Since 1992, the company produces sealings for pumps and armature from expandable graphite.
The gland rings from expandable graphite, are the most recent material designed for sealing industrial armature glands and rotodynamic pumps with good working parameters, high reliability and durability, at a reasonable price. Because the material is free of any binders and fillings, it maintains its properties in a wide range of temperatures, pressures and sealing media.
The linear velocity can be determined from "w" factor, it being the multiplication of the operating pressure and the linear slip velocity:
The number of rings in the case is dependent on the sealing pressure, the seal structure and the sealing device. The table below allows us to choose the number of rings in the gland chamber, when the rings height is equal to its width.
|sealing pressure||number of rings|
|up to 4||4|
|up to 10||5|
|up to 40||6|
|up to 6.3||4|
|sealing pressure||number of rings|
|armature and pumps|
|up to 4||2|
|up to 16||3-4|
|up to 40||4-6|
The length of the gland chambers can be shortened by enclosing the spacers.
|diameter tolerance||H8 to H11||H8|
|roughness Ra||2,5 to 6,3||max 2,5|
|spindle / shafts|
|diameter tolerance||h7 to h9||h7|
|radial beating||to 0,08||to 0,4|
|hardness HR||-||40 to 50|
Gland rings from expandable graphite are made in industrial cleanness, with an ash content of 2.0%. For special appliances like e.g. nuclear energy or high concentrated oxygen atmosphere, graphite containing no more than 0.15% is used. They are made only on special orders. If the graphite purity is not specified in the order, the rings will contain industrial levels of ash.
|Criteria||Unit||Indust purity||special purity|
|density||g/cm3||from 1,4 to 1,6|
|ash content||%||to 2,0%||to 0,15%|
|chloride content||ppm||from 50||to 20|
|heat conductivity in 20°C|
|parallel to the plates||W/mk||155|
|perpendicular to the plates||W/mk||4,8|
|linear expandability coefficiency|
between 20 and 1000°C
|residual stress W/g DIN 52 913||%||minimum 48|
After placing the specified number of rings in the gland chamber, pull the choke lightly, move the spindle a few times and tighten the choke until the tension in the gland is reached. (calculate the tension using the torque spanner)
|Sealing pressure||Ring tension in the gland|
|4 MPa||20-30 MPa|
|16 MPa||40-60 MPa|
|40 MPa||70-100 MPa|
After placing the specified number of rings in the chamber, the screws of the choke need to be tightened manually. After starting the pump and reaching operating parameters, tighten the choke in a way to reach a spill in a range between 50 and 500 drops per minute. It's beneficial to start up the pump for a dozen or so seconds, turning it off for a couple of minutes and repeating the process a couple of times. After running the pump for around half an hour, it's possible to reduce the leakage again. To do that, tighten the screw of the choke by 1/6 of a spin, all while controlling the temperature and the size of the leakage. In case of a rapid temperature increase or interruption of the leakage, immediately loosen the choke. The minimal acceptable spill is dependent on the pumps working condition, but it should be between 10 and 100 drops per minute.
Both in armature and in pumps, it's recommended to use closed up rings, but in situations when it's impossible to use them (e.g. in renovations) they can be replaced with seals cut in one place at a 45° angle. This kind of rings can be parted axially and mounted on a pin or a pumps shaft. Some dissection of the ring on the opposite side of the cut is acceptable. It's important to place the seals in the gland in such a way, that the discontinuities are spaced from each other by 60° or 90°. angles.