API 20E BSL -1/2/3 Stud Bolt &Nuts

API 20E Alloy and Carbon Steel Bolting for Use in the Petroleum and Natural Gas Industries

API 20E Bolting Specification Levels (BSLs)

The API 20E standard categorizes fasteners into three Bolting Specification Levels (BSL-1, BSL-2, and BSL-3), each reflecting increasing levels of quality control, testing, and qualification requirements. These levels are tailored to the severity of the application and the possible implications of failure –

• BSL-1: The baseline level, suitable for less critical applications. It requires basic quality controls and testing to ensure the fasteners meet minimum performance standards.
• BSL-2: A more stringent level, BSL-2 includes additional testing and documentation, such as traceability of raw materials and enhanced inspection processes. It is used in applications where failure risks are moderate but still significant.
• BSL-3: The highest level, reserved for the most critical applications like subsea equipment or high-pressure wellheads. It requires strict quality checks which includes advanced testing, detailed process controls and full traceability. This level is designed for zero-failure scenarios, where a malfunction could result in severe environmental or human harm.

API 20E BSL-1 Stud Bolts

Standard Quality Level for General Oil & Gas Service

BSL-1 is the baseline API 20E level, suitable for non-critical or low-risk bolting applications.

• Material manufactured to ASTM specification (e.g., A193 B7)

• Standard heat treatment and testing

• Basic traceability

• Manufacturer quality system verification

Typical Applications:

• Onshore oil & gas facilities

• Non-critical piping and flanges

• General refinery bolting

API 20E BSL-2 Stud Bolts

Enhanced Quality & Traceability for Critical Equipment

BSL-2 introduces additional controls for bolting used in critical pressure equipment.

Key Features:

• Enhanced chemical and mechanical verification

• Increased testing frequency

• Full heat and lot traceability

• Process qualification and documentation

• Risk-based quality controls

Typical Applications:

• Offshore platforms

• Pressure vessels

• High-pressure piping systems

• Critical refinery and petrochemical units

API 20E BSL-3 Stud Bolts

Highest Integrity Bolting for Subsea & Extreme Service

BSL-3 is the highest and most stringent API 20E level, required for safety-critical and high-risk applications.

Key Features:

• Full process traceability (raw material → finished stud)

• Extensive mechanical and metallurgical testing

• Increased NDT requirements

• Third-party witnessing (when specified)

• Strict change management and documentation control

Typical Applications:

• Subsea bolting systems

• Wellheads and Christmas trees

• Blowout preventers (BOPs)

• HPHT (High Pressure High Temperature) service

API 20E BSL Comparison Table

Quality control of API 20E stud bolt

Control of Raw Material  This additional control was imposed because poor quality raw material was found to be the cause of failures  Raw material suppliers (mills) must be qualified  Through on-site quality and process evaluation  For BSL-3, mills must be physically audited  Manufacturer must have raw material specifications for each material.

Heat Treatment BSL-2 Requirements

ASTM A320 Grade L43 and ASTM A540, Grade B23 material shall be double tempered  When threads are rolled, parts shall subsequently be stress relieved at a temperature within 50ºF (10ºC) of, but not exceeding the final tempering temperature  Done to control the increase of thread hardness / stress increase caused by the rolling process BSL-3 Requirements  Contact thermocouple required  Continuous, induction and direct resistance heat treating prohibited  Furnace diagram (or photo) required.

NDE Requirements BSL-2

 Surface NDE is required for 5% of each production lot

 Volumetric NDE required for 20E bolting greater than 2.5 inches nominal diameter

 20F: PMI required for 10 percent of each lot BSL-3

 Surface NDE required on each piece

 Volumetric NDE is required

 20E all nominal sizes

Dimensions / Visual

General  BSL-3 requires 100% dimensional inspection  Oversizing of nut threads or under sizing of bolt threads is not permissible

Hardness

 Maximum HRC of 34 for BSL-1, BSL-2 & BSL-3  BSL-2 & BSL-3:

 Each piece must be Hardness tested

API 20E Stud Bolt Marking

 Mfg. trademark & material type (US L43)

 Part Number (if required by client)

 API 20E BSL Level, (20E2)

 Month/Year of Manufacture

 API 20E License Number

 Manufacturers Heat Treat Lot Number

 Specific Part Serial Number (19)

 API Monogram

API 20E BSL 1 2 3 Stud Bolt

Common Materials for API 20E Stud Bolts

API 20E can be applied to various bolting grades, including:

ASTM A193 Grade B7 STUD BOLT
ASTM A193 Grade B7M STUD BOLT
ASTM A193 Grade B16 STUD BOLT
ASTM A194 Grade 2H
ASTM A194 Grade 2HM
ASTM A194 Grade 7
ASTM A194 Grade 7M
ASTM A320 Grade L7 STUD BOLT
ASTM A320 Grade L7M STUD BOLT
ASTM A320 Grade L43 STUD BOLT

Coatings  (Optional)

API 20E stud bolts can be supplied with:

• Xylan® 1424 / 1014 / 1070

• PTFE coating

• Zinc-aluminum coating

Testing & Certification

API 20E stud bolts are supplied with:

• ASTM Mill Test Certificate (MTC)

• API 20E compliance statement

• Traceability records

• EN 10204 3.1 / 3.2 (when required)

• Third-party inspection reports (BSL-2 / BSL-3)

API 20E BSL-1, BSL-2, and BSL-3 stud bolts provide a structured quality framework for critical oil & gas bolting applications, ensuring safety, reliability, and full traceability. While BSL-1 suits general service, BSL-2 and BSL-3 stud bolts are essential for offshore, subsea, and high-risk environments.