About Us

About Us

Carbon And Graphite Supplier

Applications

As carbon Jamuna Carbon  gland Rings are extensively used in steam turbines broth as pressure seals in high pressure (HP) glands and vcuum seals in low pressure (LP) glands. They also find many applications as air gas seals in industrial particular advantages in these applications may be summarized as follow: 

Sealing with carbon gland rings is efficient. The carbon gland rings can b  mounted, safely, with a smaller clearance than is possible with the  alternative metallic labyrinth seal where metal to metal contact must be prevented under all working conditions.

This high sealing efficiency can be obtained with limited axial length.

Carbon gland rings are not affected by axial movement of the shaft relative to the gland, and also can accommodate considerable radial displacement of the shaft from its normal axis without danger of seizure or loss of sealing efficiency.

Carbon gland rings are inexpensive, both in purchase price, installation and maintenances costs. Our manufacturing technique ensures an accuracy which permits all segments of identical rings toe be completely interchangeable. Rings which have been correctly specified can be fitted directly to the shaft without further hand fitting or adjustment; they will require little or no maintenance and in many cases survive several normal turbine overhauls.

Operating Conditions

Number of rings per gland and sealing pressure

A complete gland is built up of a number of gland rings in separate housing compartments. Normally, however, the entire first state pressure of a HP reaction turbine is broken down labyrinth seals on the balance piston of dummy piston t a comparatively low pressure corresponding to on of the exhaust end stages. When this arrangement has  been made, it is then customary to fit at least two carbon gland rings between the balance chamber and the gland steam leak-off  annulus,  and a third ring between the leak-off and atmosphere, where a `goose-neck’ or sighting vent is fitted,  a further ring is required beyond the vent connection to prevent steam and water flowing toward the bearing.

Vacuum sealing glands are similar, except that  steam is supplied to the central annulus for `packing’ the gland and the tendency for leakage is both towards the turbine and towards the atmosphere. Frequently the packing steam is taken from a HP Main through a reducing valve and necessitates the use of high temperature carbon materials for the LP as well as the HP gland. In this case we would recommend the use f a high temperature electro-graphite carbon material throughout. Generally the differential pressure across the carob gland rings will not exceed2.1 kgf/Cm2. The small leakage past each ring helps to equalize the pressure drop, but  for high pressure drop, but for high pressure sealing it is desirable to arrange controlled pressure balancing leak of connections to various turbine stages which will enforce equalization of pressure. In this way, pressures to several hundred pounds per square inch can be effectively sealed by carbon gland rings. Fan and  blower seals dealing with air and gas are usually low pressure seals and often a single check kings is fitted, although for more important-gland tow rings are considered a desirable minimum.

Shaft Speeds

Steam turbine shaft speeds may result in surface velocities  up to 50.8m/sec(10,000ft/min). Provide that the initial cold clearance is correctly assessed, a `but-jointed’ ring that does not make contact under the pressure with the shaft is satisfactory fro normal steam turbine shaft speeds. The inherent self lubricating property of carbon will permit contact without under frictional heating at these speeds. However. for very high surface speeds, or for high rotational speeds with small diameter shaft (conditions which are frequently a feature of gas turbine and compressor applications), the 'carbon labyrinth' gland which is discussed later, has particular advantages.

Temperature and Oxidation Resistance

Our CY (carbon-graphite) grades are suitable for gland rings operating in super=heated steam at temperatures up to 350'C (6602F). CY grades combine homogeneity with high mechanical strength and good self-lubricating properties. in normal conditions where the oxygen content of the steam is low, and where there is infrequent subjection to atmospheric contamination at high temperature, this grade has proved capable of withstanding the disintegrating action of steam at 400-C (725' F) for periods extending to several normal turbine overhauls. Glands which will be required to work under greater steam temperatures or, conversely, subject to more than the normal moderate oxidising influences, should be equipped with EY (electro-graphite) grades which have a high mechanical strength and resistance to oxidation. Grade EY 9106 is completely resistant to super-heated steam temperatures up to 500'C (932'F) and for abnormally oxidising conditions at lower temperatures. For applications concerned with temperatures upto 600`C (1,112'F) grade EY 9106 BY is suitable.

GRADES

Our most commonly used grades for gland rings are CY2 for non-contact gland rings, CY2T for contact gland rings, CY2W and CY2WA for contact gland rings handling toxic gases, and EY9106 for high temperature application.

DESIGN

Type of Joint

As mentioned earlier,gland rings for steam turbines are now made almost invariably as'butt-joined' rings. The ends of the segments are accurately cut on the radial line, so that no clearance exists between segments when the ring is assembled around the shaft

Earlier designs of gland rings are still made however with a small clearance between segments, which therefore bear directly on the shaft, i.e., they form a contact seal rather than a throttle. To avoid leakage through the clearance of the joints, the segments used in these rings can be machined with very accurately fitting lap joints. This type of ring however is only suitable for low pressure sealing and where a certain amount of lubrication is available from the saturated steam.

`Contact' type rings with special joints are occasionally useful for low pressure gas sealing applications, but are more appropriate to fluid sealing applications, and are used extensively for water turbine glands for which segmental rings in diameters of 2032 mm (80 in) and over are frequently manufactured.

Fans and Blowers

As carbon Jamuna carbon gland rings are being used extensively for shaft seals in auxiliary plants such as compressors, fans and blowers. Such gland rings are particularly suitable for plants installed in exhaust systems handling noxio, inflammable or toxic gases and in air refrigeration or gas systems. The self-lubricating properties, high oxidation and chemical resistance of carbon make it an ideal material for a wide range of operating conditions. In these applications carbon gland rings provide an effective seal which has a long life, thus reducing maintenance problems to a minimum.

As carbon/ Jamuna grade CY2 has been found to give excellent results under the conditions most commonly encountered in this field, but other materials are also available for abnormally severe conditions such as those associated with very high temperatures or highly corrosive gases. In such cases reference should be made to our Applications Department to ensure that the most suitable grade of carbon is chosen.

In low pressure machines it is a normal practice to employ a single check ring of the bevelled section type, although for more important glands two rings are often considered a minimum. For sealing higher pressures, or where a leak-off must be provided to prevent toxic gases escaping into the atmosphere, a gland employing several rIngs may be necessary.

The fitting and the design of these glands should follow the recommendation made for steam turbine glands earlier. When sealing corrosive gases, care must be taken to prevent the formation of corroded particles in the gland ring housing, because this will cause abnormal wear to the carbon rings. In such instances suitable corrosion resistance materials should be used for the shaft sleeve and ring housing.

Smilarly, on blowers handling dust laden atmospheres, the ingress of dust particles into the gland will also cause wear of the carbon rings. In exceptional cases of this nature, the gland rings may jam am in their housings. This problem can often be overcome however by a suitable housing design. Our Applications Department will give advice on this.

When pressures of 7.0 kgf/cm2 (100 lbf/in2) and over are to be sealed. it is usual to employ a carbon labyrinth. One or more leak-offs are normally provided to control the pressure drop through the gland. Leak-offs or pressure feed points may also be necessary to collect the leakage of toxic gases or to prevent contamination of the gas being handled.