scholarly journals Autoclaves and their dangers and safety in laboratories

1975 ◽  
Vol 75 (3) ◽  
pp. 475-487 ◽  
Author(s):  
E. H. Gillespie ◽  
S. A. Gibbons
Keyword(s):  
High Temperature ◽  
Internal Pressure ◽  
Accelerated Cooling ◽  
Cooling Stage ◽  
Safe Level ◽  
Downward Displacement ◽  
Fluid Media ◽  
The Media ◽  
Heating Up ◽  
High Internal Pressure

SUMMARYUsing a laboratory downward displacement vertical autoclave with the help of thermocouples recorded on a 12 point multichannel strip recorder, the risk of failing to sterilize laboratory discard buckets has been demonstrated. The use of proper temperature and time controls can prevent this risk.A load in a bucket with perforated sides is more easily sterilized than in a solid bucket. Wire baskets, where appropriate, facilitate the sterilizing practice. The addition of water to a bucket does not reduce the time of heating up.It is desirable that sealed bottles of media should not be sterilized in simple downward displacement autoclaves, but if used, strict monitoring of temperatures and times is essential both in the heating up stage and especially in the cooling stage. The temperatures in bottles are slow to rise and very slow to fall. Bottles at high temperature 80–405° C. or over have a high internal pressure which can allow the bottles to explode when subjected to thermal shock if removed too early.It is suggested that all laboratory autoclaves should have a load temperature simulator or similar device to control the temperature of the load during the cycle automatically. For the sterilization of fluid media, it is suggested that, in addition to a simulator there should be accelerated cooling to reduce damage to the media and, what is more important, to rapidly bring down the temperature and thus the internal pressure in the bottles to a safe level. The opening of the sterilizer door or lid should be automatically controlled by the load temperature simulator.

scholarly journals Structural Transformations and Mechanical Properties of Metastable Austenitic Steel under High Temperature Thermomechanical Treatment

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 645
Author(s):  
Igor Litovchenko ◽  
Sergey Akkuzin ◽  
Nadezhda Polekhina ◽  
Kseniya Almaeva ◽  
Evgeny Moskvichev
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
High Temperature ◽  
Austenitic Steel ◽  
Structural Transformations ◽  
Initial State ◽  
Twin Boundaries ◽  
Metastable Austenitic Steel ◽  
Average Grain Size ◽  
Heating Up

The effect of high-temperature thermomechanical treatment on the structural transformations and mechanical properties of metastable austenitic steel of the AISI 321 type is investigated. The features of the grain and defect microstructure of steel were studied by scanning electron microscopy with electron back-scatter diffraction (SEM EBSD) and transmission electron microscopy (TEM). It is shown that in the initial state after solution treatment the average grain size is 18 μm. A high (≈50%) fraction of twin boundaries (annealing twins) was found. In the course of hot (with heating up to 1100 °C) plastic deformation by rolling to moderate strain (e = 1.6, where e is true strain) the grain structure undergoes fragmentation, which gives rise to grain refining (the average grain size is 8 μm). Partial recovery and recrystallization also occur. The fraction of low-angle misorientation boundaries increases up to ≈46%, and that of twin boundaries decreases to ≈25%, compared to the initial state. The yield strength after this treatment reaches up to 477 MPa with elongation-to-failure of 26%. The combination of plastic deformation with heating up to 1100 °C (e = 0.8) and subsequent deformation with heating up to 600 °C (e = 0.7) reduces the average grain size to 1.4 μm and forms submicrocrystalline fragments. The fraction of low-angle misorientation boundaries is ≈60%, and that of twin boundaries is ≈3%. The structural states formed after this treatment provide an increase in the strength properties of steel (yield strength reaches up to 677 MPa) with ductility values of 12%. The mechanisms of plastic deformation and strengthening of metastable austenitic steel under the above high-temperature thermomechanical treatments are discussed.

Towards the Development of Filament Wound Composite Structures Submitted to Very High Internal Pressure, Based on Complex Geometry Shapes

2013 ◽  
Author(s):  
Erik Vargas Rojas ◽  
David Chapelle ◽  
Dominique Perreux
Keyword(s):  
Internal Pressure ◽  
Composite Structures ◽  
Complex Geometry ◽  
Industrial Applications ◽  
Filament Winding ◽  
Complex Geometries ◽  
Filament Wound ◽  
Complex Shapes ◽  
Filament Wound Composite ◽  
High Internal Pressure

Industrial applications, especially composite structures bearing high internal pressure, and fabricated using the filament winding process face certain difficulties like the reinforcement of complex shapes, as well as the correct placement of fibers over the surface of a mandrel. In some cases the definition of the manufacturing parameters respond more to cost or time criteria rather than engineering standards, reducing largely the advantages of the said manufacturing process. In order to overcome these obstacles, this research aims to propose a solution that permits to fabricate complex shapes with the desired winding angles at a certain region of complex-shaped mandrels. A numerical tool that simulates the placement of fiber tows over the surface of complex geometries is developed and validated by means of the fabrication of convex and concave composite structures using detachable mandrels. Previous results show that it is feasible to wind complex geometries with good accuracy.

scholarly journals Structure and Function in the Nematodes: Internal Pressure and Cuticular Structure in Ascaris

1957 ◽  
Vol 34 (1) ◽  
pp. 116-130 ◽  
Author(s):  
J. E. HARRIS ◽  
H. D. CROFTON
Keyword(s):  
Internal Pressure ◽  
Direct Method ◽  
Pressure Gauge ◽  
Longitudinal Axis ◽  
Mean Value ◽  
Mechanical Factors ◽  
And Function ◽  
Longitudinal Muscles ◽  
High Internal Pressure ◽  
A Direct Method

1. Experimental determinations of the hydrostatic pressure in the pseudocoel of living Ascaris lumbricoides were made by a direct method, using a glass helix pressure gauge and by an indirect method using an indentation gauge, both of which are described. 2. The mean value of this pressure was 70 mm. Hg (95 cm. of water), and showed wide and often rhythmical variations from 16 mm. to as high as 225 mm. Hg. Observations on the behaviour of artificially distended worms and of the tension developed by the muscles confirm these results. 3. The mechanical structure of the cuticle, with its inextensible spiral fibrils, forming a basketwork at an angle of 75° to the longitudinal axis, provides for an anisometric expansion and contraction under the action of the longitudinal muscles which is closely in accordance with the observed changes in volume and length. 4. A discussion of the significance of this mechanism and of the high internal pressure suggests that the great similarity of form among nematodes is determined to a considerable extent by mechanical factors.

On Determining Reference Stresses for High Temperature Thin/Thick Tube Bends

2005 ◽  
Author(s):  
Abheek Basu ◽  
Khosrow Zarrabi ◽  
Lawrence Ng
Keyword(s):  
High Temperature ◽  
Internal Pressure ◽  
Explicit Expression ◽  
Finite Volume ◽  
Limit Analysis ◽  
Volume Analysis ◽  
Reference Stress ◽  
First Time

It is well known that tube/pipe bends have some degree of ovality caused during their manufacture. For the first time, based on limit analysis, the authors previously presented an explicit expression for calculation of the reference stress of tube/pipe bends with varying degrees of ovality that are subjected to uniform internal pressure. The present paper assesses this expression using an elastic-creep finite volume analysis. This is due to availability of an in-house finite volume code. It is shown that the references stresses predicted by proposed expression correlate well with those computed using elastic-creep analyses for tube/pipe bends with various degrees of ovality.

scholarly journals Self-assembled nanocapsules in water: a molecular mechanistic study

2017 ◽  
Vol 19 (31) ◽  
pp. 20377-20382
Author(s):  
Hang Xiao ◽  
Xiaoyang Shi ◽  
Xi Chen
Keyword(s):  
Carbon Nanotubes ◽  
Drug Delivery ◽  
Internal Pressure ◽  
Mechanistic Study ◽  
Potential Applications ◽  
Self Assembled ◽  
High Internal Pressure ◽  
Very High

One-end-open carbon nanotubes with an appropriate radius difference can coaxially self-assemble into a nanocapsule with very high internal pressure (on the order of 1 GPa), underpinning potential applications in nano-reactors, drug-delivery, etc.

The Effect of a Discontinuous Welding Technique on Stress Levels of a Hot Tap Tee

2004 ◽  
Author(s):  
X. L. Xue ◽  
Z. F. Sang ◽  
W. Z. Jiang
Keyword(s):  
High Temperature ◽  
Internal Pressure ◽  
Stress Level ◽  
Heat Treating ◽  
Structure Study ◽  
Economic Losses ◽  
Radial Deformation ◽  
Test Model ◽  
Operating Pressure ◽  
Metallurgical Structure

With the development of petrochemical industry, the hot tapping technology has been widely used. A hot tapping is a technique that allows establishing a branch connection to a live pipeline. As it is a technology without halting transportation, it can avoid large economic losses and serious air pollution. When an operation of hot tapping is performed, a technology of discontinuous welding is sometimes used to reduce the localized high temperature that may cause burn-through of pipe. The purpose of this paper is to investigate whether the structure fabricated by discontinuous welding can work safely. Simulation of discontinuous welding was conducted to compare the temperature and stress distribution between continuous and discontinuous welding. It can be concluded that the temporary high temperature can be reduced effectively by discontinuous welding. However, due to frequent arc starting, a larger residual stress is resulted in. The stress level under internal pressure was studied by experiment using stress-gauging method. And the internal pressure was imposed by a high-lift pump. The failure load of the test model was 24.0MPa. Finite element simulation was also conducted to study the stress level under internal pressure. Then a comparison between experimental and FEA results was made. The experimental and FEA results indicate that the maximal stress occurs at the intersection area of the branch and run pipe. And it also can be seen that the results of radial deformation in the cross section are in good agreement. The metallurgical structure study shows that the welding and heat-treating procedures were proper. It can be concluded from this study that although the stress level is high under operating pressure, the structure can undergo the operating pressure safely.

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