Wednesday, January 18, 2017

Application of Limit Switches on Automated Industrial Valves

industrial valve automation actuator and limit switch
Employed in a wide range of industrial applications,
limit switches are known for ease of installation,
simple design, ruggedness, and reliability.
Courtesy Flowserve Automax
Limit switches are devices which respond to the occurrence of a process condition by changing their contact state. In the industrial control field, their applications and product variations are almost countless. Essentially, the purpose of a limit switch is to serve as a trigger, indicating that some design condition has been achieved. The device provides only an indication of the transition from one condition to another, with no additional information. For example, a limit switch triggered by the opening of a window can only deliver an indication that the window is open, not the degree to which it is open. Most often, the device will have an actuator that is positively activated only by the design condition and mechanically linked to a set of electrical contacts. It is uncommon, but not unknown, for limit switches to be electronic. Some are magnetically actuated, though most are electromechanical. This article will focus on limit switch designs and variants used in the control and actuation of industrial process valves.

Valves, devices used for controlling flow, are motion based. The movable portions of valve trim create some degree of obstruction to media flow, providing regulation of the passage of the media through the valve. It is the movement of critical valve trim elements that limit switches are used to indicate or control. The movable valve trim elements commonly connect to a shaft or other linkage extending to the exterior of the valve body. Mounting electric, hydraulic, or pneumatic actuators to the shaft or linkage provides the operator a means to drive the mechanical connection, changing the orientation or position of the valve trim and regulating the media flow. Because of its positive connection to the valve trim, the position of the shaft or linkage is analogous to the trim position and can be used to indicate what is commonly referred to as “valve position”. Limit switches are easily applied to the valve shaft or linkage in a manner that can provide information or direct functional response to certain changes in valve position.

In industrial valve terms, a limit switch is a device containing one or more magnetic or electrical switches, operated by the rotational or linear movement of the valve.

What are basic informational elements that can be relayed to the control system by limit switches? Operators of an industrial process, for reasons of efficiency, safety, or coordination with other process steps, may need answers to the following basic questions about a process control valve:

  • Is the valve open? 
  • Is the valve closed? 
  • Is the valve opening position greater than “X”? 
  • Has the valve actuator properly positioned the valve at or beyond a certain position? 
  • Has the valve actuator driven the valve mechanism beyond its normal travel limits? 
  • Is the actuator functioning or failing? 
Partial or complete answers to these and other questions, in the form of electrical signals relayed by the limit switch, can serve as confirmation that a control system command has been executed. Such a confirmation signal can be used to trigger the start of the next action in a sequence of process steps or any of countless other useful monitoring and control operations.

Applying limit switches to industrial valve applications should include consideration of:

  • Information Points – Determine what indications are necessary or useful for the effective control and monitoring of valve operation. What, as an actual or virtual operator, do you want to know about the real time operational status of a valve that is remotely located. Schedule the information points in operational terms, not electrical switch terms. 
  • Contacts – Plan and layout a schedule of logical switches that will provide the information the operator needs. You may not need a separate switch for each information point. In some cases, it may be possible to derive needed information by using logical combinations of switches utilized for other discrete functions. 
  • Environment – Accommodate the local conditions and hazards where the switch is installed with a properly rated enclosure. 
  • Signal – The switch rating for current and voltage must meet or exceed those of the signal being transmitted. 
  • Duty Cycle – The cycling frequency must be considered when specifying the type of switch employed. Every switch design has a limited cycle life. Make sure your selection matches the intended operating frequency for the process. 
  • Auxiliary Outputs – These are additional contact sets that share the actuation of the primary switch. They are used to transmit additional signals with specifications differing from the primary signal. 
  • Other Actuator Accessories – Limit switches are often integrated into an accessory unit with other actuator accessories, most of which are related to valve position. A visual local indication of valve position is a common example. 
Switches and indicators of valve position can usually be provided as part of a complete valve actuation package, provided by the valve manufacturer or a third party. It is recommended that spare contacts be put in place for future use, as incorporating additional contacts as part of the original actuation package incurs comparatively little additional cost.

Employing a properly configured valve automation package, with limit switches delivering valve status or position information to your control system, can yield operational and safety benefits for the life of the unit. Good advice is to consult with a valve automation specialist for effective recommendations on configuring your valve automation accessories to maximize the level of information and control.

Friday, January 13, 2017

Electronic Line Break Detection - Pipeline Monitoring

electronic line break detector for oil and gas pipelines
Electronic line break detector unit
Courtesy Rotork
There are some process control challenges for which you may need to establish or produce a solution of your own design. These should be applications where a pre-engineered option or product is not available. A manufactured product for your application likely is comprised, not only of appropriate physical attributes suitable for the application, but also the experience gained from numerous successful iterations solving the same problem, challenge, or issue you currently face. There can be expertise, knowledge, and experience provided as part of a hardware item, and bringing that knowledge and experience of others into the solving of a process control challenge is sound practice.

Pipelines, when considered from differing organizational vantage points:

  • A source of revenue
  • A means of transportation
  • A pipe with fluid in it
  • An ongoing operation requiring monitoring and control
  • An extensive physical presence with an associated risk element
Pipelines are all those and more. Regardless of your vantage point, line breaks are decidedly negative events worthy of early detection and rapid response. Part of that solution is available in the electronic line break detection device from Rotork, globally recognized leader in the design and manufacture of valve actuators employed throughout the industrial sphere. The ELB model incorporates a set of features and capabilities that can be used to detect and respond to gas pipeline breaks. It is a self contained unit employing technology to detect line breaks and execute a predetermined response.

Read more about the ELB from Rotork in the document included below. It provides a detailed outline of the operational features of the unit. Share your fluid system control challenges with an experienced application team, combining your process knowledge with their product application expertise to develop effective solutions.



Tuesday, January 3, 2017

Application of Flame Scanners in Combustion Operations

single burner flame scanner sighting or alignment
Aim flame scanner through the largest cross sectional area of the flame
Courtesy Fireye
Flame detectors or scanners are regularly deployed in combustion applications as a means of confirming the presence of flame in a combustion chamber. The verification that fuel flowing into the utilization equipment is being properly burned and not accumulating unburned in the combustion chamber is the first line of safety in combustion.

Flame scanners use the characteristics of combustion and the electromagnetic emissions from burning fuel to detect flame and distinguish among flames from multiple burners. The instruments rely heavily upon operating principles utilizing visible, infrared, and ultraviolet light measurement and detection.

In single burner applications, simpler sensor and controller combinations can work suitably, but multiple flame applications are candidates for more complex detection devices and controls which can discriminate among multiple flames. Differences in individual flame characteristics, indicated through combustion products, can be utilized to distinguish between flames from different burners. Some photoelectric detectors can distinguish a signature flicker in flames of any type, invisible to the human eye.

Knowledge and understanding of the flame itself, its emissive attributes, and other characteristics are the key to proper flame detection. This may include the temperature of gases within the flame and its specific gas products. Other than temperature, electromagnetic radiation and ionized gas molecules in the flame are commonly used by flame scanners or detectors.

A variety of flame scanners are available for industrial and commercial use, each optimized for particular application sets. Essentially you have a scanner, which acts as a sensor. The signal from the scanner requires amplification and further processing to provide a reliable control signal. Hardware is available as discreet components, allowing a combination of scanner, amplifier, and control units to be combined into a system tailored for specific application requirements. Integrated systems are also available, with all appropriate detection and amplification circuitry built into a single compact unit.

Share your combustion process challenges with application specialists and combine your facility and process knowledge with their product application expertise to develop effective solutions.


Tuesday, December 27, 2016

Preventing Cavitation in Industrial Process Control Valves

cutaway view of mulit stage valve trim Flowserve Kammer Multi-Z
Example of multi-stage valve trim
designed to eliminate cavitation
Courtesy Flowserve - Kammer
In process control valves, cavitation results from a rapid drop in pressure as liquid passes through the valve. It results in the formation of vapor spaces or bubbles within the valve cavity. When the bubbles move downstream into a larger cross-sectional area, velocity decreases and pressure increases. The higher pressure now surrounding the bubbles causes them to implode, producing shockwaves which propagate through the liquid. These shockwaves can cause metal fatigue and excessive wear on the internals of the valve. The collapsing bubbles also make a discernible sound with accompanying vibration. The cumulative effects of cavitation can cause rapid deterioration of a valve, resulting in reduced control function, frequent need for service, or premature failure.

There are ways to mitigate cavitation. Some involve changes in the process, others, incorporating a properly designed and selected valve with trim that reduces or prevents the conditions that cause cavitation. The paper below, authored by Flowserve, provides an in depth examination of the causes of cavitation, then continues with explanation of how their specialty valves are designed to overcome the conditions that promote it.

There are detailed illustrations showing the specific valve trim features that impede cavitation. Share your process control valve challenges with application experts, combining your process knowledge with their product application expertise to develop effective solutions.


Tuesday, December 20, 2016

Self Defense Against Industrial Control System Cyber Threats

binary code industrial control system cyber security
Protection from cyber attacks and intrusions should be
a high priority wherever industrial automation is present
Industrial control system owners, operators, and other stakeholders should be aware of their exposure to malicious intrusion and attack by individuals or organizations intent on inflicting physical damage, stealing information, or generally wreaking havoc throughout an industrial operation. The risk of intrusion, regardless of the size or type of facility, is real and deserves the focused attention everyone involved in the design and operation of industrial control systems.

The National Cybersecurity and Communications Integration Center, part of the US Department of Homeland Security, ...
serves as a central location where a diverse set of partners involved in cybersecurity and communications protection coordinate and synchronize their efforts. NCCIC's partners include other government agencies, the private sector, and international entities. Working closely with its partners, NCCIC analyzes cybersecurity and communications information, shares timely and actionable information, and coordinates response, mitigation and recovery efforts. (from www.us-cert.gov/nccic)
The Industrial Control Systems Cyber Emergency Response Team (ICS-CERT) is a division under NCCIC. It has published a set of seven basic steps toward establishing a more secure industrial control system. I have included the publication below, and it is interesting and useful reading for all involved in industrial process control.

Having a fence around an industrial site, with a guarded entry gate, no longer provides the level of security needed for any industrial operation. Read the seven steps. Take other actions to build your knowledge and understanding of the risks and vulnerabilities. Cybersecurity is now another layer of design tenets and procedures that must be added to every control system. It will be a part of your company's best practices and success, now and in the future.

There are uncountable legacy controllers and communications devices throughout industrial America. All need to be reassessed for their vulnerability in the current and upcoming security environment. When reviewing your processes and equipment, do not hesitate to contact CTI-Controltech for assistance in your evaluation of our products.



Wednesday, December 14, 2016

Vertical Tubeless Boiler - Small Footprint for Hot Water and Steam Production

vertical tubeless boiler
Vertical Tubeless Boiler
Courtesy Williams & Davis Boilers
Steam and hot water are utilized in quantity throughout many industrial and commercial operations. Boilers, the most common production equipment for steam, are commercially available in a number of configurations, each with its own set of attributes making it an advantageous choice for a particular application.

One type of boiler is the vertical tubeless boiler, so named for the direction of combustion gas flow and its lack of tubes that are utilized in other designs.

Production capacity in a boiler is very dependent upon heat exchange surface area. The orientation of a vertical tubeless boiler results in a design with a significantly smaller footprint than a comparable horizontal boiler. This, obviously, can be very helpful if floor space is scarce in your facility. The rugged, simple design and lack of tubes tends to make these boilers very reliable and simple to maintain. Fueled by oil, gas, or a combination of the two, provides suitability for a wide range of facility installations. The burner is top mounted and the Williams & Davis unit pictured in this article comes fully trimmed and ready to install in most cases. Feedwater treatment and condensate return considerations are generally the same as for any other boiler.

The vertical tubeless boiler can have broad application in commercial and industrial facilities requiring a reliable source of hot water or pressurized steam. Share your hot water or steam requirements with combustion and boiler experts for the most effective solutions.

Thursday, December 8, 2016

General Purpose Valve for Targeted Applications

industrial butterfly valve with actuator handwheel
Industrial Butterfly Valve
Courtesy Adams Valves, Inc.
This is the Adams Valve WEK series industrial butterfly valve. It is a general purpose valve for many applications involving fresh water, seawater, sewage, hydrocarbon and wet gas.

The WEK valves feature low operating torque, compact design, low weight, and good control characteristics. The sealing system is completely integrated within the body of the valve, utilizing a laminated metal and graphite material. Available sizes range from 3" to 24".

Streamlining promotes smooth movement of the disc through its full travel range, without flutter induced by the flow moving around the disc. Sealing is accomplished when the disc rotates to the closed position and seals tightly against the seat which is incorporated into the body. Tight shut off results from the disc pushing into the seal. Valve operation can be manual, via a handwheel, or automated with a range of electric, hydraulic, or pneumatic actuators.

Share your fluid control, valve, and automation challenges with the engineers at CTI Controltech, combining your process and facility knowledge with their product and application expertise to develop the most effective solutions.