Drums and HeadersDrums and Headers

Make up the highest and lowest parts of Make up the highest and lowest parts of the water and steam containing elements the water and steam containing elements in the boilerin the boiler

Steam DrumsSteam Drums

Function to accumulate the steam generated in Function to accumulate the steam generated in the tubes and to provide a space for the the tubes and to provide a space for the separation of moisture from the steam before the separation of moisture from the steam before the steam leaves the boilersteam leaves the boiler

Function to provide reservoir for the water Function to provide reservoir for the water required for proper operation of the boilerrequired for proper operation of the boiler

Function to receive and distribute to the Function to receive and distribute to the downcomers the feedwater required for the downcomers the feedwater required for the generation of steamgeneration of steam

Water DrumsWater Drums

Function to distribute water to the Function to distribute water to the generating tubesgenerating tubes

Function to provide a receptacle for the Function to provide a receptacle for the accumulation of scale and other solid accumulation of scale and other solid matter which may be present in or matter which may be present in or precipitate from the boiler waterprecipitate from the boiler water

DrumsDrums

Components of the DrumComponents of the Drum Wrapper Sheet (upper sheet of the steam Wrapper Sheet (upper sheet of the steam

drum and lower sheet of the water drum)drum and lower sheet of the water drum) Tube Sheet (lower sheet of the steam drum Tube Sheet (lower sheet of the steam drum

and upper sheet of the water sheet)and upper sheet of the water sheet) Drum Heads (welded to the ends of the drum Drum Heads (welded to the ends of the drum

and contains manhole covers for access to and contains manhole covers for access to the drum)the drum)

DrumsDrums

Steam DrumSteam Drum

Inside Inside DiameterDiameter 54”54”

Shell LengthShell Length10’ 8”10’ 8”

Thickness of Thickness of Tube SheetTube Sheet 4 11/16”4 11/16”

Thickness of Thickness of Wrapper Wrapper SheetSheet

1 ½”1 ½”

Water DrumWater Drum

Inside Inside DiameterDiameter 32”32”

Shell LengthShell Length 10’ 6 1/4”10’ 6 1/4”

Thickness of Thickness of Tube SheetTube Sheet 2 13/16”2 13/16”

Thickness of Thickness of Wrapper Wrapper SheetSheet

1”1”

DrumsDrums The boiler drums are constructed from a high The boiler drums are constructed from a high temperature steel alloy.temperature steel alloy.

Most drums are formed of two sheets of alloy Most drums are formed of two sheets of alloy steel which is rolled into a semi-circular shape.steel which is rolled into a semi-circular shape.

The lower sheet of the steam drums and the The lower sheet of the steam drums and the upper sheet of the water drums are called the upper sheet of the water drums are called the tube sheets.tube sheets.

These are rolled with an increase thickness to These are rolled with an increase thickness to provide extra strength where the holes are provide extra strength where the holes are drilled for the insertion of the generating tubes.drilled for the insertion of the generating tubes.

DrumsDrums The other half of the drum is called the The other half of the drum is called the wrapper sheet.wrapper sheet. The ends of the drums (drum head) and The ends of the drums (drum head) and headers are formed by forging.headers are formed by forging. The drum head has a central manhole to The drum head has a central manhole to permit access for inspection, cleaning or permit access for inspection, cleaning or repair.repair. These access openings are closed in These access openings are closed in while the boiler is in service by means of a while the boiler is in service by means of a manhole.manhole.

DrumsDrums

The wrapper, tube and drum heads are joined The wrapper, tube and drum heads are joined together by robotic electric arc welding.together by robotic electric arc welding.

Next the nozzles for the various fittings are Next the nozzles for the various fittings are hand welded.hand welded.

The drum is then given a radiographic (X-ray) The drum is then given a radiographic (X-ray) examination for welding defects.examination for welding defects.

The drum then treated in an annealing furnace The drum then treated in an annealing furnace to relieve stresses incurred during the various to relieve stresses incurred during the various fabrication operations.fabrication operations.

DrumsDrums After the annealing process is completed, After the annealing process is completed, a hydrostatic pressure test is made at one a hydrostatic pressure test is made at one and one half times the design pressure of and one half times the design pressure of the boiler (MAWP – Mean Allowable the boiler (MAWP – Mean Allowable Working Pressure).Working Pressure). If a defect in a weld appears it must be If a defect in a weld appears it must be ground out and be rewelded.ground out and be rewelded. The weld must then be X-rayed again, The weld must then be X-rayed again, heat treated and pressure tested once heat treated and pressure tested once more.more.

DrumsDrums

The holes for the tubes are then drilled The holes for the tubes are then drilled with special jig to obtain accurate with special jig to obtain accurate alignment of holes.alignment of holes.

After the holes are drilled, the is then After the holes are drilled, the is then reamed out to ensure the hole is circular reamed out to ensure the hole is circular as possibleas possible

DrumsDrums

DrumsDrums

Wrapper Sheet

Tube Sheet

Steam Drum Water Drum

Wrapper Sheet

Tube Sheet

DrumsDrums

Manhole Plate

Manhole Opening

DrumsDrums

Why is the steam drum a larger diameter Why is the steam drum a larger diameter then the water drum?then the water drum?

DrumsDrums

The steam drum contains a number of The steam drum contains a number of drum internals where the water drum may drum internals where the water drum may only contain a desuperheater.only contain a desuperheater.

The steam drum contains both water and The steam drum contains both water and steam where the water drum only contains steam where the water drum only contains waterwater

DrumsDrums

Lets look at a 600 psia boiler.Lets look at a 600 psia boiler.

The specific volume of water at 600 psig The specific volume of water at 600 psig is is ννff = 0.02013 ft = 0.02013 ft33/lbm/lbm

The specific volume of steam at 600 psig The specific volume of steam at 600 psig is is ννgg = 0.70843 ft = 0.70843 ft33/lbm/lbm

The expansion ratio is 35.19 to 1The expansion ratio is 35.19 to 1

HeadersHeaders

In some boilers headers are used instead In some boilers headers are used instead of water drums.of water drums.

The header serves the same function as The header serves the same function as the water drum.the water drum.

In general a drum is large enough so that In general a drum is large enough so that it can be entered by a man thru the it can be entered by a man thru the manholemanhole

HeadersHeaders

A header is smaller and access is A header is smaller and access is provided by means of hand holes and provided by means of hand holes and hand hole plates located throughout the hand hole plates located throughout the length of the header, so that the tubes can length of the header, so that the tubes can be inspected, cleaned and maintained, as be inspected, cleaned and maintained, as necessarynecessary

Type of HeadersType of Headers

Box type headersBox type headers

Sinuous type headersSinuous type headers

Circular type headersCircular type headers

HeadersHeaders

Headers are usually used with:Headers are usually used with:

Waterwall TubesWaterwall Tubes

Superheater TubesSuperheater Tubes

Economizer TubesEconomizer Tubes

HeadersHeaders

Waterwall Tube

Downcomer

HeadersHeaders

Handhole Opening

Handhole Plate

Gasket Seating Surface

HeadersHeaders

Dog

Spiral Wound Gasket