If you already know the required size, pressure class, end connection, and process conditions, review the Alloy 20 globe valve product page or send the data directly for technical review.

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Why Alloy 20 Is Considered for Sulfuric-Acid Service

Alloy 20 is a nickel-iron-chromium alloy identified as UNS N08020 and EN 2.4660. Its chemistry includes copper and molybdenum, and the alloy was developed for resistance in sulfuric-acid environments. It is also used in selected chemical processing, pickling, fertilizer, pharmaceutical, and process-piping applications.

That description is a starting point, not a universal approval. Concentration, temperature, aeration, oxidizing contaminants, chlorides, solids, flow velocity, crevices, and cleaning chemicals can change corrosion behavior. A material that performs well in one sulfuric-acid condition may be unsuitable in another.

First Decide the Valve Duty: Isolation or Throttling

A globe valve uses linear stem movement to position a disc or plug against a seat. Compared with a gate valve, its flow path creates a higher pressure drop, but the geometry is better suited to regulated flow. This does not mean every standard globe valve is automatically a control valve.

Seven Items to Put on an Alloy 20 Globe Valve RFQ

1. Fluid composition and operating envelope

State the chemical name, concentration range, contaminants, solids, pH if relevant, and whether aeration or cleaning chemicals are present. Provide normal, minimum, maximum, and design pressure and temperature. For acid service, concentration and temperature should be supplied together rather than as separate general values.

2. Size, rating, and end connection

Specify NPS or DN, ASME Class or PN, and the required end connection. For flanged valves, define RF or RTJ facing and the applicable dimensional standard. For butt-weld ends, provide pipe material, schedule, bore, and any required transition details. Do not select a pressure class without checking the exact material and design temperature.

3. Design and dimensional standards

State the required design basis and edition. ASME B16.34 covers pressure-temperature ratings and general requirements for valves within its scope, while API 623 applies to a heavy-duty series of bolted-bonnet steel globe valves with flanged or butt-welding ends. Face-to-face requirements, testing, project specifications, and regional conformity requirements should be listed separately.

4. Complete material schedule

Define the body and bonnet material form and specification, then list the disc or plug, seat or seat ring, stem, hardfacing, bolting, gasket, and packing. A commonly associated cast grade for Alloy 20 service is ASTM A351 CN7M, while wrought or forged components follow their applicable specifications. The final component specification must match the valve design, size, rating, and code requirements.

5. Seat, packing, and emissions requirements

State whether the seat is metal or soft, the required leakage class or acceptance criterion, packing material, live loading if required, and any project fugitive-emission qualification. These details are especially important when the fluid is hazardous or when the valve will cycle frequently.

6. Operation and actuator data

For manual operation, define handwheel or gearbox requirements and any access limitations. For pneumatic or electric actuation, include available utilities, control signal, fail position, enclosure or area classification, accessories, required stroke time, and the process differential pressure used for actuator sizing.

7. Inspection, testing, and documentation

List the pressure-test standard and acceptance criteria, PMI scope, material certificates, NDE, corrosion testing if applicable, inspection hold points, third-party witnessing, marking, drawings, and final documentation dossier. If an EN 10204 3.1 certificate or a project-specific inspection and test plan is required, state it on the RFQ rather than after order placement.

Minimum Process Data for Throttling Review

Common Specification Mistakes

• Writing only “Alloy 20 globe valve” without identifying component material specifications.
• Providing acid concentration without the temperature range or contaminants.
• Assuming a throttling application can be selected from pipe size alone.
• Using pressure class as a substitute for a verified pressure-temperature rating.
• Omitting shutoff, leakage, packing, or fugitive-emission requirements.
• Requesting certificates or third-party inspection only after production has started.

Frequently Asked Questions

Is Alloy 20 suitable for every sulfuric-acid concentration?

No. Its performance depends on concentration, temperature, contaminants, aeration, velocity, crevices, and the fabrication and heat-treatment condition. Confirm compatibility using process-specific corrosion data and the end user’s materials engineering requirements.

Can an Alloy 20 globe valve be used for flow control?

It can be engineered for throttling, but pipe size alone is not enough. The supplier needs flow cases, pressure drop, fluid properties, temperature, valve characteristic, allowable noise, cavitation or flashing review, and actuator requirements.

Does “Alloy 20 body” mean all wetted parts are Alloy 20?

Not necessarily. The trim, stem, seat, hardfacing, packing, gasket, and bolting may use different materials. Request and review the complete bill of materials.

What should be sent for a quotation?

Send the fluid and concentration, contaminants, design and operating pressure and temperature, valve size and rating, end connection, isolation or throttling duty, required materials, operation method, testing, documentation, quantity, and delivery destination.