Back to Basics: An Overview of Plumbing Engineering瘦的英语怎么读
By John Swaffieldfestival walk
准备 英文Any overview must be personal. In this ca, the perspective is bad on 25 years of exposure to the whole gamut of plumbing issues from application of mathematical simulations to the efforts necessary to bring water supply to the less privileged areas of developing countries; from the investigation of venting problems in underground structures to the political and business issues inherent in the manner in which codes and regulations are specified.
界面英文This perspective leads to caution in addressing the title “Back to Basics.” In the U.K., and probably other western democracies, this phra reprents the graveyard of many political aspirations. The first step in this overview therefore is to define “basics” and probably more importantly to determine what is not included under this heading.
The fundamental requirement of a plumbing system, including both water supply and drainage, is that it does no harm. The public health imperative is supreme. This is often encapsulated within codes through an apparent obssion with such issues as back-siphonage. Drainage systems must carry away waste without posing a hazard to the ur or providing any long term hazard within the areas thro
ugh which the drainage system pass. Habitable space must be protected from the incursion of foul odor through the provision of venting systems. The requirements are basic and form, in the U.K. at least, the backbone of the Victorian drainage and vent systems installed from the 1880s and which became the precursor of similar systems within the developing Western world at that time.
In the U.K. in the mid 19th century Chadwick and other social reformers introduced many of the urban water supply and drainage system techniques now taken for granted––effectively the Industrial Revolution spawned both the problem and the socially aware groups that would provide its solution. To the requirements must now also be added the need to conrve water, not only as an economic and political imperative, but also to meet the demands being placed on water supply systems by increas in population, particularly in the cities of the developing world, and the rising expectations of tho fortunate to live in developed cities.
What’s Not Included
So much for the definition of “basics.” The cons ideration of what should not be included within this title is more controversial. “Back to basics” does not mean a return to some golden age when rule of thumb was supreme, when venting was so excessive that traps never oscillated and flush volumes s
o great that imperfections in system design and installation went unnoticed, and each community applied its own codes and standards developed from limited experimentation and obrvation, unsubstantiated by any degree of engineering analysis or rigor. In the U.S. the design of water supply and drainage systems may be traced back to the fundamental work of Hunter.
However, Hunter recognized in his definitive 1940 paper that the solutions he propod were limited by the analysis techniques available to him. Referring to the design of building drainage systems he obrved that “...the conventional pipe formulae apply to the irregular and intermittent flows that occur in plumbing systems only during that time (usually very short) and that ction of pipe in which the variable factors involved (velocity or volume rate of flow or hydraulic gradient and hydraulic radius) are constant.”
Hunter recognized that the basic physics underlying water supply and drainage, and, in particular, drainage, as this arm of the subject offers particular challenges to the analysis due to the free surface nature of the flow, which may also be multi-pha due to the transport of solid material and the possibility of entrained air, is identical in Seattle and Sydney, Hoboken and Helsinki or even Albuquerque and Auchtermuchty. Yet each of the states or nations reprented in this list has its own code or standard. The European Community has struggled for nearly 20 years to generate a commo
n plumbing code––unsuccessfully.
Thus, the predominant issue for plumbing engineering at the end of the 20th century has to do with education––the need to stress that physics defines operation and mathematical simulations can function without rule of thumb overrides. Water Conrvation
职称英语合格标准Water conrvation offers an example for the interaction between practitioners and tho involved in developing both products and system design simulation process. A review of the water usage within developed countries indicates surprising similarities in the percentage u of domestic water for a whole range of common requirements––approximately 30 to 40% of the drinking-quality water is ud to flush toilets. Similar figures are found in toilet and urinal usage in commercial buildings. Careful monitoring of usage has provided this data, and to introduce effective water conrvation measures it is imperative that water clot flush volumes decrea.
This has been a continuing thrust for the whole of this century, a century which opened with a disagreement between the London Metropolitan Water Board and the ceramic industry over the 10.5 gallons propod for water clot flushing and clod with arguments in similar arenas as to the acceptability of 1.6 gallons for flushing devices. Similarly, the century opened in the U.K. with the Inst
itute of Health in London proposing a drain line carry test using half-inch diameter balls and clod with an extremely similar test probably facing demi within the U.S. water clot. Reducing water clot flush volume is imperative. Good design can deliver. The introduction of dual flush (i.e., a lower flush volume for urine removal, particularly significant in commercial buildings with a high female population), offers further opportunities for conrvation. Dual flush was first introduced to the U.K. in the 1980s, where it was unsuccessful due to a lack of clarity in operation. It will be reintroduced in the 1999 Water Regulations, encouraged to a large extent by the successful u of 1.6 and 0.8 gallon dual flush in Australia. The introduction of
non-siphonic flushing devices within the U.K. Water Regulations from January 1,
2001, will allow a simpler and unambiguous two-button mechanism which will ensure that the system in understood by all urs.
Drainage Systems
会计电算化软件However, there is a need to recognize that drainage networks are a system. Alteration to one element in isolation may lead to possible problems. There is a need to recognize that reducing flush volume should be accompanied by possible reductions in drainage diameters, particularly for isolate
d water clots or increas in slope. Similarly, the decay of the flush wave needs to be recognized and modeled. Hunter recognized the importance of wave attenuation but was unable to model it due to the lack of computing power in the 1940s. The modeling method to ensure that the considerations are fully investigated at both the code and design stage exists, developed initially through initiatives at National Bureau of Standards, now NIST, and propagated in the U.S. through ASPE conferences over the past 10 years. Similarly, water clot design can, and will, benefit from the introduction of modern technology. The application of computational fluid dynamics to the flow regime within water clots has already been demonstrated by such industrial organizations as Toto in Japan. While there is a need to approach with caution the boundary conditions which must determine the accuracy of any such CFD model, the introduction of such models is a major step forward in the development of water clots.
Mathematical simulations can inform the designer when the item is acceptable. Mathematical models can provide the targets to which design should aspire or confirm the appropriateness of a given t of performance code criteria. This approach would bring the plumbing engineering industry in its broader n in line with tho other industries which depend on a fundamental understanding of fluid mechanics.
Thus, this overview of plumbing engineering stress the importance of water conrvation and highlights its growing importance in the coming century. There will be a need for the developed world to reduce its usage of water while at the same time being able to provide low water u solutions to tho countries still developing and who cities are verely taxed by the overu of water for purpos that could be achieved at lower cost.
In defining the basics of drainage design, the prevention of odor ingress was highlighted. The Victorian concept that smell equalled dia led to extremely complicated venting systems, known in the U.K. as two-pipe networks where each individual appliance was parately vented to a vent stack and black and grey water were parately taken away from the building through two vertical wet stacks. The development in the 1930s of the one pipe system in the U.S. and, in particular, the introduction of the single stack system in the U.K. from the 1950s on, led to considerable savings in terms of the cost of plumbing installations. In the U.K. in the 1950s such reductions were important in the post-war housing rebuilding process. However venting systems are still over-provided.
Modern technology allows the analysis of vent system operation and allows the阿根廷 英文
identification of means by which pressure excursions may be limited. The introduction of pressure rel
ief valves or air admittance valves and the opportunity for distributed venting up the whole height of a multi-story building offers tremendous advantages and savings for vented system design. In the U.K. the development of waterless trap als that also act as air admittance valves provide exciting possibilities for system designers in the future. In this context “back to basics” does not mean adhering to complicated vent systems when modern technology could offer simpler and more elegant design opportunities.
In the area of rainwater drainage, which varies considerably due to geographic location, similar advantages may now obtained through the introduction of systems relying on a fundamental understanding of system flow. Siphonic rainwater systems applied to large buildings, such as airports and retail outlets, offer tremendous cost advantages, at the expen of ensuring that the mechanisms necessary are fully understood.
Siphonic rainwater systems require that the rainwater pipes run full, creating sub-atmospheric pressures to increa the drainage rate from the roof during design rain storms. System design is related to the design storm and the must be matched. Over-provision in the drainage system will lead to under usage as the design storm may not occur for veral hundred years. Under-design of the network may lead to excessive suction pressures as the design storm may occur and be exceedgoogle网页翻译工具
ed on many occasions.
The siphonic nature of the system means that pipework is depressurized and there is a possibility of system collap under particular flow conditions––flow conditions that can be properly analyzed and predicted so that the dangers can be minimized. The innovations emphasize the need for plumbing engineers to fully understand the fluid mechanics of their subject area and confirm that designers and code specifiers understand that rule of thumb safety factors may, in drainage systems, lead to failure, rather than safety.
Water Reu
Water conrvation may be viewed as a source of new supply. One of the most hopeful areas for development is in the reu of wastewater or the collection, or harvesting, of rainwater. In the U.K. this is an area being given considerable attention. However, there are legislative areas to be addresd concerning the quality of the collected water. While rainwater harvesting may be an attractive solution in some areas, as demonstrated at the AWWA Conrv99 conference, water quality must be suitable and there must be no possibility of cross contamination between the contributing water sources, e.g., water clot flushing where rainwater and reud bath or sink water
could be collected together in one holding tank also provided with a mains top up supply. There may have to be treatment if water resides within the system longer than the minimum period of time. Developments in on-line control, nsors and tariff structures will allow the benefits of water reu to be realized. Recurring Issues
A number of recurring issues are identified by this overview. First, the need to fully understand the fluid mechanics of plumbing system operation will require a shift in the way in which the industry responds to rearch. However, the rearch community must understand that its products must be made accessible and understandable to the industry its rves. Therefore, dialogue is necessary between the plumbing engineering industry and the rearch community that rves it.
Second, it is necessary to address the issue of code specification. All of the developed countries take codes forward in much the same way, by tting up committees which discuss and agree on code specifications. The committees are often dominated by interested parties and the input of fundamental engineering, or a full understanding of the fluid mechanics of the process, may be lost through a perceived need to protect industry from encroachment.
There is a need to reevaluate the manner in which codes are developed and it may be that code pro
posals should be subjected to theoretical analysis bad on system simulations before acceptance to highlight any unnecessary code restrictions. Traditionally, international codes are extremely difficult to generate. However, industry, particularly in the product area, is increasingly becoming international. The purcha of national ceramic manufacturers by overas bidders has led to a reduction in the overall number of organizations now producing ceramic sanitaryware in the developed world. While individual names may remain, companies have merged and are becoming large multi-national organizations. Codes should recognize this and should be written in the next century to allow freedom of trade.
No overview of plumbing engineering can avoid the problems of operative training. In the U.K. the traditional training routes for plumbers have been verely reduced. Similarly regulation and enforcement have been weakened in the 1980s and 1990s by privatization. Performance codes alone are insufficient if there is no degree of regulation and enforcement to ensure that installations are fit for purpo and meet the basic requirement that plumbing systems shall do no harm. It is likely that both of the issues will be addresd and that there will be a degree of reintroduction in the areas.
Advances in nsor technology applied to water u monitoring will allow water providers considerabappeal
konforle freedom to devi tariff structures to control water usage. Complex tariff structures will allow off peak water u and the introduction of a cost regime which will not penalize tho less able to pay. The are issues which the industry will have to address, although technically not engineering issues in the n of the title of this overview.
In conclusion, this overview has tried to identify the range of problems facing the plumbing engineering industry at the end of this century. The advances since 1900 have been considerable, not only in the obvious areas of materials but in the fundamental understanding of the fluid mechanisms of water supply and drainage. The integration of this understanding with the design process has changed the design and installation of building water supply and drainage and vent systems.
There has been a continuous process of water conrvation, particularly by reduction of water clot flush volumes, culminating in Scandinavian dual flush water clots
