Patent Description:
The present invention relates to a pump unit comprising an assembly for attenuation of vibration of the pump unit coupled to a pipework according to the preamble of the claim <NUM>.

The present invention relates also to a pump unit.

Invention relates to vibration problems in a pipework aggregate to which a pump unit is attached to pump the fluid in the pipework.

A pump is usually installed in a bed or a support frame typically made of metal bars. The support frame is resiliently attached to a foundation. The foundation may be for example a concrete floor or a separate framework made of metal bars.

<CIT> discloses a centrifugal pump support which comprises a mounting frame to a support fame is resiliently attached by making us of compression springs.

It has been found out that even if such a pump unit and the support frame would be aqeuately supported to the mounting frame, coupling it with the pipework changes the vibration properties of the whole system considerably and the support of the mounting frame can not adequately cope with the whole system comprsing the pipework aggregate, which includes the pump unit. Structural dynamics of such pipework aggregate changes from the standstill situation to operational situation and structual dynamics of the pipework aggregate is difficult to define exactly beforehand. On the otherhand, the circustances during a steady state operation of the pipework aggregate are diffent and therefore the support which may be optimal for start-up stage may be unadequate in steady state operation.

An object of the invention is to provide a method of operating a pipework aggregate and an assembly for attenuation of vibration of a pump unit in which the performance is considerably improved compared to the prior art solutions.

It is also an object of the invention is to provide a pump unit utilizing the method and/or the assembly.

Objects of the invention can be met substantially as is disclosed in the independent claims and in the other claims describing more details of different embodiments of the invention.

According to an embodiment of the method of operating a pipework aggregate, comprising a pipework for transporting process fluid, fluid processing devices and at least one pump unit, comprising a centrifugal pump and a motor assembled on a base plate, the pump unit being coupled to the pipework, which pump unit is supported resiliently on a foundation using a resilient support, which resilient support is resilient in several directions, comprises steps of.

This way operation of the pump unit advantageous during both the transient state operation, such as start-up, and during steady state operation. During the start-up stage vibration behaviour and/or thermal expansions of the pipework aggregate and its effects on the pump unit is advantageously taken care by the resilient support, while during the steady state the stiffness and/or damping of support of the pump unit on the foundation is increased so as to minimize the harmful effects of any vibration resonances.

According to an embodiment of the invention the method further comprises.

Resilient support is arranged for coping with temperature increase while the temperature is lower than the target temperature. During normal operation the resilient support is prone to allow inducement of vibrations and when the measured temperature is equal to or higher than the target operational temperature, the pipework aggregate is in a steady state operation and stiffness and/or damping of support of the pump unit on the foundation is increased.

According to an embodiment of the invention the method further comprises during a start-up of the pipework aggregate.

According to an embodiment of the invention during the steady state operation, vibration of the pump unit is analysed, and if direction of vibration, which has vibration amplitude greater than a pre-set limit value of the amplitude, is detected, stiffness and/or damping of the base plate of the pump unit is increased in at least the determined direction of vibration.

According to an embodiment of the invention stiffness and/or damping of support of the base plate of the pump unit on the foundation is increased by arranging a mechanical retainer means to selectably suppress relative movement between the base plate and the foundation in the determined direction of vibration.

According to an embodiment of the invention during the steady state operation, stiffness and/or damping of the support of the base plate of the pump unit is adjust-ably increased in a plane of the base plate.

According to an embodiment of the invention in a next transient state operation after a steady state operation, stiffness and/or damping of support of the base plate of the pump unit on the foundation is restored to the state prevailing in the transient state.

An assembly for attenuation of vibration of a pump unit coupled to a pipework, the pump unit comprising a centrifugal pump and a motor assembled on a base plate, the pump unit being supported resiliently on a foundation using a resilient support, which resilient support is resilient several directions. The assembly comprises a retainer means configured movable between a first position suppressing relative movement between the foundation and the base plate for increasing stiffness and/or damping and/or damping of support of the base plate of the pump unit on the foundation, a second position being neutral in influencing to relative movement between the foundation and the base plate.

According to an embodiment of the invention the base plate is supported on the foundation by several vertical legs wherein the resilient support is arranged between the leg and the base plate, and the retainer means are arranged to selectably supress relative movement between the leg and the base plate in the plane of the base plate.

According to an embodiment of the invention the retainer means are provided with a body part, and pusher part adjustably attached to the body part, wherein the relative movement between the leg and the base plate is suppressible by bringing the pusher part against either one of the base plate or the leg while the body part being attached to either one of the base plate or the leg.

According to an embodiment of the invention body part is attached to the base plate and the pusher part is configured to adjustably push against the leg.

According to an embodiment of the invention that the pusher part comprises a screw bar and the body part comprises a threaded hole to which the screw bar is attached, and that the pusher part is provided with a resilient head at an end of the screw bar.

According to an embodiment of the invention the resilient support are compression springs.

According to an embodiment of the invention the retainer means are arranged as pairs in which the retainer means in each pair effect in opposite directions to each other.

A pump unit comprising an assembly for attenuation of vibration according to the invention.

In this context the term base plate means a generally planar structure on which a centrifugal pump and its motor are assembled. The base plate may be a framework which is constructed of multiple beams arranged to form the planar structure.

The exemplary embodiments of the invention presented in this patent application are not to be interpreted to pose limitations to scope of the invention which is defined by the appended claims. The verb "to comprise" is used in this patent application as an open limitation that does not exclude the existence of also unrecited features.

<FIG> depicts schematically a pump unit <NUM> which is coupled to a pipework, forming a pipework aggregate <NUM>. The pump unit <NUM> comprises a pump <NUM>, which is here a centrifugal pump, a motor <NUM>, and a shaft coupling <NUM> connecting the pump <NUM> and the motor <NUM>. The pump unit further comprises a base plate <NUM>, which is resiliently supported on a foundation <NUM>. The pipework aggregate <NUM> may be a substantially complicated network of piping which is illustrated here by the block <NUM>. The piping comprises straight pipes and angled part connecting the straight part as well as various appliances (valves, data collectors, mixers, etc) and processing devices <NUM>' for processing the fluid in the pipework aggregate <NUM>. The pipework aggregate may be for example a part of a pulp mill, water supply system, power plant or alike.

Structural dynamics of such a pipework changes from the standstill situation to operational situation. In order to cope with temperature expansion resulted in the pipework aggregate the pump unit comprises a resilient support <NUM> in the base plate <NUM>, such that the pump unit <NUM> is supported resiliently on the foundation <NUM>. The resilient support <NUM> is resilient several directions. The resilient support may comprise one of, or a combination of a spring, resilient block, such as a rubber block, vibration damper, such as viscose damper, or alike. Advantageously the resilient support is a compression spring <NUM>. The resilient support has a main compression direction which is bearing the load caused by the mass of the pump unit <NUM>. The main compression direction is therefore substantially vertical direction transverse to the plane or the base plate <NUM>.

Even if a pump unit <NUM> and its resilient support is adequately designed in a view of possible vibration over the conceivable operational range (range of volume flow, pressure range, range of rotational speed) of the pump unit <NUM>, coupling the pump unit <NUM> with the pipework aggregate <NUM> may change the vibrational characteristics and demands considerably. Structual dynamics of the pipework aggregate is difficult to define exactly beforehand. The pump <NUM> is connected to the pipework aggregate without any bellows, that is using simple flange joint <NUM> directly to respective feed pipe <NUM> and return pipe <NUM>. Such a flange joint may be considered as a rigid coupling. At least the flange joint <NUM>. is considerably stiffer than the resilient support <NUM>.

Now turning to <FIG> the features and operation of the invention are explained in more detailed manner. <FIG> shows a side view of a pump unit <NUM> according to an embodiment of the invention. There are sectional views IV-IV and VI-VI marked in the <FIG> which are shown in the <FIG> and <FIG>, respectively. <FIG> shows a left-side end view of the <FIG>. There is a sectional view V-V marked in the <FIG> which is in turn shown in the <FIG>.

The pump unit <NUM> comprises an assembly <NUM> for attenuation of vibration of a pump unit to selectably effect on the resilient support <NUM> in the base plate <NUM> and vibration characteristics of the pump unit <NUM>. The assembly <NUM> comprises adjustable retainer means <NUM> for increasing stiffness and/or damping of support of the base plate of the pump unit on the foundation. The retainer means <NUM> can be selectably activated for effecting on the stiffness and/or damping of support of the base plate and deactivated. In addition to mere on-off action of being activate or passive, the stiffness is adjustable by adjusting the force by which the retainer means <NUM> effects.

In the <FIG> there is shown an enlarged view A in the <FIG>, which shows one of the resilient supports <NUM> in connection with which two retainer means <NUM> are arranged. Each one of the retainer means <NUM>, which are referred also as stoppers, effects in one direction in the plane of the base plate <NUM>. And, as it can be seen for example in the <FIG> there is a first pair of retainer means <NUM>'-<NUM>" which effect in opposite directions to each other, in longitudinal direction of the pump unit, and a second pair of retainer means <NUM>' - <NUM>" which effect in opposite directions to each other, perpendicularly to the longitudinal direction of the pump unit. In other words, according to the invention the retainer means <NUM> are arranged as pairs in which the retainer means <NUM>'-<NUM>" effect in opposite directions to each other.

The longitudinal direction of the pump unit is parallel to the shaft of the pump and the motor. The first pair and the second pair of retainer means are arranged at a first end of the pump unit. There is a third pair of retainer means <NUM>'-<NUM>" which effect in opposite directions to each other, in longitudinal direction of the pump unit, and a fourth pair of retainer means <NUM>' - <NUM>" which effect in opposite directions to each other, perpendicularly to the longitudinal direction of the pump unit. The third pair and the fourth pair of retainer means are arranged at a second end of the pump unit <NUM>. The direction in the which the retainer means effect is transverse to the compression direction of the resilient support.

Should the direction of the problematic vibration i.e. selected direction, be different than the longitudinal direction of the pump unit <NUM>, the first pair of retainer means <NUM>'-<NUM>" is arranged to effect in the direction of the selected direction, and a second pair of retainer means <NUM>' - <NUM>" is arranged to effect in the direction perpendicularly to the selected direction.

As it becomes clear particularly from the <FIG> the base plate <NUM> is supported on the foundation <NUM> by several vertical legs <NUM> wherein the resilient support <NUM> is arranged between the leg <NUM> and the base plate <NUM>. As is shown in the <FIG> the retainer means <NUM> are arranged to selectably suppress relative movement between the leg <NUM> and the base plate <NUM> in the plane of the base plate <NUM>. Since the leg is attached to the foundation <NUM> the movement of base plate <NUM> is suppressed considerably.

The retainer means <NUM> are provided with a body part <NUM>, and a pusher part <NUM> adjustably attached to the body part <NUM>, wherein the relative movement between the leg <NUM> and the base plate <NUM> is suppressible by bringing the pusher part <NUM> against either one of the base plate <NUM> or the leg <NUM> while the body part <NUM> being attached to either one of the base plate <NUM> or the leg <NUM>. In other words, while the body part is attached to one of the base plate <NUM> or the leg <NUM>, the pusher part <NUM> is brought against the other one of the base plate <NUM> or the leg <NUM>. In the embodiment shown in the figures, the body part <NUM> of the retainer means <NUM> is attached by screws to the base plate <NUM> and the pusher part <NUM> is brought against a surface of the leg <NUM>. The pusher part is configured to adjustably push against the leg. More precisely the pusher part is configured to be selectably activated, by bring it against the leg <NUM>, and deactivated by detaching the pusher part <NUM> from the leg <NUM>, and when activated the pressing force of the pusher part is adjustable. The pusher part <NUM> comprises a screw bar and the body part comprises a threaded hole <NUM> to which the screw bar is attached so as to provide adjustable longitudinal movement of the screw bar by rotation thereof. The pusher part <NUM> is provided with a resilient head <NUM> at an end of the screw bar <NUM>. The surface in the leg, against which the pushed part <NUM> is pushing can be provided with an optional, additional counter part <NUM>, by means of the characteristics of the support can be further controlled. The counter part <NUM> may be for a resilient block or a plate. The counter part <NUM> may be arranged in connection with one or more, or all of the pusher parts <NUM>.

The assembly is advantageously used for practising a method of operating a pipework aggregate <NUM> for transporting process fluid which comprises fluid processing devices <NUM>' and at least one pump unit <NUM>. When the process fluid flow in the pipework aggregate is in a transient state operation, such as a start-up of the pipework aggregate, stiffness and/or damping of support of the pump unit <NUM> on the foundation is ruled by the resilient support solely. During the transient state vibration properties of the pipework aggregate change due to change of the fluid characteristics and the pipework aggregate, caused by the fluid processing devices. Resilient support is advantageous in this stage because during the start-up the change, or raise, of the temperature of the process fluid and/or the pipework aggregate <NUM> can be compensated, if not totally but still very effectively.

This state of operation is shown in the <FIG>. As it can be seen the retainer means <NUM> are now adjusted to a position where the pusher parts <NUM> are detached from the leg, that is, not effecting on the vibration characteristics.

During the start-up process the motor <NUM> of the pump unit <NUM> is started to run the pump and the fluid in the pipework aggregate <NUM> starts the transportation of the fluid in a transient state operation, during which vibration properties of the pipework aggregate may change due to change of the fluid characteristics and the pipework aggregate, caused by the fluid processing devices. In other words, during transient state operation of the process fluid flow in the pipework aggregate vibration properties of the pipework aggregate change due to change of the fluid characteristics.

After the start up, when the pipework aggregate and the process fluid flow have reached their operational temperature and being in a steady state operation, stiffness and/or damping of support of the base plate of the pump unit on the foundation is increased, such that stiffness and/or damping of support of the pump unit <NUM> on the foundation is ruled in addition to the resilient support, by means of the pusher part <NUM>, as is depicted in the <FIG>. By means of the retainer means <NUM> it is possible to minimize excessive vibration of the pump unit <NUM> induced by excitations from the pipework. It can be said that the resilient support results in advanced operation during the start-up stage compensating heat expansion of the pipework aggregate, while during the steady state operation, when the operational temperature has been reached, increased stiffness and/or damping is brought by the pusher part minimizing excessive vibration of the pump unit <NUM>.

Preferably in a next shut down of the pipework aggregate transient state operation is commenced after steady state operation and stiffness and/or damping of support of the base plate of the pump unit on the foundation is restored to the state of <FIG> prevailing in the transient state.

The method may include a step of setting a target operational temperature to the process fluid and/or the pipework aggregate, and acquiring a measured temperature of the process fluid and/or the pipework aggregate, and in case the measured temperature is lower than the target operational temperature the pipework aggregate is in a transient state operation, and in case the measured temperature is equal to or higher than the target operational temperature, the pipework aggregate is in a steady state operation.

Generally, as is depicted in the <FIG>, when the process fluid flow is in a steady state operation stiffness and/or damping of support of the pump unit on the foundation is increased such that the pusher parts <NUM> are attached to, or adjusted to, be against a side wall of the leg. In the next transient state operation stiffness and/or damping of support of the base plate of the pump unit on the foundation is restored to the state prevailing in the transient state.

<FIG> discloses a view of a pump unit <NUM> from beneath the pump unit <NUM> according to an embodiment of the invention. The pump unit <NUM> comprises an alternative assembly <NUM> for attenuation of vibration of a pump unit to selectably effect on the resilient support <NUM> in the base plate <NUM> and vibration characteristics of the pump unit <NUM>. The assembly <NUM> comprises four retainer means <NUM> for increasing stiffness and/or damping of support of the base plate of the pump unit on the foundation acting in opposite and transverse direction.

Each one of the retainer means <NUM> effects in one direction in the plane of the base plate <NUM>. The assembly comprises a pole <NUM> which is attached to the foundation <NUM> similarly to the legs <NUM> of the pump unit <NUM>. In practise the surface at the end of the pole <NUM> in the <FIG> is attached to the foundation. The pole extends upwardly from the foundation into the plane of the base plate <NUM> between its structural beams.

The retainer means <NUM> are provided with a body part <NUM>, and a pusher part <NUM> adjustably attached to the body part <NUM>, and the relative movement between the pole <NUM> and the base plate <NUM> is suppressible by bringing the pusher part <NUM> against either one of the base plate <NUM> or the pole <NUM> while the body part <NUM> being attached to either one of the base plate <NUM> or pole <NUM>. In other words, while the body part <NUM> is attached to one of the base plate <NUM> or the pole <NUM>, the pusher part <NUM> is brought against the other one of the base plate <NUM> or the pole <NUM>. In the embodiment shown in the <FIG> the body part <NUM> of the retainer means <NUM> is attached by welding to the base plate <NUM> and the pusher part <NUM> is brought against a surface of the pole <NUM>. The pusher part is configured to adjustably push against the leg. The pusher part <NUM> comprises a screw bar and the body part comprises a threaded hole <NUM> to which the screw bar is attached so as to provide adjustable longitudinal movement of the screw bar by rotation thereof.

The assembly is advantageously used for practising a method of operating a pipework aggregate <NUM> for transporting process fluid which comprises fluid processing devices <NUM>' and at least one pump unit <NUM>. When the process fluid flow in the pipework aggregate is in a transient state operation, such as a start-up of the pipework aggregate, stiffness and/or damping of support of the pump unit <NUM> on the foundation is ruled by the resilient support solely. Resilient support is advantageous in this stage because during the start-up the change, or raise, of the temperature of the process fluid and/or the pipework aggregate <NUM> can be compensated, if not totally but still very effectively.

<FIG> discloses a view of a pump unit <NUM> from beneath according to another embodiment of the invention. View 10a shows an enlarged view of the detail a in the figure and the view 10b shows an enlarged view of the detail a seen from direction under the base plate <NUM>. The pump unit <NUM> comprises an alternative assembly <NUM> for attenuation of vibration of a pump unit to selectably effect on the resilient support <NUM> in the base plate <NUM> and vibration characteristics of the pump unit <NUM>. The assembly <NUM> comprises four retainer means <NUM> for increasing stiffness and/or damping of support of the base plate of the pump unit on the foundation.

The retainer means <NUM> according to the embodiment of <FIG> comprise a support block <NUM>, a wedge part <NUM> and body part <NUM> as the main components of the retainer means <NUM>. The support block <NUM> is attached to the lower surface of the base plate <NUM> adjacent to the leg <NUM>. The support block <NUM> has a planar wall <NUM> facing towards the leg <NUM>. The body part <NUM> comprises a slanted side wall <NUM> which is facing towards the planar wall <NUM>. The wedge part <NUM> is arranged between the body part <NUM> and the support block <NUM>. The wedge part <NUM> has also a slanted wall <NUM> which is arranged against the slanted wall <NUM> of the body part. The retainer means <NUM> shown in the <FIG> can be activated by moving the wedge part <NUM> sideways in respect to the planar wall <NUM> of the support block <NUM>. The body part <NUM> is provided with a pusher screw <NUM> by means of which the position of the wedge part <NUM> can be changed. Movement of the wedge part <NUM> tightens the wedge-shaped space between the support block <NUM> and the body part <NUM>, and this way effects on the stiffness and/or damping of support of the base plate <NUM>. Depending on the nature of contact between the planar wall <NUM> of the support block and the wall of the wedge part <NUM> facing the planar wall <NUM> effect of the retainer means <NUM> can be altered. The contact may be arranged as a gliding contact by arranging a suitable glide part to either one, or both of the surface. When the contact is a gliding contact the support is practically increasing stiffness only in the direction of normal of the surface between the planar wall <NUM> of the support block and the wall of the wedge part <NUM> facing the planar wall <NUM>. Without a gliding part the friction between the parts results in increasing stiffness is all directions. Instead of a separate glide part the surfaces may be arranged to have a desired co-efficient of friction.

<FIG> discloses a view of a pump unit <NUM> from beneath the pump unit <NUM> according to another embodiment of the invention. The pump unit <NUM> comprises an alternative assembly <NUM> for attenuation of vibration of a pump unit to selectably effect on the resilient support <NUM> in the base plate <NUM> and vibration characteristics of the pump unit <NUM>. The assembly <NUM> comprises four retainer means <NUM> for increasing stiffness and/or damping of support of the base plate of the pump unit on the foundation.

The retainer means <NUM> comprise a bar retainer <NUM>. The bar retainer is a straight bar which arranged to extend between two legs <NUM> supporting the base plate <NUM> such that the resilient support <NUM> is arranged between the leg <NUM> and the base plate <NUM>. The ends <NUM> of the bar retainer <NUM> may comprise adjusting screws by means of which the length of the bar retainer <NUM> can be adjusted. The bar retainer is attached to the base plate <NUM> and its ends <NUM> are arranged selectably to be against the legs <NUM>, when the retainer means is activated, or detached from the legs, when the retainer means <NUM> is deactivated. There is a retainer bars arranged between each leg <NUM> such that the relative movement between the leg <NUM> and the base plate <NUM> is suppressible is two directions perpendicular to each other. The retainer bars <NUM> are arranged under the base plate <NUM>.

The embodiment shown in the <FIG> can be further developed so that its activation and deactivation is accomplished by thermal expansion. Since the need of stiffness and/or damping of support of the pump unit <NUM> is advantageously dependent on the temperature of the process fluid in the pipework aggregate, it is possible to activate, or more generally control the effect of the bar retainer <NUM> by controlling its temperature in response to the temperature of the process fluid. In other words, the bar retainer <NUM> is configured to be in contact with the legs <NUM> when the temperature of the process fluid is at normal operational level and detached from the legs at lower temperature than the normal operational temperature. The bar retainer means is advantageously arranged in heat transfer communication with the process fluid so as to control its heat expansion operation.

It is conceivable to practise the method such that that vibration of the pump unit <NUM> is analysed during the steady state operation, and if direction of vibration, which has vibration amplitude greater than a pre-set limit value of the amplitude, is detected, stiffness and/or damping of the base plate of the pump unit is increased in at least the determined direction of vibration. This means that directions at which the retainer means effect may vary as a result of the analysis.

It is also conceivable to further develop the invention such that vibration of the pump unit is analysed during the transient state operation and if at least one direction of vibration, which has vibration amplitude greater than a pre-set limit value of the amplitude, is determined, stiffness and/or damping of the base plate of the pump unit is increased in at least the determined direction of vibration. Thus, the stiffness and/or damping of support of the base plate of the pump unit on the foundation is increased by arranging a mechanical retainer means to suppress relative movement between the base plate and the foundation in the determined direction of vibration. Change of the fluid characteristics is change of temperature and operation is steady state operation when the temperature has reached a predetermined temperature level.

Claim 1:
A method of operating a pipework aggregate (<NUM>) comprising a pipework for transporting process fluid, fluid processing devices (<NUM>') and at least one pump unit (<NUM>), comprising a centrifugal pump (<NUM>) and a motor (<NUM>) assembled on a base plate (<NUM>), the pump unit (<NUM>) being coupled to the pipework, which pump unit (<NUM>) is supported resiliently on a foundation using a resilient support (<NUM>), which resilient support (<NUM>) is resilient in several directions, characterized by
- when the process fluid flow in the pipework aggregate (<NUM>) is in a transient state operation, during which vibration properties of the pipework aggregate (<NUM>) change due to change of the fluid characteristics, stiffness and/or damping of support of the pump unit (<NUM>) on the foundation (<NUM>) is ruled by the resilient support (<NUM>), and
- when the process fluid flow is in a steady state operation stiffness and/or damping of support of the pump unit (<NUM>) on the foundation (<NUM>) is increased.