DJ46H SDNR Globe Valve

DJ46H SDNR Globe Valve Definition and Components

What is a DJ46H Valve?

The DJ46H is a Stop-Check Globe Valve, commonly designated as an SDNR valve (Stop, Disc, Non-Return). The code typically breaks down as: D (for a specific series/corrosion-resistant), J (Globe Valve), 4 (Flanged), 6 (Stop-Check function), H (Hardened seat). It is a dual-purpose valve combining the functions of a manual isolation (globe) valve and an automatic check (non-return) valve in one body.

Globe Valve for Water Main Parts:

• Valve Body: A flanged, Z-pattern (globe) body, usually made of carbon steel (WCB) or alloy steel for high-temperature service.
• Bonnet: Bolted to the body, houses the stem assembly. Often includes a yoke.
• Stem & Handwheel: For manual operation. The stem is connected to a lifting mechanism inside the bonnet.
• Disc (or Plug): The primary closure element. It is not rigidly fixed to the stem.
• Seat Ring: A hardened, usually angle-seat ring where the disc seals.
• Stop-Check Mechanism: The defining feature.

It consists of a yoke or guides that allow the stem to lift the disc manually for flow or closure, but also permit the disc to close automatically via gravity/pressure if the stem is left in the raised position and reverse flow begins.

Role, Characteristics, and Application Scenarios of DJ46H SDNR Globe Valve in Pipelines

Pipeline Functions:

• Manual Isolation: Functions as a standard globe valve for positive shut-off when the handwheel is used to seat the disc.
• Automatic Check (Non-Return): Functions as an automatic check valve to prevent reverse flow when the handwheel is backed off (leaving the disc free to move).
• Flow Throttling: The globe design allows for moderate flow regulation.

Operational Features:

• Dual-Function Flexibility: One valve serves two purposes, saving space and cost compared to installing separate isolation and check valves.
• Free-Disc Design: The disc is free to lift off the seat for check action but can be locked closed by the stem.
• Preferred Direction: Typically installed so that flow lifts the disc. The disc closes by gravity and back-pressure.
• Not for Rapid Cycling: The closing action is gravity-dependent, not spring-assisted, so it's slower than a dedicated check valve.

Water Valves Application Scenarios:

• Used in systems where both reliable isolation and backflow prevention are required, often in critical power or process services.
• Boiler Feedwater Lines: The classic application. It isolates the feedwater pump while also automatically preventing boiler water from flowing back into a stopped pump.
• Pump Discharge on Critical Systems: Where a dedicated check valve is needed, but operators also require a guaranteed positive isolation point.
• High-Pressure Steam Bypass Lines: In power plant turbine systems.
• Main Steam Isolations: In smaller boiler systems.

Scenario Diagram (Text Description):

In a power plant boiler system, a feedwater pump supplies high-pressure water to the boiler drum. A DJ46H (SDNR) valve is installed on the pump discharge line. During normal operation, the plant operator opens the valve manually via the handwheel, lifting the disc and allowing flow to the boiler. The handwheel is left in the open position, leaving the disc free. If the feedwater pump suddenly trips, flow reverses. The free disc immediately slams shut onto its seat by the combined force of gravity and reverse pressure, preventing the high-pressure boiler water from rushing back into the pump and causing damage. For maintenance, the operator can manually screw the stem down to forcibly seat the disc, providing a positive, leak-tight isolation for the pump.

DJ46H SDNR Globe Valve Standards: Materials, Design, and Connections

Material Standards:

• Body/Bonnet: ASTM A216 WCB (CS), A217 WC6/WC9 (C-Mo Alloy for high temp).
• Disc & Seat: Hardened 13% Chrome steel, Stellite-faced (Co-Cr alloy) for erosion resistance.
• Stem: 13% Cr or 17-4PH stainless steel.
• Bolting: ASTM A193 B7/B16.

Design Standards:

• API 602: For compact steel gate, globe, and check valves. A key design standard.
• ASME B16.34: Valve Pressure-Temperature Ratings.
• MSS SP-80: Bronze globe valves (for reference on design).

Connection Standards:

Flanges: ASME B16.5 Class 1500, 2500, or higher are common for high-pressure boiler service. Raised Face (RF) or Ring-Type Joint (RTJ).

How to Select DJ46H SDNR Globe Valve

Key Steps:

• Confirm the Need for Dual Function: Specify that you require a Stop-Check (SDNR) globe valve, not a standard globe or check valve.
• Define Service Rigorously: This valve is for critical service. Specify exact pressure, temperature, and fluid (e.g., "Feedwater, 2500 psi, 250°C")
• Specify Materials for Erosion/Corrosion: For boiler feedwater, insist on hardened trim (e.g., 13% Cr or Stellite 6 overlay on disc and seat) to resist wire-drawing erosion.
• Clarify the Operation: Understand and specify the free-disc lift required and ensure the design uses a yoke and guide mechanism to prevent disc rotation and ensure proper re-seating.

Pre-Shipment Inspection for Export DJ46H SDNR Globe Valve and Key Considerations

Inspection Checklist:

Dual-Functionality Test (Critical):

• Manual Stop Function: Operate with handwheel to ensure the stem can forcibly seat the disc for a tight shut-off.
• Automatic Check Function: With the handwheel backed off to the fully open position, verify the disc is free to move. Blow air through the valve in the reverse direction to confirm the disc swings shut.
• Pressure Testing: Perform shell and seat tests per API 598. Seat leakage must be within acceptable limits for metal-seated valves.
• Material Verification: Check PMI on body, bonnet, and most importantly, the disc and seat hardening/stellite application.

 

Export Precautions:

• Secure the Disc: Before shipping, the disc must be locked in the closed position using the handwheel. This prevents the free-moving disc from flailing and damaging the seat during transit.
• Protect Flange Faces: Use heavy, bolted metal covers on flange faces, especially for high-pressure RTJ grooves.
• Documentation: Ensure material certificates and pressure test reports are included, with specific note of the trim hardness and Stellite facing if applicable.

DJ46H SDNR Globe ValveMaterials

NO.	Parts		Materials
1	Body		Cast iron
2	Body Seat Ring		Stainless Steel
3	Disc Seat Ring(DN65-300)		Stainless Steel
4	Disc	DN15-50	Stainless Steel
		DN65-300	Cast iron
5	Screw		Steel
6	Nut		Steel
7	Bolt		Steel
8	Steel Ball		Steel
9	Gasket		Graphite
10	Stem		Stainless Steel
11	Bonnet		Cast iron
12	Bolt		Steel
13	Nut		Steel
14	Glander Follower		Ductile iron
15	Stem Nut		Cast Brass
16	Screw		Steel
17	Hand wheel		Cast iron
18	Washer		Steel
19	Nut		Steel
20	Packing		Graphite

DJ46H SDNR Globe Valve Main dimensions(PN16/PN10)

Size	L	D	D1	D2	B	f	n -d	D0	H
DN15	130	95	65	46	14	2	4-14	100	162
DN20	150	105	75	56	16	2	4-14	100	169
DN25	160	115	85	65	16	3	4-14	120	187
DN32	180	150	100	76	18	3	4-19	120	223
DN40	200	150	110	84	19	3	4-19	140	234
DN50	230	165	125	99	20	3	4-19	140	262
DN65	290	185	145	118	20	3	4-19	200	293
DN80	310	200	160	132	20	3	8-19	200	341
DN100	350	220	180	156	22	3	8-19	240	381
DN125	400	250	210	184	24	3	8-19	280	419
DN150	480	285	240	211	26	3	8-23	315	485
DN200	600	340	295	266	30	3	12-23	360	569
DN250	730	405	355	319	32	3	12-28	400	634
DN300	850	460	410	370	32	4	12-28	400	801

 Note:1. Other specifications and flange standards are available upon request.

2. Design and specifications are subject to change without prior notice.