WO2010058411A1

WO2010058411A1 - Pressurised float

Info

Publication number: WO2010058411A1
Application number: PCT/IN2008/000782
Authority: WO
Inventors: Nalawade Abhijit Annasaheb; Joshi Milind Arvind
Original assignee: SPIRAX MARSHALL PVT Ltd
Current assignee: SPIRAX MARSHALL PVT Ltd
Priority date: 2008-11-20
Filing date: 2008-11-20
Publication date: 2010-05-27
Anticipated expiration: 2011-05-20

Abstract

A float (1 ) is proposed, which is filled with pressurised fluid to withstand high external pressure. The fluid comprises air, inert gas or a combination of water and inert gas. The float can be hermetically sealed or be provided with means to increase the mass of the fluid in the float.

Description

PRESSURISED FLOAT

FIELD OF THE INVENTION:

This invention relates to floats.

INTRODUCTION AND BACKGROUND:

Floats are elements used in the float type traps as well as pressure powered pumps and many other products / equipment (e.g. in vessels, tanks for level gauging). Floats have to work against their self weight and external pressure with the help of buoyant force. Float traps and the pressure powered pumps work (function) with the help of float.

The upward buoyant force of a float, floating in a liquid medium contained in a vessel, is used to overcome the self weight of the float to either open or close an orifice to control the level of the liquid in the vessel. As the liquid level in the tank goes down the float moves down due to self weight and the cyclic operation of closing and opening of orifice commences.

In many common applications like a water tank level controller valve or level indicator, the float operates in ambient pressure and temperature. But in cases like a steam trap or pressure pump the floats operate at high temperature and has to withstand the operating pressure of the tank or vessel. This internal pressure of the tank is applied as an external pressure on the float.

Floats are usually manufactured of low thickness materials to reduce their self weight as increase in the weight reduces the buoyant force of the float. At the same time in cases where the floats are subjected to high external pressure and temperature the thickness of the float material has to be sufficiently high to withstand the pressure at elevated temperatures.

For increasing the external pressure carrying capacity of the float, the thickness of the float can be increased. But the float will not work as a float, because its weight will increase and it ultimately starts sinking. So, there is a limit up to which the thickness of the walls of the float can be increased. But it is very important to provide internal strength to the float, because with the existing thickness of the float, the float can not sustain very high pressures at elevated temperature, as the material resistance capacity drastically goes down at higher temperatures.

The present invention envisages a method to increase the external pressure carrying capacity of the float.

OBJECTS OF THIS INVENTION:

One of the objects of this invention is to provide a float capable of withstanding high external pressure.

Yet another object of this invention is to provide a float capable of operating at high temperature.

Another object of this invention is to provide a float made of relatively thinner material capable of withstanding high external pressure and temperatures.

Another object of this invention is to provide a float having higher net buoyant force. SUMMARY OF THE INVENTION:

According to the present invention there is provided a float adapted to withstand high external pressure; said float filled with pressurised fluid. Typically, the fluid comprises air, an inert gas or a combination of water and an inert gas.

Typically, the float is hermetically sealed.

Typically, the mass of fluid in float is variable.

Typically, the float is provided with means to increase mass of fluid in the float.

This is done in accordance with this invention by filling the float with gas at higher pressure or filling the float with water or both. Inside water starts generating steam as the external high pressure and high temperature condensate comes in contact with float thus providing strength to float from inside. In case of a gas filled float, there will always be some pressure from inside & once the float comes in contact with high pressure & high temperature condensate & or steam, pressure inside will increase as per gas laws.

BRIEF DESCRIPTION OF THE DRAWINGS:

The invention will particularly be described with reference to the accompanying drawings, in which:

Figure 1 shows the force acting on a float;

Figure 2 shows arrangement for pressure testing of an internally pressurized float of this invention; and Figure 3 is graphical representation of the test result of an internally filled / pressurized float of this invention.

DETAILED DESCRIPTION OF THE DRAWINGS:

Referring to figure 1 a float (1) is subjected to

(i) an external pressure force (P) acting on the external surface of the float (ii) a buoyant force (B) acting vertically upward on the float and

(iii) self weight (W) acting vertically downward on the float.

Referring to figure 2, a float (2) partly filled with water is placed in a container (3) designed to withstand high pressure. The container (3) is also filled with water and heated externally with the help of a heater (H). The steam pressure generated within the container (3) is applied externally on the float (2). Pressure gauges Pl and P2 connected to the float and container measure the internal pressure and the external pressure of the float.

Figure 3 is a plot of the internal pressure and the external pressure of the float at various stages.

Following EXPERIMENTS were carried out:

A. Test on a float internally pressurised with Nitrogen gas

(I) A float was pressurized internally with Nitrogen gas up to 40 bar g. and placed in a test chamber filled with water and pressurised. The pressure of the chamber was gradually increased and the condition of the float was observed through a viewing port constantly. The test was carried out till the float collapsed due to the external pressure. (2) The test as above was conducted on a conventional un-pressurised float till it collapsed.

RESULTS:

(i) The regular float burst at 120 bar g on doing destructive hydro test.

(ii) The pressurised float burst at 160 bar g CONCLUSION: a) When internal pressure was provided by filling a pressurized gas, the external pressure carrying capacity of the float increased to the same extent as the internal pressure.

B) Test on a float partially filled with water

EXPERIMENTAL SET-UP:

The experimentation was done with filling the float internally with 20 grams of water. The float was placed in a container designed to withstand high pressure. The container was heated externally with the help of a heater. The container was also filled with water, so that the float start pressurizing externally first as the water starts generating steam pressure externally. Due to heat conduction, the water inside the float also starts generating steam pressure internally. The pressure gauges are arranged inside and outside of the float to measure the pressure. The readings were noted. The experimental set up is shown below:

The readings were noted for both Pl (pressure inside float) and P2 (pressure outside float in the container) as seen in figure 2 of the accompanying drawings.

The graph was plotted for understanding the response of the P2 with respect to Pl which is seen in figure 3 of the accompanying drawings. The graph shows that

1. There is no delay in generation of internal pressure with respect to the external pressure.

2. The water inside and outside the float follows saturated steam pressure line. The advantages of using the float in accordance with this invention are as follows:

1) There is increase in the strength of the float to carry high external pressure at elevated temperatures.

2) As the float is internally strengthened, there is reduction in the wall thickness of the float.

3) With reduction in the thickness of the float, there is net reduction in the weight of the float.

4) With less weight of the float, the total cost of the float is reduced.

5) Actual pressure acting on the float is the resultant of the internal and external pressure, which is less than the external pressure. Hence, the float can be manufactured from lower strength materials.

6) The cost of the lower strength material is normally lower than the high strength material, which ultimately reduces the cost of the float.

7) As the net weight of the float which is acting downward is reduced with reduction in the thickness of the float, there is scope of reducing the size of the float till the buoyant force is greater than the self weight. This reduction in the size of the float gives rise to the cost reduction. 8) With reduction in the float size, the trap (equipment) size can be reduced, which leads to cost reduction and space reduction.

9) Alternatively, with higher buoyant force for same size of the float, the orifice size can be increased in the float type traps. This helps in increasing the condensate discharge capacity (trap overall dimensions remaining same).

10) In case of a gas powered pump, with reduction in actual size of the float which acts as a dead volume, there is increase in the discharge capacity of condensate per stroke.

11) Water + gas filled floats can sustain the water hammer. Water hammer is a phenomenon in which the cold segregated condensate (generated at plant stoppages) flows with very high velocity at the start of the process. This high strength float reduces the damage to float due to water hammer.

12) The float is filled with water internally to generate pressure on receiving heat. The time required to generate steam pressure depends upon the latent heat of the water. The same principle can be applied with the fluid having lower latent heat of vaporization than water.

13) Instead of using the liquid for generating pressure, the solid state particles can also be used which have sublimation property.

14) The float can be filled with an inert gas such as N2 gas. From safety and hazardous point of view, it is preferable to use inert gases at higher pressure.

15) Water or any other liquid can be filled into the float through a non return valve type construction. Alternatively, water can be filled in the float through a pipe and then the pipe can be crimped. Or any other type of assembly options can be used to fill the float such that after pressurization, there will not be any leakage.

In view of the wide variety of embodiments to which the principles of the present invention can be applied, it should be understood that the illustrated embodiments are exemplary only. The illustrated embodiment should not be taken as limiting the scope of the present invention. For example, the interactions between the components may be taken in sequences other than those described, and more or fewer elements may be used. While various elements of the preferred embodiments have been described as being implemented, other embodiments implementations may alternatively be used, and vice-versa.

Claims

Claims:

[1] A float adapted to withstand high external pressure; said float filled with pressurised fluid.

[2] A float as claimed in claim 1, wherein said fluid comprises air, an inert gas or a combination of water and an inert gas.

[3] A float as claimed in claim 1, wherein the float is hermetically sealed.

[4] A float as claimed in claim 1, wherein mass of fluid in float is variable.

[5] A float as claimed in claim 1, wherein the float is provided with means to increase mass of fluid in the float.

[6] A float adapted to withstand high external pressure as herein above described with reference to the accompanying drawings.