Archive: Mar 2018
Used to restrict fluid flow to a certain direction, check valves are employed in the vast majority of industrial processes. At DFT® Inc., we provide a wide range of check valves for use in diverse industrial applications. Our spring-assisted in-line check valves, for instance, are specifically designed to prevent water hammer by eliminating the risk of reverse flow. And, if sizing is done to account for flow rather than line size, these high-performance valves will operate reliably and efficiently for years, without the need for extensive maintenance.
In-Line Check Valves
The experts at DFT® often help clients assess their unique check valve requirements; our check valve sizing program allows us to easily determine required valve sizes before actual setup, eliminating the risk of design errors and delays. DFT® check valves can be installed in-line in any orientation; valve operation will not be hampered in any way by the specific orientation chosen, provided the flow direction is in line with the valve design (as indicated by an arrow on the valve casting).
However, for a downward flow, these check valves need to be modified slightly to support the additional weight of the disc and any static head that may be involved. While silent check valves can be employed in vertical piping or in installations requiring constant controllable pressure, swing valves should only be used in horizontal pipe runs, in which minor flow variations are expected.
When using swing check valves, users are afforded limited pressure control, as there is less control over valve opening and closing. Therefore, this type of valve is usually employed in less sensitive, large-scale pipelines carrying liquids, gases, or steam. To allow for enhanced performance, these swing check valves can be replaced by our GLC® Silent Check Valves or Excalibur® Silent Check Valves. These silent check valves have only one moving part and allow for greater flow variability than a conventional style swing check valve. Also, because the DFT Axial Flow Check Valves have so few moving components, they are more resistant to wear and tear and can maintain a longer lifespan.
However, the GLC® model is not considered a “dead-end” service valve. It is essential that the upstream, or seat end, of the valve be connected to the line until the pressure is relieved from the downstream end. The seat end of the valve must always remain bolted to the mating flange when the valve is exposed to downstream pressure in order to avoid possible blowout of the internals, as the retaining screws do not account for direct exposure to downstream pressure. In addition to eliminating water hammer, appropriately sized silent check valves can greatly improve system safety, protect critical system components like pumps, and improve overall system life while reducing maintenance costs.
DFT® check valves are specially designed to improve the efficiency and safety of your industrial processes, and our team of experts is ready to assist in identifying the ideal model for your specific needs.
To learn more about our valve solutions, and why it may be beneficial to replace your current valves with DFT® non-slam check valves, download our new eBook, “Non-Slam Check Valves vs. Swing Check Valves.”
In our latest webinar, we provide an engaging, informative overview of steam condensate and its critical role in industry today. The webinar includes a short history of steam condensate, some of the most common problems that arise when utilizing it, solutions to those problems, and a survey of its many modern applications.
The History of Steam Condensate
The history section of our webinar discusses the origins of steam research, beginning with Thomas Savery, who invented the first steam engine in England at the end of the 17th century. He developed and patented it for use in pumping wells in 1698. Thomas Newcomen would later refine that invention in 1712, adding water tanks and pump rods so that deeper water mines could be accessed with steam power. In 1778, James Watt further built on these discoveries, employing a gearing system that allowed a steam engine to drive a flywheel in order to produce rotational power, spurring the development of the steam locomotive. These inventions, all originating in England, would become the catalyst for the Industrial Revolution and shape the world as we know it today, with steam power playing an instrumental role in a wide range of industries — including mining, chemical processing, petroleum production, textiles, pulp and paper production, and, most importantly, power generation.
The Basics of Steam Condensate
The webinar then describes the basics of steam condensate, answering the question: Why steam? The main advantages of steam stem from its high efficiency and ease of transportation and control, which make it an ideal medium for heat transfer. Steam power is easy to create due to the abundance of water and wide range of heating options available; simply by managing the temperature and pressure of steam, it can be used for much of the work that powers the industrial world. The three biggest users of stream power today are the power generation, pulp and paper manufacturing, and chemical processing industries; in these sectors, steam is used for all manner of jobs, including automation, dilution, fractionation, quenching, mechanical drive, and stripping.
Common Issues With Steam Condensate
There are some challenges involved in using steam condensate, however. For instance, it’s important to maintain high-quality steam in order to prevent a variety of pipe and valve issues, as low-quality steam can reduce heat-transfer efficiency by as much as 65%. Also, if CO2 combines with steam condensate, the formation of carbonic acid and CO2 gas may occur, which can cause rapid corrosion. Luckily, this can be managed through the use of steam traps, which keep water separated from the steam. Engineers and plant managers must also consider the line sizing of pipes in order to prevent condensate collection, as well as the location and configuration of equipment, the insulation methods used, and the types and quality of different valves used for different applications.
Steam Condensate Q&A
- Q: Do you propose using traps for all piping loops with low points in offsite piping?
- A: Yes. The condensate must be removed from the lines in order to prevent water hammer or corrosion of the piping itself.
- Q: Can you share some guidelines for specifying cracking pressure? Is there a tool one can use?
- A: It’s best to work with directly a manufacturer to pinpoint the best low cracking pressure options for your specific application. In-line (silent) check valves typically have a cracking pressure of approximately 0.5 psi. Depending on the condensate return piping layout, a standard cracking pressure (CP) valve may allow excess condensate to accumulate. In these scenarios, a lower CP is ideal; options will vary from manufacturer to manufacturer. At DFT, we offer solutions that allow for a CP as low as 0.1 psi.
- Q: Are there any formulas or tables available for steam pipe sizing?
- A: We recommend the reference handbook, “Crane Technical Paper No. 410.”
- Q: Are low cracking pressure check valves only necessary in certain types of steam systems?
- A: Low cracking pressure valves should be used for condensate return lines, not main steam lines. Also, low CP valves will help reduce the accumulated condensate in return lines.
All of these matters and more are discussed in our comprehensive online webinar and its accompanying slides. To learn more about steam condensate, view DFT’s prerecorded webinar today.