Patent Description:
Pipe systems are used in industrial environments, for example food industry or oil industry, for transporting contents like raw materials, half products or end products to various stages in corresponding processes. Such pipe systems need periodic cleaning and therefore the pipe system contents, i.e. the product need to be cleared from the pipe system. After clearing the pipe system, cleaning can be performed. Such cleaning is in the art also referred to as 'Cleaning In Place' (CIP).

While clearing the pipe system, the cleared contents are preferably preserved for later use or recycling in the process in which the pipe system is used. For this reason is it advantageous to clear the pipe before cleaning by pushing out the pipe system contents using a air. Usually compressed air is used, but dependent on the contents, other gasses may be applicable.

In the art it is known that clearing a pipe system can be performed by blowing out the pipe system contents in a push phase, wherein high pressure air is applied at a pipe system proximal end such that the pipe contents are set in motion. When most of the contents are cleared from the pipe system, a constant air flow in a blow phase will remove the remaining contents which adhered to the pipe system walls, after which the pipe system can be rinsed and dried in respective rinse and dry phases.

Clearing the pipe system in the push phase requires adequate pressure and speed. When the pressure is too low, the air used for expelling the contents tends to flow over the pipe system contents and find its way to an distal end. Thereby contents are left inside the pipe system.

When the pressure is too high, the air can push through the pipe contents, creating so called 'rat holes' i.e. passages through the contents.

Adequate initial pressure and pressure profile in time of the compressed air in the push phase can determined from contents viscosity, pipe diameter and architecture, and can also be determined from experience. The air pressure profile in time and consequential flow, once the air is released in the push phase, also determines adequate expelling of the pipe system contents.

Document <CIT> describes a method of clearing a pipe that comprises forcing a gas flow through the pipe, the pipe having a pipe volume, an inlet end and an outlet end, wherein the gas flow is forced into the pipe at the inlet end by applying a gas pressure decreasing from an initial pressure to a lower final pressure that is maintained at the lower final pressure until the pipe is cleared and apparatus for clearing pipes by forcing a gas flow through a pipe having an inlet end and an outlet end, comprising gas flow generating means and a container having an inlet and having an outlet connectable to the inlet end of the pipe.

Document <CIT> describes the method that involves pressurizing gas or gas mixture in a line with a high pressure by modulating pressure impulses such that mini water blocks are formed in the line. The blocks are driven with a high speed through the line. A pressurized gas supply is directly readjusted with the same or high pressure after temporary lowering of the pressure built by the impulses in the partially emptied line such that other water blocks are formed. The former blocks are impacted by the latter blocks with high speed such that the former blocks obtain supplementary propulsion.

Document <CIT> describes a method of clearing a pipe of contents with an air system. The method may include providing air by the air system at high pressure and low velocity compressed air source until the contents begin to move within the pipe, providing air by the air system air at low pressure and high velocity blower until a majority of the contents are removed from the pipe, and continuing to provide air at low pressure and high velocity blower until substantially all remaining contents are removed from the pipe.

Document <CIT> discloses a method in accordance with the preamble of claim <NUM> and an apparatus in accodance with the preamble of claim <NUM> and describes a transfer apparatus which can be used for a transfer method of a coating material. The method applies a pig or pig shuttle to transfer a coating material in a pipe system.

In the art, a predetermined air pressure profile is released upon the pipe system contents, starting at an initial pressure, decreasing to an end pressure. The push phase is ended when the end pressure is reached, i.e. the pressure drops below a threshold value, or when the push phase is timed out. In these cases the pressures and pressure profiles are chosen such that at the end of the push phase a sufficient normalized amount of the contents has been cleared. In other cases the push phase is ended when a sudden unexpected pressure drop is detected. In the latter case, the pipe system contents were completely expelled prematurely.

When an insufficient normalized amount of contents have been cleared, or when the push phase ends prematurely relatively large normalized amounts of contents remain in the pipe system. Consequently an extensive blow phase is required to eventually clear the pipe system of its contents.

When too much contents are cleared from the pipe system in the push phase, compressed air may undesirably enter a container used for capturing contents removed from the pipe system, i.e. product, thereby causing overpressure in such a container and consequently obstructing filling of the container.

As a pipe system may comprise many product feed lines or pipes, each of which has to be cleared during production, and wherein pipes are made from opaque materials such as stainless steel, it is not possible to follow the pipe content while it is being cleared from the pipe. Thus completion of the clearing of the pipe system is uncertain.

It is an object of the invention to provide clearing of a pipe system from contents without the disadvantages described above.

The object is achieved by a method of clearing a pipe system from its contents in accordance with claim <NUM>.

By determining the air volume supplied to the pipe system, and simultaneously controlling the air supply to create a constant contents flow, the pipe system is effectively cleared without air overflowing the contents and without creating air passages in the contents. The contents travel speed can be set dependent on the contents, i.e. the viscous product in the pipe system.

By more effectively clearing the pipe system in the push phase, energy is saved in the blow phase, as less blowing activity is required to clear the remaining contents.

In an embodiment, the controlling the air flow at the proximal end of the pipe comprises controlling a regulation valve between the air supply and the proximal end of the pipe.

In an embodiment, the controlling the air supply to the proximal end of the pipe system comprises using a difference between the estimated contents travel speed and a preset contents travel speed value. This effectively allows the contents to be travelling in the pipe system at a predetermined preset speed.

In an embodiment, the controlling the air flow at the proximal end of the pipe system comprises controlling a regulation valve between the air supply and the proximal end of the pipe system. The controllable valve allows continuous real time control of the air supply into the pipe system, thus the contents travelling speed can be maintained constant at the preset speed.

The air supply comprises a compressed air container having a container volume. This is advantageous since the compressed air required for the clearing of the pipes can be loaded into the compressed air container which is then available for fast release in the push phase, alleviating compressed air sources from providing large quantities of compressed air at once.

The determining a volume of air supplied to the pipe system comprises measuring a pressure in the compressed air container, and measuring a pressure at the proximal end of the pipe system, and calculating the air volume supplied to the pipe system from a pressure difference in the air container between an initial pressure and a pressure in the air container after supplying air from the air container to the pipe system, the air container volume, and a pressure at the proximal end of the pipe system after the supplying of the air into the pipe system.

The determining a volume of air supplied to the pipe system further comprises compensating the volume of air supplied to the pipe system for a supply line volume, and an expansion of the air volume stored in the supply line prior to the supplying of the air to the pipe system.

Using this scheme, the volume passed into the pipe system is simply determined using pressure sensors. Thus, expensive air flow meters are obviated, and no sensors are required to detect the air front pushing the contents through the pipe system.

Accuracy in determining the air volume in the pipe system volume is thereby improved also for pipe clearing systems having an air supply line of substantial dimensions between the air supply and pipe system. Consequently, position and speed of the air front pushing the pipe system contents are improved.

In an embodiment, the determining an estimated contents travel speed from the volume of the air supplied to the pipe system comprises determining a position of an air-contents front in the pipe system from the volume of air supplied to the pipe system by compensating volume of air supplied to the pipe system with a pipe system diameter.

This allows the position of the air-contents front to be controlled. The air supply can for example be cut off when the air-contents front approaches the pipe system distal end. This prevents blow out of the pipe system, i.e. air pushed into a container capturing contents pushed out of the pipe system to be prevented. This further allows the speed of the air front pushing the pipe contents to be determined and to be controlled in a further step.

In an embodiment, the determining an estimated contents travel speed from the volume of the air supplied to the pipe system further comprises calculating at least two positions of the air-contents front at least two corresponding points in time and calculating the estimated contents travel speed from the difference in the at least two positions and the time difference between the at least two respective points in time.

Thereby the contents travel speed in the pipe system is determined without inspection, i.e. sensors, in the pipe system itself.

The object is further achieved by a system for clearing contents from a pipe system in accordance with claim <NUM>.

In an embodiment, the control means are arranged for regulating the air supply to the proximal end of the pipe system comprises using a difference between the estimated contents travel speed and a preset contents travel speed value.

In an embodiment, the control means comprise a controllable valve for controlling the air supply to the proximal end of the pipe system and a controller, controllably connected to the controllable valve. This allows the supply of air into the pipe system to be controlled.

In an embodiment, the controller comprises a PID-controller. This allows effective, responsive control of the contents speed without offset.

The air supply comprises a compressed air container having a container volume. The system can be self-sufficient and needs not be connected to an external compressed air supply.

The volume determining means comprise a first pressure sensor for measuring a pressure in the compressed air container, and a second pressure sensor for measuring a pressure at the proximal end of the pipe system, wherein the volume determining means are arranged further for calculating the air volume supplied to the pipe system from a pressure difference in the air container between an initial pressure and a pressure in the air container after supplying air from the air container to the pipe system, the air container volume, and a pressure at the proximal end of the pipe system after the supplying of the air into the pipe system.

The volume determining means are further arranged for compensating the air volume supplied to the pipe system for a volume of a supply line to the pipe system and an expansion of air in the supply line prior to supplying the air into the pipe system.

This allows air volume supplied to the pipe system be determined without the need for air flow sensors.

In an embodiment, the calculating means for determining an estimated contents travel speed from the volume of the air supplied to the pipe system are further arranged for determining a position of an air-contents front in the pipe system between the supplied air and the contents in the pipe system from the volume of the air supplied to the pipe system and a pipe system cross section area.

In an embodiment, the calculating means for determining an estimated contents travel speed are further arranged for calculating at least two positions of the air-contents front in the pipe system at at least two corresponding time points, calculating the estimated contents travel speed from a difference between the at least two positions at the at least two points in time and a time difference between the respective at least two point in time.

The invention will now be elucidated by the following drawings.

The invention will be further elucidated by the following description of exemplary embodiments.

In <FIG> a system <NUM> is shown for clearing a pipe system <NUM> from its contents. The pipe system <NUM> can be supplied with liquid viscous product via line <NUM>, which can be shut off by valve <NUM>. The pipe system <NUM> has a proximal end <NUM> near valve <NUM> and a distal end <NUM> near an outlet manifold <NUM>. The outlet manifold provides various outlets <NUM>, <NUM>', <NUM>" for example for connecting to a further process, a container for content cleared from the pipe system <NUM>, or a separator for separating content from air or rinse fluids used for clearing the pipe system <NUM>. The pipe system <NUM> can comprise at least one pipe which may be a one-segment pipe. The pipe system <NUM> may also comprise for example a multi-segmented, bent, curved, bifurcated pipes or a ramification of pipes. The pipes and/or segments may run in different directions, including horizontal, oblique and vertical directions. Furthermore, the pipes or pipe segments in the pipe system <NUM> can have cross sections of arbitrary dimensions and/or shapes. There may also be segments in the same pipe system having different cross sections and cross section shapes.

Contents transported in pipe system <NUM> can relate to viscous, low-viscous or non-viscous products which adhere to the pipe system walls. These products can be finished products, half-products or raw materials used in various industrial processes as can be utilized in petrochemical industry or food industry. The products may be smooth, but may also contain particles and/or solid fractions.

The system <NUM> for clearing the pipe system <NUM> comprises a compressed air container <NUM>, a supply line <NUM>, a regulation valve <NUM> for controlling a compressed air flow from the compressed air container <NUM> to the pipe system <NUM>, a compressor <NUM>, a blower <NUM> connected to the supply line <NUM> via controllable valve <NUM>. The air used is for example compressed air. A pressure sensor <NUM> is connected to the supply line <NUM>. The supply line <NUM> may connect to the pipe system <NUM> via valve <NUM>. The various valves <NUM>, <NUM>, <NUM>, <NUM>, <NUM>-<NUM>", compressor <NUM> and blower <NUM> are controlled by control unit <NUM>. Outlet manifold <NUM> can be formed by for example a three-way valve or separate valves <NUM>, <NUM>', <NUM>" connected to the distal end <NUM> of the pipe system <NUM>. The valves <NUM>, <NUM>', <NUM>" can be controlled by control unit <NUM> such that only a single valve is allowed to be opened while the remaining valves are closed. The blower <NUM> can for example be a claw pump, a screw pump or a side channel blower. The compressor <NUM> can be any type suitable air compression pump for filling compressed air container <NUM> with sufficient capacity for filling the container and at a sufficient pressure for allowing the compressed air container <NUM> to perform the moving of the pipe system contents.

As an alternative to the compressor <NUM>, the compressed air container <NUM> may be connected to a main compressed air supply which is usually available in food, petrochemical or other industry. Furthermore, the air container <NUM> and regulation valve <NUM> can be supplemented or replaced by a high pressure low volume compressor <NUM> as shown in <FIG>. The high pressure low volume compressor <NUM> is connected to the air supply line <NUM> via a valve <NUM>. The high pressure low volume compressor <NUM> can be controlled by the control unit <NUM> to provide the required pressure measured by pressure sensor <NUM> for performing the push phase.

The process of clearing the pipe system <NUM> has four phases as is depicted in <FIG>. The first phase is the push phase <NUM>, wherein a high pressure generated from compressed air container <NUM> and controlled by regulation valve <NUM> is applied to the proximal end <NUM> of the pipe system <NUM>. The pressure Pcontainer is measured by pressure sensor <NUM>, which value is communicated to the control unit <NUM>. Control unit <NUM> controls controllable valve <NUM>, such that the pressure in the supply line <NUM> is applied to the proximal end <NUM> when the pressure has reached a pre-set level.

When valve <NUM> is opened, air from compressed air container <NUM> pushes the contents of pipe system <NUM> towards to distal end <NUM> of the pipe system <NUM> wherein the outlet manifold <NUM> is set such that at least one of the outlet <NUM>, <NUM>', <NUM>" is open to allow the contents being pushed out of the pipe system <NUM> to be removed. The contents may for example be collected for re-use.

The pressure Pcontainer measured by pressure sensor <NUM> and the pressure Ppipe measured by pressure sensor <NUM> is used to control regulation valve <NUM> to create a decreasing pressure in time at the proximal end <NUM> of the pipe system <NUM>. The controlling by control unit <NUM> is arranged to cause contents in the pipe system <NUM> to continue moving towards the distal end <NUM> at a constant speed. The push phase <NUM> ends when the contents are sufficiently removed from the pipe system <NUM>. Preferably the end of the push phase <NUM> is alternatively determined by calculating a position of an air front in the pipe and establish that the air front is near the distal end <NUM> of the pipe system <NUM>. This air front is the interface of the air released from the compressed air container <NUM> into the pipe system <NUM> with the contents to be pushed out. Alternatively, as a safeguard, the sufficient removal of the contents can be detected by a sudden pressure drop measured by pressure sensor <NUM>, indicating that the compressed air can escape from the pipe system without blocking by contents within the pipe system <NUM>.

The control unit <NUM> is arranged to estimate the position of the air-contents front from the measured pressure Ppipe at the proximal end <NUM> by pressure gage <NUM>. When the control unit <NUM> has determined that the air front is near the distal end <NUM> of the pipe system <NUM>, corresponding to a position wherein for example at least <NUM>% of the contents is pushed out of the pipe system <NUM>, then regulation valve <NUM> is closed. Thereby the push phase <NUM> of <FIG> ends.

A new phase <NUM> of blowing the pipe system <NUM> is entered by starting blower <NUM> and opening valve <NUM> whilst valve <NUM> is kept open. In the blow phase <NUM>, the blower <NUM> provides an air flow in pipe system <NUM> such that any contents left behind on the pipe system walls during the push phase <NUM> is blown out. The blow phase <NUM> is usually performed during a preset time period and timed by control system <NUM>. The preset time period depends on the size and length of the pipe system, the viscosity of the contents, temperature, etc..

When the blow phase <NUM> is completed, the pipe system <NUM> can be rinsed in a rinse phase <NUM>. In the rinse phase <NUM>, the blower <NUM> blows air into the pipe system <NUM>, while simultaneously rinse fluid is injected in the supply line <NUM> connecting the blower <NUM> to the valve <NUM> and proximal end <NUM> of the pipe system <NUM>. The rinse fluid is for example water.

Following the rinse phase <NUM> the blower <NUM> is used for providing constant air flow through the rinsed pipe system <NUM> for drying in a drying phase <NUM>.

In <FIG> an extra cleaning phase <NUM> is shown following drying phase <NUM>. De cleaning phase <NUM> is similar to the rinse phase <NUM>, wherein cleaning agents or disinfectants can be added to the rinse fluid. The cleaning phase <NUM> can be followed by an additional rinse phase <NUM> and/or drying phase <NUM>.

In <FIG> a block diagram is shown of a control system <NUM> which is active in the push phase for controlling the pipe contents travel speed Vcontents. The functions <NUM>, <NUM>, and <NUM> shown in the block diagram <NUM> described below are performed in control unit <NUM>, to which the container pressure sensor <NUM> and the pipe system pressure sensor <NUM> are connected.

The pipe contents travel speed Vcontents is controlled by regulating an airflow from the compressed air container <NUM> into the pipe system <NUM> using a controlled valve <NUM> to obtain the set value Vset. Thus a pipe contents travel speed Vcontents can be maintained which is sufficiently high for removing the pipe contents from the pipe system <NUM>, and sufficiently low to prevent compressed air used for pushing out the contents from the pipe system <NUM> to be overrun with air, thereby leaving too much of the pipe contents in the pipe system.

In function block <NUM> the estimated pipe contents travel speed Vcontents is determined on the basis of the air volume in the pipe system Vpipe which has been supplied from the compressed air container <NUM> to the pipe system <NUM> in the push phase.

In block <NUM> the air volume in the pipe system Vpipe is determined from the of air volume supplied from the compressed air container <NUM> which is calculated from the pressure drop ΔPcontainer in the compressed air container which occurs when the air is released from the compressed air container <NUM> into the pipe system <NUM>, the compressed air container volume Vcontainer and the pressure Ppipe in the pipe system.

In function block <NUM> a sequence of air volume values Vpipe supplied to the pipe system <NUM> is determined from corresponding pressure measurements Pcontainer in the container <NUM> and the pipe system Ppipe. From there a sequence of changes in volume ΔVpipe of the air in the pipe system <NUM> i.e. a flow into the pipe system is determined. By compensating the air volume changes ΔVpipe in the pipe system for pipe diameter d in block <NUM>, the estimated pipe contents travel speed Vcontents being the speed of the air front pushing the contents from the pipe system <NUM> can be determined.

Alternatively the normalized amount of air released from the compressed air container can be determined with an air flow meter positioned in the supply line <NUM>. By adding up flow measurements in time, a normalized amount of air can be determined.

In subtractor <NUM> the estimated pipe contents travel speed Vcontents is subtracted from the set speed value Vset. With the calculated speed difference and a Proportional-Integration-Differentiation (PID) control function in block <NUM> a variable control signal is generated to control regulation valve <NUM>. The regulation valve <NUM> causes a variable air flow from the compressed air container <NUM> into the pipe system <NUM>.

The calculated estimate of the pipe contents travel speed Vcontents can be corrected for content viscosity with a contents speed correction factor F, which is determined by experiments using different products as pipe system contents. This prevents air to overflow the product near the end of the push phase, when most of the pipe contents have been pushed out of the pipe system <NUM>.

While emptying the pipe system <NUM> from contents by filling it with compressed air from the compressed air container <NUM>, the control unit <NUM> can determine that a predetermined threshold value of for example <NUM>% of the air volume in the pipe system is exceeded, indicating that the contents are sufficiently expelled from the pipe system <NUM>. The regulation valve <NUM> and/or the valve <NUM> can be closed, thereby ending the push phase.

In practice often the supply line <NUM> from the regulation valve <NUM> to the proximal end <NUM> of the pipe system has a non-negligible volume, affecting the calculation of the normalized amount of air released into the pipe system <NUM>,as the normalized amount of air from the compressed air container first has to fill the supply line <NUM> as well. In a pre-push phase, the supply line <NUM> is filled with air up to a preset pressure value Ps measured by pressure sensor <NUM> air by opening regulation valve <NUM>. When the preset pressure value Ps is attained the regulation valve <NUM> is closed again. The compressed air is then released into the pipe system in the push phase by opening valve <NUM>. This connects the pipe system <NUM> to the supply line <NUM>. Subsequently the pressure in the supply line <NUM> and pipe system <NUM> is regulated by the control system <NUM> and the regulation valve <NUM>.

When the valve <NUM> is opened, the pressure in the pipe system <NUM> and the supply line <NUM> together is controlled by the control unit <NUM> by controlling regulation valve <NUM> on the basis of the estimated contents speed Vcontents. The total amount of air supplied to the pipe system is now determined from air supplied from the air container <NUM> as described, and the air already in the supply line using the supply line volume Vsupplyline, the pressure drop in the supply line, which is equal to the pressure drop in the pipe system ΔPpipe since supply line <NUM> and pipe system <NUM> are now connected, and the pressure in the supply line and pipe system Ppipe.

In <FIG> fluid supplies <NUM>, <NUM>' are shown connected to supply line <NUM> via respective valves <NUM>, <NUM>'. The supply line <NUM> can be separated from the blower <NUM> via valve <NUM>. In the blow phase <NUM> the blower <NUM> is switched on and valve <NUM> activated for providing a sufficient air flow in the pipe system <NUM> to sustain the outward motion of the remaining contents in the pipe system.

Remaining contents in the pipe system <NUM> may form fluid plugs which move from the proximal end <NUM> to the distal end <NUM> of the pipe system <NUM>. In order to prevent mechanical vibration of the pipe system <NUM> caused by these fluid plugs, the blower <NUM> can be soft-started such that the pressure generated by blower <NUM> increases gradually at startup.

The rinse phase fluid supply <NUM> usually comprises water, but depending in the pipe contents, the rinse fluid composition may vary. Agents like detergents or disinfectants may be added to the rinse fluid.

As described, in a cleaning phase <NUM> instead of rinse fluid such as water, a cleaning fluid with a cleaning agents such as detergents or disinfectants can be injected from for example fluid supply <NUM>' into the supply line <NUM> via valve <NUM>'. A commonly used agent is for example sodium hypochlorite. After cleaning the pipe system <NUM>, the pipe system <NUM> can be rinsed using rinsing fluid to remove the cleaning fluid as in the rinse phase and subsequently dried as in the drying phase as is the case in the process of clearing the pipe system <NUM>. The combined blowing air in the supply line <NUM> using blower <NUM> and injecting a cleaning fluid with cleaning agent into the supply line <NUM>, and the injected cleaning fluid is blown by the airflow in the supply line <NUM> into a spray.

The control unit <NUM> can comprise a programmable logic controller (PLC) or any other computing device having input ports for acquiring process data such as pressures, flows, etc. and output ports for controlling devices in the process such as valves, compressors, blowers.

The computing device may comprise a microprocessor or microcontroller connected to a memory having programming instructions which are executable on the computing device. The programming instructions can be stored in the memory such as EPROM, Flash memory, computer discs and other computer readable devices.

Claim 1:
Method of clearing a pipe system (<NUM>) from its contents, the pipe having a proximal end and a distal end, the method comprising:
- providing an air supply to the pipe system at the proximal end (<NUM>) by applying an air pressure decreasing from an initial pressure as the bulk of the pipe contents get discharged gradually at the distal end (<NUM>) for obtaining a contents flow in the pipe system;
the method further comprising:
- determining a volume of air supplied to the pipe system by the air supply;
- determining an estimated contents travel speed from the volume of the air supplied to the pipe;
- controlling the air supply at the proximal end of the pipe for obtaining a predetermined pipe contents travel speed using the estimated contents travel speed,
- wherein the air supply comprises a compressed air container (<NUM>) having a container volume and wherein the determining a volume of air supplied to the pipe system comprises:
- measuring a pressure in the compressed air container; and
- measuring a pressure at the proximal end of the pipe system;
- calculating the air volume supplied to the pipe system from a pressure difference in the air container between an initial pressure and a pressure in the air container after supplying air from the air container to the pipe system;
- wherein the determining a volume of air supplied to the pipe system further comprises compensating the volume of air supplied to the pipe system for a supply line volume and an expansion of the air volume stored in the supply line (<NUM>) prior to the supplying of the air to the pipe system.