Document EvMX8JpqNdnqYqdvZBK4841D4

a ' I! f il? i Insulation Handbook: Part 4 How to Apply 85% Magnesia Heat Insulation By PHll SWAIN, EDITOR WIRED SECTIONAL t i Here factory canvas is removed. Use at least 3 annealed iron wires per section. Twist wire ends together, bend over and press into insulation for protection. Stagger lengthwise joints. Point up all joints with 85% magnesia cement An alternate method omits wiring, pastes down laps on factory canvas and applies metal bands < 2 DOUBLE LAYER f Handle inner layer as before. Apply outer layer with all joints staggered. Outer layer may be wired without canvas like inner layer, or may be finished by pasting down factor! canvas and banding { i SEWED CANVAS JACKET If cost of better looking, more durable job is warranted remove factory canvas. Apply layers as above, followed bf rosin-sized or sheathing paper. Stretch 8-oz canvas over paper, sew in place, coat with glue sizing, paint as de* sired. To avoid scorching canvas finish by heat from nearby flanges or other uninsulated surfaces, stop canvas and paper a few inches short of insulation end. Finish eX; posed ends with asbestos cement i Wire mesh , PARALLEL PIPING ii } Block Insulating insulation cement in joints Where two parallel pipes1 are too close for convenient separate insulation, or where a steam pipe must protect a water pipe from freezing, or keep oil line warm, arrange ment pictured is convenient and practical 112 POWER juty ;v5C Practical know-how in convenient form. Drawings and con densed instructions summarize standard procedures in the 85% Magnesia Insulation Manual, published by the Magnesia Insulation Manufacturers7 Association, of Washington, D. C. LARGE VALVES To insulate valves of 4-inch pipe size or larger, build cover of block or sectional insulation of any convenient shape. Tie together with wires. Seal crevices with in sulating cement. Use solid insulation half-inch thinner than pipe insulation to allow for cement finish. Then build to full thickness with asbestos cement, 2 coats. % LARGE FITTINGS r Treat fittings, 4-inch and up, same as valves. Note: For valves and fittings under 4-inch, cover directly with : asbestos cement in several half-inch layers to bring total thickness up to that of pipe covering. Allow each coat to dry before applying the next Clearance / Insulating Supporting for bolts cement insulation block PERMANENT FLANGE INSOLATION ' Wire sectional insulation or blocks firmly in place and - cover with asbestos cement. Extend flange insulation at least >2 inches over adjacent pipe insulation. Fill open space /. (in overlap) with insulating material. Cut back and bevel pipe L'insulation to allow removing bolts H REPLACEABLE FLANGE INSULATION \ | ^Design pictured can be removed and replaced. Wrap sec.Stional insulation with wire mesh and finish with asbestos ement. Or build wire mesh in two halves, cover with blocks. ti&Cover this with wire mesh and cement inside and out OWER July 1950 ,For more insulation facts turn page+ HANDBOOK: PART 4 Continued, Two cobles STEEL DRUMS Where fuli circumference is not exposed, as with boiler drums, install firm anchorages. Fit blocks to cylinder, stag gering joints, and bind firmly with annealed iron wire laced through steel straps or wire cables DRUM HEAD Secure job requires anchoring blocks in manner shown, or f equivalent. Since curved blocks are not available to fit t round end of tank, pieces of flat block are used. These are e held in place by network of wires. Finish with asbestos f cement in one or several layers. .f HORIZONTAL TANK Horizontal tank pictured is completely encircled by in- sulation. Note that insulation in lower half tends to sag r from tank, so must be more firmly held in place. Angle 4 irons shown are one way. Asbestos cement finish { HORIZONTAL TANK END k Anchoring method, much like that for boiler-drum end \ but with more gradual curve, may allow use of full-size blocks. - Asbestos cement finish t DUCTS WITHOUT STIFFENERS Case pictured: breeching, duct or flue with no stiffeners i or other projections. Nor is any provision needed for r expansion. Blocks applied directly to surface and held by \ wire cables fir foetal straps. Metal beads protect corners ' POWER July >950 DUCT SURFACE WITH STIFFENERS When projections are far apart and there's no need to allow for expansion and contraction, wire blocks directly to surface and insulate stiffeners as pictured below STIFFENER INSULATION Half sections may be used to insulate stiffeners or other projections on ducts, shown above DUCTS WITH PROJECTIONS Where stiffeners or other projections are closely spaced, - or where you must allow for expansion or contraction, stretch heavy-iron-wire fabric over the projections to form a foundation. Then wire blocks in place and finish with asbes tos cement in the usual manner Corner bead Facts to Remember About 85% Magnesia - i AS THE NAME SUGGESTS, 85% magnesia contains not less than 85% of : magnesium carbonate. To this white, . : crystalline, extremely light insulating material, the makers add 15% of as'bestos fiber as a binder. : The wet mixture of magnesium car V bonate and asbestos fibers is shaped : first by molding and drying, then (usui. ally) by machining to commercial di 5 mensions. Usual commercial shapes are % split shells--called sectional insulation ,v\.--for piping, flat blocks, also curved r* blocks -- segmental insulation--to fit . v; large piping and tanks. The K Factor a rcent test of a commercial block v?6iof 85% magnesia, the U.S. Bureau of .-Jjfr.- -g&POWE* July 1950 Standards measured the density as 13.2 lb per cu ft. The K value (Btu transmitted per hr per sq ft for a temperature gradient of 1 deg F per inch of thickness) was 0.39 at 130 F mean temperature. This compares with MIMA values of 0.39 at 100 F mean temperature, 0.45 at 300 F, and 0.51 at 500 F. 85% magnesia insulation withstands temperatures up to 600 F without damage. Above 600 F the material be gins to calcine. It withstands repeated wetting and drying. For heated surfaces operating above 600 F, an 85% magnesium outer layer is customarily applied over an inner layer of high temperature insulation--usually "diatomaceous silica," molded with a binding component of asbestos fiber. Commercial thicknesses of sectional insulation and blocks include 1%, 2, 2V2, and 3 in. Sectional insulation is also available in graded sizes known as "standard" and "double standard." See table below: Insulation Thickness: Standard (S) And Double Standard (DS) Pipe size, nominal 1/2 to i-y2 2 to 3-y2 4 5 &6 8 & 10 12 and over 5 7/8 1-1/32 1% i-y8 i-y4 DS 1-29/32 2-5/32 2-y4 2-5/16 2-y2 3 115 I if