INDUSTRY COMPONENT

Bonnet

A bonnet is a protective cover component in steam generator pressure relief valves that houses internal mechanisms and provides structural integrity.

Component Specifications

Definition
The bonnet is a critical housing component in steam generator pressure relief valve assemblies, designed to enclose and protect the valve's internal working parts such as the stem, spring, and disc. It provides structural support, maintains pressure integrity, and often serves as an attachment point for adjustment mechanisms. In industrial applications, bonnets are engineered to withstand high temperatures and pressures while preventing leakage and ensuring reliable valve operation.
Working Principle
The bonnet functions as a sealed housing that contains the pressure relief valve's internal components. It maintains a pressure-tight environment while allowing for the transmission of force from the adjustment mechanism to the valve disc. During operation, the bonnet withstands system pressure and provides a mounting surface for the valve spring and stem assembly, ensuring proper alignment and function of the pressure relief mechanism.
Materials
Typically manufactured from forged or cast carbon steel (ASTM A105, A216 WCB), stainless steel (ASTM A351 CF8/CF8M), or alloy steels. High-temperature applications may use chrome-molybdenum alloys. Materials must meet pressure vessel codes and corrosion resistance requirements.
Technical Parameters
ParameterTypical rangeNotes & selection driver
Leakage ClassANSI/FCI 70-2 Class IV or better
Surface FinishRa 3.2 μm or better
Connection TypeFlanged, threaded, or welded
Pressure RatingASME Class 150-2500
Design StandardsASME B16.34
Temperature Range-20°C to 425°C

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards
ISO 4126-1, ASME B16.34, API 526, DIN 3320

Parent Products

This component is used in the following industrial products

Engineering Analysis

Risks & Mitigation
  • Stress corrosion cracking
  • Thread galling during assembly
  • Seal failure under thermal cycling
  • Material degradation at high temperatures
FMEA Triads
Trigger: Improper material selection for operating conditions
Failure: Cracking or deformation under pressure
Mitigation: Use materials certified for specific temperature/pressure ranges and conduct regular NDT inspections
Trigger: Incorrect assembly torque
Failure: Thread damage or leakage
Mitigation: Follow manufacturer torque specifications and use calibrated torque wrenches

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance
Dimensional tolerances per ASME B16.34, pressure testing to 1.5x design pressure
Test Method
Hydrostatic pressure test, helium leak test, dimensional verification, material certification

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation
Request current drawings, revision history, and a signed specification sheet.
Manufacturing capability
Verify equipment lists, process limits, capacity, and representative production evidence.
Inspection readiness
Confirm test methods, calibrated equipment, sampling plans, and traceable reports.
Supplier transparency
Check the legal entity, factory address, ownership, certifications, and direct contacts.

CNFX does not score or rank suppliers. Buyers must verify all claims and documents with the legal manufacturer before ordering.

Manufacturers of Bonnet

Manufacturer profiles associated with Bonnet.

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Frequently Asked Questions

What is the primary function of a bonnet in pressure relief valves?

The bonnet serves as a protective housing that contains internal valve components, maintains pressure integrity, and provides structural support while allowing for adjustment of the relief pressure setting.

Can bonnets be interchanged between different valve manufacturers?

Generally not recommended due to differences in design, dimensions, and pressure ratings. Bonnets are typically designed as integral components of specific valve models and should only be replaced with OEM-approved parts.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

Preliminary Technical Classification
This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

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Bonding Interface Bonnet Flange
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