Dervos valve · Product specification
High Pressure Gate Valve
Full-bore isolation at high pressure. Bolted bonnet where the class allows it and maintenance access matters, pressure seal where it does not.
- Size
- NPS 2 - 24 (DN 50-600) （test）
- Pressure class
- Class 600 - 2500
- Body material
- A105, A182 F11, F22; WCB, WC6, WC9 where cast
- End connection
- BW to ASME B16.25, SW, flanged RF or RTJ
- Operation
- Handwheel, bevel gear, electric or pneumatic actuator
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.
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| Parameter | Specification | Basis |
|---|---|---|
| Size | NPS 2 - 24 (DN 50-600) （test）Larger sizes are confirmed per item. | Catalogue range |
| Pressure class | Class 600 - 2500 | Catalogue range |
| Design temperature | up to 425 °C / 800 °FAbove this the body grade moves to F22 or higher and the item belongs in the pressure seal or forged range. | Configuration dependent |
| Bonnet | Bolted to Class 600, pressure seal from Class 900 | Catalogue range |
| Medium | Water, condensate, feedwater, steam, oil, gas | Catalogue range |
| Body material | A105, A182 F11, F22; WCB, WC6, WC9 where cast | Catalogue range |
| Trim material | 13Cr / F6a, hardfaced with Stellite 6 on request | Catalogue range |
| Wedge | Flexible wedge, solid wedge on request | Catalogue range |
| End connection | BW to ASME B16.25, SW, flanged RF or RTJ | Catalogue range |
| Operation | Handwheel, bevel gear, electric or pneumatic actuator | Confirm per order |
02 / Engineering
Valve design & materials
Bonnet chosen by class, not by habit
Bolted below Class 900 because it is easier to strip and reseat; pressure seal above it because bolt load and gasket creep stop being manageable. We state which you are getting and why.
Flexible wedge
A relief groove lets the wedge flex slightly so it seats squarely when the body distorts under thermal load, instead of bearing on one face.
Hardfaced seating on steam duty
Stellite 6 overlay on the seat and wedge faces where the medium is steam or the closure count is high. Plain 13Cr where the duty does not need it, and we will say so rather than upsell.
Back seat
Allows the packing to be renewed under pressure where the operating procedure permits it.
Full bore
The seat bore matches the pipe bore, so pressure drop when open is negligible and the line can be pigged where that matters.
Reference material configurations
Material combinations are examples for selection; the final bill of materials is agreed for each order.
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| 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 |
| Wedge (flexible) | A105 + Stellite 6 | F11 / F22 + Stellite 6 | F91 + Stellite 6 |
| Stem | A182 F6a | A182 F6a Cl.2 | A182 F6NM / 422SS |
| Bonnet | A105 / A105N | A182 F11, F22 | A182 F91, F92 |
| Gland | A105 | A182 F11 / F22 | A182 F91 |
| Gland flange | A105 | A105 | A182 F91 |
| Stem packing | Flexible graphite | Flexible graphite | Flexible graphite, low-leakage set |
| Gland eyebolt / pin | A193 B7 / A194 2H | A193 B16 | A193 B16 |
| Yoke | A105 / WCB | A105 / WCB | A105 / WCB |
| Yoke bushing | Ni-Al bronze | Ni-Al bronze | Ni-Al bronze |
| Back seat | 13Cr overlay | 13Cr overlay | Stellite overlay |
| Handwheel | Ductile iron / carbon steel | Ductile iron / carbon steel | Ductile iron / carbon steel |
| Nameplate | AISI 304 | AISI 304 | AISI 304 |
03 / Reference dimensions
Dimensions & approximate weight
Typical reference values only. Request the approved GA drawing and confirmed weight for your selected class and configuration.
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| NPS | DN | Face to face / end to end | Approx. weight |
|---|---|---|---|
| NPS 2 | DN 50 | 368 mm | ~55 kg |
| NPS 3 | DN 80 | 470 mm | ~105 kg |
| NPS 4 | DN 100 | 546 mm | ~180 kg |
| NPS 6 | DN 150 | 705 mm | ~390 kg |
| NPS 8 | DN 200 | 832 mm | ~700 kg |
| NPS 10 | DN 250 | 991 mm | ~1150 kg |
| NPS 12 | DN 300 | 1130 mm | ~1750 kg |
| NPS 16 | DN 400 | 1410 mm | ~3200 kg |
Service fit
Where this valve is used
Typical applications
- High-pressure water, condensate and feedwater lines
- Process steam headers below the creep range
- Refinery and petrochemical high-pressure isolation
- Compressor and pump discharge isolation
- Utility and interconnection isolation on high-pressure systems
Selection limits to check
- Throttling or flow control. A partly open wedge concentrates the pressure drop on the seat and erodes it. Use a globe valve.
- Metal temperatures in the creep range without moving to a creep-grade body. Above roughly 540 °C the grade decides the valve, not the type.
- Slurries and crystallising media that settle in the body cavity under the wedge.
- Frequent cycling. The multi-turn stroke is slow and the packing becomes a consumable.
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
When should I specify this rather than a pressure seal gate valve?
Below Class 900 and below the creep range, this is the simpler and cheaper valve, and the bolted bonnet is easier to maintain. Above Class 900, or where the metal temperature calls for F91 or F92, the pressure seal range is the correct one. Tell us the duty and we will say which applies.
Cast or forged body?
Both are offered. Forged has no casting porosity and behaves better under thermal cycling; cast allows shapes that would be uneconomic to forge and is entirely adequate on steady duty. If the specification is silent we propose one and state the reason.
Can it be used for throttling if we only need it occasionally?
We would advise against it and say so on the quotation. Even occasional throttling puts the full pressure drop across a small gap at the seat, and the damage is cumulative and not repairable in service.