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Description

... A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by mechanical action. Pumps can be classified into three major groups according to the method they use to move the fluid: direct lift, displacement, and gravity pumps.

Generally, a pump is a device which receives mechanical energy from an external source and transfers this energy to the fluid that passes through it. As a result, fluid energy increases after the device’s exhaust. In pumps, always the change in fluid energy could be observed by the change in fluid pressure. The pumps are used for fluid transfer to a certain height or transporting it in a piping or hydraulic system. In other words, pumps are used to move fluids from one point to another.

Oil spills penetrates into the structure of the soil and can have significant deleterious consequences for ecosystems. There are radical soil chemistry changes which can arise from the presence of many hazardous chemicals even at low concentration of the contaminant species. These changes can manifest in the alteration of metabolism of endemic microorganisms and arthropods resident in a given soil environment. The result can be virtual eradication of some of the primary food chain, which in turn could have major consequences for predator or consumer species.

All oil companies use pumps for oil transfer in different flow and pressures, but unfortunately in recent years due to heavy sanctions by the West countries against Iran, importing this type of pump is associated with many problems, so that frequent refreshes in supply tender of this type of pump has been observed, which in many cases it leads to face many obstacles. For example, this company (Saban Sanat Sepahan) which is a manufacturer of Mobile Oil Separator devices (MOS & MOT) in Iran, is faced with many problems in supplying of oil transfer pumps, which is the most important product in the supply procedure of this devices. In this regard, this company had to import 6 oil transfer pumps in the past 2 years (due to order from Aghajari and Gachsaran oil and gas companies), which was achieve with many difficulties.

According to the calculations shown in the following chapters, it is also clear that it reflects significant differences in financial perspective between domestic and foreign samples and it will significantly prevent the outflow of foreign exchange.

In terms of quality, according to many inspection which has been done by this company’s experts on oil transfer pumps in different parts of the country, this company has achieved to a good conclusion so that now working on completely different and new models are pending and it is hoped after manufacturing this type of pump, it could obtain the approval of the Bureau of Standards.

Here it is noteworthy that this type of pump has not been built in any part of the country and this company is the first company to design and construction of it.

Considering the foregoing, the company was inspired to make pride and self-sufficiency for the country by production of this type of pumps.

General Product Specification

... In the following, general description is given for the pumps.

Different types of pumps:

Pumps can be classified by their method of displacement into positive displacement pumps, impulse pumps, velocity pumps, gravity pumps, steam pumps and valveless pumps. There are two basic types of pumps: positive displacement and centrifugal. Although axial-flow pumps are frequently classified as a separate type, they have essentially the same operating principles as centrifugal pumps.

Positive displacement pump

... A positive displacement pump makes a fluid move by trapping a fixed amount and forcing (displacing) that trapped volume into the discharge pipe.

Some positive displacement pumps use an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pump as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses. The volume is constant through each cycle of operation.

Positive displacement pump behavior and safety

... Positive displacement pumps, unlike centrifugal or roto-dynamic pumps, theoretically can produce the same flow at a given speed (RPM) no matter what the discharge pressure. Thus, positive displacement pumps are constant flow machines. However, a slight increase in internal leakage as the pressure increases prevents a truly constant flow rate.

A positive displacement pump must not operate against a closed valve on the discharge side of the pump, because it has no shutoff head like centrifugal pumps. A positive displacement pump operating against a closed discharge valve continues to produce flow and the pressure in the discharge line increases until the line bursts, the pump is severely damaged, or both.

A relief or safety valve on the discharge side of the positive displacement pump is therefore necessary. The relief valve can be internal or external. The pump manufacturer normally has the option to supply internal relief or safety valves. The internal valve is usually only used as a safety precaution. An external relief valve in the discharge line, with a return line back to the suction line or supply tank provides increased safety.

Positive displacement types

A positive displacement pump can be further classified according to the mechanism used to move the fluid:

Rotary positive displacement pumps

These pumps move fluid using a rotating mechanism that creates a vacuum that captures and draws in the liquid

Advantages: Rotary pumps are very efficient because they naturally remove air from the lines, eliminating the need to bleed the air from the lines manually.

Drawbacks: The nature of the pump demands very close clearances between the rotating pump and the outer edge, making it rotate at a slow, steady speed. If rotary pumps are operated at high speeds, the fluids cause erosion, which eventually causes enlarged clearances that liquid can pass through, which reduces efficiency.

Rotary positive displacement pumps fall into three main types:

Reciprocating positive displacement pumps

Reciprocating pumps move the fluid using one or more oscillating pistons, plungers, or membranes (diaphragms), while valves restrict fluid motion to the desired direction.

Pumps in this category range from simplex, with one cylinder, to in some cases quad (four) cylinders, or more. Many reciprocating-type pumps are duplex (two) or triplex (three) cylinder. They can be either single-acting with suction during one direction of piston motion and discharge on the other, or double-acting with suction and discharge in both directions. The pumps can be powered manually, by air or steam, or by a belt driven by an engine. This type of pump was used extensively in the 19th century—in the early days of steam propulsion—as boiler feed water pumps. Now reciprocating pumps typically pump highly viscous fluids like concrete and heavy oils, and serve in special applications that demand low flow rates against high resistance. Reciprocating hand pumps were widely used to pump water from wells. Common bicycle pumps and foot pumps for inflation use reciprocating action.

These positive displacement pumps have an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pumps as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses. The volume is constant given each cycle of operation.

Typical reciprocating pumps are:

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