275560216 Boilers Inspection Ppt

BOILERS

SCOPE: This procedure is intended to give guidance to the plant inspector to check, evaluate, and asses the condition of the water tubes boiler components and recommend any necessary repair.

Function

>> The purpose of the utility boilers is to produce superheated steam for use in the process units. The primary source of boiler feed water is the clean condensate returned from steam users throughout the complex. The makeup water is from the process water after it has been Demineralized. Both the condensate and the Demineralized water enter the deaerators D-6003A/B before reaching the boilers. The maximum continuous rating of the boiler is 153 Ton/h. The normal operating temperature and pressure are 400 C and 4480 Kpag respectively.

MAJOR PARTS

Economizer: A heat exchanger which is used to recover the heat from the fuel gases which otherwise would be lost up to the stack. It is used to preheat the feed water of the boiler. The economizer consists of spiral fin tubes connected to two headers lower and upper. The boiler feed water enters the economizer through the lower header and the preheated water enters the steam drum from the upper header. The economizer has two set of manholes for cleaning and inspection.

Forced Draft Fan : A fan supplying air under pressure to the fuel burning equipment.

Induced Draft Fan : A fan exhausting hot gases from the heat absorbing equipment.

Furnace/Fire Box An enclosed space provided for the combustion of fuel.

Mud Drum A drum at the bottom of the boiler which is connected to the steam drum by the vertical bank tubes. The drum is also connected to the furnace wall tubes. Inside the drum, an intermittent blowdown pipe is fixed along the drum bottom with 6 mm holes to remove any deposits from the drum.

Steam Drum: A drum at the top of the boiler which is connected to the mud drum by the vertical bank tubes. The drum is also connected to the furnace wall tubes. The drum contains chevron dryers that are installed at the top to remove the moisture.

Strainer Metal screen with small openings to retain solids and particles in fuel media which could detrimentally affect the operation of the burners.

Superheater The superheater is a convection type and it consists of three set of bank tubes secured to two headers by weld joints. It is installed between the screen tube zone. The saturated steam from the steam drum is superheated through the three pass superheater.

Wind box A chamber below the grate or surrounding a burner, through which air under pressure is supplied for combustion of the fuel. One type called a burner wind box which is a chamber around a burner in which an air pressure is maintained to ensure proper distribution and discharge of combustion air.

SILENCERS Two silencers to be checked in the boiler, one is the start-up Vent Silencer, and the second is the PSV Silencer for the normal operation.

Stack

Burner

REFERENCES API, Guide for Inspection of Refinery Equipment, Chapter VIII- Direct-Fire Boilers and Auxiliary Equipment, Second Edition 1974. API 510, Pressure Vessel Inspection Code, Maintenance, Inspection, and Alteration, Seventh Edition 1992. ASME, Boiler and Pressure Vessel Code, Section I, Power Boilers, Edition 1992. ASME, Boiler and Pressure Vessel Code, Section VIII, Recommended Guidelines For the Care of Power Boilers, Edition 1992.

BOILER INSPECTION

>> According to ASME standard section I and VIII, Boiler has to be inspected annually. API Chapter VIII does not specify any inspection interval. From YANPET experience it has been decided that the boiler shall be down for inspection every two years. There are two types of inspection, during operation and during outage inspection.

DURING OPERATION INSPECTION

>> The inspection during operation should be done to ensure that the outside surface and parts are in good opera table condition. It also to ensure no leaks, hot spots, corrosion, nor settlement are exist. The external inspection may be done during the operation of the boiler, however, the main foundation and supports of the fire box shall be done during the boiler outage.

FOUNDATIONS >>The important of foundation can not be overemphasized. Any overlook of the foundation deterioration might lead to equipment bearing failures, refractory failures, steam leaks and.....etc. Tapping the concrete with a hammer will reveal deterioration or unsound conditions. Foundation should be checked for:

A)- Settlement, which is caused by water wash or high vibration. Settlement of the foundation can be detected by cracks in the concrete, brick walls and adjacent flooring. Surveyor’s level or transit or transparent hose water level can be used to check the settlement. Boiler manufacturer often put level marks on drums or other parts that can be used to check settlement.

B)- Spalling, usually caused by excessive heat, mechanical shock, the corrosion of reinforcing steel. C)- Cracks, in concrete which may be caused by excessive heat, poor design material, mechanical shock, or unequal settlement. D)- Soundness of the anchor bolts.

LADDERS, STAIRWAYS, PLATFORMS & WALKWAYS >> The ladders, stairways, platforms, and walkways should be checked carefully by visual inspection aided with light hammering and scraping the oxide scales and other corrosion products. They should be checked for:

•Cracks. •Broken parts. •Tightness of bolts. •Wear of ladder rungs and stair treads. •The condition of the platforms flooring. •Corrosion beneath painted surfaces which will be indicated by rust stain or blistering.

PIPING

The piping and their connections are items may be affected if any vibration, settlement, earthquakes, and fire damages occur to the boiler. They should be checked for: •High vibration. •Leaks. •Cracking at weld joints. •Defective coatings and insulation. •Distortion or any deterioration. •Metal loss. •Corrosion.

INSULATION The insulation and cladding of the boiler components is considered as one of the major items that it should be in good condition, due to the fact that any defect or loss of insulation will cause loss of heat and may subject personnel to heat burns. The insulation should be checked for: •Hot spots, may indicate hidden defects in the insulated parts. •Un-secured parts of cladding. •Sign of leaks, may indicate a hidden problem. •Deterioration and general defects.

AUXILLARY EQUIPMENT

Auxiliary equipment, such as gauges connections, sight glasses, and safety valves may be inspected visually for: •Undue vibration. •Corrosion and breakage. •General deterioration.

DURING OUTAGE INSPECTION Inspection will be carried out when the boiler is out of service either in planned shutdown or an emergency shutdown. The emergency shutdown usually in short period of time, therefore, complete inspection could be difficult. However, it is considered a good chance for checking the critical areas and/or the areas with previous problems. Before starting internal inspection, the results of the recent external inspection and the previous internal inspection should be used as a guide for the current internal inspection, e. g. a hot spot on the casing indicate a refractory failure.

CONTINUATION: A preliminary inspection of the inside of the boiler shall be carried out before the boiler is cleaned. The location, amount, physical appearance, and analysis of mud and sludge or scale deposited on the inside of tubes and drums will provide information relative to the effectiveness of the feed water treatment, blowdown operation and method of cleaning needed. The preliminary inspection may also be helpful in determining which part of tubes or drums require close inspection.

FIRE BOX The fire box (furnace) is the main and major component of the boiler. The fire box is constructed of water wall tubes backed up by firebricks ( refractory), block insulation and steel plate casing. The fire box should be inspected internally by checking the following items visually and/or by using any of the NDT methods. TUBES:

All tubes should be checked for : • Blistering and Bulging. • Cracks.

•Bowing and Sagging. •Corrosion. •Deposit that will effect the heat transfer. •Metal loss, may be done by checking the wall thickness of the tubes using Ultrasonic as per 7.1. •Soot and dirt shall be removed and area below it should be inspected. •Overheating. •Tube may be x-rayed to check the internal deposit and wall thinning.

All the tubes should be inspected for signs of overheating, corrosion, and erosion. Usually overheating is caused by deposits or excessive scale on the water side of the tube. The nearest tubes to the burners are susceptible to overheating and should be closely examined for bulging, blistering, quench cracking, sagging and bowing. Blistering and bulging is easily accomplished by shining a flashlight parallel to the length of the tubes so that bulges or blisters will cause shadows.

The locations of the thickness measurements shall be identified, so next shutdown the readings will be taken in the same locations for comparison.

REFRACTORY The refractory should be inspected for: •Cracks. •Erosion. •Melting. •Bulging. •Fall down.

Cracks in the refractory are common and are to be expected but if the cracks is severe, then repairs should be made. If the erosion and melting are present, then the refractory has to be carefully evaluated before putting the boiler back into service. Metal shell and insulation behind the refractory will become overheated if these defects remain unchecked.

BURNERS All burners should be checked for: •Corrosion. •Erosion of tips. •Burning and Melting. •Spalling. •Cracks. •General deterioration.

STEAM DRUM The drum should be inspected internally for: •Seam welds cracks. •Corrosion. •Pitting. •Grooving. •Scale deposits and sludge accumulation in shell and tubes. •Tightness. •Deterioration. •Soundness. •Structural stability. •Metal loss

MUD DRUM

The mud drum (water drum) should be checked for: •Corrosion. •Pitting. •Grooving. •Cracking. •Scale, deposits, and accumulation of sludge in shell and tubes. •Metal loss as

Special attention should be paid to all seam welds and should be examined for cracks and corrosion. Corrosion adjacent to the seam weld is more serious than a similar amount of corrosion in the solid plate away from the seams. Cracks along the seams is likely to occur when the material is highly stressed.

SUPERHEATER

The superheater should be checked for: •Corrosion and paint defects. •Signs of leaks. •Cracks at weld joints. •Wall loss of headers and tubes, thickness check to be taken in fixed points as per •Melting, burning, and/or heat damage to the internals. •Sign of insulation and refractory deterioration at the walls. •General damage or breakage.

ECONOMIZER

The economizer should be checked for: •Corrosion and paint failure. •Cracking at weld joints. •Signs of leaks. •Wall loss of header and tubes, thickness check to be taken in fixed points. •Damage to the structural and vane plates. •Tightness of bolts and clips of header and tubes. •Security and cleanness of vents.

BANK TUBES CHANGER

The bank tubes chamber should be checked for: •Corrosion and paint failure. •Cracking at weld joints. •Signs of leaks. •Wall loss as per •Damage to the structural and vane plates. •Tightness of bolts and clips of header and tubes.

SIDE WALL TUBES

The side wall tubes should be checked for: •Corrosion and paint failure. •Cracking at weld joints. •Signs of leaks. •Wall loss

WIND BOX AND F.D. FAN

They should be checked for: •Corrosion and paint failure. •Erosion due to ash particles. •Thinning and holes in the fan blades. •General deterioration. •Damage of the louvers near the burners. •Any damage, deterioration, or paint failure on the burners visible parts

STACK

The stack should be checked for: •Refractory damage •Corrosion on the stack metal parts. •Erosion. •Overheating. •External Paint damage.

STRAINERS

Two strainers for the gas and the diesel fuel to be checked in the boiler shutdown. They are located at the top platform in the inlet lines to the boiler. They should be checked for: •Breakage in the screen. •Heavy deposit. •Corrosion. •Foreign materials. •Deterioration in the screen or the body

VALVES

During the boiler shutdown, there are two valves to be checked, one is the boiler feed water non-retaining valve and the other is the superheater non-retaining valve. They should be checked for: •Erosion. •Cracking in the seat and seat ring. •Corrosion. •General deterioration.

SILENCERS

Two silencers to be checked in the boiler, one is the start-up Vent Silencer, and the second is the PSV Silencer for the normal operation. The smaller one is for the start-up. They should be checked for: •Corrosion internally or externally. •Cracking in the weld joints or the body. •Deterioration in the internals. •Damage to the connecting fittings. •Corrosion or deterioration of the inlet piping.

LUBE OIL COOLER The cooler usually opened during the scheduled boiler shutdown for cleaning and inspection. It should be checked for: •Tube plugging. •Corrosion. •Erosion in the channel, covers, or heads. •Cracks or damage. If leak is suspected, the cooler should be hydrotested from the shell side to 1.5 times the design pressure of the shell and observe any leaks through the tubes, this test should be done when all covers and heads are removed.

THICKNESS MEASUREMENTS The thickness measurements shall be taken at several locations (Attachment III) at the boiler as follows: FIRE BOX: All four sides of the wall tubes shall be covered by the thickness check at fixed locations. The thickness shall be checked at 1.5 M. from the floor on the following selected tubes: NORTH WALL: 12 tubes, first 4 from east, 4 tubes at the middle (tube no. 58 to 61), and the last 4 tubes at the west side (tube no. 116 to119).

CONTINUATION: SOUTH WALL (SCREEN & BAFFLE TUBES): 3 screen tubes at the middle section (tube no. 7 to 9). 9 baffle tubes, first three at east side, 3 at the middle (tube no. 51 to 53) and the last 3 tubes at west side (tubes 102 to 104). WEST WALL (BURNER SIDE): 4 tubes, 2 tubes at the center (tube no. 8 and 9) of both north and south sections.

EAST WALL (MAN-WAY SIDE): 9 tubes, first 3 tubes at North corner and 3 tubes (tubes no. 22 to 24) at the center and the last 3 tubes at south corner (tubes n0. 45 to 47).

STEAM DRUM: The thickness shall be checked on the steam drum at the following locations:

HEADS: Both heads shall be checked at 3,6,9 and 12 O’clock positions. SHELL: The shell shall be checked at the top and the bottom sections and the thickness shall be checked `at three locations, east, middle and west sides. The top section shall be checked from outside.

MUD DRUM: The thickness shall checked on the mud drum at the following locations:

HEADS: Both heads shall be checked at 3,6,9 and 12 O’clock positions. SHELL: The shell shall be checked at the top and bottom sections in three locations, east, middle and west sides.

CONTINUATION: SUPERHEATER: The thickness shall be checked on the superheater at the following locations:

TOP CHAMBER: TUBES: 1 tube in each of the east, middle and west banks, tube no. 1 counting from east of each bank. HEADER: 3 locations, east, middle and west.

BOTTOM CHAMBER:

TUBES: 1 tube in each of the east, middle and west banks, tube no. 1 counting from east of each bank. HEADER: 3 locations, east middle and west.

ECONOMIZER: The thickness shall be checked on the economizer at the following locations: TOP CHAMBER: TUBES: 1 tube in each of the east, middle, and west sides (tubes no. 1, 17 and 30 counting from east) of both south and north ends.

CONTINUATION: HEADER: 3 locations east, middle and west side plus one point at the bottom side of each branch. BOTTOM CHAMBER: TOP SECTION TUBES: 1 tube in each of the east, middle and west sides (tubes no. 1, 22 and 30 counting from east) of the north end. BOTTOM SECTION TUBES: 1 tube in each of the east, middle and west sides (tubes no. 1, 22 and 30 counting from east) of the south end.

CONTINUATION: BANK TUBES CHAMBER: The thickness shall be checked on 1 tube in each of the north, middle and south sides (tubes no. 1, 17 and 23 counting from north) at 1.5 M from the floor.

SIDE WALL TUBES: All 6 tube shall be checked, one point each.

HYDROSTATIC TEST >> After completing the inspection, the boiler shall be hydrostaticly tested to a pressure equal to 1.5 times the maximum allowable working pressure (MAWP), thus the testing pressure shall be 8826 KPaG. The pressure shall be increased gradually, max. 300 KPaG per minute and shall be held for at least 30 minutes. Then the test pressure shall be reduced to the MAWP, 2746 KPaG and shall be maintained at this pressure until the Inspector certify that there are no leaks or other apparent defects.