LPG drain system 2

[garciaf]

My issued is the following.
I got the following configuration. see athachment
Is a lpg installation. spherical tank.

I want to know what are the specifications of this valve and according what standart apply to this valve.
These valves are threaded at both ends?
or welded, according what standard.
Please I need your help.
Thanks for your knowlegde.

 

[BigInch]

You need to supply more information. You have not said much about many, very important aspects of the design.
Piping design code?
Piping material?
Min Max Temperature?
Max Pressure?
Pipe Size?
Where is this drain going?

 

[MikeHalloran]

LPG tanks are not usually provided with a bottom port.
What are you trying to do?


Mike Halloran
Pembroke Pines, FL, USA

 

[garciaf]

ASME B31.3
A333 GR.6
1 INCH DIAMETER
THIS CONNECTION IS A DRAINAGE OF THIS SPHERICAL TANK HOW I SHOW IN THE IMAGE PRESENTED BEFORE.


LPG SPERICAL TANK
DESING PRESSURE 264.7 PSIA
DESING TEMPERATURE 51.7 CELCIUS

 

[BigInch]

One inch could easily be threaded, however the high and low temperatures that it is exposed to may tend to loosen threaded connections. I would weld.

 

[MikeHalloran]

WLPGA.ORG publishes a
"Guide to Good Industry Practices for Bulk LP Gas Installations".
Section 5.3 talks about drains.

I have no idea if your AHJ invokes wlpga or other standards.


Mike Halloran
Pembroke Pines, FL, USA

 

[georgeverghese]

Valves in all flammable fluid service should be flanged or socket welded in my experience, not threaded. Given this is LPG, lower design temp (at MAWP) for drain line and valves should be approx -40degC.

 

[MJCronin]

Is anyone else on these fora getting a little frightened about now ??

http://www.slideshare.net/mohitnayal98/the-mexico-city-explosion-of-1984

Before we answer any more questions ....... Tell us where this tank farm will be located ???

MJCronin
Sr. Process Engineer

 

[georgeverghese]

If this is a small dia drain line, to reduce the risk of external corrosion due to constant icing from leaky drain valves ( in the future), may be better to construct this small bore line in all SS316L or 2205 duplex SS with lower design temp of -40degC - duplex SS may have to be impact tested.

You say upper design temp of the sphere is 52degC; what about lower design temp? How was lower design temp estimated?

 

[chicopee]

If threaded use schedule 80 piping; if welded use schedule 40. Get a copy of NFPA 58 for LPG systems, it will give you all the details necessary.

 

[garciaf]

Thanks for your help to all of you.

I was reading API 2510, someone told me about that standard

8.2.2 Piping Joints
8.2.2.1 The number of joints of any type between the vessel
and the Þrst block valve shall be minimized.
8.2.2.2 Welded joints shall be used where practical.
8.2.2.3 The number of ßanged joints shall be minimized.
8.2.2.4 Joints in pipe NPS 2 or larger shall be welded or
ßanged.
8.2.2.5 Joints in pipe smaller than NPS 2 shall be socketwelded,
butt-welded, or ßanged.
8.2.2.6 Piping gaskets shall be of the self-centering or con-
Þned type and shall be resistant to LPG.
8.2.2.7 Threaded connections shall be minmized to the
extent practicable and shall be between NPS 3/4 and NPS
11/2, inclusive.
Note: Threaded connections are typically used for connections such
as instrumentation and specialty devices and are downstream of a
block valve.

what do you think about this?

the first valve is a plug valve LF2 and the second one is gate valve LCB.
the minimum temperature is -20 celcius

 

[BigInch]

Like I said a while ago, weld it, unless you have very good reason not to.
Welding appears to comply with the API.

Two valves would be OK, since you would probably want to use the plug valve when attempting to regulate flow whenever the gate valve is open.

 

[chicopee]

I doubt that it is a drain line in the sense that a drain line is to remove condensate from water vapor. The line shown in the picture of the OP is either a vapor or liquid inlet or outlet to the tank. To control moisture in LPG tanks, there will be an auxiliary tank piped into the bulk storage tank in which methanol is introduced.