≤ 20 %, then the entry of airborne contaminants from the outside into the operating room is considered to be 20 %, then the entry of airborne contaminants from the outside into the operating room is considered to be effectively prevented.
effectively prevented.
If no system-tested LTF outlets or surgical lights/satellites have been installed, then a system test (basic test If no system-tested LTF outlets or surgical lights/satellites have been installed, then a system test (basic test conditions as in E.5 and turbulence intensity measurement as in E.6) shall be carried out with all objects conditions as in E.5 and turbulence intensity measurement as in E.6) shall be carried out with all objects installed. The limit values specified in
installed. The limit values specified in D.3 shall be D.3 shall be maintainedmaintained..
D.2 Procedure D.2 Procedure D.2.1 General D.2.1 General
Before measurements are carried out, the system shall have successfully passed the system qualification and Before measurements are carried out, the system shall have successfully passed the system qualification and the preliminary visual test (flow visualization as in Annex B).
the preliminary visual test (flow visualization as in Annex B).
When carrying out velocity measurements to determine the turbulence intensity, Tu, a direction-independent When carrying out velocity measurements to determine the turbulence intensity, Tu, a direction-independent measurement system shall be used with an averaging time of at least 100 s and where at least one measured measurement system shall be used with an averaging time of at least 100 s and where at least one measured value is recorded per second. The sensor shall have a response time (t 63, or time necessary to reach 63 % value is recorded per second. The sensor shall have a response time (t 63, or time necessary to reach 63 % of its end value) of <
of its end value) of < 0,2 s. The error of measurement shall be no greater than ± 0,05 m/s and the accuracy of0,2 s. The error of measurement shall be no greater than ± 0,05 m/s and the accuracy of measurement shall be checked at the time intervals recommended by the manufacturer.
measurement shall be checked at the time intervals recommended by the manufacturer.
The turbulence intensity at each test location (measuring plane: 1,2 m above FFL) is determined by the The turbulence intensity at each test location (measuring plane: 1,2 m above FFL) is determined by the highest of two measurements. For the first
highest of two measurements. For the first measuremmeasurement the sensors are ent the sensors are perpendicuperpendicular to the lar to the flow direction inflow direction in the measuring plane, while for the second measurement the sensors are then rotated by 90° (see Figure D.1).
the measuring plane, while for the second measurement the sensors are then rotated by 90° (see Figure D.1).
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Figure D.1 — Position of turbulence intensity sensors in the measuring plane (2nd rotated by 90°)
All parameters and parameter constellations of the operating conditions tested shall be documented along with the relevant test results in a detailed test report.
D.2.2 Measuring and marking test positions
For the acceptance test, colour markings are placed below the LTF outlet as auxiliary and test positions. In the following example the laminizer size is 3,2 m × 3,2 m and that of the protected area is 3,0 m × 3,0 m; the colours used for the markings are by way of example only.
⎯ Project the positions of the four outer corners of the laminizer onto the floor area of the test room or operating room by dropping a perpendicular, and mark these in red as auxiliary positions. Other laminizer shapes (round, oval, etc.) shall be marked analogously by marking at least four positions so that within these shapes a rectangle with a maximum area is formed.
⎯ Then project the positions of the outer corners of the protected area onto the floor area of the test room or operating room using a series of black points to form a second rectangle.
⎯ The red markings indicating auxiliary positions can be removed at this point.
⎯ Make eight orange marks along the median lines of the diagonals and of the vertical and horizontal axes of the rectangle.
⎯ Make a white mark at the intersection of the diagonal with the vertical and horizontal axes.
Measuring point
Tu sensor
1stmeasurement 2nd measurement
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-DIN 1946-4:2008-12
58
Figure D.2 — Auxiliary positions and test positions projected on floor beneath LTF outlet (red line: projection of laminizer; black line: boundary of protected area)
D.2.3 Procedure for Tu measurement
The measurements shall be performed without operating tables and instrument tables.
Using a sensor fixed above the perpendicular of the test position, determine the three parameters flow velocity, temperature, and turbulence intensity in the measuring plane 1,2 m above FFL. Take two measurements each above the black, orange and white marks ( n = 17, see Figure D.2) and then average the two results for each position.
If the requirements for the protected area are not met during this test, then the effectiveness of the LTF outlet may be tested separately. To this end, temporarily (for the measurement only) install a flow stabilizer surrounding the entire outlet to a height of 1,0 m above FFL and repeat the turbulence intensity measurements. This allows a distinction to be made between external influences (e.g. room geometry, extract air flow) and the effects of the LTF outlet.
D.3 Requirements D.3.1 Protected area
Mean turbulence intensity at each test position (except for the corner positions): ≤ 20 % Mean turbulence intensity at each of the four corner positions: ≤ 30 % D.3.2 LTF outlet, separate (with temporary stabilizer surrounding outlet)
Mean turbulence intensity at each test position (except for the corner positions): ≤ 15 % Mean turbulence intensity at each of the four corner positions: ≤ 25 %
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