According to the prior art, the thermal barrier function and the function of cooling the friction elements of the mechanical packing are carried out by tappings (ducts that supply certain zones and have inlet(s) and outlet(s) are defined as tappings) arranged in the pump housing, the mechanical packing and in the fluid header, if there is one. Existing techniques make maintenance difficult, since piping has to be removed beforehand. Moreover, the arrangement of numerous tappings in standard components increases costs, in particular because of the holes and the welding of the supply piping. Such devices make it more difficult to carry out maintenance on the sealing device inasmuch as the tappings are made in the mechanical packing and the pump housing.
In this context, the problem set here is to produce a pump sealing device of the abovementioned type, which has a simple structure and facilitates maintenance of said device and improves the service life of the device.
The mechanical packing provides sealing at the end of the shaft and on the outside of the pump housing. The temperature of the mechanical packing and of the water flowing near the mechanical packing must not exceed a threshold temperature, conventionally 100° C. However, typically, the water which flows through the pump is at a temperature of around 200° C. Given the mechanical properties of the packing and in particular of the stationary face ring and the rotating face ring and the arrangement thereof in the sealing device, it is important to protect them from excessive heat in order to protect them from deterioration in their operating state. Specifically, an exchange of heat by conduction between the pump housing and the mechanical packing can impair correct operation of the seal and in particular the seal at the point between the stationary face ring and the rotating face ring. Moreover, friction between the rotating part of the mechanical packing defined by the rotating face ring of the packing, on the one hand, and the stationary part defined by the stationary face ring of the packing, on the other hand, dissipates energy in the form of heat, leading to an increase in the temperature and premature wear of the stationary face ring and rotating face ring. Thus, in order to increase the service life of the mechanical packing, provision is made for the mechanical packing to be cooled at the points where friction takes place, i.e. at that point in the mechanical packing and, more precisely, at the point where there is a relative movement between the stationary face ring and the rotating face ring.
Furthermore, the present invention aims in particular to optimize the maintenance of the sealing device and to increase the service life of the sealing device.
The solution proposed by the present invention is that the pump sealing device comprises:                a mechanical packing,        a fluid header comprising:                    a first plurality of surfaces that cooperate with said mechanical packing;            a second plurality of surfaces that are designed to cooperate with a pump housing;            a plurality of ducts that form, in an operating state, a first fluid circuit that constitutes a thermal barrier between the first plurality of surfaces and the second plurality of surfaces, and a second fluid circuit that supplies fluid to said mechanical packing in order to cool it.                        
Such an arrangement advantageously facilitates maintenance and increases the service life of the sealing device by proposing a sealing device in which a fluid header is incorporated. The fluid header, which is included between the mechanical packing which is to be protected and the pump housing that defines a hot zone, incorporates first and second circuits. The function of the first circuit, which circulates in the fluid header between the pump housing and the packing, is to form a thermal barrier in order to protect the packing from the heat dissipated by the pump housing and caused by the hot water flowing through said pump. The function of the second fluid circuit, which supplies fluid to the packing, is to cool the packing in order to lower the temperature so as to allow the sealing device to be used with no risk of leakage—this then preventing pump water from coming into contact with the external surroundings.
Furthermore, maintenance is facilitated on account of the fact that the header tank mechanically welded between the pump housing and the packing makes it possible to combine the two functions in a simple manner. Thus, it is not necessary for there to be tapping on the pump housing and on the packing. Furthermore, the device does not include a seal at the point of the thermal barrier and no hole in the pump housing in order to supply the thermal barrier.
In another embodiment of the invention, the thermal barrier might be formed by a recess that separates the first portion and the second portion of said fluid header, said first portion being intended to be oriented alongside a hot zone and said second portion being intended to be oriented alongside said packing, said recess containing a fluid.
In another embodiment of the invention, a space defining an exchange zone, between the mechanical packing and the fluid header, which is adjacent to friction elements of said mechanical packing, might contain a fluid for cooling said elements.
In one embodiment, the fluid header comprises a first duct and a second duct for respectively supplying and evacuating the second fluid circuit, said first duct and second duct each extending from a radially outer surface of the fluid header to said space that communicates with the packing.
In one embodiment, the fluid header comprises:                a third duct for supplying said recess, said third duct extending from a radially outer surface of the header to a first internal duct arranged inside said fluid header;        a fourth duct for evacuating said recess, said fourth duct extending from said radially outer surface of the header to a second internal duct arranged inside said fluid header.        
In one embodiment, the recess extends radially inside the header, defining an annular shape.
In another embodiment of the invention, the first fluid circuit and the second fluid circuit are connected to a fluid-cooling device.