Forged Power Plant Check Valve
Check valves with a one-piece forged pressure boundary for power station duty, in both pressure seal and bolted cover arrangements depending on class.
- Size NPS 1/2-24 (DN 15-600)
- Pressure class Class 150-2500
- Design temperature up to 650 °C / 1200 °F
- Body material A105, A182 F11, F22, F91, F92, F304/F316 for auxiliary
- End connection SW, NPT, BW, flanged RF or RTJ
Overview
The forged-body version of the check valve range, specified where the project requires forged rather than cast pressure-containing parts. Forging is chosen for grain flow and the absence of casting porosity, which matters most in thick sections under thermal cycling. Cover arrangement follows the class: bolted up to Class 600, pressure seal from Class 900.
Target systems
- Feedwater pump discharge and recirculation
- Boiler circulating pump discharge
- Superheater and reheater drains
- Auxiliary and gland steam
- Small-bore instrument and sampling lines (API 602 sizes)
- Use as an isolation valve. It has no positive shut-off function.
- Duties where a cast body is explicitly specified and no deviation is permitted - forged is not automatically an upgrade in a client specification.
- Very large bores where a forging of the required section is not economically available; above roughly NPS 24 this becomes project-dependent.
Technical data
Every value is marked standard for the catalogue range, typical where it depends on material or configuration, or per project where it can only be confirmed against your specification.
| Parameter | Value | Basis |
|---|---|---|
| Size | NPS 1/2-24 (DN 15-600) Small bore below NPS 2 follows API 602 construction. | standard |
| Pressure class | Class 150-2500 | standard |
| Cover type | Bolted to Class 600, pressure seal from Class 900 | standard |
| Design temperature | up to 650 °C / 1200 °F | typical |
| Body material | A105, A182 F11, F22, F91, F92, F304/F316 for auxiliary | standard |
| Body construction | One-piece forged pressure boundary We state per size which features are integral to the forging and which are welded. | standard |
| Type | Swing, piston lift, ball check (small bore) | standard |
| End connection | SW, NPT, BW, flanged RF or RTJ | standard |
| NDE scope | UT or RT on the forging, MT/PT on machined surfaces | per project |
Design
One-piece forged pressure boundary
Body machined from a single forging. Grain flow follows the contour of the part instead of being interrupted, and there is no shrinkage porosity in the thick sections around the seat. On thick-wall Class 1500 and 2500 parts this is the main technical argument for forging over casting.
Class-appropriate cover arrangement
Bolted cover below Class 900 because it is simpler to maintain and adequate for the duty; pressure seal above, because bolt load alone cannot hold the joint through repeated thermal cycles. We do not fit a pressure seal cover to a Class 300 valve to make the datasheet look better.
API 602 small-bore construction
Below NPS 2 the valves follow API 602 rather than API 600 - different wall thickness basis, different end connection set. Getting this right matters when the valve goes on an instrument or drain connection covered by the piping class.
Traceable material through the whole boundary
Each pressure-containing part carries the heat number through machining to final assembly, and the heat numbers on the MTC match the parts in the valve. This is checked at final inspection, not assumed.
Standard material specifications
Part numbering follows the general arrangement drawing. Three columns cover the common temperature bands; the actual configuration for your order is confirmed on the datasheet.
| No. | Part name | Carbon steel | Low alloy | Creep grade |
|---|---|---|---|---|
| 1 | Body | A105 / A105N | A182 F11, F22 | A182 F91, F92 |
| 2 | Seat ring | 13Cr + Stellite 6 | 13Cr + Stellite 6 | F91 + Stellite 6 |
| 3 | Disc | A105 + Stellite 6 | F11 / F22 + Stellite 6 | F91 + Stellite 6 |
| 4 | Hinge arm | A182 F6a | A182 F6a | A182 F6NM |
| 5 | Hinge pin | A182 F6a, hardened | A182 F6a, hardened | A182 F6NM / Inconel 718 |
| 6 | Bushing | Stellite 6 / hardfaced | Stellite 6 / hardfaced | Stellite 6 / hardfaced |
| 7 | Cover (bonnet) | A105 / A105N | A182 F11, F22 | A182 F91, F92 |
| 8 | Pressure seal ring | Flexible graphite + SS liner | Flexible graphite + SS liner | Flexible graphite + Inconel liner |
| 9 | Thrust ring (segmental) | A105 | A182 F11 / F22 | A182 F91 |
| 10 | Retainer segments | A105 | A182 F11 / F22 | A182 F91 |
| 11 | Cover plug / vent | A105 | A182 F11 / F22 | A182 F91 |
| 12 | Nameplate | AISI 304 | AISI 304 | AISI 304 |
Standards
What each standard actually governs on this valve. A standard listed without a scope is decoration.
| Standard | Applies to |
|---|---|
| ASME B16.34 | Pressure-temperature ratings, materials, wall thickness, testing and marking. This is the base rating standard for the valve - it is what fixes the allowable pressure at your design temperature. |
| ASME B16.10 | Face-to-face and end-to-end dimensions. Relevant when the valve replaces an existing one or has to drop into a fixed spool. |
| API 602 | Compact steel valves NPS 4 / DN 100 and smaller. Applies to the small-bore end of this range only - it is not the design basis for the large sizes. |
| ASME B16.25 | Butt welding end preparation, including bore and bevel geometry for the matching pipe schedule. |
| API 598 | Inspection and pressure testing - which tests are mandatory, test durations and allowable leakage. We state the shell and seat test scheme on the ITP. |
| MSS SP-25 | Marking of the body and the nameplate - size, class, material heat, figure number and flow direction where applicable. |
Inspection
- Hydrostatic shell test to API 598 / MSS SP-61
- Hydrostatic or pneumatic seat test, leakage rate per specification
- Back seat test (gate and globe, where a back seat is supplied)
- PMI on all pressure-containing parts and welded overlays
- NDE per specification - RT, UT, MT or PT as applicable
- Hardness survey after post-weld heat treatment
- Dimensional inspection against approved GA drawing
- Material certification EN 10204 3.1 (3.2 on request)
- Visual and functional check, full stroke on the manual operator
The actual scope, and which points are hold or witness, is set on the Inspection and Test Plan agreed before manufacture.
Documents supplied
- Product datasheet
- General arrangement (GA) drawing
- Inspection & Test Plan (ITP)
- Material test certificate (MTC) EN 10204 3.1
- Hydrostatic and seat test report
- PMI report
- NDE reports as applicable
- Heat treatment charts
- Dimensional report
- Packing list and preservation record
What each document proves, and which ones suppliers most often cannot produce
Manufacturing evidence
These positions are reserved for photographs of actual DERVOS VALVE production. They are shown as placeholders rather than filled with stock or rendered images - see the note on the company page about what this site will and will not claim.
Frequently asked questions
Is a forged body always better than a cast body?
For thick-wall, high-class, thermally cycled service, forging gives better grain structure and avoids casting porosity. For large-bore, complex-geometry, lower-class valves a good casting with proper NDE is entirely appropriate and usually cheaper. What matters is that the choice is made against the duty and stated on the datasheet - not that one is universally superior.
What NDE do you apply to the forging itself?
Typically UT on the forging before machining, then MT or PT on the finished machined surfaces, with the extent set by the specification. For F91 and F92 there is also a hardness survey after PWHT. We put the actual scope on the ITP rather than listing every method as though all are always applied.
Can you match an existing valve for a replacement?
Send the nameplate photograph, the figure number if legible, and the face-to-face dimension. Face-to-face to ASME B16.10 makes most replacements straightforward; a non-standard original does not, and we will say so rather than promise a drop-in fit we cannot confirm.