DIGITAL METERING | CONDITION MONITORING
ANSI 1½”
ANSI 2½”
ANSI 3½”
Far left: No changes to panels: one size fi ts all adapter plates
Left: PNP-X is one of the more popular universal display options
ANSI 4” ANSI 4½”
recycle and if so at what price? The present estimated net cost for a Class 1E replacement analog meter is more than $15,000 each with a delivery lead time of perhaps 28 weeks. Considering the “loaded” cost (including procurement, storage, insurance, cost of idle $, overheads, and so on) an additional 20% is typical of the inventory. With 640 meters of perhaps $15,000 plus another $3,000 of load factor the inventory for meters alone could run to more than $10m with inflation a further factor to account for over the next 20 years. The corresponding cost of spares inventory for the PNP
version of meters would consist of one PNP-2 display/ controller, one PNP-V display/controller, one plug-in loop power input-signal converter module, one of each optional Control Output plug-in module and one each of the 250 different “sticky” scale plates for the displays. Meanwhile for the transmitters spares would be one 4-20 mA current loop transmitter (PNP-D or -P or -X or a combination), one each of every plug-in module for the 20 different input signals, and one each of the plug-in power input module. The total estimated cost of PNP spares here is less than $25,000. In addition, the average meter life expectancy for an
analog meter is around 10-15years whereas the digital unit might run for 40 years or more. There are other benefits too. Accuracy and resolution for analog meters is around 2% (depending on operator parallax) whereas for digital it is closer to 0.05% and there is no possibility of parallax errors occurring.
The estimated cost of digital modernization with PNP
for some 640 current loop transmitters (Din Rail or Panel Mount) to EPRI 102323-rev4 standard for every signal input listed at about $4,000 each is around $2.56m A further 445 PNP-2 (which replaces VMI 9222) and 180
PNP-V (which replaces the VMI 9223) EPRI grade display/ controller at $4,000 each is a further $1.78m for a total of around $4.34m One spare for each of the PNP-2, PNP-V, three different power supply modules, 20 different input signal conditioner modules, each control output modules (as listed) and 250 different adhesive scale plates at $25,000 leads to a total one-time investment of $5,145,000 or about 60% of the cost of just maintaining the analog meter I&C for the next 20 years.
Scaling instrumentation It’s estimated that American NPPs have about 8,200 discontinued VMI 9221, 9222 and 9223 in use today. The only
way they can be replaced is if the old meters are recycled and rebuilt, since the demand doesn’t justify the investment to build new ones from scratch. This is an issue that is only going to become more challenging as times passes. Instead, copying D’Arsonval’s “one movement” analog
meter invention of the 1800s, but utilising modern technology, eliminated the mechanical movement and achieved a simplicity of design. The PNP “one movement” display (Patent # 10,222405)
only accepts bipolar, single ended or differential 0.5V DC signal input and 3-5.5V DC power input. In other words, all PNP displays/controllers have identical inputs/outputs regardless of size or shape, and all displays accept the self- adhesive scale plate that is placed on the front of the filter. Any display can be used for any application. All offered (and custom) signal and power input options are converted to the “one movement” either at the 4-20 mA current loop transmitter or inside the housing of the display, or at the HUB that converts them to the required “one movement” (+/- 0.5V DC full scale signal and 3-5.5V DC power). The HUB is used to convert any and all existing panel cut outs (if the selected PNP housing fits in existing space) using the available (or custom) adapter plates to mount the selected PNP display/controller in an existing panel space without retooling the panel. The Plug and Play (PNP) acronym is used because it’s
truly a plug-and-play design, no changes are required to present panel mounting as long as the case selected will fit within the space and no changes are needed to existing wiring for signal/power or existing signals. PNP technology represents the natural evolution of the
nuclear instrumentation and control room. Improvements in accuracy, reliability, and efficiency have allowed digitalization to overtake analog instrumentation in the 21st century control room, and it is now time to add cost- effectiveness to that list. Such technology can not only improve the performance of I&C room instruments but can also effectively address economic concerns over spares inventory by reducing the number of spares necessary, from hundreds down to a single spare instrument. And it can do it without any disruption to whatever surrounding panels or wiring may be in place. ■
Right: This type of scale recording device can help minimise spares inventory
www.neimagazine.com | August 2022 | 31
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45
