Compromise between sliding seals: wear and leakage


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The traditional sliding seal applications: pumps, mixers, agitators and centrifuges. In these devices, the sliding seal is often the root cause of the accident. The right choice of suitable seals can reduce such accidents. So how do you choose the right seals? Suppliers to provide users with what solutions?
Process pump, professional and technical seminars, correspondents Flowserve Corporation, Mr. Hans-Wilhelm Laarmann interview, from the perspective of a sliding seal manufacturers to explore the application of sliding seals difficulties: sliding seals except to bear high sealing pressure outside, but also withstand the high temperatures of the sealing medium, sometimes medium or contains solids medium or high viscosity. In addition, there are the geometric dimensions of requirements, for example, with the tight installation space, the size requirements of the screw pump accurate axial spacing, etc.. Laarmann He is also a the four prerequisite for sliding seals efficient work:
Degrees of parallel to the end face of the sliding face;
· Sealing surface and between the axis of rotation of the vertical degree;
· The sealing surface of the resilient contact;
· Lubricant film between the sealing surface.
In the 2007 TU Granz process pumps practical technical seminars the John Crane of Bernhard Borgr for? Ber Mr. final one conducted presentations: good lubricating oil film formed between the sealing surface of the well to reduce the sliding surface contact, reduce friction, but also has a large seal leak problem. In real sliding seals, generally compromise deal with the seal leak sealing surface wear. But this tradeoff can in certain circumstances be broken, Mr. Borngr? BER: "through the liquid with the purpose of the sliding surface design of the the molded structure - LaserFace structure, so that we significantly improve the sliding ring seal lip dynamic lubrication performance, while reducing seal leakage. practical application of many users has confirmed it. "LaserFase structure how to play a role in it? This relates to consider in the design of the sealing surface of the trench.
The oil supply groove in the sealing ring is capable of generating a lot of hydraulic dynamic pressure in the under the action of this pressure in the contact surface for generating a stable, has a strong adhesion of the lubricating film will be separated from the contact surface. Back to the oil sump lubrication after the oil back into the inside of the machine, thus greatly reducing the seals seal leakage. The biggest advantage of this technology is that: in a medium having a "volatile, escape" performance, when used, has a longer life than the the GLRD type ring. The potential of this technology is to greatly increase the service life of the sliding seals.
This technique, however, when in use will be subject to certain limitations: Currently, this technique can only be used in the clean medium sealing, if the medium to be sealed to contain more solid substance, the use of such seals will restricted. Boiling temperature of the liquid medium is sealed -268.15 ~ -270.15 ℃.
Silicon carbide: the appropriate choice of materials
Generally speaking, the material of the sliding seal is usually chosen silicon carbide (SiC). The combination of the materials in contact with each other carbide - carbon or carbide - carbide compared with a combination of materials of silicon carbide - silicon carbide has a better resistance to corrosion performance and the performance of the anti-corrosive medium. Even so, the user of the pump must have a little "spirit of sacrifice" to make some concessions and compromise: in the case of dry friction oil loss in a short time, the poor performance of the silicon carbide material seals; Moreover, this material a sealing member in limited use in the hot medium. In these use cases, ESK ceramic material provides a high quality material called SiC-G (Ekasic-G): a carbon-containing, direct sintered silicon carbide material. Constitute a hard - hard and hard - soft pairing material combinations. Adding carbon particles have the same role in dry friction agent, in the case of oil loss in a short time (no lubrication medium dry run) has good frictional properties - an increase sliding seals to extend the life of the adverse working conditions an important measure. Also reflects the good results in the use of this material in demineralized water. Other silicon carbide materials in demineralized water easily corrode, SiC-G is not susceptible to corrosion.
Shaft sealing solutions
Together with a process equipment production factory, Grundfos R & D as a food production enterprises a Gooled-Top seals. In this product, the sliding seal is an air cooling accessories and pump separated. This separation is to prevent the pump the heat conduction to the sliding seal. Air cooling attachment itself without cooling. Sliding seals by the transmission medium for lubrication, and the lubricating effect of the medium to enter the interior of the seal attachment lubrication channels. Shaft seal in order to maintain no more than 120 ° C maximum operating temperature, medium temperature must not exceed 180 ° C. Due to the mechanical properties and the technical characteristics of the sliding seal can not work at high temperatures for a long period, therefore, the air cooled GLRD seal the shaft is a good sealing solutions.
Corrosive media sealing solution
Strong corrosive media sealing, Garlock provides a good solution. Such a seal is suitable for use in pumps, mixers, and the compressor shaft. Gulliver series of seals are two types of synthetic rubber bellows and the rubber O-ring suitable for use in the chemical industry equipment. The friction surface and the friction surface may be a carbon fiber material, a carbon material containing silicon carbide, tungsten carbide, silicon carbide, alumina, quenched and tempered steel, cast steel or plasma chromia coating.
The traditional sliding seals can not do a certain condition due to the sealing lip, the PS-Seal would be a good solution. This seal is a floating seal member, in the conventional sealing member can not be used due to the deviation of the shaft and, for example, is a good sealing solutions for large deviations of the mixer shaft, dryer shaft and stirrer shaft .
With emery help avoid wear
The EagleBurgmann company R & D and production with emery coating seals. This seal has a very good wear resistance under conditions of mixing of raw materials as well as the dry-run oil loss in the high corrosive media sealing conditions. Emery coating of crystals suitable for seals in the oil and gas industry (for example, the multiphase pump), mud pump field in chemical production enterprises in the field of medicine production enterprises and civil technologies (hot water). Carborundum coating of the thickness of the sliding seal surface up to 8μm has a high hardness, thermal conductivity, and resistance to chemical corrosion and low coefficient of friction. The adhesion properties of the base material is the key to this technology.
Emery coating DiamondFase technology is a microcrystalline coating, by chemical vapor deposition technology coated on the base material. The decisive crystallization under the 2000 ° C high temperature in a vacuum state by the tungsten electrode is applied to the substrate surface. This coating technique in the entire surface of a coating of uniform and detailed - layer thickness of 8μm, and the function of the sliding seal has a pivotal role in the coating. Emery adhesion properties meet the practical requirements known so far.
Service life improved significantly
Burgmann with Shell German limited liability company located in Godorf and Wesseling factory signed a "framework contract" sliding seals after-sales service. Shell German company's annual production capacity of up to 17 million tons, is the largest oil refinery in Germany.
The purpose of this service contract signed is to significantly improve the service life of the sliding seals. To avoid downtime in the future production engineering, to reduce oil production equipment maintenance time, mutual study of seal failure, investigate the reason of the failure to develop improved measures improve and eventually into the SEPRO. SEPRO an enterprise network-based software program developed specifically for the management and evaluation of the service contract implementation. Under this service contract, Burgmann Shell Germany's comprehensive partner. Shell rotating parts and Reliability Engineering Department, Mr. Markus Hampel said: "with the the Burgmann company's contract to bring the many benefits of the Shell company more money we can save costs." In the first month of the commencement of the contract, Both sides start the analysis of potential improvements to improve. The Burgmann company responsible for sales and service center in Germany, Mr. Fred Kirchmayr said: "With the completion of the sales and service center, Shell and Burgmann mutual benefit."



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