WO2015128250A1 - System with a gas seal, and operating method - Google Patents

Abstract

The invention relates to a system (A) with a gas seal (GS), in particular a dry gas seal (DGS), comprising the following: - a support element (CE) on which the gas seal (GS) is secured and supported, - at least one sealing gas feed line (SGL) for supplying sealing gas (SG) to the gas seal (GS), and - at least one heating element (HT), said heating element (HT) being designed and arranged such that the sealing gas (SG) flowing through the sealing gas feed line (SGL) can be directly or indirectly heated by the heating element (HT) before entering the gas seal (GS) and/or the gas seal (GS) can be directly or indirectly heated by the heating element. In order to reduce costs and increase efficiency, the support element (CE) is connected to the heating element (HT) so as to conduct heat such that the gas seal (GS) and/or the sealing gas (SG) flowing in the sealing gas feed line (SGL) is heated by the dispensed thermal energy of the heating element (HT) by means of the heat conduction of the support element (CE). The invention also relates to a method for operating the system.

Description

description

The invention relates to a system with a gas seal, in particular a dry gas seal comprising:

 a carrier element to which the gas seal is attached and supported,

 - At least one sealing gas supply line for supplying sealing gas to the gas seal. In addition, the invention also relates to a method for operating the system.

Gas seals are used as shaft seals and increasingly preferred over simple labyrinth seals, because the leakage is considerably lower.

The gas seals, in particular dry gas seals, depend on a special quality of the sealing gas for safe operation. The sealing gas is to be supplied to the gas seal in a relatively narrow temperature range with only a very low moisture content. Should there be only a slight deviation in the quality of the sealing gas during operation, e.g. To introduce too high a level of moisture, there is a corresponding interruption of the lubricating film of gas between the rotating sealing surface and the standing sealing surface and consequently to damage or destruction of the gas seal. Frequently gas seals or dry gas seals are used in the compression of process fluids, so that the destruction of the gas seal designed as a shaft seal usually has a decommissioning or even destruction of the compressor result. In the case of a toxic or explosive process medium, the destruction of the gas seal in the compression process can have catastrophic consequences.

Because of this, the API 614 (API = here standard of the American Petroleum Institute) and the draft for the API 692 prescribe that the sealing gas - also called barrier gas - must have a temperature with a sufficient distance to the dew point (2OK) over the entire gas seal. Even if the barrier gas flow temperature is sufficient, condensate can precipitate on surfaces which are cold compared to the barrier gas flow and therefore act as condensation nuclei (for example, the surface of the gas seal itself), and thus the dry gas seal can be damaged. Particularly critical are the operating points "pressure-loaded standstill" and "start-up" of a turbo compressor, since no waste heat from ventilation or friction losses heats the metal of the dry gas seal and thus also the critical surfaces.

From WO 2013/083437 Al, the use of a gas seal or dry gas seal is already known. This publication also provides heating for the sealing gas prior to entering the gas seal.

The careful temperature control leads to a significant installation effort for the treatment of the sealing gas in conventional systems of the type mentioned. To the treatment usually also includes a careful heating and temperature control of the sealing gas, depending on the current operating conditions of the plant.

Heretofore, as provided by the API 614 and API 692 design, the barrier gas flow was strongly heated so that a sufficient distance to the dew point could be maintained. A disadvantage of this solution is that it does not take into account the effect of condensation on cold surfaces, but provides sufficient protection against surface condensation only for operating points with sufficient heat input from losses of the turbocompressor. Additionally, for critical operating points, an alternative gas, such as nitrogen, has been used with sufficient distance from the dew point. At this solution is disadvantageous that an external barrier gas source with sufficient external sealing gas must be available.

For example, if the system is in a particularly cold environment, or if currently a particularly cold or hot operating medium is being conveyed, then the temperature control of the sealing gas must take this into account in that the sealing gas must be able to meet the required lubricating effect on the sealing surfaces of the gas seal within the prescribed temperature range ,

A particular disadvantage of the sealing gas treatment is on the one hand in the high installation costs, which causes considerable costs and on the other hand in the significant space requirement, which claims the usually at least component-wise redundant running seal gas treatment for themselves.

Based on the problems and disadvantages of the prior art, the invention has therefore taken on the task, on the one hand to improve the reliability of a gas seal and on the other hand to reduce the space required for the sealing gas treatment. To solve the invention proposes a system of the type mentioned above with the additional features of the characterizing part of claim 1 and a method according to the dependent method claim for the operation of the claimed system. The respective dependent claims contain advantageous developments of the invention. The invention is also attributable to embodiments that are not explicitly defined by means of the claim references, however, the expert from a combination of the other claimed features and the features of the embodiments make sense.

The invention overcomes several disadvantages of the prior art. So far, the influence of higher temperature of the barrier gas on the surface temperature of the gas seal is only low, since the transfer surface and the proportion of the sealing gas, which flows over the surface, is small. Therefore, conventionally, there is a high required power of the purge gas heater because much of the introduced heat remains unused.

By a construction according to the invention can advantageously be a failure of liquids on the gas seal and in particular the associated surface by condensation of the sealing gas, which possibly leads to a failure of the dry gas seal, are excluded.

It is likewise advantageous that it is possible to dispense with an external sealing gas which, as stated above, was previously required for critical operating points such as start-up and standstill under pressure to prevent liquid failure. A further advantage is that the required energy input can be reduced to the required by the API barrier gas heater, since according to the invention one - possibly further - heat source is closer to the critical location, which due to the arrangement a much better efficiency relative to the heating of the Has gas sealing surface.

Furthermore, it is advantageous that only by cylindrical recesses or simple holes in the support element of the gas seal - for example, a housing cover - by means of introduced into the holes electric heating cartridges, the required thermal energy can be supplied.

A further advantage is that the mentioned holes do not have to protrude into the pressure chamber, so that no special sealing of this heating chamber is necessary. It is also advantageous that the achievable temperature is limited only by the design temperature of the carrier component, for example the temperature capacity of the housing cover. Compared to a heating by means of oil can be advantageously dispensed with an extension of the oil system for heating purposes by means of a construction according to the invention, wherein the same function is provided electrically with much less effort. The electrical version is also more flexible to control and independent of the oil system regulated.

Furthermore, it is advantageous that, compared to the conventional solutions in the construction according to the invention results in a lower transmission path for the heat conduction. Thus, the losses are reduced significantly.

It is also advantageous that by using a control, the heat input can be adjusted depending on an operating point to the thermodynamic need. The heating of the gas seal carrier may possibly be switched off in normal operation if the self-heating from the heat loss occurring in the seal or the heat of a turbomachine connected in operation is sufficient to heat the gas seal.

Particularly flexible is an electrically formed heating element. This can be advantageously used in elongated recess of the support element. In this case, it is particularly expedient for the carrier element (CE) to have an additional heat conductor-in particular thermal compound-wherein the additional heat conductor can be adapted to the shape of the heating element, so that an enlarged surface of direct contact between the carrier element and the additional element Heat conductor and the heating element is formed, so that compared to an arrangement without the additional heat conductor of a ne improved heat conduction from the heating element to the support element is formed.

The support element is expediently designed with a supply channel for the sealing gas.

A preferred application of the invention is a design of the system as a fluid energy machine, in particular as a turbo compressor. Advantageously, the carrier element may be part of a housing of the turbomachine, for example as a housing cover of the housing of the fluid energy machine, in which case the housing cover may also be the carrier of the gas seal attached to the housing cover and carrier of a shaft bearing attached to the housing cover.

According to the invention, the at least one heating element transfers heat energy to the carrier element, wherein the carrier element transmits heat energy absorbed by the heating element to the gas seal. In this case, it may be advantageous for the carrier element to transfer part of the heat energy absorbed by the heating element to the gas seal and another part to the supply channel for the sealing gas.

The invention is explained in more detail below with reference to specific exemplary embodiments with reference to FIGS. The

Embodiments are to be understood as exemplary only and do not limit the invention exclusively to the illustration. On the contrary, within the scope of his specialist knowledge, it is possible for a person skilled in the art to combine individual mentioned features with others without departing from the scope of the invention. Show it:

FIG. 1 shows an end view of a schematic representation of a housing cover with electrical heating cartridges inserted in bores,

Figure 2: a longitudinal section of an embodiment with parallel to a compressor shaft introduced heating cartridge. Figure 3: a longitudinal section of an embodiment with introduced perpendicular to the compressor shaft heating cartridge.

 FIG. 4 shows a longitudinal section of an exemplary embodiment with a heating cartridge introduced at an angle to the compressor shaft.

The figures each show schematically relevant components of a system according to the invention A. There are, inter alia, a gas seal GS, in particular a dry gas seal DGS, a support member CE, on which the gas seal GS is attached and supported, and at least one heating element HT shown. As shown schematically in FIGS. 1-4 each, a gas seal insert GSC comprising a gas seal GS or dry gas seal DGS and a certain number of heaters HT is received by the support element CE formed as a housing cover CCV.

In addition, a shaft bearing BEA is provided on the carrier element CE or the housing cover CCV, by means of which a shaft SH extending along an axis of rotation X is mounted. The shaft SH is sealed to the otherwise stationary components by means of the gas seal GS, so that no process fluid PF in the interior of a fluid power machine passes through the gap into the environment through a gap extending in the circumferential direction between the gas seal GS and the shaft SH can escape. The fluid energy machine of plant A is preferably designed as a turbocompressor TC and has a substantially hermetically sealed housing CAS, which is sealed to the environment by means of the housing cover CCV, which is designed as a carrier element CE. The housing cover CCV takes as a carrier of the shaft bearing BEA on the static and dynamic bearing forces of the shaft SH and the corresponding rotor. The gas seal GS is supplied by means of a sealing gas supply via a sealing gas line SGL by means of sealing gas or sealing gas. The sealing gas SG is contaminated by means of a derivation, not shown, from the gas seal GS contaminated by passed into the extracted sealing gas SG process gas and ambient air along an exhaust, not shown. The sealing gas line GSL has a sealing gas filter SFL and holds the sealing gas SG from a higher pressure level, which is shown in FIG. 1 as a sealing gas compressor SCO. Alternatively, the higher pressure level may also be a reservoir of sealing gas SG. Particularly preferred is an embodiment of the invention in non-environmentally harmful process fluids PF such that the sealing gas SG is simultaneously the process fluid PF and the sealing gas SG is taken from the highest pressure level of the fluid energy machine for supplying the gas seal GS.

In the exemplary embodiment of FIG. 1, the heating elements HT positioned by the carrier element CE are located on a circle RAD over the circumference - in this case distributed at equal intervals concentrically with the axis of rotation X. This equidistant arrangement is only exemplary and not mandatory.

As also shown in FIGS. 2-3, the respective heating element HT is arranged along a longitudinal axis XHT1, XHT2, XHT3 in a cylindrical recess CH in the carrier element CE. In the various embodiments, the longitudinal axis XHT1, XHT2, XHT3 is oriented in each case in a different angular position to the axis of rotation X of the system A. In principle, it is possible that the heating element HT extends with the longitudinal axis XHT1 - XHT3 in any angular orientation to the axis of rotation X or a housing longitudinal axis of the housing CAS. The final number of heating elements HT or of the corresponding heating element recesses CH and their orientation in the carrier element CE can be determined. Optionally, the heating elements HT in the recesses CH with interposition of a deformable additional Wäremleiters AHC - here thermal paste - the carrier element CE arranged.

Task of a constructive optimization with the aim to operate in each operating state by means of the heating elements HT, the gas seal GS in the allowable temperature range. For this purpose, it is also useful if the heating element HT transmits by means of the support member CE not only on the gas seal GS heat, but also on the sealing gas supply CGL, which extends partially through the support member CE to the gas seal GS out. In this way, the heating element HT or the heating elements HT indirectly heats both the gas seal GS and the supply of sealing gas SGL and indirectly also the sealing gas SG, so that the gas seal GS is always operated in the allowable temperature range.

FIG. 2 shows an embodiment in which the heating element HT is inserted parallel to the compressor shaft SH in a bore introduced in the housing cover COV and thus indirectly heats the (in simplified form) gas-tight housing including the dry gas seal DGS contained therein.

In the embodiment of Figure 3, the heating element HT is used perpendicular to the compressor shaft in a housing cover COV introduced hole and thus indirectly heated (simplified) gas seal housing including the dry gas seal contained therein.

The heating elements HT are powered by a power source PSU using power lines PSL with electrical

Power supplied to generate the heat energy. A temperature measuring point TS transmits the current temperature to a central control CU, which regulates the power supply from the power source PSU to the heating elements HT. For the purposes of regulation, the central control unit CU accesses a database PDA, so that it is ensured in all operating states that, based on empirical values stored in the database, the correct amount of energy is always fed into the heating system. HT is converted to heat. The control CU is connected to the central database PDA and the power source PSU and the temperature measuring point CS by means of signal lines SL in connection.

In a third exemplary embodiment (see FIG. 4), the heating cartridge 3 is inserted obliquely to the compressor shaft in a bore 11 introduced in the housing cover CCV and thus indirectly heats the (in simplified form) gas-tight housing including the dry gas seal 2 contained therein.

Furthermore, this design takes into account the geometry of the gas-tight seal housing and is nevertheless attached as close as possible to the gas seal insert GSC including the dry gas seal 2 contained therein.

Claims

claims Plant (A) with a gas seal (GS), in particular a dry gas seal (DGS), comprising:  a carrier element (CE) to which the gas seal (GS) is attached and supported,  at least one sealing gas supply line (SGL) for the supply of sealing gas (SG) to the gas seal (GS),  - At least one heating element (HT), wherein the heating element (HT) is designed and arranged such that by means of the heating element (HT) through the sealing gas supply line (SGL) flowing sealing gas (SG), before entering the gas seal (GS) and / or the gas seal (GS) is / are directly or indirectly heatable,  characterized in that  the carrier element (CE) is thermally conductively connected to the heating element (HT), so that the gas seal (GS) and / or the sealing gas (SG) flowing in the sealing gas supply line (SGL) depends on the heat energy of the heating element (HT) emitted by the heat conduction of the heating element Carrier element (CE) is heated. Plant (A) according to claim 1,  wherein the heating element (HT) is an electrical heating element (HT). Plant (A) according to claim 1 or 2,  wherein the heating element (HT) is elongate and the support member has an elongated recess (CH), in which the heating element (HT) is arranged. Plant (A) according to at least one of the preceding claims 1 to 3, wherein the carrier element (CE) has an additional heat conductor (AHC), which is adaptable to the shape of the heating element (HT), so that an enlarged area direct contact between the support element (CE) and the heating element (HT) is formed, so that compared to an arrangement without the additional heat conductor (AHC) improved heat conduction from the heating element (HT) on the support element (CE) is formed. Plant (A) according to at least one of the preceding claims 1 to 4, wherein the sealing gas supply line (SGL) is partially provided in the carrier element so that a supply channel is provided in the carrier element for the sealing gas (SG). Plant (A) according to at least one of the preceding claims 1 to 5, wherein the system (A) is designed as a fluid energy machine (FEM), in particular as a turbocompressor (TC). Plant (A) according to claim 6, wherein the carrier element (CE) is part of a housing (CAS) of the turbomachine (FEM). Plant (A) according to claim 7, wherein the carrier element (CE) is designed as a housing cover (CCV) of the housing (CAS). Plant (A) according to claim 7, wherein the cover (COV) is the carrier of the gasket (GS) attached to the housing cover (CCV) and carrier of a shaft bearing (BEA) attached to the housing cover (CCV). Method for operating an installation (A) according to one of claims 1 - 9, wherein the at least one heating element (HT) transfers thermal energy to the carrier element (CE), wherein the carrier element (CE) of the heating element (HT) absorbed heat energy transmits at least a portion of War meenergie to the gas seal (GS). Method according to claim 10 and at least also 5, wherein the carrier element (CE) transfers heat energy absorbed by the heating element (HT) partly to the gas seal (GS) and another part to the supply channel (SGL) for the sealing gas (SG).