Claims:We Claim:

1. A centrifugal type slurry pump for handling iron ore ground slurry avoiding slurry leakage comprising:
a rotating impeller shaft and stationary casinghaving gland seal arrangement with pressurised gland water involving compressed packing including slurry pump stuffing box as housing having an outer lip seal andleakage blocking inner leak seal and lantern ring assembly, gland water inlet, gland rope combinations , gland follower, tightening bolt & pump shaft sleeve.

2. A centrifugal type slurry pump for handling iron ore ground slurry avoiding slurry leakage as claimed in claim 1 wherein said leakage blocking inner leak seal and lantern ring assembly comprise annular lantern ring circumscribing said shaft having a flanged circular extensionproviding for deformation free housing of said inner lip seal therein.

3. A centrifugal type slurry pump as claimed in anyone of claims 1 or 2 comprising said gland sealing arrangement adapted to prevent leakage of slurry due todamage of seal comprising

a stuffing box mounted on a shaft sleeve to house the gland sealing elements with compressed packing comprising,
an outer lip seal disposed closer to pump casing,
an inner lip seal cooperatively mounted in the recess within a lantern ring disposed on opposite side of pump casing,
a plurality of gland ropes disposed one after another in succession next to the lantern ring and away from the pump casing,
inbuilt flow passage in said stuffing box for introducing gland water under pressure, and
a gland follower with cooperative tightening bolt to secure the gland seal system within said stuffing box in a manner to prevent damage of seal due to ingress of foreign particles.

4. A centrifugal type slurry pump as claimed in anyone of claims 1 to 3 comprising said gland sealing arrangementwherein said lantern ring is configured to provide an annular recess suitably dimensioned to house the inner lip seal.

5. A centrifugal type slurry pump as claimed in anyone of claims 1 to 4 comprising said gland sealing arrangementwherein said recess in lantern ring is preferably 15mm wide to accommodate the corresponding width of inner lip seal such as to withstand the pressure applied by tightening of bolt of said gland follower without deformation.

6. A centrifugal type slurry pump as claimed in anyone of claims 1 to 5 comprising said gland sealing arrangementwherein number of said gland ropes in the gland sealing system is preferably three.

7. A centrifugal type slurry pump as claimed in anyone of claims 1 to 6 comprising said gland sealing arrangementwherein said stuffing box is secured on the pump casing in a leak proof manner.

8. A centrifugal type slurry pump as claimed in anyone of claims 1 to 7 comprising said gland sealing arrangement wherein the lip seals are preferably made of Nitrile rubber material.

9. A centrifugal type slurry pump as claimed in anyone of claims 1 to 8 comprising said gland sealing arrangementwherein the lantern ring is preferably made of brass material.

10. A centrifugal type slurry pump as claimed in anyone of claims 1 to 9 comprising said gland sealing arrangement wherein the gland ropes are preferably made of PTFE (Polytetrafluoroethylene) poly teflon packing rope material.

11. A centrifugal type slurry pump as claimed in anyone of claims 1 to 10 comprising said gland sealing arrangementwherein inside the stuffing box gland water is equally distributed by lantern ring on either sideto ensure gland water is flowing from lantern ring to lip seal and towards pump casing, at a pressure of gland water maintained above discharge pressure of slurry pump, so that only water is coming in contact with gland seal arrangement and not the slurry.

Dated this the 21st day of November, 2018
Anjan Sen
Of Anjan Sen & Associates
(Applicant’s agent)
IN/PA-199
, Description:FIELD OF THE INVENTION

The present invention relates to a centrifugal type slurry pump for handling iron ore ground slurry having modified gland seals arrangement, avoiding slurry leakage wherein said gland seal is adapted to prevent the leakage of highly abrasive iron ore slurry from the spacing between the rotating impeller shaft and stationary casing. More particularly, the present invention is directed to improve MTBF (Mean time between failures) of the centrifugal slurry pump provided with said gland sealing system. The modified system according to the invention thus would improve the equipment availability.

BACKGROUND OF THE INVENTION

In the steel plant of the applicant, conventionally centrifugal slurry pumps are used for medium head slurry pumping application wherein generally three types of seals are used:
1. Gland with compressed packing.
2. Centrifugal expeller seals.
3. Face type mechanical seals.
Out of these, Gland with compressed packing are the most common andwerein use prior to the invention.
Gland seal with compressed packingconsists of slurry pump stuffing box which acts as housing for lantern ring, lip seal, gland water inlet, first gland rope, second gland rope, third gland rope, fourth gland rope, gland follower, gland follower tightening bolt & pump shaft sleeve(as indicated in fig. no. 2).

In the existing slurry pump there is stuffing box (fig. No 1), typical stuffing box contains 4 gland ropes & one lantern ring (fig. No. 2). Inside stuffing box gland water is equally distributed by lantern ring on either side.Slurry have direct contact will lip seal and it prevents slurry from entering into the gland. To ensure gland water (through passage-part no. 4 of fig.no 2)is flowing from lantern ring to lip seal & towards pump casing, pressure of gland water is maintained above discharge pressure of slurry pump. This ensure only water is coming in contact with gland seal arrangement (not the slurry). Water also act as lubricant and cooling agent for gland seal arrangement.

Deficiency of the existing system
Applicant’s steel manufacturing plant have common handling system for handling of all raw materials (i.e Iron ore, Lime Stone, Coke, Coal, Dolomite etcetera) required for steel making. During iron ore grinding, ingress of foreign material in slurry is prevalent condition. Therefore, Slurry handled by pumps had contamination (coarser light weight particles) in the form of woods, sand stones, rubber, coal and coke. These coarser particles used to come directly in contact with the lip seal (part no 3 of fig. no 2 called Radial shaft seals, also known as lip seals made of Nitrile rubber), which are used to seal rotary elements, such as a shaftsleeve.

The said centrifugal type slurry pump is used to pump iron ore slurry (ground iron ore mixed with water)from one equipment to other. Iron ore slurry typically have density ranging from 2.1 to 2.3gm/ cc & is highly abrasive in nature. As discharge pressure at pump is normally 8 to 9bar & to prevent the slurry leakage between the rotating impeller shaft and stationary casing, agland seal arrangement with gland water is provided as shown in the fig.2. Gland water pressure is maintained 1.5 to 2bar more than the slurry pressure, in order to avoid slurry entry into the seals.

In the existing slurry pump there is stuffing box (fig. No 1), typical stuffing box contains 4 gland ropes (part no. 6,7,8 & 9 of fig. no. 2) & one lantern ring (fig. No. 2). Inside stuffing box gland water is equally distributed by lantern ring. Due to coal contamination the above said arrangement was prone to premature failure (less than 3 months against industry norms of 6 months).

Inside stuffing box gland water is equally distributed by lantern ring. Due to coal contamination the above said arrangement failed to perform to the guaranteed level.

Once the primary lip seal gets damaged, foreign particles used to damage 1st gland rope. Once the 1st gland rope is damaged, lantern ring used to get damaged sooner. When the lantern ring damaged the whole assembly fails immediately.

This situation ledto the below mentioned operational problems:
1. Leakage of slurry from the pump.
2. Frequent breakdown of the pump.
3. Higher maintenance cost.
4. Slippery floor due to slurry accumulation.

There has been thus a need to develop an effective glad sealing system for safe and reliable operation of slurry handling centrifugal pumps in order to avoid ingress of foreign contaminants in stuffing box and thus causing failure of the gland sealing system and disrupt the material handling system,adversely affecting the productivity of plant.

OBJECTS OF THE INVENTION

The basic object of the present invention is directed to provide a centrifugal slurry handling pump havingmodified gland sealing system adapted to prevent ingress of foreign contaminants including highly abrasive iron ore slurry in stuffing box and therebyprevent damage of sealing system and consequent leakageof slurry from the spacing between the rotating impeller shaft and stationary casing.

A further object of the present invention is directed to a centrifugal slurry handling pump having modified gland sealing system which would ensure uninterrupted reliable and longer operation of the pump without failure of seal to thereby ensure improved MTBF (Mean time between failures)from existing 2 months to 6 months and hence increased equipment/plant availability.

A still further object of the present invention is directed to a gland sealing system for centrifugal slurry handling pump which would replace existing 1st (inner) gland rope with a second inner oil seal/lip seal (acts as NRV), in addition to the existing primary lip seal, thus avoiding slurry to enter inside the second gland rope through lantern ring.

A still further object of the present invention is directed to a gland sealing system for centrifugal slurry handling pump which would provide said additional inner lip seal resistant to deformation under gland water or follower pressure, being placed within a recess created on inner face of lantern ring with modified configuration and prevent damage of lantern ring or leakage of slurry.

A still further object of the present invention is directed to a gland sealing system for centrifugal slurry handling pump which would ensure less installation and maintenance cost with reduced frequency of repair/ replacement of the pump gland seal assembly.

SUMMARY OF THE INVENTION
The basic aspect of the present invention is directed to a centrifugal type slurry pump for handling iron ore ground slurry avoiding slurry leakage comprising:
a rotating impeller shaft and stationary casinghaving gland seal arrangement with pressurised gland water involving compressed packing including slurry pump stuffing box as housing having an outer lip seal andleakage blocking inner leak seal and lantern ring assembly, gland water inlet, gland rope combinations , gland follower, tightening bolt & pump shaft sleeve.

A further aspect of the present invention is directed to a centrifugal type slurry pump for handling iron ore ground slurry avoiding slurry leakage wherein said leakage blocking inner leak seal and lantern ring assembly comprise annular lantern ring circumscribing said shaft having a flanged circular extension providing for deformation free housing of said inner lip seal therein.

A still further aspect of the present invention is directed to said centrifugal type slurry pump comprisingsaid gland sealing arrangement adapted to prevent leakage of slurry due to damage of seal comprising

a stuffing box mounted on a shaft sleeve to house the gland sealing elements with compressed packing comprising,
an outer lip seal disposed closer to pump casing,
an inner lip seal cooperatively mounted in the recess within a lantern ring disposed on opposite side of pump casing,
a plurality of gland ropes disposed one after another in succession next to the lantern ring and away from the pump casing,
inbuilt flow passage in said stuffing box for introducing gland water under pressure, and
a gland follower with cooperative tightening bolt to secure the gland seal arrangement within said stuffing box in a manner to prevent damage of seal due to ingress of foreign particles.

A still further aspect of the present invention is directed to saidcentrifugal type slurry pump comprising said gland sealing arrangementwherein said lantern ring is configured to provide an annular recess suitably dimensioned to house the inner lip seal.

Another aspect of the present invention is directed to saidcentrifugal type slurry pump comprising said gland sealing arrangementwherein said recess in lantern ring is preferably 15mm wide to accommodate the corresponding width of inner lip seal such as to withstand the pressure applied by tightening of bolt of said gland follower without deformation.

Yet another aspect of the present invention is directed to saidcentrifugal type slurry pump comprising said gland sealing arrangementwherein the number of said gland ropes are preferably three.

A further aspect of the present invention is directed to acentrifugal type slurry pump comprising said gland sealing arrangementwherein said stuffing box is secured on the pump casing in a leak proof manner.

A still further aspect of the present invention is directed to saidcentrifugal type slurry pump comprising said gland sealing arrangement wherein the lip seals are preferably made of Nitrile rubber material.

A still further aspect of the present invention is directed to saidcentrifugal type slurry pump comprising said gland sealing arrangementwherein the lantern ring is preferably made of brass material.

A still further aspect of the present invention is directed to saidcentrifugal type slurry pump comprising said gland sealing arrangement wherein the gland ropes are preferably made of PTFE (Polytetrafluoroethylene) poly teflon packing rope material.

A still further aspect of the present invention is directed to said centrifugal type slurry pump comprising said gland sealing arrangementwherein inside the stuffing box gland water is equally distributed by lantern ring on either side to ensure gland water is flowing from lantern ring to lip seal and towards pump casing, at a pressure of gland water maintained above discharge pressure of slurry pump, so that only water is coming in contact with gland seal arrangement and not the slurry.

The above and other objects and advantages of the present invention are described hereunder in greater details with reference to the following accompanying non limiting illustrative drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig 1: shows a sectional view of existing slurry Pump with disposition of its various parts.
Fig 2: shows schematically the existing Gland Seal Arrangement with indication of different components marked with respective reference numerals.
Fig 2a: shows the flow path of gland water in existing gland seal and its uniform distribution through packing and lip seal.
Fig 3: original Pump stuffing Box.
Fig 4: Original Pump lantern Ring.
Fig 5: Original Pump Lip Seal.
Fig 6: Original Pump Gland rope/Seal.
Fig 7: Modified Gland Seal Arrangement.
Fig 8: Modified stuffing box.
Fig 9: Modified lantern ring.
Fig 10: Modified lip seal.
Fig 11: Gland rope.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS

The present invention is directed to provide a centrifugal type slurry pump for handling iron ore ground slurry, comprising modified gland sealing arrangement which is used for handling slurry containing abrasive particles, adapted to prevent damage of gland seal and resulting leakage from gap between the rotating impeller shaft and stationary casing.

Accompanying Figure 1 and 2 illustrates the existing slurry pump having Gland seal with compressed packing. Figure 1 show the various components of the slurry pump including the disposition of existing stuffing box and the gland seal housed therein. As already described herein above, that gland seal system consists of slurry pump stuffing box which acts as housing for lantern ring, lip seal, gland water inlet, first gland rope, second gland rope, third gland rope, fourth gland rope, gland follower, gland follower, tightening bolt & pump shaft sleeve as indicated in fig. no. 2.

Accompanying Figure 2 illustrates the disposition of following items in the existing gland seal system:
1. SLURRY PUMP STUFFING BOX.
2. LANTERN RING.
3. LIP SEAL.
4. GLAND WATER INLET.
5. FIRST GLAND ROPE.
6. SECOND GLAND ROPE.
7. THIRD GLAND ROPE.
8. FOURTH GLAND ROPE.
9. GLAND FOLLOWER.
10. GLAND FOLLOWER THIGHTENING BOLT.
11. PUMP SHAFT SLEEVE.

In the existing slurry pump there is stuffing box (fig. No 1), typical stuffing box contains 4 gland ropes & one lantern ring (fig. No. 2). Inside stuffing box gland water is equally distributed by lantern ring on either side.Slurry have direct contact will lip seal and it prevents slurry from entering into the gland. To ensure gland water (through passage-part no. 4 of fig. -no 2)is flowing from lantern ring to lip seal & towards pump casing, pressure of gland water is maintained above discharge pressure of slurry pump. This ensure only water is coming in contact with gland seal arrangement (not the slurry). Water also act as lubrication and cooling agent for gland seal arrangement. Accompanying figures 2a shows the gland water flow path and Figures 3-6 show the details of the existing gland seal components.

During iron ore grinding, ingress of foreign material in slurry is prevalent condition. Therefore, Slurry handled by existing pumps had contamination (coarser light weight particles) in the form of woods, sand stones, rubber, coal and coke. These coarser particles used to come directly in contact with the lip seal (part no 3 of fig. no 2 called Radial shaft seals, also known as lip seals (Material of construction - Nitrile rubber)), which are used to seal rotary elements, such as a shaft sleeve.
Due to contamination by abrasive slurry, the above said arrangement was prone to premature failure (less than 3 months against industry norms of 6 months). This was leading to the problems likeLeakage of slurry from the pump, frequent breakdown of the pump, Higher maintenance cost and Slippery floor due to slurry accumulation.

The present invention thus provides for a gland sealing system for slurry pump with modified configuration that not only prevents ingress of foreign contaminants including highly abrasive iron ore slurry in stuffing box but alsoprevent damage of sealing system and consequent leakage of slurry, ensuring reliable operation of slurry pump with the purpose of improving MTBF.

The target was to protect the lantern ring and gland ropes from damage due to ingress of contaminants by providing a modified configuration of the gland sealing system.

Accompanying Fig 7 illustrates a preferred embodiment of modified Gland Seal Arrangement according to present invention comprising the following components as indicated in the figure.
1. SLURRY PUMP STUFFING BOX.
2. LANTERN RING.
3. INNER LIP SEAL.
4. OUTER LIP SEAL.
5. GLAND WATER INLET.
6. FIRST GLAND ROPE.
7. SECOND GLAND ROPE.
8. THIRD GLAND ROPE.
9. GLAND FOLLOVER.
10. THIGHTING BOLT.
11. PUMP SHAFT SLEEVE.
Accompanying Figures 8 to 11 show the structural details of the components of the gland sealing system comprising stuffing box, modified lantern ring, inner lip seal and gland ropes used in the modified gland sealing system.

Thus according to present invention followingstep by step modifications were implemented in the gland sealing system of slurry pump to prevent ingress of foreign abrasive particles of slurry in stuffing box causing frequent damage of gland seal system:
1. Observing that once the primary lip seal gets damaged in existing gland sealing system, foreign particles used to damage 1st gland rope. Once the 1st gland rope is damaged, lantern ring used to get damaged. Whole gland seal assembly fails immediately when lantern ring is worn out. A low cost modification of the gland sealing system was thus explored to eliminate the problem.

2. Lip seal being a low cost spare, its efficient utilization was considered to be a means for cost effectivemodification of the gland seal system to avoid the problem.

3. As a preventive step, one more lip seal is introduced (part no.3, fig. no. 7), on inner side of the stuffing box in order to increase the life of lantern ring (part no. 2, fig. no. 7).

4. The 1stgland rope next to lantern ring (in existing configuration) was removed simultaneously to make provision for the required space for the additional lip seal.

5. There being possibility of deformation of newly introduced lip seal due to high pressure from the gland follower (part no 10, fig. no. 7) when tightened with bolt, further modification was necessary.

6. In order to protect newly introduced lip seal (part. No. 3, fig. no. 7), from deformation, design of lantern ring has been changed to provide an annular space to house the lip seal as shown in fig. no 08. Lantern ring is extended by 15mm& this dimension is chosen to house newly introduced (part. No. 3, fig. no. 7) lip seal. Thus avoiding any pressure from gland follower and resultant damage of the inner lip seal due to tightening of gland follower.

7. This modification in gland sealing system effectively protected the lantern ring, and gland ropes avoiding damage due to ingress of foreign particles and thus improved the MTBF from existing 2 months to up to 6 months.

It is thus possible by way of the present invention to provide a gland sealing system for slurry pump for handling abrasive slurry adapted to prevent damage of seal due to ingress of foreign particles/abrasive contaminants and leakage of slurry therefrom and consequent operational problem. The gland sealing system thus ensure longer operation of slurry pump without needing frequent repair and maintenance improving the MTBF and plant availability.