Overhaul and Salvage in Theory and Practice
Part VIII. — The ‘Tools’ of Salvage. . . . The ‘Cover’ or ‘Tarp’, . . . Is There Room for Improvement in Facilities? . . . Recent Developments
Editor’s Note: Previous installments of this series have covered all the preliminaries of the need for salvage; its history and development in the American and British Fire Service; its emergence from a fire insurance to a fire service facility and responsibility; the need for pre-fire salvage planning, and the importance of inspections as a prerequisite for better salvage operations.
In this Chapter the author gets down to the practical phases of salvage operations, beginning with the study of equipment and that prime requisite salvage tool, the salvage cover, or tarpaulin. Subsequent installments will further develop the varied and diversified mechanics of modern salvage practice.
It should be said here that some of the observations and prognostications of the author are his own tninking and do not necessarily represent at this time the considered viewpoint of any associations or groups of fire chiefs, or protection engineers. They are introduced by the author purely to inspire greater study and research in this most important field of fire waste reduction.
BY this time those who have followed this series of studies on salvage and overhaul should be pretty well convinced of its importance in the field of fire waste reduction and that it is a prime factor that should he included in all prefire planning, inspection and preparation for fire prevention and fire suppression.
Probably the first attempts of man to protect his possessions against damage by the elements was some sort of coverall. It is known that fire salvage work antedated any comprehensive attempts to extinguish fires, once they started. In fact, extinguishment, as practiced in the early days of Great Britain and this country, was conspicuous by its absence; instead, people concentrated on the removal of such goods as they could from the path of the fire. And as we have said in an earlier chapter, this attempt to salvage their possessions ultimately led to organizations such as the “Mutual Assistance Bag Company,” reportedly the nation’s first accredited salvage organization.
Photo courtesy Worcester. Mass., Protective Department
The chief tool of these enterprising, if ill-trained groups, was the canvas bag. “Two stout canvas bags about two by three feet in size” were required by each member of the bag company, who in the vernacular of the day was called “bagman.” His name was inscribed in full on the outside of each of his bags together with the letters “MA,” surrounded by a circle. He was further identified by his round hat with blackbrim and white crown, bearing the initials “BM” in front.
In time of fire the possessor of these bags was required to respond with them to the scene of the blaze (wearing his other insignia, of course) and if a fellow member’s property was in danger, it was his duty to help save all that he could, using the containers.
The bag, therefore, may be said to be the forerunner of the later day salvage cover, just as the bagman or member of the Mutual Assistance Bag Company was the antecedent of today’s salvage corpsman.
Various kinds of sheets and blankets, in fact anything that would repel water, also are said to have been used in this connection. And from these developed the tarpaulin and the salvage blanket, or cover.
As fire service salvage grew and the problem of protecting the nation’s increasing resources from fire (primarily) grew apace, the cover assumed increasing importance. This was reflected in the more exacting specifications for protective covers adopted by salvage corps and patrols, and by the fire service which undertook salvage operations.
It was not merely a question of creating waterproof or water-repellent canvas, rubber or other type of sheet for such covers; it called for a product that had all the virtues of water and weather repellency, but in addition certain other attributes, requisite to efficient covering.
Value of Salvage Covers
Covers represent one of the largest items of expense in the performance of salvage work. There fore, fire insurance salvage patrols and all fire departments which seriously practice salvage, practice all possible economy in the selection, use and maintenance of this salvage facility.
Large users of salvage covers, such as fire patrols and squads, have considerable investment in covers. To them, maintenance of covers is a serious business, just as is the use of covers so as to avoid injury.
Photo courtesy Los Angeles Fire Department
It is hardly possible to measure the actual dollars-and-cents value of a salvage cover in terms of property saved. A salvage cover at one fire may be employed to protect from water damage merchandise and furnishings of small value. Again, the same cover may become the protector of a baby grand piano or an antique worth several thousand dollars. At still another fire, the same cover may be found furnishing security and shelter from water to immeasurably costly machinery or electrical equipment.
Actual monetary worth of a salvage cover may be estimated by its original cost, plus cost of keeping it in good condition (repairs and other maintenance charges) divided by the number of fires in which it is used, and property it has protected from water or other damage. Obviously the longer its operational life, the greater its return on investment. And even after it has served its prime usefulness, it may still contribute further toward preventing damage by the weather, or fire extinguishing operations, as some form of a storage or general utility covering.
Opinions Differ on Covers
There is still some difference of opinion between experts on the subject of covers, blankets or tarpaulins, as they may be called. Although there have been a number of new types of such products made, especially since the introduction of modern plastics, those who practice fire service salvage to any degree have maintained their loyalty to one or another form of cover material which they have used successfully over the years. Many authorities are convinced there will ultimately be still further improved salvage covers, perhaps for the most part made out of new and hitherto unexplored materials, chiefly in the plastic group. This does not necessarily mean that the orthodox and widely accepted treated cotton salvage cover will disappear from the scene.
Although there may be some difference of opinion over the new as against old types of cover material, there is agreement, however, on the principles that a salvage cover should shed water and at the same time hold water under reasonable pressure when “bagged.” There is further agreement that a cover should not get sticky under heat application; that it should be as near chemical proof and as light and easy to handle as possible.
Some rubber covers measure up to some of these requirements, notably their imperviousness to water. But they have other disadvantages, notably cost, which is generally higher than the best treated canvas cover. The rubber products weigh more than other types and have a tendency to slip from high piles of goods and from shelving; and they are not as well adapted to bagging as other kinds because of the difficulty in rolling the edges. Still another difficulty of the rubber type is the tendency to become soft when employed in temperatures not infrequently encountered at fires, and to become brittle, and split or crack when left folded in storage for any appreciable length of time.
The Treated Canvas Cover
The cover in most general use is known as the treated canvas type. The canvas used in this type is treated to make the material waterproof. But it is difficult to waterproof them uniformly, particularly at the seams, and according to the experts they may leak under pressure after they have been used extensively.
Leakage, naturally, is due to the wearing away of the water-proofing solution. Furthermore, there is a tendency for this type of material to mildew when stored for lengthy periods, unless it is chemically treated. But, to quote Chief Frank McAuliffe (Fire Department Salvage Operations, published by the National Board of Fire Underwriters) “these are minor objections compared with their merits which outweigh those of rubber covers.”
Another attribute of the canvas cover is that it is lighter in weight and more resistant to rugged usage encountered at fires. Also, under most operating conditions, the edges of the cover are more easily rolled and they retain their rolled position so highly desirable when arranged to catch water on flat surfaces.
The canvas cover is about the oldest type in use, and through the years the manufacturers of such covers have consistently improved the treating processes (and other characteristics) to make them tougher and more durable, and to give them longer service life.
Size of Covers
Opinions vary among salvage authorities as to the most satisfactory size. One believes the most practical size to be the 12×18 feet. Another claims the most satisfactory all-purpose type to be the 14×18, weighing approximately 32 pounds. The cotton treated 12×18 foot covers weigh 27 pounds.
Photo courtesy Worcester, Mass., Protective Department
Present day cotton treated covers also come in 9×12 foot size.
In addition to regulation fire service salvage covers, mentioned above, there are several other types:
Roof Covers: These are heavy duck covers used in covering roofs after fires, and also for covering oily machinery and broken store windows or doors, to protect them from the weather and trespassers. Usually these covers measure 12×12 feet and 14×14 feet.
Asbestos Covers: Generally used to protect a room or material from damage by heat and/or steam. They are also used to protect fireplaces in controlling chimney fires and for other specific purposes. One application, only recently found practicable, is in controlling truck tire fires.
Motor Covers: Usually made from discarded roof or other covers which have been torn and damaged so that full use of the cover is no longer possible. Small in size but usable for covering motors and small oily items.
Utility Covers: Treated and untreated, used to cover fire apparatus motors or ether objects against weather or dust.
Photo courtesy Underwriters Salvage Corps, Cincinnati
Sometimes used as “carryalls’ or “body bags.
Within the past few years several types of plastic covers have been introduced to the fire service and some salvage companies have experimented with them, with varying degrees of success.
One type is a vinyl plastic coated glass cloth blanket, not presently made in the larger sizes. This product may be thrown over a person or machine enveloped in flames to effectively cut off the oxygen and smother the fire. It can also be used as a first aid fire fighting measure in smothering fires at vents, manholes, in barrels and buckets, or other containers, or used as a welding screen.
This type which evidently finds greater utility in protecting against fire than water used in fire fighting, requires no other covering for the latter purposes; it is coated with a plastic compound made from a vinyl resin, which reportedly provides resistance to acids, alkalies and most solvents and other chemicals. It stays flexible at low temperatures and reportedly will not support combustion. It gives a surface which is easily kept clean by flushing with water.
This, of course, is not strictly a salvage cover, per se. Larger units may later be made of this material. Data on costs as compared with treated canvas have not been received.
Recently engineers at the Du Font Company swung a paper-thin transparent sling under a pleasure car and raised it in the film completely off the ground. The film, called Mylar, is said to be one of several plastics which can do things heretofore accomplished by no other plastics. The film is said to be an excellent insulator, and resists chemicals and solvents. It may conceivably have application in the manufacture of salvage covers. At present, however, tests of specimen covers made by this company have not been completed in representative fire insurance patrols and fire departments.
Still another manufacturer has been producing plastic covers which are finding acceptance both with the fire service and salvage authorities, for special applications and for industrial and mercantile installations. The light weight of this and other plastic covers makes it possible to carry more of them on apparatus, and for users to carry them more easily then the conventional covers. The lighter weight more easily adapts them for inside operations, particularly where there may be perishables, or delicate, breakable products such as found on counters of chinaware and other stores.
Certain objections to these covers have been recorded, notably the subjectability of some to extremes of weather, and a tendency to slip which makes them more difficult to carry and handle under some operating conditions.
In addition to the foregoing, various types of treated paper covers have been introduced. These are for the most part known as building papers and are procurable in small or large rolls. Among them are aluminum foil and reinforced waterproof papers of all types, as well as developments of the old familiar tar paper still carried by most salvage units. Their use, naturally, in fire salvage is limited to specific tasks, such as patching roofs or other openings. Although not essentially of the fire salvage family of facilities, they cannot be ignored.
This leads to a conclusion advanced by several authorities on salvage. It is this: They believe that, as in almost every other field of endeavor, science and American ingenuity and inventiveness will produce new materials for salvage covers of which may be adapted for salvage work and which will have a major bearing on the concept of protecting materials and stocks against injury or destruction bv the elements, including fire itself.
To assist, when calling for bids for the two types of salvage covers now in most general use, the National Board of Fire Underwriters has issued the following specifications:
Size: Either 12×18 or 14×18 ft., tolerance 3 inches plus or 2 inches minus in either width or length, or both. Cloth to be cut 19 ft.
Cotton Fabric: To be of clean cotton, duck, free of knots, dropped threads or other weaving imperfections. The weave of the fabric or count of the warp and filling threads per inch and the strength shall be in accordance with the requirements of Federal Specification No. CCC-D-771.
Treated Cotton Duck Cover: Fabric to weigh not less than 11 ounces per square yard before waterproofing, and not more than 20 ounces per square yard after waterproofing. To be treated with a preparation that will produce a waterproof condition capable of withstanding tests hereinafter specified. The treatment to be such that the covers will not mildew, stiffen in cold weather, nor become tacky in warm weather.
Seams to be not more than two in number, end each seam to be sewed with two lines of stitches on lock-stitch machine with rotproofed and waterproofed thread. All seams to measure from 3/4 to 1-inch between lines of stitches and to be of the “roll” type with edges turned under, and so treated as to prevent leakage at that point, as provided for in tests hereinafter specified.
All edges shall be hemmed by turning under 1 1/2 inches of goods, so as to make three thicknesses of goods all around the edge of the cover.
Rubber Coated Cover: The finished weight of a cover frictioned both sides shall not be less than 24 lbs. nor more than 33 lbs. per cover. Fabric to weigh not less than 7 1/2 ounces per square yard. The strength of the warp or filling shall be not less than 100 lbs. per inch of width in warp and 70 lbs. in the fill.
Covers frictioned both sides shall have a coating weighing not less than 7.5 ounces per square yard and not more than 12 ounces per square yard.
The rubber to be black, bloomed finish, without varnish or other wash. The first application or friction coat shall be calendered and penetrate into the interstices of the weave, showing through on the reverse side. The finished cover shall be free from surface imperfections.
These covers, as stored for use, will be so folded as to create many angles, corners and folds. The rubber coating must not crack, check or peel, due to this folding.
Seams shall not be more than two in number and must not be butted but must be lapped not less than one inch and are tc be in the direction of the greatest length of the cover. All seams are to be cemented.
All edges shall be hemmed by turning back the fabric on itself for a distance of 1 1/4 inches and be cemented in place.
Grommets: The 12×18 ft. cover shall have 24 No. 3 spur brass grommets spaced two at each corner, five at each side and three at each end. The 14×18 ft. size shall have 32 of these grommets, spaced two at each corner, seven at each side and five at each end.
Grommet Reinforcements: All covers to be reinforced on the under side of the cover with a 7 1/2-inch triangular piece of tne same material as that used in body Of cover so as to provide three thicknesses of goods for corner grommets.
Stencil: Covers are to be stenciled with the month, day and year on two opposite corners in 3-inch letters. Eightinch letters designating Fire Department, Fire Patrol, or other organization, at direction of purchaser, to be placed at opposite corners.
Tests: Not less than 20 per cent of all deliveries to be tested as follows:
Covers to be picked at random and placed in a test rack hereinafter described, and there subjected to a depth of 5 inches of water over the seam for a period of four hours. No drop shall appear in the fabric, and leakage inexcess of 1/4-ounce of water at the seam during the test period shall be cause for rejection. If one cover fails, all covers in the assignment shall be tested.
Photo courtesy Underwriters Salvage Corp, Cincinnati
Test Rack: To be made of two pieces of 2×4’s each 16 ft. in length, with two cross pieces of the same material 2 1/2 ft. long. Holds for thumbscrew bolts to be drilled 6 inches from ends of each 16 ft. piece, and 1 1/2 inches in from ends of each 2 1/2-ft. piece. In testing, cover is to be spread out on the floor, treated side up, and each end folded back 2 ft. Each side is then rolled up on one of the 16 ft. 2×4’s to within about 15 inches of one of the seams, so this seam will be in the middle of the rack. The two 2 1/2 ft. 2×4’s are then fastened to the longer pieces by means of the thumb-screws and the rack and cover are raised off the floor high enough to permit observation of the test. Water to a depth of 5 inches is then poured into this trough. The folds at the ends of cover prevent water from spilling while test is in progress.
Lake Test: Using the test rack described above, place rack on top of bricks, or some other object, so as to raise rack to a height of about 8 inches off the floor. Spread cover out flat, treated side up, and press cover down over rack, with seam at middle, until cover is flat on floor, thus forming a rectangular trough, or lake basin, into which water is to be poured to a depth of 5 inches. After 24 hours, with cover resting on floor, there shall be no leakage.
Warranty: The contractor shall warrant all covers furnished under these specifications to be waterproof and to meet the test requirements, and shall agree to replace any cover which, within a period of 13 months after the month and year indicated by the corner stencil, develops defects resulting from imperfections in manufacturing or waterproofing.
Quotations: Quotations shall lie understood as applying to these specifications.
Terms: Terms shall be 2% ten or net thirty days from date of shipment f.o.b. shipping point. Freight paid prices quoted on request.