PulseGuard Pulsation Dampeners

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PulseGuard Pulsation Dampeners
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Pulsation Dampener Pressure Safety - The "P Max" and "UM" Scandle

Beware of Pressure Vessel Codes
You rarely receive the dampener for which you think you have been quoted.
What does the manufacturers listed pressure rating actually mean?


Here are three typical expressions:

1. Maximum allowable working pressure - determined by users.
2. Design pressure - The designer, "responsible body", "engineering author" responsibility.
3. P.Max - Absolute maximum, nothing could cause a higher figure.
Unfortunately, neither 1 2 nor 3 mean the same pressure.
Even worse; not only are the meanings different, but also the meanings of each of the three expressions is different, when used by each of the 120 companies who claim to design and make pulsation dampeners.
It has been calculated that there are 96 different ratings for any one pulse dampener .


First understand "--Pressure--"

Starting with the simplest, item 3 above, "P.Max". (An EN13445 expression)

This means exactly what it says. The pressure maximum under the least stringent circumstances. No deductions from the figure to cover ANY eventuality at all.


"P Max" as per "a 87-404-EU Simple Vessels" and "UM" is the pressure for which you can apply the dampener , if you dare, when there is NO additional material for the following:
A. Relief valves requiring more then dead weight set pressure for dynamic response..
B. Relief valve requiring an additional 15% above response pressure to safely fully open.
C. Low working stress, so that the dampener does not fail due to hydraulic shock loading. Please refer to minimum estimated deductions for hydraulic shock loadings.
D. Lowering the working stress further, to allow for high cyclic duty, accelerated fatigue.
E. Recognition that users do run dampeners without cushion pre-fill. F. corrosion allowance..


"P.Max" will also probably mean that the highest working stress figure has been used, by applying the European Harmonized Pressure Vessel Code EM 13445-3:2002, method of calculation, and assuming that TUEV have seen the metal melted, poured, & tested.

All of which can mean that the dampener is less than half as strong as another that is also called the same number of --Bars, or --PSI. rated.

Therefore when specifying a dampener by its "P.Max" number, supply is on the basis that the purchaser has taken account of A through E above, and so purchaser has de-rated the dampener , for safe use, in his organization. accordingly.


"Design Pressure" Item 2 above.

When a dampener is listed by "Design Pressure", it is deliberately not saying that this is a suitable "P.Max" nor a suitable "Max Allowable Wkg. Pres" (MAWP). Design pressure does mean that the designer is working to a code, and generally means that it is being assumed that the user will want to use a lower pressure for his MAWP.
In the case of PulseGuard Dampeners, both fatigue considerations, and RV considerations, items ABC&D will be suitably addressed if the MAWP is set at 79% of design pressure. This is because PulseGuard uses low working stress figures, for example 17,000 lbs in3 when others use 20,000 to 30,000 lbs in3.


"Maximum Allowable Working Pressure" (MAWP) Item 1 above

A MAWP statement means that ABCD&E etc. have all been considered, and the appropriate ones of them, have been allowed for in determining the MAWP figure. Generally the equipment provider, does not have enough information to make the decision.



For safety in use, ISO9001, the EU "PED", OSHA, and due dillegence, it is always wise for a user to set an MAWP as 50% of "P.Max" or 79% of PulseGuard design pressure.
Never specify a static pressure vessel code (EN5500, EN13445) for a dampener , because pulsation is high cyclic duty, not static pressure duty and their WPSs acceptance test & ductility are inadequate.


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Fluid Flow Control Pulsation Dampeners