GB2512044A

GB2512044A - Seal support system

Info

Publication number: GB2512044A
Application number: GB201304255A
Authority: GB
Inventors: Christopher Iveson
Original assignee: AES Engineering Ltd
Current assignee: AES Engineering Ltd
Priority date: 2012-03-09
Filing date: 2013-03-08
Publication date: 2014-09-24
Anticipated expiration: 2033-03-08
Also published as: GB201304255D0; GB201204212D0; GB2512044B

Abstract

Apparatus and method for preventing the temperature of liquid inside a seal support system from falling below the freezing point of the liquid while maintaining constant pressure inside the seal support system. A pressure vessel 2 is provided in closed loop fluid communication with a mechanical seal 4. The closed loop includes a feed line 3 to the mechanical seal and a thermostatic valve 8 for releasing liquid when the temperature of the liquid falls below a predetermined temperature. The thermostatic valve may be positioned adjacent to the seal, or attached to a connecting member which is adjacent to the seal, or attached directly to the seal. A pressure regulating valve 7 supplies further liquid to the vessel via an external supply line 6. A further thermostatic value 9 may be positioned inside the external supply line.

Description

SEAL SUPPORT SYSTEM

Field of the Invention

The present invention relates to support systems, for seals such as mechanical seals. The invention is particularly concerned with the prevention of fluid inside a seal support system from freezing while placed inside extreme cold environments.

Background to the Invention

A seal support system comprises a vessel/tank which generally contains a volume of fluid. The vessel is piped to a sealing device on a pump, mixer or piece of rotating equipment. Generally there is a return pipe that is connected back to the vessel, which closes the loop'. The fluid inside the vessel is referred to in the industry as barrier/buffer fluid.

is A mechanical seal, which is supported by the seal support system, generally comprises a rotating member attached to the pump shaft and a stationary member attached to the pump housing. The rotating member is in direct contact with the stationary member which provides the seal. A basic operating principle of mechanical seals is that they require a fluid film' that provides a lubricant between the stationary and rotating members. A barrier/buffer fluid inside the seal support system generally provides the fluid film. The seal support system will be subject to a loss of pressure over time. Because of this, it is not uncommon for a seal support system to have a fluid feed line entering the vessel, generally originating from a mains water supply. The purpose of this fluid feed line is to ensure that the correct level of barrier/buffer fluid is maintained inside the seal support system.

Commonly used on seal support systems are other items of equipment that perform s various duties. Some examples of these are pressure regulators and extra pieces of cooling equipment that help cool the barrier/buffer fluid.

Under extreme cold conditions, the barrier/buffer fluid is prone to a drop in temperature, causing the liquid inside the system to freeze. If the barrier/buffer fluid does freeze, this has the potential to have a catastrophic effect on the seal, as it will starve the seal faces of the fluid film' causing it to fail completely in a short time.

Statements of the Invention

According to the present invention, there is provided apparatus that prevents the temperature ot liquid inside a seal support system from falling below the freezing point of the liquid, while maintaining substantially constant pressure inside said seal support system, the apparatus comprising a vessel, a teed line capable ot providing a closed loop fluid communication between the vessel and a mechanical seal, a thermostatic valve positioned in the closed loop seal support system and operable to release a liquid from said seal support system when the temperature of said liquid tails below a predetermined temperature, means for supplying liquid to said vessel via an external supply line, and a regulatory device for supplying further liquid to said seal support system.

Accordingly, apparatus ot the invention measures the temperature of the liquid at the coolest point in the system, which is generally accepted to be the barrier feed line into the mechanical seal. As the temperature of the liquid in this area drops to approach freezing point, the system releases said liquid to drain. This action causes is a drop in pressure inside the seal support system, which is replaced with liquid from a liquid supply line.

The system comprises in its simplest form: I A pressure vessel I A mechanical seal * A fluid feed line into said pressure vessel from an external source.

* A pressure regulator regulating the fluid from said fluid feed line into said pressure vessel.

I Pipe work feeding fluid from said pressure vessel into said mechanical seal (barrier inlet) and back from said mechanical seal into said vessel (barrier outlet).

I A primary thermostatic control valve.

Preferably said primary thermostatic control valve is attached to said mechanical seal on said barrier inlet side of said mechanical seal, which is generally accepted to be the coolest area on said seal support system. By way of clarity, attached' is defined in this document to mean either directly to, or by way of a connecting member, such as a T piece or any other relevant fitting.

Preferably, said thermostatic control valve is connected to said pipe work in such a manner that it presents no restriction to the flow of said liquid through said system.

Preferably, said primary thermostatic control valve releases liquid inside said seal support system as the temperature inside said seal support system drops close to freezing point. As this occurs, said liquid shall be vented to drain, which causes a pressure drop inside said seal support system.

Preferably, there is present a pressure regulator positioned on the liquid feed line to said pressure vessel, which detects a pressure drop inside said seal support system, and replaces the drained liquid with replacement liquid from an external source.

Preferably, there is also present on said seal support system a secondary zs thermostatic control valve adjacent to said pressure regulator in the liquid feed line on the opposite side of said pressure vessel, so that said pressure regulator is positioned between said pressure vessel and said secondary thermostatic control valve. The purpose of said secondary thermostatic control valve is to prevent the liquid in said liquid feed line from freezing. Preferably this is achieved by again sensing the temperature of the liquid inside said liquid feed line and releasing said liquid as it approaches freezing point. As this occurs, said liquid shall be vented to drain, which shall be replaced by the liquid from the external source.

The present invention also provides a method for preventing the temperature of liquid inside a seal support system from falling below the freezing point of the liquid while maintaining substantially constant pressure inside said seal support system, the method comprising a vessel in closed loop fluid communication with a mechanical seal, said closed loop including a feed line from said vessel to said mechanical seal, supplying fluid to said vessel via an external liquid supply line, and controlling said liquid supply by a regulating valve, said valve being portioned inside said feed line.

Brief Description of the Drawings

Figure 1 shows a schematic drawing example of a seal support system, including a mechanical seal and a mechanism which prevents the fluid inside the system from freezing. This includes a thermostatic valve positioned in the barrier feed line, as well as in the liquid feed line to the vessel.

Figure 2 shows a schematic drawing example of an alternative arrangement of a seal support system whereby said thermostatic control valves are positioned at the end of a connector pipe, which allows the liquid being vented to be appropriately angled into a dedicated drain source.

Detailed Description of the Invention

Figure 1 shows a schematic drawing of a seal support system 1. Said seal support system 1 comprises a pressure vessel 2 that houses a volume of liquid. Attached to said pressure vessel 2 is a barrier fluid inlet 3, which feeds liquid to the mechanical seal 4, which is then returned back to said pressure vessel 2 through the barrier fluid outlet 5.

Attached to said pressure vessel 2 is also present a liquid feed line 6 which is regulated into the pressure vessel 2 by a pressure regulator 7, the purpose of which is to control the pressure, and volume of liquid inside said pressure vessel 2.

There is also present a primary thermostatic valve 8, which is positioned inside said barrier fluid inlet 3. The purpose of said primary thermostatic valve 8 is to protect the liquid inside said seal support system 1 from freezing. This is most likely to occur whilst the mechanical seal 4 is stationary (not in use)-The primary thermostatic valve 8 operates by sensing the temperature of the liquid inside the barrier fluid inlet 3 and as the temperatures of said liquid drops, because of external factors, to approaching freezing point, the primary thermostatic valve 8 automatically opens to release said freezing liquid from said seal support system 1. This creates a pressure drop inside said seal support system 1, which is sensed by the pressure regulator 7, which reacts by releasing liquid from the liquid supply line 6 into the pressure vessel 2, thus replacing the liquid vented by the primary thermostatic valve 8. This operation prevents liquid inside said seal support system 1 from freezing.

A secondary thermostatic valve 9 is positioned inside said liquid supply line 6, the purpose of which is to prevent the liquid inside said liquid supply line 6 from freezing.

This is most likely to occur whilst the mechanical seal 4 is in dynamic operation. The secondary thermostatic valve 9 operates by sensing the temperature of the liquid inside the liquid supply line 6 and as said liquid approaches freezing point, said secondary thermostatic valve 9 automatically opens to release said freezing liquid from liquid supply line 6. This liquid is then replaced by an external source further up the liquid supply line 6.

Figure 2 shows a schematic of an alternative seal support system 10. Said alternative seal support system is identical to said original seal support system 1 except that there is present a primary connecting pipe 11 connecting the primary thermostatic valve 8 to the barrier fluid inlet 3 and also a secondary connecting pipe 12 connecting the secondary thermostatic valve 9 to the liquid supply line.

The purpose of both the primary connecting pipe 11 and secondary connecting pipe 12 is to allow said liquid inside said alternative seal support system 10 to be effectively piped to an appropriate drain 13. a

Claims

Claims 1. Apparatus that prevents the temperature of liquid inside a seal support system from falling below the freezing point of the liquid, while maintaining substantially constant pressure inside said seal support system, the apparatus comprising a vessel, a feed line capable of providing a closed loop fluid communication between the vessel and a mechanical seal, a thermostatic valve positioned in the closed loop seal support system and operable to release a liquid from said seal support system when the temperature of said liquid falls below a predetermined temperature, means for supplying liquid to io said vessel via an external supply line, and a regulatory device for supplying further liquid to said seal support system.
2. Apparatus according to claim 1, wherein said thermostatic valve is in use positioned adjacent to said mechanical seal.
3. Apparatus according to claim 2, wherein said thermostatic valve is, in use, attached to a connecting member which is then adjacent to said mechanical seal.zo
4. Apparatus according to claim 2, wherein said thermostatic valve is attached directly to said mechanical seal.
5. Apparatus according to any of the preceding claims, and including a further thermostatic valve positioned inside said external liquid supply line.
6. Apparatus according to claim 5, wherein said further thermostatic valve is positioned adjacent to said regulating device, which is in turn adjacent to said vessel.
7. Apparatus according to claim 5, wherein said further thermostatic valve is attached to a connecting member, which is then adjacent to said regulating device.
8. Apparatus according to claim 5, wherein said further thermostatic valve is attached directly to said regulating device.
9. Apparatus according to any of the preceding claims, wherein the liquid is water.
10. Apparatus according to Claim 1 and substantially as herein described.
11. Apparatus that prevents the temperature of liquid inside a seal support system from falling below the freezing point of the liquid while maintaining substantially constant pressure inside said seal support system, the apparatus being substantially as described herein with reference to Figure 1 and Figure 2 of the accompanying drawings.
12. A method for preventing the temperature of liquid inside a seal support system from falling below the freezing point of the liquid while maintaining substantially constant pressure inside said seal support system, the method comprising providing a vessel in closed loop fluid communication with a mechanical seal, said closed loop including a feed line from said vessel to said mechanical seal, supplying fluid to said vessel via an external liquid supply line, and controlling said liquid supply by a regulating valve, said valve being portioned inside said feed line.