Re: Hydrotest vent and drain

From: <mechengr1977>
Date: Thu Nov 14 2002 - 22:22:00 EST

Loosening the bolt on large bore dia pipe and then tightening it back again is not easy compared to opening the vent valve or plug. plus u run the risk of cold working the gasket. Makes it worse if the flange joint is connected to a valve. its a pain if the location is high.

• In PipingDesign@y..., zope_tushar@f... wrote:
  > In my opinion High point vents and drains are required only if
  there is no
  > flange joint at the highest elevation in the piping (in the run).
  >
  

  ---

two problems.
not all spool fab at shop are flanged, some are butt welded (usch as cryo and hp steam).

purpose of hydrotest is to check for leak prior to s/u. No matter how many spool with flange joint you test at the shop, at the end of the day u will still end up with a joint or two that has to be done at site since u need to tie-in the piping to a piece of equipment, control valves, etc.

its always a good practice to install a vent at high point and drain at low point. note that the drain and vent will probably be use again during the plant turnaround or the running maintenance in case a repair or mods has to be done on the pipe.

Moreover these are required only if the lines are going tobe hydratested
> after the installation. Shop tested spools or piping does need not
these.
>
> Generally there will be a max. size mentioned in the project spec.
(e.g.
> 26") etc above which all lines will be shop tested.
>
> This is because, the operating weight and the hydrotest weight of
the
> piping. Supporting structure of the big lines will have to be
designed for
> hydrotest loads. It means extra money. hence these lines are shop
tested.
>
> -Tushar
>
>
>
>
>
> PipingDesign@y... AT SMTP
> Sent by: Robert" <robert.liu@u.../ "Liu AT SMTP
> 11/14/02 12:48 AM
>
>
> To: PipingDesign@y... AT SMTP@ccMTA-sgsinmx001
> cc: (bcc: Zope Tushar/fwsg)
> Subject: [PipingDesign] Hydrotest vent and drain
>
>
>
>
> Dear members;
>
> Is it true that vent and drain are needed at every high and low
> point of
> piping if water is used for hydrotest? what if air or steam are
used?
>
> Can someone explain the general procure about how to use them
> in the
> hydrotest?
>
> I know these question seems too junior but I do have confusion
> on it. your
> response is appreciated.
>
> Thanks
> Robert Liu
>
>
>
>
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Received on Thu Nov 14 22:22:00 2002