RU2278302C2 - Method of measurement of positive suction head of pump - Google Patents

Abstract

FIELD: measurement of positive suction head of pumps handling hydrocarbon mixtures.

SUBSTANCE: proposed method includes placing the flask filled with fluid to be handled in pipe line in front of pump ensuring ratio of vapor and liquid phases in flask equal to or close to ratio of phases in flow section of pump cavitation zone. Ratio of vapor and liquid phases in flask and cavitation zone is set taking into account thermal and physical properties of liquid; pressure difference at pump inlet and flask inlet is measured with the aid of differential pressure gauge. Adequate ratio of vapor and liquid phases in flask and in cavitation zone is set by means of design formulae.

EFFECT: enhanced efficiency due to taking into account physical and thermo-dynamic properties of hydrocarbon material of varying composition.

1 dwg

Description

The invention relates to a pump engineering industry, in particular for measuring the cavitation reserve of a pump pumping a hydrocarbon mixture.

It is known that the condition for reliable operation of the pump is the absence of cavitation. For this, it is necessary to maintain at the pump inlet a certain excess pressure above the vapor pressure of the pumped liquid.

A technical solution is known for measuring the cavitation reserve of a pump (see Bukrinsky AM, Modnikova VV. A device for measuring the cavitation reserve of circulation pumps // Energomashinostroyenie. - 1968. - No. 8. - P.36-43), including spray can 1, pipeline 2, differential pressure gauge 3 and impulse tubes 4.

However, the known technical solution when measuring the cavitation stock of the pump does not take into account the thermophysical properties of the pumped hydrocarbon mixture.

Closest to the invention is a method for measuring the cavitation reserve of a pump pumping a hydrocarbon mixture, which consists in placing a canister in the pipeline in front of the pump, which is pre-filled with the pumped liquid, providing a ratio of vapor and liquid phases in the cavity of the can equal to or close to the phase ratio in flow part of the cavitation zone of the pump, while the ratio of vapor and liquid phases in the can and cavitation zone is established taking into account the thermophysical properties of the liquid ti is measured and a differential pressure gauge differential pressure across the pump inlet and into the cartridge (SU 1054573 A, Institute of Nuclear Energy BSSR, 15.11.1983).

However, the known method cannot be effectively used when measuring the cavitation stock of a pump pumping a hydrocarbon mixture of variable component composition.

The objective of the invention is to increase the efficiency of the method by taking into account the physical and thermodynamic properties of the pumped hydrocarbon mixture of variable component composition.

The technical result is achieved by the fact that in the method for measuring the cavitation stock of a pump pumping a hydrocarbon mixture, which consists in the fact that a canister is placed in the pipeline in front of the pump, which is pre-filled with the pumped liquid, providing a ratio of vapor and liquid phases in the can cavity equal to or close to the phase ratio in the flow part of the cavitation zone of the pump, while the ratio of the vapor and liquid phases in the can and cavitation zone is established taking into account the thermophysical properties of fluids and measure by differential pressure gauge the pressure drop at the inlet to the pump and to the canister, according to the invention, an adequate ratio of vapor and liquid phases in the can and cavitation zone is established using the formula

for the area

and

for the area

,

,

- критерии тепловой кавитации,

;Where

- criteria for thermal cavitation,

;

g is the acceleration of gravity, m / s ² ;

ρ is the density of the liquid, kg / m ³ ;

with _p - specific heat of the liquid, J / kg · K;

r is the latent heat of vaporization, J / kg;

- наклон кривой насыщения, К/Па;

- slope of the saturation curve, K / Pa;

V _p , V _W - respectively, the specific volume of steam and liquid.

The drawing shows a General view of a device for measuring the cavitation stock of a pump in which the described method can be implemented.

The device comprises a can 1, pipeline 2, differential pressure gauge 3, impulse tubes 4 and valves 5 and 6.

The implementation of the method is as follows.

Spray can 1 is installed in the suction pipe of the pump in a vertical position. Spray can 1 is prepared for operation: valves 5 and 6 are opened, spray 1 is blown with pumped liquid into the atmosphere until the air is completely removed. After that, valve 6 closes, and then valve 5. Through valve 6, part of the liquid is removed from the can 1 to form a controlled vapor space. In the inner cavity of the can 1, a pressure is set equal to the vapor pressure at a given ratio of vapor and liquid phases and the temperature of the liquid at the pump inlet. The differential pressure measured by a differential pressure gauge 3 connected to the pipeline and the can is the excess pressure - a cavitation reserve that must be controlled to avoid pump cavitation.

The given ratio is determined by the above formulas. The control of the steam space is carried out by measuring the volume of liquid removed from the can 1.

Using the proposed method will allow you to measure the cavitation stock of the pump, taking into account the thermophysical properties of the liquid with a variable component composition.

Claims (1)

A method for measuring the cavitational reserve of a pump pumping a hydrocarbon mixture, which consists in placing a canister in the pipeline in front of the pump, which is pre-filled with the pumped liquid, providing a ratio of vapor and liquid phases in the can cavity equal to or close to the phase ratio in the flowing part of the pump cavitation zone while the ratio of vapor and liquid phases in the can and cavitation zone is established taking into account the thermophysical properties of the liquid and measured by a differential pressure gauge ohm differential pressure at the inlet to the pump and to the canister, characterized in that an adequate ratio of vapor and liquid phases in the can and cavitation zone is established using the formula

for the area

and

for the area

, Where

- criteria for thermal cavitation,

; g is the acceleration of gravity, m / s ² ; ρ is the density of the liquid, kg / m ³ ; with _p - specific heat of the liquid, J / kg · K; r is the latent heat of vaporization, J / kg;

- slope of the saturation curve, K / Pa; V _p , V _W - respectively, the specific volume of steam and liquid.