PRESSURE VESSSEL ESPHERIC USITEN 375

Current process and current problems experiencing??????

A) In computer messages ALL CAPITALS is SHOUTING. just so you know.

B) You have not given enough information. What type of welding? Are you pre heating? What rod, flux, filler, shield gas are you using? are you post(after) heating?

C) What type of weld inspection(s) are you using and is this during or post weld?

D) Has the base metal been checked by a metallurgist to verify it is correct and up to specification?

I'm a novice to welding (learning GTAW/TIG/Heliarc welding) so sounds like you will need to do a lot of research before you pressurize these tanks or risk disaster.

Brad

thanks

we are welding whit E7018 and we have WPS and PQR`S.

we are doing a preheat at 95ºc before start the welding process but we don`t do post heat . the temperature in this zone of country is around 45ªC until 49ºc at peak time.

we do visual inspection, radiographic inspection, and some times ultrasonic inspection and the plate was verified by our people because we have in our team metallurgical engineers. (The plate is according whit especifications)

in especific the crack appear in:

1.-a joint between plates in ecuador zone. the crack have 1 until 2 inch lenght

2.-the join between the nozzle and hemisphere plate, and the crack appear charged to neck of the nozzle and this was produced after the post weald heat treatment.in this point of wels is neccesary PWHT because according ASME (the nozzle have 14" of diameter and have a reinforcing pad).

the PWHT is done in according ASME CODE UCS 56,

if you need more information to can help us whit your comments please let me know

GABRIEL

From my experience, I think that there is a problem related with preheating and inter-pass heating. That thicker base metal need to be preheated. Also, very important for doing intermediate heating (between every two passes, unless the material not reached the required temp.). And you have to check and measure the temp. of the base metal before welding and between passes.

Also, it is very important while proceeding a PWHT for any part (not the whole vessel) to heat the area around and adjacent the portion where you doing the PWHT to control the rate of heating and cooling from that area and the areas around. Rapid cooling or heating will affect the mechanical properties of the material such as tensile, hardness and elongation and can cause cracking.

In addition to the following questions: Did you used:

1. A weld metal match with the base metal?

2. Qualified WPS's and PQR's?

3. Apply a PWHT in the qualified WPS's & PQR's?

4. E7018 in a heated condition as manufacturer's recommendation?

5. E7018 in uphill direction?

6. And many many questions related to joint design, welding parameters (volt, amp.& speed), attendance of a qualified inspector, ... etc.

Does your material come with documentation? If this is an isolated case, you may conceder removing as section in the affected area and send it to be analysed. You may have a bad mill run creating problems.