Showing posts with label Eastern Pennsylvania. Show all posts
Showing posts with label Eastern Pennsylvania. Show all posts

Magnetrol Model A15 Single-Stage Displacer Level Control Switches


Displacer switch operation is based upon simple buoyancy, whereby a spring is loaded with weighted displacers, which are heavier than the liquid. Immersion of the displacers in the liquid results in buoyancy force change, changing the net force acting on the spring. The spring compresses as the buoyancy force increases.

A magnetic sleeve is connected to the spring and operates within a non-magnetic barrier tube. Spring movement causes the magnetic sleeve to move into the field of a pivoted magnet, actuating a switch mechanism located outside the barrier tube. Built-in limit stops prevent over stroking of the spring, under level surge conditions.

The minimum differential band is approximately 6 inches (152 mm) in water and varies somewhat with liquid specific gravity. The maximum differential is determined by the length of the displacer suspension cable. Series A15 units are calibrated to operate over a narrow level differential band and are ideally suited for liquid level alarm applications on either high or low level.

For more information about Magnetrol Displacer Level Switches, contact Miller Energy, Inc. Call them at 800-631-5454 or visit their web site at https://millerenergy.com.

Process Instrumentation and Valves for the Chemical and Petrochemical Industries


Miller Energy provides process control instruments and valves designed to assist in higher quality yields, more efficient processes, and greater plant safety for chemical processing and petrochemical refining manufacturing facilities. 


The Chemical Industry


The chemical industry is key to industrial production. It transforms the raw materials of animals, vegetables and minerals into a host of products used by both the industrial and domestic customers. Lightweight and durable plastic products contribute to fuel effectiveness in transportation, energy-saving insulation material in buildings, paints and protective coatings that extend metal and wood life, soap, shampoo and detergents maintain us clean, pharmaceuticals and disinfectants protect our health. Without vital chemicals, computers and telecommunications systems could not work.

The industry has matured using local resources such as salt, coal, lime, vegetable products and animal fats. It is now a worldwide sector that mainly uses natural gas and oil fractions such as naphtha as the main raw materials. There is a strong awareness of the need to substitute fossil resources both as raw materials and for process energy with sustainable options.

The Petrochemical Manufacturing Industry


The sector produces petrochemicals which are petroleum and natural gas chemicals (organic compounds not burned as fuel). Ethylene, propylene, butylene, benzene, toluene, styrene, xylene, ethyl benzene and cumene are key products. These products are fundamental construction blocks in the manufacturing of consumer products, automotive parts and numerous sustainable and unsustainable goods. These products are fundamental construction blocks in the manufacturing of consumer products, automotive parts and numerous durable goods. This sector does not include organic compounds such as ethyl alcohol and inorganic chemicals such as carbon black.

Olefins and aromatics constitute the building blocks of a large variety of products, including solvents, detergents and adhesives. Polymers and oligomers used in plastics, resins, fibers, elastomers, lubricants and gels are built upon olefins.

Miler Energy: Chemical and Petrochemical Instrumentation and Valve Experts


Miller Energy offers a broad range of instrumentation and valves for these diverse markets. Since 1958, Miller Energy, Inc. has exceeded customers expectations in the Chemical and Petrochemical Industries by specifying and providing the highest quality instrumentation and valves. Known for unparalleled customer service and local technical support, Miller's comprehensive line of pressure, temperature, level, flow and analytical products are available now and ready to solve your most challenging chemical and petrochemical applications.

Contact the Miller Energy office in your area by visiting this web page, or call 800-631-5454 for further assistance.

The Design Principle of Segment Disc Control Valves


Figure 1.
The central throttle device of this control valve is two discs with segmented openings which slide on one another and seal against each other (Fig. 1). The segment discs are positioned vertically in the valve housing, facing the direction of flow. A moving disc is placed upon a rotationally fixed segment disc, the geometry of which determines the throughput capacity and characteristic curve. These two discs have the same number of segments and the moving disc is rotated via a push rod which is tangentially inserted. Consequently, the cross-section surface of the free segment passage changes when a control intervention is made.

Irrespective of the pending pressure differential, the moving segment disc is pressed onto the fixed disc via a spring pack- age. This ensures that the direction of flow is variable and that the valve can be installed in any desired location. Due to the fact that there are no metal seats with ring-shaped contact surfaces, no grooves will occur which can rapidly lead to leaks in traditional steam valves. Leakage ratios amounting to < 0.001% of the Kvs value are constantly achieved with the significantly less vulnerable surface seal.

Extremely robust segment disc valve from
Schubert & Salzer for steam distribution.
Thanks to this special design, segment disc valves are one of the few valves that are able to combine control precision and a high level of tightness, even in extreme conditions and which also experience hardly any wear.

The standard segment disc valves are available in finely graduated intervals of between DN 25 and DN 300 – and go up to DN 800 where necessary – in an intermediate flange design for nominal pressures up to PN 25. They can be used for media temperatures ranging between -60°C and +220°C (higher temperatures and nominal pressures are available on request). The robust valves have a rangeability of 60:1.

For more information, contact Miller Energy, Inc. by calling 800-631-5454, or visit their web site at https://millerenergy.com.

How to Change Loss of Signal Failure Mode on the Cashco Ranger Control Valve


This video provides step-by-step instructions on how to change the Cashco Ranger (control valve) loss of signal failure mode from air to open / fail closed to air to close/ fail open, as well as remounting and recalibrating the valve positioner.

The Cashco Ranger is one of the most popular control valves on the market. It is the most versatile, adaptable, and easily maintainable valve ever produced.

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.

For more information about Cashco in Metro New York, New Jersey, and Eastern Pennsylvania contact:

Miller Energy, Inc.
New York Metro and Northern NJ: 800-631-5454
Eastern PA, Southern NJ, Delaware: 888-631-5454
https://www.millerenergy.com

Selecting the Right Magnetic Level Indicator

Companies in the process industry need the ability to visually monitor liquid levels in vessels (boilers, storage tanks, separators, etc.). Traditionally, armored glass sight gauges have been used. However, many companies want an alternative to sight gauges to avoid problems such as breakage, leaks, or bursting at high pressures and temperatures. In addition, the visibility of the sight glass can be poor and often affected by moisture, corrosion, or oxidation.

Many companies are increasing the use of automation and desire a 4–20 mA, HART®, FOUNDATION® fieldbus, or other output for level—which is difficult to do with a sight glass. Magnetic level indicators (MLIs) do not have the shortcomings of glass sight gauges and are suitable for a wide variety of applications.

Orion Instruments, a Magnetrol company, has authored an excellent Magnetic Level Indicator selection guide.


Miller Energy, Inc.
https://millerenergy.com
In NY/NJ 800-631-5454
In Eastern PA 888-631-5454

Level Instruments for Tank Overfill Protection

Tank overfill incidents in recent years have resulted in loss of life and billions of dollars in damages to petroleum facilities worldwide. One of the worst incidents - the overflow of a gasoline storage tank at Buncefield Oil Depot (U.K.) - has been traced to the failure of level control to maintain containment of the flammable liquid. More common are minor spills that cause significant environmental impact and result in millions of dollars in clean-up fees and environmental agency fines.

In the wake of this incident, the American Petroleum Institute’s (API) Recommended Practice (RP) 2350, the most widely accepted guideline for overfill protection of petroleum storage tanks, has been revised. The fourth edition was published in May 2012 and combined the prescriptive standards of RP 2350 with the functional safety standards of Safety Instrumented Systems (SIS) as described in IEC 61511.

Vital to these new requirements is the application of level instrumentation as one part of a comprehensive Overfill Prevention Process (OPP).

Magnetrol, a world-leader in the design, manufacturer and application of level and flow instrumentation, has written an application document titled "Level Instruments for Tank Overfill Protection". Get your copy here.

Brooks Instrument Sponsoring $2000 Engineering Scholarship

CLICK THIS LINK TO LEARN MORE

Brooks Instrument is committed to the next generation of engineers. Accordingly, they have established a $2,000 scholarship for a qualified student enrolled in an engineering program at an accredited college or university. Learn more here (https://www.brooksinstrument.com/en/about-us/scholarship).

Detailed Look at the Yokogawa YS100 Series as a Replacement for the Obsolete Siemens 353

This video is a thorough presentation detailing why and how the Yokogawa YS1000 Series is the best replacement for the obsolete Siemens/Moore 353 controller. It is composed of a series of presentation slides - hit the pause button to focus on any single slide.

New Jersey: 908-755-6700 
Pennsylvania: 610-363-6200

How to Select a Pressure Switch

UEC One Series Switch Transmitter Hybrid
UEC One Series Switch Transmitter Hybrid
Reprinted with permission from United Electric Controls

Pressure switches are widely used by many industries and within many applications. The basic function of a pressure switch is to detect a pressure change and convert it into an electrical signal function – typically on/off or off/on. Pressure switches may be of electro-mechanical or electronic/solid-state design (see our ONE Series); and while each may have its advantages, arriving at the correct pressure switch for your application is the same.

Set Point & Deadband


Application set point (sp) is the desired value reached at rising or falling pressure at which the micro-switch changes electrical states. Depending upon the pressure switch function, the micro-switch could be wired to open (turn something OFF)  or close (turn something ON) when set point is achieved, thereby triggering an event such as an alarm, equipment shutdown, or powering up secondary equipment. Ideally, the set point should fall into the mid 50% of the pressure switch range for best performance including repeatability and long life. On an electro-mechanical pressure switch, set point may be adjusted internally or externally either through blind adjustment or reference dial. An electronic pressure switch would have internal or external adjustment via a key pad and digital display or a handheld programmer.
Deadband graph

Deadband (DB) is the on-off differential required to reset the micro-switch. This value may be fixed or adjustable with an electro-mechanical switch and may be up to 100% adjustable on an electronic switch.

Deadband may be an important factor to consider depending upon the application requirements.

System Pressure


Knowing your normal and maximum system pressures will help in selecting a pressure switch with appropriate minimum and maximum operating parameters. Once your set point is established, other factors to consider are vacuum and/or surge pressure that could affect switch operation. This would involve maximum working pressure, over range pressure, and proof pressure specifications of a pressure switch. The relationship between set point and system pressure has a direct effect on switch performance and life.

Electrical Considerations


UEC 100 Series Pressure Switch
UEC 100 Series Pressure Switch
Micro-switches are available in a variety of configurations. The most common for electro-mechanical pressure switches is 15A, 480VAC SPDT (single pole, double throw). The advantage of a SPDT micro-switch is that it offers wiring flexibility to either open or close on pressure change. Other micro-switches available include 1A with gold contacts, useful when working with a PLC, or at the upper end, 30A when switching certain high voltage heaters or motors. Adjustable micro-switches help with deadband adjustment. A DPDT (double pole, double throw) micro-switch would provide two simultaneous functions off of one micro-switch. If a low-high limit alarm and shutdown were required, there are pressure switches that include two SPDT micro-switches that are independently settable.

An electronic pressure switch would use solid-state relays to change states. Like an electro-mechanical switch, the electronic switch can be programmed to open or close on rising or falling pressure. There are different capacities for switching voltage and current depending upon the application requirements.

Process Media and Wetted Parts


The pressure connection and sensor are known as wetted parts since they come into direct contact with the process media. Sensor material is either elastomer (i.e. Buna-N, Teflon®) or metallic (i.e. Brass, Stainless Steel) with metallic or composite pressure connections. The process media must be compatible with the wetted parts material. Process media temperature should also be considered as each of the different wetted materials would have differing operating properties.

Pressure Switch Mounting


If the unit is to be installed directly onto the process, there are many methods of installation.
Typically a 1/8”, 1/4”, or 1/2” NPT (national pipe thread taper) connection is used with a mating
fitting to secure the pressure switch to the process. There are also straight threaded (SAE, BSPT)
connections, flush mount connections, and sanitary connections. The pressure switch may be
mounted directly in the process line using the threaded connection, a manifold, or flange; or the
enclosure could be bolted to a mounting plate or other plane to secure it. If heavy vibration is
present, you may choose to use a remote diaphragm seal with the pressure switch. The diaphragm
seal mates with the process connection while the pressure switch enclosure is mounted securely
away from the vibration. 

Process Environment


It is important to know what type of environment the pressure switch would be installed in – hazardous or ordinary location; indoors or outdoors; exposed to salt air; inside a control panel; in high ambient temperature. These are just some of the factors to consider so the right enclosure type is chosen. Enclosure types come in many shapes, sizes, and materials. They also conform to various industry and third-party approval standards. Electronic switches can be used to replace electro-mechanical switches when SIL is needed for safety applications.  There are also electro-mechanical pressure switches without enclosures; typically used in OEM, non-hazardous locations where the environment is benign.

With careful consideration of all the factors listed above, choosing a pressure switch is a snap. If you are at all unsure, please contact your local United Electric Distributor or visit the UE Product Selector to find your pressure switch.

Miller Energy, Inc. - Expertly Serving These Industries in the Mid-Atlantic Region

Miller Energy is a Manufacturer's Representative and Distributor of Industrial Instrumentation and Process Control Equipment with offices in South Plainfield, NJ and Exton, PA. In business since Since 1958, Miller's success is attributable to their commitment to exceeding their customers expectations and a comprehensive line of "best-of-breed" measurement, control, and communication products. With a strong reputation for unparalleled customer service and expert local technical support,  Miller Energy continues to demonstrate strong growth in the Mid-Atlantic region.


https://millerenergy.com
908-755-6700 NJ
610-363-6200 PA

Radiometric, Non-contact Level Measurement for Liquids or Solids

Radiometric level detection
Radiometric level detection
(RONAN)
Radiometric level measurement, using a very low gamma level source, is designed to deliver outstanding performance in a wide range of difficult applications and process conditions for both liquids and bulk solids which include the most dangerous materials such as caustic, toxic, corrosive, explosive, and carcinogenic irrespective of their viscosity and temperature.

These level gauges meet “As-Low-As-Reasonably-Achievable” (ALARA) guidelines. Source activity is customized depending on vessel and process parameters such as diameter, wall thickness, material, and measurement span to ensure optimum sensitivity, economy and safety while keeping the source activity to a minimum.

Non-contact level
Sources and Detector Mounted
External to Vessel
An exclusive “Radiation Low Level” (RLL) source holder uses up to 100 times less gamma energy than comparable gauges, and is the only source holder recognized by the NRC to be so safe that it does not require the stringent documentation, training or handling procedures of other systems.

Operation

Radiometric level measurement provides a safe and efficient, non-contact method to measure liquids or solids in harsh process environments. Each system consists of a gamma source, detector and microprocessor.

  • The gamma source, typically mounted external to the vessel emits energy through the vessel walls collimated in a direction towards the detector mounted on the opposite side of the vessel. The gamma energy reaches the detector when the vessel is empty. As the process level rises in the vessel, the gamma energy reaching the detector will decrease in an inversely proportional relationship to the level. 
  • The detector measures the level of energy and sends a proportional signal to the microprocessor. 
  • The microprocessor linearizes, filters, and correlates this signal to a level measurement. 

The entire system is mounted external to the vessel and can be easily installed and maintained while the process is running ... without expensive down time, vessel modifications or chance of accidental release.

Applications
Low Level Source and Detector
Low Level Source and Detector
Mounted External to Vessel
  • Radiometric level detection
  • Low Level Source and Detector
  • Mounted External to Vessel
  • Solids or Liquid Measurement 
  • Measurement Not Affected by: 
  • Internal Obstructions. i.e. Agitators Extreme Process Temperatures 
  • Caustic Processes 
  • Violent Product Flow 
  • Sterile Process 
  • Changing Process 
  • Variable Product Flow 
  • Automatic Compensation for Vapor Density Changes 
  • Automatic Compensation for Foam or Gasses 
  • Automatic Compensation for Process Build-Up 
  • Detectors Contoured to the Shape of Vessels 
  • Upgrade Utilizing Existing Sources
Features and Benefits 
  • Accurately Measures the Most Complex Processes 
  • Solid Crystal or Flexible Scintillating Fill- Fluid 
  • Excellent Measurement Reliability due to Proprietary Filtering Technology 
  • Level Detection of Multiple Interfaces 
  • Low Maintenance / No Component Wear 
  • Auto-Calibration

For more information in Eastern Pennsylvania, New Jersey, Metro New York or Delaware contact:
Miller Energy by visiting https://millerenergy.com or by calling 908-755-6700 in New Jersey, or 610-363-6200 in Pennsylvania.

Industrial Refractometers Used in Process Control

Refractometer Pharmaceutical Use
Refractometer for pharmaceutical use (K-Patents).
Part physics, part material science and part chemistry, refractometry is the process which measures the composition of known substances by means of calculating their respective refractive indexes (RI). RIs are evaluated via a refractometer, a device which measures the curve, or refraction, resulting when the wavelength of light moves from the air into and through a tested substance. The unitless number given by the refractometer, usually between 1.3000 and 1.7000, is the RI. The composition of substances is then determined when the RI is compared to a standard curve specific to the material of the substance.

Process refractometers provide the analysis to quickly, reliably, and very accurately identify a sample and determine it's concentration and purity levels. They measure the refractive index and temperature of flowing liquids, and apply mathematical functions to determine the concentration of dissolved solids.

Common industrial refractometer applications are:
  • Calculating beverages’ amount of sugar dissolved is water.
  • In commercial food applications such as juice production or tomato processing, refractometers are used to measure degrees Brix (Tthe Brix scale relates refractive index to sugar concentration, and is a key way to maintain consistency).
  • In the pharmaceutical industry, process refractometers are used to monitor and control concentration levels during supersaturation, a critical process in crystallization.
  • In pulp and paper production, process refractometers for measuring dissolved solids in black and green liquor during the chemical recovery process.
Equipment manufacturers have developed numerous refractometer configurations tailored to specific each use and application. Each has a set of features making it the advantageous choice for its intended application. Product specialists can be invaluable sources of information and assistance to potential refractometer users seeking to match the best equipment to their application or process.

For more information on industrial refractometers, contact Miller Energy by visiting https://millerenergy.com or by calling 908-755-6700 in New Jersey or 610-363-6200 in Pennsylvania.

Laboratory Flame Testing of Industrial Pressure Gauges: Wika vs. Competitor

Laboratory flame testing of industrial pressure gauges. Manufacturer Wika versus a competitor. The test is structured in (3) stages: a 10 second burn, a 30 second burn, and then a one minute burn. The Wika gauge maintains its reading, does not melt, and does not continue to burn.

https://millerenergy.com
New Jersey 908-755-6700
Pennsylvania 610-363-6200

Flow & Pressure Instrumentation for Biopharmaceuticals & Life Sciences

Flow & Pressure Instrumentation for Biopharmaceuticals & Life SciencesProducing biopharmaceuticals is one of the world’s most demanding manufacturing processes.

Brooks Instrument’s mass flow and pressure control technology helps maximize cell culture yields and control bioprocess costs. Their flow
and pressure controllers set global standards for reliability, repeatability and long-term stability.

Brooks Instrument mass flow controllers (MFCs) satisfy key biotechnology research and production requirements:
  • Tight control of DO and pH during experiments and production
  • NO unplanned downtime due to high cost of losing a batch or experiment
  • Ability to rapidly diagnose and resolve issues with bioreactors or fermentation equipment
  • Cost-effective method for adhering to regulatory requirements
  • Excellent technical support and rapid response for equipment service


What Advantages Do Displacer Transmitters Have Over Differential Pressure Level Transmitters?

Displacer Transmitters
Displacer
Transmitter
(Magnetrol)
Many technologies have been available over the years have helped the process control industry with level measurement. From basic mechanical float-operated level switches, the process automation industry has been developing new technologies to make industry safer and more efficient.

An example of a "tried and true" technology that was commonly used in the process automation industry is the DP (differential pressure) level transmitter. First introduced in the 1950s, DP transmitters measures the hydrostatic (head) pressure of a liquid in a tank or vessel and interprets this as level, based on the density/specific gravity of the liquid and programmed in by the user. A newer, alternative technology to DP transmitters is the displacer level transmitter, a device also based on specific gravity. While they both are dependent on specific gravity, they are significantly different in areas of installation, accuracy, and maintenance requirement.

Application/Calibration

Applying a DP transmitter or displacer level transmitter requires experience and there are many factors to be considered. Here are a few:

DP transmitters use inferential measurement to determine level measurement from the hydrostatic pressure.  Despite requiring the specific gravity variable having to be programmed into the transmitter electronics, the level displacer transmitter is in contact with the process media and the level measurement is direct.

DP transmitters requires time consuming and expensive calibration/re-calibration if any of the set-up parameters change or if the same DP transmitter is used on different materials in the same tank.
Displacer transmitters only require two variables to be programmed (temperature and specific gravity), making it easier when running multiple products in the same tank.

Many displacer transmitters do not require liquid to be present for calibration. They are programmed (wet or dry) using software. A huge time and money saving over DP transmitters.

Mounting

The physical mounting of DP transmitters is limited, which can in some situations can become downright problematic. DP transmitters require (2) side-mounted entry locations on the vessel or tank, with one having to be near the bottom. As a general rule, the fewer the entry points of a tank or vessel, the better, because of leakage. Tank bottom entries all the more so.

Displacer transmitters are mounted to meet the requirements of the application and do not require a connection at the bottom of the tank.

Installation Cost

While DP transmitters have a lower unit cost, adding ancillary components such as tubing and heat tracing can quickly "level" the installation cost playing field. Furthermore, don't discount the time cost savings when setting up, calibrating and re-calibrating displacer transmitters.

Temperature Range

DP transmitters have a normal operating temperature of up to 250°F, with an upper limit of 650°F when special options are specified.

Displacer transmitter can be used up to 850°F, very helpful particularly with level measurement in a hot oil separator application.

There are many options and variants to accommodate industrial level applications. Share your level application challenges with instrumentation specialists, leveraging your own knowledge and experience with their product application expertise to develop the most effective solution.

Cashco / Valve Concepts Model 3100 Packing Material Removal and Weight Installation Instructions

Valve Concepts Model 3100
Valve Concepts Model 3100
The Model 3100 end-of-line conservation breather vent is part of the Valve Concepts, Inc. modular vent product line. The Model 3100 can easily be field converted to a vacuum only vent, a pressure/vacuum vent with pipe away and can either be direct acting or pilot operated.

The Model 3100 end-of-line conservation breather vent is designed for use on atmospheric and low-pressure storage tanks where pressure and vacuum relief is required.

How it Works

Weight loaded pallets in the vent housing allow the intake of air and the escape of vapors as the tank breathes due to thermal changes and product movement in and out of the tank. The pallets open and close to permit in breathing and out breathing necessary to maintain the tank pressure within permissible limits to avoid damage to the tank.

Paperless + Wireless Process Control Recorder

Paperless and Wireless Process Control Recorder
Paperless and Wireless
Yokogawa GX20W
There are probably few among us who long for the days when process recorders used paper. Video based graphic (also known as paperless) recorders, aside from being paperless, provide a broad range of functionality that empowers a user to display and deliver process information in whatever way is most useful for the application.

High sampling speed of multiple inputs that can be configured to accommodate a range of input signals, along with data storage, network communications and programmable alarm outputs power up the usefulness of these instruments for monitoring and documenting process operation. Many utilize touch sensitive screens, eliminating any buttons or keys on the operator panel.

Some of the great features available on today's paperless recorders:

  • Multiple channels of input
  • Start/stop recording by batch, and create data files
  • Ample internal memory
  • Creation of template-based Excel spreadsheets
  • Custom display function
  • Historical data with date and time calendar search function
  • Ethernet interface
  • PROFIBUS-DP and EtherNet/IP protocols
  • Dust and splash-proof front panel
  • Front panel door lock and login function

Wireless Seals the Deal

Wireless technology is a serious contributor in the effort to improve plant efficiency, lower risk, and increase productivity. Wireless recorders are now available for monitoring virtual all process variables such as pressure, temperature, level, and flow (plus many more).  The use of wireless recorders provides a compelling argument when you consider installation cost savings and convenience.  Savings estimates as high as 70% are realized when compared to the cost using cables for the same application.

There are many options and variants to accommodate every conceivable process control application. Share your data acquisition and process monitoring challenges with instrumentation specialists, leveraging your own knowledge and experience with their product application expertise to develop an effective solution.

For more information on paperless recorders, contact Miller Energy by visiting https://millerenergy.com or calling 908-755-6700 in NJ or 610-363-6200 in PA.

Pressure Switches - The Stalwart of Pressure Instrumentation

pressure switch
Pressure switch in an
explosion-proof housing.
(United Electric)
A pressure switch is an electromechanical device that detects the presence of fluid pressure and responds by opening or closing an electrical or pneumatic circuit.

In heavy industry, pressure switches are used in virtually every power plant, refinery, chemical plant, paper mill, steel mill, or other manufacturing plant that blends ingredients.

Pressure switches are simple devices. They can be broken down to their major parts: a pressure port or connection; a sensor that moves in relationship to changing pressures; an electrical or pneumatic switch that opens or closes upon movement; and finally a housing that protect the internals of the pressure switch from the ambient conditions.

pressure switch
Differential pressure switch.
(United Electric)
Pressure switches use a variety of sensing elements such as diaphragms, bellows, bourdon tubes, or pistons. In most cases, the movement of these sensors, caused by pressure fluctuation, is transferred to a set of electrical contacts to open or close a circuit. Normal status of a switch is the resting state. A pressure switch will be in its “normal” status when it senses low or minimum pressure. For a pressure switch, “normal” status is any fluid pressure below the trip threshold of the switch.

One of the earliest and most common designs of pressure switch was the bourdon tube pressure sensor accompanied by a mercury switch. A mercury switch is a position sensitive glass bulb containing mercury that flows over, or away from, the electrical contacts. When pressure is applied, the bourdon tube attempts to straighten, and moves enough to slightly tilt the mercury switch. Many of these kind of pressure switches were sold on steam boilers, and while they became a de facto standard, they were sensitive to vibration and breakage of the mercury bulb.

electrical switch contacts
NO vs. NC electrical switch contacts.
The most common electrical switch used in pressure switches are "microswitch" type. These are also called "snap switches" because they are actuated by very little physical force, through the use of a tipping-point mechanism. These type of switches offer reliability and repeatability. They also are available in many different voltages and current ratings

One of the criteria of any pressure switch is the deadband or (reset pressure differential). This setting determines the amount of pressure change required to reset the switch to its normal state after it has tripped.  The “differential” pressure of a pressure switch should not to be confused with differential pressure switch, which actually measures the difference in pressure between two separate pressure ports.

When selecting pressure switches you must consider the electrical requirements (volts, amps, AC or DC), the area classification (hazardous, non-hazardous, general purpose, water-tight), pressure sensing range, body materials that will be exposed to ambient contaminants, and wetted materials (parts that are exposed to the process media).

It's always a good idea to discuss your application with an expert before specifying or installing a pressure switch. You'll end up saving time and money, and ensure long, safe operation.

For more information on pressure switches, contact Miller Energy by visiting https://millerenergy.com or by calling one of these numbers: In New Jersey 908-755-6700. In Pennsylvania 610-363-6200.

Miller Energy - Industrial Instrumentation & Process Control Equipment

Miller Energy is a Manufacturer's Representative and Distributor of Industrial Instrumentation and Process Control Equipment. Since 1958, we have been committed to exceeding our customers expectations by providing an unparalleled level of customer service and local technical support. We offer the most comprehensive line of measurement, control, and communication solutions in the Industry today. The products we represent solve challenging applications in the Industrial Gas, Power, Refining, Chemical / Petro-Chemical, Food & Beverage, Water/Wastewater, and Pharmaceutical markets.

NJ 908-755-6700 
PA 610-363-6200