priya17385
Chemical
- Jul 10, 2007
- 13
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Can anybody explain me the main disadvantage of tilting Disc Check valve over a swing Check valve?
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Tilting Disc Check vs Swing Check Valve 1
- Thread starter priya17385
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tilting disc check valves are a lot smaller and lighter so for a given pipe size they don't cost as much. Since the tilting disc is partially balanced, the cracking pressure is less-Particularly for vertical upward flow. Neither will work well for vertical downward flow, and neither will be happy if they are not installed right-side up.
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The characteristics of the tilt check valve are such that the potential for waterhammer are reduced. Not as much as you would see with an annulus type non slam check valve.
What you aim for is a valve with a low mass and short travel so that is is closed before the returning pressure wave will slam it shut. The tilt check by its geometry is better than a swing check valve. the latter has been described as "agricultural at best".
Refer Fluid Transients in Pipeline Systems ARD Thorley. Also check out the Delft Laboratory site. Delft have tested check valves for dynamic performance. Als see where there are papers on surge.
Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng
What you aim for is a valve with a low mass and short travel so that is is closed before the returning pressure wave will slam it shut. The tilt check by its geometry is better than a swing check valve. the latter has been described as "agricultural at best".
Refer Fluid Transients in Pipeline Systems ARD Thorley. Also check out the Delft Laboratory site. Delft have tested check valves for dynamic performance. Als see where there are papers on surge.
Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng
Seconding what stanier said, as I recall the tilting disc is airfoiled so it goes to fully open position and stays there. A swing disc valve continually bounces around and ultimately the pin wears which mat make it hang open, leak due to misalignemnt, or the pin may even fail. If the disc goes downstream it inevitably finds something expensive to jam.
I support the replies from both JimCasey and Stanier and the descibtion that swing checks are "agricultural at best".
During the NEL valve workshop in Aberdeen (October 2005) there was an interesting paper about Maintenance, Inspection and Testing of Non-Return Valves. This paper was presented following a near accident on a British platform where 12 out of 12 swing check valves in a production line failed.
However, Priya, correct valve selection should always be based on the application. For standard non-return applications a tilting disc or dual plate check valve will do. For more critical applications (e.g. to protect expensive rotating equipment or potential risk of waterhammer) an axial or non-slam check valve type is recommended.
During the NEL valve workshop in Aberdeen (October 2005) there was an interesting paper about Maintenance, Inspection and Testing of Non-Return Valves. This paper was presented following a near accident on a British platform where 12 out of 12 swing check valves in a production line failed.
However, Priya, correct valve selection should always be based on the application. For standard non-return applications a tilting disc or dual plate check valve will do. For more critical applications (e.g. to protect expensive rotating equipment or potential risk of waterhammer) an axial or non-slam check valve type is recommended.
What I hate most about tilting disc check valves is the restricted accessibility for maintentance.
The body of a swing check valve typically is equipped with a separate flanged cover plate. This allows you to access the flapper for maintenance or to remove the flapper for line testing and flushing while the valve remains in installed condition.
Tilting disc valves, however, typically have a split body. You have to remove the entire valve body for maintenance. It is even worse where tilting disc checks valves are equipped with butt welding ends. In this case the pipping manifold has to be spread apart for maintenance. Sometimes this requires the provision of additional break flanges.
The body of a swing check valve typically is equipped with a separate flanged cover plate. This allows you to access the flapper for maintenance or to remove the flapper for line testing and flushing while the valve remains in installed condition.
Tilting disc valves, however, typically have a split body. You have to remove the entire valve body for maintenance. It is even worse where tilting disc checks valves are equipped with butt welding ends. In this case the pipping manifold has to be spread apart for maintenance. Sometimes this requires the provision of additional break flanges.
Grandnobi,
Of course if you used an annulus type non slam valve such as Noreva or Mokveld you wouldnt need to be continually taking your check valves apart for maintenance.
The prime cost of a piece of mechanical equipment may only be 12% of its whole of life cost if it is a high maintenence item. Great if you want job security in maintenance but if you are the owner and want reduced life cycle costs and plant availability avoid the swing check and the dual plate type valves.
There are two types of damage by surge. The first is obvious and something breaks. The second is the damage from repetitive events that cause fatigue failure of seals, glands, discs, seats, shafts and gaskets. When one piece of equipment finally succombs to this type of failure you are then reliant on the standby which is in a parlous state itself having been subjected to the same fatigue history.
Design the system for whole of life not the maintenance crew's career path and longevity!
Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng
Of course if you used an annulus type non slam valve such as Noreva or Mokveld you wouldnt need to be continually taking your check valves apart for maintenance.
The prime cost of a piece of mechanical equipment may only be 12% of its whole of life cost if it is a high maintenence item. Great if you want job security in maintenance but if you are the owner and want reduced life cycle costs and plant availability avoid the swing check and the dual plate type valves.
There are two types of damage by surge. The first is obvious and something breaks. The second is the damage from repetitive events that cause fatigue failure of seals, glands, discs, seats, shafts and gaskets. When one piece of equipment finally succombs to this type of failure you are then reliant on the standby which is in a parlous state itself having been subjected to the same fatigue history.
Design the system for whole of life not the maintenance crew's career path and longevity!
Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng
CWFCNuclear
Nuclear
If your velocity is not high enough to hold the disc fully open both the swing check and tilting disc valve will experinece bushing/hinge pin wear. Once difference between tilting disc and swing check is that the TD is very intolerant to any wear and will result in seat leakage. Swing checks with moderate hinge/bushing wear may still seat tightly at high DP.
If your velocity is below 10-12 fps water, expect disc oscillation for a swing or TD valve. These are ballpark numbers and differ based on the specific desings.
If your velocity is below 10-12 fps water, expect disc oscillation for a swing or TD valve. These are ballpark numbers and differ based on the specific desings.
CWFCNuclear,
Great insight of what industry already knows. Given the nuclear industry's routine documentation of failures is there a Report you can reference?
Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng
Great insight of what industry already knows. Given the nuclear industry's routine documentation of failures is there a Report you can reference?
Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng
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