Selecting Single-ended vs. Differential Voltage Measurement for Process Measurement - Part 1 of 2

Acromag manufactures an extensive array
of signal conditioning modules

Process control requires process measurement. The industry provides a enormous array of measuring devices for almost every conceivable process parameter. Selecting the right signal conditioner that will convert a current process state into a signal to be transmitted to and utilized by a controller can be challenging. One area of confusion centers around whether to use differential or single-ended voltage measurement.

Acromag, Inc., a globally recognized manufacturer of signal conditioning equipment for industrial process measurement and control, has provided a white paper that helps sort out reasons behind a beneficial selection of single-ended or differential voltage measurement devices. Explanation of how each functions and tips on selection criteria for an application are also provided. The technicality of the language is at a level that is comprehensible to most, but retains that exciting engineering edge for the purists among us. The first part of two (Part Two), provided below, focuses mostly on single-ended measurement. Part two covers differential.

Top flight assistance with your process measurement and control application challenges is available from M.S. Jacobs & Associates.

Single-Ended vs. Differential Voltage Measurement Part 1 of 2 from MSJacobs-Cali

Get To Know MS Jacobs & Associates for Industrial Process Control Instruments and Equipment

MS Jacobs serves the electric power generation industry,
as well as chemical, oil and gas, water and wastewater

M.S. Jacobs and Associates has been a leading manufacturer's representative and distributor of industrial instrumentation and controls since 1945.  Expanding from its original focus on the steel industry, MS Jacobs services and supplies products in all major industrial markets, including power generation, chemical processing, pulp and paper, oil and gas production, water and wastewater treatment, and nuclear power generation.

The company's longevity and dedication to the industrial market has resulted in a broad offering of superior quality products for flow, level, pressure, and temperature measurement, as well as filtration products and valves. Everyone at MS Jacobs takes pride in the company's ability to solve tough applications and provide exceptional customer service with a team of trained outside sales engineers and inside customer service representatives.

MS Jacobs' Pittsburgh service center provides instrument calibration and repair for MSJ's complete line of products, as well as those of other manufacturers. The company carries factory authorization for repair of numerous manufacturers' industrial process instrumentation products. The service center also provides custom assembly of instruments and other gear to meet customer requirements. Completed assemblies are tested and certified prior to shipment.

Reach out to MS Jacobs & Associates for the products and services that move your process instrumentation and control projects toward a successful completion.

MS Jacobs Line Card & Product Offering from MSJacobs-Cali

Non-Invasive Measurement of Extremely Low Flow Rates

Industrial process measurement and control operations present a continuous stream of challenges to designers, engineers, operators, and equipment manufacturers. The innumerable combinations of environmental, safety, financial, and other concerns have lead to a wide variety of instruments, equipment, and techniques for meeting specific process requirements. A critical element of many industrial processes is the measurement of liquid flow. Matching the best available flow measurement technology or product to an application calls for through knowledge of the process, the medium being measured, and the strengths and limitations of a proposed measurement device. The most current product and application information is available from specialists in flow measurement.

The video illustrates how a special adaptation of ultrasonic flow measurement technology is utilized to measure extremely low flow rates. Specific product information is also included, showing the advantages and specific application ranges of this specialty product from Flexim Americas.

Non-Invasive Measurement of Extremely Low Liquid Flow Rates from MSJacobs-Cali

Oxygen or High Purity Service Valve Preparation

Industrial Ball Valve
Courtesy Marwin Valve

Oxygen is used extensively throughout a wide range of industrial processes. Medical, deep-sea, metal cutting, welding, and metal hardening are a few examples. The steel industry uses oxygen to increase capacity and efficiency in furnaces. As a synthesis gas, oxygen is also used in the production of gasoline, methanol and ammonia.

Odorless and colorless, oxygen is concentrated in atmospheric air at approximately 21%. While O2, by itself, is non-flammable, it vigorously supports combustion of other materials. Allowing oils or greases to contact high concentrations of oxygen can result in ignition and possibly explosion. Oxygen service preparation of an industrial valve calls for special cleaning processes or steps that remove all traces of oils and other contaminants from the valve to prepare for safe use with oxygen (O2). Aside from the reactive concerns surrounding oxygen, O2 preparation is also used for applications where high purity must be maintained and valves must be free of contaminants.

Gaseous oxygen is noncorrosive and may be used with a variety of metals. Stainless steel, bronze and brass are common. Liquid oxygen presents unique challenges due to cryogenic temperatures. In this case, valve bodies, stems, seals and packing must be carefully chosen.

Various types of valves are available for oxygen service, along with a wide array of connections, including screwed, socket weld, ANSI Class 150 and ANSI Class 300, DIN PN16 and DIN PN40 flanged ends. Body materials include 316 stainless steel, monel, bronze and brass. Ball and stem material is often 316 stainless steel or brass. PTFE or glass filled PTFE are inert in oxygen, serving as a common seat and seal material employed for O2 service.

Common procedures for O2 service are to carefully deburr metal parts, then meticulously clean to remove all traces of oil, grease and hydrocarbons before assembly. Valve assembly is performed in a clean area using special gloves to assure no grease or dust contaminates the valve. Lubricants compatible with oxygen must be used. Seating and leakage pressure tests are conducted in the clean area, using grease free nitrogen. Specially cleaned tools are used throughout the process. Once assembled, the valves are tested and left in the open position. A silicone desiccant pack is usually inserted in the open valve port, then the valve ports are capped. A warning label about the desiccant pack's location is included, with a second tag indicating the valve has been specially prepared for oxygen service. Finally, valves are individually sealed in polyethylene bags for shipment and storage. Different manufacturers may follow slightly differing protocols, but the basics are the same. The valve must be delivered scrupulously contaminant free.

The O2 preparation of valves is one of many special production variants available to accommodate your special application requirements. Share your valve requirements and challenges with a valve specialist to get the best solution recommendations.

Video Reenactment and Analysis of Industrial Fire and Explosion

All facilities have some element of risk

Industrial accidents range in severity and impact from minuscule to catastrophic. As operators, owners, or technicians involved with industrial operations, we all have a degree of moral, ethical, and legal responsibility to conduct our work in a manner that does not unduly endanger personnel, property, or the environment. Maintaining a diligent safety stance can be helped by reviewing industrial accidents at other facilities. There is much to learn from these unfortunate events, even when they happen in an industry that may seem somewhat removed from your own.

The U.S. Chemical Safety Board, or CSB, is an independent federal agency that investigates industrial chemical accidents. Below, find one of their video reenactments of an explosion that occurred in Texas in 2013, along with their findings regarding the cause of the incident. Check out the video and sharpen your senses to evaluate potential trouble spots in your own operation.

Contact M.S. Jacobs & Associates for any safety related information you may need concerning their lines of industrial and process control products.

New Product: Non-Contact Radar Level Transmitter

Model R96
Non-Contact Radar Level Transmitter
Courtesy Magnetrol

A new entry into the non-contact radar level measurement transmitter arena has been released by Magnetrol, a well known manufacturer of level and flow measurement instrumentation for the industrial process control field. The new Model R96 Non-Contact Radar Level Transmitter is intended primarily for applications where continuous fluid level measurement is required.

The company sums up the technical capabilities with their description of the product...

"Virtually unaffected by the presence of vapors or air movement within a vessel’s free space, the two-wire, loop-powered, 6 GHz Radar transmitter measures a wide variety of liquid media in process conditions ranging from calm product surfaces and water-based media to turbulent surfaces and aggressive hydrocarbon media."

The Model R96 level transmitter offers features that combine to deliver a state-of-art instrument for accurate continuous level measurement. A product brochure is included below. Contact application specialists to formulate the right product configuration for your level measurement challenge, or to get more detailed information.

Non-Contact Radar Level Transmitter From Magnetrol from MSJacobs-Cali

New Metal Seated Ball Valves Introduced

Cutaway view of a metal seated ball valve
Courtesy SVF Flow Controls

Ball valves are utilized across a wide range of industrial process fluid flow control applications. Consequently, there are many ball valve variants, each designed to satisfy a particular range of application requirements.

Reviewing some of the attributes of ball valves that might make them the best choice:

• Tight closure.
• Very low resistance to flow.
• Best suited for applications requiring fully closed or open control.
• 90 degrees of rotational motion from open to closed position yields rapid response.
• Comparatively compact, without the space requirement for extending stem movement as required by some other valve types.
• Wide range of construction materials for the body, stem, ball, and seals.
• Moderate force required for actuation.
• A full size port provides for very low pressure drop across the valve when fully open.
• Requirements for maintenance are generally low. 
• No lubrication required.

One limiting factor for the application of ball valves, as with many other valve types, is the seat material. Most often, seats are fabricated from elastomeric or other "soft" materials. While these materials provide good sealing performance, their inability to withstand higher fluid temperatures makes them unsuitable for some industrial applications. To satisfy a wider range of process applications, some manufacturers offer metal seated ball valves. The metal seated valves are designed to meet severe service applications involving high temperature, erosive fluids and other challenging shutoff requirements where soft seats would rapidly deteriorate.

One manufacturer, SVF Flow Controls, provides metal seated ball valves in sizes 1/2" through 12" with a full port design. Because of their intent for severe service applications, metal seated ball valves are generally provided with other design features that enable their application across a wide range of high temperature or erosive fluid applications.

I have included a data sheet below that provides additional technical information, or you may contact a valve application specialist for any assistance you need. Share you fluid control challenges and get effective solutions.

SVF Flow Control M-Seat Metal Seated Ball Valves from MSJacobs-Cali