9. Steam quality tests
Introduction
9.1 A continuous supply of saturated steam is required for steam sterilization and
婴儿侧睡for humidification in certain EO sterilizers. Too high a level of non-condensable
gas will prevent the attainment of sterilizing conditions; too little moisture
奶豆腐怎么吃carried in suspension may allow the steam to become superheated during
expansion into the chamber, while excess moisture may cau damp loads. 9.2For all the tests, the steam should be sampled from the steam rvice pipe
to each sterilizer. The measurements are taken during a period of maximum
steam demand, when steam is first admitted to the sterilizer chamber.
9.3Silicone rubber tubing is porous to steam and should not be ud to carry
steam in the tests.
Non-condensable gas test
9.4This test is ud to demonstrate that the level of non-condensable gas in the
steam will not prevent the attainment of sterilization conditions in any part of the
load. (Possible sources of non-condensable gas are discusd in Part 2 of
this SHTM.) The method described should be regarded not as measuring the
exact level of non-condensable gas, but a method by which the provision of
acceptable steam quality can be demonstrated.
9.5The apparatus is shown and described in Figure 9. All sizes are nominal.
9.6Connect the needle valve to the steam rvice pipe as shown in Figure 9.
9.7Asmble the apparatus so that condensation will drain freely from the long
rubber tube into the sampling pipe. If the tube is too short, copper or stainless
steel tubing may also be ud.房子怎么画简单又漂亮
9.8Fill the container with cold water until it overflows. Fill the burette and funnel
with cold water, invert them and place them in the container. Draw out any air
that has collected in the burette.
9.9With the steam sampling pipe out of the container, open the needle valve and
allow steam to purge the air from the pipe. Place the pipe in the container,
locate the end within the funnel, and add more cold water until it flows through
the overflow pipe.
9.10Place the empty measuring cylinder under the container overflow.
9.11Adjust the needle valve to allow a continuous sample of steam into the funnel
sufficient to cau a small amount of steam hammer to be heard. Ensure that
all the steam is discharged into the funnel and does not bubble out into the
container. Note the tting of the needle valve. Clo the valve.
矗立近义词
9.12 Ensure that the container is topped up with cold water and that the measuring
cylinder is empty. Draw out any air prent in the burette
Figure 9: Apparatus for non-condensable gas test
a50ml burette with a minor mark of 1ml
b parallel-sided funnel with a nominal opening of 50mm
c rubber tubing – size to suit funnel an
d burette
d2000ml container with overflow at 1500ml
e steam sample delivery pipe – 6mm O/D with 75mm
upturn
f¼“ BSP needle valve
g250ml measuring cylinder with a minor mark of 10ml
h burette stand
i rubber tubing
j thermometer 0-100o C with a minor mark of 1o C
k overflow pipe
9.13Ensure that the sterilizer chamber is empty except for the usual chamber
furniture. Select and start the operating cycle.
9.14When the steam supply to the chamber first opens, open the needle valve to
the previously noted tting, allowing a continuous sample of steam into the
funnel sufficient to cau a small amount of steam hammer to be heard.
9.15Allow the steam sample to conden in the funnel. Any non-condensable gas
will ri to the top of the burette. Overspill formed by the condensate and the
water displaced by the gas will collect in the measuring cylinder.
9.16When the temperature of the water in the container reaches 70-75°C, clo the
needle valve. Note the volume of gas collected in the burette (V b) and the
volume of water collected in the measuring cylinder (V c).
9.17Calculate the fraction of non-condensable gas as a percentage as follows:
Fraction of non-condensable gas = 100 x (V b/V c).
9.18The test should be considered satisfactory if the fraction of non-condensable
gas does not exceed 3.5%.
读书的名言
9.19The test should be done two more times to check consistency. If the results of
the three tests differ significantly, then the cau should be investigated before
proceeding further.
Superheat test
9.20This test is ud to demonstrate that the amount of moisture in suspension with
steam from the rvice supply is sufficient to prevent the steam from becoming
superheated during expansion into the chamber.
证伪主义
9.21The method described here us a low-volume sample, continuously taken
from the centre of the steam rvice pipe. The level of superheat determined
by this method cannot be regarded as indicative of the true dryness of the
steam in the pipe since condensate flowing along the inner surface is not
collected. However, devices designed to parate free condensate are
incorporated into the steam delivery system to the chamber and therefore the
level determined by this method is reprentative of steam conditions likely to
prevail within the chamber during the plateau period.
9.22This test should normally follow a satisfactory test for non-condensable gas.
9.23This test, and the subquent dryness value test, require a pitot tube as shown
in Figure 10. The rest of the apparatus is shown and described in Figure 11. All
sizes are nominal.
9.24Fit the pitot tube concentrically within the steam rvice pipe as shown in
Figure 11.
受伤的英语the following equation:
T T Superheat o
e −=where T o is the boiling point o
f water at local atmospheric pressure.
9.29The test should be considered satisfactory if the superheat measured in the
expansion tube does not exceed 25°C.
高发明Figure 11: Apparatus for superheat test
To temperature measuring tube
Nylon bush Push fit into the tube ‘A’ – Suitable fitting for locating a temperature nsor into the
tube. To minimi heat
transfer between the fitting
and temperature nsor,
insulation may be required.
