used in process control. The change in flow per unit of valve stroke is directly proportional to the flow occurring just before the change is made. While the flow characteristic of the valve itself may be equal percentage, most control loops will produce an installed characteristic approaching linear when the overall system pressure drop is large relative to that across the valve.

Linear

An inherently linear characteristic produces equal changes in flow per unit of valve stroke regardless of plug position. Linear plugs are used on those systems where the valve pressure drop is a major portion of the total system pressure drop.

Quick Open

Quick open plugs are used for on-off applications designed to produce maximum flow quickly.

This information provided courtesy of Flowserve Valtek. Further technical information can be found at this link.

Unique Design Rotary Ball Control Valve Provides Superior Control

This rotary ball control valve video (courtesy of MOGAS) provides an informative look at the flow conditions inside a valve designed with a tortuous flow path and specialized characterization.

The Flexstream rotary control valve uses a standard ball valve body with a very specialized ball. As the ball opens, the video shows the tortuous path. The design allows for volumetric expansion when controlling gas. Velocity, noise and cavitation are controlled by repeated 90 degree turns in the flow path. This design is excellent for applications that require wide range-ability.

Torque and Limit Switch Considerations When Applying Electric Valve Acuators

When selecting an electric actuator for industrial valves, an understanding of the valve torque requirements, both at start of travel, and end of travel, is critical for proper operation and optimal service life. Additionally, the ability to accurately set, or limit, disk travel is required.

Many of today's industrial electric valve actuators provide easy setting or programming of travel and torque sensing.

This short video provides a brief visual understanding of the reasons why valve torque and travel limits are important.

Heavy Duty Scotch Yoke Pneumatic Valve Actuator

Scotch yoke refers to a sliding linear mechanism that provides a reciprocating motion. One of the most common uses for scotch yokes are pneumatic valve actuators.

Scotch yoke mechanism
(courtesy of Wikipedia)

Scotch yoke valve actuators are designed to provide higher torque output for larger industrial valves. They typically have large pistons and air cylinders that provide the linear force required to open and close large quarter turn valves (ball, butterfly, plug).

Scotch yoke pneumatic actuators installed
in sea terminal
(courtesy of Rotork)

Scotch yoke actuators can be energized by either compressed gases, or hydraulic fluids. Here are some images of scotch yoke actuators in use:

Large spring return scotch yoke actuator
(courtesy of Rotork)

Commissioning a Jerguson Glass Level Gage with Safety Ball Check Valves

Here is a how-to video, courtesy of Clark-Reliance/Jerguson on starting up a glass level gage (gauge) with safety ball check valves.

Flame Discrimination and Detection for Multi-fuel Applications

Safe, reliable infrared and ultraviolet flame discrimination and detection for multi-fuel applications.

Flame scanners are used to detect emissions from fossil fuel flames. These can be gaseous fuel, light petroleum distillates, diesel fuels, heavy fuel oils and a variety of coals. They are suited for application to multiple burner furnaces in utilities and pulp and paper plants, industrial application such as petrochemical, refinery and chemical production, through to industrial boilers. Flame temperature measurement can be used to monitor and report on many applications including specialized burners used in applications such as Low NOx, Incineration and sulfur recovery.

An Industrial Electric Actuator Designed to Keep the Water and Dust Out

The Rotork IQ3 electric actuator includes a double o-ring seal to keep the internal parts sealed away from water and dust should the electrical conduit seals fail.

The Rotork IQ3 also includes these advanced features:

New intuitive user interface
Advanced dual stacked display with configurable datalogger functionality
Toughened glass screen plus optional environmental shield
Setting tool with secured Bluetooth® connection
High reliability, solid-state controls
Reduced internal wiring and connections
Simplified torque sensor
Simple and robust absolute position sensor with high reliability and accuracy
New thrust base design
Separable gearbox/thrust base across the range
Advanced real-time status reporting

Watch this video to see the how the IQ3 double o-ring seal keeps out water and dust.

Types of Level Instruments in Process Control

Tuning fork level controls
(form of echo level sensing)

In many industrial processes, the measurement of level is critical. Depending on the nature of the material being measured, this can be a simple or complex task. Several different technologies for sensing level are briefly explained here.

Sight Glasses or Sight Gauges
A very simple type of level measurement device for direct visual measurement of level in a tank or vessel. A sight gauge is usually a clear glass or plastic tube connected to the a vessel at the top and bottom of the level range needing to be viewed. As long as interface (different fluids with different densities floating on each other) the fluid level inside the vessel will be at the same hight as the level in the tube.

Choosing an improperly applied sized or improperly sized control valve can have serious consequences on operation, productivity and most important, safety. Here is a quick checkist of basics that need to be considered:

Not an isolation valve:
Control valves are not intended for isolating a process and should not be used as such. They are not intended to provide a bubble tight shutoff.

Choose the correct materials of construction:
The valve body, seat and wetted materials must be compatible with the process being controlled. Take into consideration pressure ratings and operating temperatures along with the material compatibility prior to valve selection.

Selective Catalytic
Reduction Systems

During the combustion process in large industrial or commercial boilers, the natural nitrogen in coal combines with oxygen forming nitrogen oxides (NOx). Nitrogen oxides in the atmosphere are unacceptable because they contribute to ground level ozone and undergo reactions in the atmosphere to form unwanted, and possibly harmful, fine particles.

Selective Catalytic Reduction (SCR) is a means of converting nitrogen oxides (NOx) to harmless nitrogen, water and trace CO2 by using an advanced emissions control system that injects a liquid-reductant agent, typically anhydrous ammonia, aqueous ammonia or urea, through a catalyst into the combustion exhaust stream.

The name "selective" derives because it selectively reduces levels of nitrogen oxides and "reduction" because of the chemical reaction where the ammonia or urea is the reducing agent converts NOx to nitrogen, water and CO2.

Commercial selective catalytic reduction systems are typically found on large utility boilers, industrial boilers, and municipal solid waste boilers. They have been shown to reduce NO by 70-95%.

SCR systems are one of the most cost-effective technologies available, while delivering great efficiency, being capable of reducing NOx emissions by up to 95 percent.

For more information on SCR's (Selective Catalytic Reduction Sytems) contact CTi Combustion.

The Eccentric Plug Rotary Control Valve (also known as the Rotary Globe)

Eccentric Plug Rotary Control
or Rotary Globe Valve
(courtesy of Cashco)

Available in either a flanged or flangeless body style, the rotary globe control valve design provides excellent service life in a wide range of applications. This rotary globe design provides front access to the valve body, allowing use of various low-noise inserts, abrasion sleeve or alternate front- end seal retainers, making it one of the most user friendly control valves when it comes to maintenance.

The rotary globe control valve is a universal control valve that can be used in most control valve applications, with particularly excellent performance on steam. Where conventional ball or globe control valves have problems with body or trim wear, the design and typical options for rotary globe control valves provides longer life. The ease and flexibility of installing characterized inserts provides noise control for gases, and cavitation and flashing control for liquids. Also because of its design, it inherently can withstand temporary distortions due to “thermal shock” without compromising continued control of the process.

A very versatile control valve that provides easy maintenance and serviceability, saving time and money for plant operations.

Flow Control Valve Tutorial

Since CTi Controltech sells, services and specifies industrial control valves in Northern California, we're always looking for helpful resources to educate our employees and our customers on control valve operation.

We recently found a great resource of tutorials courtesy of Columbia Gorge Community College that we thought we should share with you. The video we are showing is titled "Flow Control Valves" done by an instructor named Jim Pytel who does an excellent job.

Boiler MACT Help

Are you ready for Boiler MACT?
(photo courtesy of Victory Energy)

In March 2011, the Environmental Protection Agency (EPA) imposed a rule for stricter emissions limits on industrial boilers, commercial boilers and process heaters. The rule is known as Boiler MACT (which stands for "maximum achievable control technology". It is intended to affect the emissions of hazardous air pollutants with reduction to the highest degree possible, while still considering the costs incurred by achieving these reductions.

On January 31, 2013, after several stops and starts, the EPA published final amendments to the Boiler MACT rule.

There are two classes of pollution sources - area sources (minor) and major sources. For major sources the compliance deadline is January 31, 2016.

The rules will require some large facilities to undertake broad energy use assessments. The assessment includes inspections of boilers, operation & maintenance procedures, and drawings. A list of suggested efficiency improvements, with projected costs and an expense-recouperation timeline, must also be submitted.

Time is running out if you're a major source of HAP (hazardous air pollutants) and you need to act. The web site boilermactsolutions.org is an excellent resource and a great place to start.

Control Valves in Industrial Control Systems

Cashco rotary
control valve

One of the most ubiquitous final control elements in industrial control systems is the control valve. A control valve attempts to regulate flow through a pipe, reacting to a signal from some type of controlling device or balancing circuit, such as a simple on/off sensor, PID loop controller, or a programmable logic device (PLC). Control valves designs are available for simple (on/off) control of flow, or for more sophisticated applications that are intended to regulate flow between a fully opened valve and a fully closed valve.

Critical service valves, and the process equipment they protect, represent large capital investments in a manufacturing plant. To protect those investments, and the improve performance of your facility, a predictive maintenance inspection plan for severe service valves needs to be implemented.

Predictive maintenance inspections identify leaky valves, their severity and potential impact. The resulting report provides data that prioritizes critical issues immediately, while allowing time scheduling and budget allocation for lower priority issues.

Increasing process reliability results in greater plant efficiency and profits. Plants should routinely check their critical service valves for leaks, and repair or replace defective valves. Adoption predictive maintenance inspection will result in cost savings, greater process reliability and better safety.

Diagram of zirconia
sensor for oxygen
measurement.
(Courtesy of Wikipedia)

Oxygen analyzers are used to measure the quantity of oxygen in air or in other mixtures of gases, such as exhaust flue gas from a process. Oxygen, along with nitrogen and hydrogen, is a major component of air making up 20.9% of the air we breath. Oxygen is also used in the industrial combustion process, and when fuel is burned in presence of oxygen, CO, CO_2, and H₂O are by-products of that combustion. By measuring the oxygen in combustion process the proper air-to-fuel ratio can be maintained for optimized process efficiency.

Oxygen analyzers are used to determine exhaust gas concentration of oxygen in many applications from internal combustion engines to combustion applications in industrial plants. Many industries such as powergen, refineries, chemical plants, cement plants, asphalt production, and agrochemicals all require oxygen measurement.

Check out our little promotional video for CTi Combustion. For those who don't know, CTi Combustion specializes in combustion, steam, boilers and burners with engineering expertise in:

Class 1500 Ball Valve and Actuator Retrofit

rotork actuator with class 1500 ball valve

Class 1500, metal seated ball valve
with Rotork pneumatic spring return
actuator and hydraulic override.

CTi Controltech's broad engineering experience was recently challenged with the retrofit of a worn out globe valve and hydraulic actuator, to a new high pressure (Class 1500), metal seated ball valve and actuator package used on 10,000 lb. per hour steam system.

The customer is a large US Navy contractor located in Northern California. The application is the main steam stop valve on the contractor's steam boilers that provide steam for their turbine testing facility. The contractor's facility simulates conditions on US Navy ships so that turbines and related equipment can be properly tested.

One of the biggest challenges was to replace the valve and actuator in a very tight compartment. Space was extremely limited.

CTi, along with actuator manufacturer Rotork, came up with the right package to meet the very demanding operating conditions, as well as the working with the small space available.

The job involved the removal of the old globe valve and hydraulic actuator, and then having the new ball valve and pneumatic actuator package lowered through a hole cut in the facilities' roof. A very large crane, with a 200 foot boom, was used for the placement.

The new metal seated, Class 1500 ball valve was outfitted with a Rotork GP200 pneumatic, spring return actuator that included an hydraulic manual override.

The new valve and actuator package works exceptionally well, and the customer is very pleased CTi engineers came up with a solution that fit in to the existing space.

Ball Valves for Industrial Applications

Large industrial ball valve
(courtesy of MOGAS)

Perhaps the most universally used type of valve, ball valves come in a wide variety of sizes, materials, pressure classification, port configurations and end connections. They are applied in a multitude of industrial applications, and in every industry from chemical processing, to pulp and paper to food processing to bio-research.

A ball valve belongs to the quarter-turn family of valves, which means its rotational motion is 90 degrees to fully open of close the valve, allowing or stopping flow. Flow through the valve is accommodated by a sphere, or ball, with a hole through it. The ball is sandwiched between two seating rings, usually made of teflon or other elastomer. When the hole in the ball has its axis parallel to the valve ports, you have flow, when the hole is perpendicular, the flow is stopped.

Rack and Pinion Valve Actuators - A Look Inside

Here is an animation of the assembly components of a Flowserve Automax Supernova rack and pinion actuator with a transparent look inside to see its operation.

The critical components to take note of during the video are:

body
pinion gear
o-ring seals
piston "racks"
travel adjustments
end caps and seals
housing bolts

At the end, the video allows you to see the operation (in both directions) of the rack and pinion actuator as it is pressurized from either port. The pinion gear rotates 90 degrees, which in most applications, is used to open or close a valve or damper.

Introduction to Valve Parts or Components

Various types of industrial valves
(courtesy of Flowserve)

Industrial valves come in many shapes and sizes and they are classified according to different functions they have. Regardless of type, all valves have the following basic parts or components, the body, bonnet, trim, seat, stem, actuator, and packing.

Valve Body

The valve body is the primary boundary, housing or container. It serves as the main element of a valve assembly. It is the framework that holds all the parts together.

The body contains the fluid pressure loads from the inlet and outlet piping. The body connects to the piping via through threaded, flanged, or welded joints.

Sensing temperature

Temperature sensors are vital to everyday products and in the manufacturing of just about every product we use. Household ovens, refrigerators, and air conditioners all depend on temperature control to function properly. In the process industries, temperature control is essential in the production of chemicals, electrical power, food, communications, building materials, fertilizer, paper, plastics and petro-chemicals.

Temperature sensors are devices used to measure temperature of a medium (i.e. liquid, solid or gas). The sensor detects change in the temperature, and accordingly, change its physical or electrical property in a manner that can be measured. These sensors come in many different forms and are used for a wide variety of applications.

Electromagnetic
flowmeter
(courtesy of Azbil)

Flow measurement, the measuring of a flow rate for gasses, liquids and solids, is used throughout process applications in power generation, chemical manufacturing, petro-chemicals, pulp and paper, water and wastewater, bio-science, semiconductor and many other manufacturing processes. There two primary ways to measure the flow: volumetrically and by weight.

Flowmeters are used to measure the rate of flow (or quantity) of material in an open or closed system. They normally are installed on piping systems with the flow sensor immersed in the process medium.

Great Animated Movie Showing the Internals of a Control Valve

Here is a great video of the internal construction of a control valve (in this case its the Valtek MaxFlo 3 by Flowserve).

The animation is first class and reveals all the major internal parts of the valve and actuator. For anyone just learning about control valves, its well worth the 2 minutes to view.

Rack and Pinion Pneumatic Actuator Basics

A rack and pinion gear.
(Courtesy of Wikipedia)

Rack & Pinion actuators are designed for operating quarter-turn valves such as butterfly, plug, and ball valves or for actuating 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”.

In a pneumatic actuator, pistons are attached to the rack. As air or spring power is applied the to piston, the rack is “pushed” inward or “pulled” outward. This dual direction linear movement is transferred to the rotary pinion gear providing bi-directional rotation.

Five Advantages of Firetube Boilers

Five advantages of a firetube boiler over a watertube boiler are:

Firetubes provide the highest efficiency from the boiler without an economizer.

Lower capital cost.

Smaller footprint in most applications.

Less maintenance.

Easier to ship.

Below is a video that briefly describes the advantages and explains what a firetube boiler is (courtesy of Victory Engineering).

For more information on firetube or watertube boilers, call 925-208-4250 or visit www.cti-ct.com.

Welcome to The CTI Controltech Blog

The Internet has changed people's behavior. People do their own research. The first place anyone looks now for information is the Web. With this in mind, we're introducing the CTI Controltech Blog, a place where you can find educational information on industrial combustion and process control equipment.

We plan on providing regular posts about many topics including burner controls, boilers, process instrumentation, selective catalytic reduction (SCR) systems, engineered valves and valve automation. We'll try and deliver interesting and informative application notes and product introductions that will help you understand how these products work and interesting ways in which they are applied.

CTI Controltech Industrial Combustion and Process Control Blog