The purpose of the work . Familiarization with the practical methods of stowage of bulk cargoes (on the example of coal) in the port in compliance with safety regulations and fire prevention measures.
General instructions . When storing coal in the port, the most common are stacks in the form of a wedge and an obelisk . Stacks in the form of a cone, pyramid and prism are much less common and, especially with large cargo flows, are less effective. This is due to the fact that the area allocated for stacks of goods in the form of these figures is much larger (due to passages and driveways) than that of an obelisk or wedge (with the same amount of cargo). The angle of repose a of coal in piles depends on many factors and ranges from 30 to 45°.
When placing coal in warehouses, it is necessary to determine the length L pcs , the width B pcs and the height H pcs of the stack.
The width of the stack is determined by the width of the platform and the size of the passages between the stack and structures (buildings, structures, railway and crane tracks, roads, etc.). The following minimum (more is possible, less is not possible) values are determined when placing bulk cargoes:
distance from the axis of the railway track to the stack – 2.5 m;
distance from the crane runway ( rail head) – 2 m;
passages between stacks – 6 m.
Most of the cranes used in the port have a gantry width (the distance between the rail heads of the crane tracks) of 10.5 m. The railway tracks in the port have the same width as the entire Ukrainian railway network – 1520 mm.
The height of the stack is determined by the restrictions associated with:
using the technical norm of the load on the floor of the warehouse;
transport characteristics of the cargo.
The technical load rate (P t ) on the first site is taken equal to 6 t / m 2 , on the second – 10 t / m 2 . If one platform is given, then the load (P t ) on it corresponds to the value of the first platform. If two sites are given, then it is better to place anthracite on the second one.
For coal, the main height limitation is determined by transport characteristics, namely the tendency to spontaneous combustion . According to the terms of fire safety, depending on the brand of coal and the shelf life, the permissible heights of its stacking are determined (MOPOG Rules).
In this paper , we assume that the height of coal storage according to transport characteristics:
anthracite (grades starting with the letter A) – not limited;
coal grade PZH, PS – 3 m;
coal grades T, G, D – 2 m.
The spatial arrangement of structural elements on the sites is as follows:
if one site is specified, it is located between the railway and crane tracks (Fig. 30);
Rice. 30. Layout of stacks on one site
if two sites are given, they are separated by a crane runway and limited by railway tracks (Fig. 31).
Rice. 31. Layout of stacks on two sites
The length of the stack is determined by the width and height of the stack, its shape and the size of the batch of cargo to be stacked.
Work order . In accordance with the given option , we determine:
brand and quantity (Q pcs ) of each type of coal, t;
number and width (in pl ) of the site (sites), m:
bulk weight of cargo g, t / m 3 .
Since it is necessary to determine the linear dimensions of the stack, then first, by the amount of cargo for each brand of coal, we determine the volume of the corresponding stacks, m 3 :
V pcs = Q pcs / g.
According to the assignment, the width of the two sites is the same (if two are specified), therefore, having calculated the width of the stack on one site, we automatically obtain the width of the stack on the second .
The width of the stack , V pcs, is calculated as the difference between the width of the platform, V pl , and the distances from the railway and crane tracks.
Since the minimum distance from the head of the rail of the crane runway is 2 m, and from the axis of the railway track is 2.5 m, then B pcs is determined from the following expression, m:
In pcs u003d In pl – 2.0 – (2.5 – 1.52 / 2).
For coal grades PZh, PS, T, G, D, the possible height of stacking (H¢) is set , and for anthracites (grade A) it is necessary to determine this height , m:
H¢ = P t / g.
For each brand of coal, we calculate the tangent of the possible angle of dumping of cargo, subject to the required heights of the stacks:
tga = H¢ / (1/2 × H pcs ).
For a stack of each brand of coal, one of three situations is possible:
1. If tga < 0.5774 (a < 30°), then placing the load in a stack in the form of a wedge (Fig. 32, a - line 1) is not possible , since a cannot be less than 30°. This can be only if the stack is specially leveled to reduce the angle, but in practice this is not applied . Then the necessary data for calculating the stack length (L) are as follows:
a u003d 30 ° (we increase to the minimum possible);
stack shape – obelisk (Fig. 3, a – line 2);
H=H¢; V about u003d V pcs ; B = B pcs ;
calculate the side of the base A:
A = 2 × H¢/ tga.
2. If 0.5774 < tga < 1.0 (30° < a < 45°), then the required data for calculating the stack length (L) are as follows:
a – equal to the calculated value;
stack shape – wedge ;
H=H¢; V cl u003d V pcs ; B = In pcs .
Rice. 32. Determining the shape of the stack
3. If tgau003e 1.0 (au003e 45 °), and this is not possible , since a cannot be more than 45 ° (Fig. 32, b – line 1). Theoretically , with the help of various expensive methods, it is possible to increase a, but in practice this is not applied . With the height of the dumping H¢ and the actual value a, the stack width B pcs will be greater than the calculated one. In this case, the necessary distances from the rail heads to the stack will not be observed, and it is generally possible to fill the rails with cargo, which is unacceptable . Then the necessary data for calculating the stack length (L) are as follows:
a u003d 45 ° (we lower it to the maximum possible);
stack shape – wedge (Fig. 32, b – line 2);
V cl u003d V pcs ; B = B pcs ;
recalculate the height H downward:
H = B pcs × tga / 2.
To determine the length of stacks L, the calculation formulas for determining the volumes of stacks in the form of a wedge and an obelisk are used (see lab. work. 5). Having carried out simple transformations of the calculation formulas, we obtain:
for a wedge : L u003d (V cl + 1/3 × H × B 2 ) / (1/2 × B × H);
for an obelisk : L u003d (V about + 1/2 × A × B × H – 1/3 × H × A 2 ) / (B × H – 1/2 × A × H).
At the end of the work, a diagram of the placement of stacks in the warehouse is given, indicating the paths , driveways , aisles and all sizes (Fig. 30 and 31).