August 2006
Volume XII, Number 8
Safety-Valve Availability

How to Achieve High Safety-Valve Availability
Employing Automated Partial-Stroke Testing Systems
If plant managers could be sure that safety valves would be available 99.999 percent of the time when called on, they could eliminate a lot of stress from their work lives. However, five-nines reliability is not a reality in most plant environments, so the stress persists. Fortunately, there are two pieces of good news on this front. The first is that such a high degree of certainty over safety-valve availability is attainable. The second is that availability can be attained while contributing to the processing plant's ROI.

Evolution of Ultrasonic Flow Measurement
From Poor Performer to Recognized for Custody Transfer
Ultrasonic flowmeters of various types have been in use for more than 20 years. Doppler-based technologies were the first ultrasonic systems introduced on the open market, and initial designs showed signs of promise as an alternative to traditional flow measurement technologies. Unfortunately, early-generation Doppler systems ultimately proved to be poor performing instruments, and, as a result, gave ultrasonics a rather lowly reputation among flowmeter users. Over the years, however, continuing enhancements of Doppler technology, as well as the emergence of the transit-time concept, have dramatically improved the accuracy of ultrasonic systems.

Selection Criteria for Self-Powered Thermometers
Ensuring the Accuracy of Your Temperature Measurements
There are three general types of self-powered thermometers: liquid-in-glass; bimetallic-actuated; and filled-system. Identifying the specific requirements of your temperature-measurement application will help make sure you select the appropriate self-powered thermometer for your needs.

Vortex Flowmeters Gaining Traction (Finally)
Technology Enhancements, Standardization Efforts Are Reasons for Optimism
Since vortex flowmeter technology was first introduced in the late 1960s, the number of worldwide suppliers has grown to at least 35. During this time, many technology evolutions have taken place, including anti-vibration software and electronics, multivariable meters, reduced-bore meters, plastic vortex meters, etc. As such, users now have a wide variety of choices when specifying or purchasing vortex flowmeters.

High-Level Switch vs. Transmitter
Are Improved Diagnostics & Reliability Worth the Added Cost?
Installing a level switch addresses the goals of reducing costs and only installing the minimum equipment to perform a function. After all, level switches usually cost significantly less than level transmitters, so there is a definite cost savings. However, the analysis of costs should extend beyond the costs of the instruments themselves to include their installation and operation.

Mailbag: Why Is My Water Temp. Rising?
Reader Frustrated by Pump Overheating Issues
We recently (May 2006) installed a new pump for ambient water service on a paper-cutting machine. When we operate this pump, the water temperature rises continuously. In four hours of operation, the water will reach boiling point. What is the problem?

Quiz Corner: Positive-Displacement Flowmeter Sizing
What Size Flowmeter Do You Need?
You are instructed to purchase a positive-displacement flowmeter for a liquid flowing continuously at approximately one gallon per minute (approx. four liters per minute). What size flowmeter would you purchase?