Q1 - Is 304L piping typically used for cryogenic applications i.e. transporting liquid nitrogen?

a) Could you be more specific? Are you referring to bulk transport, or just piping from bulk storage?

Now this is a tank:

http://www.uigi.com/featured_liquid_tanks.html

Here are some specs for Cryogenic Liquid Trailer Specifications
LOX/ LIN/ LAR:

http://www.uigi.com/trailers.html

Here's an Overview of Cryogenic Air Separation
and Liquefier Systems:

http://www.uigi.com/cryodist.html

b) These folks use 304  for Vacuum Jacketed Pipe (VJP) but, I don't know for sure if it's a low carbon grade or not (L)...

http://www.vjpipe.com/pdf_files/QC_Technical_Manual.pdf

http://www.midwestcryo.com/VJPmanual.pdf

https://www.chart-ind.com/app_csd_vip_mvip.cfm

https://www.chart-ind.com/litfiles/13490803.pdf

http://www.cryofab.com/html/stand_4.htm

http://www.technifab.com/products/vacuum_jacketed_piping/rigid_vjp/index.html

Here's some technical information on 304 SS piping used for cryogenic applications:

http://www.sandmeyersteel.com/304.html

Here's typical specification for cryogenic piping design/materials where the use of 304SS of the piping and associated parts is specified along with some other materials but primarily 304 SS:

https://dcc.ligo.org/public/0025/E1000713/001/Spec%20for%20Piping%20Design_Materials%20E1000713_v1.pdf

Here's a not so typical transition joint made up of both 5083 Aluminum and 304L SS for special applications:

http://www.asahi-kasei.co.jp/baclad/en/product/ccj.html

Here's an overview of the various, most common types of cryogenic piping systems used today:

http://www.process-cooling.com/Articles/Feature_Article/0d3f8c5f4b5b7010VgnVCM100000f932a8c0____

Just to expand your mind a bit, here's an interesting short course on the Introduction to Cryogenic Engineering:

http://www.slac.stanford.edu/econf/C0605091/present/CERN.PDF

Here's some good info from the folks who fabricated some critical components for the NIF otherwise know as the National Ignition Facility at Lawrence Livermore National Labs:

http://www.mtm-inc.com/reduce_project_risk/toughness_testing_and_asme_b313_process_piping_code/

Here's the award they got from NIF/LLNL:

http://www.mtm-inc.com/news/meyer_tool_receives_award_from_lawrence_livermore_laboratory/

Finally, here's an interesting application:

http://www.doeal.gov/SWEIS/DOEDocuments/076%20cryogenicdrilling_2.pdf

Q2 - We have ASME IX WPS qualified for 316L to 316L pipe using 316L consumable.  I am looking to use this WPS to weld 304L to 304L as 304L and 316L has the same P number Group number as per ASME IX...

I would pass that question up to the EOR (Engineer Of Record) first for approval.

Q3 - Is it common practice to weld 304L to 304L using 316L consumable?

Not really... It is common that a 308L filler is used when welding 304 or 304L SS. However, i have on occasion seen 316L used but I don't remember any code requirements for use on 304 pipe... Then again I'm retired and I'm getting old and forgetting alot these days so forgive me if I'm not as current as some would like me to be.

Anywho, that's my two cents worth... Hope this is helpful.

Respectfully,
Henry

You have to keep in mind that carbon is an austenite stabilizer and as such when you use low carbon fillers you are going to experience higher ferrite content. This is the very thing you do not want in cryo service due to ferrites' proclivity to a ductile to brittle transition.
But its 304L base metal you say?
Base metal is different. Given the manner of its processing it will still be fully austenitic at room temp.
I would suggest you consult a filler metal supplier that deals with austenitics intended for cryo, i.e., no ferrite. My preference is Euroweld.

In order to get their degree, engineering students at Mackenzie Presbyterian University in Sao Paulo are required to prepare what we call a TGI, i.e., a monography about a certain engineering subject that they choose freely. The TGI must be done under the supervision of a professor, who is called the Counselor.
Years ago, one of my pupils, Miss Gabriela Tiemi Hattori, decided to prepare her TGI putting up a piping specification for liquid nitrogen, and invited me to be her counselor, which I promptly accepted. Her TGI deserved 10 points, the maximum that can be obtained.

TGIs are not protected by copyrights and their content is open to whoever wants to use them, so I'm not infringing any right nor patent if I let you know the materials of construction that were selected by Miss Hattori. Her specification is 4 pages long, so I'll reproduce here just the most important parts of it.

Service: Liquid nitrogen
Temperature: minus 102 to minus 196 Celsius
Pressure: 20 bar

Base material for pipe: AISI 304
Surface finishing: 125 - 250 RMS
Corrosion allowance: zero
PWHT: not required
Inspection Class III
Base material for valves: AISI 316

Pipe material
1/2 to 2 inches: ASTM A312 Tp 304 seamless, Sch 40S
2.1/2 to 24 inches: ASTM A312 Tp 304, EFW, Sch 10S

Fittings (all)
1/2 to 2 inches: ASTM A182 Gr F304, class 3000, socket weld ends
2.1/2 to 24 inches: ASTM A403 Gr WP304, EFW, Sch 10S, butt weld ends

Flanges
1/2 to 2 inches: ASTM A 182 Gr F304, serie 300, Raised Face, socket weld ends
2.1/2 to 24 inches: ASTM A 182 Gr F304, serie 300, Raised Face, welding neck

Valves (all)
1/2 to 2 inches: body ASTM A182 Gr F316, trim AISI 316, raising stem, socket weld ends
2.1/2 to 24 inches: body ASTM A351 Gr CF8M, trim AISI 316, raising stem, flanged ends

Gaskets (all)
Flexitallic, AISI 304 with graphite filling, carbon steel outer ring, serie 300

All pipe shop and field welding procedures, as well as welders, to be qualified with impact test for low temperature service according to paragraph 323 of ASME B31.3. Impact test temperature to be the minimum temperature of this specification.

After obtaining her degree, Miss Hattori applied for a job in the Piping Department of a well known Brazilian engineering company. Along with her resume, she sent her specification. She was inmediately hired.

Giovanni S. Crisi
Sao Paulo - Brazil

What is your definition of "cryogenic""? You should quote your minimum metal design temperature. What process and which consumable do you to propose to use? Quoting 316L is insufficient information. 304L base material should be no problem. Choice of welding consumable is.

Hi Firefly

I think you have your answers, but maybe I can give my opinion in a slightly briefer manner:

Q1 - Absolutely, along with Al alloys 304L and 316L are the materials of choice for cryogenic applications. 304L is usually used rather than 316L, because the higher price of the 316L is not warrented. (Pitting will not be an issue at those low temperatures.) The only exception will be where the pipe is in a marine environment, and may be exposed to periods out of service, where pitting may become an issue.

Q2 - Theoretically there is no problem using the 316L consumable. ASME IX allows it, and it will perform just as well joining 304L to 304L as joining 316L to 316L. After the dilution effects of the base materials are taken into account, you will find that the weld deposit is hardly different. The only issue here is that many company specifications will not allow you to use a WPS for 304L, which is backed by a PQR qualified on 316L base metal. (Just make sure this is not the case.)

Regards
Niekie