Instrumentation process fluid change

In many cases, opening and closing the vent lines must be done carefully to reduce sudden changes in pressure that could destroy the instrument. To bring the instrument back on service, for example, a secondary line may be attached to the vent line to pressurize the instrument slowly. The line may be overpressurized so that when the valve to the process line is opened, the purge fluid flows into the process instead of process fluid entering the instrument line. 

Sensor problems are often associated with the small-diameter lines that transport process fluids to the sensors. For example, the presence of solid material, ice, or bubbles in a line can result in erroneous measurements. Simple diagnostic checks can be performed to detect certain types of sensor problems. An abnormally small amount of variability in a set of consecutive measurements can indicate a dead sensor (see Section 10.3), while a break in an instrument line (e.g., a thermocouple) can be detected by a rate-of-change or noise-spike filter (see Chapter 17). 

The instrument mechanic replaced the fluid in the bubbler with glycerin. Unfortunately, the glycerin reacted with the gas, turned into nitro-glycerin, and detonated. The explosion seriously and permanently injured the employee. This dangerous accident resulted from an undetected one-minute process change of less than a quart (liter) of fluid. It appears that a lack of proper training led to this accident. 

Further investigations with boar seminal fluid performed by Kalic et al. [54] using a 600-MHz NMR instrument revealed the identification of the amino acids hypotaurine and carnitine. Semiselective HSQC 2D experiments on an 800-MHz speedometer [55] enable one to differentiate between the structurally similar polyamines, spermidine, spermine and their metabolic precursor putrescine, all attracting interest for tumor therapy, in seminal fluid. Recently, Tomlins et al. [56] studied dynamic biochemical processes in incubated human seminal fluid samples The enzymatic hydrolysis of phosphoiylcholine to choline and the conversion of uridine-5 -monophosphate to uridine were found to be very fast, whereas the slow polypeptide hydrolysis to amino acids can be inhibited by the addition of EDTA. It remains to be seen which role the biochemical changes play in the reproductive function. 

Monomer conversion in emulsion and solution polymerization can be determined via density of the reaction medium due to the difference in density between monomer and polymer. The availability of on-line digital densitometers manufactured by Anton Paar of Austria and others make this approach amenable to on-line application [23-26]. These instruments are capable of immediate determination of the density of any fluid, and, if equipped with a flow cell, can continuously monitor the density of a process stream. Results are displayed locally and can be transmitted digitally to a data acquisition computer. Density measurement is accomplished by introducing a test fluid into a glass U-shaped sample tube which is rigidly supported at the open ends. The tube is electronically excited to vibrate at its natural frequency. The frequency of oscillation is continuously monitored electronically, and from the change of frequency caused by the test fluid within the tube, the... 

Main Components of the Control System Sensors Signal is sent from the sensor to the measuring instrument by means of connecting cables or mechanical link or change in pneumatic/fluid pressure. The desired values of the process parameters are generally known or are designed in the begiiming. 

Change in facilities may also occur as a result of changes in produced fluids, process additives, product specifications, byproducts or waste products, design inventories, instrumentation and control systems, or materials of construction. Typical instances in which change in facilities would likely occur include the following ... 

---