The Pipeline Shock Prevention People
Pump Start-up surge, Valve closure shock, Pump shutdown back flow bang.
Large vessels for high pressures with matching bladders, diaphragms, gas bags, and bellows, for over a third of a century.
ShockGuard Ltd. offer shock alleviators. | Please phone 44(0) 161-480-9625
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This 3.222 Hz. major frequency plot is formed by a continuous fluctuation at 29 Hz. which is be seen by magnification.
HOW DOES THIS HAPPEN?
A common occurrence is, for a natural wave speed frequency of one of the lengths of pipe to reflect or "return", the pressure wave to the pump at a frequency which coincides with the frequency at which the pump shaft will defect, or bend, or move slightly in its bearings, so that vibration then begins.
The small shaft movement, changes the distance from the impellers to the housing, and pressure fluctuations result. The fluctuations are amplified by the returning waves. Very soon the pipe system is suffering from heavy pulsation.
1. Reservoir 2. Centrifugal Pump
Click on the WaveGuard for detailed pages
The answer is to decouple the pump from the pipe, "Acoustically" with a
PULSEGUARD Ltd/ Inc.
WAVEGUARD, a no moving parts pulsation dampener.
|Visit LIQUID DYNAMICS Intl. Ltd. LDi offers analytical and modeling services. They predict these and similar problems, before pipe systems are built. When you pipes already exist, it is less expensive to install a WAVEGUARD than to stand the cost of acoustic diagnostics, analysis and modeling.|
PRESSURE COMPENSATION FOR VOLUME EXPANSION
Where block valves shut a volume in a pipe that may be subject to temperature change and where a relief valve piped back to source is not safe or practical, Flexorber or Liquibello volume compensators are used.
The LIQUIBELLO Metal Bellows Replaceable bellows capsule.
FLEXORBER LP with PTFE Diaphragm from FLEXFLON or virgin Teflon (El DuPont)
A QUICK ESTIMATE OF THE VOLUME OF COMPENSATOR NEEDED
|1. "dV" ration The volumetric expansion of the liquid over application temperature range: (This figure is found from the difference in SG Specific gravity at the lowest temp, to SG at the highest temp)
Example: Liquid has a density of 1.013 at 5 Degrees C. and density 0.98 at 150 Deg, C. The valve for volumetric expansion is 1.013 minus 0.98 - 0.033 (3.3%)
|2. "V" The volume of liquid locked in between the clock valves. *||
|3. Pressure max "Pm". Generally less than the max pipe design pressure.||
|4. "dP" Maximum allowable level of pressure change to be applied.||
|The equation has assumed an isothermal pressure change for the suction gas compression or expansion which is of course absolutely incorrect. However the pipeline itself expands and contracts with temperature hereby accommodating some of the expansion or contraction volume. This is being used here as an offset, to save having to make an adiabatic calculation - to simplify the example for you.
An accurate calculation can be made with the gas laws: where n=0.3
The coefficient of expansion for the pipe material will of course then also have to be used to reduce the volume selected, because of the volume change due to pipe expansion or contraction.
Explanations - Understanding Frequencies / How shock and surge prevention works
|Visit LIQUID DYNAMICS Intl. Ltd. LDi offers analytical and modeling services. They predict these and similar problems, before pipe systems are built. ShockGuard is a licensed run time user of the LDi Ltd. software, ShockView. ShockView enables us to quickly and accurately run your proposed piping system, in our computers and you what the maximum level of pump start up surge, or shutdown shock will be.|
Understanding Pipeline Surge / Shock Alleviators
Shock-Guard.com / ShockGuard.co.uk Shock Alleviators