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Assuring quality in the small to medium-size job shop

Quality assurance calls for careful attention to each step of a job—before the job is sold, during, and following production—and requires input from multiple departments.

Prejob Requirements

The sequence of inspection (Figure 1) phases is of the utmost importance. The salesperson or person who prepares the quotation for a job must consult the shop supervisor and quality control/quality assurance (QA) manager before quoting. This is the time to address the shop's suitability to perform the work, discuss possible changes, and determine whether to accept or reject the job. Aggressive salespeople interested only in selling the job can create problems if they don't follow this process.

The shop supervisor can determine the number of hours that can be dedicated to the job to complete the work on time, and whether the manpower, machinery, and equipment are available to perform the work. Sometimes the shop is already committed to a previous project that ties up machinery, equipment, and personnel for a length of time that does not allow the new job to be scheduled. A job that is not finished on time frequently results in the loss of a customer.

The QA manager also plays a crucial part in determining whether the job can be completed according to the specifications and on time. Most job shops do not have equipment or personnel to perform some types of nondestructive testing (Figure 2). Factors such as location of office personnel or residences in relation to the shop do not allow radiographic testing. In most cases, the time and cost for training nondestructive testing technicians make outsourcing a more viable option.  Outsourced testing costs must include loading, packaging, and shipping to and from the testing company, along with the actual testing costs.

The job specifications may include requirements that the shop is not qualified to meet. Most jobs refer to a particular code or standard. The QA manager must determine whether the shop is authorized to perform the work. For instance, if a shop is authorized to work only on unfired pressure vessels (ASME U" stamp), the QA manager must inform the sales personnel, or whoever is responsible for accepting or rejecting the job, that the shop is not authorized to do fired pressure vessels or pressure piping (ASME S stamp).

Some projects require stress-relieving the weldment, which can be performed by thermal or vibratory (Figure 3) methods. The contract usually specifies which method is to be used and whether the weldment is to be stress-relieved again after machining. Either method must have a recording device to show that the part is stress-relieved. A written procedure is mandatory, and the operator must be qualified.

Some specifications may require measuring instruments that are not available in the shop. Sometimes the specs stipulate a specific type of equipment, such as a coordinate measuring machine (CMM). The cost of these instruments, in excess of $100,000, can exceed the total job profit. A shop most likely would outsource the CMM work in this case.

Personnel requirements also could be a deal breaker. The specifications may call for an American Welding Society-certified welding inspector (AWS CWI). These inspectors are in short supply, and time constraints often do not allow for training current shop inspectors to become certified. It can be expensive to hire a CWI by contract.

Having the chief engineer and the engineering department check the customer-supplied top-level drawings is a must. Notes on the drawings can be a factor in determining whether the company wants the job. Sometimes the notes do not match the specifications, which can cause confusion and delays on the shop floor.

Work should no commence before any confusion about the specifications or drawing is cleared up. The QA manager should write a nonconformance report for each discrepancy or unclear portion.

Figure 1
AWS Inspection Kit

A better-safe-than-sorry tactic is to hold a question-and-answer meeting with all employees who will be involved with the work. Many times the workers are the best inspectors in the shop.

More Preliminary Work Before the Job Begins

Ordering material is especially critical for minimizing problems on the job. The engineering department usually is responsible for preparing bills of material. These documents are extremely critical for all phases of the fabrication. To be safe, the QA manager and shop supervisor should check them before they are presented to the purchasing department.

Each purchasing document must include a statement that "all material must be accompanied by a material test report (MTR) or a certificate of compliance (C of C).

If the job is to be built to AWS D1.1, ASTM (American Society for Testing and Materials) numbers must be listed on the purchase order. For instance, low-carbon steel plate may be ASTM A709 Type A36. If the job is to be built to ASME (American Society of Mechanical Engineers) standards, the number would be SA 709 Type A36.

Some material may be dual-certified, with both these numbers shown on the MTR.

The receiving inspector must check the receiving document against the purchasing document to ensure that the material meets all the requirements of the purchase order (PO) (Figure 4). The receiving inspector must then compare the MTR to the ASTM or ASME specification.

The chemical composition and mechanical properties should be listed on the MTR. If a discrepancy shows up between the MTR and the PO, a nonconformance report must be prepared and submitted to the person assigned to resolve such problems.

If there is a hardness requirement, the inspector must check the material and record the results, stating whether it is in compliance or nonconforming.

In some cases, the discrepancy can be resolved in-house; however, many times it is necessary to involve the customer. A material substitution is an option, but only with the customer's approval and if it doesn't violate the code of construction. It is always safer to involve the customer to prevent back charges or rejections at the end of the job.

If the material is found to be in a nonconforming condition, it must be placed in isolation and marked as "nonconforming" or "rejected material" until the nonconformance is resolved. The resolution may satisfy the customer and/or a code reference, but it must be documented as acceptable or not acceptable.

Figure 2
Ultrasonic Testing Instrument

In the Shop, Finally!

Once the material is checked and approved by the receiving inspector, the engineering department provides a cut list, which the shop inspector examines and approves. Each piece that is cut must be measured by the shop inspector and marked as OK or rejected. Burning slag must be removed satisfactorily.

If marked OK, the piece can be fitted as noted on the drawing. The inspector then inspects the fit-up for proper dimensions and marks it as OK or not OK to weld.

The inspector also checks to determine whether the proper welding procedure (with preheat, etc.) is available to the welder, and if the welder is qualified to perform that procedure. If the procedure is correct, and the welder is properly qualified, the welding may begin. If not, a nonconformance report is submitted to the proper supervisor and work halted until the problem is resolved.

If the procedure and welder qualification are satisfactory, the welder can begin welding and must mark the weld at specified intervals with his or her mark. The inspector immediately begins observing the weld visually and marks the welded area as OK or rejected. If the weld is marked OK, and further nondestructive examination (NDE) is not required, the welding can continue.

If further NDE is required, the inspector marks the method of NDE at intervals previously specified. The inspector has the prerogative to stop the welding until an NDE is performed by a qualified technician on a certain area of the weld (specified or at the discretion of the inspector). If the results are satisfactory, the welding may proceed. If the results are not satisfactory, the inspector may stop work and report the results to the proper supervisor.

The inspector may remove the welder from the job and require a test to determine why the weld is not being produced to the specified standards. If the problem is with the equipment, the supervisor can correct the settings or replace the machine, and the welder can return to the job.

The inspector must perform an overall dimensional check upon completion of the welding. Any shrinkage or distortion that causes the weldment to be out of tolerance requires a nonconformance report.

A method for a corrective action procedure (CAP) must be established and approved by the engineering department before attempting the correction. If the CAP is approved, the inspector must monitor the condition of the material (due to heating, bending, etc.) to ensure that the material will not be affected metallurgically or mechanically. Excessive heat or cold bending can adversely affect the material.

Machining might be required after welding and stress relieving. The machine shop inspector (Figure 5) must check all machined surfaces for surface roughness. This will be indicated on the drawing or the specifications. If the item is round, the runout (out of roundness) must be checked at several points.

Once the problem is corrected, the inspector checks the cleanliness of the welded areas to make sure there is no slag, tacks, or gouges. The unit then can be released for blasting. All machined surfaces must be protected from the blasting and painting processes.

Figure 3
Vibratory Stress Reliever

The inspector then checks the blast profile to be sure it meets the requirements of the paint procedure and is properly cleaned. If OK'd, the unit can proceed to the paint area.

The receiving inspector is responsible for ensuring that the proper primer, paint, and thinner are provided. The paint inspector then attests that the paint is properly mixed and the specified equipment is used (airless or air spray).

Humidity and temperature must be recorded, along with the dew point. A psychrometer (sling or digital) is used for this confirmation.

The number of layers and thickness of each layer must be checked and recorded, and the drying of each layer must be observed and recorded.

Got 'Er Done! (Almost)

The last step often is time-consuming and sometimes difficult. All the documentation from start to finish must be gathered and organized in a fashion that is either specified by the customer or by in-house practices. Commonly referred to as the master job file, it usually consists of:

The original completed request for quote (RFQ) document (proof of pricing).
The as-built drawings and specifications.
The customer PO (Also serves as confirmation for the RFQ).
The acknowledgement of PO and pricing.
Shop details and instructions.
Shop-generated bills of materials.
Shop RFQs to vendors for materials contract inspections.
Shop POs to material vendors.
Receiving tickets and MTRs.
Receiving checklists.
All inspection reports.
Stress-relief reports.
NDE reports.
Packing and loading directions (Figure 6).
Loading release form.
Package, load, and ship documentation (Figure 7).
Final sign-off by QA manager (Figure 8).

About the Author
Weld Inspection & Consulting

Professor R. Carlisle "Carl" Smith

AWS CWI, CWE, NDE Level III

Weld Inspection & Consulting

PO Box 841

St. Albans, WV 25177

304-549-5606