The Swanson Flo Blog is dedicated to provide educational and new product information on process control instrumentation, control valves, and valve automation. For more information on these products, visit SwansonFlo.com or call 800-288-7926.
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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.
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
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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.
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.
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.
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.
