Users seek reliability, accuracy, and ruggedness

Even in the ever-evolving world of process control, things occasionally find equilibrium. At least, for the short term. Usage trends for process variable transmitters (PVTs) have done that since Control Engineering and Cahners Research surveyed readers a year ago. Key selection criteria were reliability, accuracy, environmental ruggedness, ease of calibration, and ease of maintenance, i...

By Staff April 1, 2002

Even in the ever-evolving world of process control, things occasionally find equilibrium. At least, for the short term. Usage trends for process variable transmitters (PVTs) have done that since Control Engineering and Cahners Research surveyed readers a year ago. Key selection criteria were reliability, accuracy, environmental ruggedness, ease of calibration, and ease of maintenance, in descending order.

In the latest study, responses to 10,000 e-mails sent to subscribers yielded a response rate of 4%. Results were based on 230 respondents involved in the evaluation, specification, recommendation, installation, and/or purchase of process transmitters.

As might be expected, the top applications PVTs were the big four of process sensing-temperature, pressure, flow, and level. Analytical variables such as conductivity, pH, and ORP closely followed the ‘big four.’ Multivariable units appeared at the bottom of the list.

Penetration of multivariable transmitters into the PVT marketplace has been slow though steady, but in the recent economic slowdown-certainly since 9/11-it has not grown at all. According to Lou DiNapoli, product manager, transmitters, at Siemens Energy & Automat ion (Spring House, Pa. ), ‘Users are not willing to pay for any capability that they do not need. In this economy, the few transmitters specified are held to exact criteria to make sure that project costs are controlled. Suppliers are now regularly ‘shopped’ to get the lowest price, and brand loyalty seems a thing of the past. Price seems to have become a major differentiator in this climate.’

Applications rule!

When asked if they preferred to buy integrated units or individual components, 47% of survey participants said it depends on the application. Another 36% preferred integrated units. Of the remaining respondents, 7% preferred individual (separate) components. These results are not vastly different from those of the previous survey in which 52% of participants bought application-specific components, 37% integrated units, and 11% individual components (sensors, electronics, software, mounting hardware, etc.).

Downsized engineering departments can mean that processes might have to make do with off-the-shelf components to provide the control functions needed. However, many large process plants were commissioned years or even decades ago in an engineering environment that provided personnel and budget to fine tune control processes. Hence, application-specific purchasing of PVT components may be ‘locked in’ by the previous design.

Even in a down economy, limited ‘greenfield’ construction or expansion of existing processes do not give control engineering staffs the ability to simply pick integrated components. Increased pressure on quality requirements and the ability to sustain flexible manufacturing and delivery responsiveness have undoubtedly conspired to keep application-specific PVTs an engineering necessity.

Selecting a PVT

No matter the application or type of tr ansmitter selected, survey respondents were specific in their choice of product selection criteria. At the top of the list was reliability with 87% of the respondents voting ‘most important.’ The next tier of criteria was accuracy and environmental ruggedness at 70% and 69% each. Ease of calibration placed fourth at 56% and ease of maintenance placed fifth at 53% response.

According to Scott Nelson, director of worldwide pressure marketing at Emerson Process Management (Chanhassen, Minn.), ‘Reliability is always the number one selection criterion with our users. Reliability issues will cause more trouble than performance issues macroscopically. If a transmitter stops functioning, it directly impacts plant availability or a loop being up.’

Al Erwin, product manager for transmitters at Yokogawa Corp. of America (Newnan, Ga.) agrees that reliability deserves to be at the top of the list. ‘Failure of a transmitter costs time and money. When failure occurs, it is always treated as an emergency situation.’

Because of the capital investment involved, process plants are built for the ‘long haul.’ As with any stable manufacturing environment, the equipment that helps it run efficiently and effectively must be built to function correctly for the long term. This implies stability for the existing state of affairs-status quo.

For more transmitter products, visit www.controleng. com/freeinfo .

Columbia Dataforth PSI-Tronix

Transmitter performs under pressure

Newnan, Ga.- EJA Series digital pressure transmitters, also known as the DPharp, meet 6-sigma conformance criteria and boasts resistance to overpressure events common in many applications. Dpharp’s exclusive digital sensor eliminates the need for and the inaccuracy of analog-to-digital conversion required for all resistive and capacitive sensors commonly used to measure pressure. Accuracy is 0.075% of calibrated span. All are rated NEMA 4X, FM/CSA, explosion-proof, and intrinsically safe. Yokogawa Corp. of America

Demanding application transmitters

Stamford, Conn.- TX1500 Series transmitters are comprised of isolated 4-20 mA devices intended for demanding applications. The transmitters are isolated to 1,500 V rms , and feature 9-50 V compliance, a turndown ratio of 10:1, NMV protection to 120 V ac, and a temperature operating range of -40 to 185 °F. Packaging is NEMA-4X with shock protection to 55 g. Two-wire operation power is obtained directly from the 4-20 mA loop with no need for separate power input, simplifying field wiring and eliminating noise pickup from power lines. Omega Engineering

Flowmeter is accurate, reliable

Greenwood, Ind.- Promass 80/83 flowmeters offer accurate, cost-effective, and reliable Coriolis flow measurement. In addition to excellent repeatability, the units are said to provide extremely accurate measurement of mass and volume flow in liquids and gases. Other process parameters, including density, temperature, % solids, and ° Brix, can also be measured. Up to four signal outputs are available. FOUNDATION fieldbus, Profibus, and HART communications options are also available. A wide choice of materials for process connections and measuring tubes is offered. . Endress+Hauser

‘Smart’ transmitters

Phoenix, Ariz.- Honeywell’s ST 3000 Series 900 Gauge Pressure Transmitters bring ‘smart’ technology to many pressure measurement applications with varying process interface requirements. They output a signal proportional to the measured variable in an analog 4-to-20 mA, digital DE protocol, FOUNDATION fieldbus, or HART format. The new STG99L model measures pressures from 0 to 10,000 psi for applications, such as high-pressure reactors and high-pressure oil and gas recovery. Honeywell

Pressure transmitter family

Foxboro, Mass.- Invensys Process Systems’ Measurements & Instruments unit offers a new family of Foxboro pressure transmitters. The family-which includes a versatile Multirange line, a high-performance Premium Performance line, and a cost-saving Multivariable line-is said to provide a competitively priced product for almost every pressure measurement application and price point. All three offer a choice of communications protocols, including HART, FOUNDATION fieldbus, Profibus, and FoxCom. Invensys Process Systems

Custody transfer flow measurement

Peabody, Mass.- UFM500, Altosonic V, liquid ultrasonic process meter maintains an uncertainty of less thanmeasures the complete flow profile, ensuring custody transfer-class measurement. Krohne Inc.

High-tech diagnostics

Spring House, Pa.- The newest version of Siemens Sistrans P, DSIII Series pressure transmitters being configured and distributed exclusively here in the U.S. by Siemens Moore Process Automation Inc. DSIII pressure transmitter incorporates software that provides extensive diagnostic and simulation capabilities. Diagnostics include high- or low-signal limit alarms; peak value registers for pressure, sensor temperature, and electronics temperature; and two programmable ‘watchdog’ timers that alert the operator when user-set maintenance and calibration times occur. Siemens Energy & Automation

Historical transmitters, next generation

Eden Prairie, Minn.- For many users, ‘Rosemount’ has historically meant ‘pressure transmitter.’ Model 1151, introduced in 1969, then Model 3051, introduced in 1988, provided users with the high reliability, installed repeatability, and long-term stability. In 2001, Rosemount, a division of Emerson Process Management, introduced 3051S Series, which is said to provide users with advanced PlantWeb functionality and deliver enhanced performance and reliability in a highly scalable platform. Emerson Process Management

Flowmeters feature add-on transmitters

Boulder, Colo.- Micro Motion’s Coriolis flowmeters feature many add-on transmitter modules, ranging from basic, single-variable flow measurement to enhanced multivariable transmitters with mass, volume, temperature, and density outputs. These transmitters feature local operator interfaces that can be placed in C1D1/Zone 1 areas for easy access to process information, flow totalizers, and meter diagnostics. They can be mounted integrally to the sensor or up to 1,000 ft away using standard 4-wire cable, which can reduce installed costs considerably. Micro Motion

‘No threat’ transmitters

City of Industry, Calif.- Approved by various international regulatory agencies, Barton/Fuji’s FCX transmitters are intrinsically safe and explosion-proof. For a wide range of applications and process media, FCX transmitters measure, display, alarm, and provide level, pressure, and/or flow data. Gauge, absolute, flanged level, and differential pressure models are available. Wetted parts can be 316 stainless steel, Hastelloy, Monel, or Tantalum. Turndown is 16:1 or 100:1 depending on model. Output can be 4-20 mA or retrofitted to full digital with a snap-in module. Barton Instrument Systems

Level transmitters

Tustin, Calif.- 8250 ProcessPro level transmitters are designed for use with their developer’s pressure, magnetostrictive, and ultrasonic level sensors. They are said to provide an industry-first turnkey continuous level measurement system solution. The transmitters feature single- and dual-channel input with one 4-20 mA output for each input channel. All outputs are fully scaleable and reversible. 8250 ProcessPro also comes equipped with two relays and the ability to support additional externally mountable relays for a total of four. It also features a front pushbutton setup and configuration. +GF+Signet