TWI862479B - Inner explosion resistant membrane door for a marine vessel - Google Patents

Abstract

An inner membrane door for a marine vessel comprises a first plate with an opening enclosed by a peripheral edge; a door connected to this first plate by a hinge construction; the door sealingly co-acting with said peripheral edge. The peripheral edge comprises a plate part having a wave shape with at least one wave. The door comprising a second plate or door leaf of stainless steel, in particular of 316L, which second plate or door leaf is received in a framework which co-acts sealingly with the peripheral edge in a closed position. The peripheral edge is deformable under the influence of an air pressure load acting on the membrane door in the closed position such that at least the door can be pressed out of the main plane it occupies when at rest while maintaining the co-action between the framework and the peripheral edge, and while providing mechanical integrity and fracture resistance to the inner membrane door for a marine vessel.

Description

Explosion-resistant inner membrane doors for marine vessels

The present invention relates to an explosion-proof inner membrane door for use on marine vessels as described in the preamble of claim 1.

An inner membrane door for marine vessels is known from EP-B-1144783 and is illustrated in Figures 1, 2 and 3. In Figure 1, a known inner membrane door 31 is shown, comprising a first plate 32 as a fixed frame and having an opening 34 surrounded by a peripheral edge 33. A door 37 is pivotally connected to this first plate 32 by two hinges 35, 36, so that the door 37 can cooperate sealingly with the peripheral edge 33 with its peripheral area 38. The first plate 32 carries a plurality of peripherally arranged clamps 39, which can be rotated simultaneously by a common operating mechanism 40 with an operating handle 41 and can cooperate with the peripheral surface 42 of a corresponding non-circular through-hole 43 in the door 37 by rotation. For each clamp 39, the peripheral surfaces 42 can have a contact surface 44 which is inclined relative to the main plane of the inner membrane door 31 in the closed condition, and the through-holes 43 have a form to allow a clamp 39 to pass therethrough. The door 37 of the known inner membrane door for marine vessels further comprises a second plate or door leaf 45 made of steel and housed in a frame 46 which cooperates with the peripheral edge 33 in the closed condition of the inner membrane door 31. The clamps 39 are arranged on the rotation axis 47. The through-holes 43 in the door 37 are correspondingly formed as slots. The peripheral edge 33 is deformable under the influence of the air pressure load on the inner membrane door in the closed position, so that the entire inner membrane door, consisting of the first plate with the peripheral edge and the door, can be compressed out of the main plane it occupies when at rest. By means of the handle 41, the pivot 47 of each clamp can be rotated between a closed position and a free position via a transmission arm 50, which is generally indicated by the symbol 49 via a system of a plurality of mutually coupled rods. As shown in Figures 2 and 3, the peripheral edge 33 comprises a relatively thin (6-9 mm), generally wavy sheet metal strip 51 having at least one wavy portion. The strip 51 extends entirely around the door opening 34 and is welded to the first plate 32 and to the remaining portion 52 of the peripheral edge 33. Figures 2 and 3 show the doors 45, 46 arranged in the closed position and illustrate the presence of hooking members on the peripheral edge 33 and the door 37, respectively, which hooking cooperation only begins when a certain minimum deformation of the inner film door 31 in the closed position is exceeded due to the pressure load acting on the edge of the inner film door 31. The hooking members include prismatic beams 57, 58, which form a separate part of the peripheral edge and the frame 46, respectively. The beams have respectively notched surfaces 59, 60 facing each other, which can start the cooperative operation of hooking onto each other in the state of substantial deformation under the influence of the air pressure load. This known inner membrane door for marine vessels meets high standards of explosion resistance.

One purpose of the present invention relative to the prior art is to provide an inner membrane door for marine vessels that meets higher standards of explosion resistance.

This object is achieved by an inner membrane door for marine vessels having the characterizing features of claim 1. The invention is based in part on the insight that the explosion resistance of an inner membrane door for marine vessels can be improved if the rupture resistance of the inner membrane door for marine vessels under the conditions of combined blast load and fragment penetration can be increased. The invention is particularly based on the insight that if an exploding warhead, warhead or bomb explodes in an inner compartment of a marine vessel closed by an inner membrane door, fragments of the exploding warhead will reach the inner membrane door before the door is significantly deformed due to pressure load, and the fragments can penetrate the inner membrane door to form holes therein. Afterwards, the pressure load of the explosion causes a significant deformation of the inner membrane door and can generate or propagate several cracks or fissures in the inner membrane door starting from the holes formed by the fragments, and these cracks can seriously reduce the explosion resistance of the inner membrane door when (part of) the door leaf 45 can be blown open. The present invention is based on the following insight: if the second plate or door leaf is made of stainless steel, the generation or growth of such cracks can be significantly reduced. It is noted that stainless steel is not an obvious choice for use in inner doors of marine vessels, particularly as stainless steel is more expensive than more commonly used steel grades (e.g., Fe235), and further as inner doors are not subject to corrosion as they are not exposed to the aggressive marine environment. However, after much research and experimentation, the inventors unexpectedly discovered that by using a second plate or door leaf of stainless steel, the crack resistance of the inner membrane door, particularly the second plate or door leaf, under air pressure loads in the presence of debris holes is substantially increased.

In a specific embodiment of the inner membrane door for marine vessels of the present invention, the second plate or door leaf is made of austenitic stainless steel of the AISI 300 series, which is weldable, retains good strength values and has the required high toughness. This perspective of the present invention is based on the insight that the second plate or door leaf, in particular made of austenitic stainless steel, provides increased explosion resistance while being easy to integrate into the inner membrane door. It is particularly beneficial when the second plate or door leaf is made of austenitic stainless steel of the AISI 300 series or ASTM/UNS S3xxxx series. Preferably, the second plate or door leaf is made of austenitic stainless steel, in particular 316L low carbon austenitic stainless steel.

In another specific embodiment of the inner membrane door for marine vessels of the present invention, the second plate or door leaf has a thickness of 4-5 mm. This is in contrast to EP-B-1144783, which teaches that the second plate or door leaf needs a maximum thickness of 3 mm, and the present invention is further based on the following insight: for most types of explosions, the rupture and explosion resistance of the inner membrane door for marine vessels is sufficient when the second plate or door leaf has a thickness of 4-5 mm.

31: Gate of the inner membrane

32: First board

33:Surrounding edges

34: Open mouth

35,36: Hinge

37: Door

38:Surrounding area

39: Clamp

40: Joint operating agency

41: Operating handle

42: Surrounding surface

43: Non-circular through-holes

44: Contact surface

45: Second board or door leaf

46:Framework

47: Rotating shaft

49: System

50: Transmission arm

51: Thin metal strips

52: The rest of the surrounding edge

57,58: Prismatic beam

59,60: incision surface

The present invention has been described above with reference to the inner membrane door for marine vessels known in EP-B-1144783, and the known inner membrane door for marine vessels is shown in the drawings. Among them: Figure 1 shows a perspective view of the inner membrane door for marine vessels known in EP-B-1144783 in an open position; and Figures 2 and 3 show a cross-sectional view of a portion of the inner membrane door for marine vessels known in EP-B-1144783 in a closed position, illustrating the hook structure.

When compared to the inner membrane door for marine vessels known from EP-B-1144783, the construction of the inner membrane door for marine vessels of the present invention is substantially the same, except that, according to the present invention, the second plate or door leaf 45 is made of stainless steel. As discussed above, the use of stainless steel for inner doors of marine vessels is not an obvious choice, particularly since stainless steel is more expensive than commonly used steel grades (e.g., Fe235), and further since inner doors are not susceptible to corrosion. However, after much research and experimentation, the inventors unexpectedly discovered that by using a second plate or door leaf 45 of stainless steel, preferably weldable austenitic stainless steel, in particular austenitic stainless steel of the AISI 300 series or ASTM/UNS S3xxxx series, the explosion resistance, in particular the crack resistance, of the inner door structure can be substantially increased. Preferably, the second plate or door leaf is made of low carbon austenitic stainless steel, in particular 316L low carbon austenitic stainless steel. With such a second plate or door leaf, the explosion resistance, in particular the crack resistance, of the inner membrane door can be substantially increased. It is noted that the chemical composition of AISI 300 series or ASTM/UNS S3xxxx series steel, and in particular 316L, is generally known in the art. In particular, the second plate or door leaf 45 has a thickness of 4-5 mm. Such a thickness provides sufficient rupture and explosion resistance to the inner membrane door of a marine vessel for most types of explosions.

31: Gate of the inner membrane

32: First board

33:Surrounding edges

34: Open mouth

35,36: Hinge

37: Door

38:Surrounding area

39: Clamp

40: Joint operating agency

41: Operating handle

42: Surrounding surface

43: Non-circular through-holes

44: Contact surface

45: Second board or door leaf

49: System

50: Transmission arm

Claims (1)

A blast-resistant inner membrane door for marine vessels comprises: a fixed frame comprising a first plate having an opening surrounded by a peripheral edge; a door pivotally connected to the first plate by at least one hinge structure so that the door utilizes its peripheral area to sealably cooperate with the peripheral edge, the peripheral edge comprising a wave-shaped plate portion having at least one wave portion; the door comprises a steel second plate or door leaf received in a frame, the frame sealingly cooperating with the peripheral edge in a closed position; the first plate carries a plurality of peripherally arranged clamps, The clamps are arranged on a rotating shaft, the clamps can be rotated simultaneously by a common operating mechanism having an operating handle, and can cooperate with several peripheral surfaces of several non-circular through-holes in the door through rotation; the peripheral edge is deformable under the influence of a predetermined pressure load on the inner membrane door in the closed position, so that at least the door can be compressed out of the main plane occupied when it is at rest, while maintaining the cooperation between the frame and the peripheral edge and the mechanical integrity of the inner membrane door, characterized in that: the second plate or door leaf is made of AISI The second plate or door leaf is made of weldable austenitic stainless steel of 300 series or ASTM/UNS S3xxxx series, and the second plate or door leaf has a thickness of 4 to 5 mm. The second plate or door leaf is made of 316L low carbon austenitic stainless steel.