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发表于 2008-7-22 23:30
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来自： 中国山东济南
在IACS里有对它的要求:
Air Pipe Closing Devices
P3.1 General requirements
Where air pipes are required by the Rules or Load Line Convention, 1966 to be fitted
with automatic closing devices, they are to comply with the following:
P3.2 Design
P3.2.1 Air pipe automatic closing devices shall be so designed that they will withstand
both ambient and working conditions, and be suitable for use at inclinations up to and
including ± 40 o.
P3.2.2 Air pipe automatic closing devices shall be constructed to allow inspection of
the closure and the inside of the casing as well as changing the seals.
P3.2.3 Efficient ball or float seating arrangements are to be provided for the closures.
Bars, cage or other devices are to be provided to prevent the ball or float from
contacting the inner chamber in its normal state and made in such a way that the ball
or float is not damaged when subjected to water impact due to a tank being overfilled.
P3.2.4 Air pipe automatic closing devices are to be self-draining.
P3.2.5 The clear area through an air pipe closing device in the open position shall be
at least equal to the area of the inlet.
P3.2.6 An automatic closing device is to:
a) Prevent the free entry of water into the tanks,
b)Allow the passage of air or liquid to prevent excessive pressure or
vacuum coming on the tank.
P3.2.7 In the case of air pipe closing devices of the float type, suitable guides are to be
provided to ensure unobstructed operation under all working conditions of heel and
trim.
P3.2.8 The maximum allowable tolerances for wall thickness of floats should not
exceed ± 10% of thickness.
P3.2.9 The inner and the outer chambers of an automatic air pipe head is to be of a
minimum thickness of 6 mm.
P3.3 Materials
P3.3.1 Casings of air pipe closing devices are to be of approved metallic materials
adequately protected against corrosion.
P3.3.2 For galvanised steel air pipe heads, the zinc coating is to be applied by the hot
method and the thickness is to be 70 to 100 microns.
P3.3.3 For areas of the head susceptible to erosion (e.g. those parts directly
subjected to ballast water impact when the tank is being pressed up, for example the
inner chamber area above the air pipe, plus an overlap of 10o or more either side) an
additional harder coating should be applied. This is to be an aluminium bearing epoxy,
or other equivalent, coating, applied over the zinc.
P3
(1991)
(Corr. 1
May
1998)
(Rev.1
May
2001)
(Corr.1
April
2002)
(Rev.2
Mar 2004)
IACS Req. 1991, Rev.2 2004
P3-1
P3
P3.3.4 Closures and seats made of non-metallic materials are to be compatible with
the media intended to be carried in the tank and to seawater and suitable for operating
at ambient temperatures between -25 oC and 85 oC.
P3.4 Type Testing
P3.4.1 Testing of Air Pipe Automatic Closing Devices
Each type and size of air pipe automatic closing device shall be surveyed and type
tested at the manufacturer’s works or other acceptable location according to the
Classification Society’s practice. The minimum test requirements for an air pipe
automatic closing device shall include the following:
a) Determination of the Flow Characteristics.
The flow characteristics of the air pipe closing device are to be determined.
Measuring of the pressure drop versus rate of volume flow is to be carried out
using water and with any intended flame or insect screens in place.
b) Tightness test during immersion/emerging in water.
An automatic closing device is to be subjected to a series of tightness tests
involving not less than two (2) immersion cycles under each of the following
conditions:
i) The automatic closing device is to be submerged slightly below the
water surface at a velocity of approximately 4 m/min. and then returned
to the original position immediately. The quantity of leakage shall be
recorded.
ii) The automatic closing device is to be submerged to a point slightly
below the surface of the water. The submerging velocity is to be
approximately 8 m/min and the air pipe vent head is to remain
submerged for not less than 5 minutes. The quantity of leakage shall be
recorded.
iii) Each of the above tightness tests shall be carried out in the normal
position as well as at an inclination of 40 degrees.
The maximum allowable leakage per cycle shall not exceed 2 ml/mm of
nominal diameter of inlet pipe during any individual test.
P3.4.2 Testing of non-metallic Floats
Impact and compression loading tests shall be carried out on the floats before and
after pre-conditioning as follows:
P3
cont’d
Test temperature °C
Test condition - 25 20 85
Dry + + +
After immerging in water + + +
After immerging in fuel oil - + -
Immerging in water and fuel oil is to be for at least 48 hours
P3-2 IACS Req. 1991, Rev.2 2004
a) Impact Test
The test may be conducted on a pendulum type testing machine. The floats
shall be subjected to 5 impacts of 2.5 Nm each and shall not suffer permanent
deformation, cracking or surface deterioration at this impact loading.
Subsequently the floats shall be subjected to 5 impacts of 25 Nm each. At this
impact energy level some localised surface damage at the impact point may
occur. No permanent deformation or cracking of the floats shall appear.
b) Compression Loading Test
Compression tests shall be conducted with the floats mounted on a supporting
ring of a diameter and bearing area corresponding to those of the float seating
with which it is intended that float shall be used. For ball type float, loads shall
be applied through a concave cap of the same internal radius as the test float
and bearing on an area of the same diameter as the seating. For a disc type
float, loads are to be applied through a disc of equal diameter as the float.
A load of 350 kg shall be applied over one minute and maintained for 60
minutes. The deflection shall be measured at intervals of 10 minutes after
attachment of the full load. The record of deflection against time is to show no
continuing increase in deflection and, after release of the load, there shall be
no permanent deflection.
P3.4.3 Testing of Metallic Floats
Tests shall be conducted in accordance with 3.4.2 a). The tests shall be carried out at
room temperature and in the dry condition. |
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