Pressure testing, disinfection and flushing pipelines

[JohnWeal]

Good morning,

We have several pipelines of lengths up to 25 km and vary from 700 to 1600 mm diameter.

Is it acceptable to pressure test between the section into valves which are spaced approx 2km apart? It is a lot of water and I am not sure if it acceptable to reuse this same water for testing the next section of pipeline to save removing the water and bringing in more fresh test water.
I am not sure whether spectacle blinds can be fitted and how they are fitted.

Regards
John

 

[racookpe1978]

Well, spectacle flanges would have to be inserted at flange points, not underground well joints.
Each time you break up the pipeline into test sections (to save water ?) you require many hundred of man-hours and travel time to isolate, fill, vent, and test each section; then have to repeat all of that time to vent, drain, verify empty, re-isolate the broken flanges and re-torque the bolts; then go to the next section and repeat.

It is the cost and time to do each section (to isolate, fill, vent, test, vent, drain, and re-connect) that makes a longer test less expensive.

 

[rconner]

For any unfamiliar with testing of particularly large pipelines, this can be a complex subject with much to consider. Helpful guidance is contained in some standards and publications e.g. ANSI/AWWA C600, AWWA Manual M41, and several pages of guidance are provided also in European Standard EN 805.
As to testing "into" (against?) valves, while I suspect this has been done many times over the years in many places, I believe the latter publication directs that pressure tests instead be conducted with intermediate line valves open. While I may not know all reasons for this, I do know that required pressure test levels on some projects are quite high, can be above the seat pressure rating on valves employed, and I would think noone wants leakage due to excessive pressure by valve seats to cause a problem in a pressure test. As to testing blanks or bulkheads, quite large forces come to bear in testing of particularly large pipelines, and care must be taken to ensure that any caps or temporary blanking fittings etc. are adequately anchored when lines are filled and said pressure is applied. As to test water, I think it is also not unusual for test water to be re-used on large jobs with means of by-passing etc. provided from section to section etc. around an isolation/test boundary; however, where the line is to eventually provide potable water eventual/proper disinfection should probably be kept in mind in the process. Also, if one is testing against valve seats, with back-pressure used to limit differential pressure to some arguably safe level on the test side, there best be water on the backside to do that.

 

[brimmer]

Yes, you can easily test 2km sections, this would be considered a very short distance in the pipeline transmission world, I have seen test sections over 100km. The limitation is really if you have elevation change, as test pressure changes when you do, and what kind of test pressure you want (and maximum operating pressure you want in the end). I don't imagine you would have any issues with a 2km section. Re-using water is a common practice if water is expensive / hard to source / hard to dispose off, typically for new pipeline construction, though perhaps more tedious. You will probably want to treat the water if it is not potable from a municipal source.