New Product Alert: The United Electric Controls Excela™ Electronic Switch

United Electric's Excela™ is the first switch of its type. Excela™ provides plant operators with an affordable way to upgrade to electronic performance. It has only two wires and is simple to place into the existing mechanical switch infrastructure. This unique, high-quality electronic pressure and temperature switch provide everything operators require for improved performance at an affordable price.

There are benefits and drawbacks to using advanced transmitters and old electromechanical switches at a facility. In terms of maintenance, an operator may spend at least ten times trying to maintain a switch over a transmitter. A transmitter, on the other hand, can be expensive and excessive for a modest application. There is a market void for economical, easy-to-install, drop-in-upgrade instrumentation for a facility's old mechanical switch infrastructure. To address the maintenance and upgrade cost concerns, the Excela™ was designed from the ground up to combine the benefits of the electromechanical switch (e.g., simplicity) and the transmitter (e.g., precision) at an inexpensive price point.

The Excela™ electronic switch is for plant upgrades by replacing mechanical switches with cutting-edge digital switch technology. It makes use of the existing mechanical switch wire as well as the attached discrete input power supply. In most cases, Excela™ is a direct drop-in replacement for existing mechanical pressure, differential pressure, and temperature instrumentation, making upgrading instrumentation within a plant cost-effective and straightforward. Typical uses are monitoring pressure and temperature for alarm and emergency shutdown in lubricating oil, boiler, furnace feed pumps, cooling, chiller water injection pumps, compressors, and many others.

For more information about the Excela™ electronic switch contact Miller Energy. Call 800-631-5454 or visit https://millerenergy.com.

Programming the UE One Series Hybrid Transmitter-Switches

The United Electric Controls One Series electronic pressure and temperature transmitter-switches are designed to provide transmitter, switch and gauge functions all-in-one rugged enclosure that can withstand the rigors of harsh and hazardous environments. Available in Type 4X enclosures approved for intrinsic safety, flameproof and non-incendive area classifications, these hybrid transmitter-switches have a fully adjustable set point and deadband and 0.1% repeatability. This video provides a quick tutorial on how to set up the One Series.

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

Simplified Operation and Reduced Cost With Safety Transmitters and Switches

Process safety experts continually seek sustainable ways to improve the performance of safety critical loops, achieving risk reduction and safety goals in a cost-effective manner. Some view a reduction in complexity of safety related protocols to be a positive development. Traditional or historical approaches to deploying full blown safety systems were generally associated with great expense and high complexity, and still came up short on delivering the needed levels of risk reduction. Process control device and equipment manufacturers have responded with newer technologies and products that better address the safety needs of industrial processing.

In sensor subsystems, United Electric’s certified safety transmitter for pressure or temperature provides a less costly, simple path for process designers, instrument and control engineers, and maintenance personnel. The Series One Safety Transmitters combine several useful safety and monitoring functions into a single, easy to deploy device. Products are available for gauge pressure, differential pressure, and temperature applications. In addition to a 4-20 mA process variable output, the Series One has an embedded programmable high-capacity relay certified as a safety variable output. The Series One Safety Transmitter provides designers the option of a hard wired trip in less than 100 milliseconds, with a tenth of a percent repeatability, along with the monitoring functions of a traditional continuous analog output.

For equipment under control requiring protection, or processes where rapid excursions can initiate dangerous events, this unique pressure and temperature transmitter is addressing process safety time constraints, coupling issues with PLC and DCS units, and adding diversity to the safety instrumented function.

There is a whole lot more to learn about these "Safety right out of the box" industrial pressure and temperature safety transmitters. A product data sheet is provided below, but you can get the latest and most detailed product and application information from a specialist in industrial process measurement and control. Share your safety instrumentation challenges with them, combining your process expertise with their product application knowledge to develop effective solutions.

Learn more about the UEC One Series by visiting this page on the Miller Energy web site.

One Series Safety Transmitter - Pressure and Temperature Transmitter-Switch from Miller Energy, Inc.

Temperature Switches

Temperature switch
(United Electric Controls)

A temperature switch detects the temperature of some substance. Temperature switches often use bimetallic strips as the temperature-sensing element, the motion of which actuates one or more switch contacts. An alternative design uses a metal bulb filled with a fluid that expands with temperature, causing the switch mechanism to actuate based on the pressure this fluid exerts against a diaphragm or bellows. This latter temperature switch design is really a pressure switch, whose pressure is a direct function of process temperature by virtue of the physics of the entrapped fluid inside the sensing bulb.

The “normal” status of a switch is the resting condition of no stimulation. A temperature switch will be in its “normal” status when it senses minimum temperature (i.e. cold, in some cases a condition colder than ambient). For a temperature switch, “normal” status is any sensed temperature below the trip threshold of the switch.

Like all other process switches, temperature switches exhibit a certain amount of deadband in their switching action. A temperature switch that trips at 300 F rising, for example, will not reset at 300 F falling. That switch would more likely reset at some lower temperature such as 295 F. With mechanical switch designs, some amount of deadband is inevitable due to friction inside the mechanism. However, process switch deadband is actually a useful characteristic as it helps avoid repeated “nuisance” alarms from happening.

To understand this concept, it is helpful to imagine a scenario where the process variable is at or very near the trip point. For our hypothetical temperature switch with a trip point of 300 F (rising), imagine a situation where the process temperature is precisely 300.0 F. Any further rise in temperature will of course trip the switch (sounding an alarm). With no deadband, however, the switch will immediately re-set when the temperature falls back down to 300.0 F. This means the switch may possibly “cycle” back and forth between its trip and reset states with just a minute change in process temperature (300.0 F to 300.1 F and back again). If the temperature switch is activating an alarm every time it trips, it will create a series of alarm events prompting operators to repeatedly acknowledge the alarm. This is a nuisance to operations personnel, as it distracts them from addressing what they already realize is a process problem. It is better for the switch to trip at 300.0 F rising and remain in that tripped state until the temperature falls down to some degree substantially below the trip point. This way, the operators only receive one alarm event rather than multiple alarm events for each process temperature excursion.

Some mechanical temperature switches come equipped with a separate adjustment for deadband (also called differential). Setting this deadband adjustment in a mechanical temperature switch requires the technician to repeatedly subject the sensing element to a rising and falling temperature, to check that the switch trips at the proper setting and resets at the proper setting. This is analogous to cycling the process variable back and forth when adjusting the “zero” and “span” settings of an analog transmitter: checking to see that the transmitter repeatedly outputs a 0% signal at the lower range value (LRV) and a 100% signal at the upper range value (URV). 

For discrete temperature-sensing applications demanding high accuracy and repeatability, electronic temperature switch circuits using thermocouples, RTDs, or thermistors may be used instead of a mechanical (bi-metallic or filled bulb) sensing element. The operation and configuration of discrete electronic temperature switches is very similar to that of continuous electronic temperature transmitters.

An example of an electronic temperature switch module is the United Electric One Series shown below:

UE Series One Electronic Temperature Switch

With electronic temperature switches, the adjustment of deadband (differential) is both precise and flexible. Unlike mechanical switches where deadband is primarily a function of friction, and therefore liable to change over time as the device wears, electronic switching circuits may be precisely set for any trip and reset points along its measurement range, remaining very stable over time.

For more information about temperature switches, contact Miller Energy by visiting https://millerenergy.com or by calling 908-755-6700.

Text adapted from "Lessons In Industrial Instrumentation" by Tony R. Kuphaldt – under the terms and conditions of the Creative Commons Attribution 4.0 International Public License.

How to Select a Pressure Switch

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 (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

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.

Pressure Switches - The Stalwart of Pressure Instrumentation

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.

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.

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.

Setting Up the United Electric Controls Series One Safety Transmitter

Here is a two part tutorial showing how to setup your United Electric Series One Safety Transmitter. If you need any additional help or product information, reach out to a product specialist.

Part One Video

Part Two Video

Safety Transmitters For Temperature and Pressure

Series One Safety Transmitter
United Electric Controls

Industrial history is replete with examples of catastrophic accidents. New safety technologies exist today that can prevent or mitigate mishap and disaster in fluid processing and other operations. Modern philosophy of plant safety brings a focus on a proactive approach. Process operators have a new sense of urgency to bring increased levels of safety to their operations.

The United Electric Controls (UE) Series One is a SIL-certified (Safety Integrity Level) transmitter designed solely for safety, alarm, and shutdown. With reliability, speed, and reduced nuisance trips an integral part of its design, the Series One is suitable for application in new installations, or easily integrated into existing operations.

A typical safety loop consists of sensors (such as a pressure or temperature transmitter), controllers, and final control elements. Most SIL-rated pressure transmitters require 300ms to communicate with the controller, then up to 500ms for the controller to send a signal to the final control element (such as a valve). This combined response time may insufficient for some applications. Incorporating the One Series Safety Transmitter, directly connected to the final control element, the total signal time is reduced to 100ms - a large and significant time savings when safe operating conditions have been breached. When used with blowers, pumps and compressors, the One Series makes up a complete safety system with a self-contained sensor, controller, and final control element (the switch) capable of SIL2 without additional safety instrumented function (SIF) components.

The below document provides detailed information about the Series One. Share your process safety challenges with the instrumentation specialists and combine your process knowledge with their product application expertise to produce effective solutions.

Safety Transmitters for Temperature and Pressure from Miller Energy, Inc.

Safety Transmitters Achieve Safety Goals With Reduced Cost and Complexity

Series One Safety Transmitter
United Electric Controls

Process safety experts continually seek sustainable ways to improve the performance of safety critical loops, achieving risk reduction and safety goals in a cost-effective manner. Some view a reduction in complexity of safety related protocols to be a positive development. Traditional or historical approaches to deploying full blown safety systems were generally associated with great expense and high complexity, and still came up short on delivering the needed levels of risk reduction. Process control device and equipment manufacturers have responded with newer technologies and products that better address the safety needs of industrial processing.

In sensor subsystems, United Electric’s certified safety transmitter for pressure or temperature provides a less costly, simple path for process designers, instrument and control engineers, and maintenance personnel. The Series One Safety Transmitters combine several useful safety and monitoring functions into a single, easy to deploy device. Products are available for gauge pressure, differential pressure, and temperature applications. In addition to a 4-20 mA process variable output, the Series One has an embedded programmable high-capacity relay certified as a safety variable output. The Series One Safety Transmitter provides designers the option of a hard wired trip in less than 100 milliseconds, with a tenth of a percent repeatability, along with the monitoring functions of a traditional continuous analog output.

For equipment under control requiring protection, or processes where rapid excursions can initiate dangerous events, this unique pressure and temperature transmitter is addressing process safety time constraints, coupling issues with PLC and DCS units, and adding diversity to the safety instrumented function.

There is a whole lot more to learn about these "Safety right out of the box" industrial pressure and temperature safety transmitters. A product data sheet is provided below, but you can get the latest and most detailed product and application information from a specialist in industrial process measurement and control. Share your safety instrumentation challenges with them, combining your process expertise with their product application knowledge to develop effective solutions.

United Electric One Series Safety Transmitter from Miller Energy, Inc.

Simplifying Plant Safety Instrumentation

Series One Safety Transmitter and Switch
Courtesy United Electric

Safety implementation typically is accomplished by a group that includes plant instrument engineers and technicians. They are charged with developing simple and reliable solutions that increase safety and reduce risk. Safety related events can involve the question of when to shut a process down. These decisions can hinge on the level of key process variables such as flow, level, temperature and pressure. All must be within their specified range at various locations throughout the process, whether within chemical and petrochemical plants, refineries and power plants, or other processing operations. Critical points of measurement can include anything from process vessels to eye wash stations.

For such point safety applications, a properly designed and implemented digital switch with self-diagnostics can be an important part of the answer. As an element of a multiple technology solution, a digital switch-based approach can help eliminate common-mode failures, significantly improve response time, achieve needed safety integrity levels (SILs), and simplify plant safety instrumentation.

United Electric Controls has authored a white paper entitled "Simplifying Plant Safety Instrumentation" that provides some insight into deployment of safety controls. The entire white paper is included below and will prove to be useful reading. More detailed product and application information is available from product specialists. Combining their product expertise with your process knowledge will produce the best solutions.

Simplifying Plant Safety Instrumentation from Miller Energy, Inc.

Improve Process Safety Compliance With Safety Transmitters

Oil Refinery

Industrial processes often are characterized by substantial hazard through their operation. As operators, engineers, and designers, we are responsible for keeping those actual and potential hazardous conditions and occurrences in check. I recently wrote about safety transmitters that can be used to enhance safe industrial process operation and provide compliance with applicable standards.

I located a single sheet document that summarizes the features, benefits, cost savings, and compliance ratings for the safety transmitters from United Electric. You can get more detailed information on these devices and how to properly apply them in your process control scheme by contacting a product specialist. Combining you process expertise with their product application knowledge will generate a solid solution.

United Electric One Series Safety Transmitter from Miller Energy, Inc.

Safety Transmitter for Temperature and Pressure in Industrial Processes

One Series Safety Transmitters
Courtesy United Electric Controls

United Electric Controls has developed a safety transmitter that combines transmitter, safety switch, and display gauge in a single, easily deployed device. The One Series Safety Transmitter includes the manufacturer's patented self diagnostics, along with diverse and redundant signal processing that feed algorithms to detect and respond to internal faults and process abnormalities.

The safety transmitter provides a local switch that can be used for rapid emergency shutdown at the point of measurement or detection, eliminating the need to communicate with other safety controllers and await a response. The safety relay output is programmable and can handle high voltages and currents associated with shutting down control valves, compressors, and other industrial equipment.

In addition to the safety relay output, the One Series Safety Transmitter provides logic outputs that can be employed in voting logic schemes often used to produce warnings prior to a shutdown. For reliability, the unit employs no moving parts and includes self diagnostics with a local display of device status.

There is a whole lot more to learn about these "Safety right out of the box" industrial pressure and temperature transmitters. The product brochure is provided below, but you can get the latest and most detailed product and application information from a specialist in industrial process measurement and control.

United Electric One Series Safety Transmitter from Miller Energy, Inc.

New Product From United Electric - Hybrid Transmitter for Industrial Use

Series One HART Transmitter
Courtesy United Electric

By mid November, United Electric will begin shipping its new One Series hybrid transmitter-switch models that include HART® Communications Protocol. The newly designed product offering includes a transmitter-only model, as well as another model providing a transmitter plus two solid-state relays. Monitoring pressure or temperature in harsh, hazardous and heavy industrial process measurement and control settings is the target application for these loop-powered transmitters. Models will include UL and ATEX approvals for Divisions 1 & 2 (Zones 1 and 2). With the introduction of the One Series, UE is declaring a number of older models obsolete. You can get a listing of the newly obsolete models from your local UE distributor.

The new combination transmitter and switch model provides a HART® 7 loop-powered transmitter, and includes two programmable solid-state relays, an improved backlit LCD display, and a separate IAWTM health status discrete output.The transmitter-only model is a HART® 7 loop-powered transmitter and also features an improved backlit LCD display.

Some operational benefits, quoted directly from United Electric's product announcement documentation:

• With HART® 7 capability, all of the functions available with the two-button keypad are also available via the HART® Communications Protocol. Using a HART®-compatible hand held communicator or a PC with a HART® modem and appropriate asset management software, users have the ability to quickly configure the One Series, including the switching parameters, and save the configuration in their library for cloning additional controls with the same parameters. We believe this is the only Division 1 electronic switch on the market with HART compatibility!
• If the units are connected to a control system with HART® IO allowing bi-directional communication, configuration can be performed remotely, without the need to remove the enclosure cover in a Division 1 (Zone 1) area.
• Using a HART® capable asset management system, the comprehensive diagnostic functions of the One Series can determine the health status 24x7, saving time and money while allowing operators to focus on other critical issues.
• For cybersecurity purposes, the HART® communications can be set to read-only mode that prohibits parameter changes from unauthorized users and creating a potentially dangerous condition.

You can explore these new products in more detail with your United Electric distributor, taking advantage of their freshly acquired new product knowledge. Find out how the advanced new features of the One Series transmitters can enhance the operation and management of your industrial process.