Steam Leakage In Small Steam Turbines

Name: Steam Leakage In Small Steam Turbines
Uploaded: 2017-07-05T04:47:46+00:00
Duration: PTM31S17
Channel: Bathsheba Morton
Description: Steam Leakage In Small Steam Turbines

Steam Leakage In Small Steam Turbines
Bearing Housing/Pedestal Bearing Steam Leakage In Small Steam Turbines Turbine Case Oil Carbon Seals This presentation covers steam leakage in small steam turbines. The area that we are looking at is leakage that occurs along the shaft.

Bearing Housing/Pedestal
Turbine Case Oil Carbon Seals This is a rendering of a turbine sealing system and bearing pedestal.

Turbine Case Oil Carbon Seals There is a large temperature variance between the turbine case and the bearing housing. The bearing housing is cooled by the oil reservoir that is used to lubricate the bearings. Often a water jacket is used to keep the oil temperature at an acceptable temperature. 230 degrees f. 230 degrees f. Temperature

Steam Turbine Case Oil Carbon Seals The turbine case is pressurized with hot steam. Steam is always looking for the point of “least resistance”. Most often steam leakage will migrate to breaches in the case split lines. As the carbon rings deteriorate, steam leakage occurs along the shaft. 230 degrees f. 230 degrees f. Temperature

Condensate Magnet Bearing Housing/Pedestal Bearing Seal Failure Steam Turbine Case Oil Carbon Seals Seal failure will occur either on the split lines or along the shaft. 230 degrees f. Temperature

Steam Path Bearing Housing/Pedestal Bearing Turbine Case Oil
Carbon Seals Steam moves out of the case, down the shaft and past the carbon seals to atmosphere Steam moves out of the case, down the shaft and past the carbon seals to atmosphere.

Turbine Case Oil Carbon Seals Some steam dissipates into the atmosphere. In some instances (such as in cold climates), this could cause a visibility hazard. Some steam dissipates into the atmosphere. In some instances (such as in cold climates), this could cause a visibility hazard.

Turbine Case Oil Carbon Seals It could also cause a slipping hazard as condensate collects on the ground, or can cause severe burns if contacted near the exhaust path. It could also cause a slipping hazard as condensate collects on the ground, or can cause severe burns if contacted near the exhaust path.

$$$$$$$$$$ $$$$$$$$$$ Bearing Housing/Pedestal Bearing Turbine Case
Oil Carbon Seals $$$$$$$$$$ Lost steam is also money thrown into the wind. Proper sealing of the shaft will also generate a cash savings. Lost steam is also money thrown into the wind.

Turbine Case Oil Carbon Seals Ultimately, moisture begins to collect in the bearing housing. Yet another consideration – if water enters your bearing housing, the integrity of your oil (lubrication system) will be compromised.

Turbine Case Oil Carbon Seals Once the oil becomes contaminated with water, the oil will deteriorate. The result is lack of lubrication to the bearings. The bearings will deteriorate to the point of causing the turbine to fail. This could lead to bearing failure and ultimately, equipment failure.

Condensate Magnet Bearing Housing/Pedestal Bearing Turbine Case Oil Carbon Seals In event of a failure in the turbine shaft sealing system, the last barrier to oil contamination are the bearing housing seals. When shaft seals fail, your only barrier against oil contamination are your bearing case seals.

Condensate Magnet Bearing Housing/Pedestal Bearing Turbine Case Oil Carbon Seals The standard seal is an “H” seals, are usually configured as a laby. type seal with deflectors on either end. The aftermarket upgrades include modified “H” seals (Disrupter Seals) and bearing isolators, of which several types are marketed. CTS offers both upgrades. These seals can be standard OEM “H” seals, or “upgrades” such as modified “H” seals (Disrupter Seals) or aftermarket Barrier Seals.

Solutions #1 Try to reduce or eliminate steam leakage at the source.
The basic solution is to try to eliminate leakage at the source, which would of course, be along the shaft. #1 Try to reduce or eliminate steam leakage at the source.

Solutions #2 Protect your oil from contamination.
The basic solution is to try to eliminate leakage at the source, which would of course, be along the shaft. #2 Protect your oil from contamination.

Carbon Seals Carbon seals are the standard shaft seal in most small turbines. The standard shaft seals on most small steam turbines are carbon rings.

Carbon Seals Assuming that the carbons were properly sized and installed correctly, they work well for a period of time. However, carbons have a tendency to wear and deteriorate over time. Their sealing properties will never be as good as they were upon initial installation. If installed correctly, they provide a good seal. However they do deteriorate rapidly.

Effective Clearance Over Time
This chart compares the performance, over time, of carbon rings vs. Brush Seals. The performance of carbon rings deteriorates over time. The performance of Brush Seals remains constant.

Carbon Rings Advantages Inexpensive Easy to install
Perform well when properly sized and installed Lightweight Disadvantages Easily cracked/ chipped If not properly sized, can either seize on shaft or leak too much Short life, resulting in high leakage after short time Advantages and disadvantages of carbon rings. Note: CTS Brush Seals combine the advantages of carbon rings & Brush Seals into one slot.

Mechanical Seals Mechanical seals were popular about ten years ago.

Mechanical Seals Advantages Disadvantages Best sealing performance
Longer life than standard carbon seals Disadvantages Expensive initial investment Difficult to install, requires entire rotor to be removed for installation/ maintenance Can require permanent case modifications Finite life-span before a costly overhaul is required. Advantages and disadvantages of Mechanical Seals. Quite a few small turbines were retrofitted with these in the past. We have noticed several customers removing them recently. However, it was problematic being that some modifications had been performed on the case.

Brush Seals Brush Seals were first installed in steam turbines about ten years ago.

More durable than carbon seals
Brush Seals Advantages Moderately priced More durable than carbon seals Extremely long life Disadvantages Must be installed in shop Not stocked for all size turbines Relatively new technology for steam applications Heavy “floating” seals can gravitate downward on turbines that cycle, thus decreasing efficiency Brush Seals offer the newest technology for sealing small turbine shafts. They are more moderately priced than Mechanical Seals, more durable than carbon rings, and have an extremely long life. The downsides are that Brush Seals must be installed during an overhaul, they are not stocked for all turbine models, and they do not have a long track record. However, in the last decade, they have been installed in over one hundred know instances with a high degree of success. Most customers for Brush Seals are repeat customers.

Brush Seals Utility Turbines Mechanical Drive Turbines
Current Applications Utility Turbines Mechanical Drive Turbines Gas Turbines – Aircraft & Industrial Single Stage Turbines Elliott – All YR sizes Dresser Rand General Electric Westinghouse Brush Seals were initially developed by NASA for rocket and aircraft applications. Brush Seals are used in utility steam turbines (retractable packing), aircraft engines and industrial gas turbines. They have proved to increase efficiency in these applications. Currently, Brush Seals have been used in almost all brands of small steam turbines. They are most common on the Elliott Steam turbines, where the turbine configurations have been standardized.

Brush Seals Brush Pack Rotation Shaft
Brush Seals are “directional” meaning that they are angle with respect to the direction of rotation. They are also installed with a slight positive pressure against the shaft (usually around .005). The result is that the leakage reduction produces substantial effeciency gains.

Brushes are a Haynes 25 material
Holder Holder is SS Fence Flow This is a typical Brush Seal configuration. Brushes are sandwiched between rings to form a brush pack. Typically this is designed as a “floating” seal. Brush Pack Brushes are a Haynes 25 material

Brush Seals Little or no case modifications beyond original design specifications. Lower sustained leakage than carbon rings. Indefinite life span eliminating periodic replacement. Benefits

Brush Seals Installation Considerations

Compressor & Turbine Services. LLC
4/16/2017 Sealing faces and ID of carbon box are machined to assure a good seal fit. To install correctly, the sealing faces of the packing boxes must be skimmed to insure a good seal fit. Compressor & Turbine Services. LLC

4/16/2017 Like all sealing systems – internal turbine alignment is important. This is extremely critical where fixed, non-floating, seals are installed. Floating Brush Seals require less alignment precision. A line bore is unnecessary. Internal Alignment is Important On Fixed (non-floating) Brush Seals Compressor & Turbine Services. LLC

4/16/2017 Suggested Shaft Coatings – None – Base Metal Chromium Carbide Tungsten Carbide (preferred) Shaft coatings: The recommended coatings are; base metal, chromium carbide or tungsten carbide. NASA tests were conducted using chromium carbide. Compressor & Turbine Services. LLC

Leakage Data Leakage Data. Compiled by various sources. Compressor & Turbine Services. LLC

Leakage Data From SST Test
4/16/2017 Leakage Data From SST Test Test comparing brush seals with cold (new) carbon seals Brush seals installed with “zero” clearance Carbon seals installed with 2.5 mil radial clearance Carbon seals exhibit equivalent clearance of 4.3 mils This is the result of air tests conducted with Brush Seals and Carbon Rings. The Carbon Rings were new The Brush Seals were an early prototype – split ring design Brush Seals were installed with “0” clearance. The effective clearance was 3.4 mils radial. Due to leakage through the bristles (required for cooling) Carbon Seals were installed with 2.5 mils radial clearance. The effective clearance was 4.3 mils. Several combinations were tested – Brushes alone, Carbons alone and combinations of carbons & brushes. A combination of Brushes and Carbons gave the best overall results. B = Brush Seal C = Carbon Seal

4/16/2017 Brush Seals vs. Carbon Rings Effective Clearance over Time Since Carbons rings begin deteriorating shortly after installation, their performance degrades dramatically over time. Brush Seals do not deteriorate. Compressor & Turbine Services. LLC

4/16/2017 Effective Clearance over Time Carbon seals will degrade almost immediately. Brush seal performance will always stay the same. The performance of Brush Seals stays consistent over time. Compressor & Turbine Services. LLC

4/16/2017 Brush Seals Two Approaches * Stand Alone Application * Brush/Carbon Combo There are two methods for using Brush Seals in Single Stage Steam Turbines. One is a stand-alone application. The other is a Brush/Carbon application. Compressor & Turbine Services. LLC

Brush Seals for Steam Turbines
4/16/2017 Brush Seals for Steam Turbines May be used as a replacement for Carbon Rings Or May be used in conjunction with Carbon Rings Brush Seals May be used as a replacement for Carbon Rings Or May be used in conjunction with Carbon Rings

4/16/2017 Brush Seals Stand-Alone Application Stand-alone application Compressor & Turbine Services. LLC

Application: Brush Seals to Replace Carbon Rings
4/16/2017 Application: Brush Seals to Replace Carbon Rings Non Floating Seals COST: Around $10k Per SST The cost to do a Brush Seal only system is around $10K. These seals were non floating. Three Brush Seals were installed on either side of the wheel. Cost do not include the line bore of the turbine. Compressor & Turbine Services. LLC

4/16/2017 Application: Brush Seals to Replace Carbon Rings More Risky Than Brush/Carbon Combination Since Brush Seals DO NOT Have a History for this Application. Only recommended for turbines that are in continuous service. (floating seals) Stand - alone Brush Seal applications are costly, roughly comparable to Dry Gas Seals. It is a riskier application since the system relies 100% on technology that does not yet have an established track record. A Brush/Carbon combination is like wearing a belt and suspenders. Adding carbons to the empty slots does not add much to the overall costs and does help to reduce pressure down the shaft. Compressor & Turbine Services. LLC

Application Requirements: Brush Seals as Replacement for carbon rings
4/16/2017 Application Requirements: Brush Seals as Replacement for carbon rings Drain Minimum radial space between shaft and packing box ID of 1.0 inch typically Maximum pressure drop across one seal is 150 psid Packing box must be reasonably aligned with bearings Best used on turbines that are in continuous operation The requirements to install Brush Seals in any application is the same as with most sealing systems. Note: Each Brush Seal is good for about 150#’s of pressure. So, several Brush Seals might be required. A Brush Seal is required on either side of the drain. (Non Floating, carbonless application) Brush Seals

4/16/2017 Split line Brushes Anti-rotation pin Sealing face This is a stand-alone Brush Seal installation. This is a split seal. Note the anti rotation pins. Application: Brush Seals to Replace Carbon Rings Non Floating Seals Compressor & Turbine Services. LLC

4/16/2017 Here is a side view. Elliott BYRHH Compressor & Turbine Services. LLC

4/16/2017 Flow No.1 Drain Pipe No.2 Another view showing the direction of the steam flow. There is a seal on either side of the drain hole. In later applications the last seal is placed before the bleed-off for improved performance. No.3 Compressor & Turbine Services. LLC

4/16/2017 Brush Seals - Used With Carbon Rings Brush Seals used in conjunction with Carbon Rings. Compressor & Turbine Services. LLC

4/16/2017 A More Conservative Approach This is a more conservative approach. Estimated around 100 turbines in operation with Brush Seals in this configuration. Compressor & Turbine Services. LLC

Brush Seals/Carbon Rings - A Winning Combination
4/16/2017 Brush Seals/Carbon Rings - A Winning Combination No case modifications beyond original design specifications. Lower sustained leakage than stand-alone carbon rings. Indefinite life span eliminating periodic replacement. Protects carbon rings from contamination Reduces pressure on carbon rings This is our preferred sealing system, a combination or Brushes and Carbon Rings. No case modifications beyond original design specifications. Lower sustained leakage than stand-alone carbon rings. Indefinite life span eliminating periodic replacement. Protects carbon rings from contamination Reduces pressure on carbon rings The CTS Brush Seal takes this approach a step further. Compressor & Turbine Services. LLC

Leakage Data From SST Test
4/16/2017 Leakage Data From SST Test Test comparing brush seals with cold (new) carbon seals Brush seals installed with “zero” clearance Brush seals exhibit equivalent clearance of 3.4 mils radial Carbon seals installed with 2.5 mil radial clearance Carbon seals exhibit equivalent clearance of 4.3 mils Once again tests indicate that a combination of Brushes and Carbons provide the best results. B = Brush Seal C = Carbon Seal

4/16/2017 COST: Around $ 3k – 6k This the latest evolution of the Brush Seal. The latest design incorporates many new features: It is a solid ring It is much lighter than its predecessors The brush pack is shorter and denser than previous versions. It is roughly the size of the carbon ring that it replaces It utilizes a garter spring or OD ring anti-rotation device that is identical in operation to the anti-rotation device on a standard carbon ring. Brush Seal cost for this application is approximately $3k Solid Ring Design Compressor & Turbine Services. LLC

Brush Seals Installation Considerations

Single Stage Turbine Brush Seal Benefits - When used with carbon rings
4/16/2017 Single Stage Turbine Brush Seal Benefits - When used with carbon rings Carbon rings Brush Seal used to protect carbon rings Protects carbons 1) by reducing steam pressure. 2) Reducing particulate contamination. One Brush Seal ring required upstream of carbons on both ends Brush Seals used in conjunction with carbon rings A single seal is installed upstream of the carbon rings on both packing boxes. This serves two purposes: the Brush Seal greatly reduces the amount of pressure that moves downstream thereby reducing stresses to the carbon Rings. The fact that the Brush seals indeed contain a brush pack makes the brush act as a filter to reduce particulates and contaminates that may move downstream and therefore add additional protection to the carbons. Compressor & Turbine Services. LLC

Single Stage Turbine Brush Seal Benefits - When used with carbon rings
4/16/2017 Single Stage Turbine Brush Seal Benefits - When used with carbon rings Carbon rings Brush Seal used to protect carbon rings Protects carbons 1) by reducing steam pressure. 2) Reducing particulate contamination. One Brush Seal ring required before the bleed-off. Brush Seals used in conjunction with carbon rings A Brush Seal is placed before the bleed-off to reduce pressure to the final carbon. Compressor & Turbine Services. LLC

4/16/2017 Our latest design – This is for an Elliott BYRH turbine. The Brush Seal is the same size as the carbon ring that it is replacing. It combines the best of both worlds – two carbon rings & one brush seal that fits in a single slot. Standard Brush Seal CTS Brush Seal Compressor & Turbine Services. LLC

4/16/2017 Single Stage Turbine Brush Seal Benefits To complement carbon rings No case modifications beyond original design specifications. Lower sustained leakage than stand-alone carbon rings. Increased run-time. Protects carbon rings from contamination Reduces pressure on carbon rings The benefits of a Brush Seal/Carbon Ring Sealing system: No case modifications beyond original design specifications. Lower sustained leakage than stand-alone carbon rings. Indefinite life span on Brush Seal eliminating periodic replacement. Protects carbon rings from contamination Reduces pressure on carbon rings Compressor & Turbine Services. LLC

4/16/2017 The Result is Reduced Maintenance Costs The benefits of a Brush Seal/Carbon Ring Sealing system: The result is – reduced maintenance costs. Reduced leakage will result in reduced oil contamination and longer operations between repairs. Compressor & Turbine Services. LLC

Our Sealing Systems

Brush Seals Designed & Manufactured at our facility
Light weight “floating” seal Available for Elliott “YR” turbines (and many others) Custom applications Our seals are designed and manufactured at CTS.

Early non floating Brush Seal
CTS Brush Seal Steel Cased Brush Seal Typical Carbon Ring Early non floating Brush Seal CTS Brush Seals are only slightly heavier than a standard carbon ring. The design consists of a brush pack sandwiched between two carbon rings.

Brush Pack Our seals are much lighter than those of the competition. CTS Brush Seals are lighter than traditional Brush Seals. In addition you have the benefits of two carbon rings and one Brush in each turbine slot. Eliminates the problems caused by heavier Brush Seals on turbines that cycle. Carbon

Support American owned small businesses!
Disrupter Seals Designed & Manufactured at our facility Superior design to reduce moisture in bearing housing Cost effective Disrupter seals provide better protection than standard seals. Support American owned small businesses!

Steam Bearing Turbine Case Oil Carbon Seals Steam
Disrupter seals are finned on one side, disrupting the steam flow and pushing is out and away from the bearing housing. In addition, the finned side of the seal has an increased OD compared to standard seals. This increases the centrifugal force, and pushes steam away from the shaft. We have also added an ID “O” ring to eliminate steam that might migrate down the shaft. Steam CTS “Disrupter” Seals deflect moisture away from the bearing housing by disrupting the steam that moves down the shaft.

Steam Leakage In Small Steam Turbines

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