1. Keep Feedwater soft.
2. Maintain proper blowdown (bottom, continuous, and water columns).
3. 1 Boiler Horsepower = 34.5 pounds of steam production/hr. 1 gallon of water = 8.34 pounds of steam.
4. Test representative samples of make up, soft water, feedwater, boiler, and condensate.
5. Record pressures, temperatures, pump and controller settings, and feed rates.
6. Know percent blowdown, percent return condensate and steam production.
7. Maintain proper treatment levels: Appropriate Conductivity / TDS, Hydroxyl Alkalinity (OH) > 200 PPM, Condensate pH 8.3 – 8.9, Sulfite (SO3) 30 – 60 PPM.
8. Establish testing and treatment procedures, train operators, and keep daily logs.
9. Know the operating characteristics of equipment (softeners, DAH, boilers, etc.) under treatment.
10. Have full knowledge of, communication with, and training of operating, supervisory, and management personnel.
One of the most effective ways of increasing the efficiency of your boiler operations is to find ways of increasing the amount of condensate returned to be used as feedwater for the boiler. The quality of steam condensate, in most cases, is so good that increasing the amount of return can lead to a significant reduction in boiler blowdown. This reduction addresses one of the efficiency-robbing, necessary evils of boiler operation.
The more condensate that is returned to the feed tank or deareator, the more dilute the feedwater conductivity. Consequently, less blowdown for conductivity control is needed. As a result of less blowdown, fewer treatment products are required. Additionally, the quality of condensate is such that it usually requires less treatment than an equal amount of make up. Finally, as less blowdown occurs, the demand for make up and thermal input goes down as well.
In most cases, an added benefit of increased return condensate is a gain in thermal efficiency due to the fact that, many times, condensate being returned to the system is much hotter than make up water and will require less input to raise the feedwater to the boiling point. Hotter feedwater will also reduce the amount of sulfite required for the removal of dissolved oxygen. This is a function of the natural release of dissolved gasses as the temperature of the water is increased.
Are you returning all of the condensate that is practical? Are you relatively sure of the average return condensate percentage of your system? Determining the average return condensate is a straight forward process. Water Quality Test Results that are already being performed by your Water Treatment Consultant are used for this determination.
You should also keep in mind that although your system may have been designed to return all available steam condensate, through the years there my have been some modifications or changes to the system that could be robbing you of efficiency.
Absorption Air Conditioning
1,000 Btu/cu. ft.
832 lbs/100 lbs.
10,000 lbs/100 gals.
70 lbs/100 cu. ft.
1.0MM lbs/400 ton
H2SO4 produced 17.5 lbs/hr/Ton of Refrigeration
Black Furnace Gas
Coke Oven Gas
80 – 100 Btu/cu. ft.
11,000 – 14,000 Btu/lb.
450 – 650 Btu/cu. ft
975 – 1,100 Btu/cu. ft.
During the years we have spent in the Water Treatment business, it has become apparent that many cases of “apparently” dirty boiler come from poor shutdown techniques – not inadequate treatment.During normal operations, the boiler water chemistry is carefully controlled so that the dissolved/suspended material is conditioned to prevent hard deposits on boiler metal. These dissolved/suspended solids are maintained in suspension by water circulation and the action of the treatment chemicals.
When a boiler is shut down or drained, this material (sludge) may settle and bake on tube surfaces; it may become so adherent that mechanical (turbining) chemical cleaning may be required. At worst, there are large piles of sludge in the mud drum and in the lower tube ends which cause the customer and/or boiler inspector to feel that the deposits developed during operation, and thus unjustly criticize the treatment program. Outlined below is a procedure that if followed will minimize the total amount of sludge left behind when a boiler is opened.
1. Three to five days before a scheduled shut down, increase the blow down by 50%.
a. If possible, increase the alkalinity to at least 500 ppm. Go as high as possible without causing foaming or carryover.
b. Due to the increased blowdown rate, the feed rate of the scale inhibitor and oxygen scavenger must be increased so as to maintain the normal boiler water residuals.
c. If possible, increase the sludge conditioner level in the boiler water by 50 to 100%.
2. During the last twenty-four hours before shut down, decrease the continuous blowdown and increase the manual blowdown.
a. Frequent short bottom blows are better than fewer longer blows.
b. Generally it is sufficient to hold each mud drum blowdown valve open for about 5-10 seconds every one to two hours.
c. Once the load is dropped from the boiler, include the header blowdowns as part of the manual blowdown procedure.
3. When the load is dropped from the boiler, continue bottom blowdowns until boiler is cool and safe to work on.
4. As soon as possible after the boiler is opened, wash down the boiler watersides, preferably with soft water.
Following this procedure will ensure that the boiler watersides will be ready for inspection and no unwarranted criticisms of the operation or maintenance of the Boiler Water Treatment Program will occur.
1. Non-condensable gases are frequently overlooked when investigating dry steam problems from a low pressure (i.e. less than 300 psig) boiler. Such boilers, when proper Water Treatment is used, will always produce a saturated (wet) steam.
2. Non-condensable dissolved gases (Oxygen & Carbon Dioxide) that accumulate in a steam header will result in a dry or low pressure superheated steam. Thus, even though the steam has the desired temperature, it is very low in moisture content. This dry steam condition can cause failures in such processes as the manufacturing of corrugated packaging and the pelletizing of animal feed.
3. To maintain saturated steam, you need to be sure of the following:
4. Operate the deaerating heater at saturation conditions (i.e. equal or above 215° F and at 3 – 5 psig).
5. Feed neutralizing amine to the boiler or steam header so that condensate pH is maintained in the range of 8.3 – 8.8.
When boilers are taken out of service for any length of time, corrosion may occur on the internal surfaces of the boiler unless certain precautions are observed. During periods of idleness, boilers may be laid up by one of two methods described below. The choice of method is dependent on how long the boiler is to be out of service, and how quickly the boiler may be required back in service for regular steaming purposes in an emergency, etc.
The DRY METHOD:
The dry method is preferable when a boiler is to be out of service for a month or more and will not be required for emergency purposes. This boiler should be drained, thoroughly cleaned, and carefully inspected to ensure all is in good order. The boiler should then be thoroughly dried internally by means of hot air stoves or a light wood fire. Close attention should be given to complete drying of non-drainable super heater tubes.
Use of Quick Lime:
An amount of quick lime, approximately 30 pounds for each 100 boiler horsepower, should be spread on water-tight wood trays placed in the boiler immediately after the drying-out process. If the boiler is an HRT or locomotive type, a single tray resting on top of the flues or in the bottom of the shell will be adequate. In a multi-drum water tube boiler, a tray should be placed in each drum. The manheads, handholes, and all connections on the boiler should be tightly blanked or closed after the lime has been placed in position. If the boiler is idle for a considerable period, it should be opened every 3 or 4 months for examination and renewal of the quick lime, if necessary.
Use of Silica Gel:
Absorbents such as silica gel can be used in dry storage. Before use of the absorbent, the boiler should be prepared as outlined above. Silica gel may be obtained in convenient packages to permit good distribution. The packages of silica gel should be placed on wood or metal trays and distributed throughout the boiler. Approximately 4 pounds of silica gel should be used for each 100 cubic feet of air space.
If the boiler is idle for a considerable period of time, it should be opened every 3 or 4 months and the silica gel examined. If necessary, the silica gel can be reactivated by placing it in an oven for several hours or by blowing hot air through it until moisture is no longer given off.
The WET METHOD:
The wet method should be employed if boilers must be left idle with water in them, prepared for emergency service if required. The boiler should be thoroughly cleaned and carefully inspected to ensure all is in good order. Do not use wet method if boiler will be exposed to freezing temperatures.
Use of Caustic Soda and Sodium Sulfite:
After the boiler is filled to the normal water level, the water should be boiled, with the boiler properly vented to the atmosphere for a short time. This procedure is necessary to expel dissolved gases such as oxygen from the water. The water should then be made alkaline in excess of 400 ppm by the use of caustic soda (approximately 3 lbs. of caustic soda per 1,000 gallons of water in the boiler). In addition, sufficient sodium sulfite should be added to boiler water to produce a minimum sulfite residual of 100 ppm (approximately 1.5 lbs. of sodium sulfite per 1,000 gallons of water in the boiler). After the boiler has cooled somewhat, but before a vacuum is created, the boiler should be filled with deaerated water. Filling should be sufficient to completely fill the superheater elements and headers with treated water. This can be determined by testing the overflow water from the superheater outlet for sulfite and alkalinity. After filling, all connections should be tightly closed. It is desirable to leave a small positive pressure in the boiler to prevent a vacuum from developing as the unit cools to room temperature.
The boiler water should be tested at weekly intervals. Additional caustic soda and sodium sulfite should be added as necessary to maintain the recommended concentrations. When additional chemicals are added, the boiler water should be circulated by means of an external pump or by reducing the water level to the normal operating level and steaming the boiler for a short time. The boiler should then be completely flooded as outlined above.
When the boiler is returned to service, the manufacturer’s operating instructions should be followed concerning firing rate and boiler water out of non-drainable superheater tubes.
However, boiler out flooded superheater elements leaves a residue of soluble salts. After several such boil-outs, the superheater tubes should be individually washed with water to remove the salt deposit. Sufficient blowdown should be provided during start-up to reduce boiler water alkalinity to the normal operating range.
In operation, boiler water contains suspended solids (or mud) which are held in suspension by water circulation and the action of treatment. Unless care is exercised when draining, these suspended solids settle out on the boiler surfaces and air dry to an adherent deposit, sometimes requiring turbining of the boiler. In addition, unless the deposits are examined carefully, it may be assumed incorrectly that the deposits are scale which formed during operation. Therefore, in order to judge the effectiveness of the water conditioning program, as well as to eliminate unnecessary boiler cleaning, proper care is imperative during shutdown.
For a period of three (3) to seven (7) days before shutdown, manual blowdown should be increased. During this period, the lower conductivity or chloride limit should be observed as a maximum. The feed of internal treatment must be increased to maintain specific residuals. Continuous blowdown should be kept to a minimum so the reduction in solids is achieved by increased manual blowdown.
If it is necessary to use a draw-and-fill method for cooling, the pressure should be lowered, and cooling should be at the rate recommended by the boiler manufacturer. Care should be taken to maintain recommended treatment balances during this process. Feedwater should be deaerated.
Immediately on draining the boiler, the manhole or manholes should be knocked in and a high pressure hose employed to wash out sludge. By this procedure, the sludge is removed while still in a fluid form.
If the boiler cannot be washed immediately on draining, heat in the boiler setting may cause baking of residual sludge. The boiler should not be drained until cool. However, never leave the boiler filled with water for any extended period of time without taking measure to prevent corrosion and pitting.
A properly operating steam trap rids a steam line of condensate. Unfortunately, we often see a needless waste of condensate from steam traps which have been bypassed because they are not operating properly. More often than not, the failure of a steam trap is the result of improper installation rather than a mechanical failure. In some instances, the condensate discharge and the steam trap discharge are installed in such a way that the condensate cannot readily flow from the system. This can cause the system to become water logged.
These are some suggestions regarding problem steam traps:
1. Make sure the steam trap is properly rated for the application.
2. Make sure the discharge/condensate line is free of obstructions.
3. Uphill runs of steam trap discharge can result in head/back pressure on the trap. If condensate needs to be moved up or overhead, a condensate collection tank pump should be used.
Although not intended to be all inclusive, this article might give you some steam trap insight and experience from another perspective.