Disc and Seat: Set Pressure Range 0.1-25 MPa

Component Specifications

Definition

The disc and seat form the primary sealing mechanism in a steam generator pressure relief valve assembly. The disc is the movable component that lifts off the stationary seat to allow steam discharge when system pressure exceeds the set point, then reseals against the seat when pressure normalizes. This interface must maintain leak-tight closure under normal operating conditions while providing reliable, repeatable opening during overpressure events.

Working Principle

The disc is held against the seat by spring force or system pressure during normal operation. When upstream pressure exceeds the set pressure, the resulting force overcomes the spring force, lifting the disc from the seat to create a flow path for steam discharge. As pressure decreases below the reseat pressure, the spring force returns the disc to contact with the seat, re-establishing the seal.

Materials

Typically manufactured from corrosion-resistant alloys such as stainless steel (AISI 316, 17-4PH), Inconel 718, or Stellite for high-temperature steam applications. Hard-facing materials like tungsten carbide may be applied to sealing surfaces for enhanced wear resistance.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Leakage Class	ANSI/FCI 70-2 Class IV or better
Surface Finish	Ra ≤ 0.4 μm on sealing surfaces
Flatness Tolerance	≤ 0.0005 mm/mm
Set Pressure Range	0.1-25 MPa
Operating Temperature	Up to 400°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 BPVC Section VIII, API 526

Parent Products

This component is used in the following industrial products

Steam Generator Pressure Relief Valve Assembly

Safety valve assembly for industrial steam generators that prevents overpressure conditions.

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Engineering Analysis

Risks & Mitigation

Seal failure leading to continuous leakage
Sticking or binding preventing proper operation
Erosion reducing sealing effectiveness
Corrosion compromising material integrity

FMEA Triads

Trigger: Contaminant accumulation on sealing surfaces
Failure: Prevent proper disc-seat contact, causing leakage
Mitigation: Implement regular cleaning procedures and install upstream strainers

Trigger: Thermal stress from rapid temperature changes
Failure: Warping or cracking of disc or seat components
Mitigation: Use materials with matched thermal expansion coefficients and implement controlled warm-up procedures

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Dimensional tolerances per ASME Y14.5, sealing surface flatness within 0.0005 mm/mm, surface roughness Ra ≤ 0.4 μm

Test Method

Hydrostatic testing per ASME BPVC Section VIII, seat leakage testing per API 527, set pressure verification using certified test stands

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 Disc and Seat

Manufacturer profiles associated with Disc and Seat.

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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 causes disc and seat wear in pressure relief valves?

Primary wear mechanisms include erosion from high-velocity steam flow during discharge, corrosion from chemical contaminants in steam, galling from metal-to-metal contact during operation, and thermal cycling effects that cause material degradation.

How often should disc and seat components be inspected?

Visual inspection should occur during routine maintenance shutdowns (typically annually). Dimensional inspection and leakage testing should be performed according to manufacturer recommendations or regulatory requirements, usually every 12-24 months depending on service conditions.

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.

Disc and Seat