RE: check valve

From: <Lakshmi>
Date: Thu Oct 30 2003 - 03:45:00 EST


Thank you Mr Steve McKenzie for reply.
Regards
Lakshmi Narayana

-----Original Message-----
From: Steve McKenzie [mailto:Mechproj@xtra.co.nz] Sent: Thursday, October 30, 2003 10:31 AM To: <a href="/group/PipingDesign/post?postID=twTFqMAyRwKJ4b8swH5FHLynG_aF8mm_ApTe4r7cAeMyAyOCvUnR0CyPvAMAqWGDM44onXQzc4xb7y56KwjTMY2-0YU">PipingDesign@yahoogroups.com</a> Subject: RE: [PipingDesign] check valve

The ball type check valve is less likely to jam up than other types because it has only loose guideways; no hinges or pins. Also there is less danger of seat damage due to material sticking to a face. This is because the ball presents an infinite number of sealing faces, and its shape provides a degree of self cleaning action at the seating circle. For liquids containing grit or uncertain corrosives, they can be a good choice. Ball checks, and derivatives ( Y valves) are almost exclusively in slurry check valve service for these reasons;hardly anything else lasts. A similar arrangement is often used for compressed air traps. The balls are normally elastomeric coated to aid sealing.
They are more expensive, however, owing to the larger body size, and the cost of the ball.
If the "oily water" contains grit or corrosives (both common in oily water) then a ball check would possibly be my first choice. I have pulled out a lot of wafer checks with frozen spindle bushes and broken springs; this cannot happen with ball checks. The humble swing check works well (if it has a swivel pin and externally lubricated bushes in dirty service), and is often overlooked because it is more expensive than a wafer check. If the liquid is clean and non-corrosive, the extra cost of a ball check is probably not justified.

Cheers

Steve McKenzie

-----Original Message-----
From: Paul Bowers [mailto:pbowers@pipingdesign.com] Sent: Thursday, October 30, 2003 6:13 PM To: <a href="/group/PipingDesign/post?postID=twTFqMAyRwKJ4b8swH5FHLynG_aF8mm_ApTe4r7cAeMyAyOCvUnR0CyPvAMAqWGDM44onXQzc4xb7y56KwjTMY2-0YU">PipingDesign@yahoogroups.com</a> Subject: Re: [PipingDesign] check valve

Ball checks are similar to globe valves in layout in the sense that the flow tends to be up and over (or around) rather than a "straight-through" pattern that wafer checks have. This would seem to result in more turbulence and higher pressure drop.

My experience in refineries that were built 60+ years ago indicates that at that time there were limited alternatives as to check valve choices and wafers don't exist in the original specs. Same goes for high-performance butterfly valves.

If you are unsure, consult an expert for the intended fluid and pressure application.

If you are diverting from original plant specs and rely on supplier recommendations, I STRONGLY suggest that you check out the supplier.

In the past, stuff has blown up because products looked good (for the price) but actually were non-code. We don't want to kill anybody here.

Paul

> It is availble with the vendor that he can supply rightaway.enough space
is
> avialable. wafer is replaced with ball type. pressure loss is very less.
>
> regards
> lakshmi narayana
>
> -----Original Message-----
> From: rajendra bajikar [mailto:rajendrabajikar@yahoo.com]
> Sent: Wednesday, October 29, 2003 8:40 AM
> To: <a href="/group/PipingDesign/post?postID=twTFqMAyRwKJ4b8swH5FHLynG_aF8mm_ApTe4r7cAeMyAyOCvUnR0CyPvAMAqWGDM44onXQzc4xb7y56KwjTMY2-0YU">PipingDesign@yahoogroups.com</a>
> Subject: Re: [PipingDesign] check valve
>
>
> The Non Return Valve, whatever type you use, is to prevent back flow. You
> may want to check out the pressure losses between the two, if it is
critical
> in any way. You have not mentioned the reason for this change.
> Regards,
>
> "Lakshmi V. Narayana" <LNarayana@safco.net> wrote:
>
> Dear friends,
>
> Instead of wafer type check valve(PTFE lined),PTFE ball type check valve
is
> being used for oily water service (3"NB) pressure 4KG/cm2 temp 44C . is
> there any negative impact in doing so. can anybody throw some light on
this
> .
>
> Regards
> LAKSHMINARAYAN
 > MECHANICAL ENGINEER
 > SAFCO


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Discussion List sponsor: The fluid flow calculations website - www.LMNOeng.com - LMNO Engineering, Research, and Software, Ltd.

Information presented on this list is given as helpful advice, nonsense, carefully-considered calulation or any combination of the above. The intent is to spark discussion and encourage knowledge-sharing amongst professionals. If you blow yourself up by doing stuff remotely described by info gleaned from reading this list, you are an idiot.

Your use of Yahoo! Groups is subject to <a href="http://docs.yahoo.com/info/terms/">http://docs.yahoo.com/info/terms/</a> Received on Thu Oct 30 03:45:00 2003

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