CN1119037A - Uniformly compressed shaft seal assembly - Google Patents

Abstract

A gland seal assembly for a slurry pump comprising a main body (3) having a bore (4) therethrough for receiving a rotatable shaft (50), a packing receiving zone within the bore (4), the packing including at least two packing rings (8) and a packing sleeve (25) surrounding the packing rings (8) and arranged so that axial compression of the packing sleeve (25) can be translated, at least in part, to radial compression of the packing rings (8).

Description

Uniformly compressed shaft seal assembly

The present invention relates to seal assemblies for pumps, more locally but not exclusively to seal assemblies for centrifugal mud pumps.

Shaft seal assemblies have been used on centrifugal water and slurry pumps for many years. Typical common shaft seal assemblies are shown in Figures 1, 2 and 3. Figures 1, 2 and 3 are partial cross-sectional views of conventional shaft seal assemblies. Such assemblies generally comprise a housing 2, commonly referred to as a stuffing box, with a circular bore 4 through which a rotatable shaft 50 passes. For example, shaft 50 may be the shaft of a pump. An end wall 35 is provided at one end of the hole. The shaft 50 may or may not be provided with a protective sleeve. The annular gap 7 between the hole 4 and the shaft 50 is generally filled with a packing 5 which may be several packing rings 8 . The packing can vary according to the application, but it is generally woven of fibers, has a square or rectangular cross-section, and can be cut into rings. Fillers can be selected according to strength requirements, and other lubricants (such as polytetrafluoroethylene) can be added to reduce friction.

The stuffing 5 is generally placed in the casing, that is, the stuffing box, and is compressed by the stuffing cover 9 from the outside. Due to the compressibility of the packing 5, the gap between the packing 5 and the shaft (or its sleeve) 50 can be adjusted by moving the packing cap 9 into and out of the annular gap 7 constituting the packing space. This adjustment is typically made via external bolts (not shown). Adjusting the gap 7 between the stationary packing 5 and the rotating shaft 50 can control leakage from the assembly. In some applications, this leakage may be critical to ensure proper cooling of the packing and shaft and carry away the heat generated by friction.

When used in a water pump, such a seal assembly can utilize pumped liquid that leaks from the seal assembly during operation to help cool the assembly. Well lubricated components are essential for long life.

Since the mud pump is used to pump mud that contains particles, this creates additional problems. These particles cause additional friction and wear on the packing and bushing. For mud pumps, it is generally necessary to inject clean sealing water into the components from an external water source to reduce the above problems and ensure a long life. Water is injected into the assembly through delivery channel 14 up to a Lantern ring assembly 10. The collar assembly may include a collar 10 and a restriction 12 . In FIG. 1, the throttle member 12 is made of metal, and in FIG. 2, it is a non-metallic member. In Figure 3, a set of rings 11 is spaced apart from a neck ring 17 by means of packing 8D. The collar and restriction direct the water introduced through passage 14 into a gap around the shaft or bushing. This allows water to enter the demanding clearance between the packing and shaft 50 for proper and effective lubrication. The collar and orifice assembly allows some seal water to flow into the pump. This allows particles to be flushed away from the seal assembly, thereby reducing the risk of mud contaminating the interior of the shaft seal assembly.

The conventional shaft seal assemblies described above have inherent structural problems that also cause mud working and maintenance problems. For example, the structures described above typically have uneven compression across each packing ring. High voltages can exacerbate this problem. Generally, one or two packing rings will be more squeezed by the packing cap than the other packing rings, making the sealing and wear uneven. Additionally, water usage can vary widely depending on operator adjustments, the type of packing used, and other variables. Some processes rely on drying the pumped solids in the slurry by removing water. Therefore, the use of additional water adds expense to the subsequent treatment stages. Another problem arises because the operator cannot always ensure proper adjustment. The water source may vary and even lead to wear failures of the packing and bushings. Water may also leak around the radially outer side of the packing instead of its radially inner side.

It is an object of the present invention to overcome one or more of the above-mentioned problems of conventional seal assemblies.

A shaft seal assembly suitable for a mud pump according to the present invention includes a main body having a through hole for receiving a rotatable shaft, a packing receiving area in the through hole, packing including at least two packing rings, and surrounding A packing sleeve for a packing ring arranged such that axial compression of the packing sleeve is at least partially translated into radial compression of the packing ring.

The packing sleeve preferably includes an elastomeric ring disposed between the packing ring and the inner surface of the bore. In one form of the invention, the packing jacket may have a substantially annular peripheral wall. In another form, the packing sleeve may include an outer peripheral wall with a radially inwardly extending side wall at one end of the outer peripheral wall, and in the assembled position, the side wall may be arranged in a lateral direction of the packing. Extend down.

In one preferred form, there are two sets of packing rings, each set cooperating with one of the aforementioned packing sleeves. The two sets of packing rings may be spaced apart from each other by a collar assembly or similar structure. In a preferred arrangement, said collar comprises a first portion fitted between two sets of packing rings and a second portion shaped to compress the packing sleeve in the installed position. An O-ring or similar device may also be provided between the collar and the housing to form a seal.

The housing can have any suitable structure. For example, the housing may include a body having a through hole for receiving a rotatable shaft. The body may include first and second portions, each portion having a filler receiving area in the through hole. Each of the first portion and the second portion includes an end wall and abutment wall constituting the above-mentioned packing receiving area. Adjustment means are also provided for causing a relative movement between the abutment walls in the axial direction of the through-hole.

The packing receiving area may comprise an annular gap between the inner surface of the through-bore and the outer surface of the rotatable shaft in the assembled position.

Each abutment wall may include a flange extending substantially radially inwardly relative to the inner surface of the through-hole. A flange against the wall is preferably formed on the first and second parts of the housing. When in the assembled position, the above-mentioned abutment walls are spaced apart from each other. The apertures in each portion of the housing may be relatively open and may be spaced slightly from each other to accommodate the collar assembly therebetween.

The flange of each abutting wall has a free inner edge which, in the assembled position, is adjacent to the surface of the shaft and which, by itself and/or in cooperation with the collar, acts as a flow restrictor. Preferably a plurality of packing rings are arranged in each housing part.

A part of the casing is preferably fastened to the pump casing together with another part operatively connected to the pump casing, which can move axially relative to the first-mentioned part due to the operation of the adjusting means.

The adjustment means may be in the form of a plurality of bolts connecting the first and second parts of the housing, rotation of these bolts causing axial movement of the two parts. Additionally, at least one of the two parts of the housing has two sections connected by bolts arranged so that the two parts can be separated to facilitate access and removal of the housing.

A preferred embodiment of the invention will now be described with reference to the following drawings:

Figure 4 is a partial side view of a shaft seal assembly according to the present invention;

Fig. 5 is a front view of the shaft seal assembly shown in Fig. 4;

Figure 6 is a view similar to Figure 4, showing a variant of the assembly according to the invention;

Figures 7-9 are side views of a modified collar which may form part of the shaft seal assembly of the present invention.

Referring now to Figures 4 and 5, the assembly of the present invention includes certain features similar to those of the conventional seal assembly, and the same reference numerals are used for like features. The purpose of the seal components of a pump is essentially to contain the pumped liquid under pressure. The pressure is damped by the seal assembly to bring the pressure to atmospheric pressure outside the seal.

The sealing housing, the stuffing box 2 , has a bore 4 parallel to the rotatable shaft 50 and forms an annular gap 7 . The stuffing box 2 comprises a main body 3 comprising a first part 3A and a second part 3B. The abutment walls are in the form of flanges 14 and 15 each having inner edges 16 and 17 . The inside diameter of the stuffing box is close to the diameter of the shaft. The inner rims 16 and 17 by themselves and/or with the neck ring act as a flow restricting gap to assist the water to wash away the mud. The abutment walls 14 and 15 also form a shoulder supporting the packing 5 . Stuffing boxes are generally metal, but other suitable materials may be used, and may be made of low abrasive materials such as High Chrome Iron (High Chrome Iron), because it can withstand the abrasion of mud.

Shaft 50 is typically protected by a hard metal sleeve or plated sleeve to reduce wear.

The arrangement of the two parts 3A and 3B of the main body 3 is such that adjustment means in the form of bolts 21 allow the position of these two parts to be adjusted axially relative to each other, thereby varying the compression of the packing 5, controlling the distance between the packing and the sleeve or shaft. The gap, thus controlling the leakage of the sealing assembly. The bolt 21 is carried on the flange 32 of the part 3B.

Unlike conventional devices, the abutment walls do not enter the bore of the stuffing box, they form an annular sealed chamber on the inner diameter. Housing part 3B is split into two halves as shown, fastened together by retaining bolts 23, and part 3A can be similarly split. During maintenance, the housing parts can be separated and removed from the shaft 50, thereby allowing easy access to the outer housing.

A collar 55 separates the two ends of the housing parts 3A and 3B. Its outer diameter is within the bore diameter of the shell, ie the stuffing box, to assure and maintain concentricity. The collar can generally be metal, but can also be plated or inserted on the inner diameter to reduce wear on the shaft or bushing. Radial holes or annular grooves on the inside diameter allow water to be injected into the gap between the packing and the shaft or sleeve on both sides of the collar. Therefore, water can flow into the pump as well as to the outside world.

The new structure described above can utilize any common packing type. These packings are usually braided rings cut through in one place to fit over the bushing. The number of packing rings 8 can vary at both ends. There are two packing rings at each end as shown.

As shown in Figures 4 and 6, there are packing sleeves 25 around the packing at both ends of the sealing assembly. As shown, two packing sleeves 25 each have a packing ring set 8A and 8B. The above-mentioned packing sleeves 25 are elastic, so that the axial pressure caused by the relative movement between the two parts of the housing will first compress these packing sleeves axially. The packing sleeve 25 shown in FIG. 4 is substantially annular with a peripheral wall. The stuffing sleeve shown in FIG. 6 has an outer peripheral wall and a side wall extending radially inward from one end of the outer peripheral wall. In the assembled position, the side walls of the packing sleeve are sandwiched between the abutting wall of the housing and the packing ring. In another arrangement not shown, the sidewall of the packing sleeve is positioned adjacent to the collar assembly. Since the packing sleeve is essentially between the shell 3 and the packing 5, the axial compression will be transformed into the radial compression of the packing. As a result, the packing will be compressed both axially and radially, and the compression will be more uniform from ring to ring. More even compression on each packing ring will provide much better control over seal assembly and operation and leakage. The packing sleeve will help seal around the outside of the packing ring and prevent uncontrolled leakage.

Figures 7 to 9 illustrate various forms of collars which are particularly suitable for use with the shaft seal assembly of the present invention. In each case, the collar 55 comprises a first portion 55A fitted between the groups of packings 5 and an enlarged portion 55B acting on the packing sleeve 25 so as to partially compress the packing sleeve 25 .

In the embodiment shown in Figures 8 and 9, an O-ring 40 fits between the collar 55 and the housing 3A/3B to form an additional seal.

The above arrangement in accordance with the preferred embodiment provides better seal water control, reduced water usage, improved life, reduced mud intrusion, and more uniform wear. The bushing wear is distributed over all the packing rings, rather than being concentrated at one end as in common stuffing box construction, which proves that the packing is evenly compressed. The measured shaft seal water injected into the shaft seal can be lower than that of the common shaft seal structure without affecting the work. This configuration also controls the amount of shaft seal water that flows into and out of the pump's injection shaft seal. In addition, this arrangement provides easier access to the packing rings and reduces the length of the fixed annular seal chamber for easier maintenance.

It is obvious that various modifications, changes and additions can be made to the above structures and arrangements without departing from the scope of the present invention.

Claims (8)

1. gland seal assembly that is used for slurry pump, it comprises a main body with the through hole that holds rotating axle, filler in through hole holds the district, the filler that comprises at least two packing rings, around the filler cover of described packing ring, the axial compression that its layout is overlapped filler can change into the radial compression to described packing ring at least in part.

2. gland seal assembly as claimed in claim 1 is characterized in that: described filler cover comprises the elastic ring that is arranged between described packing ring and the described through-hole inner surface.

3. gland seal assembly as claimed in claim 1 or 2 is characterized in that: described filler cover comprises ringwise substantially perimeter wall.

4. gland seal assembly as claimed in claim 1 or 2 is characterized in that: described filler cover comprises a perimeter wall, and described perimeter wall one end has the sidewall that extends radially inwardly.

5. the described gland seal assembly of arbitrary as described above claim is characterized in that: be provided with two groups of packing rings, every group with one of described filler cover cooperating.

6. gland seal assembly as claimed in claim 5 is characterized in that: described filler group is come by a collar space.

7. gland seal assembly as claimed in claim 6 is characterized in that: the described collar comprises first portion and second portion that is assemblied between the described filler group, and its shape makes compresses described filler cover when the mounting point.

8. gland seal assembly as claimed in claim 7 is characterized in that: also be provided with O shape ring or like parts, be formed on the sealing between the described collar and the housing.

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