LPG Pipe Work

Grease...I assume you mean pipe dope, which is not grease. First of all, be sure and choose the pipe joint chemical to match air, water, potable water or chemical product that will be in your pipes. I am not aware of any code that requires pipe dope and tape together.

The only screeding I know is making the top surface of concrete even with forms, so do you mean laying the pipe on top of the concrete after screeding, or laying it in the excess concrete off to one side of the forms in the pile of concrete that has been screeded off the top??

Any chance of future leakage will depend on several things, were the pipes joined good? Your psi test will answer that. Then will the pipes be protected from exterior forces so the pipes will not move when vehicles, foot traffic, or other forces are applied onto or into the medium holding the pipes? If yes, then leakage should not occur.

There is always a chance that the pipe will leak, though it can be minimised by good engineering practice, which means following the end Client's piping specifications to the letter. So start with the temperature and pressure of the LNG inside the pipe; what are they?

'Dear Sir'

This idea is not recommended, the pipe cannot be guaranteed to remain leak free due to joint problems over time or corrosion both internal and external occurring. There is also risk of stressing due to the relative temperatures of slab and pipe which will not help the problem of joint integrity over time. Any subsequent leak will tend to track along the pipe and appear at one end or the other, this can pose a real fire/explosion risk if there is then a build-up in an unventilated space.

Given the small diameter of the service I would opt for soft copper with the PVC sleeving which comes in rolls of up to 50m and therefore would be entirely free fro joints within the slab, unless you exceed that length.

Please also think of whether your pipe will have to cross any construction joints as these also pose an issue in terms of movement.

Massey.