Class 900LB Stainless Steel Flexible Wedge Gate Valve — A351 CF8/CF8M, Flanged RF/RTJ or BW, NPS 2"–24"

This Class 900LB stainless steel gate valve is the API 600 flexible wedge, OS&Y rising stem, bolted bonnet design with a ring joint gasket on the body-bonnet joint. The body, bonnet, wedge, seat ring and gland flange are cast in ASTM A351 CF8 (304) or CF8M (316); the stem is A182 F304 or F316, with A193 B8/B8M bolting and A194 8/8M nuts. Flanged ends are to ASME B16.5 with either raised face (RF) or ring type joint (RTJ) facing; butt-weld ends to ASME B16.25 are also available. Face-to-face dimensions are per ASME B16.10, pressure-temperature ratings per ASME B16.34. Sizes run from NPS 2" to NPS 24". The valve is supplied with a handwheel as standard; a bevel gear operator is available on request.

Application

This Class 900 stainless steel gate valve is specified in high-pressure oil and gas, petrochemical and refinery process lines, power generation and high-energy utility service where the combination of 900LB pressure rating and stainless steel body is required. The ring joint bonnet gasket and the flexible wedge design are particularly suited to high-pressure and high-temperature service. For sour service the valve can be supplied to NACE MR0175 / ISO 15156 on request; CF8M (316) and RTJ ends are typically specified together in this case.

Standards

Design and Manufacture: Cast steel gate valve to API 600 or API 6D.
Inspection and Test: API 598, API 600 or API 6D.
End flange dimension: ASME B16.5 (for NPS ≤ 24); API 605 or ASME B16.47 series A / MSS SP-44 (for NPS > 24).
BW end dimension: ASME B16.25.
Face to face and end to end: ASME B16.10.
Pressure-temperature ratings: ASME B16.34.

Quick Details

1. Type: 900LB flexible wedge gate valve
2. Design: OS&Y, bolted bonnet, flexible wedge design
3. Size Range: 2" to 24" (DN50 to DN600)
4. Pressure Rating: ASME Class 900LB / 900#
5. Materials Available in: A351 CF8, CF8M, CF3, CF3M
6. Various trim materials are available to suit different service conditions
7. Actuator: Manual, handwheel (gear operated available on request)
8. Special Requirement: NACE MR0175 on request

Selection Notes: Ring Joint Gasket, CF8 vs CF8M and RF vs RTJ at Class 900

Why a ring joint gasket at Class 900: at Class 900, the pressure acting on the bonnet area is high enough that a spiral wound or sheet gasket would be at the edge of its reliable sealing range. The ring joint gasket uses a metal ring seated in a machined groove on both the body and the bonnet, and the seal is achieved by metal-to-metal contact between the ring and the groove. This provides a much more reliable seal at high pressure and high temperature, and it is why ring joint gaskets are standard from Class 900 upward in the API 600 gate valve range. At Class 150, 300 and 600 the spiral wound gasket is still the standard; the ring joint becomes the standard at Class 900.

CF8 (304) vs CF8M (316): CF8 corresponds to AISI 304 stainless steel; CF8M corresponds to AISI 316. The key difference is the molybdenum addition in CF8M, which significantly improves resistance to chloride pitting and crevice corrosion. At Class 900, where the valve is often used in high-pressure oil and gas, petrochemical and refinery service, CF8M (316) is the more common selection because of its better corrosion resistance in chloride-bearing media. CF8 (304) remains suitable for mildly corrosive media where chlorides are not present. Internals change accordingly: CF8 valves use A182 F304 stems and A193 B8 / A194 8 bolting, while CF8M valves use A182 F316 stems and A193 B8M / A194 8M bolting.

RF vs RTJ at Class 900: RF (raised face) ends to ASME B16.5 are available at Class 900 and are used where the line is non-sour and the pressure-temperature conditions do not demand a metal-to-metal seal. RTJ (ring type joint) ends use a metal ring gasket seated in a machined groove and are the standard choice at Class 900 for high-pressure, high-temperature and sour service, and are frequently specified together with NACE MR0175. On this valve, both RF and RTJ facings are available; the face-to-face dimensions differ between the two, as listed in the dimension table on this page.

Features

1. Body and Bonnet Connection
Class 900LB gate valves are usually connected with bolted bonnet design.

2. Seat
For carbon steel gate valve, the seat is usually forged steel. The seat sealing surface is overlay welded with hard alloy specified by the customer. For stainless steel gate valve, the seat is integral with body, or it can be machined directly after hard alloy welding.

3. Disc Design
NPS ≥ 2 gate valves are flexible wedge gate.

4. Backseat Design
All gate valves have backseat design. In most cases, the carbon steel gate valve is fitted with a renewable back seat. For stainless steel gate valve, the back seat is machined directly in the bonnet or machined after welding.

5. Stem Design
The stem is integral forged design. The minimum diameter of the stem shall be as per the standard requirement.

6. Stem Nut
Usually, the stem nut is made of ASTM A439 D2. It can also be made of copper alloy or other materials if requested by the customer.

7. Operation
Hand wheel or bevel gear box is usually used for gate valve operation.

8. Bonnet Gasket Style
Ring joint gasket is used for Class 900 gate valve.

9. Packing Seal
As usual, flexible graphite is used for packing material. PTFE or combined packing material can also be used if requested by the customer.

900LB Gate Valve Parts and Material List

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Parts No. 9 (Gland Eyebolt): original source had "ASTMA193 B8" without a space — corrected to "ASTM A193 B8". Gate (Parts No. 4): original source listed "ASTM A351 Cr8M" in the CF8M column — corrected to "ASTM A351 CF8M". Bonnet (Parts No. 15): original source listed "ASTM A351 Cf-8M" — corrected to "ASTM A351 CF8M". Stem Nut (Parts No. 17): original source listed "ASTM A439 02" in the CF8 column — corrected to "ASTM A439 D2". Set Screw (Parts No. 21) is shown as ASTM A193 B7 in both columns, as in the original source. Nipple, Yoke Sleeve Nut, Hand Wheel and Hand Wheel Nut are shown as carbon steel / ductile iron because these parts are not wetted and do not change with the body material.

Main Connection Dimensions — Class 900LB (mm)

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Dimensions in mm. L = face-to-face dimension (RF / RTJ) or end-to-end (BW) per ASME B16.10. RF and RTJ flange dimensions per ASME B16.5 for NPS ≤ 24; ASME B16.47 series A for NPS > 24 (not applicable to this table, which covers through NPS 24). At Class 900 the RTJ face-to-face dimension is shorter than the RF dimension for the same NPS (for example NPS 12: RF 965 mm, RTJ 958 mm) — this is the standard ASME B16.10 Class 900 relationship and is not a transcription error.

Frequently Asked Questions