Ball Check vs Piston Check Valve

[alamin]

Hi,

I have got a plethora of questions regarding these valves. Can the forum members enlighten me

(1) For what type of applications and fluid media these types of NRV for more suitable?
(2) Is it preferable to use a ball check than a piston check for the fact that piston check relies on spring force for closure and may loose its resiliency in course of time?
(3) Is it true that a ball check will experience less erosion than a piston check due to the fact that ball check has almost a point contact to its seat when used in a dust-laden gas or corrosive liquid media?
(4) Does either type work equally well in vertical and horizontal orientation? For gaseous and liquid media?
(5) Do they have any specific advantage over swing check valve or pinch valve?
(6) Does ball check give tighter seal than piston check?
(7) Is dP normally higher for a piston check than a ball check valve?
(8) Please tell me any other prominent features / advantages of these two types of check valves that I haven't mentioned above.

Cheers,
Amin

 

[sterl]

1) Virtually all types of spring loaded Check Valves are going to be somewhat prone to P-A cycling (chattering) based on the same (change in area exposed to upstream pressure upon first crack) as a blowdown PRV, just in samller proportion..>So they tend to pop open and reseat at a characteristic frequency, which if it aligns or corresponds with a superimposed pressure cycle, will cause the valve to chatter. This will make them unsuitable for certain types of pulsing flows, and many pumps and compressors, even screws and scrolls, create pressure pulsations at some frequency or another. This movement of the valve's internals can certainly amplify the pulsation, create noise and increase wear on the valve's moving parts. In come case the spring itself is broken by the high count of stress cycles or mislodging from its intended containment or alignment.

2) There are a multitude of versions for Piston Type check valves...Some have an inherent dashpot effect...They are therefore not as prone to the pressure cycles and are harder to damage in that fashion. They may be slow reacting. Many have s singular "correct" orientation, for instance they have to be mounted at a specific 12 to 6 on a horizontal pipe. Many of them do not have great turndown, that is they work well at 20 to 120% of nominal flow; then run out of "headroom" in capacity terms; or at low flows or low frequency pressure cycles may start "seat bouncing" much like the chattering spring loaded check...

Throttling type check valves are largely piston types, and can be designed to attenuate the effects of accelerating flows, including localized vaporization and "water hammer". Certain styles of diaphagm valves can also be designed to attenuate flow transitions and many, as a bonus, can act to protect piping against inadvertent pressurisation due to "locked liquid expansion" and similar.

3) Swing gates, offset bifolds, dual hinged, dashpot effected, and even bimetallic countersprung and a variety of other designs tend to address Slow opening problem as well as pulsation effects.

4) None of above means much if the seating mechanism and materials don't work consistently, or are subject to corrosion or erosion or impingement damage by fluid or contaminants in otherwise tolerable concentrations...

Hope this helps: The valve guys have tons and tons of literature focused on what works good where, though you kind of have to read between the lines in their more "generic" catalog material...A lot of the good stuff is only in their IOM Manuals.