Welding purge dam with apertured purge plates

1. A water-degradable welding purge dam apparatus for purging a weld zone of a pipe assembly comprising first and second pipes having respective first and second pipe ends to be welded together at a root gap, said purge dam apparatus comprising:

a blocking plate assembly having an outer blocking plate, an inner blocking plate, and zero or more interior blocking plates;

said blocking plate assembly comprising one or more water degradable materials to facilitate removal of said purge dam apparatus from said pipe assembly using an aqueous fluid following welding; and

at least one of said blocking plates comprising a plurality of fluid flow apertures formed in a pattern to aid distribution of said aqueous fluid through said blocking plate assembly.

2. The purge dam apparatus of claim 1 , wherein there are first and second ones of said blocking plate assembly that are ganged together by an interconnection assembly to provide a ganged set of spaced-apart air flow blocking plate assemblies, said interconnection assembly comprising one or more water degradable materials to further facilitate removal of said purge dam apparatus from said pipe assembly.

3. The purge dam apparatus of claim 1 , wherein said blocking plate assembly comprises at least one pair of blocking plates in mutual facing engagement with each other, each blocking plate of said blocking plate pair having a plurality said fluid flow apertures.

4. The purge dam apparatus of claim 3 , wherein at least some of said fluid flow apertures in respective ones of said blocking plates in said blocking plate pair are partially laterally overlapping relative to each other.

5. The purge dam apparatus of claim 3 , wherein at least some of said fluid flow apertures in respective ones of said blocking plates in said blocking plate pair are fully laterally misaligned relative to each other.

6. The purge dam apparatus of claim 1 , wherein each said blocking plate assembly comprises two or more pairs of blocking plates in mutual facing engagement with each other, each blocking plate of said two or more blocking plate pairs having a plurality said fluid flow apertures.

7. The purge dam apparatus of claim 6 , wherein at least some of said fluid flow apertures in blocking plates that are not part of the same blocking plate pair are partially laterally aligned relative to each other.

8. The purge dam apparatus of claim 6 , wherein at least some of said fluid flow apertures in blocking plates that are not part of the same blocking plate pair are fully laterally aligned relative to each other.

9. The purge dam apparatus of claim 1 , wherein said blocking plate assembly includes at least one interior blocking plate having said fluid flow apertures, and wherein said outer blocking plate and said inner blocking plate do not include said fluid flow apertures.

10. The purge dam apparatus of claim 2 , wherein said interconnection assembly comprises an interconnection structure having a wall surrounding a hollow interior.

11. The purge dam apparatus of claim 10 , wherein said interconnection structure wall comprises a plurality of fluid flow apertures to aid distribution of said aqueous fluid from said hollow interior to an exterior region outside said interconnection structure wall.

12. The purge dam apparatus of claim 2 , wherein said interconnection assembly comprises first and second interconnection structures that interconnect said blocking plate assemblies.

13. The purge dam apparatus of claim 12 , wherein said second interconnection structure surrounds said first interconnection structure.

14. The purge dam apparatus of claim 13 , wherein said first and second interconnection structures each comprise a wall surrounding a hollow interior, and one or both of said first and second interconnection structure wall comprise a plurality of fluid flow apertures to aid distribution of said aqueous fluid from said hollow interior to an exterior region outside said interconnection structure wall.

15. The purge dam apparatus of claim 1 , wherein said blocking plate assembly comprises at least one friction plate having a plurality of flexible sidewall members on its periphery adapted to flexibly engage an inside wall of one of said first or second pipe ends.

16. The purge dam apparatus of claim 15 , wherein said flexible members comprise flexible tabs defined by slits in said disk periphery.

17. The purge dam apparatus of claim 16 , wherein said blocking plate assembly comprises one or more support plates stacked on one or both sides of said friction plate.

18. The purge dam apparatus of claim 17 , wherein said one or more support plates have a periphery that is aligned with a base of said friction plate flexible tabs.

19. A weld zone purging installation, comprising:

a pipe assembly comprising first and second pipes having respective first and second pipe ends to be welded together at a root gap;

a water-degradable purge dam apparatus disposed in each of said first and second pipes proximate to said first and second pipe ends to define a weld zone spanning said root gap;

said water-degradable purge dam apparatus, comprising:

a blocking plate assembly having an outer blocking plate, an inner blocking plate and zero or more interior blocking plates;

said blocking plate assembly comprising one or more water degradable materials to facilitate removal of said purge dam apparatus from said pipe assembly using an aqueous fluid following welding; and

at least one of said blocking plates comprising a plurality of fluid flow apertures formed in a pattern to aid distribution of said aqueous fluid through said blocking plate assembly.

20. A water-degradable welding purge dam apparatus for purging a weld zone of a pipe assembly comprising first and second pipes having respective first and second pipe ends to be welded together at a root gap, said purge dam apparatus comprising:

a ganged set of spaced-apart air flow blocking plate assemblies;

each blocking plate assembly having an outer blocking plate, an inner blocking plate and zero or more interior blocking plates;

said blocking plate assemblies being ganged together by an interconnection assembly that interconnects said blocking plate assemblies;

said blocking plate assemblies and said interconnection assembly comprising one or more water degradable materials to facilitate removal of said purge dam apparatus from said pipe assembly using an aqueous fluid following welding;

at least one of said blocking plates comprising a plurality of fluid flow apertures to aid distribution of said aqueous fluid through said blocking plate assemblies;

each said blocking plate assembly comprising at least one pair of blocking plates in mutual facing engagement with each other, each blocking plate of said blocking plate pair having a plurality said fluid flow apertures;

some or all of said fluid flow apertures in respective ones of said blocking plates in said blocking plate pair being at partially laterally overlapping relative to each other;

said interconnection assembly comprising an interconnection structure having a wall surrounding a hollow interior, said interconnection structure wall comprising a plurality of fluid flow apertures to aid distribution of said aqueous fluid from said hollow interior to an exterior region outside said interconnection structure wall;

each said blocking plate assembly comprising at least one friction plate having a plurality of flexible sidewall members on its periphery adapted to flexibly engage an inside wall of one of said first or second pipe ends; and

said flexible members comprising flexible tabs defined by slits in said disk periphery.