جریان آب

آب تشکیل شده از دو گاز هیدروژن و اکسیژن به نسبت دو ملکول هیدروژن و یک ملکول اکسیژن (H2O). در سیستم انگلیسی آب در فشار جو در دمای ۲۱۲ درجه فارنهایت به جوش می آید و در دمای ۳۲ درجه فارنهایت یخ میزند. بیشترین وزن مخصوص در دمای ۳۹٫۱ درجه فارنهایت به ازای هر فوت مکعب ۶۲٫۴۲۵ پوند(LP) میباشد. (یک پوند=۴۵۳٫۵g  گرم) .درسیستم متریک آب تحت فشار جو در دمای ۱۰۰ درجه سانتی گراد بجوش می آید. و در دمای صفر درجه سانتی گراد یخ میزند. وزن مخصوص یک لیتر آب یک کیلوگرم است. در حالیکه یک لیتر یک دسیمتر مکعب میباشد. در سیستم متریک فشار برحسب پاسگال (Pa) که معادل یک نیوتن بر مترمربع است. در دماهای بالاتر فشار کمی افت میکند. فشارپذیری آب محدود است. این محدودیت به حدی است که در عمق یک مایلی (یک مایل=۱۶۰۹٫۳۴ متر) وزن یک فوت مکعب آب که در سطح ۶۲٫۴۲۵ پوند بود فقط نیم پوند بیشتر است. حاصل تمام فرمولهایی که برای اندازه گیری مقدار جریان آب از یک مجرای در زمان داده شده بکار گرفته میشوند, تقریبی بوده. فرمول زیر مقدار جریان در یک شبکه با شرایط عادی را با %۵ تا %۱۰ تقریب نشان می دهد

                                                                                                                                                                                                                      مقدار تقریبی سرعت (فوت برثانیه)  =  V

 ضریب استخراج شده ازتابلوی زیر  =  C

قطرلوله(برحسب فوت)         =  D

  هد لوله(برحسب فوت)    =  h

 طول لوله(برحسب فوت)   = L

C  جدول مقدار ضریب

مثال: یک شبکه انتقال به طول یک مایل و قطر ۱۲ اینچ آب را با هد ۱۰۰ فوت تخلیه میکند.سرعت و مقدار آب تخلیه شده را در ثانیه محاسبه کنید با استفاده از جدول فوق مقدارضریب برای لوله ای با قطر ۱۲ اینچ(یک فوت)۴۸ میباشد

برای محاسبه حجم آب تخلیه شده در ثانیه برحسب فوت مکعب کافیست سرعت بدست آمده فوق را در سطح لوله(فوت مربع) ضرب نمایید

( فوت مکعب بر ثانیه )   ۵٫۱۶ = ۶٫۵۷ * ۰٫۷۸۵۴

Lubricants and Lubrication

A lubricant is used for one or more of the following purposes: 1.To reduce friction: 2.To prevent wear: 3.To prevent adhesion: 4.To aid in distributing the load: 5.To cool the moving elements: and 6.To prevent corrosion.

The range of materials used as lubricants has been greatly broadened over the years so that in addition to oils and greases many plastics and solids and even gases are now being applied in this role .

The only limitations on many of these materials are their ability to replenish themselves , to dissipate frictional heat ,their reaction to high environmental temperatures ,and their stability in combined environments.

Because of the wide selection of lubricating materials available , great care is advisable in choosing the material and the method of application .   The following types of lubricants are available: 1.petroleum fluids: 2.synthetic fluids: 3.greases: 4.solid films : 5.working fluids: 6.gases: 7.plastics: 8.animal fat: 9.metallic and mineral films: and 10.vegetable oils.

Pinch valve made by AHANGARY in China is a new type of valve with unique structure. It is very popular because of its excellent wear resistance and corrosion resistance. It is suitable for the transportation control of granular slurry or chemical medium in various pressure pipelines system.

Basic Character:

1. Scope of application: Chemical industry, petroleum, power generation, alkali plant, mineral processing, cement coal preparation, non-metallic industries. It can quickly control or cut-off sand flow pipeline.
2. Applicable media: pulp, sewage, slag, cinder, sediment and so on.
3. Applicable temperature: -30-120, higher temperature customized.
4. Pressure range: -0.3-2.5 Mpa (order description).
5. Driving mode: manual, electric and pneumatic.
6. Valve body material; Gray cast iron, Aluminum alloy, Carbon steel.

Why Choose Pinch Valve?

1. Multipurpose: pinch valve can replace gate valve, globe valve, regulating valve and so on.
2. Wear resistance and corrosion resistance: Rubber is much more wear-resistant than steel, iron and other metal materials. And the formulation can be adjusted to resist the corrosion of various chemical solvents. So it is especially suitable for the pipeline transportation control of granular slurry and chemical medium.
3. Good Seal ability: Rubber flanges are installed at both ends of the hose. When the valve is connected with the pipeline, no additional sealing gasket is needed, thus eliminating the bad phenomena of running, running, dropping and leakage.
4. Resistance low-temperature: Because the fluid medium flows in the elastic rubber tube, the harmful effects such as freezing crack of the shell caused by the fluid crystallization are eliminated.
5. Cost effective: Simple and flexible operation, easy maintenance, as long as the rubber hose is replaced during maintenance, the valve body and other mechanisms can be used for a long time, thus improving the service life of the valve, greatly saving the production cost of users, in line with value engineering.
6. Simple Structure: Pinch valve has simple structure and is the only leak-free valve in China. It can withstand all kinds of medium concentration of acid and alkali salts, and can transport pulp, dry and wet powder and crystalline medium. The inner lining of rubber pipes with different rubber formulations can be selected for different media to meet the production needs of different users.

How to choose Pinch valve rubble?

• Acid and alkali resistant rubber is used in power plants and chemical plants
• Mines (coal mines, iron ores, gold mines, non-ferrous metals, etc.) have large particles and strong impact. Natural rubber or blends with strong wear resistance are used.
• Oil-resistant rubber is used when oil content is high.
• HD40:95% pure natural rubber is prepared by liquid phase process with fresh latex. Excellent wet wear resistance, super elongation, high resilience and tensile strength. (For small particles)
• HD60: Silicon reinforced natural rubber, with wear resistance, high resilience, cutting resistance, tear resistance, and other properties. (For large particles)
• HDGJ: Silicon-based filling reinforced NBR. With wear resistance, oil resistance, aging resistance, fatigue resistance, good air tightness and other properties.
• HDTRJ: Carbon black/silica reinforced natural/synthetic rubber, hardness 60-70 IRHD. With wear resistance, high resilience, cutting resistance, tear resistance, impact resistance and other properties.
• HDDJ: Halogenated butyl rubber. Acid and alkali resistance, good air tightness, high temperature resistance.
• HDFG: Natural rubber, FDA certification, suitable for long-term contact with food use. HDOZ: 95% natural rubber, excellent wear resistance, ultraviolet and ozone resistance
• For more information of pinch valve please contact Resta China

Water Pressures : Water is composed of two gases , hydrogen and oxygen , in the ratio of two volumes of the former to one of the latter .

In the English System of measure , water boils under atmospheric pressure at 212 degrees F . and freezes at 32 degrees F.

Its greatest density is 62.425 pounds per cubic foot , at 39.1  degrees F . In metric SI measure water boils under atmospheric pressure at 100 degrees C (Celsius) and freezes at 0 degrees C . Its density is equal to one kilogram per liter , where one liter is one cubic decimeter.also in metric SI , pressure is given in pascals (Pa) or the equivalent Newton per square meter .

For higher temperatures , the pressure slightly decreases in the proportion weight of water per cubic foot at different temperatures.

The pressure per square inch is equal in all directions , downwards , upwards and sideways. Water can be compressed only in a very slight degree , the compressibility being so slight that even at the depth of a mile , a cubic foot of water weighs only about one – half pound more than at the surface .

The amount of water that will flow through a pipe in a given time are approximate . The formula below will give results within 5 or 10 per cent of actual results , if applied to pipe lines carefully laid and in a fair condition.

In which :

V = approximate mean velocity in feet per second ,

C = coefficient from the accompanying table ,

D = diameter of pipe in feet ,

h =  total head in feet ,

L = total length of pipe line in feet.

Example : A pipe line 1 mile longs , 12 inches in diameter , discharges water under a head of 100 feet . Find the velocity and quantity of discharge.

From the table , the coefficient C is found to be 48 for a pipe 1 foot in diameter ,

Hence :

To find the discharge in cubic feet per second , multiply the velocity found by the area of cross – section of the pie in square feet :