How to replace gland packing seal

Gland packing seal requires continuous liquid lubrication and cooling between the rotating shaft sleeve and the compressed packing, to prevent over heating due to the friction.

The slurry is not a suitable liquid to provide this function, as the particles would very quickly wear through the protective shaft sleeve. A supplementary external supply of clean flushing water must be provided, to flush the slurry particles away from the seal area, whilst providing the necessary lubrication and cooling required by the packing. The quality, quantity and pressure of this gland sealing water is of prime importance and must be carefully matched to the duty Required.
1, Clean the stuffing box and check whether the shaft surface scratches or burrs. stuffing box should be cleaned and the shaft surface should be smooth.
2, Check shaft run-out, the beating of the rotor unbalance amount should be within the allowable range(0.03~0.08mm), to avoid heavy vibration damage the packing.
3, Rolls packing around one stick which same size with shaft journal, then cut it with 45°bevel.
4, Fill the packing one by one, holding the ends of the packing interface, then pull it away axially, spirally, and then from the incision set into the shaft journal. Shall be opened along the radial to avoid interface arrhythmia.
5,Push the packing deep into the stuffing box. Fill all the packing in same way, when the packing amount is from 4 to 8, it should make the interface staggered 90°and two packing staggered 180°; if only 3 to 6, should make it 120°to 180°, in order to prevent leakage through the interface.
6, Finally tight the gland assembly easily, not in heavy pressure force. Rotating shaft with hand simultaneously in order to make the assembly clamping force tends to parabolic distribution. Then slightly relax the gland, make sure the gap between gland assembly and shaft sleeve is 0.75 to 1mm, the glad assembly and stuffing box is 0.1 to 0.3mm..
7, Running test before continuous operation, if not sealed well, then pressed some more packing; if the fever is too high, then release a little. Until it shows a the Droplets leakage and common fever (not higher than the ambient temperature from 30 to 40℃).

Tags:gland packing, gland packing seal, slurry pump packing

The Leakage Analysis of Slurry Pump Packing Seal Gland Assembly

The packing seal is the most commonly used seal type of slurry pumps, it is composed by packing ring, packing sleeve, packing, packing gland, stud bolts and nuts.

Through the packing and shaft surface contact pressure, it prevents the medium leakage to achieve the purpose of sealing. The existence of many of the small gap and the groove, making it possible to achieve necessary sealing pressure by sufficient pressing forcing the packing material into elastoplastic deformation to reduce the gap between the contact seal surface.

Since there is always a certain degree of roughness in the surface of the shaft, it is not possible with packing to achieve the desired contact, there must be a slight gap exists, thus forming numerous "labyrinth". These fine tortuous gap damping play the role of the media repeatedly throttle and the "labyrinth effect" produced by the stagnation in gap boundary layer and other factors, lead to blocking and achieve sealing.

So, the sealing effect is formed at the obstruction within the gap between the contact surface of the medium into the packing and the pump shaft.

After we know the structure of packing seal, it is easily to get the seal leakage ways:
Leakage through the interface between Packing and Static parts;
Leakage through Packing itself;
leakage through the interface between the Packing and Moving parts.

It is the same way for leakage through static packing surface and leakage type. The leakage of Packing depends on the internal structure of the sealing and penetration itself, the plaiting packing prone to this leakage.

When the infiltration of the media or the media is gas, the penetration leakage through the packing is almost inevitable, but the specific mechanism of this kind leakage will be explored further. For the vast majority of the liquid medium, the leakage mainly through the interface between the packing and the moving parts. For slurry pumps, the large size particles make it difficult to close the small gaps in shaft seal, so,

when pumping the corrosive liquids or the liquids contains corrosive slurry, it will penetrate into the packing seal, these will cause wear and corrosion of the shaft.

Especially when two kinds of materials are constituting the friction pairs in the electrolyte solution, there may occur the galvanic corrosion that is much more accelerated corrosion damage to the shaft. So, when transporting toxic, corrosive and precious liquid, due to the small amount of leakage, and even allowed no leakage, it can not use packing seal.

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