化學儲存監測

在最近的訪問中，在新的聯合循環發電廠進行了化學儲存應用上的若幹級變送器，我們有機會與EPC公司，工廠人員和化學品供應商合作。這提供了一種有趣的外觀，從工程角度來看，從工程角度來看，以及從日常運營的角度來看。

Ammonia, Acid and Caustic Chemical Storage

Although important measurements, the ammonia, acid and caustic storage tanks are not difficult level applications for Magnetrol^®和orion instruments.^®任何伸展。然而，我們發現，關於應用程序如何相對於技術監測的細微差別可以對所用儀器類型的日常實用性和可靠性具有急劇效果。此外，在補充這些化學品時存在安全注意事項，這可以通過對儀表包的一些簡單，經濟有效的修改實現一些簡單，經濟有效的修改來同時解決。

These chemical storage tanks can be horizontal or vertical vessels six to ten feet in diameter/height, with the ammonia storage tank usually the largest of the three. It is not uncommon to see some type of non-contact level transmitter (Ultrasonic being the most prevalent) installed to provide level indication to the control room with a local display at the base of the tank, either in series with the 4-20 mA transmitter output or repeated from the control room. The signal to the control room tracks inventory, acts as a high alarm for overfill protection and establishes the resupply interval. The local display facilitates monitoring the offload of chemicals from the supplier’s truck.

There are a number of level technologies you could throw at these applications. Our preference is Through-Air (Non-Contact) Radar or Guided Wave (Contact) Radar on the acid and caustic tanks and the latter for the ammonia storage. This doesn’t imply non-contact Ultrasonic Level transmitters or other technologies are not up to the task. Simply put, radar is indifferent to the changes in the contents of the vapor space of these vessels occurring throughout the course of the day. Oftentimes, these changes affect the Ultrasonic burst causing what we refer to as a nuisance alarm, e.g., it loses the signal intermittently or the level indication becomes erratic only to recover about the time a technician arrives on the scene. These types of issues are difficult to isolate since they are intermittent and not linked to an installation or configuration anomaly or hard fault in the instrument. If a competitively priced technology that does not require calibration and is unaffected by changing process conditions is available, we would take that path. Radar meets these three criteria.

Performance Perspectives from the I&C Team

在評估過程中與I＆C技術人員和化學品的討論局限於電平變送器的可靠性，遠程指示和性能驗證。在所有三個罐上，沿著磁電平指示器（MLI）的線路都是優選的獨立視覺指示。從技術人員的角度來看，它允許輕鬆驗證水平變送器的性能，並在任何原因出現發射機退出傭金時添加一層冗餘。我們對我們的儀器有很多信心擊中了大門的標記，但我們必須承認在初次調試後對閱讀有第二次意見是很好的。粘貼這些坦克通常不是正常操作期間的選項。

產品轉移期間的級別儀表可讀性

專注於readabi化工供應商的見解lity during the transfer of product from the truck to the tank. Even though he normally offloads a fixed quantity of material which the vessel should accommodate based on level indications prior to dispatch, knowing the level during the transfer process is a safety measure to prevent overfilling. His comment was that MLIs can be read easily from a distance with the occasional glance while managing other tasks, whereas, he had to be on top of an LCD-type display to monitor progress. This was particularly important when working with the ammonia storage tank.

頂部填充時的考慮因素

值得指出的一項值，這將簡化儀器的調試是頂部填充管道在較小的酸和苛性罐上的儀器安裝噴嘴附近。由於非接觸技術在這些應用上普遍存在，因此依賴於突出垂直於測量材料表麵的圓形或橢圓形信號占地麵積，從而將儀器噴嘴定位在遠離產生的湍流，而頂部填充是理想的。此外，如此緊密的接近允許作為化學物流進入容器以與透射光束相互作用的噴射圖案，這可能導致填充過程中的信號丟失，使供應商盲目地向血管中的剩餘空間盲目。隨著時間和耐心，調整儀器的配置可以克服這種障礙。在壁邊，在船隻的設計階段分離這兩個入口點將消除任何潛在的問題，而不增加成本或擴展調試時間。本發明的噴嘴/填充線配置是另一個點來爭論MLI的情況或選擇導向波雷達技術，以消除發射器附近的任何潛在的幹擾和過度湍流。

在調查各自申請和訪問I＆C部門和化學品供應商後，我們審查了工程團隊的各種選擇。我們的合作產生了三種選擇，可以提高可靠性並增強儀表包的日常功能。

Another benefit to this approach is more flexibility in the instrument nozzle mounting location relative to the vessel top fill piping arrangement. The Guided Wave Radar is a contact measurement whose sensing element can ignore turbulence and the chemical spray pattern previously mentioned. This added benefit not only simplifies commissioning of the instrument but separates the measurement from the tank dynamics for improved reliability.

Lastly, we looked at including some of the “wish list” items the I&C technician and chemical supplier noted and added a visual indicator (Orion Instruments Atlas™ or Aurora^®models) for level verification, redundant and diverse measurement technologies and improved readability during normal plant operation. This approach does add cost to the instrumentation package even when taking into account the elimination of peripheral items included in a minimal installation. Aside from the ammonia storage tanks, which traditionally have the process connections in place to accommodate an externally mounted device, adding similar process connections to the acid and caustic tanks would bump up the cost of the vessel as well. In the grand scheme of things, the additional costs are minor compared to the long-term benefit, but it is something that needs to be taken into consideration for chemical storage monitoring.