What are purged impulse lines and why are they needed?

Diagram of a purged impulse line implementation.
(image courtesy of Lessons in Industrial Instrumentation
by Tony R. Kuphaldt)

Purged impulse lines, or sensing lines, allow process transmitters and gauges to maintain operation under potentially adverse process conditions that may impact the operation or accuracy of the instrument. The purging of an impulse line is of particular use when sensing lines may have a high susceptibility to plugging by the process fluid. The line is purged with clean fluid at a constant rate, meaning new fluid is always being introduced into the impulse line. When the purge is properly set, a critical element of successful implementation, the pressure instrument is still able to correctly measure system pressure.

Purging a sensing line will require additional valves and devices to properly control the purge fluid flow and provide for effective maintenance or repair. Because of the increased relative complexity, a purging setup will likely be employed only in cases where other methods of maintaining clear sensor lines and proper instrument operation have been considered and rejected. The impulse line will stay free of sedimentation thanks to the purge fluid, and process fluid contamination of the sensing line is avoided.

One of the most important parts of the purged impulse line system is a restriction, implemented to prevent the pressure instrumentation from sensing the elevated pressure of the purge fluid supply instead of measuring the original process fluid. The purge valve, through which the purge fluid flows, is left partially open instead of fully open. If the restriction does not mitigate the introduction of the purge fluid on the process line, then the flow rate of the purge fluid can adversely impact the process measurement. It is essential that purge flow be regulated in a manner that does not adversely impact the measurement of actual process conditions.

A basic requirement of sensing line purge systems is that the supply of purge fluid needs to be flowing at all times. Additionally, the purge fluid supply pressure must be maintained at a level greater than the process pressure because if the pressure of the purge fluid supply drops below the process pressure, the process fluid will flow into the impulse line. The purge fluid must also not react negatively with or contaminate the process and will be continuously consumed. Generally, purge rates are kept as low as possible, mitigating purge fluid impact on the process measurement and keeping the cost low. A rotameter, which indicates visual flow of the purge fluid, is an item typically paired with purge impulse line systems, and there are many options available for use as purge fluids.

Common gases for purged impulse lines include air, nitrogen, and carbon dioxide. A purge system can be applied to both gas and liquid process systems. Share your process measurement challenges with instrumentation specialists. Combine your own process knowledge and experience with their product application expertise to develop effective solutions.

Swanson Flo Performance

Specialists in valves, automation and instrumentation, Swanson Flo Performance sets the standard for process control optimization and training that maximizes plant uptime, safety and operating efficiency.

• Valve automation center 
• Experienced staff of factory-certified technicians 
• Responsive on-call repair and service 
• Extensive OEM parts inventory 
• Third party audited standards 
• The region’s widest range of industry application experience 
• Comprehensive multi-brand process equipment knowledge

Please take a minute to watch the video below for more information.

Self-Operating Temperature Regulators

Jordan Mark 80

In process control applications, exceedingly close control with PID loops is not always necessary. There can also be instances where location or operational circumstance calls for temperature control, but not necessarily under the control of a centralized system. Self operated mechanical temperature regulators, with their reliable and simple operating scheme, can be well suited for these applications.

Self operated temperature regulators are basically valves with self contained actuation controlled by a filled system, or bulb. The valve portion of the assembly controls the flow of a fluid which impacts the process temperature. The process temperature is measured by a fluid filled bulb, connected via a capillary to a chamber containing a diaphragm. As the temperature of the process changes, the fluid in the bulb expands or contracts, changing the fluid pressure on the diaphragm. Pressure on the diaphragm causes movement, which is linked to the sliding gate trim of the valve, thus adjusting fluid flow. A spring provides a counteractive force on the diaphragm and allows for setpoint adjustment.

The self contained assembly requires no external power source to operate and requires little maintenance. Proper selection of line size, capillary length, bulb type, and temperature range are key elements in getting the right valve for the job. Application temperature ranges from -20 to +450 degrees Fahrenheit.

The Mark 80 Series Temperature Regulator features the advanced sliding gate seat technology pioneered by Jordan Valve. Using the Jordan Valve sliding gate seat technology, the Mark 80 temperature regulators have the signature straight-through flow, short-stroke that is 1/3 of a globe-style valve, quiet operation and tight shutoff. The Jordan Valve Mark 80 has high rangeability and extremely accurate regulation. The proprietary Jorcote seat material is extremely hard (@RC85) with a low coefficient of friction that delivers outstanding performance and long service life.

Share your temperature control and fluid flow challenges with product application specialists, combining you own process expertise with their product application know-how to develop the most effective solutions.

You can see all the details in the datasheet included below. For more information contact Swanson Flo by calling 800-288-7926 or visit http://www.swansonflo.com.

Jordan Valve Mark 80 Self Operated Temperature Regulator from Swanson Flo

Choosing Temperature Sensors for Industrial HVAC and Chiller Equipment

Sensors used in HVAC

Reprinted with permission from Gems Sensors & Controls white paper.

Efficient operation of industrial HVAC and chiller equipment depends upon optimum temperatures of refrigerant and lubricating oil at various phases of the refrigeration cycle. The most common sensors for this purpose utilize negative temperature coefficient (NTC) thermistors of various resistance values. NTC sensor devices exhibit lower electrical resistance when exposed to higher temperatures.

RTD

Either thermistor or RTD-type sensors may be used for this purpose, however thermistors are preferred for most applications due to cost and media exposure attributes. RTDs are more expensive, and the fragility of the sensing element require it to be separated from the sensed media within an enclosure. Thermistors are more durable, and may be immersed directly in any non-conductive fluid media being sensed, for quicker response to temperature changes. There is an inherent non- linearity in thermistor output that requires temperature and resistance correction for the output. Manufacturers of thermistors, and sensors made from them, can provide Resistance-to-Temperature curves for this purpose.

Assuming equivalent thermistor quality and resistance values, combining the thermistor within a housing that can be installed into HVAC or chiller equipment is what differentiates one sensor assembly from another. These fall into two basic types: exposed or enclosed thermistor housings.

Open sensor thermistor probe.

Exposed thermistors directly contact the fluid being sensed; in this application, those are refrigerant, oil, and oil/refrigerant emulsion, although they may be used in any non-conductive fluid. Direct contact with fluids provides faster and more accurate thermistor response. The downside to exposed thermistor sensors is leakage through the housing where the thermistor leads pass through sensor housings, especially in pressured installations. Leakage results in maintenance downtime for the operator and warranty issues for the equipment manufacturer.

Enclosed thermistors encase the thermistor inside a probe that is an integral part of the housing. These eliminate the leakage issue, but because the thermistor is actually in an air pocket surrounded by the metal or plastic housing, temperature compensation and sensor responsiveness issues are introduced.

A Recent Third Option

Gems Sensors & Controls has produced a third type of housing that combines the performance of an exposed thermistor design, while providing the hermetic sealing of an enclosed sensor housing. Known as the TM-950 Series, these thermistor-based temperature sensors were designed specifically to solve long-term reliability issues in HVAC and Chiller applications.

TM-950 Series temperature sensor incorporates a unique fused-glass technique to produce a hermetically sealed the housing. Molten glass is placed inside the heated housing. As the assembly cools the metal housing shrinks, compressing the glass. In addition, the boundary surface of heated metal and glass bond at a molecular level. Two nickel-plated steel tubes are positioned pre-positioned before the glass fusing process to provide a pass through for the thermistor leads. Any of a variety of thermistors may be utilized based on the temperature sensing profile required. Once leads are passed through the steel tubes and glass, induction soldering fills the tubes completely, providing a leak-proof seal to 450 psig. The result is a sensor with the benefits of direct fluid contact incorporating the leak-proof attributes of an enclosed sensor.

For more information on selecting sensors for industrial HVAC applications and chillers visit Swansonflo.com or call 800-288-7926

A Look Inside the Cashco Ranger QCT Industrial Control Valve

Cashco Ranger QCT
Industrial Control Valve

The Cashco Ranger is one of the most popular industrial control valves on the market. It is the most versatile, adaptable, and easily maintainable valve ever produced. No other valve is more user friendly.

The Ranger offers over 6 different trim combinations. Trim can easily be changed in less than 5 minutes without disturbing the packing, actuator, or positioner calibration. The service area is a thread-less design, which resists corrosion or collection of chemical deposits.

A selection of 3 body materials with a broad temperature range from -325°F to +750°F makes the Ranger adaptable for use in steam, heat transfer fluids, slurries, gases, liquids, and cryogenic applications. The Ranger’s unique dual seating design provides both Class VI and backup Class IV seat leakage. And the standard patented live-loaded packing system lets you check and adjust packing without the need for specialized tools or complicated procedures.

Check out the video below for a detailed look. For more information, visit Swanson Flo at http://www.swansonflo.com or call (510) 274-1990.

Lined Industrial Valves for Corrosive Service

Lined Plug Valves
(courtesy of Flowserve Durco)

Lined valves use a fluoropolymer, plastic, or ceramic lining applied to all wetted internal parts of the valve.

Lined valves combine the excellent mechanical properties of metallic bodies with the corrosion resistance of fluorocarbons, such as PFA and PTFE.

Lining the intricately shaped inside surfaces of a valve is certainly an engineering challenge, especially to achieve a uniform thickness and the highest lining quality, without cavities or inclusions.

Lined ball and swing check valve
(courtesy of Flowserve Atomac)

The special lining process guarantees tight bonding between the lining and the inside of the body.
This effectively prevents the lining from shearing off the body in part or being removed completely.

Ideal applications include highly corrosive applications within the chemical processing industry such as sulfuric and hydrochloric acid.

Lined valves are ideally suited for corrosive applications, requiring very reliable performance, tight shutoff, constant torque and no maintenance. These valves have gained extensive usage in many industries including power generation, pulp and paper, refineries, chemical process, pharmaceutical/bioprocessing and pollution control.

For more information on lined valves, visit Swanson Flo at http://www.swansonflo.com or call 800-288-7926.

Magnetic Flowmeters (Magmeters): Principles and Applications

Magnetic flowmeter (Foxboro)

Crucial aspects of process control include the ability to accurately determine qualities and quantities of materials. In terms of appraising and working with fluids (such as liquids, steam, and gases) the flowmeter is a staple tool, with the simple goal of expressing the delivery of a subject fluid in a quantified manner. Measurement of media flow velocity can be used, along with other conditions, to determine volumetric or mass flow. The magnetic flowmeter, also called a Magmeter, is one of several technologies used to measure fluid flow.

In general, magnetic flowmeters are sturdy, reliable devices able to withstand hazardous environments while returning precise measurements to operators of a wide variety of processes. The magnetic flowmeter has no moving parts. The operational principle of the device is powered by Faraday's Law, a fundamental scientific understanding which states that a voltage will be induced across any conductor moving at a right angle through a magnetic field, with the voltage being proportional to the velocity of the conductor. The principle allows for an inherently hard-to-measure quality of a substance to be expressed via the Magmeter. In a Magmeter application, the meter produces the magnetic field referred to in Faraday's Law. The conductor is the fluid. The actual measurement of a magnetic flowmeter is the induced voltage corresponding to fluid velocity. This can be used to determine volumetric flow and mass flow when combined with other measurements.

The magnetic flowmeter technology is not impacted by temperature, pressure, or density of the subject fluid. It is however, necessary to fill the entire cross section of the pipe in order to derive useful volumetric flow measurements. Faraday's Law relies on conductivity, so the fluid being measured has to be electrically conductive. Many hydrocarbons are not sufficiently conductive for a flow measurement using this method, nor are gases.

Magmeters apply Faraday's law by using two charged magnetic coils; fluid passes through the magnetic field produced by the coils. A precise measurement of the voltage generated in the fluid will be proportional to fluid velocity. The relationship between voltage and flow is theoretically a linear expression, yet some outside factors may present barriers and complications in the interaction of the instrument with the subject fluid. These complications include a higher amount of voltage in the liquid being processed, and coupling issues between the signal circuit, power source, and/or connective leads of both an inductive and capacitive nature.

In addition to salient factors such as price, accuracy, ease of use, and the size-scale of the flowmeter in relation to the fluid system, there are multiple reasons why Magmeters are the unit of choice for certain applications. They are resistant to corrosion, and can provide accurate measurement of dirty fluids - making them suitable for wastewater measurement. As mentioned, there are no moving parts in a Magmeter, keeping maintenance to a minimum. Power requirements are also low. Instruments are available in a wide range of configurations, sizes, and construction materials to accommodate various process installation requirements.

As with all process measurement instruments, proper selection, configuration, and installation are the real keys to a successful project. Share your flow measurement challenges of all types with a process measurement specialist, combining your process knowledge with their product application expertise to develop an effective solution.

The video below provides additional information about magnetic flowmeters.

Your Partner for Process Control Automation: Swanson Flo

Founded in 1960, Swanson Flo has long maintained our position as an industry leader in process automation with unmatched project success leveraging industry preferred products and services.

Our mission is to provide innovative process control solutions for engineers, managers and maintenance professionals through quality equipment and experienced application engineering. These efforts combined with excellent aftermarket service yield reduced operating costs and improved production. Visit http://www.swansonflo.com or call 800-288-7926.

Ashcroft Awards Swanson Flo Coveted "Distributor of Distinction Award"

For the fourth consecutive year, pressure and temperature instrument manufacturer Ashcroft, Inc. named Swanson Flo of Plymouth Minnesota the Ashcroft "Distributor of Distinction" for 2016. This award recognizes and honors Ashcroft Distributors who deliver exceptional growth, revenue, and commitment, and stands as Ashcroft's most respected and highest honor for their Distributors.

Swanson stood out from the pack in 2016 with a 17% increase in bookings over their previous year, despite a very tough economy for industrial distribution. Swanson Flo attributes the increase to their focus on developing new business at targeted accounts, increasing the size of their sales force, and turning up new applications at existing accounts.

From left to right:  Bill Johnson, Sales Manager, Western Division;

Robbin Jensen, Insides Sales Manager; Tom Howe, Owner/CEO,

Sandy Grinvalds, Ashcroft; and Sid Sondag, Director Sales & Marketing.

The Advantages of the Sliding Gate Control Valve Seat in Process Control

Sliding Gate Control Valve Seat (Jordan)

Fluid flow control in a process can present a number of challenges, large and small. In addition to selecting a properly sized control valve, your choice of trim design can contribute noticeably to overall positive performance. One candidate for fluid flow control is the sliding gate valve.

The trim of a sliding gate valve essentially consists of a fixed disc and a movable plate installed directly in the flow path. The disc and plate have precisely located and sized perforations, slots, or other openings. The valve actuation mechanism slides the plate across the face of the disc, progressively changing the alignment of the openings in the plate and fixed disc. This type of design can bring some benefits to the process and user:

• Short stroke length provides fast response, reduces wear on packing and diaphragm, allows for a compact installed assembly
• Straight-through flow pattern reduces turbulence, noise, erosion, valve chatter, and cavitation
• Ease of maintenance, with fewer trim components that are easily changed
• Self cleaning, self lapping seats

The video below provides a clear illustration of how the sliding gate valve trim works, through animation and exploded views of the valve components. Share your fluid flow control challenges with a valve specialist and combine your process expertise with their product application knowledge for an effective solution.

Continuous Non-contact Level Measurement for Process Control

LLT 100 Laser Level
Transmitter

ABB has released the new Model LLT 100 Laser Level Transmitter, which provides continuous non-contact level measurement for process automation and inventory management across a broad range of industrial applications.

The new transmitter provides reliable level measurement of solids or liquids, even clear liquids. The laser ranging technology is packaged with features required by industrial applications. Currently, three variants include housings for general industrial applications, as well as another for high pressure and one for hygienic installation.

The video blow provides a clear overview of the benefits that accrue from selecting this technology for your next project. More information is available from application specialists, with whom you should share your requirements and challenges to develop effective solutions.

Protect Your Instrumentation with Diaphragm Seals

Flanged diaphragm seal
(Ashcroft)

Pressure measurement is a common element of industrial operations and control systems. Fluid processing can often involve media that is potentially harmful to pressure sensing devices. The media may be corrosive to the sensor material, or other media properties may impact the performance or usable life of the instrument. In process control environments, diaphragm seals play a role in protecting items like pressure sensors from damage by process fluids.

The diaphragm seal is a flexible membrane that seals across the connecting path to a sensor and isolates the sensor from the process media. System pressure crosses the barrier without inhibition, enabling accurate measurement, but the process fluid does not. Typical materials composing diaphragm seals are elastomers, with a wide variety of specific materials available to accommodate almost every application.

In the operating principle of the diaphragm seal, the sealed chamber created between the diaphragm and the instrument is filled with an appropriate fluid, allowing for the transfer of pressure from the process media to the protected sensor. The seals are attached to the process by threaded, open flange, sanitary, or other connections.  Diaphragm seals are sometimes referred to as chemical seals or gauge guards. Stainless steel, Hastelloy, Monel, Inconel, and titanium are used in high pressure environments, and some materials are known to work better when paired with certain chemicals.

Threaded diaphragm seal

Sanitary processes, such as food, beverage, and pharmaceuticals, use diaphragm seals to prevent the accumulation of process fluid in pressure ports, a possible source of contamination. If such a buildup were to occur, such as milk invading and lodging in a port on a pressure gauge, the resulting contamination compromises the quality and purity of successive batches. Extremely pure process fluids, like ultra-pure water, could be contaminated by the metal surface of a process sensor. Some pneumatic systems rely on the elimination of even the smallest pressure fluctuations, and diaphragm seals prevent those by ensuring the separation of the process materials from the sensors.

Sanitary diaphragm
seal with pressure gauge.

Diaphragm seals are not without some application concerns, and devices are now built to address and counter many potential issues related to the use of diaphragm seals with process monitoring instruments and equipment. Products seek to eliminate any and all dead space, allow for continuous process flow, and are self-cleaning thanks to continuous flow design. Some high pressure seals come equipped with anti-clogging features, accomplished by the elimination of internal cavities while protecting gauges. Multi-purpose seals reduce temperature influence and improve instrument performance while pinpointing and diffusing areas of high stress. These pre-emptive measures result
in longer instrument life-cycles and improved performance while ensuring protection from corrosion.

There are numerous options and available diaphragm seal variants. Share your application specifics with a product specialist, combining your own process knowledge and experience with their product application expertise to develop an effective solution.

Measurement and Control Instruments for the Power Industry

Coal fired power plant.

The coal-fired power generation and combined-cycle power generation industry now demands much more of its control and instrumentation suppliers. Common areas for use are fuel systems, fermenters, gas storage, water treatment, boiler feed water, boiler drum, steam line, cooling water system, generator, condenser, gas cleaning system, flue gas desulfurization, residuals storage and stack.

The document below provides a visual guide of common applications and the instrumentation products that have proven track records in those applications.

Foxboro Instrumentation for Power Plants from Swanson Flo

Flowserve Valtek Valve Automation

The video below highlights several Swanson Flo automated Valtek control valves. Included in these systems are Valtek ShearStream segmented ball valves, Valtek Valdisk BX butterfly valves, Logix positioners, Valtek VR piston actuators, and StoneL Axiom valve monitors.

Swanson Flo is a premier valve and valve automation supplier located in Plymouth, MN with warehouse and fabrication facilities in Addison, IL, Indianapolis, IN and Menomonee Falls, WI.

Visit Swanson Flo at http://www.swansonflo.com or call 800-288-7926 with any valve automation project.

Swanson Flo Valve Automation Services

42 inch electrically (Limitorque) actuated butterfly valve.

Swanson Flo, an industrial valve and control company headquartered in Plymouth, Minnesota is also one of North America's leading valve automation specialists.

From simple, small pneumatic or electrically actuated valves, to very large, critical-control valve systems, Swanson Flo delivers tested, certified, and reliable product to customers located in the Upper Mid-West. Swanson Flo designs, engineers, and assembles actuated valve assemblies for the best fit, highest performance, and optimal application life. Their engineers and technicians combine decades of experience and knowledge. Coupled with a broad variety of carefully selected, readily available components, Swanson Flo customers are provided the best quality and best value possible.

Building upon 50+ years of industry and applications experience, Swanson Flo boasts the largest, most comprehensive automation facility in the mid-west, with capabilities for electric, pneumatic and electro-hydraulic actuation. A team of experienced design engineers and fabrication technicians construct automated valve systems from virtually any valve, actuator, monitor or positioner technology.

For more information, visit http://www.swansonflo.com or call 800-288-7926.

Swanson Flo Performance Brochure

Swanson Flo specialize in valves, automation and instrumentation.  Swanson Flo Performance sets the standard for process control optimization and training that maximizes plant uptime, safety and operating efficiency.

Swanson Flo Performance from Swanson Flo

Understanding Motor Operated Valves (MOV) in Industry

The video below demonstrates the operation a small (Worcester) motor operated ball valve (MOV). Also known as an “electric actuator”, motor operators come in a wide variety of sizes and styles. Some electric actuators are intended for quarter-turn valves (such as ball and butterfly valves), while others are designed to operate linear valves (such as gate and globe valves).

The MOV / electric actuator consists of an electric motor with the gearbox assembly which rotates the shaft of the valve. Most MOVs operate at 120, 240 or 480 volt, single or three phase. Basic features include adjustable limit switches to limit valve travel and to notify valve status, directional settings, analog inputs to allow for precise control, analog outputs to provide a feedback signal and digital communications. MOV enclosures can be either NEMA 4, NEMA 4X and NEMA 7 and are available in a wide range of torque outputs to match the valve it is operating.

Understanding Control Valves: The Flowserve Valtek Mark One

Control valves are an integral part of many process control loops. Understanding their basic operation is important for any process control professional. The following video demonstrates the reassembly of the Flowserve Valtek Mark One control valve and introduces the viewer to a control valve's main components.

There are a variety of styles of control valves. A globe control valve is a specific type of valve used for regulating flow in a pipe. The design includes a movable plug, connected to a stem, which can be moved linearly to close or open the valve. Globe control valves are referred to as “linear” valves because of this movement to open and close is directed by a piston type, linear movement actuator. Generally, globe control valves provide better overall flow control than quarter-turn valves due to the design of their flow path.

For more information, a Valtek Mark One specification sheet is also included with this post.

Flowserve Valtek Mark One Control Valve from Swanson Flo

Virtual Tour of Swanson Flo Illinois

Swanson Flo has facilities and teams of skilled experts who are uniquely equipped to rapidly combine resources and skills for the maximum benefit of their customers. As the company continues to grow, their investment in new technologies, equipment, facilities, and solutions demonstrate their commitment to build solid client partnerships.

The video below provides a virtual tour of our new Addison, Illinois warehouse, instrument calibration lab, and valve automation center.

For more information, visit Swanson Flo at http://www.swansonflo.com or call 800-288-7926.

Rupture Discs Are Designed to Fail. That's Their Job.

Rupture disc and holder
(courtesy of Continental Disc)

A rupture disc (pressure safety disc, burst disc, bursting disc) is a “one and done” pressure relief device most often used to protect a vessel, pipe, or container from over pressurization. As opposed to pressure relief valves, rupture discs are designed to function only one time by providing an instantaneous response to an over-pressure condition.

These sacrificial parts are designed to burst when pressure within production equipment exceeds a certain threshold by breaking down, stopping the process to prevent or mitigate hazardous events. Rupture discs are critical instruments utilized so that companies can ensure process safety as set forth by the International Safety Standards (IEC 61508/61511).

Rupture discs prove most effective when they fail according to pre-established specifications. Inferior rupture discs often cause unnecessary and expensive production shutdowns due to the lack of quality testing and expertise in manufacturing.

Rupture discs are commonly used in chemical, petrochemical, nuclear, aerospace, medical, railroad, pharmaceutical, food processing and gas & oil applications. They provide primary or backup protection. Very often rupture discs are used in tandem with safety relief valves, protecting them from the process media and extending the life of the relief valve.

For more on rupture disc's call Swanson Flo at 800-288-7926 or visit http://www.swansonflo.com.

Continental Disc HPX Rupture Disc Family from Swanson Flo