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Application Guide

Valves for Ethylene Crackers & Olefin Plants

Ethylene crackers span the widest temperature range of any process plant — from +900°C pyrolysis furnace outlet to −165°C demethaniser column overhead. This demands completely different valve materials and designs at each point in the flowsheet. Vajra Industrial Solutions supplies WC9 and F22 Cr-Mo alloy gate valves for furnace crossover and quench systems, SS316L cryogenic extended-bonnet ball and gate valves for the cold train, and API 526 spring-loaded PSVs for all pressure relief duties from cracked gas compressor to refrigeration system.

ASME B16.34API 600 (High-Temp Gate)API 6DAPI 526 (PSV)API 941 (Nelson Curves)NACE MR0103IBR (Steam)
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Recommended Valve Types for Ethylene Crackers & Olefin Plants

Gate Valve (A217 WC9)

Class 600 / 900

Why: Pyrolysis furnace crossover and TLE (Transfer Line Exchanger) inlet isolation — 600–900°C service

Materials: A217 WC9 (2.25Cr-1Mo); A182 F22 forged for smaller sizes; Stellite 6 trim

Standards: API 600, ASME B16.34, API 941 (Nelson curves for H₂ service)

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Cryogenic Ball Valve (SS316L)

Class 300 / 600

Why: Demethaniser, deethaniser column overheads (−100°C to −165°C); ethylene/propylene refrigeration

Materials: A182 F316L forged body; PCTFE or PTFE seats rated to −196°C; extended bonnet per BS 6364

Standards: BS 6364, API 607, API 6D

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Safety Relief Valve

Class 300 / 600 / 900

Why: Cracked gas compressor, refrigeration system, depropaniser and product headers overpressure protection

Materials: A351 CF8M SS316 for cryogenic; A216 WCB for hot service; Stellite trim for high-cycle

Standards: API 526, API 527, ASME Section VIII Div. 1

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Globe Valve (Control)

Class 300 / 600

Why: Dilution steam control, quench oil recirculation, and product rundown control

Materials: A216 WCB with SS316 trim; A217 WC9 for high-temperature steam service

Standards: API 623, ASME B16.34, IEC 60534 (control valves)

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Critical Requirements

Furnace crossover and TLE outlet valves — WC9 or WC11 material required above 550°C; confirm Nelson curve compliance per API 941 for H₂ service
Cold train valves below −29°C — extended bonnet (minimum 350 mm bonnet extension per BS 6364) to prevent ice formation at packing; cryogenic-grade PTFE/PCTFE seats
Diene and acetylene service — no copper alloys (acetylene forms explosive copper acetylide); SS316 or carbon steel only
Dilution steam — IBR certification for all steam header valves in Indian plants
API 526 PSVs must be installed without block valves unless full-bore, car-sealed-open alternative is provided per API 520
Anti-surge valves on cracked gas compressors — fail-open design; fast-acting actuator (< 2 seconds full stroke)

Fluid & Service Challenges

⚠Cracked gas (ethylene, propylene, H₂, CH₄) — extremely wide composition; hydrogen in mixture requires API 941 compliance for carbon/Cr-Mo steel
⚠Pyrolysis furnace outlet (900°C) — above carbon steel Nelson curve limit; Cr-Mo alloy mandatory
⚠Liquid ethylene at −104°C and liquid propylene at −47°C — cryogenic extended bonnets; impact testing mandatory
⚠Dilution steam with trace pyrolysis by-products — deposition; SS316 trim to prevent coke fouling around valve seat
⚠Fuel oil for furnace — high viscosity; heated trace required; ball valves with hollow-ball blowout risk

Material Selection Guidance

Furnace outlet and crossover (>500°C): A217 WC9 (2.25Cr-1Mo) for Class 600–900. Cold train (−100°C to −165°C): A182 F316L forged body with BS 6364 extended bonnet — CMTR required confirming Charpy impact ≥ 27 J at −196°C. Cracked gas at moderate temperature: A216 WCB (to 425°C) or A352 LCB (to −46°C) with SS316 trim. Dilution steam: A216 WCB with IBR Form III for Indian plants.

Typical Service Points

Pyrolysis furnace feed and effluent — gate and globe valves (WC9, 600–900°C, Class 600–900)
Quench oil tower — large-bore butterfly valves and globe control valves
Cracked gas compressor — anti-surge globe valve (fast-acting), suction/discharge block valves
Cold box and demethaniser — cryogenic SS316L ball and gate valves (−165°C, Class 300–600)
C2 and C3 splitters — SS316L ball valves; PSVs on reflux drums
Product rundown and storage — ball valves for liquid ethylene (cryogenic extended bonnet)

FAQ — Valve Selection for Ethylene Crackers & Olefin Plants

What valve material should I use for ethylene cracker furnace crossover?
The pyrolysis furnace crossover operates at 600–900°C — well above the carbon steel Nelson curve for hydrogen service. Specify A217 WC9 (2.25Cr-1Mo) gate valves for Class 600–900 service at these temperatures. For smaller bore instrument connections at the furnace, A182 F22 forged (same Cr-Mo alloy) is used. Confirm compliance with API 941 Nelson curves: WC9 is acceptable up to 600°C at 70 bar H₂ partial pressure without creep concerns.
What is a BS 6364 extended bonnet and when is it required?
BS 6364 is the British Standard for Valves for Cryogenic Service. It specifies that valves handling fluids below −29°C must have an extended bonnet — a lengthened bonnet neck (typically 350–600 mm) that keeps the gland packing and actuator above the cryogenic zone. Without this extension, ice forms at the gland seal, causing leakage and potential valve seizure. Extended bonnets are mandatory for liquid ethylene (−104°C), liquid propylene (−47°C), LNG (−162°C), and liquid nitrogen (−196°C) service.

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Ethylene Crackers & Olefin Plants

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Key Standards

ASME B16.34
API 600 (High-Temp Gate)
API 6D
API 526 (PSV)
API 941 (Nelson Curves)
NACE MR0103
IBR (Steam)

Products for This Application

Ball ValvesGate ValvesGlobe ValvesSafety & Relief Valves

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