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AIRBORNE LEAK DETECTION



STEAM LEAKS - ULTRASONIC VALVE
& STEAM TRAP INSPECTION

DESCRIPTION

When valves or steam traps leak or fail, it can be extremely costly in terms of product quality, safety and energy loss. Valve operation effects the way fluids will flow through a system. There are great differences in the way particular valves and steam traps work.

The ULTRAPROBE® makes it easy to adjust for these differences and readily determine operating conditions while valves and traps are on-line.



HOW ULTRASONIC LEAK DETECTION WORKS

As fluid moves from the high pressure side of a valve through the seat to the low pressure side, it produces turbulence. This turbulence generates ultrasound which is detected by the Ultraprobe® and translated, via heterodyning, down into the audible range.

The translated ultrasounds are heard through headphones and seen as intensity increments on a meter. High frequency tuning allows users to adjust for differences in fluid viscosity (i.e. water vs. steam) and reduce any interference from stray pipe noises.

LEAK DETECTION METHOD

Inspection methods vary depending on the type of valve or steam trap. Therefore the primary rule is to know the details of your system, for example the way a specific trap or valve may work under specific conditions. In order to determine trap/valve condition such as leakage or blockage: touch upstream of the valve or trap and reduce the sensitivity of the instrument until the meter/display panel reads about 50% of scale. If the instrument has frequency tuning, you may also use this feature to hear the trap or valve sound quality more clearly. Simply tune the frequency until the sound you would expect to hear becomes clear. It's that simple.

Next, touch downstream of the valve or trap and compare intensity levels. If the sound is louder down stream, the fluid is passing through. If the sound level is low, the valve or trap is closed. Ultrasonic valve and steam trap inspection is considered a "positive" test in that an operator can instantly identify sound quality and intensity differentials and thereby determine operating condition accurately. A steam trap troubleshooting guide is available from the factory upon request.  

In a steam system with 150 lbs. of pressure and a production cost of $6 per thousand pounds, a leak 1/32" in diameter - no larger than the tip of a ball point pen - can cost $249 per year.

In a 50 p.s.i. system with a production cost of $8/1000 pounds, a number of small leaks totaling about 1/4" will cost $8,339.52 in one year. Double the number of leaks to total 1/2" and the cost will be $33,358.08.

At Sun Co.'s Toledo, Ohio refinery, the Ultraprobe® identified 188 malfunctioning steam traps. Savings from replacing these traps have been in the range of $56,000 per year based on reducing 450 p.s.i. steam consumption by about 1,000 lb./hr.

Chevron USA, Perth Amboy NJ has six to eight thousand steam traps throughout the plant. The plant generates close to 500,000 lb./hr. of steam. A steam trap audit with the UE SYSTEMS' Ultraprobe® revealed the trap failure rate was up to 28%. The refinery has increased its steam trap reliability by 15% within two years after the Ultraprobe® was put into use. The reduction in steam losses is savings at least $50,000 a month.

Indiana University-Perdue University campus at Indianapolis has three to four thousand steam traps. Technicians using the Ultraprobe® to monitor steam traps and by-pass valves estimate they are saving $300,000 per year.

STEAM TRAPS

The purpose of a Steam Trap is to keep steam in the system while removing condensate (water) and air.  Air can reduce the heat transfer ability of steam and cause corrosion.  Condensate / Water substantially reduces heat transfer and the ability of a steam device to do work.  When a steam trap fails, it allows steam to blow-through along with the condensate.  This loss of steam can represent a substantial energy loss.  A basic component of all industrial energy audits in plants with steam is a stream trap inspection and repair/replacement program.

OPERATION

There are several types and manufacturers of steam traps.  The most common is the Mechanical Trap.  Mechanical traps operate by using the difference in density between steam and condensate.  The Inverted Bucket is the most common mechanical trap.  The float resembles a bucket (4).

A float (4) within the trap detects the variance in weight between a gas and a liquid in the chamber (1).  Condensate comes through the inlet (3) and the mechanical action (2) drains it out the drain (5) 

Thermostatic traps detect the variation in temperature between steam and condensate at the same pressure. The sensing device operates the valve in response to changes in the condensate temperature and pressure.

Thermodynamic Traps use volumetric and pressure differences that occur when water changes state into gas. These changes act upon the valve directly.

STEAM TRAP AUDITS

Most traps fail in the open mode. When this occurs, at times, a boiler may begin to work harder to produce the necessary energy to perform a task which, in turn, can create high back pressure to the condensate system. This inhibits the discharge capacities of some traps, which may be beyond their rating, and cause system inefficiency. While most traps operate with back pressure, they’ll do so only at a percentage of their rating, affecting everything down the line of the failed trap. Steam quality and product is affected.

A closed trap produces condensate back-up into the steam space. The equipment will not produce the intended heat. As an example, if there are four coils in a dryer and only three are operating, it will take longer for the dryer to dry a product, which will have a negative effect on production.

Excluding design problems, two of the most common causes of trap failure are over sizing and dirt. Over sizing causes traps to work too hard. In some cases this can result in blowing of live steam. As an example, an inverted bucket trap can lose its prime due to an abrupt change in pressure. This will cause the bucket to sink, forcing the valve open.

Dirt is always being created in a steam system. Excessive build-up can cause plugging or prevent a valve from closing. Dirt is generally produced from pipe scale or from over-treating of chemicals in a boiler.

HOW FAILURE EFFECTS EQUIPMENT

When steam traps cause a back-up of condensate in a steam main, the condensate is carried along with the steam. It lowers steam quality and increases the potential for water hammer. Not only will energy be wasted, equipment can be destroyed.

Water hammer occurs as slugs of water are picked up at high speeds in a poorly designed steam main or in pipe coils or where there is a lift after a steam trap. In some systems, the flow may be at 120 feet per second, which is about 82 m.p.h. As the slug of condensate is carried along the steam line it reaches an obstruction, such as a bend or a valve, where it is suddenly stopped. The effect of this impact can be imagined. It is important to note that the damaging effect of water hammer is due to steam velocity, not steam pressure. It can be as damaging in low pressure systems as it can in high. This can actually produce a safety hazard, as a valve or a strainer can be blown out by the force of water hammer.

Condensate in a system is destructive. It can cause valves to become wiredrawn and unable to hold temperatures as required. Little beads of water in a steam line can eventually cut any small orifices the steam normally passes through. Wire-drawing will eventually cut enough of the metal in a valve seat that it prevents adequate closure, producing leakage in the system.



COMPRESSED AIR LEAKS

AIR LEAK COST

Diameter Of Leak

Cubic
Feet/Minute

Cubic Feet/Day

Loss/Day Dollars

Loss/Month Dollars

Loss/Year Dollars

 

 

1/64"

 

.45

 

 

 

 

 

576

 

$0.10

 

 

$3.00

 

 

$36.00

 

 

 

1/32"

 

1.60

 

 

2,304

 

$0.40

 

 

$12.00

 

 

$144.00

 

 

 

3/64"

 

3.66

 

 

5,270

 

$0.95

 

 

$28.50

 

 

$342.00

 

 

 

1/16"

 

6.45

 

 

9,288

 

$4.65

 

 

$49.50

 

 

$594.00

 

 

 

3/32"

 

14.50

 

 

20,880

 

$3.75

 

 

$112.50

 

 

$1,500.00

 

 

 

1/8"

 

25.80

 

 

37,152

 

$6.70

 

 

$201.00

 

 

$2,412.00

 

 

 

3/16"

 

58.30

 

 

83,952

 

$15.10

 

 

$453.00

 

 

$5,436.00

 

 

 

1/4"

 

103.00

 

 

148,320

 

$26.70

 

 

$801.00

 

 

$9,612.00

 

 

 

5/16"

 

162.00

 

 

233,280

 

$42.00

 

 

$1,260.00

 

 

$15,120.00

 

 

 

3/8"

 

234.00

 

 

336,960

 

$60.65

 

 

$1,819.50

 

 

$21,834.00

 

                                       
Based on 100 PSIG, $0.18/MCF, 8,760 Hours/Year

 

AIR LEAK COST

Diameter Of Leak

Cubic
Feet/Minute

Cubic Feet/Day

Loss/Day Dollars

Loss/Month Dollars

Loss/Year Dollars

 

 

1/64"

 

.45

 

 

 

 

 

576

 

$0.13

 

 

$3.90

 

 

$47.00

 

 

 

1/32"

 

1.60

 

 

2,304

 

$0.55

 

 

$16.50

 

 

$198.00

 

 

 

3/64"

 

3.66

 

 

5,270

 

$1.26

 

 

$37.80

 

 

$454.00

 

 

 

1/16"

 

6.45

 

 

9,288

 

$2.22

 

 

$66.60

 

 

$800.00

 

 

 

3/32"

 

14.50

 

 

20,880

 

$5.01

 

 

$150.30

 

 

$1,804.00

 

 

 

1/8"

 

25.80

 

 

37,152

 

$8.91

 

 

$367.30

 

 

$3,208.00

 

 

 

3/16"

 

58.30

 

 

83,952

 

$20.14

 

 

$604.20

 

 

$7,250.00

 

 

 

1/4"

 

103.00

 

 

148,320

 

$35.59

 

 

$1,067.70

 

 

$12,812.00

 

 

 

5/16"

 

162.00

 

 

233,280

 

$55.98

 

 

$1,679.40

 

 

$20,153.00

 

 

 

3/8"

 

234.00

 

 

336,960

 

$80.87

 

 

$2,426.10

 

 

$29,113.00

 

                                       
Based on 100 PSIG, $0.24/MCF, 8,760 Hours/Year

 
 
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