Reverse Dial Alignment Procedure

Reverse Dial Indicator Method - Alignment Procedure

Reference Standard – API 610 and API 686

General Refinery Services

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Note: This procedure conforms to API 610 and API 686

Reverse Dial Indicator Method 1) Learn about the machine you are aligning.

a) Visually check coupling, pipehangers, base bolts, coupling spacing etc. b) Check for coupling & shaft run out.

2) Learn about the machine you are aligning. a) Visually check coupling, pipehangers, base bolts, coupling spacing etc. b) Check for coupling &

3) Know the characteristics of your tool. a) Perform a Sag Check - See Sag check example

4) Prepare the machine. a) Remove all existing shims from under the feet -if old shims are to be used, clean them thoroughly. -always use minimum amount of shims. b) Clean the base thoroughly. -scrape and file away all rust, nicks, and burrs

c) Examine the base bolts and holes. -retap if necessary -replace bolts if necessary

5) Installation of alignment brackets a) Clean mounting surface, file off nicks and burrs. b) Check indicators for sticking and loose needle. c) Aim indicator stem directly toward center line of shaft.

6) Measurement a) measure distance between the two indicators. b) measure distance between indicator and front feet. c) measure distance between front and back feet.

7) Layout graph paper a) mark indicator position b) mark feet position. c) remember to mark + and - signs (this eliminates confusion)

example: graph layout




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8) Horizontal Move

Horizontal Move

The horizontal move is the part of the alignment process that aligns the shaft's centerlines from side to side. View the machine from the pump end, zero the indicators on the left, and then rotate and read on the right. Make sure that you always view the pump from the same direction in order for you to keep the left and right directions correct. There is no sag compensation on the horizontal move.

For example:

the indicator on the pump reads -8 the indicator on the motor reads +10

The shafts are collinear at 1/2 the Total Indicator Reading.

Using graph paper to illustrate the position. Under the indicator position mark the point that is 1/2 the indicator reading. (-4 for the pump and +5 for the motor) Connect these points and extend the line past the motors feet. This will show you how much you need to move the motor for horizontal alignment.

These indicator readings mean that you need to move the motor: front foot .006" left back foot .007" left

You can avoid graphing the horizontal move by zeroing the indicators on the left and rotate them to right. Now turn the indicator needles half way to zero and begin to walk the motor into place by moving the fartherest foot toward zero and then the nearest foot. Slowly walk the motor into place by alternating the moves until you obtain two zero indicator readings.




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Now begin the procedure for the vertical move. Be sure to check your equipment for sag and soft foot.

9) Perform Vertical Move Vertical Move

The vertical move is the part of the alignment process that aligns the two shaft's centerlines into their proper up and down position. Usually you will have to add or remove shims in this step. The indicators are zeroed on the top and read at the bottom. (start with a plus + reading if you need to compensate for sag)

Example: the indicator on the pump reads -12 the indicator on the motor reads +8

This means that the shafts are one half the total indicator reading from being collinear at these points.

Using a square grid graph paper to illustrate the position. Under the indicator position mark the point that is half the indicator reading. ( -6 for pump side indicator and +4 for the motor side indicator) Connect these two points with a line and then continue the line past the lines representing the feet on the motor. The graph now shows that the front foot needs to have a .003" shim added and the back foot needs to have a .001" shim added.

Now with your shims in place. Tighten all bolts and take and check your readings. If the

readings are within tolerance than your equipment should be aligned




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10) Check for Soft Foot

Soft Foot

Soft foot is a condition in which one of the feet does not sit flat on the base. The foot or the base may have been warped. When you tighten the bolt on the foot, the machinery will distort.

Parallel Soft Foot Angular Soft Foot

How to check for Soft Foot

1. Move indicators to 12 o'clock position, depress indicators and then zero. 2. Loosen one base bolt. If indicator moves away form zero, place the amount of shims that will slide under that foot. Retighten bolt and make sure the dial indicator needle does not move. 3. Repeat this procedure for the remaining feet.

Step 11: Tighten all bolts and recheck indicator readings.

Step 12: Pipe stress check prior to final alignment check.

Step 13: Remove alignment brackets.

Sag Check

A sag check is a test that determines the amount an indicator bracket will sag at a given

distance.How to perform a sag check Clamp the brackets on a sturdy piece of pipe the same distance they will be when placed on the equipment. Zero both indicators on top, then rotate to the bottom. The difference between the top and bottom reading is the sag.

Sag will always have a negative value, so when allowing for sag on the vertical move always start the dial indicator with a plus(+) reading. For example if you have .002" sag; when you zero your indicators on top put the needle on a +2 instead of zero to compensate for the sag.

Piping Connection to rotating equipment – Pipe Stress Check




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Before the equipment is offered for the final alignment inspection all work on piping systems shall be completed. This includes pressure tests, cleaning or air blowing and installation of permanent supports (fixed, sliding and spring supports). During these activities the piping shall be disconnected from the equipment. Tolerances on flange connections between rotating equipment and associated piping: 1. Parallelism

Before bolting up, flange faces shall be aligned parallel within 0.05 degrees in all directions, i.e:

Flange diameter (mm)

Maximum deviation from parallel across flange diameter (mm)

< 300 0.2

300 to 600 0.3

> 600 0.5

Flange bolt holes shall be aligned within 3 mm maximum offset. 2. Clearance

The gasket type, material and size shall be checked. The gap between the flanges shall be just sufficient to slide in the gasket without damaging the gasket or the flange faces.

3. Concentricity

The flange bolt dimensions and material shall be checked. Stud bolts shall extend beyond the nut, but not by more than the height of one nut. To check flange concentricity the flange bolts shall slide freely through the bolt holes of mating flanges without interference.

4. Proceed with the pipe stress check. Dial indicators should be on the equipment before and during the tightening of the piping and brackets, to detect any distortion. The relative movement of shaft centre lines shall not exceed 0.025 mm (= 0.05 mm TIR). The final shaft alignment reading shall be taken with all process piping and auxiliary piping connected with proper gaskets in place and shall be within the tolerances.

Alignment Tolerances

An alignment tolerance allows the alignment to be within an acceptable range of misalignment that does not affect the machine's ability to rotate properly. Misalignment is the deviation of relative shaft position from a collinear axis of rotation, measured at the points of power transmission, when the equipment is running at normal operating conditions. A good rule of thumb for general purpose equipment (3600 rpms and less) is .0005" (1/2 thousandth) per inch of coupling span.




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This tolerance uses only speed and coupling span. Other factors to consider are: How critical is the equipment, mechanical stiffness, the excitation forces influencing the rotor dynamics, etc. This is where knowing your equipment is essential.

Final misalignment shall not exceed the Manufacturer's recommendations or the following, whichever are the more stringent:

Equipment condition Radial (parallel) misalignment Total Indicator

Reading

Axial (angular) misalignment

All speeds and coupling spacer lengths < 250 mm

0.05 mm 0.05 mm (based on a diameter of 150 mm)

All speeds and coupling spacer lengths > 250 mm

0.02 mm per 100 mm of spacer length

0.05 mm (based on a diameter of 150 mm)

Speeds lower than 1500 r/min, low power (< 10 kW) with elastomeric flexible couplings

0.10 mm 0.05 mm (based on a diameter of 150 mm)

Both the driver and driven shafts are turned simultaneously to take alignment readings. Readings shall be demonstrated to be repeatable. Dial bracket sag shall be taken into account and shall not be more than 0.05 mm (which should be checked, e.g. on a lathe). Alignment checks include:

- a preliminary check to ensure that alignment is possible with regard to shim limitations, bolt and bolt hole positions, etc.;

- an alignment check without piping connected to the equipment;

- an alignment check with the bearing bracket support loose (for overhung pumps);

- final alignment check. For this check, the dial indicators should be on the equipment before and during the tightening of the piping and brackets, to detect any distortion. The relative movement of shaft centre lines shall not exceed 0.025 mm (= 0.05 mm TIR). The final shaft alignment reading shall be taken with all process piping and auxiliary piping connected with proper gaskets in place and shall be within the tolerances of (6.2).




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Final alignment data shall be recorded, filed and handed over together with the Equipment Record Card of the equipment.

Reverse Dial Alignment Procedure

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