First thoughts More information required. Is the pipe really 5km long? Start & end in different locations or does the pipe follow a 'circular' route so it isn't actually 5km away? What is the flow rate? What arrangements are there for retaining the pipe contents at the open end? What are the pipe connections in between - flanges or pipe unions or coninuous welded/extruded pipe? If the pipe is km long what other areas does it run through - other factory/process areas? Public areas? WHat happens if there is a leak part way along the pipe? Are there any particularly vulnerable areas along the route? If there is a leak part way along, can the acid react with anything/damage anything? If 5km, from end to end, how will you communicate between each end of the pipe and people involved. As ever conduct a HAZID exercise of the proposed task and then forumlate your risk assessment and control measures.

The tubing is actually coiled up and will be hanging from a bracket of sorts. We are still in the process of buying in the pump unit but the flow rate will be relative to 100 bar pressure forcing a liquid through a 3mm tube. I do believe it will be a passive operation as there will be no obstructions throughout the tube and the other end will be open. There will be no other persons in the area as it will be carried out in a test unit and the 20% concentration of acid will be added from outside the unit. I don't foresee any serious issues with the operation, but I was curious to hear from anyone who may have conducted this operation before. Thanks for your replies anyway. Regards Dave