TECHNICAL FIELD

[0001] The present subject matter relates, in general, to stuffing box, and in particular to a stuffing box with ports for cooling.

BACKGROUND

[0002] In most centrifugal pumps, the rotating shaft that drives the impeller penetrates the pressure boundary of the pump casing. Hence, it is important that the pump is designed such that leakage of liquid along the shaft at the point that the shaft penetrates the pump casing is prevented. There are many different methods of sealing the shaft penetration of the pump casing. Factors considered when choosing a method include the pressure and temperature of the fluid being pumped, the size of the pump, and the chemical and physical characteristics of the fluid being pumped. Typically, a stuffing box is used to prevent the leakage of pressurized fluid, such as water or steam, from a pump casing. A stuffing box is an assembly which is used to house a gland seal, in which material is compressed around a shaft or axle, for example, in centrifugal pumps or turbines, to prevent the leakage of pressurized fluid.

BRIEF DESCRIPTION OF DRAWINGS

[0003] The detailed description is given with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components.

[0004] Fig. 1A shows an outer sectional view of a stuffing box coupled to a pump casing, in accordance with an embodiment of the present subject matter.

[0005] Fig. 1B shows an inner sectional view of a stuffing box coupled to a centrifugal pump, in accordance with an embodiment of the present subject matter. [0006] Fig. 2 shows a detailed view of part of a stuffing box with ports for cooling, in accordance with an embodiment of the present subject matter.

[0007] Fig. 3 shows detailed view of cooling ports in a stuffing box, in accordance with an embodiment of the present subject matter.

DETAILED DESCRIPTION

[0008] The present subject matter relates to a stuffing box with ports for cooling to be used in, for example, centrifugal pumps and turbines. The ports of the present subject matter help in delivery of pumping fluid to the stuffing box for reducing the heat generation caused due to friction between packing of the stuffing box and the shaft sleeve on which the stuffing box is disposed, which would otherwise lead to early wear of the shaft sleeve.

[0009] A conventional stuffing box comprises a housing, a packing, a gland for compressing the packing, a lantern ring, and a cooling port. The lantern ring may be a metallic or non-metallic ring and is generally placed about midway between two sets of packing. Sealing water or lubricant is admitted from the cooling port into the traveling area of the lantern ring for reduction of friction between the packing and the shaft sleeve. However, when the packing wears, the lantern ring moves beyond the traveling area for which it is designed and sealing water or lubricant can no longer enter the stuffing box. Thus, the unit needs to be taken out of service and re-packed with new packing.

[0010] In some conventional systems, an external liquid or grease is used to lubricate and cool the packing and to seal the stuffing box from air entering (if operating on a vacuum or a suction lift) into the pump or turbine. The cooling liquid is either delivered from the casing or from an external source to the cooling port. In case of cooling liquid being delivered through the casing, as there is high pressure from the discharge side of the pump, the pumping fluid also leaks into the seal cavity along with the cooling liquid. Generally, there is an excess of leakage of the pumping fluid into the seal cavity, which happens in both shut off and normal working condition, due to the pressure difference between the discharge side and the seal cavity. In the case of cooling liquid being delivered from the external source, there is high pressure from the external source, which is controlled by using valves, thereby making the process complex and costly.

[0011] The present subject matter provides an improved stuffing box with cooling ports. The stuffing box of the present subject matter comprises a plurality of cooling ports placed in the wear ring seating portion of the stuffing box. As is understood, the wear ring portion of the stuffing box is the portion of the stuffing box that is towards the impeller of the pump, where a wear ring is disposed to reduce friction between the stuffing box and the pump casing surrounding the impeller.

[0012] The stuffing box further comprises a fluid seal chamber, a packing to be disposed on a shaft sleeve in the fluid seal chamber, a lantern ring to be positioned radially between the shaft sleeve and inner wall of the stuffing box, and a gland engaged with the outer end of the stuffing box. The lantern ring is disposed about midway in the packing and holds the packing under compression with the gland.

[0013] In one example, the cooling liquid for the packing is supplied from the rear side of the impeller wear ring area. The rear side of the impeller wear ring area faces towards the stuffing box. As the gap between the wear ring and the impeller is small, the pressure developed is low. This facilitates in a small amount of the pumping fluid being delivered to the lantern ring for efficient cooling and lubrication of the packing and shaft sleeve, and thus reduces heat and wear, while also substantially reducing leakage of the pump fluid.

[0014] Fig.lA shows an outer sectional view of a stuffing box coupled to a pump casing, and Fig. IB shows an inner sectional view of a stuffing box coupled to a centrifugal pump, in accordance with an embodiment of the present subject matter. The following description will refer to both figures. The centrifugal pump 100 comprises a pump casing 102, a drive shaft 104, and an impeller 106 which is secured to one end of the drive shaft 104. The drive shaft 104 is generally surrounded by a protective sleeve (not marked in these figures). A stuffing box 108 is mounted on the protective sleeve of the drive shaft 104, between a pump frame (not marked in the figures) and the pump casing 102. The protective sleeve helps to avoid wear of the drive shaft 104 due to friction that would otherwise act between the stuffing box 108 and the drive shaft 104, also referred to as shaft 104. The stuffing box 108 includes a housing marked as a hatched component in Fig. 1A and internal components disposed in the housing, as will be discussed.

[0015] The housing of the stuffing box 108 houses packing 110 and lantern ring 112 positioned radially between an inside surface of the stuffing box 108 and the protective sleeve, also referred to as shaft sleeve. The packing 110 may be generally a rope like material, usually with lubricant in it, and is wrapped around the shaft sleeve and compresses the inner sides of the stuffing box to limit leakage out of the pump casing 102. The lantern ring 112 may be generally a metallic ring placed in between the packing 110 and is drilled with holes to allow lubrication to reach the packing 110. The lantern ring 112 is also used to distribute cooling water, such as small amounts of pumping fluid, to the packing 110. It will be understood that any packing 110 and lantern ring 112 as known in the art may be used in the present subject matter.

[0016] Further, the stuffing box 108 includes ports 114 and 116 to allow pumping fluid to be delivered to the lantern ring 112 for cooling and lubricating the packing 110. In operation, the pumping fluid can enter the clearance between an impeller hub 118 and the stuffing box 108 to enter the port 114. Further, the pumping fluid can enter via impeller balancing holes 120 into the port 116. The pumping fluid thus delivered to the stuffing box 108 helps in cooling and lubrication of the packing 110 and the lantern ring 112. The stuffing box 108 is further described in detail with reference to Fig. 2.

[0017] Fig.2 shows a detailed view of part 200 of a stuffing box with ports for cooling, in accordance with an embodiment of the present subject matter. As shown, the packing 110 and lantern ring 112 are positioned radially between a shaft sleeve 202 and inner wall of the stuffing box 108. The space between the inner surface of the stuffing box 108 and the shaft sleeve 202, in which the packing 110 and the lantern ring 112 are disposed, forms the fluid seal chamber. A gland 204 is provided in the outer end of the stuffing box 108. By tightening or loosening bolts, the gland 204 can be shifted in an axial direction towards or away from the packing 110 to compress the packing 110 to a pre-determined extend between the lantern ring 112 and the gland 204.

[0018] The ports 114 and 116 extend through the housing of the stuffing box 108 and provide a path for pumping fluid to enter the area of the lantern ring 112 and the packing 110 from the pump casing 102. In one example, each of the cooling ports 114 and 116 comprises a flow passage that has a circular or polygonal cross section. In one example, each of the cooling ports 114 and 116 has multiple flow passages. The ports 114 and 116 are further illustrated in Fig. 3.

[0019] Fig. 3 shows detailed view of cooling ports in a stuffing box, in accordance with an embodiment of the present subject matter. For purposes of illustration, the internal components, i.e., the packing and lantern ring, have not been illustrated in the figure, but will be understood to be present in the region 302. Port 114, also referred to as first port 114, is placed in the wear ring seating area at an angle between 25-75 degrees, for example, about 45 degrees, to the central axis of the shaft 104 and it provides lubrication to the lantern ring 112. Port 116, also referred to as second port 116, is placed at certain distance parallel to the first port 114, i.e., at the same angle to the central axis of the shaft 104 as the first port 114, and it provides lubrication to packing 110, which is near to the impeller 106.

[0020] Thus, as per an embodiment of the present subject matter, the pumping liquid enters through the cooling ports 114 and 116, which facilitates cooling and lubrication of the packing 110 and the lantern ring 112, and shaft sleeve 202, thereby reducing heat generated and wear. There are radial openings formed in the lantern ring 112 at locations spaced apart, for example, at a uniform distance, about the circumference and they help in communicating the fluid to the packing 110 and the shaft sleeve 202.

[0021] In operation, flow recirculation occurs in the region of the impeller hub 118. The plurality of cooling ports 114, 116 release the pumping liquid from the region of the impeller hub 118 to the lantern ring 112 and this lubricates the packing 110 and shaft sleeve 202. It helps to improve the life of the packing rope and also reduces liquid recirculation pressure and leakage of pumping fluid to the surrounding atmosphere.

[0022] Thus, the present subject matter provides a generally improved stuffing box with multi flush cooling port in the wear ring seating region that gives continuous supply of pumping liquid to the packing and shaft sleeve, thereby reducing the wear and heat due to friction. It ensures greater life of the packing and shaft sleeve and also reduces the frequency/ requirement of replacement of the gland. Further, the stuffing box of the present subject matter reduces recirculating pressure in the impeller hub and cuts off the leakage to minimize leakage along the peripheral surface of the rotating objects.

[0023] Although embodiments for the stuffing box have been described in language specific to structural features, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features are disclosed as example embodiments.