filename : C:\WINDOWS\ \ALSTOM OMM\SECT04 - Cond Instal Instruct

Installation and Removal of Condenser Tubes

Read the entire procedure before attempting to install or remove tubes.

The standard practice for installation of tubes in a surface condenser is to expand (roll) the tubes into the tube sheet at both ends. The inlet end of the tube is flush with the tube sheet face and the outlet end of the tube is flush or projecting beyond the tube sheet face.

The tube expanders are self-feeding, straight roll types. Each consists of a tapering mandrel, collar, rollers and roller frame. Each expander embodies a movable stop collar design, which permits it to be adapted to tube sheets of varying thick nesses. The collar of the expander has a flat or flush face so that after rolling, the end of the tube is flush with the face of the tube sheet. The rolls are set in the roller frame at an angle to the expander mandrel or central shaft. No pushing or forcing of the expander mandrel is necessary. All that is required is to rotate the mandrel. The rolls, being set at an angle, will pull the mandrel resulting in an automatic feeding action. To withdraw the expander at the end of the expanding operation, it is only necessary to reverse the direction of rotation. The rolls will then automatically eject the mandrel and the whole expander may be withdrawn from the expanded tube.

Under-expanded tubes may slip in their holes and give trouble from leakage. On the other hand, the over-expanded tubes are necked or grooved and may crack in service. Under expanding is easy to correct. Over-expanding cannot be corrected.

The first step to take before expanding any tubes is to set the expander stop collar at the proper position. This is accomplished by loosening the stop collar set screw and screwing up the stop collar to the desired position. The distance from the face of the collar to the beginning of the radii on the expanding rollers should be 3.2mm less than the thickness of the tube sheet. In exceeding this dimension, there is a possibility of belling the tube beyond the tube sheet making tube removal very difficult and creates an area of high stress concentration, which could result in premature tube cracking. In expanding a tube, the roller frame sometimes called the expander housing containing the rolls, should be inserted entirely into the tube end, the mandrel being held out as far as possible during this part of the operation. Then with the expander stop collar held firmly against the tube sheet, the mandrel should be slipped forward into a snug position and the expander drive started.

During the actual expanding operation, the expander stop collar should be held firmly against the tube sheet from start to finish. At the same time, the expander mandrel should be held perpendicular to the tube sheet. The latter precaution is necessary to assure a correctly expanded tube and to minimize mandrel breakage.

To reduce wear and breakage of the mandrel and rollers, expanders should be kept well lubricated and free of chips, during the expanding operation. To lubricate the expanders, place a lubricant such as Lube-A-Tube into the end of the tube.

Lubrication should be repeated at approximately every 10 or 20 tube ends. Likewise, if chips or scale collect on the rolls, the expanders should be dipped into kerosene as often as required to keep the rolls and mandrel clean.

The inlet end of the tube should be expanded first. After this is completed, the outlet end is expanded.

After the tubes have been inserted in the condenser, preparatory to expanding any of them, the inlet end of each tube should be set flush in the tube hole. Expand using the expander with the flush collar. During the expanding operation, the end of the tube will tend to flow outward slightly between .4mm and .8mm depending on the hardness of the tube and meet the edge of the tube hole radius. This flowing action of the tube metal should occasion no alarm because it is due to the normal extruding action of the worked tube metal.

The following points will sum up briefly the instructions to be followed during the Installation of the tubes:

1. Start with the inlet tube ends.

2. Set the inlet tube ends flush with the face of the tube sheet before starting the

expanding operation

3. Set each expander stop collar for the correct depth of expansion.

4. Insert roller frame into tube end, then follow up with expander mandrel. Hold stop

collar firmly against tube sheet from start to finish of expanding operation.

5. Hold mandrel perpendicular to tube sheet at all times.

6. Do not press or force mandrel. The expander does not require action of this kind.

7. Do not expand the tube ends hard enough to produce a neck or ridge.

8. Lubricate the expander frequently during the operation. Lubrication prevents tube

ends from flaking, becoming grooved by expander, and keeps mandrel smooth

and true.

9. Clean expanders when necessary to remove chips.

Before expanding any tubes, review the following:

"Expanding (rolling) tubes"

Expanding (Rolling) Tubes

This procedure describes the steps required to expand (roll) tubes into tube sheet holes.

The necessary equipment (torque control drivers, expanders and lubricants) can be purchased From Air tool Co., Elliott Co. or T.C. Wilson Co. If the supplier is given the number of tubes, tube materials and tube O.D. and gauge, they will be able to specify the type and quantity of equipment required. The supplier should also be advised that the tubes will be flush on the inlet ends and that the outlet ends may extend beyond the face of the tube sheet.

Automatic torque controls are available for both air and electric drives. Be sure there is an adequate air supply for air-powered tools. This supply should be through a separate direct line from the air compressor; do not use air from a line serving various other activities.

Before rolling the tubes, each torque controlled expander drive must be calibrated. Since each individual tube O.D., I.D. and tube plate hole diameter varies within tolerances; it is necessary to measure these parameters to calculate the as rolled I.D. using the following formula:

"As rolled " ID = I.D.t + (I.D.h-O.D.t) + (O.D.t-I.D.t) % wall reduction

Where I.D.t = tube I.D.

O.D.t = tube O.D.

I.D.h = tube plate hole I.D.

Sample calculation for a O.D25.4 x 1t tube and 10% wall reduction

Where I.D.h = 25.81 mm

O.D.t = 25.4 mm

I.D.t = 23.4 mm

"As rolled" ID = 23.4 + (25.81-25.4) + (25.4-23.4) .10

= 24.01

"As rolled" ID for that particular hole and tube is 24.01 mm

Recommended % wall reduction:

7% - 9% for copper based materials only

6% - 8% for all other materials

3% - 5% where the chief method of providing joint strength is welding.

Before calibrating the expander drives and actually rolling any tubes, tube holes and tube ends must be clean and dry. The expander rolls must be set to a depth of 3mm from the back face of the tube sheet, (see attached drawing).

Note: It is important not to roll the tubes deeper than the T-3mm dimension, where T is the thickness of the tube sheet.

After calculating the "as rolled" I.D. the tube should be rolled with the torque controller set at the manufacturer's suggested setting for the conditions. The "as rolled" I.D. is measured and compared with the calculated value. If they are equal, the tool is properly set. If they differ, the calculation must be repeated for another hole and torque limit reset according to the first run. (It is imperative that tubes be rolled within the specified tolerance.) Once a setting gives the proper "as rolled" dimension, it is used to roll any tubes under-rolled during the torque setting procedure and to roll the remaining tubes in the unit. Torque setting procedure should be repeated after approximately 300 tube ends have been rolled. For units with more than one tube material, or with different tube gages, a new torque setting will be required for each. A different torque setting is required for the inlet end and the outlet end, where the inlet tube hole has a flare.

After all the inlet tube ends are expanded, the outlet tube ends may be expanded. Since the outlet tube ends may protrude past the face of the tube sheet, a full recessed collar expander must be used. Be sure that the recess on the collar is deep enough to accept the longest protrusion of a tube beyond the tube sheet.

Removing Tubes

For removing expanded tubes, utilize a piloted tube reamer, which is applied to both ends of the expanded tube. This tool reams out the internal bore of the tube for a distance equal to the tube sheet thickness, leaving only a thin tube wall or shell confined by the tube hole. A tube driver is then used in driving out the expanded tube. The latter tool consists of a steel pin, one end of which is turned down to a diameter slightly smaller than the I.D. of the tube. This end of the tool terminates in a square shoulder which when inserted in the tube end, butts up against the internal shoulder left in the tube after the above reaming operation. The outer end of the pin has an enlarged head to permit striking with a hammer to facilitate the removal of the tubes. Under the driving action, the thinner wall at each end of the reamed out tube tends to collapse. In this way, the expanded tube is driven out without danger of injuring the hole in the tube sheet.

There are other methods of removing tubes from the condenser. However, the above Described method gives satisfactory results.

Insertion of new tubes will be greatly facilitated by using a tube guide or tube pilot.

Lay down Procedure

The brief lay down procedure is described below:

The condenser centre line is at an elevation of .. m from the finished ground level.

The building wall adjacent to the condenser area has been provided with a collapsible door, which can be lifted upwards whenever necessary.

The length of one tube is ~ m and weight is ~ 3.8 kg

As per the layout available, it can be observed that there is adequate space available to manoeuvre the entire length of the tubes ( please refer General layout attached Drg No. DPB BB 00 000 ); though the weight of the tube demands only one labourer, in view of the length, two labourers may be necessary for manoeuvring. Hence the tube, once detached from the condenser, can be pulled out and laid on the ground below.

In case the number of tubes are more, the tubes, after removal, can be carried to the turbine operating floor and bundled together. The tube bundle can be transported to the unloading area of the building using the crane. From there, the tubes can be carried away by truck.

FOR INFORMATION

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