A recent article in Chemical Processing by Dave Joseph of Emerson Process Management highlights the costly leak detection problem experienced by the Fujifilm chemical plant in Dayton, Tenn which was solved through the use of pH analysis. (To read the complete article, Click HERE.)
The site, which makes photosensitive chemicals, feeds dry materials and flammable solvents, including thionyl chloride (SOCl2), to a reactor used to precipitate crystals. The volatile solvent is pulled from the reactor and routed through a heat exchanger using a liquid ring vacuum pump. Unfortunately, SOCl2 produces hydrochloric acid when it comes into contact with moisture. When acid from the process got past the pump’s seal, it damaged the pump. In the last three years, the $28,000 pump was replaced multiple times due to corrosion.
Three alternatives could prevent the problem: using exotic materials of construction; installing an intermediate tank to capture vapor (not possible in the available space); or analyzing the seal fluid to detect leaks before they caused damage. Opting for a simple analysis system was the proverbial “no-brainer.”
Leak detection can be performed using either pH or conductivity analysis. The choice depends on the process. For pH to be used, a small amount of contaminant must cause a measurable change in the pH of the process; for conductivity to be suitable, the contaminant must significantly alter the conductivity. Conductivity can detect leaks of acids, bases or even salts but requires stable process conductivity for best results.
The chemicals to be monitored by Fujifilm affected pH. So, the plant installed a pH analyzer in the vacuum pump seal loop (see image below). It chose a wireless unit to obviate power and output wiring. Because a wireless gateway was already in place for other process control applications, implementing the analyzer was easy. It was incorporated into a self-organizing network that allows each device to function as a data repeater. Thus, if any pathway becomes interrupted, data automatically travels via an alternative pathway, assuring uptime. The pH monitoring system cost less than $3,500 to implement and was up and running in two days.
Since the plant installed the pH analyzer in June 2011, it hasn’t suffered any corrosion-related pump failures.
In the Fujifilm application, the normal pH of the seal fluid (water) is approximately 7; at that point, corrosion is minimized. To protect the vacuum pump seal integrity, when the analyzer finds the pH has dropped below 3, the process is stopped and the system is flushed to clear out the acid and return the process pH to 7.
The Fujifilm application is an excellent example of appropriate use of pH-based leak detection because when the process pH is near neutral (7.0) the pH response is greater, resulting in increased sensitivity to detect leaks. In general, however, pH may respond differently to the presence of contaminant, depending upon the process pH and the chemistry involved. To learn more about the use of pH analysis in a range of applications, Click HERE.
The need to monitor fuel burning efficiency and emissions is common to many industries and nowhere is this more relevant than in marine applications. For one South Korean shipbuilding and marine engineering company, Daewoo Shipbuilding & Marine Engineering (DSME), continuous emission monitoring solution (CEMS) equipment from Emerson Process Management, Rosemount Analytical has allowed it to improve the operational performance of its floating production, storage and offloading (FPSO) vessels, meet regulatory requirements and perform real-time emissions monitoring of its exhaust gases.
With rising energy costs, maritime companies work hard to monitor the flow of fuel in ships, FPSOs and other sea-faring vessels. Equally important is assuring the efficiency of the burning process. Thus, the installation of a CEMS allows the operator to monitor the emissions of the fuels being burned by the vessels. This information helps determine the need for scrubbers to reduce CO2, NOx and SO2, which may be required to meet international maritime standards.
The FPSO CEMS provided is a system which is custom-engineered for the analysis of samples taken from four different streams. As the samples from these streams are laden with moisture, due consideration has to be taken to ensure all sample stream components are kept in the same gaseous phase. Hence, all sample streams are heated from the sample take-off points and also kept hot to prevent unwanted condensates in the AISI 904L sample tubings. A sample conditioning system is used to properly condition the sample to suit each separate analysis by different analyzers. The sample system is also designed to ensure quick response to the change of samples taken from each sample point. The sample conditioning system and analyzers are housed in an IP65 weatherproof CEMS enclosure made of 316SS material. A PLC (programmable logic controller) is also used to execute certain functions within the sample conditioning systems. An on-demand request to the PLC will activate the pneumatic blowback, typical of CEMS that handle particulate content which may clog the filter at the sample take-off point. This is also implemented within the design of the sample conditioning system to clean the filter at the sample take-off point. The electrical components of this whole system are required to meet the requirements of ATEX Zone 1, Gas Group IIA.
While other technologies may be used in on-shore plants, the space limitations in a tightly knitted FPSO mean that the use of CEMS is more appropriate. In most cases CEMS allows the user to be able to have the dry basis measurement, not on a wet basis. In addition, the analyzers used for CEMS do not require air conditioning as other technologies do since they are designed to be suitable for up to 50oC ambient temperatures. Air conditioning takes space and generates heat and the need to meet ATEX certification means a more expensive type of air-conditioning system is used. The simplicity and reliability of this self-contained CEMS makes it an ideal choice for these demanding marine applications where the FPSO is deployed.