16-08-2017, 12:44 PM
I had something like this on a project last year.
The P-way contractor wanted the equipment cases out the way in good time so they could use nights for pre-work before the main commissioning. The TOCs would not accept even weekend blockades to do the migration. We were left with 10 overnights (3 blocks of fri/sat/sun) each just a few hours. These are some points from my experience related to the stageworks approach:
*There is a risk that any one of those nights might overrun - many stages higher risk;
*There is a greater risk with short possessions that they could be lost altogether - we lost one because late running trains at the end of the evening meant that handover was to late to start work. Once this happens the whole sequence is at risk.
* The new equipment room needs to be able to run all the existing railway and all the new layout - it may be costly to provide any additional space, equipment and power to run today's railway from the new location, and then abolish it a few weeks later.
* there is greater complexity in the design; all the stage states have to be fully considered and planned before the first design starts.
* Potentially the existing railway is to legacy standards and if you're doing stageworks you have to resolve how to have a new equipment room to new standards running legacy railway equipment safely.
* sequential design stages take longer to design, check and approve. Both in hours spent and in timescale. It cannot be done in a shorter time by putting more designers on the job. If you can't keep the same designer(s) on every stage of the design then there could be a mis-understanding and significant incompatibility somewhere.
* There is usually a necessity for overlapping design i.e. the next stage's design is begun before the previous had been commissioned. Overlapping design means there is a risk changes to one stage are not correctly carried forward.
* if the new equipment room is relocatable (portacabin style, not brick-built) it would be possible to build and wire everything internally and fully pre-test off site. This significantly reduces the workload on commissioning for testers. This is easier if the location only has the final state to test, hard to impossible to use this method to pre-test significant stageworks.
The P-way contractor wanted the equipment cases out the way in good time so they could use nights for pre-work before the main commissioning. The TOCs would not accept even weekend blockades to do the migration. We were left with 10 overnights (3 blocks of fri/sat/sun) each just a few hours. These are some points from my experience related to the stageworks approach:
*There is a risk that any one of those nights might overrun - many stages higher risk;
*There is a greater risk with short possessions that they could be lost altogether - we lost one because late running trains at the end of the evening meant that handover was to late to start work. Once this happens the whole sequence is at risk.
* The new equipment room needs to be able to run all the existing railway and all the new layout - it may be costly to provide any additional space, equipment and power to run today's railway from the new location, and then abolish it a few weeks later.
* there is greater complexity in the design; all the stage states have to be fully considered and planned before the first design starts.
* Potentially the existing railway is to legacy standards and if you're doing stageworks you have to resolve how to have a new equipment room to new standards running legacy railway equipment safely.
* sequential design stages take longer to design, check and approve. Both in hours spent and in timescale. It cannot be done in a shorter time by putting more designers on the job. If you can't keep the same designer(s) on every stage of the design then there could be a mis-understanding and significant incompatibility somewhere.
* There is usually a necessity for overlapping design i.e. the next stage's design is begun before the previous had been commissioned. Overlapping design means there is a risk changes to one stage are not correctly carried forward.
* if the new equipment room is relocatable (portacabin style, not brick-built) it would be possible to build and wire everything internally and fully pre-test off site. This significantly reduces the workload on commissioning for testers. This is easier if the location only has the final state to test, hard to impossible to use this method to pre-test significant stageworks.