Diaphragm Seals: Critical Isolation and Protection for Your Process Instruments

Diaphragm Seal courtesy of
AMETEK U.S. Gauge

Diaphragm seals play a critical role in protecting items like pressure switches, gauges, and transmitters from the fluid being evaluated by the sensor. The seal is a flexible membrane which both seals and isolates an enclosure. Pressure crosses the barrier without inhibition, but the material being contained does not. Typical materials composing diaphragm seals are elastomers, with rubbers being the prime substance in both general and specialty purposes.

In the operating principle of the diaphragm seal, the chamber between the diaphragm and the instrument is filled with system fluid, allowing for the transfer of pressure from the process media to the sensor being protected. The seals are attached to the process by threaded, open flange, sanitary, or other forms of connection.  The seals can also be known as ‘chemical seals’ or ‘gauge guards’. Stainless steel, Carpenter 20, Hastelloy, Monel, Inconel, and titanium are used in high pressure environments, and some materials are known to work better when paired with certain chemicals.

Diagram of diaphragm seal
(courtesy of Wikipedia)

Sanitary processes, such as food and pharmaceuticals, use diaphragm seals to prevent against the accumulation of process fluid in pressure ports. If such a buildup were to occur, such as milk invading a pressure port on a pressure gauge and spoiling, the quality and purity of the fluid in the process may be compromised. Extremely pure process fluids, like ultra-pure water, could be contaminated by the metal surface of a process sensor. 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.

Diaphragm seals protect the sensors
on pressure switches like this
United Electric Controls model.

Despite their protective function and reliability, there are some potential complications related to diaphragm seals. Devices are now built to address and counter many potential issues related to process monitoring involving diaphragm seals. 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 improve performance while ensuring protection from corrosion. The seals’ ability to protect both process quality and their own vitality make them essential components of process control.

For more information on diaphragm seals, visit Ives Equipment at http://www.ivesequipment.com or call (877) 768-1600.

Introduction to Flowmeters

Magnetic flowmeters
(courtesy of Siemens)

Flowmeters measure the rate or quantity of moving fluids, in most cases liquid or gas, in an open channel or closed conduit. There are two basic flow measuring systems: those which produce volumetric flow measurements and those delivering a weight or mass based measurement. These two systems, required in many industries such as power, chemical, and water, can be integrated into existing or new installations.

Turbine flow meter
internal view
(courtesy of Niagara)

For successful integration, the flow measurement systems can be installed in one of several methods, depending upon the technology employed by the instrument. For inline installation, fittings that create upstream and downstream connections that allow for flowmeter installation as an integral part of the piping system. Another configuration, direct insertion, will have a probe or assembly that extends into the piping cross section. There are also non-contact instruments that clamp on the exterior surface of the piping add gather measurements through the pipe wall without any contact with the flowing media.

Because they are needed for a variety of uses and industries, there are multiple types of flowmeters classified generally into four main groups: mechanical, inferential, electrical, and other.

Variable Area Flowmeters
(courtesy of Siemens)

Quantity meters, more commonly known as positive displacement meters, mass flowmeters, and fixed restriction variable head type flowmeters all fall beneath the mechanical category. Fixed restriction variable head type flowmeters use different sensors and tubes, such as orifice plates, flow nozzles, and venturi and pitot tubes.

Inferential flowmeters include turbine and target flowmeters, as well as variable area flowmeters also known as rotameters.

Laser doppler anemometers, ultrasonic flowmeters, and electromagnetic flowmeters are all electrical-type flowmeters.

For any flowmeter application or question, visit Ives Equipment at www.ivesequipment.com or call (877) 768-1600.

Instrumentation and Controls for the Grain Industry

Instruments and control for grain producers.

Abstracted with permission from the Siemens "For the Love of Grain" article.  View the complete document at  the bottom of this post or download it from Ives Equipment here.

A successful grain merchant during the 1840s is considering expansion in the coming years. Recent years have been fruitful, but there are rumors of a new invention on the market: a grain elevator. Claims are that this elevator is able to unload more than 1,000 bushels each hour! Compare this to current operations where workers carry sacks of grain on their backs from wagons to waiting ships. Our grain merchant has seen firsthand the hazards of this process – everything from suffocating and explosive grain dust to the daily stresses on workers’ bodies. Will this new technology be able to increase the merchant’s profits as well as make a safer working environment for employees?

Over a century and a half later, mechanized equipment is now an essential part of the grain industry, from planting and growing to harvesting, handling, and milling grain. Your challenges are still the same as those of nineteenth century grain operators, though – how can you improve processes and cut costs while also increasing safety?

Promoting a culture of safety

Working with grain has the potential to be deadly, especially when grain is in motion. Similar to ‘quicksand,’ moving grain can bury a worker in seconds. In 2010, U.S. grain operators reported that fifty-one workers had been trapped in grain, more than in any year since Purdue University began collecting data on grain entrapments in 1978. Sadly, almost half of these entrapments led to fatalities.

Increasing automation

To prevent deadly occurrences such as these, the grain industry is increasingly taking steps to reduce grain handling and storage hazards. Improving efficiency in grain facilities through automation is becoming a growing industry trend. A concern for safety is one driver behind automating operations, as a reduction in human interactions with grain decreases the occurrence of accidents.

Another reason for the push towards automation is that owners are constantly looking to increase production and reduce expenses while still producing a high quality product. A solution is to invest in automated processes in a facility. Many facilities have moved to complete automation of production, termed Totally Integrated Automation (TIA).

Refining inventory management 

Tracking inventory in grain silos is a significant component of a successful grain operation. Managing raw materials and finished products is essential for keeping processes efficient and optimizing inventory ordering and shipments. By knowing where materials are located, companies can use these resources more effectively, decreasing human intervention and increasing efficiency. As well, checking bin levels on a regular basis requires substantial labor costs. To make inventory track-ing faster and more streamlined, the industry is continually moving towards automated inventory management.

Read complete article below:

Instrumentation, Automation and Control Solutions for the Grain Industry from Ives Equipment

New Ives Equipment Video

Ives Equipment, founded in 1954, provides a diverse range of process control equipment, including valves, regulators, wireless products, flow products, pressure gauges, control products, level instrumentation, sanitary products, temperature instruments, analytical products, electric heat trace and bio-pharmaceutical products.

For more than 60 years, Ives Equipment Corporation has successfully served the industries of eastern and central Pennsylvania, Delaware, Maryland, metro NY, New Jersey, Virginia and Washington DC with the latest in process control equipment and services.

The Ives business is built on a foundation of quality people, highly trained and experienced, who take a keen interest in finding the optimum solutions to customers' control problems.

When It Comes to Pressure & Temperature Switches, Understand the Difference Between Switch Normal and Process Normal

Diagram of pressure
switch. Note the SPDT
electrical switch on top.
  (Courtesy of United
Electric Controls)

The normal status of a switch can be a confusing aspect of understanding the function of connected electrical and logic components in a process control application. The misunderstanding stems from the ambiguity of the word normal. Typically, electrical switch contacts are classified as being normally-open or normally-closed, referring to the open or closed status of the contacts under normal conditions. The key in understanding the normal state of a switch contact requires one to dissociate from their thinking, the concept or definition of normal used in everyday conversation. Where, among friends in casual conversation, the word normal tends to refer to what is expected, the normal status of the switch is, explicitly, its contacts electrical status when no stimulus is applied, that is, when the switch is at rest. An applied example of this definition is a momentary-contact pushbutton switch is not being pressed, because, when the pushbutton is not being pressed, the switch is experiencing no physical stimulation. Electrical schematic drawings always represent switches in their normal status. When an electrical switch on a lamp is in its normally-open state, the switch is open while receiving no physical stimulation.

Temperature switch (courtesy of
United Electric Controls)

The concept of normal is somewhat more complex when applied to pressure and temperature switches. Pressure and temperature switches are actuated, not by electrical signal or human contact, but by process related stimuli, i.e. temperature, flow, pressure, or level. A flow switch is actuated by a defined amount of flow through a pipe.  Lets say a flow switch is engineered to trigger an alarm when the flow rate inside a pipe is below a certain level. Even if the contacts of the flow switch are designated as being in their normally-closed status, the switch will be open when enough fluid is flowing through the pipe. The normal switch status (closed) indicates an abnormal process flow rate condition, because the switch is only going to be in its normal electrical status when the flow is low. Considering this inverse nature (normal switch status indicating abnormal process status), switch contacts are conventionally represented in accordance with the switch operation and not the process operation. The manufacturers of the pressure and temperature switches cannot predict the normal status of particular processes in which their switches will be used. By utilizing the conventional switch terminology, there is a common status designation for the normal status of the switch. The designation is applicable and readable regardless of the process conditions of the specific industry using the switch. This convention provides for universal comprehension of control system electrical schematics and other symbolic representations of control system operation.

Pressure switch (courtesy of
United Electric Controls)

In making the connection between the normal state of switch contacts and the normal state of a process, one should relate the switch state to the process condition which would serve as the stimulus to change the switch state. For a limit switch, which responds to physical contact by an object, normal means the target is not contacting the switch. For a proximity switch, normal means the target is far away. A normal pressure switch condition occurs when the pressure is low, or may even indicate a vacuum. Level switches are normal when the level is empty. Normal for a temperature switch means the temperature is low. Flow switches are normal when there is a low flow rate, or the fluid is stopped. Both an understanding of normal as defined by the manufacturer of the switch and normal in terms of industry specific processes is necessary to correctly interpret the status of an operation. Once the concept of normal used in everyday conversation is uncoupled from your process control thinking, things fall into place easily.

Industrial Control Valve Actuator Operating Principles

Control valve actuators control fluid in a pipe by varying the orifice size through which the fluid flows. Control valves contain two major components, the valve body and the valve actuator. The valve body provides the fluid connections and immovable restrictor comprised a valve stem and plug that is in contact with the fluid that varies the flow.

The valve actuator is the component that physically moves the restrictor to vary the fluid flow. Three actuator types are used in control valves and they include spring and diaphragm, solenoid, and motor. As the name suggests the spring in diaphragm actuator uses a spring and a diaphragm to move the valve stem and plug.

A 15 PSI pneumatic signal enters the housing at the top of the actuator. As pressure is exerted on the diaphragm a downward force is applied against the spring which moves the restrictor. The diaphragm moves until it creates an equal but opposing force against the spring at which time the motion stops as the plug meets the valve seat. With no air pressure the restrictor is pushed upward by the spring to act as a normally open control valve. To vary the position of the restrictor and flow through the valve, a current to pressure transducer can be used to provide a three to 15 PSI signal to the diaphragm.  At 3 PSI the valve is maintained open, and 15 PSI the valve is maintained closed. Pressures between the three to 15 PSI range proportionally change the flow of the valve. For example a pressure of 9 PSI applied to the diaphragm moves the spring and valve stem to 50 percent operating range.

For on /off control of the valve, a solenoid is used to actuate the valve to a fully closed or fully open position. Applying current to the coil generates a magnetic field that moves the plunger downward against the return spring. With zero current applied to the coil the spring pulls the plunger upwards to the fully open position for a normally open state control valve.

Another method for variable valve positioning uses a motor and is referred to as proportional control mode. Using a gear motor attached to the valve stem a servo amplifier provides a DC control signal that moves the valve to the desired position. Feedback is achieved with the wiper arm attached to the valve stem that sends a signal back to the servo amplifier where the position is monitored the servo amplifier drives the motor until the control signal is equal to the feedback signal.

Watch the video below for an illustrated explanation. For more information on control valves, contact Ives Equipment at 877-768-1600 or visit http://www.ivesequipment.com.

SITRANS FC430 Coriolis Flowmeter Wins Control Engineering’s 2017 Engineers’ Choice Award

SITRANS FC430 Coriolis Flow Meter

The Siemens SITRANS FC430 Coriolis flow meter, with National Type Evaluation Program custody transfer approval, for volume and mass liquid flow,  is a Control Engineering 2017 Engineers’ Choice Awards Winner.

The Siemens SITRANS FC Coriolis flow sensor delivers mass flow, volume flow, density, fraction and temperature measurement of both liquids and gases with exceptionally high accuracy and low pressure drop.

Siemens Coriolis flow meters are user-friendly to set up and use day-to-day. The meters stand up to the most demanding process industry conditions and continue to operate in the noisiest of environments – from hazardous chemicals to fiscal metering, custody transfer to compressed natural gas fuel dispensing. Its compact design makes installation easy even in the tightest spaces.

For more information on Siemens products, visit Ives Equipment here or call (877) 768-1600.