Quartzdyne Pressure Transducers

Quartzdyne Newsletter

Circuit Life Update

It has been nearly two years since Quartzdyne presented circuit reliability statistics at the 2001 HITEN conference in Oslo, Norway. Since then, we've compiled another 1.8 million hours of destructive testing on our various circuit technologies. As a manufacturer of pressure transducers designed for high temperature use, we have found that providing circuits to survive the rigors of high temperature and high shock environments requires constant vigilance. The results of our ongoing nine-year study comprises nearly four million test hours on 960 circuit assemblies. Circuit technologies tested include surface-mount, through-hole, and hybrid assemblies containing commercially available discrete bipolar transistors, small-scale integrated circuits and passive devices. All of the test samples are essentially the same circuit with only minor packaging-driven differences. The testing consists of time at elevated temperature, as well as thermal cycles distributed over the duration of the test. Some tests also include periodic high frequency shock and vibration. All circuits are tested to failure.

Based on the test results, we've concluded that surface-mount technology can be used reliably at temperatures as high as 150°C for one year, or up to five years at 125°C. With properly constructed hybrid assemblies, more than two years at 200°C or five years at 180°C can be expected. Since the first release of this paper in June 2001, the number of hybrid units tested has increased significantly, as has our understanding of the limitations of this technology. You will find the full report located on our website at:

http://www.quartzdyne.com/pdfs/CktRelPaper.PDF

Quartzdyne Product Reliability

Since 1994, we have maintained a database containing information on transducer returns. We record the specific failure mode and elapsed time since shipment for each transducer. Since in-house component screening, design qualification, long-term product testing, and transducer calibration typically identify the major failure modes in our transducers, field returns rarely reveal new or unexpected failures. Every year, we analyze the database for trends, and share the results openly on our webpage. This report describes the general design of a Quartzdyne^® Pressure Transducer, and provides the reliability statistics and common failure modes for each of the major components, based on field-failure returns.

It is rare to find a company that publicizes their failures (albeit our failure rates are low.) However, we consider this an important part of continuous improvement. We hope that our customers appreciate our candor and honesty, as well as our ongoing efforts to improve the reliability of our products. This year's report is found at the following link:

Transient Performance

Accurate and precise pressure measurements require in-situ temperature compensation. Since Quartzdyne^® Pressure Transducers are calibrated under static conditions, a temperature difference between the pressure crystal and the temperature crystal results in a pressure measurement error. We've selected a crystallographic orientation for our pressure crystal that minimizes the transient error for most downhole work. In formation evaluation applications, rapid drawdown or buildup events cause adiabatic (PV) heating of the oil surrounding the pressure crystal. Depending upon the severity of the event, several minutes may be required to equilibrate the temperature fully throughout the metalwork and quartz.

Since 1999, we've significantly improved the transient response of our 1-inch transducers by better coupling the pressure and temperature crystals, and by minimizing the effect of the PV heating in the oil surrounding our pressure crystal. Similar improvements have now been made to our smaller transducer models (0.88 and 0.75 inch.) A technote showing the head-to-head transient competition between our downhole models is presently available on our website. The report shows essentially similar transient performance in 0.75", 0.88", 1.00" transducers. As always, final transient performance will be influenced by the metalwork you add to the transducer.

http://www.quartzdyne.com/pdfs/tran.pdf

Q-Link: Digital Transducer Interface

Quartzdyne is pleased to announce the pre-CE release version of the Q-Link digital transducer interface. The Q-Link serves as an RS-232 serial interface between a computer and up to four Quartzdyne digital transducers (Series DM and Series DS.) Customers familiar with our Series I will appreciate that the Q-Link employs the same protocol and command set as the Series I, allowing for a trivial switchover. Moreover, Q-Link firmware is upgradeable through website downloads. CE compliance is expected by May 2003. A specification sheet is now available on our website at:

Paired with the Q-Link, Series DS pressure transducers eliminate the need for the 1-to-1 "Series I -- Series QS" combination; customers who connect more than one DS transducer to a system will quickly realize the Q-Link value at $695. We encourage our Series QS customers to evaluate the Q-Link and Series DS specifications. Effective May 1, the QS will no longer be available for new purchases. The DS has several advantages over the QS: smaller size, Inconel 625 wetted parts, and digital signaling (longer transmission lengths.)

Diaphragm Isolation Transducer

Since 1991, we've offered Inconel 625 bellows isolation to protect the crystalline quartz pressure sensor from gas, brine, and other corrosive fluids. The bellows has made an impressive contribution to the long-term reliability of our transducers, particularly in high concentrations of H₂S and CO₂. A bellows should be protected from particles, however, because mud, sand, and asphaltines can inhibit smooth bellows movement. In subsea applications, wax and hydrate crystal formation serve as further incentives to find a bellows substitute.

Over the past two years, Quartzdyne has developed a flush-diaphragm-isolated transducer. The Inconel 625 diaphragm-isolated pressure housing provides excellent corrosion resistance, and the flush surface will not trap particulates. Maintaining accuracy and stability was critical during development; these performance attributes were not compromised by the design. We've qualified the diaphragm for pressures up to 16,000 psia [1100 bar] over a -40°C to 177°C temperature range. The 1.25 inch diameter makes this transducer a strong candidate for subsea wellhead applications, as well as for fluid phases behavior (PVT) analysis.

The diaphragm isolation transducer (P/N DMD301) is now listed in our website product selector at:

http://www.quartzdyne.com/spec/product.htm

Visit Quartzdyne at OTC

We invite you to visit Quartzdyne during the OTC Conference and Exhibition in Houston between May 5-8 in booth 4235. Please contact us at sales@quartzdyne.com if you would like a complimentary daypass. We look forward to meeting you, and learning more about your application requirements.

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