Waste Heat Boiler Preparation (Courtesy of Rentech Boiler Systems Inc.)

Hydrostatic Testing

The equipment has been hydrostatically tested to a minimum of 1½ times the design pressure, in the factory, and copies of the Manufacturer's Data report, signed by the Authorized Inspector witnessing and evidencing the test has been forwarded to all jurisdictional bodies as well as to the Client. However, the complete system, along with all interconnecting piping, should be hydrostatically tested before start-up to comply with code requirements and to check for leaks that may have occurred during shipping and handling. This test should be completed under the supervision of and witnessed by an Authorized Inspector who should represent the State or municipality having jurisdiction or the insurance company covering the installation. At the option of this inspector, the hydrostatic test may be at 1½ times the design pressure of the equipment, or at a pressure slightly less than the setting of the lowest safety valve. The latter test will avoid the necessity of blanking or gagging of safety valves, removing piping and plugging various pipe openings, removing controls and gage glasses, etc

The boiler and process lines must be completely vented in order to fill them with water. The following is a recommended procedure for hydrostatic testing:

1. Open the steam drum vent valve and gag the safety valves in accordance with safety valve manufacturer's recommendations. In lieu of gagging, the safety valves may be removed and replaced with test plugs or blind flanges.
2. Open the vents on the interconnecting piping. Close steam outlet valve.
3. Isolate pressure switches, gauge glasses or control components that are not intended to be subjected to a hydrostatic test.
4. Fill the system with treated water in accordance with recommendations from the Clients water treatment consultant. (Refer to section entitled "Water treatment Considerations" on page 11. The test water temperature range must be 70°F minimum to 120°F maximum (100°F to 120°F water temperature is preferred). Care should be taken so that all air is vented while the equipment is being filled. Fill the equipment until water overflows the vent, then close the vent.
5. Apply pressure slowly. The recommended rate of pressure increase is less than 50 psi per minute. Proper control must be maintained so that pressure does not exceed the desired setting of the local steam boiler inspecting agency. Do not subject any pressure part to more than 1½ times the design pressure rating of any component.
6. When the proper test pressure is reached, inspection in accordance with the test objective can begin. Examine the system for any leaks. If no leaks are visible, hold the system in a pressurized static condition for a period long enough to satisfy the code requirement.
7. Upon completion of the test, release pressure slowly through a small drain valve. Then fully open vents and drains when the pressure drops to 20 psig. Particular Care must be given to make sure that parts not normally containing water during Operations are drained free of water. The system should be drained fully after hydrostatic testing, to prevent freezing, if the unit is installed in a cold weather area, and to minimize corrosion of the metal surfaces.
8. If temporary handhole or manway gaskets were used for the test, they should be replaced with regular service gaskets before readying the unit for operation. Gaskets should never be reused. Replace gage glass if necessary and make sure that the gage cocks are open. Remove all blanks or gags from safety valves and install relief valves, if removed.
9. Additional inspection at this time by the Authorized inspector will determine whether the installation including piping arrangements, valve gauges and controls and other equipment on the unit meets Code and/or other jurisdictional requirements.
10. Refer to the "Summary of valve positions" on page 11 for recommended positioning of the various valves during hydrostatic testing.

Refractory Dry-Out Procedure

Many waste heat boilers include a refractory lining at the hot gas inlet end. The refractory material was not normally thermally cured at the factory. It is not uncommon for moisture to be absorbed by the refractory during final stages of in-shop fabrication, transit to the job site, and before the upstream combustion products are first passed through the unit. Therefore, residual moisture and any absorbed moisture must be removed after installation but prior to commencement of start-up operations. Otherwise, trapped moisture will steam, causing cracking, and in many cases, the refractory will separate from the metal in large pieces. As a minimum, follow these steps to protect the refractory from damage.:

1. Ideally, the refractory lining should be air-set in dry air, preferably not less than 70°F for at least 24 hours.
2. Using treated water (normal boiler feedwater) fill the unit to approximately the midpoint of the gauge glass, which is normal water level.
3. Verify that the feedwater system is operational.
4. Warm the furnace and gas chamber of the unit to 200°F and maintain that temperature for six hours.
5. Raise the inlet gas temperature at 100°F per hour to 500°F, while venting the generated steam to atmosphere. The valve positions are similar to the boil-out condition given in the "Summary of Valve Positions" on page 11.
6. Hold the furnace at this temperature for a minimum of two hours.
7. Continue to raise the inlet gas temperature at 100°F per hour to 1,000°F.
8. Hold the furnace at this temperature to the anticipated operating level at a rate not exceeding 50°F per hour.
9. Elevate the furnace at this temperature to the anticipated operating level at a rate not exceeding 50°F per hour.
10. Hold the furnace at this temperature for a minimum of two hours.
11. Remove the heat source and allow the refractory to cool by natural radiation. Do not introduce cold air with a fan.

Boil-Out Procedure

 The internal surfaces of a new boiler contain deposits of residual oil, grease and protective coating inherent in manufacturing procedures. It is important that these deposits be removed from the heating surfaces since this contamination will lower the heat transfer rate and possibly cause overheating of pressure vessel metal. These deposits can generally be removed by an alkaline boil-out using readily available chemicals. If during operation internal surfaces become contaminated by these deposits. Before boil-out procedures can begin, the boiler should be ready for firing and the operator must be familiar with the operation of the burner and follow instructions contained in the manual. The operating conditions of all auxiliary equipment and instrumentation should be formally checked out. Be sure that auxiliary equipment not supplied by RENTECH Boiler Systems, Inc. is of adequate size and pressure to ensure proper operation.

Check for proper voltages, fuses, and overloads. Check rotation of all motors by momentarily closing the motor starter or relay. Check the reset of all starters and controls having the manual reset feature. To the extent possible all operating mechanisms, valves, and dampers should be checked for evidence of operation and freedom from binding. Check the settings of all controls.

Before operating a boiler feed pump or an oil supply pump, be sure that all valves in the line are open or properly positioned and that all strainers are clean. Be certain that pump rotation is correct. If in doubt, remove the coupling and check motor rotation. Some pumps can be severely damaged by even a momentarily reversed rotation. Also recheck the coupling alignment.

For safety's sake, make a final and complete pre-startup inspection especially checking for any loose or uncompleted piping or wiring or any other situation that might present a hazard.

The boil-out chemicals shown in figure 1 are intended to serve as only a general guide. It is strongly recommended that the Client retain a water treatment consultant with expertise in the field of industrial boiler water chemistry to select the boil out chemicals and be available to provide consulting direction as required. There are specially prepared trademarked chemicals available. Some firms that manufacture and provide these are:

• Betz Laboratories
• Dow Chemical company
• Halliburton
• Nalco Chemical Company

The instructions and advice provided by the manufacturer of the chemical should be followed. In the event the boil-out is not handled by a water consultant company the following is a recommended boil-out procedure that may be followed:

1. If the unit is furnished with prismatic type gage glass, replace it with the temporary boil-out glass to prevent chemical attack on the operational gage glass.

2. Remove all manway and/or handhole covers to verify that tubes and nozzles are not plugged with foreign materials.

3. Unbolt steam drum girth baffle sections and stack them within the drum to permitexposure of the tube ends to boil-out solution.

4. Wire brush any heavy scale on drum surfaces and vacuum out.

5. Close all inspection openings such as manways, handholes, etc.

6. Select the chemical mixture to be used:

A. If using a commercially prepared product, follow the manufacture's directions for concentrations and mixing. The chemicals are normally available from water treatment consulting companies in quickly soluble briquettes or liquid.

B. It is preferred to mix a solution at the job site, any one of the four combinations of chemicals shown in Figure 1 have proven satisfactory. The mix concentrations are for typical guidance only, actual chemical concentration and combinations should be established by a water treatment consultant. A good quality household or commercial detergent may be added to the boil-out mixture selected. Add the detergent at a rate of ¼ pound of detergent to 1000 pounds of water. The chemicals should be dissolved prior to placing them in the unit. To make the solution, place warm water into a suitable container. Slowly introduce the dry chemical into the water, stirring at all times, until the chemical is completely dissolved.

7. Fill the boiler to the lower visibility level of the water gauge glass.

8. Blow-off valves, drain valves, and gauge cocks should be examined and closed. Be sure that vent lines are piped to outdoor locations for indoor units.

9. Add the chemical and water mixture to the unit slowly and in small amounts to prevent excessive heat and turbulence. Admit the mixture through the chemical feed or feedwater connections to a level just above the bottom of the gauge glass.

10. Verify proper operation of the gauge glass by opening the gauge glass drain. If no liquid runs out, the obstruction blocking the flow must be removed. If liquid drains out, close drain valve. This is a caustic solution, avoid contact with it!

11. Purge the flue gas passages, with air, in accordance with the burner manufacturer's recommendations or at least for five minutes.

12. While purging, verify that the valves are positioned in accordance with the Summary of Valve Positions on page 11.

13. Fire the boiler at a very low firing rate to limit the flue gases entering the boiler to a maximum of 800°F. Alternately, introduce 5 psig steam from an outside source through the blowdown nozzles.

14. When the boiler begins to produce steam (as seen though the open vents), allow the unit to steam freely for at least four hours. Watch the level in the gage glass and always maintain normal water level (midpoint of the gage glass). It will be necessary to add more boil-out solution when the water level falls.

15. Close all vents.

16. Hold drum steam pressure at 5 to 10 psig while maintaining water level near the midpoint of the gauge glass. Adjust heat input as required to maintain this pressure.

17. After eight hours, increase drum pressure to 20% of anticipated operating pressure by increasing the firing rate.

18. Continue boil-out for at least forty-eight hours. During this period, open the intermittent blowdown valve and drain an amount of solution equal to one-half of the gauge glass every eight hours. Then refill the unit to the midpoint of the gauge glass with the boil-out solution.

19. If at the end of forty-eight hours the blowdown is not clean continue the boil-out for an additional eight-hour cycle, continue this cycle until the blowdown is clean.

20. When blowdown is clean, remove the heat source, and allow the unit to cool gradually.

21. Drain the boiler when water temperature drops below 200°F. The water and chemicals must be disposed of in accordance with local, state, and EPA \ guidelines. Draining the fluid into storm sewer may not be acceptable.

22. Remove the inspection covers, flush the system with treated water at least three to four times.

23. Inspect pressure parts internally. If any remnant oil is found, repeat the boil-out procedure.

24. Remove the temporary gauge glasses, and replace with the normal service gauge glass. Replace manway covers and install new gaskets.

25. Take the necessary precautions to protect boiler internal surfaces from corrosion by utilizing the appropriate lay up procedure in section entitled "Standby Protection" on page 19.

System Contamination

Steam and water piping systems connected to the unit may contain oil, grease, or foreign matter. In new systems, the piping usually has an accumulation of oil, grease, and dirt. Old systems have an additional hazard in that the piping and receivers may be heavily limed and full of scale as a result of improper water treatment. These impurities must be prevented from entering the unit. On a steam system the condensate should be wasted until tests show the elimination of undesirable impurities. During the period that condensate is wasted, attention must be given to the treatment of the water used as make up so that an accumulation of unwanted materials or corrosion of materials does not occur.

If oil, dirt, and scale accumulations are permitted to get into the boiler system, it may be necessary to repeat the boil-out procedure. The waterside of the pressure vessel must be kept clean from grease, sludge, and foreign material. Such deposits, if present, will not only shorten the life of the pressure vessel and interfere with efficient operation and functioning of control or safety devices, but might possibly cause an unnecessary and expensive re-work, repairs and down time. The waterside should be inspected on a periodic basis, which will serve as a check against conditions indicated by chemical analysis of the boiler water. Inspection should be made three months after initial starting and at regular 6, 9, or 12 month intervals thereafter.

The frequency of further periodic inspections will depend on the internal conditions found.

Summary of Valve Positions

Valve Hydro Boil-Out Start-Up Operation CORRECT THIS TABLE XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Steam Shut-Off Close Close Open Open

Steam Stop/Check Close Close Open Open

Drum Vent Close Close Open²² Close

Feedwater Regulator Close Close Close Open

Regulator Isolation Close Close Close Close

Regulator Bypass Open Open²³ Open²³ Close

Intermittent Blowdown Close Intermittent Close Intermittent

Continuous Blowdown Close Close/Open Close Open

Chemical Feed Close Close/Open Close Open

Water Column Drain Close Close Close Close

Water Gauge Drain Close Close Close Close

Safety Valve Gag Free Free Free

Steam Gauge Shutoff Close Open Open Open

Water Treatment Considerations

For prolonged boiler life, a water treatment program recommended by a water consultant is a must. Steam boilers are sensitive to even minor deposits on tube walls. Therefore, most feedwater treatment programs are oriented toward scale control. However, internal corrosion control cannot be ignored. Scald with locally high caustic concentrations can develop on metal components, strip away the protective magnetite film, and attack the base metal. This attack is characterized by gouging of the metal and its severity is directly proportional to increasing operating pressures.

Oxygen is highly corrosive when dissolved in water, and can result in corrosion pitting of heat transfer surfaces. Mechanical deaeration of the feed water using a deaerator is the typical first step in eliminating dissolved oxygen and other gases such as ammonia and carbon dioxide. Mechanical deaeration will reduce oxygen to as low as 0.005 cc/liter. In boilers below 1,000 psig, the oxygen-scavenging chemical is fed continuously, preferably at the storage compartment of deaerator or at suction of boiler feed pump, to provide turbulence and time for mixing. Specification of chemicals and dosages should be in accordance with the recommendations of the Owner's water consultant.

Generally, a total water treatment program should pursue the following four-point goal:

1. Maintenance of free caustic corrosion potential, accomplished by eliminating free hydroxide (caustic) though the addition of various phosphate salts.
2. Minimize caustic deposit formation due to scale and suspended solids by chelation and sludge conditioners so that blowdown will remove this potential problem.
3. Eliminate oxygen content through deaeration or other mechanical means and chemical scavenging.
4. Prevention of carryover and foaming.

The accomplishment of these objectives generally require treatment before and after introduction of water into the boiler. The selection of pre-treatment processes depends upon water source, chemical characteristics, amount of make-up water needed, plant operating practices, etc. These treating methods include filtering, softening, demineralizing, deaerating, and preheating.

After-treatment involves the addition of chemicals into the boiler water. This after-treatment is required to compensate for any variations in the pre-treatment of the boiler feedwater system and to assure the ultimate protection of the boiler. Because of the variables involved, no one "boiler compound" can not be considered a cure-all, nor is it advisable to experiment with homemade treating methods. Sound recommendations and their employment should be augmented by periodic analysis of the raw water, boiler water, and condensate.

Feedwater Quality Limits

The ABMA specifies limits, as listed in Figure 5, for boiler water composition with respect to operating pressure to assure good quality steam. While there are other considerations (such as corrosion and deposit formation) in establishing boiler water composition, the limits indicate that requirements for feedwater purity become more stringent as operating pressure increases.

Notes:

1. Actual values within the range reflect the TDS in the feedwater. Higher values are for high solids, lower values are for low solids in the feedwater.
2. Actual values within the range are directly proportional to the actual value of TDS of boiler water. Higher values are for high solids, lower values are for low solids in the boiler water.
3. Dictated by boiler water treatment.
4. These values are exclusive of silica.
5. Expressed as equivalent calcium carbonate in PPM.

Figure 5: ABMA Boiler Quality

Improper and nonexistent feedwater treatment is the major factor causing boiler failure, which ultimately results in boiler down time and costly repairs. All fresh water available from natural sources requires varying degrees of treatment prior to use in a boiler. The impurities in fresh water ware many and each required special attention. Solids in the form of minerals, chemicals, and organic material are all found in fresh water and all have a different effect on the internal surfaces of a boiler.

Boiler feedwater treatment by a competent water treating company will result in prevention of scale and deposits, removal of dissolved gases (free oxygen), protection against corrosion, elimination of carry-over of water with steam, maximum boiler efficiency, and maintenance savings. It is imperative that the Owner contacts a company specializing in boiler feedwater treatment and obtain their recommendation and service.

Failure to heed the above warning will cause excessive damage to the boiler. It will be very costly to repair this damage to the boiler and place it back in proper condition. The warranty does not cover this type of maintenance. This is the Owner's responsibility.

Suggested Start-Up

It must be recognized that all boilers and auxiliary equipment require operator attention during start up. Special care must be exercised in the manipulation of feedwater and fuel systems to protect against damaging the unit and to insure personnel safety.

Check and close the manual blow-off valves, the continuous blowdown valves, the gage cocks and the water column and gage glass drain valves. Open the drum vent valve, the water column shutoff valves (if provided), the gage glass shutoff valves and the steam pressure gauge valve.

The unit should be slowly filled with properly treated feedwater using the level control valve bypass valve. The filling rate depends on the temperature of the feedwater. The feedwater should be as close as possible to the metal temperature to prevent excessive temperature stresses that could cause tube leakage. The minimum recommended feedwater temperature is 70°F. Fill slowly and vent fully to prevent any pressure buildup from the flashing of warm feedwater. The level should be set and manually maintained at just below the normal water level so that there is room for expansion when water is heated. Blowdown the gauge glass and observe the return of liquid to insure that the glass is clear and functioning properly.

When the unit is filled and the level is stabilized, start the purge cycle of the combustion controls as specified by the combustion equipment manufacturer. Allow adequate time to completely purge the entire boiler, duct work, etc.

The drum vent valve should be initially open to vent generated steam while purging air from the system. Close the steam drum vent at 15 psig. (Refer to table entitled "Summary of valve positions" on page 11).

The start-up rate of the boiler is limited by the following items:

1. Allowable heat up rate of refractory, to achieve acceptable refractory life.
2. Elimination of temperature stress that could cause leaking tube joints.
3. If sulfur or HCI is present in normal fuel effluent, start the heating process on clean fuel until the dewpoint is passed.

During this period of operation, carefully observe that all components function properly. Be prepared to shut the unit down should a lack of proper operation become evident. Visually observe combustion conditions for proof that gauges, meters, and other instrumentation are properly reporting operating conditions.

Maintain the normal water levels at all times. The level can be maintained by hand feeding or by blowing down as necessary. Too high a level will render the separators ineffective and cause water carryover in the steam, while too low a level will allow possible overheating of pressure parts. If the water level is not visible, firing should have been stopped automatically and the reason for the low water determined. The feedwater control valve should be cut in when the operating pressure is obtained and then the bypass valve should be closed.

If the unit is tied into a main steam line with other units and there is pressure downstream of the not-return valve, then the system must be brought up to slightly above that operating pressure. The steam stop valve can then be opened to permit flow through the non-return valve. Re-check inspection openings, fittings and piping connections for leaks, tighten as required to insure proper gasket seating. Always maintain proper water treatment as recommended by the Owner's water consultant.

Suggested Operating Guide

The following is a suggested operating guide for safe and reliable operation of the unit. Routine monitoring of the controls and safety systems by the operator is imperative.

Water Levels

The water level must be continually checked whether the feedwater system is operated automatically or when an operator is in attendance. Proper water level in the steam drum must be maintained at all times. High water level can result in damage to internal separation equipment with a corresponding reduction in separation efficiency. This will result in water carryover and mineral deposition inside the downstream components. If the water level reaches too low a point, the unit is in danger of overheating with possible catastrophic damage. If the level is automatically controlled by the feedwater regulator, it should be adjusted per the manufacturer's recommendations so that the level remains stable near the centerline of the gauge glass.

The water column and water gauge glass should be drained once at the beginning of each shift. This will insure that sludge or sediment will not have a chance to accumulate in the column or gauge glass and can cause an erroneous level indication. The boiler attendant, by observing drained liquid and return of liquid to glass, will be assured of proper actuation of one of the most important safety devices of the unit. Daily testing of level alarms and low water cutoff is also recommended.

Boiler Water Blowdown

Boiler water blowdown is done to remove some of the concentrated water from the pressure vessel while it is under pressure. The removed water containing suspended and dissolved solids is replaced with relatively pure feedwater even though this water is treated prior to use through external processes designed to remove the unwanted substances which contribute to scale and deposit formations. Regardless of their high efficiency, none of these processes in themselves are capable of removing all substances and a small amount of solids will be present in the boiler water. The solids become less soluble in the high temperature of the boiler water and as the water boils off as relatively pure steam, the remaining water becomes thicker with either suspended or dissolved solids.

Internal chemical treatment, based on water analysis, is used primarily to precipitate many of the solids and to maintain them as "sludge" in a fluid form. This sludge along with suspended solids that may be present must be removed by the blowdown process. If the concentration of solids is not lowered through blowdown but rather accumulates, foaming and priming will occur along with scale and other harmful deposits.

The scale forming as salts tend to concentrate and crystallize on the heating surfaces. Scale has a low heat transfer value. It acts as an insulation barrier and retards the heat transfer. This not only results in low operating efficiency and consequently higher fuel consumption, but also presents the possibility of overheating the boiler metal. The result can be tube failures or other pressure vessel metal damage.

There are two principal types of blowdown, they are intermittent and continuous. Intermittent is done manually and is necessary for the operation of the boiler regardless of whether or not continuous blowdown is employed. Continuous blowdown is a continuous and automatic removal of concentrated boiler water.

Intermittent Blowdown

The manual blowdown valve and discharge lines are located at the bottom or low point of the blower. This also provides a means of draining the boiler when it is not under pressure. The intermittent blowdown should be opened fully for a short duration (approximately 10 to 20 seconds), at least once per shift thus insuring proper removal of accumulated solids that have settled out in the mud drum. In cases where the feedwater is exceptionally pure, blowdown may be employed less frequently since less sludge accumulates in the pressure vessel.

Frequent short blows are preferred to infrequent length blows. This is particularly true when the suspended solids content of the water is high. With the use of frequent short blows, a more uniform concentration of the pressure vessel water is maintained. Blowing down is most effective at a time when the generation of steam is at the lowest rate since the feedwater input then is also low, providing a minimum dilution of the boiler water with low concentration feedwater.

It is recommended that the blowdown valve nearest the boiler be opened first and closed last, with blowing down being accomplished by the valve furthest from the boiler. The sequence of operation once established should insure that the valve last opened should be the first closed so that the other valve is saved from throttling service to insure a tight closing. The downstream valve should be cracked slightly to allow the discharge line to warm up, after which this valve opened slowly. Quickly close the downstream valve tightly, then close the valve next to the boiler. The frequency and amount of each blow should be determined by actual water analysis.

The water level should be observed during periods of intermittent blowdown. If the glass cannot be viewed by the person operating the valve, another operator should watch the glass and direct the valve operator. The blow-off valves should never be left open and the operator should never leave until the blowdown operation is completed and the valves closed. Be sure the valves are shut tight. Repair any leaking valves as soon as possible.

Continuous Blowdown

The boiler is equipped with an internal continuous blowdown pipe. The collector pipe is located several inches below the normal water level, at a point where the most concentrated water is found. A manual controlled metering valve is normally utilized to control the flow of concentrated water. Periodic adjustments are made to the valve setting to increase or decrease the amount of blowdown and water testing. Proper monitoring and maintenance of appropriate water conditions in the boiler are mandatory to assure long term integrity of the boiler.

The amount of water lost through a continuous surface blowdown is usually considerably less than the water lost through bottom blow-off in order to remove a given amount of suspended solids. The amount of blowdown depends upon the rate of evaporation and the amount of sludge forming material in the feedwater.

Foaming or priming may occur in the steam drum and cause large quantities of water to pass over into the steam lines. It can be detected by violent fluctuations or sudden dropping of the water level in the gauge glass. This trouble may be caused by dirt or oil in the boiler water, an overdose of treatment chemicals, carrying too high a water level in the steam drum, or excessive rates of change of evaporation. In case of serious trouble, decrease the load on the boiler, then alternately blowdown and feed fresh water several times. If foaming does not stop, cool, empty, and wash out the boiler and refill with fresh, treated water. Any problem in regard to extreme foaming or priming, scale in boiler, corrosion or pitting, should be referred immediately to a company specializing in boiler water chemistry consulting. Do not experiment with "home-made" treatment chemicals.

Saturated Steam Sampling

When a new sample line is being put into service, flow steam and condensate thought it for 24 hours before the samples are collected. Before the sampling period, blow steam though the sample line to remove any material that may have been deposited. Adjust the flow rate to that desired during sampling and flow the sample at this rate for one hour or longer before conductivity measurements are recorded before a sample is collected for other methods of analysis.

When samples of condensate are collected for evaporative analysis, the flasks or other types of containers should be meticulously cleaned prior to use. Borosilicate glass is a satisfactory material for such containers but they should be aged to by allowing them to stand for several days full of distilled water. This aging of borosilicate glass may be hastened by a preliminary treatment with dilute caustic soda (ten grams/liter). Containers fabricated from suitable metals or plastics may also be used.

Samples should be analyzed as soon as possible after collection. After use, the flasks should be rinsed with hydrochloric acid. These flasks should be reserved and used for no other purpose than steam samples. When the condensed sample is to be analyzed by the electrical conductance method, cool it to 25°C. When dissolved gases are to be determined, cool the sample to 20°C or lower.

Suggested Shut-Down

When the unit is taken out of service, good care of the boiler during the idle periods is mandatory to prevent unnecessary corrosion damage. Gradually reduce load and run the fuel system to low fire position. When the unit is at the low fire position, blow down the boiler along with water column gage glass and the feedwater control valve. Following manufacturer's recommendations, remove from service all combustion equipment. The until is to be post purged with the fan for at least 5 minutes and then allowed to cool on natural draft after removing the fan from the service.

The steam pressure should be allowed to drop naturally without opening vents or other intentional means of taking steam from the unit to hasten the lowering of steam pressure. A cooling rate exceeding 100°F per hour to 150°F per hour by excessive opening of vents should be avoided to limit the drum distortion and resulting strains on tube joints. Vents can be fully opened when the steam pressure drops to 15 to 20 psig. Close the stop valve on the steam line and open the drain (if provided). When the steam pressure has dropped to approximately 20 psig, open the drum vent valve to prevent a vacuum from forming within the boiler. The boiler is drained only after the water temperature drops below 200°F.

To insure that the safety valves are maintained in good working order they can be hand lifted or popped at periodic intervals. It is recommended that the valves be lifted just prior to a planned boiler shutdown, as a check to determine whether repair work is necessary.

When removing a boiler from service for storage, inspection or cleaning the circulation of water ceases. This causes suspended solids in the water to settle out on the boiler surfaces, cake and dry to an adherent sludge, which can be mistaken for scale during normal operation.

Standby Protection

Many boilers used for heating or seasonal loads or for standby service may have extended periods of non-use. Special attention must be given to these, so that neither waterside or fireside surfaces are allowed to deteriorate from corrosion. Corrosion can be more serious during this down time than when the boiler is actually in service. The key factors responsible for corrosion are water, oxygen, and pH. Elimination of either moisture or oxygen will prevent appreciable corrosion.

Two types of storage systems are widely used; these are wet and dry storage methods. Wet storage is adopted for short duration lay up and dry storage is used for shut downs exceeding approximately 30 days. No unit should be wet-stored when the temperature could drop below the freezing point.

In situations where the boiler is "headered" with other steam generating units it may be possible to maintain the boiler in idle storage by means of treated blowdown water or steam flooding from an operating unit. If these alternate lay-up methods are considered feasible the Owner should assure that his water treatment consultant firm has reviewed the water chemistry aspects of the alternate method and agreed to it's implementation as a means of protecting against corrosion.

Wet Storage

1. As the boiler is being shut down and as the pressure subsides, but before steaming stops, add chemicals to the boiler to scavenge oxygen and to control pH, per the recommendations of the Owner's water treatment consultant.
2. When the boiler pressure gauge indicates about 10 psig completely flood the system with deaerated treated water with the drum vent open. Close the drum vent after it begins to overflow. The steam stop valve should already be closed. Water should be added through the feed pump until 10 psig is maintained as indicated by the drum pressure gauge.
3. Close the feedwater valves. Observe the steam drum pressure gauge and maintain pressure. If pressure builds, it may be due to leaking feedwater valves, which may not be properly seated. A pressure loss (after the boiler is cool) indicates leakage, so check all fittings and valves for leakage.
4. Frequent water samples should be taken and analyzed by the water treatment consultant. If the analysis indicates a need for additional chemicals, the level in the boiler steam drum should be lowered to normal level and chemicals added. The boiler should be then be steamed to circulate the solution, and the process of wet storage repeated as previously described.
5. Close all gas side access doors. Isolate the system to prevent cold air from reaching the heating surface. Periodic inspections of the external surfaces of the pressure parts should be made to guard against condensation and subsequent corrosion.
6. During storage, steps should be taken to protect the exterior components from the possibility of rust or corrosion. These parts should be coated with a rust inhibitor and protected from moisture and condensation. Electrical equipment should likewise be protected. Keeping the control circuit energized may prevent condensation from forming in the control cabinet.

Dry Storage

1. When the unit will be idle for a considerable length of time and a short period can be allowed to prepare the boiler for return to service, the dry storage method is recommended.
2. The unit should be cooled down and then completely drained. Make sure that no pockets of water remain in the drum, piping, water column, etc. Open all vents to assure complete drainage.
3. Open all the manways and thoroughly wash the water side surfaces to remove any sludge deposits. Mechanically clean residual particulate from the gas side metal surfaces and inspect the system thoroughly.
4. Dry the system thoroughly. If an air hose is used, be sure condensate from the air tank is not blown into the tubes and that the air is oil free.
5. Place flat wooden trays of moisture absorbent, such as quick lime or silica gel, inside the drums to absorb any moisture that will be trapped when the unit is closed up. The trays should be placed on supports to allow air to circulate under them. For recommendations on quantity of moisture absorbent, the Owner's water consultant should be contacted. The trays should not be more than 3/4 full of the dry absorbent to prevent overflow of the corrosive liquid that has been absorbed.
6. After the entire system is dried the boiler system should be pressurized with nitrogen to approximately 5 psig though the drum vent. Close the steam outlet, drain valves, and feedwater block valves. Ensure that the system has been purged completely before pressurizing.
7. Close all the openings to prevent water, steam or air leakage into the unit. Leave open the code required drain valve between the process steam stop valves to prevent back-leakage of condensate from any downstream header that may be pressurized.
8. Isolate the boiler to prevent moisture from reaching the heating surface.
9. Keep the boiler room dry and well ventilated to reduce possible surface corrosion.
10. If it is suspected that moisture cold have been absorbed by the refractory, follow the refractory dry out procedure found on page 6.

Care must be taken to remove all of the moisture absorbing material before any attempt is made to refill the boiler. Serious damage can result otherwise. As a precaution it is recommended that warning signs be conspicuously posted, such as:

Maintenance Requirements

General Maintenance

A well-planned maintenance program avoids unnecessary down time or costly repairs. It also promotes safety and aids boiler code and local inspectors. An inspection schedule listing the procedures should be established. It is recommended that boiler room log or record be maintained, recording daily, weekly, monthly, and yearly maintenance activities. This provides a valuable guide and aids in obtaining boiler availability factor to determine shutdown frequency, economies, length of service, etc.

Even though the boiler has electrical and mechanical devices that make it automatic or semi-automatic in operation, these devices require systematic and periodic maintenance. Any "automatic" features do not relieve the operator from responsibility, but rather free him from certain repetitive chores, providing him with time to devote to upkeep and maintenance.

Good housekeeping helps to maintain a professional boiler room appearance. Only trained and authorized personnel should be permitted to operate, adjust, or repair the boiler and its related equipment. The boiler room should be kept free of all material and equipment not necessary for operation for the boiler.

Alertness in recognizing unusual noises, improper gauge readings, leaks, signs of overheating, etc., can make the operator aware of developing malfunction and initiate prompt corrective action that may prevent excessive repairs or unexpected down time. All piping connections to the system and its accessories must be maintained leak-proof because even a minor leak, if neglected, may soon become serious. This applies especially to the water gauge glass, water level control, piping, valve packing, and manway gaskets. If serious leaks occur shut down the boiler immediately and gradually reduce steam pressure. Do not attempt to make repairs while the boiler is under pressure.

Shift Maintenance

Shift maintenance should include checking the boiler water level in the gauge glass and the boiler steam pressure on the gauge. Operate the intermittent blowdown valve to remove any accumulated solids in the mud drum. The valves on the water column and gauge glass should be operated to make sure these connections are clear. Monitor water chemistry to adjust the chemical feed treatment and continuous blowdown as required, to remain within water treatment guidelines established by the Owner's water treatment consultant.

Daily Maintenance

Daily Maintenance should include a check of the burner operation, including fuel pressure, atomizing air or steam pressure, visual appearance, etc. Clean the observation ports during periods of low fire or shutdown. Test the boiler level alarms and low water cutoff. Maintain a daily schedule of sootblowing.

Monthly Maintenance

Check the condition of the refractory for significant damage or cracking. Patch and repair the refractory as required. Frequent wash coating of refractory surfaces is recommended. Use high temperature bonding, air-dry type mortar diluted with water, to the consistency of light cream, for this purpose. This will seal small cracks and prolong the life of the refractory. Any large cracks should be cleaned out and filled with mortar.

Follow the recommendations of you authorized inspector pertaining to safety valve inspection and testing. The frequency of testing, either by the use of the lifting lever or by raising the steam pressure, should be based on the recommendation of your authorized inspector. Test the boiler safety valves in accordance with the manufacturer's instructions to be absolutely sure that the valves have not corroded shut. Failure of the relief valves in an overpressure situation is DISASTROUS!

Annual Maintenance

Have the unit inspected and checked by a RENTECH Boiler Systems, Inc. service representative.

Clean both the heating and heated sides of the boiler. Remove all manway and handhole covers. Open all bottom blowdown and drain valves. Hose the inside of the boiler with clean water under high pressure. Use a hand scraper to remove accumulated sludge and scale. Start near the top and work toward the bottom. After cleaning tube exteriors, inspect the tube surfaces for signs of overheating, such as bulging, blackened surfaces in the tubes, etc.

Specific local conditions determine the use of "wet" or "dry" storage during shutdown periods. If you are unsure of which procedure to follow, contact the Owner's water treatment consultant or your local insurance company.

Annual Inspection

Insurance regulations or local laws will require a periodic inspection of the pressure vessel by an Authorized Inspector. Sufficient notice is generally given to permit removal of the boiler from service and preparation for inspection. This major inspection can often be used to accomplish maintenance, replacements, or repairs that cannot easily be done at other times. This also serves as a good basis for establishing a schedule for annual, monthly, or periodic maintenance programs.

While this inspection pertains primarily to the waterside and fireside surfaces of the pressure vessel, it provides the operator an excellent opportunity for detailed inspection and check of all components of the boiler including piping, valves, pumps, gaskets , refractory, etc. Comprehensive cleaning, spot painting or re-painting and the replacement of expendable items should be planned for and taken care of during this time. Any major repairs or replacements that may be required should also, if possible, be coordinated with this period of boiler shutdown. Replacement spare parts, if not on hand, should be ordered sufficiently prior to this shutdown.

Have available information on the boiler design, dimensions, generating capacity, operating pressure, time in service, defects found previously, and any repairs or modifications. Also have available for reference records of previous inspections. be prepared to perform any testing required by the inspector including hydrostatic testing of the equipment.

Safety Manual

General

This documentation does not replace the Owners existing company safety operating procedures and instructions. All normal safety precautions should followed when operating boilers, burners, and fuel systems. Consult the Owners plant operating and safety authorities for complete details. In addition to the categorized hazards shown in the various sections of this manual, there are general type categories, which need emphasis:

Manufacturer's Instructions - Equipment manufacturer's instructions should be followed.

Training - Employees must be trained in safety prior to operation of the equipment. The training in safety should be a continuous process for the purpose of educating employees to recognize and to keep safety in their minds throughout their careers. A training program should be established and maintained.

Housekeeping - Good housekeeping is essential for safety and good plant operation. Poor housekeeping results in increased safety hazards. A clean and orderly environment will foster safety.

Clothing and Protective Equipment - Proper clothing should be worn at all times. Avoid loose clothing and jewelry. Protective equipment must be worn when necessary (i.e.: hard hats, respirators, ear plugs, goggles, gloves, safety shoes, etc.). Never operate rotating equipment, mechanically automated devices, or electrically and pneumatically operated control components unless guides, shields, or covers are in place.

Hot Surfaces - Many hot surfaces exist in a boiler area and even non-heated surfaces can become uncomfortably warm, therefore, employees, especially new employees, must be made aware of these conditions. Refractory and insulation are typically provided to encounter elevated surface temperatures in some installations. Care must be exercised to prevent burns and other thermal hazards when near the boiler. Never enter the boiler until an adequate cool-off period has been observed and the Owner's entry procedures have been completed.

Lockout and Tagout Procedures - Every plant should have a formalized lockout and tagout procedure that is strictly enforced.

Remote Starting of Equipment - Much of the equipment in plants are started remotely and/or automatically without warning; therefore, employees must be alert to avoiding that equipment which can be started remotely. If work is to be done on any equipment, lockout and tagout procedures must be followed. Attach signs to equipment such as "DO NOT START - MEN AT WORK". Attach a similar sign on the equipment control panel.

Unexpected Noise - A sudden and/or unexpected noise may cause employees to move involuntary. Such reaction may result in injury. Precautions against this are hard to take out but experience probably is the best teacher to prevent such inadvertent responses.

Unconventional Fuels - Sometimes unconventional fuels need to be burned in boilers. When this is done, particular attention should be paid to the hazards that can result. Theses may from characteristics in the fuels, toxic chemicals in the fuel, and toxic chemicals produced through combustion. Persons knowledgeable in the use of such unconventional fuels should be consulted concerning the problems that may be encountered. Because of the wide variety and limited use, such fuels are not addressed in this manual.

Fire and Explosion Hazards - A fired boiler utilizes fuels which are flammable and potentially explosive. Extreme care should be exercised when making fuel-piping connections. Use the correct gasket, bolts, thread lubricants, and tightening torque to prevent leaks. It is recommended that drain valve and/or vent piping be channeled to safe locations. Valve packing should be periodically tightened and a rigorous leak check program be implemented as part of the Owner’s preventative maintenance program.

Electrical Hazards - Potentially hazardous voltages exist in control cabinets and electrically actuated control components. These components should only be serviced when system power is removed and only by qualified electrical or instrumentation servicemen.