Steam Bubble Cavitation

Understanding Corrosion: Cavitation

Cavitation is a fascinating yet destructive phenomenon that can have a profound impact on the integrity of materials, particularly in steam systems. This article delves into the world of cavitation and its role in pitting corrosion, shedding light on how it can lead to significant damage to steam heater tubes and piping systems. 

 

Cavitation occurs when steam bubbles rapidly collapse, generating an extraordinary amount of pressure on the adjacent material. This can result in the formation of pin-sized to larger holes, which can ultimately lead to the leaking of steam heater tubes. The process is driven by the collapse of steam bubbles, creating a highly localized and intense pressure that causes damage to the material's surface. 

Fig 1.- Tube Inside Cavitation | Motic Panthera SMZ171, Moticam 10 Stack

Image Credit: Willem Cramer

Cavitation erosion is closely linked to the behavior of flash steam in the system. Flash steam occupies a relatively large volume but rapidly condenses when it loses heat, which is transferred through the tube wall into the surrounding fluid. This sudden condensation of flash steam results in a significant change in volume. 

The specific volume differences between steam and condensate are key to understanding cavitation's destructive potential. When flash steam condenses, it creates a large void that is swiftly and often violently filled by adjacent condensate. This rapid filling of the void generates shock waves known as water hammer. 

Fig 2.- Tube Outside Cavitation | Motic Panthera SMZ171, Moticam 10 Stack

Image Credit: Willem Cramer

The rapid collapse of the flash volume and the associated shock, caused by high-velocity condensate filling the void, can have severe consequences. The force generated by water hammer and the erosion caused by the swift filling of voids can result in significant damage to piping systems. In conclusion, cavitation is a complex phenomenon with the potential for significant damage in steam systems. The rapid implosion of steam bubbles, driven by specific volume differences between steam and condensate, can lead to the formation of holes and result in pitting corrosion. Understanding the mechanics of cavitation is crucial for preventing and mitigating the destructive consequences it can have on steam heater tubes and piping systems.

© willemsmicroscope.com

What’s in a rat?

The role of rodents in biomedical research is invaluable. Rodents, such as mice and rats, are the most commonly used mammals in biomedical research because of their anatomical, physiological and genetic similarities to humans. 

Scientists are able to genetically adapt mice to study a disease, for example by removing certain genes or by inserting (human) genes that are at the basis of certain disorders. For example, breast cancer can be simulated in mice to study the mechanisms of cancer and to test treatments. Mice and rats are also often used in behavioral studies to test, for example, treatments for memory loss in dementia.

Rodents are used in countless research areas, from cancer to immune diseases, heart disease, hypertension, metabolic and hormonal disorders, diabetes, obesity, osteoporosis, glaucoma, blindness, deafness, psychiatric disorders such as depression and schizophrenia, and neurodegenerative disorders such as Alzheimer's disease, Parkinson's and ALS.

The images taken with the new Moticam S6 camera show a cross-section with details through the upper body of the rat, just above the splice of the trachea into the two bronchi. The beautiful coup shows the various body parts in this cross section, some of which are indicated below.

With thanks to Cees Koopman, veterinarian.

© willemsmicroscope.com

It grows on tree trunks

Dilated scalewort or Frullania dilatata grows mainly as a pioneer on trees with a moderately nutrient-rich bark. The species is somewhat drought-tolerant and can be found on free-standing trees, except in forests. Especially in full sun, the plants have their characteristic rust brown color. This moss experienced a decline in the last century due to air pollution, but is now common in almost all parts of The Netherlands. It is an attractive species, which is not easily overlooked in inventories. As a result, the distribution picture does suggest a greater number of occurrences than is actually the case: regularly there is only a single find per square section of land of 1 x 1 km.

© www.willemsmicroscope.com

Daphnia’s maneuvers in the dark

Like many other crustaceans, water fleas are very sensitive to light. They have a light-sensitive organ, also called Ocellus, with which they can swim in the direction of the light.

The yak keeps you warm and tidy in the winter

The yak is a bovine species, that lives amongst others in Tibet. They graze in the cool higher part of mountainous areas. Yaks are not adapted to living in hot climates. The main raw material produced by the yaks is wool, existing of tail hair and long hair along the yak belly. Yak shearing takes place in the spring, which is a difficult action because of the furious personality of this animal. 

Widespread

Bryum argenteum or Silver moss is perhaps the most widespread moss in the world, although in many regions it is found primarily in human settlements. It is prevalent in atmospherically polluted areas. It can be found in large cities on tarred roads, on concrete structures (e.g. between paving stones, at the bases of walls, on roofs and windowsills) on soil as well as in waste areas, but also in more natural habitats.

Purple Rain

On and around Mount Etna, Lapillo Vulcanico (Italian) is found all over the place. During explosive volcanic eruptions it falls like rain out of the sky over a wide spread area. The Lapillo Vulcanico from Mount Etna has a purplish color. It is present in thick layers on and around the volcano and can also be found, thinly spread over more remote areas.

Lapillo Vulcanico or Lapilli is a size classification term for tephra, which is material that falls out of the air during a volcanic eruption. Lapilli means "little stones" in Latin. By definition Lapilli range from 2 to 64 mm in diameter. A pyroclastic particle greater than 64 mm in diameter is known as a volcanic bomb when molten, or a volcanic block when solid. Pyroclastic material with particles less than 2 mm in diameter is referred to as volcanic ash. 

It is better not to have this on your skin

Carp Louse. This highly flattened fish parasite is covered with a back shield. At the bottom of the head, the first lower jaws are transformed into suction cups with which they attach to fish. The chest piece consists of only four segments, each of which carries a pair of split-leg shaped swim legs. The abdomen is little developed and not externally articulated.

A curious caterpillar in the moss

In The Netherlands there are many working groups that regularly make an inventory of the mosses present in nature. For this purpose, the natural landscape is divided into square sections of 1 x 1 km that are characterized by nationally determined coordinates. In such a section it is observed which kinds of mosses occur in it. Many mosses can be identified on the spot. Here, people often use a magnifying glass. Sometimes the determination has to be done at home with the help of a microscope. The results of such an inventory are centrally placed in the "NDFF Verspreidingsatlas" (distribution atlas): www.verspreidingsatlas.nl. This is a database that has been made possible by various nature organizations, with the aim of following the development of the mosses flora under the influence of the environment in the Netherlands.

Just a beautiful preparation

Here we see the images of a beautiful preparation made by Mike Smith. The cross section trough the ovary of Buddleia globosa shows many details. Note that the ovary (and later the seed capsule) is covered in tangled hairs (stellate-tomentose) and how the base of the style is also hairy. The second fluorescence image shows this in detail.

The horsetail – a widespread group of vascular plants with an interesting history

A great part of our fossil fuels is based on distant relatives from our present horsetails. During the Carboniferous, this group of plants attained almost worldwide distribution: arborescent lifeforms up to 30m. The decay of these trees under anaerobic conditions, later additionally under high pressure and high temperatures finally formed coal, still one basis of fossil energy.

Today the horsetails are worldwide in distribution except for parts of Australasia. In Middle Europe a plant height of 1m is remarkable.

The most conspicuous morphological feature of a horsetail is the segmentation of the shoot into nodes and internodes. This is why these plants are also called the “articulate”.

                                               Equisetum telmateia                       Equisetum telmateia (note the jointed stem)

Water worms

When searching for macro fauna in a small pool in the province of Limburg, The Netherlands, the worms on the video were found alongside many other organisms. These worms belong to the Oligochaeta, a subclass within the ringworm taxonomy. There are species that live in the soil on land and species that live in the water.

Oligochaeta are well-segmented worms and most have a large body cavity that is used as a hydro skeleton. Usually each segment has little bundles of chaeta or ‘bristles’ on the outside, The bundles can contain one to several hairs and contain muscles to pull them in and out of the body. This allows the worm to get a grip on the ground or mud while it nestles into it. When digging, the body moves peristaltically, alternately it contracts and stretches forward.

Ithytrichia lamellaris: ‘Not observed in a hundred years’

In a little stream in Limburg, the southernmost province in the Netherlands, an apparently unknown animal was unexpectedly found by members of the Macrofauna Workgroup Green Hearth Leudal. During the determination an animal with a very remarkable shape was noticed in a partly transparent tube, which was no larger than 4 mm. The segments of the abdomen of the animal were lobed like bellows of an accordion. In addition, there was a drop-shaped appendix on each lobe. This had to be something very special. Internet gave little to no result. Until an article with a photo attracted attention. In the photo you could see an animal that looked like the captured one. The headline: ‘Not observed in a hundred years’, indicated that something strange might have been caught?

Primitive, but unique

Ferns are perhaps very old plants, but they are unique in their kind. They already occur in several hundred million year old fossils. After all, it was the first plant with roots and a real vascular system. In this way the ferns managed to extract water from the ground and use it for their further development. Because of the branches of the vessels it was also possible to get the water into the tops of the feathers or leaves. Ferns do not carry flowers. They therefore do not propagate with seeds, caused by fertilization of pistils with pollen through bees, beetles, birds, wind or otherwise. 

It hides in moss and lichen

When studying moss and lichen under the microscope, you will discover that in addition to the beautiful pictures it produces, a lot of animal life crawls around in it. If you walk through nature and see the many types of moss and lichen, you actually do not realize that. This is perhaps due to the fact that the animals are hardly visible to the naked eye.

Spores

For some people moss is a green plague. For other people moss is of unprecedented beauty. The Netherlands has more than 600 species of moss. There is even a real red list of rare and endangered moss species. Moss is a spore plant. The sporangium grows into a thickening in which the spores are located. As soon as the spores are ripe, the thickening will lose its cap and the spores can be transported by the wind.

Silent flight

Why can an owl fly almost silently? The owl hunts at night and wants to make as little noise as possible in order not to frighten his prey.

Breathing under water

Breathing:

Gills are the respiratory organs of many aquatic animals. With fish, the gills are in a space behind the head. Fishes exchange gasses with water through the gills.

How do you look after four times shedding your skin

An adult female mosquito lays her eggs on the water surface. This can be in a ditch, in pools in the floodplains, in a pond or in the rain barrel. Each species has its own preference. The number of eggs that are laid is very different from species to species and can be up to 300 at a time. After a few days, the larvae crawl out of the egg. These larvae feed on algae, microbes and other substances in the water.

Prehistoric nail imprints

On the images, a hand formed pottery fragment from the Michelsberg culture, Middle Neolithic period(4300 - 3500 BC) is shown. The Michelsberg culture is responsible for some of the oldest types of pottery in Europe, which is seen as a typical element of this culture. This pottery is generally found on hilltops, giving the impression of the presence of former fortified settlements. This impression is reinforced by findings of many waste pits with very different content and interruptions in the trenches that are interpreted as gates.