Procedure for monitoring a pipeline

The invention relates to a method for monitoring a pipeline for transporting petrochemical liquids or gases according to the preamble of claim 1 and an apparatus according to the preamble of claim 6.

For the transport of environmentally hazardous media a line pipe has been disclosed, which consists of two concentrically arranged metal pipes, corrugated and in which the gap between the tubes by pressure or vacuum is monitored. (DE-C-21 64 814)

Although this pipe excludes an unnoticed event of damage most likely, is where legal provisions are missing, used for cost reasons an emaciated pipe. Such available under the trade name "Flexwell suction" pipe comprises a corrugated metal tube, on which rests an extruded plastic sheath. Also in this pipe is a two-layer pipe (metal corrugated pipe plastic pipe), but monitoring is not provided here.

In the monitored line pipe in general, the monitoring pressure is higher than the maximum delivery pressure of the medium. This is an entry of the medium into the interstitial space and penetrating into the monitoring apparatus and possibly an uncontrolled escape of the fluid being at this end can be avoided. At gas stations that feed lines are in operation case under a pressure of max. 3 bar. By simultaneous closing of several nozzles but can also pressure surges of up to 14 bar occur. In this case, the regular monitoring pressure would have to min. 5 bar, but possibly be adjusted to 16 bar. In the known conduit pipe from two corrugated metal pipes, of which the inner moreover still transmits a reinforcement, these pressures are almost without problems. For pipes whose inner and outer tubes of a less stable material, such as plastic, these would either burst (outer tube) or collapse (inner tube). Measures to increase mechanical stability of the material for the inner and outer tube, would raise costs significantly higher.

The present invention addresses the problem of specifying a method for monitoring a pipeline for transporting petrochemical liquids or gases which reliable reports at any time a review of the protective effect of the outer tube, precludes uncontrolled escape of the pumped medium, the formation of explosive mixtures in the interstitial space prevents as well as a sucking and forwarding that ignitable mixtures avoids it altogether. Moreover, the process should be particularly applicable to pipe components made of materials of low strength such as plastic pipes.

This object is achieved by the detected in the characteristics of claims 1 and 6 features.

By constantly monitoring the pressure in the interstitial space between the inner and outer tube both damage Innenals may also be reported to the outer tube. Minor damage to the inner tube are using this method can not be determined under certain circumstances. The circulation of the gas in the interstitial space and the bypassing of the gas to probe reports certainly a case of damage to the inner tube.

During the monitoring space is continuously pressure-monitored, except for the time when the gas is circulated, the second measure - the checking means of the sensors only in certain periods, eg durchgeführt.Wird every 60 minutes reported a case of damage, in any case, the plant will off.

The invention is further illustrated by the embodiments to 3 schematically shown in the figures the first

1 shows the scheme of monitoring system for in line 1, line 2, line 3 and 4 strand is existing plant for conveying petrochemical liquids, eg shown a gas station. The material forming each strand line pipe consists of an inner tube, an outer tube and a monitoring room.

The interstitial space of each strand is via a feed line Z₁, Z₂, Z₃, Z₄ and a line L connected to a pressure generator GF. In the embodiment of the pressure generator GF is a nitrogen-filled gas cylinder. In place of the gas cylinder, however, a conventional pump can occur. With a reducing valve RV monitoring pressure can be precisely adjusted and read on a manometer M. Such systems are known per se and are suitable for permanent pressure monitoring of the monitoring space of monitorable pipes.

In the inlets Z₁, Z₂, Z₃, and Z₄ are pressure switch D₁, D₂, D₃ and D₄, Solenoid valves X₁, X₂, X₃ and X₄ and probes S₁, S₂, S₃ and S₄ provided. In addition, in the line L is a further sensor S_c provided. In the line L boxes also contain a gas pump P, a pressure vessel DB and another solenoid valve Z. In a bypass line B another solenoid valve C is located.

The sensors S₁, S₂, S₃, S₄ and S_c is it to sensors that detect and pass on the presence of hydrocarbons.

To check the inner tube for leaks, periodically all solenoid valves X₁, X₂, X₃ and X₄ with the exception of the solenoid valve, which is located in the supply line to the strand to be checked, briefly closed. Simultaneously, the gas pump P runs for a specific short period. The equipment must be connected so that in this period, the alarm function of the corresponding pressure switch D₁, D₂, D₃ or D₄ is disabled. The gas produced in the interstitial space - usually nitrogen is preferred - is compressed in the pressure vessel DB, a limit indicator G2 limited by switching off the gas pump P the maximum compression pressure in the pressure vessel DB. The max. Compression is optimized depending on the size of the pressure vessel DB, the volume of the interstitial space of the height of the monitor pressure etc.. The cut-off time for the gas pump P is at least reached when the pressure measured by the limit sensor G1 to a value of 0.2 bar above atmospheric pressure has fallen. Occurs an alarm event is checked in the same way every other strand. In this way can be found, which strand is damaged.

After completion of the respective tests, the otherwise closed solenoid valve C opens in the bypass line B, to allow pressure equalization between the pressure vessel and the respective DB checked strand. Until the pressures eventually equalize (circuit z. B. over timing) is the gas pump P and the alarm function of the respective pressure switch D₁, D₂, D₃ or D₄ disabled. Only then is when the pressure drop over the riser, an alarm can be triggered. For smaller systems, where the size of the pressure vessel DB is not a problem, the monitor mode could be found on all lines simultaneously - be extended - rather than individually.

During the pumping operation, a part of the present in the monitoring space is determined by the gas supply lines Z₁, Z₂, Z₃ and Z₄ at the sensors S₁, S₂, S₃ and S₄ bypassed. This gas is hydrocarbon-based, the corresponding sensor is responsive to, and it can be determined that in the corresponding strand is present an inner tube damage. In this case, the system must be shut down or defective train shall be decommissioned. If no claim on, the solenoid valve C is closed again variables and the pressure monitoring cycle is set again, ie by opening the solenoid valves X₁ to X₄ monitoring pressure in the line L, the supply lines Z₁ to Z₄ and in the monitoring area of ​​the strands 1 to 4 by pressure equalization on again. The sensor S_c is required for the case that one of the sensors S₁ to S₄ fails.

In the figures 2 and 3, line pipes are illustrated in lateral section, for which the inventive method is particularly suitable.

2 shows an inner tube 1, which comprises a corrugated metal tube, surrounded by an outer tube 2 made of an extruded plastic pipe. The interstitial space 3 extends here in the form of a helix between the inner tube 1 and outer tube 2. Between the inner tube 1 and the outer tube 2 may be provided a metal foil, not shown, the bonded via a co-polymer to the outer tube 2 at its extrusion. This metal film increases the pressure resistance of the outer tube 2 and prevents diffusion of gas through the plastic pipe.

If it is in the inner pipe 1 around an annularly corrugated metal tube, the outer tube 2 at its inside should have a profile in order to ensure a continuous monitoring room third

In Figure 3, consists of both the inner tube 10 and the outer tube 20 made of extruded plastic tubes, which are held by a helical spacer 40 concentrically with each other, and thereby produce the interstitial space 30 between them.

Also in this pipe construction it may be advantageous to provide not shown metal foils in the structure both of the inner tube 10 and the outer tube 20th

The spacer 40 may be omitted if the inner tube 10 and / or the outer tube 20 has a profiling z. B. in the form of longitudinal ribs on its side facing the adjacent tube-facing surface.