Dervos valve · Product specification
High Pressure Globe Valve
Tight shut-off and the only construction here that tolerates throttling. Standard on drains, vents, warm-up and bypass lines.
- Size
- NPS 2 - 16 (DN 50-400)
- 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
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 - 16 (DN 50-400) | Catalogue range |
| Pressure class | Class 600 - 2500 | Catalogue range |
| Design temperature | up to 425 °C / 800 °FAbove this the item moves to the pressure seal or forged range on material grounds. | Configuration dependent |
| Bonnet | Bolted to Class 600, pressure seal from Class 900 | Catalogue range |
| Pattern | Straight, Y-pattern and angleY-pattern gives lower pressure drop; angle removes an elbow from the line. | Catalogue range |
| Medium | Steam, condensate, feedwater, oil, gas | Catalogue range |
| Body material | A105, A182 F11, F22; WCB, WC6, WC9 where cast | Catalogue range |
| Trim material | 13Cr / F6a with Stellite 6 hardfacing | Catalogue range |
| Disc | Plug type; ball type on tight shut-off duty | Catalogue range |
| End connection | BW to ASME B16.25, SW, flanged RF or RTJ | Catalogue range |
| Flow direction | Under the seat unless otherwise stated | Catalogue range |
02 / Engineering
Valve design & materials
Seat survives partial opening
The disc lifts off the seat rather than sliding across it, so throttling dissipates energy in the flow path and not on the sealing face.
Y-pattern and angle options
Y-pattern reduces the pressure drop by straightening the flow path. An angle body removes an elbow, which matters on cramped drain manifolds.
Two-layer Stellite 6
Hardfacing applied in two layers so the finished surface is not diluted by the parent metal, then machined to the seating profile.
Live-loaded gland option
Belleville stacks maintain packing load through thermal cycles on positions that are operated frequently.
Renewable seat ring
Threaded or seal-welded seat ring so the sealing surface can be replaced rather than the whole body scrapped.
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 |
| Disc (plug type) | A105 + Stellite 6 | F11 / F22 + Stellite 6 | F91 + Stellite 6 |
| Disc nut / stem coupling | A182 F6a | A182 F6a | A182 F6NM |
| 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 |
| Stem packing | Flexible graphite | Flexible graphite | Flexible graphite, low-leakage set |
| Yoke / yoke bushing | WCB / Ni-Al bronze | WCB / Ni-Al bronze | WCB / 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 | ~60 kg |
| NPS 3 | DN 80 | 470 mm | ~115 kg |
| NPS 4 | DN 100 | 546 mm | ~195 kg |
| NPS 6 | DN 150 | 705 mm | ~420 kg |
| NPS 8 | DN 200 | 832 mm | ~760 kg |
| NPS 10 | DN 250 | 991 mm | ~1240 kg |
| NPS 12 | DN 300 | 1130 mm | ~1900 kg |
Service fit
Where this valve is used
Typical applications
- High-pressure drains and continuous blowdown
- Vents and startup lines
- Warm-up and bypass around main isolation valves
- Chemical dosing and sampling connections
- Any position where the valve will sit partly open
Selection limits to check
- Full-bore isolation where pressure drop matters. The S-shaped flow path costs head even fully open.
- Lines that must be pigged.
- Modulating control duty. A globe valve tolerates throttling; a control valve is designed for it, with trim sized to the flow curve.
- Reverse flow. Direction is not optional: flow goes under the seat unless the datasheet says otherwise.
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
Straight, Y-pattern or angle?
Straight is the default and the cheapest. Y-pattern where pressure drop matters and there is room for the longer body. Angle where it lets you delete an elbow, which on a drain manifold often pays for itself in fittings and welds.
Does flow direction really matter?
Yes. Under the seat is standard: it keeps pressure off the packing when the valve is shut and lets the disc lift against flow. Over the seat is specified occasionally for particular reasons. Installing one backwards produces chatter and rapid seat damage, so the body carries a flow arrow.
Can this replace a control valve?
No, and we will say so. A globe valve tolerates throttling; a control valve has trim sized to a required flow characteristic. Using this in a modulating position will control badly and wear quickly.