HEATER PADS FOR CONTAINERISED BULK LIQUID TRANSPORT

This invention relates to heater pads for containerised bulk liquid transport.

It is known to transport liquids in flexible bags or tanks contained within a transport or shipping container. The bag or tank is first placed in the container and then filled with liquid through a pipe or hose which feeds the liquid into the flexible bag or tank through a small inlet hole. The hole is shut during transport. The container walls help support and constrain the filled flexible bag or tank although further structural supports are sometimes provided, particularly adjacent the container doors, so that, during filling, the bag or tank does not expand to such an extent as to render closing the doors difficult. After the closed container has been transported to its destination, the flexible bag or tank is emptied through a suitable outlet hole. Pumps can be used to force liquid into or out of the flexible bags or tanks. Once emptied, the flexible bags or tanks may be rolled up or folded for disposal.

A known problem occurs when transporting liquids from a warm climate to destinations in colder climates: the contents tend to thicken or congeal into a paste-like consistency, or even change phase either partially or fully into a waxy or more solid form. If this occurs, the flexible bags or tanks cannot be

emptied easily in the usual manner. It has become customary, in such circumstances, to provide some form of heating to reduce the viscosity of the contents of the flexible bags or tanks and so facilitate the outflow of the liquid therefrom.

In a known system, a heater pad is inserted into the container before the empty flexible bag or tank is placed there. Typically, it is placed on the inside floor of the empty container. Upon arrival at the destination, steam or hot water is passed through the heater pad to warm up the contents of the flexible bag or tank for discharge. When the emptied flexible bag or tank has been removed from the container, the heater pad is also removed, rolled up into a much smaller volume and returned for possible re-use. Known heater pads consist of inlet and outlet headers, typically rigid pipes connected to several long pieces of flexible tubing which form the heating elements. The inlet and outlet headers are placed at the container door for easy access and the flexible tubing is arranged across the floor of the container typically in either a staircase (ladder) or a spiral (coil) or a zig-zag pattern. Sometimes an additional distal intermediate header, typically a rigid pipe, is used as well. The flexible tubing is usually made of suitable steam tube. When warming of the contents of the flexible bag or tank by feeding steam into the inlet header of the heater pad through the pieces of flexible tubing and out of the outlet header, heat is conducted from the steam passes through the walls of the flexible tubing, through the wall of the flexible bag or tank and into the contents thereof. It can take two or three days sufficiently to warm the contents in a typical shipping container from the low twenties (degrees Celsius) to the high forties (degrees Celsius) or even more, the actual time depending upon the nature of the contents and the ambient temperature and winds at the discharge point. This is undesirable. Additionally, in use, there is a tendency for the flexible tubes to be crushed flat at weaker spots by the weight of the contents of the flexible bag or tank which reduces the steam flow through them, so reducing the warming efficacy in the vicinity. Making flexible tubes more rigid tends to reduce their efficiency as the heat cannot

escape. A further problem with the known heater pads is that the flexible tubes are often physically damaged in transit, so the heater pad has to be discarded.

The problem underlying the invention is to provide a robust and effective heater pad which works efficiently to raise the temperature of liquid stored in a tank or bag located within a shipping container.

These problems are solved by a heater pad for containerised transport with the features of the main claim.

By making the heater pad of a number of individual arrays of non-flexible tubes, stronger heating elements are produced with tubes that are less likely to be flattened. They are preferably made of metal which has good heat conductivity, so reducing the time taken to warm up the contents of the flexible bags or tanks.

The heater pad may be thought of as being made up of an assembly of flat arrays of tubes, for example three to six such arrays, which arrays are joined by short flexible tubes so that the heater pad can be folded up by bending the flexible tubes to convert the pad from an extended flat sheet form to a compact form, essentially a stack of arrays, which is easy to transport. When the pad is unfolded, those same flexible tubes enable all the arrays to be laid flat and coplanar upon the floor of the shipping container to form the heater underneath the bag or tank.

The arrays of the heater pad can provide improved heat transfer because of the higher heat conductivity of the rigid tube arrays when, these are made of metal pipes, as well as being strong and resistant to damage during handling and transport, thereby reducing the wastage of heater pads. Also, since the pad is modular, i.e. the heating elements are in several separate arrays, should damage occur to one of them, only that array needs to be replaced to

reinstate a complete and functional heater pad.

The invention is illustrated by way of example with reference to a specific embodiment which is shown in the accompanying drawings. In these drawings:

Figure 1 is a diagram of the array of pipes in a flexible heater pad according to the invention.

Figure 2 is a perspective diagrammatic view showing a heater pad in half- folded condition.

Referring to the drawings, the heater pad consists of five flat arrays (denoted 1 to 5) of rigid metal pipes. The length of each array is just less than the width of the shipping container into which the pad is to be placed, and the combined widths of the arrays just less than the length of that container. The pipes may be steel pipes of e.g. 25 mm diameter. The outline of the container floor is denoted by dashed line 10.

The arrays are connected via short lengths of flexible hose 8, for example 15 mm steam hose coupled to the pipes by hose connector clamps, to a set of inlet and outlet pipes shown at the top of Figure 1 , and which at their right hand ends as shown in the drawing are formed into a header array 6 which is located by the container door when the heater pad is installed. The arrays are overwrapped by a metallised sheet 11.

When the pad is to be placed on a container floor, it is preferable that first a thin heat insulating layer is placed on to the floor. This is to reduce the heat loss through the floor of the shipping container while the contents of the flexible bag or tank is being heated. The bag or tank may then be placed either directly upon the heater pad or on a thin conductive layer placed between it and the heater pad to spread the heat more evenly.

The bag or tank may then be filled and the container transported. If, at the destination, the contents need heating, steam or hot water is fed through the arrays from a suitable source until the liquid can be pumped or drained from the bag or tank.