SOW CGC Sequoia.docx

Statement of Work Sequoia Propulsion Shafting, Strain Gage Alignment Inspection

PR# 2123403Y6172M73001

POC: James, Johnston Phone: 410-636-3095

SCOPE

Contractor to perform strain gage alignment inspection aboard USCGC Sequoia in Baltimore MD dates TBD. The intent of the strain gauge alignment check is to document the state of the existing alignment of the propulsion shafting, to ensure existing alignment is correct and to collect baseline data.

3.2 Strain gage alignment check. The Contractor shall provide the services of a Consulting Engineer who is an expert in propulsion shafting alignment using strain gage alignment method to perform the propulsion shafting alignment check.

NOTES

1. The intent of the strain gage alignment check is to document the state of the existing alignment of the propulsion shafting, to ensure existing alignment is correct, and to collect baseline data. Strain gage readings shall be taken at four key events as discussed in below paragraphs: afloat (pre-work), drydocked (pre-work), drydocked (post-work), afloat (post-work).

2. This alignment section of the specification is a performance specification. The performance specification describes the end result of work that the Contractor must accomplish, and the criteria by which this work will be measured. The Contractor is left on his own to achieve the specified end result, as long as he complies with the “measures of performance” that are specified.

3.2.1 The Contractor shall ensure that the Consulting Engineer has performed similar propulsion shaft alignments of like (or greater) horsepower, length and configuration. Provide proof of this experience to the KO at the arrival conference.

3.2.2 The Consulting Engineer shall develop a 225’ WLB propulsion mathematical model that is based on transfer matrix theory using the referenced documents.

3.2.3 The Contractor shall be responsible for developing and recommending an acceptable shaft alignment in accordance with the requirements in this specification.

NOTE

An acceptable alignment is defined as the vertical and athwartships positioning of all shafting system bearings, such that satisfactory bearing loads and wear patterns on all bearings are achieved, including reduction gear bearings.

3.2.4 The Consulting Engineer shall develop a mathematical model. As a minimum, the model shall take into account the following characteristics of the shafting system:

The characteristics of stern tube, strut and other bearings. Use manufacturer’s recommended clearance and compression (crush) data.

Dimensions of the propeller, propulsion shaft, couplings, thrust bearing, and reduction gear.

Limitation on the reduction gear bearing loading.

Bearing wear down.

Difference between docked and afloat conditions.

Bearing crush and radial clearance.

Permissible loads on all bearings.

3.2.5 For consistency with past alignments, the aft stern tube bearing (72” Thordon) shall be modeled as two bearings. Half the bearing shall be modeled at a point 9” aft of the stern bearings forward end. The other half shall be modeled at a point 9” forward of the stern bearings aft end.

3.2.6 The Consulting Engineer shall undertake the appropriate numerical investigations, using the referenced documents. The shafting alignment analysis shall provide, as a minimum, the following information:

Straight-line bearing reactions.

Optimum bearing reactions with associated slopes and deflections.

Influence Number Table.

Shaft slope, stress, and deflection at each bearing, flange, and concentrated load.

Location of maximum shaft stresses and deflections.

Whirling critical RPM.

Bearing weardown analysis.

3.3 Afloat pre-drydock strain gauge measurements. For alignment purposes, the Contractor shall instrument and measure, using the strain gauge method, the static alignment of shaft with the cutter afloat under the guidance of the Consulting Engineer. This shall be accomplished prior to the cutter arrival at the Contractor’s facility. The cutter shall not be drydocked until the completion of this work in accordance with Definite Item “Routine Drydock”. The plant shall be in the cold condition. The Contractor and the CG Inspector shall ensure that the fuel, water, and temporary ballast tanks (liquid loading) are filled to normal operating levels.

NOTE

CG personnel will rotate the shaft. The CG Inspector will witness the readings.

3.3.1 The Consulting Engineer shall carry out conversion of strain gauge readings to bearing reactions and offsets. The Contractor shall submit a CIR.

3.4 Drydocked (pre-work) strain gauge measurements. The Contractor shall instrument and measure, using the strain gauge method, the static alignment of the shaft with the cutter in drydock under the guidance of the Consulting Engineer.

NOTE

The CG personnel will rotate shaft. The CG Inspector will witness the readings.

3.4.1 The Consulting Engineer shall carry out conversion of strain gauge readings to bearing reactions and offsets. The Contractor shall submit a CFR

3.5 Drydocked (post-work) strain gauge measurements. The Contractor shall, after installation of the bearings and shafting system, take strain gage measurements and carry out conversion of strain gauge readings to the bearing reactions and offsets. Submit a CFR.

NOTES

1. CG personnel will rotate the shaft. The CG Inspector will witness the readings.

2. The Cutter’s tanks will be empty or reduced to a minimum.

3.5.1 The data obtained from all of these strain gage alignments shall be used to document the before and after states of the alignment, as well as to serve as a baseline for future strain gage alignment checks.

3.6 Load cell measurements. Prior to drydock (afloat), then again in the drydock prior to removal of the shafting, the Contractor shall measure the line shaft bearing loads using the load cell method. Submit a CFR showing the measured bearing loads.