Implications with having two gas supplies in one building

[bacon_sandwich]

Just starting on a project that involves installing a new gas supply U40 2 inch job but the client already has a very old u16 supply which is piped from a remote meter box and underground steel pipe. The pipework cannot deal with the increase in demand required (quite frankly its not really up to the current demand) and as the existing pipework is basically scrap. I have a quote to put the new supply right up to the building considerably shortening the run at 21mbar.
However i may or may not de-commission the old pipework , client wants to keep the old set up as well as having a new one.
Anybody know the rules wrt multiple supplies to industrial buildings and how do we deal with isolation etc
thx

 

[bacon_sandwich]

Pressure is off, client has accepted U65. He looses a car parking space but otherwise all good. Existing U16 set up will be de-commisioned, which was my preferred option anyway. The existing U16 was too small for all loads on at the same time, pressure was way too high and it was one of those installations where your immediate reaction was jesus who let this one through the net.......lol