Thursday, December 21, 2017

Capsule Steam Traps

cutaway view capsule steam trap
Capsule type steam trap, cutaway view
Image courtesy Tunstall Corporation
Steam traps are an important part of a closed steam system, directing condensate on a path back to the boiler for reuse and venting non-condensing gases from the system. Of the several different types of steam traps utilized commercially, the thermostatic steam trap is but one. Thermostatic traps are often applied when the application can benefit from a utilization of some of the heat remaining in the condensate. This trap design will hold the condensate in place until it cools sufficiently below the saturation temperature of the steam.

Capsules utilized in thermostatic steam traps contain the controlling elements of the device. The parts are somewhat subject to wear through their movement, but more so from the corrosive effects of system fluid, impurities, and mechanical shock from water hammer. Tunstall Corporation specializes in the manufacture of replacement capsules for thermostatic steam traps that provide better service and extended warranty duration. Their sealed units are fabricated of stainless steel and welded to seal out deterioration due to exposure to steam and condensate. Drop in replacement capsules are available for conceivably every trap manufactured in the previous few decades.

Share your steam system requirements and challenges with application specialists, leveraging your own knowledge and experience with their product application expertise to develop an effective solution.

Wednesday, December 13, 2017

Process Tuning

sliding gate industrial process control valve
This sliding gate industrial control valve could operate
under the command of a tuned process control loop.
Image courtesy Schubert & Salzer
Controller tuning is a process whereby a controlling device in a process has a response characterized to the needs of maintaining a process condition within certain limits under a range of varying disturbances to the process. Established guidelines for automation standards exist so that every process control operator can experience the same standard of safety and maintenance in a way universally understandable. The International Society of Automation (ISA) promotes different tuning standards based on the particulars of the control process, such as temperature or liquid level control.

Liquid-level control loops are usually considered non-self-regulating processes. They require external moderation to remain uniform and for errors to either be mitigated or corrected. General rules which exist for adjusting and tuning loops for self-regulating process, such as temperature control, are often inapplicable to liquid level loops, making liquid level control loops somewhat unique in their tuning.

In order to address the counter intuitive nature of these process loops, start with a model of the loop’s ideal functionality. This can serve as a reference. After doing so, incorporate potential variables into the ideal loop and evaluate their impact on the model process. Checking equipment, then modeling the process dynamics, allows engineers to observe the manner in which the process reacts in relation to the target or goal performance.

Whereas other loops can be tuned via trial and error, liquid-level control loops should not be due to the nature of their reactions to controller input being different than that of other processes. Instead, the parameters for the control loop need to be carefully engineered, rather than specifically tuned. Liquid level loops are integrating processes, rather than self-regulating. A self-regulating process will, with no disturbances to the variables, reach an equilibrium at which the process value remains constant. Consider a non-self-regulating liquid level control loop where the fill valve is open. No equilibrium point will be achieved, just overflow. The distinction between the two types is key to understanding why tuning liquid level loops is a different process than self-regulating control loops.

Temperature and thermal loops, depending upon the process dynamics, present varying degrees of tuning challenge. PID temperature controllers are employed to adjust the heat input to a process to affect a change in, or maintenance of, a process temperature setpoint. Without proper tuning, the controller output and the resulting process performance can oscillate or be slow to respond, with a negative impact on process performance or yield. Many PID controllers have an auto-tune feature, some of which are more effective than others. The best results achievable by PID controller tuning are accomplished by defining a setpoint prior to the auto-tune process and starting the tuning procedure from a stable process condition. Tuning the controller in the same process environment in which it will operate can also be very helpful.

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

Thursday, December 7, 2017

Compressed Air as a Motive Force

coalescing filters for compressed air
Coalescing filters are common components of a compressed
air system.
Image courtesy SPX Pneumatic Products
Compressed air is utilized throughout every industry and many commercial settings. While primarily used as a motive force, compressed air serves as a utility in many applications in the oil and gas, chemical and petrochemical, nuclear power, food, pharmaceutical, and automotive industries. The presence and use of compressed air across multiple industries is so essential, its importance is comparable to utilities like electricity, gas, and water.

In the control of fluid processes, compresses air facilitates operation and control of valves and other instruments. Dry air, with a sufficiently depressed dew point, can ensure process materials and equipment stay free of moisture and its associated impediments to smooth operation. The use of compressed air as either a motive force or a utility imparts minimum requirements on its quality or constituents. Confounding substances, such as particulates, water, and oil, may be entrained or contained in a compressed air stream. Various methods of filtration and moisture removal may be necessary to condition or process the compressed air in order to deliver consistent quality.

The advantages of using compressed air as a motive force in industrial settings are more numerous than appropriate for listing here, but consider that tools driven by compressed air can be more compact, lower weight and less prone to overheating than electrically driven tools. Air driven devices tend to have reduced parts count and require little maintenance, whether tools, valve actuators, pistons, or other machines. Compressed air driven devices can be fashioned to amplify the power of an electrical signal, enabling a simpler means of powering some types of loads. Compressed air, by its nature, presents no electrical hazards to the workplace.

Whenever air driven devices are utilized, attention must be given to compressed air production. The pressure, maximum flow rate demand, and compressed air quality must meet the process or operation requirements. Share your compressed air system challenges with specialists, leveraging your own knowledge and experience with their product application expertise to develop effective solutions.

Tuesday, November 28, 2017

Pipeline Cyber Security

binary stream representing industrial process control network data transfer and cyber security threat
Cybersecurity is a process control challenge that consistently evolves as new technologies come into use and new threats emerge. Since process control methods are constantly developing, the protective measures need to match the rate of change to ensure adequate levels of protection are in place. Pipelines used in the oil and gas industry, as well as in the transportation of a multitude of liquid and gaseous products, account for more than 2.3 million miles of process piping in the United States.  Natural gas pipelines are commonly monitored and controlled by, for example, programmable logic controllers or other microprocessor and communications based systems, responsible for flow regulation and various process conditions. Because of the prevalence of these systems, they are a target of increasing attacks, on both PLCs and other SCADA related devices, such as compressors, remote terminal units, communication networks, and other critical process infrastructure elements.

While developments in technology have provided operating advantages and improvements to the process industries, the more complex and advanced the systems may also increase the exposure to malicious penetration and mischief by unauthorized parties (hackers). Because of this, diligence by industry professionals, while always a strong component of protecting against outside threats, has been augmented via new guidelines meant to better prepare all process operators against more coordinated cyber-attacks.

Basic preventative measures, such as a firewall, are no longer a sufficient bulwark against the increasing threats. Instead, the entire process must be evaluated and monitored so that each individual piece of the network is understood fully. If a part of the system starts behaving in an abnormal way, then an understanding of what that specific PLC or component affects must be immediately known. The most effective protective programs will be able to function without needing any downtime, and will also be able to learn the network easily. Whenever the defense program gets triggered, it needs to not only provide a general alert to the process operator, but must also be able to provide context so that the previous knowledge of how the system works can be applied to mitigate the current problem.

Currently, the oil and gas industry has transitioned to what is being termed a ‘holistic’ approach to cyber defense. In order for the best security possible to be employed, the human element of process control must function in tandem with the autonomous programs. The human component of process operation, where it exists, can be unpredictable and present vulnerabilities that may not be known or anticipated. Everything must be considered.

Industrial process operation involves many areas of risk, with cyber attack being just one. The right kind of planning and response to risk can mitigate the potential impact. Security efforts, technology, and knowledge must keep pace with threats which emerge to process pipeline security. Mountain States Engineering and Controls participates in the oil and gas industry throughout the western U.S.

Thursday, November 16, 2017

Forced Draft Cooling Tower With 20 Year Warranty

corrosion resistant HDPE cooling tower rated 50 tons with forced draft
Forced draft corrosion resistant cooling tower
with forced draft, rated 50 tons. Pioneer series.
Image courtesy Delta Cooling Towers
Delta Cooling Towers specializes in the design and construction of corrosion resistant cooling towers and similar equipment. Much of the tower construction is HDPE or other non-metallic material, enabling the company to offer a 20 year warranty on their equipment.

Cooling towers are employed worldwide in HVAC applications and process fluid cooling. In addition to their industry leading corrosion resistance, Delta Cooling Towers also offers anti-microbial protection which combats the growth of microbes responsible for Legionnaires Disease and other respiratory ailments. The various product lines cover heat transfer capacities to accommodate any installation.

There is a lexicon employed in the description of cooling tower performance and operation. Some commonly used terms, along with their meaning, is provided below. The terms and their meanings is pulled from the owner's manual provided by Delta Cooling Towers for their Pioneer series of forced draft cooling towers.

Share your process and HVAC cooling challenges with application experts, leveraging your own knowledge and experience with their product application expertise to develop an effective solution.

Cooling Tower Terms and Definitions

  • BTU - A BTU is the heat energy required to raise the temperature of one pound of water one degree Fahrenheit in the range from 32° F. to 212° F.
  • Cooling Range - The difference in temperature between the hot water entering the tower and the cold water leaving the tower is the cooling range.
  • Approach - The difference between the temperature of the cold water leaving the tower and the wet-bulb temperature of the air is known as the approach. The approach fixes the operating temperature of the tower and is a most important parameter in determining both tower size and cost.
  • Drift - The water entrained in the air flow and discharged to the atmosphere. Drift loss does not include water lost by evaporation. Proper tower design and operation can minimize drift loss.
  • Heat Load - The amount of heat to be removed from the circulating water through the tower. Heat load is equal to water circulation rate (gpm) times the cooling range times 500 and is expressed in BTU/hr. Heat load is also an important parameter in determining tower size and cost.
  • Ton - An evaporative cooling ton is 15,000 BTU's per hour.
  • Wet-Bulb Temperature - The lowest temperature that water theoretically can reach by evaporation. Wet-Bulb Temperature is an extremely important parameter in tower selection and design and should be measured by a psychrometer.
  • Pumping Head - The pressure required to pump the water from the tower basin, through the entire system and return to the top of the tower.
  • Make-Up - The amount of water required to replace normal losses caused by bleedoff, drift, and evaporation.
  • Bleed Off (Blowdown) - The circulating water in the tower which is discharged to waste to help keep the dissolved solids concentrating in the water below a maximum allowable limit. As a result of evaporation, dissolved solids concentration will continually increase unless reduced by bleed off.

Friday, November 10, 2017

Hydrostatic Pressure Liquid Level Measurement

differential pressure tank level indicator
Tank mounted differential pressure transmitter
measures hydrostatic pressure to derive liquid level
Image courtesy King-Gage
Liquid level can be inferred by accurately measuring the pressure produced by the height of a fluid column and knowing the density of the liquid measured. The measurement is comparative in nature, referencing some external pressure as a zero point. The zero point can be the surrounding atmospheric pressure, tank pressure, or the pressure exerted by another column of liquid contained elsewhere.

There are uncountable application scenarios, each with its own set of special conditions. Proper instrument selection, installation and calibration are essential to generating reliable and accurate results.

The King-Gage TeleSensor™ liquid level transmitters are specially designed to provide level measurements across a wide range of liquids using a force balance principle in a pneumatic sensor. Sensor output can be either a pneumatic signal or 4-20 mA. The pneumatic force balance arrangement provides immunity to long term drift, hysteresis and temperature changes. A diaphragm isolates the sensor from the process liquid. Mounting is compatible with 2", 3", or 4" class 150 ANSI flanges. Various options for diaphragm and flange materials are available to accommodate a range of process media.

More detail is provided in the document included below, along with application examples. Contact product specialists to share your application challenges and get effective solutions.

Thursday, November 2, 2017

Steam Condensate Return Stations

duplex condensate return station
Duplex condensate return station
Image courtesy Roth Pump
Closed steam systems produce condensate, a dense source of heat. By design, the delivery of heat in a steam system is almost entirely accomplished using the heat of vaporization, with any sensible heat transfer probably being more coincidental than intentional. Condensate will contain most of the sensible heat that was added to the feedwater to get it to the boiling temperature. Conserving that sensible heat through a reuse of the hot condensate is a huge energy saving step. The condensate must be collected and returned to the boiler in a effective manner.

A condensate return station is a common means of moving condensate back to the boiler. It will generally consist of a collection vessel for the liquid condensate and one or more pumps to provide the motive force to move the liquid along its return path. Reliability is a key factor for these systems, since it is conceivable that they may need to perform on a continuous basis for years. A duplex pump arrangement can provide some backup, as well as extra capacity for accommodating large inlet flow. This is an installation where investing in rugged hardware can pay dividends in reduced maintenance burden and trouble free performance for the long term.

Roth Pump Company has been designing and manufacturing condensate return stations and other steam system related components for many years. Their experience and expertise are part of each and every system that leaves their factory. By incorporating low RPM motors, heavy duty pumps, and other features into a compact form factor, the company is able to offer a number of systems that meet a wide range of applications and deliver solid long term performance.

Share your steam system and condensate return requirements and challenges with application experts, leveraging your own experience and knowledge with their product application expertise.