Fitting a gland packing into a gland
Design and use of gland assemblies
A stuffing box consists of a seal, i.e. the stuffing box packing, and a stuffing box cover, through which the stuffing box packing is compressed axially by means of screws or springs. Particularly with an elastic sealing material, the axial compression also results in radial compression of the gland packing against the shaft. This makes it possible to reduce the sealing gap to a minimum, i.e. precisely adapted to the required operating conditions. A small amount of leakage cannot be completely ruled out, but depending on the application – such as with pump shafts – it may even be necessary.
Stuffing boxes are primarily used to seal rotating shafts, for example in centrifugal pumps and agitators. In addition, they are used to seal plungers, i.e. axially moving rods. This includes piston pumps. They are also used to seal spindles. Whether pumps, fittings, pistons, autoclaves, paddle dryers or valves – gland seals are safe and reliable sealing elements.
Types of gland packing for gland boxes
Gland packings, alongside flat gaskets, are among the most reliable and secure seals. They are particularly used in dynamic applications. Gland packings are used to seal sliding surfaces as well as rotating parts.
A major advantage of gland packings is their resistance to pressure and temperature. They can be used at temperatures ranging from -200 to 450 °C. Depending on the material used, they also exhibit good physical and chemical resistance. They are equally suitable for use with abrasive media.
Stuffing box packings are available in various designs for installation in stuffing boxes. They come as double, triple and quadruple diagonal braids with integrated impregnation. Double diagonal braids are also known as plaited braids and have a large, coarse surface. They also exhibit good elasticity. Triple diagonal braids, on the other hand, have a dense braid structure with high dimensional stability. With quadruple diagonal braids, you receive gland packings with a dense braid structure as well as a highly wear-resistant and smooth surface. At the same time, they are very elastic and exhibit high cross-sectional stability.
How are gland packings installed in glands?
Only gland packings that correspond to the respective gland dimensions may be used in glands. If the gland packing is too thin or too thick, it must not be forced to the correct dimensions by tapping or pressing. Likewise, it should be slightly undersized, between 0.1 and 0.4 mm depending on the gland. Under no circumstances, however, is an oversize recommended.
Before a gland packing is fitted into the gland, any remaining packing must be removed and the gland carefully cleaned. It is also important to remove any grooves, dirt or rust deposits on shafts or spindles and to re-polish the affected areas if necessary. The gap between the shaft and the housing should not exceed 0.2 mm. Otherwise, the gland packing could be forced into the gap under pressure.
The gland packing should be cut to size with a sharp knife at a 45° angle before inserting it into the gland . Avoid sawing motions and instead try to cut the packing to the desired length in a single stroke. This prevents fraying. A correct cutting angle can be ensured using a cutting gauge .
The gland packing must then be inserted into the gland. Ensure that only individual packing rings or lengths corresponding to the ring dimensions are inserted. The cut rings must be carefully placed around the
shaft or spindle. The rings are then pressed in individually, using suitable tools such as one- or two-piece sleeves, at right angles to the shaft or spindle axis and compressed. Care should also be taken to ensure that the cut edges of the individual rings are offset by 90° in the gland.
In the next step, the gland packing must be tightened in the gland using the gland nut. It should be noted here that a slight drip is always necessary to prevent overheating or burning of the packing due to frictional heat. It is also advisable to wait a few minutes after each tightening operation to allow the rings sufficient time to adapt to the space within the stuffing box. Once the packing has been fully installed, the packing system should be partially relieved of the force applied by the wrench. The rod or spindle should be operated a few times, even if the process requires greater force. This achieves improved tension distribution. Subsequently, the packing must be tightened again to the maximum preload.
The installation of gland packings in glands requires experience, sensitivity and a careful approach. Sufficient time should also be allowed for the process.
Order gland packings for gland boxes from thoenes®
In the thoenes® online shop, you can find high-quality gland packings. Browse our range and order the right packing for your needs! Alternatively, we also offer other products such as flat gaskets, steam boiler gaskets or mechanical seals. As your trusted partner for innovative and specialised sealing, filtration and lightweight construction solutions, we always fulfil your requirements to the highest standard. Furthermore, we are happy to advise you on any queries regarding our gland packing and other products. Please feel free to contact us!