Flanges. Frequently, a flange must be welded to the end of a pipe, as shown in Fig. 14-6. It must be centered with respect to the axis of the pipe and the face of the flange must be perpendicular to the axis. The bolt holes in the flange are usually in multiples of four and it is common practice to weld the flange so that two bolt holes share the uppermost position on the flange.

MAKE THE 3RD AND 4TH TACK WELD, 90° FROM THE POSITION SHOWN Fig. 14*5. Step-by-step procedures for fitting-up two pipes.

The first step in fitting-up the pipe is to hold it in place as shown in Fig. 14-6A. Two bolts are inserted in the bolt holes and a spirit level is placed so that it rests on the bolts. A helper holds the flange in the center of the pipe so that the bubble of the spirit level is centered. While the helper holds the flange in this position, the welder deposits the first tack weld in place. If bolts are not available, the level can be held as shown in Fig, 14-6B, with the top of the level tangent to the two bolt holes.

After the first tack weld has been deposited, the flange is carefully aligned. It is aligned centrally with respect to the axis of the pipe by checking the internal and external surfaces of the flange and the pipe. If the pipe is known to be in a horizontal position, the flange may be positioned perpendicularly to the pipe axis, in one plane, by placing a spirit level against the face, as in Fig. 14-7. The flange is aligned by tapping it with a hammer until the bubble in the vertical glass on the level reads zero; however, it is necessary to protect the flange against dents by placing a piece of soft metal or wood where the hammer blow is struck. When the flange is aligned, the second tack weld can be deposited.

Another method of aligning the face of the flange is illustrated in Fig. 14-8. One blade of a square is placed against the face while the

14-6. A. Aligning bolt holes on flange by placing the level on two bolts inserted in bolt holes; B. Aligning bolt holes on flange with a level.

Fig.. 14-8. Method of aligning a flange perpendicular to the axis of the pipe to which it is to be welded.

other blade rests on the side of the flange. With the square in the center of the pipe, two measurements are made between the surface of the pipe and the blade of the square. When both measurements are equal, the second tack weld can be made.

Before the two final tack welds are deposited the flange must be aligned again, this time 90 degrees from where it was first aligned. If the pipe is horizontal, a level cannot be used to check this alignment. A square and a rule must be used, as shown in Fig. 14-8. The last two tack welds can be deposited when both measurements are equal.

If the flange is to be attached to a pipe that extends out from a vessel, as in Fig. 14-9, it must be welded in place a certain distance from the vessel. To obtain this distance is largely a matter of welding the pipe to the vessel correctly; however, the location of the flange should be checked. This can be done by drawing a horizontal chalk line along the side of the vessel that is the same height as the center of the pipe, as shown in Fig. 14-9. The measurement is made by placing a straightedge or the blade of a rafter square against the face of the pipe and measuring between it and the chalk line.

The flange is held in the correct position by a helper while the welder deposits the first tack weld. When this has been done the flange must be checked and aligned before the second tack is deposited by placing a level against the face of the flange, as was shown in Fig. 14-7. After the second tack weld has been deposited the straightedge, or square, is again placed against the face of the flange and two measurements that are a distance apart are made

Fig. 14-9. Aligning the flange and measuring the distance from the face of the flange to the vessel.

between the straightedge and the chalk line. When the flange has been adjusted so that both measurements are equal, the remaining tack welds can be deposited.

90-Degree Elbows. If the pipe to which the elbow is attached is horizontal, the most convenient method of alignment is by using a spirit level, as shown in Fig. 14-10. By placing the spirit level on the face of the elbow, as shown in Fig. 14-10A, the elbow is leveled before the first tack is welded. After this tack weld has been made, it is again checked with the elbow in this position and adjusted until the bubble is centered. The spirit level then is placed in the position

Fig. 14-10. A. Aligning a 90-degree elbow, using a spirit level, prior to deposit­ing the first tack weld. B. Aligning a 90-degree elbow prior to depositing the second tack weld.

shown in Fig. 14-1 OB and the elbow is aligned until the bubble on the level is centered. The bottom tack is then deposited. The elbow should be checked in both directions again and realigned, if neces­sary, before the two remaining tacks are deposited.

If the pipe is not exactly horizontal, the elbow can be checked for crosswise alignment as shown in Fig. 14-10A. For lengthwise align­ment, a straightedge or the blade of a rafter square is used, as in Fig. 14-11. When two measurements between the straightedge and the center of the pipe, taken a distance apart, are equal, the elbow is aligned. The checking, aligning, and welding are done as before.

Fig. 14- H. Method of aligning a 90-degree elbow using a straightedge or rafter square.

Fig. і 4-12. Checking the alignment of a 45-degree elbow with a spirit level when the pipe to which it is to be attached is horizontal.

45-Degree Elbows. When the pipe to which the 45-degree elbow is attached is horizontal, the most convenient method of aligning the elbow in the direction parallel to the pipe is to use a spirit level, as shown in Fig. 14-12. The elbow is aligned when the bubble in the 45-degree glass on the level is centered.

If the pipe is not horizontal, as in Fig. 14-13, a protractor level can be used. The bubble in the glass is centered when the protractor is resting on top of the pipe and the reading, in degrees, is obtained.

Forty-five degrees are added to this reading and the protractor is adjusted to this position. For example, if the reading on the pipe is 12 degrees, the protractor is adjusted to read 57 degrees (12° 4- 45° — 57°). Adjusted to this setting, the protractor level is placed on the face of the elbow, as shown, and the elbow is aligned when the bubble is centered. Sometimes a flat piece of steel must be placed across the elbow, on which the protractor can rest.

Fig. І4-13. Method of checking the alignment of a 45-degree elbow with a protractor level when the pipe is not perfectly level.

Fig. 14-14. Method of checking the crosswise alignment of a 45-degree elbow. A. Laying out the reference line; B. Method of supporting the level to align the elbow.

Frequently, the 45-degree elbow is aligned crosswise, with respect to the axis of the pipes, by visual estimation. A method that can be used is shown in Fig. 14-14. The pipe is shown lying on a flat surface in Fig. 14-14A, with a square positioned against the face. Chalk is rubbed on the face and a reference line then is scribed across the face, using the blade of the square as a guide. The chalk makes the scribed line more visible. Two shallow center-punch marks are often punched at each end of the reference line and the angle iron is aligned with respect to these marks.

When the elbow is to be aligned against the pipe, the spirit level is placed on an equal-legged angle iron (3 x 3 x s/4 in. or 11/2 x 1 y2 x % in.) and the angle iron is positioned parallel to the reference line or the center-punch marks on the face of the elbow, as shown in Fig. І4-І4В. With the level in this position, the elbow is aligned when the bubble is centered.

Fig. 14-15. A. Aligning a tee prior to depositing the first tack weld; B. Aligning the tee prior to depositing the second tack weld; and C. Alternate method of aligning the tee.

Tees. A spirit level can be used to align a tee when the pipe is horizontal. As shown in Fig. 14-15, the level is placed crosswise and lengthwise on the upper face of the tee to align it in these two directions.

When the pipe is not exactly horizontal, the crosswise alignment is obtained by using the level as shown in Fig. 14-15A. Lengthwise alignment is obtained by using a rafter square, as in Fig. 14-15C A blade of the square may be held firmly to the end face or to the top face of the tee, and two measurements are made between the top of the pipe and the square. When the two measurements are equal, the tee is aligned in the lengthwise direction.

When the branch pipe to which the tee is to be connected is horizontal, the tee must be positioned as shown in Fig. 14-16. In this case, the tee can be aligned by placing the spirit level against one face and then the other face of the tee, as shown.

Fig. 14-16. A. Aligning a tee with a spirit level prior to depositing the first tack weld; B. Aligning the tee prior to depositing the second tack weld.

Vertical Pipe Alignment. The procedures for aligning vertical pipes are shown in Fig. 14-17. Short runs of vertical pipe can be aligned by using a level, as shown in Fig. 14-17A, Two positions on the pipe that are 90 degrees apart should be checked in this manner to make certain that the pipe is truly vertical. The pipe should be checked in this manner before depositing each tack weld. A piece of bent wire can be used to obtain the root opening when the pipe is in this position.

Longer lengths of vertical pipe can also be checked with a level. The pipe should be checked in two places around the pipe as before, but this must be done in several locations along the length of the pipe. A procedure that is frequently used to check long runs of vertical pipe is shown in Fig. 14-17B. A plumb bob is attached to the end of a line hanging from a convenient place near the top of the pipe. The distance between the wall of the pipe and the line is

Fig. 14-17. A-1 and A-2. Aligning a vertical pipe with a spirit level; B. Aligning a vertical pipe with a plumb bob.

measured in several places. When these measurements are all equal, the pipe is vertical in the direction shown.

Perpendicular Pipe Alignment, Frequently, a pipe must be welded perpendicular to another pipe. The elbow alone cannot be depended upon to provide the necessary alignment. A typical example of the method of aligning the pipe after the first tack weld has been made is shown in Fig, 14-18. The rafter square is held firmly against the

Fig. 14-18. Method of aligning two pipes perpendicular to each other.

Fig. J 4- 19. Another method of aligning two pipes perpendicular to each other.

horizontal pipe and several measurements are made between the blade of the square and the surface of the pipe. By lifting the end of the horizontal pipe, it is adjusted until the measurements are all equal, after which the second tack is welded in place.

As shown in Fig. 14-19, the measuring procedure could have been reversed, with the square held against the vertical pipe and the measurements taken between the blade of the square and the hori­zontal pipe. However, in this illustration the other end of the horizontal pipe is tack welded in place before the second tack weld is deposited on the elbow. Before the other end of the pipe is tack welded in place, the square is used, as shown, to make certain that the pipes attached to the elbow are 90 degrees apart. By this procedure, the horizontal pipe is held firmly in the correct position before the remaining tack welds are deposited on the joint at the elbow.