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Fluid conveyance · Stainless check valves

TECHNICAL DATA SHEET

FT-TC-VAL-CHEQUE-INOX-001

Issue date: August 4, 2026 · Rev. 001

Check the current version

Threaded check valves in cast stainless steel ASTM A351 CF8M — vertical check, gate check and hydro check

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The threaded NPT check valves in cast stainless steel ASTM A351 CF8M from the TECTUL catalog: vertical stainless check —axially guided disc, the only design in the family that accepts vertical mounting with upward flow only—, stainless gate check —gravity gate— and threaded stainless hydro check —spring-loaded piston—. CF8M is the cast equivalent of 316: it is chosen for corrosion resistance against chlorides, chemicals, ammonia and coastal environments, or for material traceability requirements, not for extra pressure. The reference rating published for the stainless line is 200 WOG; the exact MSS SP-80 class per reference is not published by the manufacturer and is confirmed on quotation.

SKU VT-87050 (vertical stainless check) · line of 3 threaded NPT check valve references in cast stainless steel ASTM A351 CF8M

1. Technical specifications

Materials by component (stainless line)

CF8M composition and its equivalence with 316 per ASTM A351. The exact grade of the closure member and spring and the seat type per figure are manufacturer data for each reference: confirmed on quotation or in the PDF sheet attached to the product. An NPT thread is not a sanitary connection: for CIP-cleaned service the TECTUL catalog offers a sanitary stainless check reference with clamp ends, outside the scope of this sheet.

Regulatory framework and supply conditions

Threaded stainless check references in the TECTUL catalog

The vertical check and the stainless gate check have a factory PDF sheet attached to their product page; the stainless threaded hydro check is published without variants, and its sizes, pressure and lead time are confirmed on quotation. Face-to-face dimensions, height and weight are not standardized for threaded valves of this type — each manufacturer sets its own pattern — and are confirmed on quotation.

2. Rating of the stainless line: 200 WOG within the MSS SP-80 dual system

The only pressure value the manufacturer publishes for its threaded stainless line in this catalog is 200 WOG (13.8 bar cold). It is taken as the reference rating of the line, not as a certified rating of each figure: the exact MSS SP-80 class per reference is not published by the manufacturer and is confirmed on quotation.

Read within the MSS SP-80 dual class system, 200 WOG corresponds to Class 125, which links that cold number to a saturated steam limit of 125 psig:

¹ Steam saturation temperature at the stated SWP: a thermodynamic property of water, not of the valve. It is the same reference value used by ASME B16.3-2021 (Table 3-1, note 1) for the 186 °C limit of Class 150 threaded fittings. WOG is not an ASME B16.34 class, and no "Class 200 WOG" exists in that standard: it is a number declared by the manufacturer in accordance with MSS SP-80.

Two ideas that get mixed up in the field should be kept apart: pressure rating and corrosion resistance are independent. Moving from bronze to CF8M does not by itself raise the allowable pressure number —that is set by the class of the figure, not by the metal—; what changes is the range of fluids and environments in which the valve survives. That is the selection criterion in section 4.

3. Mounting position matrix of the three designs

The mechanism that closes the port —axial guiding, gravity or spring— defines the orientation in which each check valve works reliably. This stainless line has one peculiarity compared with the bronze one: it includes a single-position design. This is the matrix of the three threaded CF8M references in the TECTUL catalog.

Classification by mechanism family (axial guiding, gravity gate and spring-loaded piston), applying general check valve installation practice. The admissible position of each figure and the flow direction are defined by the manufacturer: the arrow cast on the body and the product PDF sheet override this table.

Why the vertical check only works vertically with upward flow

In this design the disc travels along its own axis, guided by the body, and returns to the seat by gravity when the flow drops. That guided travel requires the disc axis to coincide with the vertical: if the valve is laid down, the disc starts sliding sideways on the guide, its weight no longer pushes it against the seat, and closing is left to the push of the return flow; in the worst case the disc jams on the guide and the valve stays open. That is why the reference is called vertical and does not accept horizontal mounting.

Why a gravity check valve installed with downward flow loses its function

On the stainless gate check, the force that returns the gate to the seat is its own weight, and that weight only does its job if it acts opposite to the flow: hence the admissible mounting is horizontal —the gate falls onto the seat— or vertical with upward flow —it falls against the stream—. With downward flow, gravity and the fluid push in the same direction, the opening one: the gate rests on the open stop and, when flow stops, nothing brings it back to the seat. The valve stays permanently open and the return flow passes freely. This is the most common field error with this family and the network pressure test does not reveal it: it shows up when the pump stops or the tank drains through the filling line.

Field rules

• The arrow cast on the body indicates the flow direction, not the mounting position: complying with the arrow does not guarantee correct orientation.
• If the line runs vertically upward, the vertical check is the natural reference; if the line is horizontal, the reference is the stainless gate check or a spring design, never the vertical check laid down.
• Leave a straight run upstream, free of elbows, pumps and immediate reducers, so the disc works with steady flow and does not chatter against the seat.
• Size by the service flow rate and not by the pipe diameter: an oversized check valve works with the disc partly open and wears the seat (Crane TP-410 minimum full-lift velocity principle; the specific coefficient depends on the check type and the manufacturer).
• On stainless steel, avoid thread galling during assembly: suitable sealant, tightening by torque rather than by turns, and clean threads.
• A check valve is not an isolation valve: to work on the line, an isolation valve is installed upstream.

4. When the check valve must be stainless rather than bronze

The reason to move from a bronze check valve to a CF8M one is corrosion resistance, not extra pressure. The rating is set by the class of the figure (section 2), not by the metal: a Class 125 stainless check valve takes the same 200 psi cold as a Class 125 bronze one. What changes is where it survives.

Cases where stainless steel is the right call

Where stainless steel is not the answer

• It is not extra pressure. If the problem is that the network works above the available class, the answer is not changing metal but moving up a class or to a flanged or forged steel line, each with its own data sheet.
• 316/CF8M is not immune to chlorides. In concentrated brines or hot seawater there is a risk of pitting and chloride stress corrosion cracking; that scenario calls for duplex or superaustenitic alloys and must be defined by the project engineer.
• An NPT thread is not a sanitary connection. For CIP-cleaned service, polished surfaces and finish traceability, a threaded connection does not apply: the TECTUL catalog offers a sanitary stainless check reference with clamp ends.
• Cost. On potable water, compressed air and non-corrosive oils, bronze does the job at lower cost; stainless steel is justified by the fluid or the environment, not by default.

5. Frequently asked questions

Can the vertical stainless check valve be installed horizontally?

No. It is the only design in the family with no horizontal variant: the disc is guided along its axis and returns to the seat by gravity, so the valve only works on vertical piping with upward flow. Laid down, the disc slides sideways on the guide and closing is no longer reliable. For a horizontal line the stainless gate check or a spring design is the right reference.

When is a stainless check valve preferable to a bronze one?

When the fluid or the environment attacks copper: chlorides, brackish water, chemicals and condensates, ammonia, coastal environment, or when the specification requires stainless material with a heat certificate for sanitary or food traceability. On potable water, compressed air and non-corrosive oils, bronze does the job at lower cost. The detail is in section 4.

Does stainless steel take more pressure than bronze?

Not for being stainless. The rating is set by the MSS SP-80 class of the figure, not by the metal: a Class 125 stainless check valve takes the same 200 psi cold as a Class 125 bronze one. The reason to choose CF8M is corrosion resistance.

What pressure does the stainless check valve in this catalog have?

The reference rating published by the manufacturer for its threaded stainless line is 200 WOG (13.8 bar cold, up to 38 °C), equivalent to Class 125 of the dual system, whose saturated steam limit is 125 psig at ≈178 °C. The exact class of each of the three references is not published by the manufacturer and is confirmed on quotation.

Is the threaded stainless check valve suitable for a food line?

It depends on the specification. CF8M is the cast equivalent of 316 and is certified under ASTM A351, but the NPT threaded connection is not a sanitary connection: it allows no CIP cleaning and guarantees no internal finish. If the process requires sanitary design, the catalog's sanitary stainless check reference with clamp ends is the right one.

6. Application notes

7. Technical notice and limitation of liability