ASTM A105 Blind Flange

QS Flange: ASTM A105 BL Flange

ASTM A105 forged steel blind flange, 1-1/4 inch Class 150LB raised face per ASME B16.5, black anti-rust coated, for closing pipeline ends and vessel nozzles.

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One-Minute Overview

Solid ASTM A105 forged disk that closes a 1-1/4 inch Class 150LB flange joint.
Raised face sealing surface machined to ASME B16.5 dimensions, with no bore through the plate.
Black anti-rust coating keeps the machined faces sound through storage and humid sites.
Suits pipeline fittings, pressure vessels, water works, power stations and general industry.

The ASTM A105 BL flange is a blind flange: a solid disk with no bore, bolted across a pipe end or a vessel nozzle to stop flow completely. Forged in ASTM A105 carbon steel and machined to ASME B16.5, this 1-1/4 inch Class 150LB part carries a raised face and a black anti-rust coating.

Name: ASTM A105 BL Flange
Size: 1-1/4 Inch
Class: 150LB
Material: ASTM A105
Flange Face: Raised Face
Standard: ASME B16.5
Process: Forged Steel
Coating: Black Anti-rust Coating
Feature: Strong Stiffness, Good Sealing
Usage: Pipeline Fittings, Industry, Pressure Vessels, Water Conservancy, Electricity, Power Stations

A blind flange does one job without a gasket path through the bore: it terminates a line. You will find it on the end of a header waiting for a future tie-in, on a test port opened once a year, on a vessel manhole or drain nozzle, or across a valve during a shutdown. Because the plate is solid, the pressure boundary is the plate itself plus the gasket joint around it, which is why the two features listed for this part, strong stiffness and good sealing, are the ones that matter.

Stiffness keeps the plate flat under bolt load, so the raised face stays in even contact with the gasket instead of bowing away at the centre. Good sealing comes from that flat machined face and from the finish on it. Tighten the bolting in a cross pattern in stages, the way you would any flange joint of this class, and check the gap between the faces as you go.

The black anti-rust coating is a temporary protection for the machined surfaces: leave it in place until the joint is made up, then touch up any bare patch on the outside with a suitable coating. Store the flange face up on timber rather than resting on the raised face, so the sealing surface arrives on site as flat as it left the works.

FAQ

Q1. So what does a blind flange actually do?

It closes a pipe end. There is no bore through the plate, so nothing passes; the joint is sealed by the gasket between the raised face and the mating flange. You use it to terminate a line, to blank a future tie-in, to close a vessel nozzle or to isolate a section during maintenance.

Q2. How should the raised face be treated before bolting up?

Keep it covered until the last moment, wipe off the anti-rust coating and any grit, and check for nicks or burrs. A damaged face will leak whatever the bolt load. Fit the gasket the service calls for, bring the flanges together square, then tighten in a cross pattern in stages.

Q3. Why specify A105 rather than a plain mild steel plate?

ASTM A105 is a carbon steel specified for forged piping components rather than for structural plate, and this part is forged to that specification instead of being cut from sheet. Forging closes internal voids and gives the disk the stiffness it needs to stay flat under bolt load and thermal cycling in pipeline, vessel and power station duty.

Q4. What is the smallest order I can place?

Standard flange insulation gasket kits start at one set, and standard gaskets, studs, washers and sleeves start at one piece. Parts made to your drawing or to a non-standard bolt pattern are quoted one by one, because the minimum really depends on the material and the tooling involved.

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