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Application Guide

Valves for Ammonia & Fertiliser Plants

Ammonia synthesis and fertiliser manufacturing demand valves that withstand extreme pressure (150–300 bar synthesis loop), cryogenic NH₃ storage (−33°C), and highly corrosive urea melt (185°C). Vajra Industrial Solutions supplies the complete valve range — from synthesis loop block valves to urea high-pressure stripper isolation, prilling tower controls, and IBR-certified steam valves for the cogeneration plant — with NACE MR0103 and API 526 compliance documentation.

API 6DAPI 526 (PSV)NACE MR0103ASME B16.34API 598IBR (Steam Valves)IS 2825
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Recommended Valve Types for Ammonia & Fertiliser Plants

Gate Valve (A217 WC9)

Class 600 / 900 / 1500

Why: High-temperature, high-pressure synthesis loop isolation; hydrogen service at 200–300 bar

Materials: A217 WC9 (Cr-Mo alloy steel), A182 F22 forged for smaller sizes

Standards: API 600, ASME B16.34, API 598

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Ball Valve (A350 LF2)

Class 150 / 300

Why: Cryogenic liquid ammonia storage (−33°C) — extended bonnet, anti-static, fire-safe

Materials: A350 LF2, A182 F316L for urea service; PTFE seats rated to −46°C

Standards: API 6D, API 607, BS 6364 (cryogenic)

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Safety Relief Valve

Class 300 / 600 / 900

Why: Synthesis loop, NH₃ storage sphere, and urea reactor overpressure protection per API 526

Materials: A351 CF8M (SS316), A216 WCB with Stellite trim for high-cycle service

Standards: API 526, API 527, ASME Section VIII

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Globe Valve (IBR)

Class 300 / 600

Why: Steam service on cogeneration boiler — IBR Form III-C/III-E certification mandatory

Materials: A216 WCB to Class 600; A217 WC6/WC9 for high-temperature steam above 425°C

Standards: IBR 1950, ASME B16.34, IS 9395

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Critical Requirements

Hydrogen service valves must comply with NACE MR0103 (refinery sour service) — hardness limits on body, trim, and fasteners
Ammonia service — extended bonnets for cryogenic applications below −29°C; fire-safe design per API 607
Urea melt valves — SS316L trim with PTFE packing; no copper-based alloys (urea attacks copper)
IBR certification for all steam valves above 3.5 kg/cm² — Form III-C material cert and Form III-E hydraulic test
API 526 compliance for all pressure safety valves; back-pressure correction for superimposed back-pressure
Anti-static and fire-safe design for liquid NH₃ storage valves — API 607 7th edition minimum

Fluid & Service Challenges

⚠Anhydrous ammonia (NH₃) — corrosive to copper, zinc, and brass; requires steel or SS; stress corrosion cracking in high-strength steels
⚠Synthesis loop gas (N₂/H₂ 75:25) at 150–300 bar — hydrogen embrittlement risk; Nelson curve compliance per API 941
⚠Urea melt at 185°C — hydrolysis produces carbamate and CO₂; requires SS316L wetted parts
⚠Liquid CO₂ and carbamic acid in stripper — highly corrosive; duplex or SS316L minimum
⚠Steam at 40–100 bar — IBR compliance mandatory for all Indian plants

Material Selection Guidance

Synthesis loop (H₂ + N₂, 200–300 bar): A217 WC9 (Cr-Mo) gate valves — confirmed against API 941 Nelson curves for hydrogen service at elevated temperatures. Liquid ammonia storage: A350 LF2 carbon steel with NACE MR0103 HRC ≤22 hardness limit. Urea reactor/stripper: SS316L (A182 F316L forged; A351 CF3M cast) — no carbon steel in urea melt service. Steam: WCB to 425°C / WC6 to 540°C / WC9 to 595°C with IBR certification.

Typical Service Points

Ammonia synthesis loop — converter inlet/outlet, quench, feed isolation (150–300 bar, 400–500°C)
Liquid ammonia storage spheres/bullets — pump suction/discharge, transfer, loading/unloading (−33°C, 14 bar)
Urea high-pressure loop — stripper, carbamate condenser, reactor recirculation isolation (150 bar, 185°C)
Prilling tower scrubber — dilute NH₃ solution, wash water (low pressure, SS316L)
Cooling water and utility systems — carbon steel gate valves, butterfly valves
Steam header and cogen boiler — IBR gate/globe/check valves (40–100 bar, 480–540°C)

FAQ — Valve Selection for Ammonia & Fertiliser Plants

What valve material should I use for anhydrous ammonia service?
For liquid ammonia (−33°C to ambient), use A350 LF2 carbon steel body with PTFE seats and SS316 trim — no copper, brass, or zinc alloys. For synthesis loop gas (H₂/N₂ at 150–300 bar), use A217 WC9 (Cr-Mo alloy) gate valves verified against the API 941 Nelson curves for hydrogen attack. For urea melt (185°C, 150 bar), SS316L is mandatory — carbamate in the loop attacks carbon steel rapidly.
Do ammonia plant valves need NACE MR0103 certification?
NACE MR0103 (Materials Resistant to Sulfphide Stress Cracking in Corrosive Petroleum Refining Environments) applies when H₂S is present — common in ammonia plants using natural gas feedstock via desulphurisation. Key requirement: body and trim hardness ≤ HRC 22 (Rockwell C). If your feedstock is H₂S-free coal or electrolysis, NACE may not be mandatory, but most licensors (Haldor Topsoe, KBR, Casale) specify it as a precaution.
What PSV standard applies to ammonia plant pressure relief valves?
API 526 governs flanged steel pressure relief valves. It specifies standard orifice sizes (D through T), inlet/outlet flange ratings, and material requirements. For ammonia synthesis loop (Class 2500 inlet), use A351 CF8M (SS316 cast) bodies with Stellite trim for high-cycle hot service. API 527 governs seat tightness testing. Back-pressure above 10% of set pressure requires balanced-bellows or pilot-operated design.
Is IBR certification required for fertiliser plant steam valves?
Yes. In India, the Indian Boiler Regulations (IBR) 1950 mandate that all valves on steam lines at pressure above 3.5 kg/cm² (0.35 MPa) carry IBR Form III-C (material test certificate) and Form III-E (hydraulic test certificate). Fertiliser plants typically operate steam at 40–100 bar for turbine drives and process heating — all such valves must be IBR-certified. Vajra supplies IBR gate, globe, and check valves with full Form III documentation.

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Ammonia & Fertiliser Plants

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Key Standards

API 6D
API 526 (PSV)
NACE MR0103
ASME B16.34
API 598
IBR (Steam Valves)
IS 2825

Products for This Application

Ball ValvesGate ValvesGlobe ValvesSafety & Relief Valves

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