WO2008074163A1

WO2008074163A1 - Relief vent

Info

Publication number: WO2008074163A1
Application number: PCT/CH2006/000714
Authority: WO
Inventors: Karl Solenthaler
Original assignee: Bühler AG
Priority date: 2006-12-20
Filing date: 2006-12-20
Publication date: 2008-06-26

Abstract

The invention relates to a relief vent comprising an inlet and outlet pipe (1, 3), wherein the inlet pipe (1) is enclosed in an upper part (2) of the relief vent by an outer pipe whose end face is assigned a flame filter.

Description

Explosion diverters

The invention relates to a discharge vent as it is used, for example in conveyors, silos or mills for the application in which the risk of dust explosions or fires.

When conveying and cleaning bulk material, such as grain, a conveyor string but also the environment is more or less loaded with dry dust, which can lead to fires and explosions in the presence of an ignition source. Individual machines may e.g. be protected by rupture discs or explosion flaps (for example, according to DE-U-29521209 or DE-A-4334280) for the discharge of pressure shocks. If the pressure relief is used in closed rooms, it is necessary to protect the rooms and the employees therein, the pressure relief on a possible. Short pipe (so-called blow-off pipe) to lead in a harmless direction into the open or to prevent the flame escape safely by tested devices. These devices are called flame filters (quench) and are connected downstream of the rupture disk or the Ex valve. Such an explosion-relief valve for closed rooms according to DE-A-19946213 is known, in particular for the crankcase of internal combustion engines.

To reduce the dust concentration in the machines and e.g. To keep silos as low as possible and to minimize the risk of explosions and to create a slight negative pressure to prevent dust leakage, these devices are aspirated and the dust-laden air fed to a filter.

Nevertheless, if an explosion occurs in a machine that is aspirated (piped to a filter), the velocity of explosion in the pipe can increase dramatically, causing the filter to burst due to flame jet ignition and pre-compression, despite the installation of pressure relief. In order to prevent this, a so-called discharge chute ("bursting pot") was temporarily installed in front of the filter. which directs the strong flame jet and the pressure impulse Ld. R. via exhaust pipe into the open air (over the roof or side wall of the building). Since the discharge chute via blow-off pipe with the conditions of the environment (outside air) is connected, it comes because of the usually existing temperature difference between inside and outside to condensation in the discharge chimney and passes as precipitation through the pipes partly into the machines. In production and aspiration air strands in grain mills and the like, such a precipitate leads to undesirable deposits and possibly clogging and corrosion by moist dust or product. In the manual of explosion protection (Henrikus Stehen, chapter 6.4.3.5) ideal and real design rules are named for the geometric design of relief vents. It is found that due to the flow resistances and the resulting pressure drop in the discharge slot for a realistic dimensioning an area equality of the cross section of the incoming power (A1) and an annular surface (A2) of the outgoing power is not given. Therefore, the surfaces (A1) and (A2) should be the same size and be twice as large compared to a cylindrical overflow surface (A3).

By such an arrangement, however, the efficiency against flame transmission decreases sharply and the pollution in the form of deposits increases. Deposits are to be avoided in terms of explosion technology in the discharge vent.

The invention is therefore based on the object to develop a discharge vent, which avoids the disadvantages of the prior art. The solution of the problem is achieved with the features of the claim.

The discharge vent includes an inner tube which is surrounded by an outer tube. At one end, both pipes pass into connecting pieces for pipes. On the other end face either a rupture disc with flame filter or a relief valve with integrated flame filter is arranged. Pressure surges can escape harmless, flame escape into the environment / operating rooms is prevented. Likewise, the dreaded flame jet ignition is prevented by the deflection of 180 degrees. The discharge vent is compact and requires only relatively small safety distances in the room. It is crucial that the cross-sectional area between the upper and lower part of the relief slot on real aspects (or slightly smaller) is formed, while the cross-section of the rupture disk and the distance of the inner tube for this purpose should be designed according to ideal points (or slightly larger).

Advantageous embodiments are disclosed in the subclaims. Thus, the inner tube is preferably designed as an inlet tube and the outer tube as an outlet tube of the air flow. The discharge vent is preferably arranged vertically or slightly obliquely.

The outer tube or the upper part of the relief slot can be heated and / or a rupture disk is thermally insulated in order to avoid condensation.

The invention will be described in more detail in embodiments with reference to a drawing. The drawing shows in the single figure a discharge vent in a side view

The upright relief vent has an outer tube (outlet tube 3), in which an inner tube (inlet tube 1) is arranged, whose end face is located below the end face of the outer tube. On this end face of the outer tube 1, an explosion valve with flame filter or rupture disc is arranged. Explosion pressure surges are discharged axially, flames are extinguished in the flame filter before exiting.

Structure of the Lower Part of the Relief Chute (ES):

a. with a centric to the ES-top 2 inlet tube 1 with diameter D1 and an angle beta at an angle tapered outlet tube 3 with D4 as the exit diameter and D3 as a concentric circle to D1 as the upper diameter of the ES base. D1 and D4 are usually the same size

Beta is in the range 20 to 35 °, preferably 30 ° b. The terms inlet tube 1 and outlet tube 3 apply to the air flow c. An explosion can occur in the direction of air or against it. If, based on the plant safety analysis, it is clear from which side an explosion is to be expected, this must be connected to the concentric diameter D1. If explosions from both sides are to be expected, then the side to be connected to D1, at which the higher probability is to be expected. d. The position of the two tubes 1 and 3 has to be made for fluidic reasons so that D3 corresponds to the real-world formulas or slightly smaller D3 = D1 and that the taper of the oblique tube 3, if possible <12 °, so that due to the Diffuser principle by cross-sectional enlargement, the speed reduction is converted into pressure energy and the pressure loss in the lower ES range can thus be largely prevented. This is particularly important if the air enters the tube 3. e. D3 is the upper diameter at the ES lower part and identical to the lower diameter of the ES upper part 2 f. The angle alpha> 55 ° ensures that hardly any product can accumulate in the ES.

Construction of the ES upper part with rupture disk:

G. When ES is primarily a very high efficiency against flame transmission in the outflowing pipe (explosion direction) is required. This is determined in the ES upper part 2 and is the better, the more real the geometry and the lower the response pressure of a rupture disk is selected at D2. H. In the event that the explosion enters the pipe 1, an ideal overflow gap H is preferably dimensioned and combined with a rupture disk (type examination) approved for discharge chutes. The explosion then hits the rupture disk, which opens immediately, with all its force. Depending on the rupture disc configuration, H can also vary slightly larger dimensions. However, the distance is always smaller than the real sizing rules. i. In the event that an explosion occurs in the pipe 3, it is important that the speed accelerates again as of D3 as a result of a narrowing annular gap is targeted and bounces as a result of the pipe constriction in the form of a ring cross-section on the opening bursting disc. j. The upper ES diameter D2 should therefore be "ideal", but due to the burst disk size grading, it may be necessary to deviate slightly, depending on the diameter ratios of "ideal". k. When air enters the pipe 1 (D1) results in the reduction of the diameter of D2 to D3 and the taper <12 ° due to the diffuser effect in the annular gap of the ES shell 2 a speed reduction, which is converted into pressure energy, which in turn reduces the pressure losses. Subsequently, the air in the ES lower part is accelerated again and possibly deposited dust is entrained.

I. Due to the largely ideal dimensioning, "dead corners" with product accumulation are prevented, which is not only important in terms of explosion technology but also for reasons of sanitation requirements.

At the lower end faces, both pipes pass into pipe sockets for pipe strings. The outer tube is such. B. with a dust filter, not shown, and the inner tube z. B. connected to silo cells. A reverse air flow is possible. In this regard, the relief vent generally relies on the disclosure of DE-A-102004048929.

reference numeral

Inlet pipe top outlet pipe

Claims

claims

1. relief vent with an inlet tube (1), which is surrounded by an outer tube of an upper part (2), wherein an end face of the upper part (2) is assigned an explosion valve with rupture disc or a flame filter, characterized in that the cross section between upper part (2 ) and a lower part "real" is designed.

2. relief vent according to claim 1, characterized in that an outlet pipe (3) is arranged at an angle to the inlet tube (1).

3. relief vent according to claim 1 or 2, characterized in that the conicity of the outlet pipe (3) is less than 12 °.

4. relief vent according to claim 1 or 2, characterized in that the conicity of the outer tube of the upper part of the diameter (D3) in the direction of diameter (D2) is less than 12 °.