Best pipe thread type to use in harsh conditions

minnow

I have a project where we need to install a 4” Sch 40 pipe in a vessel with harsh chemical (caustic) conditions (inside and out). To make the pipe removable for maintenance, we need to build in a threaded connection in the 4” pipe.

There is concern about using a fine thread which may be sensitive to the conditions and become stuck and we would like to suggest a chunkier, more robust thread. Has anybody such experience or can recommend a certain thread?

A 3” NPT thread was the original suggestion from our contractor.

Many thanks.

T5180

Why is it essential to use a thread ? a flanged joint is far superior on diameters above 1/2" or 1".

lau1247

What sort of pressure are you looking at? I'm assuming you are looking at threaded connection because you want to avoid welding on end connections?

I agree, npt is not great in general.

Have you look at hub and clamp connection? The likes of grayloc hub (there are other manufacturer out there) may be suitable for what you need.

minnow

T5180 wrote: »

Why is it essential to use a thread ? a flanged joint is far superior on diameters above 1/2" or 1".

I should have mentioned, it needs to pass through a restriction, so must be flush, or as close as possible. No room for a flange.

minnow

lau1247 wrote: »

What sort of pressure are you looking at? I'm assuming you are looking at threaded connection because you want to avoid welding on end connections?

I agree, npt is not great in general.

Have you look at hub and clamp connection? The likes of grayloc hub (there are other manufacturer out there) may be suitable for what you need.

The issue is that it will be installed through a restriction which requires the pipe to be flush.