Definintion of "open to atmosphere"

[Dale00]

We have fire protection sprinkler systems on our coolant circulation pumps. Basically the sub-system has a 3” piping supply (no orifices) with 8 Nozzles. The pressure before the isolation valve is 1100 kPa (abs) with the fire pumps running, while the pressure at the nozzle would be about 1000 kPa (abs) if sprays were in-service (information from commissioning tests).
Modified piping welds were performed downstream of the isolation valves. ASME 137.3.2 is being used to justify not pressure testing the new welds by defining the pipes as “lines open to the atmosphere”.
Can theses lines be classified as “open to atmosphere”?

Note: It is possible to install blind flanges or plug the nozzles to perform a pressure test.

Also relevant is ASME III ND-6111 Scope of Pressure Testing which states;

The following portions of piping systems whose only function is to transport fluids to and from spray ponds, lakes, reservoirs, or tanks which are open to the atmosphere are exempt:
(1) piping downstream of the last isolation valve preceding the pipe discharge to the spray pond, lake, reservoir or tank; and
(2) piping upstream of the intake pump inlet isolation valve.

Fire protection standards all have testing requirements for sprinkler systems.

Thks Dale

 

[eliebl]

This probably comes down to a jurisdictional question. Where I am located those lines would be non-expansible fluid and therefore outside of the jurisdiction's authority. This would then fall on the contract spelled out between the owner and fabricator/designer. The contract would call out what the design code is to be used and therefore the inspection and testing requirements.

Personally, if the welds did leak a bit it wouldn't matter to me as the leak is small in relation to the reason the system is in operation. They would only become an issue if they completely failed and did not deliver the water to where it was required.

EJL