Prof. S. V. Lebedev

Spoilage of Sugar During Rail Transportation

Spoilage of sugar during its transportation over long distances is by no means a rare occurrence, and at certain times of the year is quite a frequent phenomenon. It is obvious that spoilage en route of sugar that was perfectly sound before shipment must lie in the conditions of the transportation itself and, to a certain extent, in the methods of its packing.

When sugar is packed in paper, barrels, boxes, and generally in containers that reliably protect it from external influences unfavorable to it, sugar, as is known, withstands even the longest transport quite successfully at any time of year. In connection with this, in examining the phenomenon of sugar spoilage during its rail transportation, this question will hereinafter be considered as applied to the form of packing usual for such shipments—in sacks—and under the conditions of the generally accepted rail transport of sugar in covered, unheated freight cars of the “normal type.” Under such conditions, the body of the indicated type of car is, as it were, a mobile, unheated storehouse for sugar. In this connection, clarification of the special features of such storehouses and of the conditions they create for storing the sugar transported in them should, to a significant degree, illuminate the question of the possibilities of spoilage of the latter during its rail transportation.

The body of a covered freight car of the normal type is characterized, according to the relevant data on railway rolling stock, by the features set forth below.

The base of the body of a covered freight car consists of a row of oak posts, attached below partly to iron brackets riveted to the car’s channels, and partly to the buffer beams. The upper ends of the posts are connected by transverse and longitudinal roof binding beams. Cornices are nailed to the longitudinal roof beams for protection against rain. The roof frames are reinforced with intermediate wooden or iron arches. Over the ceiling arches is laid a ceiling of planks, which are then sheathed on the outside with iron sheets. These sheets bend around, with their ends, a strip made of roofing iron and nailed to the binding frame of the car roof. The iron sheets of the car roof are joined to one another with a lock seam. The car floor is made of two-inch boards laid across the car and joined to one another with a quarter joint. Along the length of the car, at its walls, the boards are fastened to the frame with iron strips. The place where the floor meets the walls of the body is covered with a wooden cornice. The body is sheathed with planks arranged horizontally and joined with tongue and groove. The ends of the planks at the corners are fitted into selected openings in the corner posts and covered with a cornice.

The body of a normal covered car has a length of 21′, a width of 9′, and a height of 7.75 feet.

For lighting the car there are 4 openings under the roof of the car, located in the side walls at their ends. These openings—windows—are closed by iron shields—hatches, secured in iron frames on side hinges and locked from inside the car with the corresponding latches.

In each longitudinal wall of the car there is, for entry and loading, a doorway measuring 1830 mm, closed by a sliding door, which below is supported by two rollers resting on the door rail, and above—by iron-

... strip, which at the same time serves as an umbrella protecting the upper closure of the door from rain. When the car is closed, the door fits closely up to the iron jamb angle, fastened to the door post by bolts. The gap formed between the second door post and the door is closed by an iron strip fastened to the door.

The brief description given above of the construction of the body of a standard covered freight car is determined by its purpose: to protect the transported cargo from wetting, leakage, spillage, and so forth¹.

While fully satisfying these modest requirements, the body of a freight car of the type under consideration obviously does not at all ensure constancy, stability, and independence of the temperature and humidity of its internal space from the corresponding conditions and their changes in the outside atmospheric air. This is indicated quite definitely by the lightness of the wooden sheathing of the car body, as well as by the lack of airtightness in the arrangement of the window hatches and doors of such cars and, finally, by the inevitable appearance over time of cracks and fissures in the thin wooden sheathing, roof, and floors of the car.

The usual character of such kinds of leaks is confirmed by practice and sanctioned by the official rules regulating the exchange of freight cars between the individual railways. The latter is evident from what is cited below. Among the defects of the bodies of covered freight cars that preclude the transfer of a car, according to the “General Agreement between the Railways”², § 119, are “joints of the main wooden parts of the body that have separated by more than 12.5 mm”; according to § 120³ of the same “Agreement,” “natural cracks running ray-like from knots are not taken into account.”

Thus, in the body of a freight car, gaps of a definite character and openings not exceeding a known magnitude appear to be an ordinary and, to a certain extent, legalized phenomenon.

The leaks in door and window closures, together with the gaps in the body of freight cars, make possible a certain exchange between the outside air and the air of the car’s internal space.

What has been set forth above indicates that the covered freight car commonly used for transporting sugar may be regarded as an unheated summer mobile warehouse with very thin wooden walls and floor, raised above the ground. Moreover, this thin floor of the car, just like its roof and walls, is freely and vigorously washed, during the movement of the train, by the outside atmospheric air.

The latter circumstance is of substantial importance with respect to the temperature regime of the warehouse-car. In this respect it places this mobile warehouse in an entirely peculiar position in comparison with ordinary unheated warehouses located on the ground, whose thermal inertia leaves its sharp and characteristic imprint on the temperature regime⁴ and its changes in unheated warehouses. In a covered freight car the floor is no longer in contact with the ground but, like the roof of the car, with atmospheric air, freely and continuously flowing around the floor of the car while the latter is in motion.

In connection with this, the ordinary covered freight car may be regarded as a warehouse, as it were, with two roofs: with the usual upper roof and with a lower

by the roof, in the form of the thin wooden floor of the car. Both of these covers equally receive the thermal radiation of the atmosphere, both at night and in the daytime.

However, despite this, the heating of the upper roof of the car in the daytime period must be different, and moreover stronger, in comparison with the heating of the car floor. This occurs thanks to solar radiation, which brings into the car through its roof additional heat, quantitatively unequal at different times of day and year, depending on the intensity of the solar radiation. The numerical value of solar radiation, denoted by \(J\), is expressed in small calories and is equal to the amount of heat which a blackened surface of 1 sq. cm, placed perpendicular to the sun’s rays, receives in one minute. In the more general case, when the rays of the sun fall on the surface illuminated by them at an angle \(\alpha\), the amount of heat received by one sq. centimeter of this surface is expressed by the following formula:

\[ J_{\alpha} = J \cdot \operatorname{Sin}\alpha . \]

With an increase in the quantity of water vapor in the atmosphere, the intensity of direct sunlight decreases. The higher the sun, the more significant the intensity of solar radiation on the earth’s surface and the greater the heating of the roof of the warehouse car; consequently, the greater the difference in the degree of heating inside the car under the roof and near the floor.

To characterize the daily course of solar radiation, table I, compiled by N. N. Kalitin, is given below. This table gives, for Slutsk, the value for each hour of the first day of each month of the year (the average for the period 1913–1919). The numerical value is given in small calories per one sq. cm.

The given table I clearly shows that by day, especially at noon and around it, the roof of the car, and consequently also the inner air space in its upper part, receives a noticeable, sometimes very great, additional heating in comparison with the floor and the lower layers of the air space of the car.

At night, however, the floor and roof of the car are cooled equally, being under the same influence of the thermal action of the cold night air.

This cooling is transmitted equally into the car from above as well as from below. But since the air at the top of the car was warmer during the day than below, therefore at night too, with equal cooling through the roof and the floor, the lower layer of air in the car proves to be less heated than the upper.

As for the amplitude of daily temperature fluctuations, it, as is known, depends on many causes, namely: on the properties of the earth’s surface in the given place, the time of year, geographical latitude, cloudiness, hour of the day, etc. For the climate of geographical latitudes and, in general, for conditions possible on the territory of the USSR, the amplitude of daily temperature fluctuations varies from \(1^\circ\) to \(12^\circ\) C and higher, as shown by the data of G. Wild¹, presented in table II, which gives the mean monthly amplitudes.

If one takes not the mean monthly amplitudes, but individual maximum temperature fluctuations during a day, then the amplitude of such fluctuations in individual cases can attain very large values.

For example, for the city of Tomsk, during a day the temperature rose:

Table I.

Under the same conditions, the temperature there also fell.

At 33.4° C during the transition from 13 to 14 February 1879.
» 21.1 » » » » 19 » 20 » 1895.
» 27.6 » » » » 2 » 3 March 1876.
» 27.2 » » » » 23 » 24 » 1910.
» 30.6 » » » » 13 » 14 December 1879.
» 20.1 » » » » 1 » 2 April 1879.

Table II.

It is obvious that daily fluctuations of 5–6° and more already lead to the appearance of quite perceptible dew. If a storehouse in general and, in particular, a railcar in which sugar is transported does little to protect its cargo from temperature fluctuations of the surrounding air, then in such cases, when sugar is packed in sacks, a certain sweating of it inevitably occurs, and consequently the sugar also becomes damp. The latter, depending on the conditions, may be a temporary, passing phenomenon, or one that subsequently cannot be eliminated in its consequences.

In connection with the previously established difference in temperature conditions at the lower and upper levels inside the railcar, the possibility of dew formation, and consequently the danger of the sugar becoming damp at the bottom of the railcar, must be greater than at the top.

With regard to the possibility of the sugar becoming damp at the top and bottom of the railcar, what matters is not only the temperature fluctuation of the outside air, but also the conditions of heat transfer between it and the sugar located in the railcar.

Depending on this, the temperature fluctuations of the outside air may be perceived to a greater or lesser extent by the sugar located insi-

three cars. In this respect, the conditions under which temperature fluctuations of the outside air are transmitted to sugar located at the top, in the middle of the car, and to sugar lying directly on the floor differ sharply.

Below, the heat from the floor walls is directly taken up by the sugar lying on it, whereas at the top of the car heat transfer from the roof of the car takes place through a thick layer of air separating the ceiling of the car from the mass of sugar. Thus, sharp fluctuations in the temperature of the outside air are moderated by this intervening layer of air, which is at the same time a poor conductor of heat. Consequently, the possibility of the sugar located directly on the floor of the car becoming damp is considerably greater than for sugar lying higher up.

The thin layer of straw usually spread on the floor of the car, because this layer is insignificant and because of the great pressure exerted on it by the sugar lying above it in sacks, does, as practice shows, very little toward preventing the lower row of sacks of sugar from becoming damp.

The interlayers of air present in the car above the sugar and around it, in addition to what has been indicated, have another significance in connection with leaks in the body of the car. These leaks are concentrated mainly in the upper part of the car body, owing to the window openings located there. In addition, the door closures create leaks in the middle of the side walls of the car, over their entire height.

All these leaks in the car body, both structural and accidental, promote, especially when the train is in motion, a certain circulation and exchange between the outside air and the air of the interior space of the car. This phenomenon must be inevitable, since when the train moves, complex dynamic phenomena are set up in the air surrounding it. In this case the following occurs:

a) the front and rear surfaces of the cars composing the train are subjected in places to positive and in places to negative pressure, and the streams of air, flowing around the cars, break through the leaks in their bodies into their interior space; b) with a certain arrangement of the leaks of the car body relative to the motion of the air streams flowing around the train, air is to some extent injected out of the interior space of the closed car.

The indicated circumstances cause a constant circulation of air in the upper and middle space of the car. The presence of this circulation, during temperature fluctuations of the outside air, largely eliminates the danger of dampening of sugar located at the upper levels and in the middle of the car.

The reason for this is that warm air, comparatively more humid than cold air, which appears at times in the car and, at each sharp lowering of the temperature of the outside air, threatens to release its excess moisture onto the sugar, under the condition of the circulation noted above, is continuously replaced at the top and in the middle of the car by outside air of correspondingly already comparatively lowered temperature and lower humidity. This largely eliminates the possibility of dew appearing on the transported sugar lying in the indicated spaces of a covered freight car of normal type.

The sugar stacked in the front and rear parts of the lower half of the car is in a different position; here, the sugar in the lower row of sacks, lying directly in contact with the floor, is in the worst conditions.

The indicated spaces of the car, bounded by solid walls and the floor without any structural leaks there, exclude the possibility of direct communication of the car’s internal air with the outside

atmospheric. Owing to this, in cases of a rapid fall in the outside temperature, the air inside the car that is cooled in connection with this, in the indicated spaces of the car, having no possibility of escaping from there beyond the limits of the car, remains entirely within it and is cooled there as well. In connection with this, naturally, there arises the danger of dampening of the sugar stored here. With a certain lowering of the outside temperature and with a known relation between the humidity of the air inside and outside the car, dampening of the sugar lying here becomes inevitable, manifesting itself for the reasons already clarified earlier, first and foremost, and most of all, in the lower row of sacks on the sides where they are in direct contact with the floor. The upper rows of sugar sacks, protected by the air layer present here from direct cooling through the ceiling and walls of the car, are in better conditions with respect to the possibility of dampening.

Because of the relatively rapid warming of the upper and middle space of the car, with a subsequent rise in the temperature of the outside air, the sugar stored in these spaces of the car rather easily reaches the corresponding temperature, as is determined by what was analyzed earlier. As for the sugar located in the front and rear spaces of the lower half of the car, both these regions, owing to their noted isolation, warm up considerably more slowly. In connection with this, there are formed here, as it were, pockets of cold and damp air, having no outlet from there. By its presence this air prevents the sugar lying here from warming up, at the same time promoting the development in it of various commonly known processes connected with excessive moisture.

Thus, under conditions of long transports, associated with repeated, at times sharp, fluctuations in the temperature and humidity of the outside air, sugar packed in sacks and transported in covered freight cars of the normal type is inevitably subjected, to a greater or lesser degree, to the danger of dampening, depending on the duration of the transport, the season of the year, the geographical position of the route, etc.

This dampening has its strongest effect, as is usually observed, in the lower row of sacks on the side facing the floor, and manifests itself most sharply in the front and rear parts of the car.

The creation of an air layer separating the car floor from the sacks of the lower row must be recognized as one of the means capable of helping to reduce the danger of dampening of the sugar being transported.

For the arrangement of the indicated air layer, it is necessary to stow the sugar in the car not directly on the floor, but on a wooden, sparse flooring made of boards, placed either on sufficiently thick sleepers set on the car floor, or on iron supports that remove the flooring from the car floor.

All that has been set forth above concerning the possibility of sugar dampening, i.e., the possibility that, in the overwhelming majority of cases, constitutes the primary cause of spoilage of entirely good-quality sugar transported in covered freight cars, leads to the following conclusion:

A normal covered freight car, under all conditions, always leaves the possibility of dampening of the sacked sugar transported in it. Protecting the latter only from mechanical wetting by rain or snow, this type of car does not at all protect the transported cargo from temperature fluctuations and the consequences of changes in air humidity in its internal space. The inevitable consequence of this is repeated sweating, leading to dampening and subsequent spoilage of the sugar.

The temperature dependence of a normal-type covered freight car on the temperature of the outside air constitutes one of its most essential characteristic features, determining the possibility of transporting in it various kinds of cargo.

If fruits, eggs, vegetables, meat, game, fish, and other similar products require quite definite, though different, temperatures, allowing without danger to the goods being transported only the very slightest deviations from temperature norms, then sugar, with respect to temperature as such, permits exceedingly broad limits of fluctuation. It can be preserved without any harm to itself both at \(-40^\circ\) and at \(+30^\circ\), undergoing no change for the worse in quality even during prolonged storage.

But this is possible only under the indispensable condition that the sugar itself be of perfectly good quality and dry, and that the air space in which the stored sugar is located also be dry. One need only allow, under the preceding conditions, some excess humidity in the air surrounding the sugar, and the situation with respect to the possibility of preserving the sugar unharmed changes sharply.

This excess moisture in the sugar or in the air surrounding it, even if it appears only temporarily in the latter, inevitably, sooner or later, leads to spoilage of the sugar for chemical, physico-chemical, and microbiological reasons, which have been repeatedly examined by a whole series of investigators. Since this question in the indicated direction has already more than once been noted in the literature by review articles, it is therefore superfluous to dwell here on consideration of the question of sugar spoilage in this plane.

In the present case, the principal interest is concentrated on the conditions of sweating of the transported sugar, as the primary cause of its subsequent harmful complications.

With the natural course of temperature changes and fluctuations of atmospheric air in humidity during the period of the year when the outside temperature is above \(0^\circ\), the periodic appearance of the dew point is a normal phenomenon. In connection with this, despite the complete indifference of sugar to temperature changes within the limits of possible daily fluctuations in atmospheric air, it nevertheless turns out that for sugar they cannot be allowed without fear for its integrity, owing to the changes in air humidity associated with natural temperature fluctuations that lead to the appearance of dew.

Under such conditions, the use of ordinary covered freight cars of the normal type for transporting sugar proves definitely to threaten sweating and subsequent spoilage of the sugar being transported.

Cars of special designs, for example isothermal ones, are too expensive and, requiring special costly care, prove inaccessible for sugar transport.

Among the cheaper cars of special construction, the applicability of which in the present case might be considered, there can be only ventilated freight cars, which, by the arrangement of their walls, roofs, and floors, ensure a certain stability of the temperature of the car’s interior space independently of the temperature fluctuations of the atmospheric space.

The diagrams of successive temperature changes inside the car, given in drawing No. 1, approximately at \(1/4\) of the height from the roof and at the same distance from its floor, show to what extent a ventilated car, in temperature terms, depends on the fluctuation of the temperature of the surrounding air. The same drawing gives the course of temperature fluctuations of the outside air.

In order to assess the significance of the temperature diagram in drawing No. 1, it is necessary to establish what the ventilated car under consideration represents. This car belongs to the type of fruit cars built by the Vladikavkaz Railway, in the design of which it was intended to satisfy the following requirements:

a) to increase loading capacity,

b) to arrange a through longitudinal passage by means of doors in its end walls,

c) to have cars convenient for transporting fruit, hay, narzan, beer in one direction and other freight in the other.

Internal dimensions: 9.26 × 2.94 × 2.48 meters.

Inside the car there are longitudinal folding shelves.

In the middle there is a longitudinal passage to the car doors.

The insulated car is provided with double sheathing of the walls, ceiling, and floor. The insulation consists of a layer of cork and cardboard, after the type of the sheathing of the Moscow–Kazan Railway. Ventilation of the car is achieved by installing louvered hatches in the side walls, closed by removable shutters. These hatches are opened as needed. In addition, two more ventilators are installed in the ceiling. There are no devices for cooling in the car. The cost of the car at prewar prices was 3,400 rubles.

Such a ventilated car, in the case under consideration, was loaded in Turkestan with fruit sent in the second half of July 1913 to Moscow in a train organized by the “Moscow Committee for Refrigeration.” The train was made up of special cars of various designs for perishable products. The purpose of dispatching this train was to ascertain, by means of an experimental shipment¹ from Turkestan to Moscow, the conditions of packing, storage, and transportation of perishable products, and also to reveal the merits and shortcomings of special cars of various systems.

The cars were equipped inside with thermometers at various places and heights. Thermometers were also placed on platforms under the roof of the car in order to characterize the temperature of the outside air in the shade.

The general character of the temperature curves inside the car at its ceiling and at the floor, when compared, judging by Drawing No. 1, with the temperature curve of the outside air, indicates their almost complete correspondence, with some delay in following changes in the outside temperature and with a slight decrease in the amplitude of the temperature fluctuations. Between the temperature curves at the top and bottom of the car, approximately 1½ arshins from its roof and floor, there is almost no difference in the temperature readings; there are only some divergences in time in the indication of one and the same temperature.

The similarity of the temperature curves at the top and bottom of the car and their relation to the temperature course of the outside air indicates that the effect of heat transmission by the floor and roof in a ventilated car, at a somewhat equal distance from them, proves to be the same.

Thus, in this respect there is no difference between the floor and the roof of the ventilated car. But it is obvious that the temperatures and their fluctuations directly under the roof and directly at the inner surface of the floor will not be the same in the daytime, owing to the effect on the roof in the daytime of direct solar illumination, which the floor does not experience. Unfortunately, in the case considered, no corresponding experimental observations were made in the ventilated car.

From the data presented it is clearly seen that such a car, even of a reinforced type, with respect to insulation, just like an ordinary covered freight car, cannot protect the temperature condition of its interior space to such an extent as to eliminate here the possibility of such temperature fluctuations as would not threaten the appearance of sweating in connection with changes in temperature outside the car.

In view of this, the tendency toward the principle of isothermal wagons transporting sugar should be recognized as inexpedient. It is therefore necessary to seek other premises on the basis of which freight cars for sugar should be constructed.

Seeking these premises, it is necessary to take into account that sugar transported in ordinary covered freight cars of the normal type suffers essentially not from temperature fluctuations as such, but from the repeated appearance of dew inside the car, which is caused, on the one hand, by repeated cooling and, on the other, by the continuous change of air in the car. As a result, the air of the interior space, just dried by cooling and thereby already deprived of the possibility of depositing dew during repeated cooling, is, with the ordinary leaks of the accepted type of freight cars for sugar, over time replaced by moist outside air entering from without. The latter, upon the subsequent cooling of the car, again deposits dew, which is absorbed by the sugar being transported, and so on.

Under such conditions, sugar becomes an accumulator of moisture from an unlimited quantity of external air, freely and continuously penetrating into the car. Under similar conditions, during a long journey at a certain season of the year, the sugar inevitably becomes damp and then inevitably spoils.

Consequently, the main cause of such a situation lies in the leaks of the car and in the possibility of outside air freely penetrating into it.

And therefore, naturally, the means that eliminates such a phenomenon must be the airtightness of the body of a freight car intended for long-distance transportation of sugar packed in sacks.

Apart from eliminating the danger of sugar becoming damp, the convenience of this principle also consists in the fact that its practical implementation should not noticeably increase the cost of the cars ordinarily used. The construction of airtight closures for doors and window hatches presents no economic or technical difficulties.

The air-impermeability of the body of freight cars is a completely simple problem in comparison with achieving isothermality of the car.

When dry, good-quality sugar is placed in airtight cars, this sugar, even on the longest shipments, will invariably remain outside any danger of becoming damp and spoiled, regardless of any practically possible fluctuations in the temperature and humidity of the outside air.

Such hermetically constructed cars can be widely used for a very large assortment of goods that do not require access of air and do not suffer from temperature fluctuations within the limits of the latter’s annual amplitude.

Such cars, with a known design, will make it possible to pump air out of them before shipping sugar. It is also possible to replace the moist air present in the car with dry air, specially prepared and introduced into the loaded car.

General conclusions.

1. The covered cars of the normal type currently used for transporting sugar, over long distances during the season of the year with temperatures above \(0^\circ\), inevitably lead to dampening and subsequent spoilage of the sugar, if it is transported in sacks.

2. The use of isothermal cars of a cheap, simplified type for transporting sugar packed in sacks does not eliminate the possibility of its becoming damp.

The use of improved isothermal cars with artificial cooling is inaccessible for shipments of sugar because of the high cost of such cars and the large amount of freight in them.

1. The airtightness of freight cars for sugar appears to be the basic principle that promises the unconditional elimination of the possibility of sugar becoming damp en route; at the same time, the principle of airtightness provides grounds for the assumption of its practical, technical, and economic expediency when applied to the problems of car building from the standpoint of the requirements imposed by the sugar industry.

Conclusion.

The development of the design, types, and, in general, questions of the construction and possibilities of operation of airtight cars for the transportation of sugar under the conditions of the USSR must become one of the immediate tasks of our sugar industry, as one serving a colossal territory extending for thousands of versts, situated, moreover, in the most diverse geographical latitudes, with sharply differing climates in its separate regions, beginning with almost subtropical and ending with polar countries.

To the article by Prof. S. A. Lebedev

Temperature Fluctuations Inside Ventilated Car No. 253429

Transcaucasian Railway

15 July — 21 July

Hours: 2, 4, 6, 8, 10, 12

Temperature scale: −10 to 60

After loading the goods

After loading the goods

— Temperature between the side wall and the ceiling
- - - Temperature [[unclear: in the middle and lower shelf]]
···· Temperature of the outside air

1. “Report on the organization of experiments on the packing, storage, and transportation of perishable products from Turkestan to Moscow in 1913.” D. N. Golovin. 1913. ↩↩↩

2. “General Agreement between Russian Railways on the Mutual Use of Freight Cars,” 1906, p. 97. ↩

3. Ibid., p. 90. ↩

4. S. V. Lebedev, “Analysis of the Phenomenon of Sugar Becoming Damp,” 1927, pp. 55–69. ↩