AU2002340084A1

AU2002340084A1 - Steam trap instrument module

Info

Publication number: AU2002340084A1
Application number: AU2002340084A
Authority: AU
Inventors: Timothy Ray Rebik
Original assignee: Fisher Controls International LLC
Current assignee: Fisher Controls International LLC
Priority date: 2001-10-18
Filing date: 2002-10-03
Publication date: 2003-07-03
Anticipated expiration: 2022-10-03

Description

STEAM TRAP INSTRUMENT MODULE

Field of the Invention

The present invention relates generally to steam traps and, more specifically,

to an instrument module for use with a steam trap that measures, for example, total

steam flow and/or total condensate flow through a steam trap, and which further

may be used to detect failure of the steam trap.

Background of the Invention

Steam traps for use on process steam systems are generally well known in

the art. It is equally well known that many steam traps are prone to failure. When

a steam trap fails in a closed position, condensate is trapped within the system, thus

causing the outlet temperature of a process fluid to drop. Such temperature

decreases are easy to monitor and detect, and thus it is relatively easy to detect when

a steam trap has failed in the closed position.

However, it generally is not as easy to detect when a steam trap has failed in

an open position. When a steam trap fails in the open position, live steam can be

vented directly to the atmosphere through vent piping. The efficiency of the system

may drop quickly, but the failure is generally not easy to detect based on variations

in typical system parameters. Many such steam traps may be located in remote or

difficult to access locations, and therefore may not be detected for some time. All

the while, a failed steam trap venting live steam may negatively impact the overall

operating efficiency of the process system. Brief Description of the Drawings

Fig. 1 is a fragmentary schematic diagram of a process steam heating

system;

Fig. 2 is an enlarged cross-sectional view of a steam trap having a flow

control module assembled in accordance with the teachings of the invention; and

Fig. 3 is an enlarged fragmentary view illustrating the relationship between

the plug and the orifice leading to the condensate return.

Detailed Description of the Disclosed Embodiment

The example described herein is not intended to be exhaustive or to limit the

scope of the invention to the precise form or forms disclosed. Rather, the following

exemplary embodiment has been chosen and described in order to best explain the

principles of the invention and to enable others skilled in the art to follow the

teachings thereof.

Referring now to the drawings, Fig. 1 is a schematic representation of a

conventional process steam system 10 having a steam line 12. The steam line 12

includes an inlet end 14 and an outlet or condensate return 16. The process steam

system 10 includes a device requiring process steam, which in the disclosed example

is a heat exchanger 18. The steam system 10 would typically include a number of

other components (not shown) of the type typically found on steam systems. Such

typical components and the operation thereof would be known to those of skill in the

art and thus need not be discussed further. It will be understood that the heat

exchanger 18 is discussed herein for purposes of illustration only and is not intended to limit the scope of the invention described herein. The steam system 10 may well

employ a different device trap of instead of a heat exchanger 18. The steam system

10 includes a steam trap assembled in accordance with the teachings of the present

invention and which is generally referred to by the reference numeral 20.

The steam system 10 includes a control valve 22 of the type commonly

employed in the art, and a supply pipe 24 leading from the control valve 22 to an

inlet 26 of the heat exchanger 18. An outlet pipe 28 leads from the heat exchanger

18 to in inlet 30 on the steam trap 20, and an outlet 32 on the steam trap 20 leads to

the condensate return 16. The heat exchanger 18 typically includes a cold water

inlet 34 and a hot water outlet 36 as would be known. It will be understood that,

instead of water, the system 10 may use any other suitable process fluid as would be

known. However, for convenience of explanation the following description will

refer only to water, it being understood that the teachings herein are equally

applicable to a process system employing other suitable fluids.

Referring now to Fig. 2, the steam trap 20 includes a body 38 and a cover

40. The body 38 and the cover 40 may be joined to each other in a conventional

manner and are preferably separable from each other. The body 38 and the cover

40 cooperate to define a reservoir 41. A float 42 is disposed inside of the steam trap

20 and is mounted by a pivot 44 to a mounting portion 46. Accordingly, the float

42 is free to travel up and down along a generally arcuate path as indicated by the

reference arrow A. It will also be appreciated that the float 42 will generally travel

along the path A in response to the presence of, absence of, or changes in the level

of fluid inside the steam trap 20. As an alternative, it is conceivable that the float may otherwise be shiftable or slideable, such as, for example, along a generally

linear path.

In the example shown the float 42 is connected to an arm 43 having an outer

end 45 and an inner end 47. The inner end 45 is mounted to the pivot 44. A pair of

arms 48, 50 are mounted to the inner end 45 of the arm 43. The arm 48 extends

generally upwardly from the pivot 44 to form a target 49, while the arm 50 extends

generally downwardly from the pivot 44. A plug 52 is mounted to or otherwise

carried by the lower arm 50. An orifice 54 is defined inside of the steam trap 20

and provides a passage 56 between the outlet 32 and an interior 58 of the body 38.

It will be appreciated that the plug 52 will close the orifice 54 when the float 42

drops (e.g., when there is no fluid or only minimal fluid within the body 38 of the

steam trap 20). It will also be appreciated that the plug 52 will move away from

and thus open the orifice 54 when the float 42 moves upwardly (e.g., when a

sufficient amount of fluid gathers in the body 38 of the steam trap 20). Finally, the

orifice 54 will have known dimensions, such that

An instrument **module 58 is attached to the steam trap 20. The instrument

module 58 may be mounted to a mounting portion 60 of the cover 40, or to any

other suitably prepared surface or area. Preferably, a space 61 is provided between

the instrument module 58 and the balance of the steam trap 20 in order to prevent or

lessen possible overheating of the instrument module 58. The instrument module 58

includes a central processing unit or CPU 62. The CPU 62 may be any one of a

number of commercially available processing units. The instrument module 58

includes a pressure sensing system 64, a temperature sensing system 66, and an eddy current probe 68.

The pressure sensing system 64 may include a pair of pressure transducers

70, 72. The pressure transducer 70 may be disposed generally adjacent to the inlet

30, while the pressure transducer 72 may be disposed generally adjacent to the

outlet 32. The temperature sensing system may include a pair of temperature

transducers 74, 76. The temperature transducer 74 may be disposed generally

adjacent to the inlet 30, while the temperature transducer 76 may be disposed

generally adjacent to the outlet 32.

The eddy current probe 68 includes an end 78 which is disposed generally

adjacent to the arm 48. Accordingly, movement of the float 42 causes a

corresponding movement of the arm 48, which is sensed by the eddy current probe

as will be explained in greater detail below. Each of the eddy current probe 68, the

pressure transducers 70, 72, and the temperature transducers 74, 76 are operatively

connected to the -CPU 62 in a conventional manner.

The steam trap 20 may also include a phase sensing system 80, which may

include a pair of phase sensors 82, 84. The phase sensor 82 may be disposed

generally adjacent to the inlet 30, while the phase sensor 84 may be disposed

generally adjacent to the outlet 32. The phase sensors 82, 84 are operatively

connected to the CPU 62 in a conventional manner. The phase sensors 82, 84 may

be, for example, any one of a number of commercially available conductivity

probes.

Each of the pressure transducers 70, 72 may be commercially available

pressure transducers. However, the size of the pressure transducers may be a consideration depending on the size of the steam trap 20. Suitable pressure

transducers are available from Rosemount, Inc., of Chanhassen, MN. It will be

appreciated that other types of pressure sensing devices may be suitable. Similarly,

each of the temperature transducers 74, 76 may be commercially available

temperature transducers, such as may be available from Rosemount, Inc. Again,

other types of temperature sensing devices may be suitable. A suitable eddy current

probe 68 is available from Bently Nevada Corporation.

In operation, the process steam system 10 works in a conventional manner.

Steam from a steam source (not shown) is routed toward the heat exchanger 18 or

other device in a conventional manner through the steam line 12. The steam enters

the heat exchanger at the inlet 26. Inside the heat exchanger, the heat from the

steam is used to heat cold water entering the heat exchanger 18 through the cold

water inlet 34. Heated water exits the heat exchanger 18 via the hot water outlet 36,

and may ultimately be used for heating or other purposes as would be known. The

operation of the heat exchanger is conventional and would be known.

During the heat exchange process, at least a portion of the steam will be

condensed to form a condensate as the steam loses heat and changes phase back into

a liquid. This condensate, after passing through the steam trap 20, will be returned

to the steam system 10 via the condensate return 16 in a conventional manner.

As shown in Fig. 2, steam or condensate, or some combination thereof, will

enter the steam trap 20 via the inlet 30. The position of the float 42 will depend on

the level of liquid or condensate inside the steam trap 20. Thus, as condensate

builds within the steam trap, the float will rise, thus moving the plug 52 away from the orifice 54 and allowing condensate within the body 38 of the steam trap 20 to

flow out the outlet 32 to the condensate return 16.

The eddy current probe 68 produces an output 68a which is routed to the

CPU 62. The pressure transducers 70, 72 each produce an output 70a, 72a,

respectively, which are routed to the CPU 62. Similarly, the temperature

transducers 74, 76 each produce an output 74a, 76a, respectively, which are routed

to the CPU 62. Finally, the phase sensors 82, 84 (if provided) each produce an

output 82a, 84a, respectively, which are routed to the CPU 62.

For a variety of reasons, it may be desirable to measure the total flow of

condensate (during normal operation) or steam (during a steam trap failure

condition) flowing through the steam trap 20. If the steam trap has failed open, the

eddy current probe will be able to detect the position of the plug 52 relative to the

orifice 54. This is due to the fact that the movement of the target 49 on the arm 48

is indicative of the movement of the plug 52 away from the orifice 54, due to the

fact that the dimensions of the arms 48, 50 are known. Also, because the

dimensions of the plug 52 and the orifice 54 are known, the cross-sectional area of the passage 56 would be known.

For example, referring now to Fig. 3, in the event the plug 52 is very close

to the orifice 54, then the condensate or steam will flow along a generally annular

path 86 past the plug 52 and into the orifice 54. In the event the plug 52 is very

close to the orifice 54, the total cross-sectional area of the annular path 86

(commonly referred to as the "annular area") will be relatively small. On the other

hand, in the event the plug 52 is further away from the orifice 54, the total cross- sectional area of the path 86 will be relatively larger. Because the dimensions of the

orifice and the plug are known, and because the location of the plug 52 relative to

the orifice 54 can be determined via the output 68a from the eddy current probe 68,

the total cross-sectional area of the path 86 can be calculated using known geometric

principles. It will be understood that the total cross-sectional area of the path 86

will increase as the plug 52 travels away from the orifice 54 as the float 42 rises in

response to additional condensate in the reservoir 41. On the other hand, it will be

understood that the total cross-sectional area of the path 86 will decrease as the plug

52 travels toward the orifice 54 as the float 42 is lowered in response to less

condensate or the absence of condensate in the reservoir 41. When the plug 52 is

disposed as shown in Fig. 2, it will be appreciated that the total cross-sectional area

of the path 86 will be zero due to the fact that the plug 52 is seated against the

orifice 54.

Using the respective outputs from the pressure sensing system 64, the

temperature sensing system 66, the eddy current probe 68, and the phase sensing

system 80, the CPU can determine the total flow of condensate and/or steam

flowing through the orifice using well known engineering principles, such as, for

example, by using ASME water and steam tables along with general thermodynamic

and fluid dynamic principles, all of which are readily available and known to those

of skill in the art and which may be readily programmed into or otherwise available

to the CPU 62. Thus, based on the outputs received from the various temperature,

pressure, and phase sensing systems, and based on the known dimensions of the

annular path 86, the CPU 62 can readily calculate the total condensate flow through the steam trap 20 during normal operations, or the total steam flow through the

steam trap 20 in the even that the steam trap 20 has failed in an open condition.

By way of further explanation of an exemplary mode of operation, the

pressure at the inlet 30 is sensed by the pressure transducer 70, and the pressure at

the outlet 32 is sensed by the pressure transducer 72 at the outlet 32. The respective

outputs 70 and 72a are routed to the CPU 62. The temperature at the inlet 30 is

sensed by the temperature transducer 74, with the output 74a routed to the CPU 62.

The travel of the plug 52 is determined by the eddy current probe 68, with the

output 68a thereof also routed to the CPU 62. The CPU process the various

outputs, and using the aforementioned look up tables, calculates total flow through

the steam trap 20.

In the event that the float mechanism has failed in the open position, steam

will flow through the steam trap 20, as all of the condensate will drain through the

condensate return 16 until live steam flows through the steam trap 20. The

temperature and pressure values processed by the CPU will then be indicative of

trap failure, and the CPU will then calculate total steam loss through the steam trap

20.

In the event the float mechanism has failed in the closed position (e.g., with

the plug 52 blocking the orifice 54), condensate will flood the reservoir 41 of the

steam trap 20. Again, readings from the pressure, temperature, and phase sensors

will be indicative of the presence of water or fluid in the steam trap.

Those skilled in the art will appreciate that, although the teachings of the

invention have been illustrated in connection with certain exemplary embodiments, there is no intent to limit the invention to the disclosed example. Instead, the

intention of this application is to cover all modifications and embodiments fairly

falling within the scope of the appended claims either literally or under the doctrine

of equivalents.

Claims

What is claimed:

1. A steam trap system comprising:

a steam trap, the steam trap including an inlet, an outlet, and a float, the inlet

and the outlet separated by an orifice, the steam trap further including a plug

operatively coupled to the float, the plug disposed adjacent the orifice and arranged

to open and close the orifice in response to movement of the float;

an instrument module mounted to the steam trap, the instrument module

including a central processing unit operatively coupled to each of an inlet pressure

transducer, an outlet pressure transducer, a temperature transducer, and an eddy

current probe;

the inlet pressure transducer arranged to detect pressure at the steam trap

inlet;

the outlet pressure transducer arranged to detect pressure at the steam trap

outlet;

the temperature transducer arranged to detect temperature within the steam

trap;

the eddy current probe arranged to detect movement of the plug; and

the central processing unit receiving an output from each of the inlet pressure

transducer, the outlet pressure transducer, the temperature transducer, and the eddy

current probe, the central processing unit arranged to determine total steam flow and

total condensate flow through the steam trap.

2. The steam trap system of claim 1 , wherein the temperature transducer

is disposed adjacent the steam trap outlet.

3. The steam trap system of claim 1 , wherein the temperature transducer

is disposed adjacent the steam trap inlet.

4. The steam trap system of claim 2, including a second temperature

transducer disposed adjacent the steam trap inlet, the central processing unit

operatively coupled to and receiving an output from the second temperature

transducer.

5. The steam trap system of claim 1, wherein the float is mounted to a

pivot arm, and including a target mounted to the pivot arm, the pivot arm and the

target moveable along with the float, and wherein the eddy current probe is

positioned to be responsive to movement of the target.

6. The steam trap of claim 1 , including a phase sensor disposed within

the steam trap.

7. The steam trap of claim 1, including a phase sensor disposed within

the steam trap, the phase sensor arranged to detect condensate at the inlet and at the

outlet of the steam trap.

8. A steam trap system comprising:

and the outlet separated by an orifice, the steam trap further including a plug

to open and close the orifice in response to movement of the float;

a instrument module, the instrument module including an inlet pressure

transducer, arranged to detect pressure at the steam trap inlet, an outlet pressure

transducer arranged to detect pressure at the steam trap outlet, a temperature transducer arranged to detect temperature within the steam trap, and an eddy current

probe arranged to detect movement of the plug; and

a central processing unit operatively coupled to and arranged to receive an

output from each of the inlet pressure transducer, the outlet pressure transducer, the

temperature transducer, and the eddy current probe, the central processing unit

arranged to process the respective outputs to thereby determine total steam flow and

total condensate flow through the steam trap.

9. The steam trap system of claim 8, wherein the temperature sensor is

disposed adjacent the steam trap outlet.

10. The steam trap system of claim 8, wherein the temperature sensor is

disposed adjacent the steam trap inlet.

11. The steam trap system of claim 9, including a second temperature

sensor disposed adjacent the steam trap inlet, the central processing unit operatively

coupled to and receiving an output from the second temperature sensor.

12. The steam trap system of claim 8, wherein the float is mounted to a

target moveable along with the float, and wherein the eddy current probe is

positioned to be responsive to movement of the target.

13. The steam trap of claim 8, including a phase sensor disposed within

the steam trap and operatively coupled to the central processing unit.

14. The steam trap of claim 8, including a target mounted to the float, the

target positioned- adjacent the eddy current probe.

15. The steam trap of claim 8, wherein the instrument module is

contained in a housing, the housing removably attachable to the steam trap.

16. A steam trap system comprising:

and the outlet separated by an orifice, the steam trap further including a plug

to open and close the orifice in response to movement of the float;

a instrument module, the instrument module including a pressure transducer

arranged to detect pressure in the steam trap, a temperature transducer arranged to

detect temperature within the steam trap, an eddy current probe arranged to detect

movement of the plug, and a phase sensor arranged to detect phase within the steam

trap; and

a central processing unit operatively coupled to and arranged to receive an

output from each of the pressure transducer, the eddy current probe, and the phase

sensor, the central processing unit arranged to process the respective outputs to

thereby determine total steam flow and total condensate flow through the steam trap.

17. The steam trap system of claim 16, wherein the pressure transducer is

arranged to detect pressure adjacent the inlet and adjacent the outlet.

18. The steam trap system of claim 16, wherein the temperature

transducer is arranged to detect temperature adjacent the inlet and adjacent the

outlet.

19. A steam trap system comprising:

and the outlet separated by an orifice, the steam trap further including a plug

to open and close the orifice in response to movement of the float;

a instrument module, the instrument module including a pressure transducer

detect temperature within the steam trap, and an eddy current probe arranged to

detect movement of the plug; and

a central processing unit operatively coupled to and arranged to receive an

output from each of the pressure transducer, the temper ature transducer, and the

eddy current probe, the central processing unit arranged to process the respective

outputs to thereby determine total steam flow and total condensate flow through the

steam trap.

20. The steam trap system of claim 19, wherein the pressure transducer is

arranged to detect pressure adjacent the inlet and adjacent the outlet, the temperature

outlet, and including a phase sensor arranged to detect phase inside the steam trap

changes, the phase sensor operatively connected to the central processing unit.