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Rt1 Rt2 Rt3 Rt4 Radiography
The Pressure Vessel RT Test article provides you with information about Radiography testing in the pressure vessel manufacturing process and related items in pressure vessel inspection.
RT3 means E = 1 b. RT2 means E = 0.85 c. RT1 and RT2 may mean E = 1 d. RT4 means spot radiography. 16- You are planning for the Hydro-test of a complete vessel with Hydro test pressure 40Kg/cm2g. The calibrated test gauges available with you are 0-50 Kg/cm2g, 0-100 Kg/cm2g, 1-150 Kg/cm2g and 0-200 Kg/cm2g. Which two gauges are acceptable for. By CT and chest radiography, to better evaluate laryngeal. (rT3, rT4) or a histologically. Supracricoid partial laryngectomies were performed for rT1 and rT2 with suboptimal endoscopic.
Do you know what your pressure vessel RT test requirements are? Is full radiography mandatory for your vessel? When is full radiography mandatory? What are the acceptance criteria? What are the RT symbols?
So if you need this information, this article answers all of these questions.
We recommend that you to review this article in conjunction with the ASME Pressure Vessel Joint Efficiencies article.
Before going into the RT test, we need to know about joint categories. These categories are base on ASME Code Section VIII:
The ASME Training Course is 5 days video training course and available online and the student that successfully pass the exam, receive I4I academy certificate with 40 hours training credit.
Category A:
- All longitudinal welds in shell and nozzles.
- All welds in heads, Hemisph-head to shell weld joint
Category B:
- All circumferential welds in shell and nozzles
- Head to shell joint (other than Hemisph.)
Category C and D are flange welds and nozzle attachment welds respectively
Longitudinal weld (Category A) is more critical because it is subjected to double the stress than Circ. Weld (Category B) and this the reason in different part of the ASME code, we have stringent rules in category A joints compared to category B joints.
Pressure Vessel RT Test -When We Need to Do a Full Radiography Test?
When one of following conditions is existing, you need to do the full radiography:
- All butt welds in vessels used to contain a lethal substance
- All butt welds in vessels in which the nominal thickness exceeds specified values
- All butt welds in unfired steam boilers with design pressure > 50 psi
- All category A and D butt welds in a vessel when “Full Radiography” is optionally selected
As you see, the item numbers 1, 2 and 3 are really mandatory for a full RT test;
But pressure vessel manufacturers can make an optional decision for full radiography in item number 4
Pressure Vessel RT Test - Why do pressure vessel manufacturers want to spent more money for full radiography in item # 4?
Because the joint efficiency in the full radiography condition is 1, the higher joint efficiency in the pressure vessel wall thickness formula causes less wall thickness. The manufacturer might save lots of money with a lower thickness plate material.
But code has given some bonus to manufacturers in item 4, because it is not mandated to do full radiography in all butt welds. Manufacturers can do spot radiography in B and C joints with the same joint efficiency of item 1.
Item number 2 describes thickness limitations. Any pressure vessel material is designated to the specific P. Number by ASME section IX, so there are several tables in ASME Code Section VIII Div. 1 Subsection C, which determine this limitation.
For example, SA 516 material is P Number 1, and needs to be fully radiographed if its thickness is greater than 1.25 of an inch. At the same time, SA 204 material is P Number 3 and needs to be fully radiographed if the thickness is greater than 0.75 of an inch.
Pressure Vessel RT Test - Is Acceptance Criteria in Full Radiography or in Spot Radiography More Stringent?
Acceptance criteria for welding defects in full radiography is stringent. These criteria are stated in UW-51 and UW-52 in ASME Code Section VIII Div. 1
It means there is a defect if interpreted based on the full radiography criteria in UW-51, and it might be rejected, but if it is interpreted by the spot radiography criteria in UW-52, it might be accepted.
Pressure Vessel RT Test - What is the Important Spot Radiography Requirement?
- One spot shall be examined on each vessel for each 50 ft. increment
- For each increment of weld to be examined, a sufficient number of spot radiographs will be taken to examine the welding of each welder or welding operator
- Each spot examination will be made as soon as practicable after the completion of the increment of weld to be examined
- The location of the spot shall be chosen by the Inspector after the completion of the increment of welding to be examined
Pressure Vessel RT Test - Radiographic Personnel Qualification:
The radiographic personnel need to be certified by the pressure vessel manufacturer according to their written practice.
Holding the ASNT Radiographic certificate is not enough
In fact, SNT-TC-1A can be used as a guideline for manufacturers to establish their written practice for qualification and certification of their personnel.
Radiographic Examination Procedure and method
ASME Code Section VIII Div 1 mandates that all tests shall be done based on ASME Code Section V, article number 2.
Related Articles
Pressure Vessel Definition, ASME Code Section 8, Pressure Vessel Heads, Pressure Vessel Handbook, Spherical Pressure Vessel, Pressure Vessel Plate Material, ASME Pressure Vessel Joint Efficiencies, ASME Impact Test Requirement, Pressure Vessel Dimension Inspection,Vessel Pressure Testing, Third Party Inspection for Pressure Vessel, Inspection and Test Plan for Pressure Vessel
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Have your say about what you just read! Leave me a comment in the box below.Let us start out by briefly explaining of these terms:
Radiography test is a nondestructive testing method of inspecting some hidden cracks in the material by using radio magnetic radiation to penetrate through the materials. The purpose is to ensure structural integrity of the weld joint. As per ASME, there are four types of Radiography test (RT), i.e. RT1, RT2, RT3 and RT4.
Rt1 Rt2 Rt3 Rt4 Radiography Machine
Joint efficiency is the number used to define welded joint strength which basically depends on the RT type. This Joint efficiency plays a vital role in determining the thickness of the pressure vessel components in Mechanical calculation. For RT1 and RT2 joint efficiency is 1.0, for RT3 efficiency is 0.85 and for RT4 efficiency is 0.70.
The Weld Joint Category is how each weld on a vessel is classified to a Joint category, based on the criticality. As per ASME there are four types of weld joint categories, Category A, Category B, Category C, and Category D.
Now we can see how these three are interlinked as per ASME Sec VIII Div.1
As per ASME Sec VIII Div.1 the RT type 1 or 2 or 3 or 4 will be selected based on the type of weld joint category A or B or C or D. In turn the type of RT 1 or 2 or 3 or 4 will decide the Joint efficiency value 1.0 or 0.85 or 0.7. So this is how Radiography test, Joint efficiency and Weld Joint category are interlinked as per ASME Sec VIII Div.1.
To give an example, we have detailed the RT type with Joint efficiency based on weld category.
Category A and D butt welds shall be fully radiography (RT1) hence the Joint efficiency is 1.0.
Category B and C butt welds shall be spot radiography (RT3) hence the joint efficiency is 0.85.
This is because longitudinal joints are more critical than circumferential joints.
In general, heads connecting with shell will fall on Category B (RT-3 Spot Radiography), however in case of hemispherical head, the head with shell joint will fall on Category A (RT-2 full radiography), because this joint is more critical or it will be under double stress.
Rt1 Rt2 Rt3 Rt4 Radiography Mount
To help you better understand the weld joint category, we have taken a snap from ASME sec VIII Div.1 which shows the type of Joint category as shown below,