The importance of the valves
Valves are found in virtually every industrial process, including water and sewage processing, mining, power generation, processing of oil, gas and petroleum, food manufacturing, chemical and plastic manufacturing and many other fields.
People in developed nations use valves in their daily lives, including plumbing valves, such as taps for tap water, gas control valves on cookers, small valves fitted to washing machines and dishwashers, safety devices fitted to hot water systems, and poppet valves in car engines.
In nature there are valves, for example one-way valves in veins controlling the blood circulation, and heart valves controlling the flow of blood in the chambers of the heart and maintaining the correct pumping action.
Valves may be operated manually, either by a handle, lever, pedal or wheel. Valves may also be automatic, driven by changes in pressure, temperature, or flow. These changes may act upon a diaphragm or a piston which in turn activates the valve, examples of this type of valve found commonly are safety valves fitted to hot water systems or boilers.
More complex control systems using valves requiring automatic control based on an external input (i.e., regulating flow through a pipe to a changing set point) require an actuator. An actuator will stroke the valve depending on its input and set-up, allowing the valve to be positioned accurately, and allowing control over a variety of requirements.
Źródło: https://en.wikipedia.org/wiki/Valve
What do the plumbing work?
Hydraulics is quite a complex area and not everyone can be found in it. In such matters require specialized knowledge and skills, and such work is also associated with great responsibility, because the slightest error can result in a major accident. Plumbing may involve many issues. Sometimes it will be installation of hydraulic, other times repairing the broken pipe or replace gaskets and scope of such work is very extensive. Specialists in the field of hydraulics are needed in each region, because each building are installed plumbing. So it is very important work, without which it would be hard for us to get around.
Wikipedia - plumbing standards and regulations
Much of the plumbing work in populated areas is regulated by government or quasi-government agencies due to the direct impact on the public's health, safety, and welfare. Plumbing installation and repair work on residences and other buildings generally must be done according to plumbing and building codes to protect the inhabitants of the buildings and to ensure safe, quality construction to future buyers. If permits are required for work, plumbing contractors typically secure them from the authorities on behalf of home or building owners.
In the United Kingdom the professional body is the Chartered Institute of Plumbing and Heating Engineering (educational charity status) and it is true that the trade still remains virtually ungoverned; there are no systems in place to monitor or control the activities of unqualified plumbers or those home owners who choose to undertake installation and maintenance works themselves, despite the health and safety issues which arise from such works when they are undertaken incorrectly; see Health Aspects of Plumbing (HAP) published jointly by the World Health Organization (WHO) and the World Plumbing Council (WPC). WPC has subsequently appointed a representative to the World Health Organization to take forward various projects related to Health Aspects of Plumbing.
In the United States, plumbing codes and licensing are generally controlled by state and local governments. At the national level, the Environmental Protection Agency has set guidelines about what constitutes lead-free plumbing fittings and pipes, in order to comply with the Safe Drinking Water Act.
Some widely used Standards in the United States are:
ASME A112.6.3 ? Floor and Trench Drains
ASME A112.6.4 ? Roof, Deck, and Balcony Drains
ASME A112.18.1/CSA B125.1 ? Plumbing Supply Fittings
ASME A112.19.1/CSA B45.2 ? Enameled Cast Iron and Enameled Steel Plumbing Fixtures
ASME A112.19.2/CSA B45.1 ? Ceramic Plumbing Fixtures
Źródło: https://en.wikipedia.org/wiki/Plumbing