Draft page. The factory document pack for this page is still under review. Values marked “To be confirmed” have not been verified yet.
Fully welded ball valves
Ball valves · API 6D
A fully welded ball valve has a sealed steel body with no bolted body joint, made by welding the body parts together. With no body gasket there is no leak path at the joint, which is why the type is used in buried, district heating and offshore lines.
Who makes this valve
We publish one number per API specification, never a factory-by-factory row: a row with its licence set and expiry year would point at a single registry entry. One RFQ is quoted by several panel factories, and each quotation names the manufacturer, its API licence number and where to verify it, so you can check the source before you order. How we check licences
How it compares
| Feature | Fully welded | Side entry | Top entry |
|---|---|---|---|
| Body construction | Steel body parts joined by welding | Two- or three-piece body with a bolted joint | One-piece body with a bolted bonnet |
| Joints that can leak | Body welds plus the stem seal | Body joints plus the stem seal | Bonnet joint plus the stem seal |
| In-line maintenance | Not designed for seat replacement; the valve is normally replaced | Body opened after removal from the line | Serviced through the top flange in the line |
| Buried installation | Common, with an extended stem to the surface | Possible, but the body joint is buried | Less common |
Specification range
Grades listed are common ASTM designations for this valve type. The size and class range offered by the partner factory is confirmed against its datasheet before this page goes live.
| ASTM grade | Form | Sizes (NPS) | Pressure classes | End connections | Partner factory supplies |
|---|---|---|---|---|---|
| ASTM A105 | Forged carbon steel body | To be confirmed | To be confirmed | To be confirmed | To be confirmed |
| ASTM A350 LF2 | Forged low-temperature carbon steel | To be confirmed | To be confirmed | To be confirmed | To be confirmed |
| ASTM A216 WCB | Cast carbon steel body | To be confirmed | To be confirmed | To be confirmed | To be confirmed |
| ASTM A182 F316 | Forged 316 stainless steel | To be confirmed | To be confirmed | To be confirmed | To be confirmed |
| ASTM A351 CF8M | Cast 316 stainless steel | To be confirmed | To be confirmed | To be confirmed | To be confirmed |
Pressure–temperature rating (ASME B16.34)
The pressure class sets the maximum working pressure at each temperature for a given body material group. The table shows ASME B16.34 Standard Class values for material group 1.1 (for example A105 and WCB) at −29 °C to 38 °C. Seat and seal materials may limit a valve below the shell rating.
| Pressure class | Max. working pressure (bar) | (psi) |
|---|---|---|
| Class 150 | 19.6 | 285 |
| Class 300 | 51.1 | 740 |
| Class 600 | 102.1 | 1,480 |
| Class 900 | 153.2 | 2,220 |
| Class 1500 | 255.3 | 3,705 |
| Class 2500 | 425.5 | 6,170 |
Partner factory P-T curve for this valve: To be confirmed
How the body is welded
A fully welded valve is built from two or more body parts joined by welding. The pressure-containing welds are made to a qualified welding procedure, and the method and extent of radiographic or ultrasonic examination are agreed in the purchase order.
With no gasketed body joint there is no joint to retorque and no gasket to replace. The stem seal remains the one part that has to be maintained, so its design and the access to it matter as much as the body weld.
Buried installation and stem extensions
In a buried line the valve body stays below ground and an extended stem brings the operator to the surface. The extension is supported and the valve is marked so it can be found; the buried body is protected by coating and, where specified, cathodic protection.
API 6D covers the valve itself. The stem extension, its support, the surface box and the access for the operator are agreed in the purchase order, because they depend on the burial depth and the layout of the line.
Testing and documents to request
The welded body is pressure tested after assembly, normally with a hydrostatic shell test and a seat test per API 6D, or per API 598 where the purchase order names it. Ask for the weld procedure, the welder qualifications and the examination reports as well as the pressure test record.
Material certificates to EN 10204 3.1 should state the heat numbers, and the coating report should give the dry film thickness measured on the finished body.
Fire-safe design and fugitive emissions
A fully welded body removes the body-gasket leak path, but the stem seal still has to survive a fire. API 607 and ISO 10497 test the assembled valve and then check that it still isolates, so the certificate must cover the stem seal design and the size range.
ISO 15848-1 covers fugitive emissions from the stem seal, with tightness classes measured before and after mechanical and thermal cycles. Buried valves are often specified with a low-emission class because access for repair is difficult.
No fire-test or emission-test certificate for a partner factory valve is published on this page.
Datasheet and drawings
Datasheet: To be confirmed
A datasheet, dimension drawing and STEP file will be published here, without factory branding, after the panel factory authorises them. Until then, ask for them in your RFQ.
Prices, lead times and minimum order quantities are quoted per enquiry against the datasheet you send; they are not listed on this page.
Frequently asked questions
- What is a fully welded ball valve?
- A ball valve whose body parts are joined by welding instead of a bolted joint. The welded body has no body gasket, so the only dynamic seal left is the stem seal.
- Why use a fully welded ball valve instead of a side entry valve?
- Because there is no gasketed body joint to leak or to retorque. That matters in buried lines, district heating and offshore service, where access for maintenance is difficult or a joint below ground is a risk.
- Can a fully welded ball valve be repaired?
- The seats are not accessible without cutting the body, so a seat failure normally means replacing the valve. The stem seal can often be renewed from the top, depending on the design; ask for the repair procedure with the datasheet.
- Are fully welded ball valves used for district heating?
- Yes. Pre-insulated district heating lines and buried gas and water lines use them because a gasketed body joint below ground would be a maintenance point. The stem extension and the insulation are part of the valve specification.
- What standard covers a fully welded ball valve?
- API 6D is the usual specification for pipeline service. API 608 covers metal ball valves with flanged, threaded and welding ends. The purchase order should name the specification and edition, because the welding and examination requirements differ.
Standards cited
- API Spec 6D: Pipeline and piping valves: design, manufacture, testing and documentation of ball, gate, plug and check valves.
- API Std 598: Valve inspection and pressure testing (shell, backseat and seat).
- EN 10204: Types of inspection documents, including the 3.1 and 3.2 certificates.
- API Std 607: Fire test for quarter-turn valves with non-metallic seats: a type test of the design.
- ISO 10497: Fire type-testing requirements for valves: test procedure and acceptance criteria.
- ISO 15848-1: Fugitive emissions: measurement, test and qualification procedures for valve stem seals, with tightness classes from a type test.
- ASME B16.34: Valves with flanged, threaded and welding ends: pressure–temperature ratings by material group and pressure class. Edition quoted to: ASME B16.34-2025.