Monday, July 17, 2017

Foundation Fieldbus – Part Two

storage tanks
Almost any operation can benefit from incorporating
Foundation fieldbus
Since automatic control decisions in FOUNDATION fieldbus are implemented and executed at the field instrument level, the reliance on digital signals (as opposed to analog) allows for a streamlined configuration of direct control system ports. If the central control device were to become overloaded for any reason, tasks related to control decisions could still be implemented by operators in the field. This decentralization of the system places less burden and emphasis on the overall central control unit, to the point where, theoretically, the central control unit could stop functioning and the instrumentation would continue performing process tasks thanks to the increased autonomy. Allowing for the instrumentation to function at such an increased level of operation provides a proverbial safety net for any system related issues, with the capacity for independent functionality serving as both a precaution and an example for how process technology continues to evolve from analog solutions to fully end to end digital instrumentation.

Even in terms of the FOUNDATION compliant instrumentation itself, there were two levels of networks being developed at this increased level of operation, initially: the first, H1, was considered low speed, while H2 was considered high speed. As the design process unfolded, existing Ethernet technology was discovered to fulfill the needs of the high speed framework, meaning the H2 development was stopped since the existing technology would allow for the H1 network to perform to the desired standards. The physical layer of the H1 constitutes, typically, a two-wire twisted pair ungrounded network cable, a 100 ohm (typical) characteristic impedance, DC power being conveyed over the same two wires as digital data, at least a 31.25 kbps data rate, differential voltage signaling with a defined threshold for both maximum and minimum peak receive rates, and Manchester encoding. Optical fiber can be used on some installations in lieu of the twisted pair cable.

Most of these specifications were exactly designed to withstand extremely challenging process control environments while still not abandoning the philosophy of being easy to build and implement, especially in terms of new system establishment. The most crucial aspects of many process control systems are streamlined together, allowing for consistent communication and synchronization. All aspects are viewable from both the legacy central controller and also via each individual device. Despite the data rate of 31.25 kbps being relatively slow, what is sacrificed in terms of speed is more than made up for in terms of the system being compatible with imperfect cables and other hiccups which may destabilize a network with faster speeds. The evolved technology, ease of installation, and durability have made the H1 network a widely used implementation of the FOUNDATION fieldbus technology. The standard is currently considered one of a few widely adopted industrial process control communications protocols.

Foundation Fieldbus Equipped Instrumentation – Part One

Foundation filedbus capable pressure transmitter
Foundation fieldbus capable instruments and devices
provide benefits to process operators
Image courtesy Autrol
Autonomous control and digital instrumentation are two capabilities enabling highly precise or complex execution of process control functions. FOUNDATION fieldbus instrumentation elevates the level of control afforded to digital field instrumentation where, instead of only communicating with each other, instruments involved in particular process control systems can independently facilitate algorithms typically reserved for instruments solely dedicated to controlling other instruments. Fieldbus capable instrumentation has become the standard instrumentation for many process industry installations due to the fact the FOUNDATION design principle streamlines process systems. A large contributor to FOUNDATION’s success has been faster installation as opposed to operational controllers which do not feature the fieldbus configuration. Newer process companies, or process control professionals seeking to establish a new system, have gravitated towards fieldbus due to the combined advantages of system conciseness and ease of implementation.

In a typical digital control system, dedicated controllers communicate with field instrumentation (the HART protocol is a prime example of digital communication at work in the industry). The host system controls configuration of instruments and serves as a central hub where all relevant control decisions are made from a single dedicated controller. Typically, these networks connect controllers and field devices through coupling devices and other ‘buses’ which streamline many different instruments into a complete system.

FOUNDATION fieldbus approaches the same network scheme with an important difference. Whereas in a legacy or more conventional system, either algorithmic or manual decisions would need to be implemented via the dedicated system level controllers, instruments utilizing FOUNDATION fieldbus architecture can execute control algorithms at the local device level. The dedicated controller hub is still present, so that operators can view and monitor the entire network concurrently and make status changes. Algorithmic execution of control functions becomes entirely device reliant thanks to the FOUNDATION protocol. Additionally, even though FOUNDATION implements an advanced configuration, some operators use the capabilities introduced in the fieldbus upgrade to implement specific algorithms via each device while concurrently maintaining algorithms in the central controller. This dual algorithmic configuration allows for several advantages, including the ability for increased system precision.

Since individual devices in the control process are calibrated and able to execute their own control functions, issues in the process with particular devices can be isolated and dealt with in a more specified manner by technicians using the instruments in the field. The central operator retains the capacity to use the control hub to alter and direct the control system.

Saturday, July 8, 2017

In Situ Gas Measurement Instrument for Emission Monitoring and Combustion Control

in situ gas monitor
Model GM 35 in situ gas monitor
Image courtesy of Sick USA
The measurement of gas component concentration, especially in operations involving combustion, is necessary to assure regulatory compliance, as well as levels of fuel consumption efficiency. Measurement instrumentation that is reliable, easy to maintain, and accurate delivers needed information without a substantial burden.

What are some attributes of a gas measurement instrument that may prove useful for industrial installations?

  • Ability to measure multiple constituents, such as CO, CO2, H2O, or N2O with a single instrument. 
  • Built-in capability for zero and span test without the need for test gases.
  • In place continuous operation with real time measurement output, eliminating the need for gas sampling or transport. Measurement is accomplished in the process flow.
  • Measurement of temperature and pressure included in unit function.
  • Model available in cross duct and single ended probe type versions.
  • Rugged, properly rated, enclosures for installation outdoors in challenging industrial environments
Each installation scenario will have its own challenges, and each process its own set of measurement requirements. Share your application specifics with a process measurement specialist, combining your own knowledge and experience with their instrument application expertise to develop an effective solution.

Thursday, June 29, 2017

Power System Surge Protection Device

Investments of time and financial resources to operate any business process can have their yield crushed in the blink of an eye by power system anomalies. Businesses and processes run on electric power. Greater levels of IT complexity, process instrumentation, or other electrical equipment generally bring higher levels of exposure to power line surges that can bring unexpected downtime or equipment damage to a going concern.

Prevention through protection is the only available course of action for hardening facilities to the potentially damaging effects of line surges. Dehn, Inc. manufactures products that provide solutions for lightning and surge related problems. Surge protectors and lightning current arrestors, available as compact DIN rail mounted units, function as protective devices for motors, IT equipment, process controls, and instrumentation.

The video below provides a view of how the protective devices function. Without a protection plan in place, any facility is exposed to potential damage. Share your plans and challenges with a product application specialist, combining your facilities knowledge with their product application expertise to develop an effective solution.

Friday, June 23, 2017

Limiting Control Enclosure Temperature Rise

sealed enclosure cooling units heat pipe heat sink
Cooling units for enclosures utilize heat pipe technology and passive heat
sinks to limit enclosure temperature rise.
Courtesy Advanced Cooling Technologies
Control and equipment enclosures are most often tightly sealed for the safety of personnel, as well as the protection of interior components from environmental intrusion. This physical barrier also inhibits the dissipation of heat produced by devices within the enclosure. Electrical and electronic gear employed in control and measurement systems commonly has an upper limit for the temperature of its operating environment. Above that maximum, performance becomes undefined and devices may deteriorate, malfunction, or fail.

Advanced Cooling Technologies specializes in the design and manufacture of cooling devices for control and equipment enclosures. The company employs heat pipe technology, as well as heat sinks, to transfer substantial amounts of heat from within sealed enclosures. The special design of the cooling units maintains the rated performance of the enclosure and effectively moves heat from enclosure interior to surrounding environment. Units encompass a range of sizes, configurations and capacities.

Share your enclosure cooling challenges with product application specialists, combining your own knowledge and experience with their product application expertise to develop effective solutions.

Friday, June 16, 2017

Hydrostatic Pressure Measurement for Liquid Level

smart pressure transmitter for industrial process measurement and control
Smart transmitters are capable of performing advanced calculations
to infer liquid level from hydrostatic pressure measurement
Courtesy Autrol America
Pressure measurement is an inferential way to determine the height of a column of liquid in a vessel in process control. The vertical height of the fluid is directly proportional to the pressure at the bottom of the column, meaning the amount of pressure at the bottom of the column, due to gravity, relies on a constant to indicate a measurement. Regardless of whether the vessel is shaped like a funnel, a tube, a rectangle, or a concave polygon, the relationship between the height of the column and the accumulated fluid pressure is constant. Weight density depends on the liquid being measured, but the same method is used to determine the pressure.

A common method for measuring hydrostatic pressure is a simple gauge. The gauge is installed at the bottom of a vessel containing a column of liquid and returns a measurement in force per unit area units, such as PSI. Gauges can also be calibrated to return measurement in units representing the height of liquid since the linear relationship between the liquid height and the pressure. The particular density of a liquid allows for a calculation of specific gravity, which expresses how dense the liquid is when compared to water. Calculating the level or depth of a column of milk in a food and beverage industry storage vessel requires the hydrostatic pressure and the density of the milk. With these values, along with some constants, the depth of the liquid can be calculated.

The liquid depth measurement can be combined with known dimensions of the holding vessel to calculate the volume of liquid in the container. One measurement is made and combined with a host of constants to determine liquid volume. The density of the liquid must be constant in order for this method to be effective. Density variation would render the hydrostatic pressure measurement unreliable, so the method is best applied to operations where the liquid density is known and constant.

Interestingly, changes in liquid density will have no effect on measurement of liquid mass as opposed to volume as long as the area of the vessel being used to store the liquid remains constant. If a liquid inside a vessel that’s partially full were to experience a temperature increase, resulting in an expansion of volume with correspondingly lower density, the transmitter will be able to still calculate the exact mass of the liquid since the increase in the physical amount of liquid is proportional to a decrease in the liquid’s density. The intersecting relationships between the process variables in hydrostatic pressure measurement demonstrate both the flexibility of process instrumentation and how consistently reliable measurements depend on a number of process related factors.

Solutions to process instrumentation and measurement challenges are most effective when developed in concert with a product application specialist. The combination of user knowledge and experience with product application expertise will lead to a successful project.

Monday, June 12, 2017

Added Services Enhance Product Value

handshake by collaborators on industrial process control automation project
Collaboration and cooperation leverages the pool of knowledge
and experience brought to bear on problem solving
We have written previously about the contribution of a technical sales representative and the added value he or she can bring to the purchase of a physical product. With a daunting array of potential product variants available, it can be difficult and time consuming to reach a knowledge level that enables a confident selection of process automation products for a specialized application. The tech sales rep's knowledge of currently available products and their application specialties and limitations can speed the selection process and contribute to a positive outcome for for all stakeholders.

At the company level, many technical representatives commit to bringing factory level training resources to their customers. Reading instruction manuals can often fail to instill real understanding about the application, use, and upkeep of process and automation gear. Plus, manuals provide only one way communication. Training conducted by experienced, knowledgeable, factory trained individuals can instill almost tangible levels of comprehension in operators, users, and supporters of process and automation equipment.

Field services, in the form of start-up, calibration, repair, or regular maintenance of instruments and equipment are also provided by many technical sales firms. Again, bringing to bear broad experience and factory level training, technical representatives can function as an efficient outsource for essential tasks that may require special skills or knowledge. Repair, whether in-house or facilitated through the factory, is another way in which technical representatives leverage their experience and knowledge into offerings that bring value to their customer base.

Face it, if all that was needed was quick delivery of process and automation gear, would be your primary supplier. These are sophisticated instruments, apparatus, and equipment, requiring skill, knowledge, and experience to assure proper selection, installation and operation. A good technical rep firm knows that its customers need more than a product in a box or crate. It's results that count, output, and Hile Controls of Alabama is committed to assisting customers wherever Hile's expertise can help leverage positive outcomes for their customers.