ASME B16.48 Spectacle Blind Flange

QS Flange: ASME B16.48 Spectable Blind Flange

ASME B16.48 spectacle blind, 3/4 inch Class 1500LB raised face at STD thickness, in A516N Gr.70 S5, for switching a line between open and blocked.

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One-Minute Overview

Spectacle blind that swings a joint between fully open and fully blocked.
Made to ASME B16.48 in 3/4 inch, 1500LB class, raised face, STD thickness.
A516N Gr.70 S5 plate keeps the disk sound in high-pressure service.
One bolting break per change instead of two, so shutdown work runs shorter.

A spectacle blind is a one-piece plate that lets a flange joint be opened or blocked without pulling the bolting apart twice: one end carries the solid blind, the other stays open, and the plate is swung on a bolt to change state. This one is a 3/4 inch, 1500LB, raised face part of STD thickness, made to ASME B16.48 from A516N Gr.70 S5 plate.

Name: ASME B16.48 Spectacle Blind Flange
Size: 3/4 Inch
Pressure: 1500 LB
Material: A516N Gr.70 S5
Thickness: STD
Type of Face: Raised Face
Standard: ASME B16.48
Feature: Easy and Quick Installation
Usage: Pipeline Fittings, Industry, Pressure Vessels, Water Conservancy, Electricity, Power Stations

The point of a spectacle blind is the changeover. A line isolated for a shutdown and then returned to service normally needs the blind pulled, a spacer fitted and the joint remade: twice the work and twice the chance of a bad gasket. With this plate the solid end and the open end sit on the same web, so you break the bolting once, swing the plate, retighten. That is where the feature listed for this part, easy and quick installation, actually pays off, and it pays off at the flange on the day of the shutdown.

At 1500LB the joint is a high-pressure one, so thickness is not a detail. This plate is supplied at STD thickness to ASME B16.48, and the standard fixes the plate geometry and the clearances around the bolting so the blind swings between standard flanges of the matching size and class without fouling the studs. The raised face has to be flat, clean and free of burrs before the gasket goes in, because a heavy class leaves very little tolerance for a poor face.

A516N Gr.70 S5 is a pressure vessel plate grade, chosen here for a disk that must hold its shape under a heavy class. Line the plate up so the open end clears the bore when the line is running, and leave the handle or a tag visible so anyone walking past can read the position at a glance. Service covers pipeline fittings, industrial plant, pressure vessels, water conservancy and power stations.

FAQ

Q1. Which standard and thickness does this blind follow?

The plate is made to ASME B16.48 in 3/4 inch and a 1500LB class, with a raised face and STD thickness. That standard fixes the plate dimensions and the clearances around the bolting, so the blind fits between standard flanges of the same size and class and swings without fouling the studs.

Q2. 1500LB is a serious class, what does that change in practice?

Everything downstream of the gasket. The plate is thicker, the bolting is heavier and the joint is far less forgiving of a dirty face or a reused gasket. Clean the raised face, fit a new gasket for the service, bring the flanges up square and tighten in a cross pattern in stages.

Q3. Can the plate really be changed over with the line still full?

Not on a live line. You change the plate position at a joint that is depressurised and drained. What you save is the second bolting break of a blind-and-spacer swap, so the window is shorter and the gasket is handled less. Confirm the section is isolated before you touch the bolting.

Q4. How long will production take?

Standard sizes are typically ready within 30 days, and in-stock items ship immediately. Larger or custom orders get a confirmed date per order, because the schedule depends on quantity, material, the bolt pattern you specify, and how busy production is at the moment you order.

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