- Published on Sunday, 01 March 2015 23:29
- Written by Kate Kunkel
Basically everywhere you look in modern society, you see something made of concrete. Often we see trucks traveling down the road, drums spinning to keep the cargo mixing on their way to a job site in a subdivision or business park. It’s so common, in fact, that most people barely give it a second thought, but the process that turns limestone into towers of concrete and steel is one that creates its own challenges for valves in a cement plant, especially those in the slurry line.
One of the largest cement companies in the world is Lafarge, which produces cement for residential and commercial construction and for oil wells. Ed Kunkel worked for Lafarge at its plant in southwestern Ontario for more than 30 years, and he provided much of the process line and valve specification information for this article. We also spoke Ed Holtgraver of QTRCO, Inc., Tomball, TX, who provided us with additional information about valves and actuation.
- Published on Monday, 23 February 2015 10:33
- Written by David Billings
The error output from a control valve can come from a variety of sources: uncontrolled input pressure, uncontrolled input flow rate, inaccurate orifice size or turbulent flow through the system which causes irregularity of flow rates through the system. Inaccurate orifice size can result from dirt or scale in the system or from the operator having insufficient ability to set the orifice size. A common bathroom faucet, for example, is very difficult to set to an exact size due to imprecise setting mechanisms and also varying amounts of washer compression.
While progress has been made in creating valves with accurate orifice sizes, many control valves still require electronic control loops to ensure outputs are within desired limits. However, use of these electronic controls is not always practical. They can be expensive. They need regulated electricity which is not always available and which is often inconvenient to connect with. Electronic controls can also be vulnerable to damage, which not only reduces their lifespan, it reduces their reliability. They can require training to use as well. Particularly in foreign, underdeveloped markets or for some home markets, these issues can prohibit use of electronic controls for some applications.
- Published on Tuesday, 17 February 2015 11:34
- Written by Bob Cadwell, Gerry Longinetti and James Chiu
Low-temperature stainless-steel fuel shutoff valves are typically used for on/off control of fuel gas within gas fuel trains in process heating system burners. These systems are widely used by oil and gas firms as well by as original equipment manufacturers (OEMs) that produce gas heating equipment or burner management systems (BMSs) and controls in upstream oil and gas pipelines and tanks.
For valve manufacturers, these uses present a relatively specialized, rather challenging application. Environmental conditions at the point of use are often difficult. Ideally, valves should deliver reliable operation despite constraints on factors ranging from power consumption to service availability. Conversely, outdated controls can pose problems—including poor performance, noncompliance with current regulations and triggering of environmental concerns.
- Published on Monday, 19 January 2015 10:55
- Written by Terry Blevins, Kurtis Jensen and Stephen Briggs
Based on the broad acceptance of wireless transmitters, manufacturers have developed and introduced wireless actuators for on/off valves. These devices are being used to address closed loop discrete control to flush water and sand from a gas-cleaning tower and to automatically control the temperature of product storage tanks. We can expect major valve manufacturers to introduce wireless throttling valves that can be used with a wireless transmitter to implement closed loop continuous control (Figure 1).
This simple implementation can have an impact on the process industry by increasing automation and production effectiveness. While the automation may be part of the main production operation it also increases the ability to streamline auxiliary functions such as water treatment and storage operations for raw materials, intermediate materials, waste or final product.
- Published on Monday, 15 December 2014 15:42
- Written by Ed Holtgraver
Back in the “early days,” we were taught that, to properly control flow, we should select a linear valve characteristic when the valve controls more than 25% of the piping system pressure drop at full flow. We were also taught to select an equal percentage characteristic when the valve accounted for less than 25% of the pressure drop. This is an interesting guideline for sure, but many of us did not understand the rationale behind the advice. This article attempts to explain that thinking.