Instant knowledge: A case for steam

A better understanding of the properties of steam may be achieved by understanding the general molecular and atomic structure of matter, and applying this knowledge to ice, water and steam.

09/16/2013


What is steam?

A better understanding of the properties of steam may be achieved by understanding the general molecular and atomic structure of matter, and applying this knowledge to ice, water and steam.

The specific combination of these atomic elements provides compound substances. One compound is represented by the chemical formula H2O, having molecules made up of two atoms of hydrogen and one atom of oxygen.

The reason water is so plentiful on the earth is because hydrogen and oxygen are among the most abundant elements in the universe. Carbon is another element of significant abundance, and is a key component in all organic matter.

Most mineral substances can exist in the three physical states (solid, liquid and vapor) which are referred to as phases. In the case of H2O, the term ice, water and steam are used to denote the three phases respectively.

The molecular structure of ice, water and steam is still not fully understood, but it is convenient to consider the molecules as bonded together by electrical charges (referred to as the hydrogen bond). The degree of excitation of the molecules determines the physical state (or phase) of the substance.

Triple point

All the three phases of a particular substance can only coexist in equilibrium at a certain temperature and pressure, and this is known as its triple point.

The triple point of H2O, where the three phases of ice, water and steam are in equilibrium, occurs at a temperature of 32 F and an absolute pressure of 0.088 psi. This pressure is very close to a perfect vacuum. If the pressure is reduced further at this temperature, the ice, instead of melting, sublimates directly into steam.

Ice

In ice, the molecules are locked together in an orderly lattice type structure and can only vibrate. In the solid phase, the movement of molecules in the lattice is a vibration about a mean bonded position where the molecules are less than one molecular diameter apart.

The continued addition of heat causes the vibration to increase to such an extent that some molecules will eventually break away from their neighbors, and the solid starts to melt to liquid state. At atmospheric pressure, melting occurs at 32 F. Changes in pressure have very little effects on the melting temperature, and for most practical purposes, 32 F can be taken as the melting point. However, it has been shown that the melting point of ice falls by 0.01 F for each additional atmosphere of pressure. For example, a pressure of 200 psig would be needed to reduce the melting temperature by 0.18 F.

Content provided by Spirax Sarco, originally published in Steam News Magazine.



No comments
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2015 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
Hannover Messe 2016: Taking hold of the future - Partner Country status spotlights U.S. manufacturing; Honoring manufacturing excellence: The 2015 Product of the Year Winners
Inside IIoT: How technology, strategy can improve your operation; Dry media or web scrubber?; Six steps to design a PM program
World-class manufacturing: A recipe for success: Finding the right mix for a salad dressing line; 2015 Salary Survey: Manufacturing slump dims enthusiasm
Getting to the bottom of subsea repairs: Older pipelines need more attention, and operators need a repair strategy; OTC preview; Offshore production difficult - and crucial
Digital oilfields: Integrated HMI/SCADA systems enable smarter data acquisition; Real-world impact of simulation; Electric actuator technology prospers in production fields
Special report: U.S. natural gas; LNG transport technologies evolve to meet market demand; Understanding new methane regulations; Predictive maintenance for gas pipeline compressors
Warehouse winter comfort: The HTHV solution; Cooling with natural gas; Plastics industry booming
Managing automation upgrades, retrofits; Making technical, business sense; Ensuring network cyber security
Designing generator systems; Using online commissioning tools; Selective coordination best practices

Annual Salary Survey

Before the calendar turned, 2016 already had the makings of a pivotal year for manufacturing, and for the world.

There were the big events for the year, including the United States as Partner Country at Hannover Messe in April and the 2016 International Manufacturing Technology Show in Chicago in September. There's also the matter of the U.S. presidential elections in November, which promise to shape policy in manufacturing for years to come.

But the year started with global economic turmoil, as a slowdown in Chinese manufacturing triggered a worldwide stock hiccup that sent values plummeting. The continued plunge in world oil prices has resulted in a slowdown in exploration and, by extension, the manufacture of exploration equipment.

Read more: 2015 Salary Survey

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.
This article collection contains several articles on the vital role that compressed air plays in manufacturing plants.
This article collection contains several articles on the Industrial Internet of Things (IIoT) and how it is transforming manufacturing.
click me