Configuration photograph available on enquiry.
Dervos valve · Product specification
High Pressure Check Valve
Non-return protection where the governing question is not the rating but how fast the valve closes when flow reverses.
- Size
- NPS 2 - 24 (DN 50-600)
- Pressure class
- Class 600 - 2500
- Body material
- A105, A182 F11, F22, WB36; WCB, WCC, WC6, WC9 where cast
- End connection
- BW to ASME B16.25, SW, flanged RF or RTJ
Catalogue ranges for initial selection. Final rating and configuration are confirmed against your project specification.
Have an MTO or datasheet? Send it with size, class, material, quantity and required delivery.
01 / Selection data
Technical specifications
Use these ranges to shortlist the valve. Values marked “confirm per order” depend on the selected size, material or project standard.
Swipe or scroll sideways to view the full table.
| Parameter | Specification | Basis |
|---|---|---|
| Size | NPS 2 - 24 (DN 50-600) | Catalogue range |
| Pressure class | Class 600 - 2500 | Catalogue range |
| Design temperature | up to 425 °C / 800 °F | Configuration dependent |
| Type | Swing check, piston lift check, tilting disc on request | Catalogue range |
| Cover | Bolted to Class 600, pressure seal from Class 900 | Catalogue range |
| Medium | Water, feedwater, condensate, steam, oil, gas | Catalogue range |
| Body material | A105, A182 F11, F22, WB36; WCB, WCC, WC6, WC9 where cast | Catalogue range |
| Trim material | 13Cr / F6a, Stellite 6 hardfaced seat and disc | Catalogue range |
| Hinge pin | Hardened F6a or Inconel 718, renewable | Catalogue range |
| End connection | BW to ASME B16.25, SW, flanged RF or RTJ | Catalogue range |
| Installation | Horizontal line, cover up, unless qualified otherwise | Confirm per order |
02 / Engineering
Valve design & materials
Closure behaviour stated, not assumed
Where the reverse-flow case matters we ask for it and state the resulting selection. The alternative is a valve that meets its hydro test and slams on the first pump trip.
Swing or piston lift, chosen against the duty
Swing for low pressure drop on steady flow. Piston lift where fast closure and stability under fluctuating flow matter more than head loss.
Renewable hinge pin and bushings
The hinge is the wear point on a swing check. Pin and bushings are replaceable without scrapping the body.
Hardfaced seat and disc
Stellite 6 on both contact faces, because a check valve seats under impact rather than under controlled stem load.
Full-bore body
Seat bore matched to the pipe so the valve does not become the restriction in the line.
Reference material configurations
Material combinations are examples for selection; the final bill of materials is agreed for each order.
Swipe or scroll sideways to view the full table.
| Part | Carbon steel | Alloy steel | F91 / F92 |
|---|---|---|---|
| Body | A105 / A105N | A182 F11, F22 | A182 F91, F92 |
| Seat ring | 13Cr + Stellite 6 | 13Cr + Stellite 6 | F91 + Stellite 6 |
| Disc | A105 + Stellite 6 | F11 / F22 + Stellite 6 | F91 + Stellite 6 |
| Hinge arm | A182 F6a | A182 F6a | A182 F6NM |
| Hinge pin | A182 F6a, hardened | A182 F6a, hardened | A182 F6NM / Inconel 718 |
| Bushing | Stellite 6 / hardfaced | Stellite 6 / hardfaced | Stellite 6 / hardfaced |
| Cover (bonnet) | A105 / A105N | A182 F11, F22 | A182 F91, F92 |
| Cover plug / vent | A105 | A182 F11 / F22 | A182 F91 |
| Nameplate | AISI 304 | AISI 304 | AISI 304 |
Service fit
Where this valve is used
Typical applications
- Pump discharge on parallel pump sets
- High-pressure feedwater and condensate
- Compressor discharge non-return
- Process lines where backflow would contaminate upstream equipment
- Header connections on multi-source systems
Selection limits to check
- Isolation. A check valve is not a shut-off valve and must not be used as one; specify a stop-check if you need both functions.
- Pulsating or reciprocating flow without a dynamic study. Repeated part-lift hammering destroys the hinge and seat.
- Very low flow rates, where a swing disc will flutter on its seat rather than sit open or shut.
- Positions where the closure case has not been defined. Without knowing what happens on a trip, any selection is a guess.
Quality assurance
Inspection & delivery documents
The inspection and test plan defines the agreed scope, hold points and witness points for your order.
Inspection scope
- 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
Document package
- 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
Reference framework
Applicable standards
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.
Face-to-face and end-to-end dimensions. Relevant when the valve replaces an existing one or has to drop into a fixed spool.
Butt welding end preparation, including bore and bevel geometry for the matching pipe schedule.
Flanged end dimensions and ratings, when the valve is supplied with RF or RTJ flanges rather than weld ends.
Inspection and pressure testing - which tests are mandatory, test durations and allowable leakage. We state the shell and seat test scheme on the ITP.
Alternative pressure testing scheme for steel valves, used where the project specification calls for it instead of API 598.
Marking of the body and the nameplate - size, class, material heat, figure number and flow direction where applicable.
Buying questions
Frequently asked questions
Swing or lift - how do I decide?
If flow is steady and pressure drop matters, swing. If flow fluctuates, or reverse flow builds quickly on a trip, piston lift closes faster and is more stable. If you can tell us the trip case, we will tell you which one and why.
Can it be installed vertically?
Sometimes, and it has to be confirmed per item. A swing check in a vertical line needs flow upward and the hinge geometry checked; some sizes need a spring assist. Horizontal with the cover up is the default because it is the case the standard design is qualified for.
Why does the datasheet ask for the pump curve?
Because the closure case on parallel pumps is one pump tripping while the others keep running, and the reverse velocity that produces depends on the curve and the system head, not on the valve. Without it we can rate the valve but not tell you how it will behave.