New at PipingDesign.com: 18 July 2000

<a href="http://www.PipingDesign.com/software1.html">http://www.PipingDesign.com/software1.html</a>

CAD Viewer and Markup Software
Cimmetry

Free Downloadable Relief Valve Sizing Software Mercer Valve Company Inc.
(Thanks to John Breen for the link)

PipingOffice
Microsoft Excel 97-Compatible Spreadsheets for Process Piping Calculations (Now linked from the Software page- let me know if the random image transition effect is too cheesy)

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Eng-Tips Forum
Technical support forums and mutual help system for engineering professionals

<a href="http://www.PipingDesign.com/manualvalves.html">http://www.PipingDesign.com/manualvalves.html</a>

Dynamic Flow Testing of Check Valves
Utah State University

<<The two objectives of this paper are: (1) to present a test method by
which check valves can be dynamically tested for sudden closure due to reverse flow; and (2) to discuss the valve and pipe characteristics which affect the reverse velocities and pressure surges at the check valves . The information developed from the test method can then be used to predict the resulting upstream and downstream transients or pressure surges caused by a check valve closure for a given piping system and flow deceleration. It should be possible to apply the following test method for the field testing of check valves that are already in use. Flow deceleration is calculated from the piping system and flow change due to pump shutdown or closure of a control valve. The test method of this paper produces a relationship between the flow deceleration and the reverse velocity at which the check valve closes. The reverse velocity is then used to calculate the pressure surge from transient equations and methods found in publications such as Hydraulics of Pipelines by J. Paul Tullis and Fluid Transients by Wylie and Streeter. The test method can be used for most types of check valves, as long as they are un-dampened and in a full open position when the flow deceleration begins.>>

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Venturi Principle
Drinking Water & Backflow Prevention

Atmospheric Vacuum Breaker Operation
Drinking Water & Backflow Prevention

<<The purpose of the atmospheric vacuum breaker is to prevent a siphon from
allowing a contaminant or pollutant into the potable water system. This plumbing system safety valve is considered protection from high hazard or toxic substances, and may be used for low-hazard materials as well. There are three flow conditions for the atmospheric vacuum breaker. The user obtains water by opening a valve to the potable supply allowing water to flow through the device. The user will then close the potable water supply and the device will drain. Finally, if a siphon or loss of pressure occurs in the supply piping, the inlet valve will open allowing atmosphere into the outlet piping to prevent a reversal of flow or "backsiphonage" to the potable supply.>>

Cross-Connection Control (Backflow Prevention) University of Southern California

<<The term backflow means any unwanted flow of used or non-potable water or
substance from any domestic, industrial or institutional piping system into the pure, potable water distribution system. The direction of flow under these conditions is in the reverse direction from that intended by the system and normally assumed by the owner of the system. Backflow may be caused by numerous specific conditions; but, basically the reverse pressure gradient may be due to either a loss of pressure in the supply main called backsiphonage, or by the flow from a customer's pressurized system through an unprotected cross-connection, which is called backpressure. Thus the term backflow covers both a backsiphonage condition and a backpressure condition. A reversal of flow in a distribution main--or in the customer's system--can be created by any change of system pressure wherein the pressure at the supply point becomes lower than the pressure at the point of use. When this happens in an unprotected situation the water at the point of use will be siphoned back into the system; thus, potentially polluting or contaminating the remainder of the customer's system. It is also possible that the contaminated or polluted water could continue to backflow into the public distribution system. The point at which it is possible for a non-potable substance to come in contact with the potable drinking water system is called a cross-connection. To prevent backflow from occurring at the point of a cross-connection a backflow prevention assembly must be installed. However, it is important the backflow prevention assembly match the particular hydraulic conditions at that location and is suitable to protect against the degree of hazard present. The particular type of backflow preventer appropriate for specific needs will be discussed later. First, it is necessary to understand some basic hydraulics which govern the principles of backflow and cross-connection control.>>

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Controlling Vessels and Tanks
Hydrocarbon Processing

<<Controlling a vessel should be a very simple matter - they don't really do
anything! But then, if they don't do anything, why are there so many of them? And why do they have so many different names? Going through a typical set of piping and instrumentation diagrams (P&IDs), you find the following vessels: [...]. Although each of these is essentially a simple vessel or tank without any special internal structure, each serves a different purpose. Once the purpose and functions of a piece of equipment are understood, it will be clear how to control and protect it. Different purposes require different controls.>> Received on Tue Jul 18 15:32:00 2000