Bonnet Connection: Temperature Range -50°C to 600°C

Component Specifications

Definition

The bonnet connection is a precision-engineered mechanical interface that joins the valve bonnet to the valve body in regulating valves. It serves as the primary pressure boundary, preventing fluid leakage while allowing access for maintenance and internal component replacement. This connection typically incorporates gaskets, bolts, and sealing surfaces designed to withstand operational pressures, temperatures, and mechanical stresses. In regulating valve bodies, it ensures the actuator assembly remains securely attached while maintaining alignment with the valve trim for precise flow control.

Working Principle

The bonnet connection operates on the principle of creating a reliable pressure seal through mechanical compression. When bolts are torqued to specification, they compress a gasket between the bonnet and body flanges, forming a leak-tight barrier. The connection must maintain this seal under varying pressures, temperatures, and vibration while allowing controlled disassembly for maintenance. In regulating valves, it also provides structural support for the actuator stem and ensures proper alignment with the valve seat for accurate regulation.

Materials

Common materials include ASTM A216 WCB (carbon steel), ASTM A351 CF8M (stainless steel 316), ASTM A494 CW-6MC (nickel alloy), or duplex stainless steels like UNS S31803. Gaskets are typically spiral-wound (stainless steel with graphite/filler), ring-type joints (RTJ), or elastomeric seals (EPDM, Viton) depending on service conditions. Bolts are ASTM A193 B7 or B8M with corresponding nuts.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Seal Type	Gasketed, metal-to-metal, or O-ring
Bolt Torque	As per ASME PCC-1 guidelines
Surface Finish	Ra 3.2 μm or better for sealing surfaces
Connection Type	Bolted flange, threaded, or pressure seal
Pressure Rating	ANSI Class 150 to 2500
Temperature Range	-50°C to 600°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 5208, API 598, ASME B16.34, DIN EN 12516

Parent Products

This component is used in the following industrial products

Regulating Valve Body

The main structural housing of a regulating valve that contains and supports internal flow control components.

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Engineering Analysis

Risks & Mitigation

Gasket failure leading to leakage
Bolt fatigue or corrosion
Improper torque causing seal failure
Thermal expansion mismatch
Cyclic pressure causing joint fatigue

FMEA Triads

Trigger: Incorrect bolt torque during assembly
Failure: Uneven gasket compression leading to leakage
Mitigation: Use calibrated torque wrenches and follow cross-tightening patterns per manufacturer specifications

Trigger: Thermal cycling causing differential expansion
Failure: Loss of bolt preload and seal integrity
Mitigation: Select materials with compatible thermal expansion coefficients and consider spring washers for critical applications

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Flange flatness within 0.05 mm, bolt hole alignment within 0.5 mm, surface finish Ra ≤ 3.2 μm

Test Method

Hydrostatic testing per API 598/ISO 5208, helium leak testing for critical services, bolt torque verification using ultrasonic methods

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 Connection

1 company lists this product among what they make. Company figures are quoted from each company's own website; every card states where the relationship came from.

ZECO Valve

Wenzhou, Zhejiang, CN

Also makes: Butterfly Valve, Check Valve, Control Valve and 8 more

Listed on the company's own website · profile compiled by CNFX from public sources

Listed there as: “Bolted Bonnet Connection”
View source page ↗ zecovalve.com · checked 2026-09-14

View profile Send enquiry

Manufacturer listings support early research and capability understanding. They are not certification, ranking, or transaction guarantees.

Compiled and source-reviewed by the CNFX editorial team. Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review

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Frequently Asked Questions

What is the primary function of a bonnet connection in regulating valves?

The bonnet connection creates a pressure-tight seal between the valve bonnet and body, preventing fluid leakage while providing access to internal components for maintenance and ensuring proper actuator alignment for flow regulation.

How often should bonnet connections be inspected?

Inspect during routine maintenance cycles (typically 6-12 months) or when leakage is detected. Check for bolt torque, gasket condition, and surface integrity, especially after thermal cycling or pressure changes.

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.

Bonnet Connection