hrsg.inspection

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Vogt Power International

4000 Dupont Circle, Suite 400 Louisville, Kentucky 40207 502/899-4500 Fax: 502/899-4690

Sapulpa Manufacturing Operations: 2110 N. Industrial Drive Sapulpa, Oklahoma 74066 918/227-4202 Fax: 918/227-4207

Benefi ts of Routine I nspections on HRSG(s)

Attn: HRSG Plants

Re: Maintenance and the Benefits of Routine Inspections on HRSG(s)

You have invested millions of dollars in your Combined Cycle Plant and expect your HRSG(s) to last for 30 years,

right? Your HRSG can last for 30 years as they have few moving parts to cause wear, but obtaining the desired life

out of any major piece of equipment requires continuous conditional assessment. You only have to think of your

automobile or home to know that proper maintenance increases reliability, life expectancy and protects your

investment.

One way to insure your asset is protected, is by scheduling an annual inspection, not only with a reputable engineer

who is familiar with the design of your equipment, but also by the Authorized Inspector (AI) and the Water

Chemistry Technician or Engineering Lab Technician (ELT). Only in this manner can the End User receive the

best possible inspection.

Vogt Power International (VPI) recommends annual HRSG inspections by a qualified VPI inspector as well as the

AI and ELT. Why is it necessary to have all three, and at the same time? Representatives from different disciplines

look at different things. We believe that this combination represents a total that is greater than the sum of its parts.

Each inspector is trained differently and although there are some overlaps, I have yet to perform an inspection

where the other inspectors or we did not learn something from one another. This adds value to the inspection and

enhances the results for the End User.

We continue to see budget restraints that are eliminating inspections. I have witnessed those that feel a HRSG is a

tea kettle and does not need an inspection. This perception is a dangerous one and can eventually result in a

HRSG that is no longer reliable or safe to operate. As an example, shortly after commissioning an HRSG we found

problems with pipe supports. This issue was not addressed when it was first noted and after 5 years of operation,

with no inspections and no concerted effort to resolve the problem, the result was a catastrophic failure of the

module support system. After re-supporting the module, 16 cracks were found in various pressure part welds. The

lost revenue was $500,000 to $1,000,000 and the repairs amounted to well over $150,000. The cost of an

inspection would have been less than $10,000. The HRSG is not just a tea kettle and it needs almost as much

attention as the gas turbine.

Often when we are performing an inspection, we are asked, What do we look for? The answer is, Nothing inparticular, the inspector should resist preconceived notions as to where problems may be found. It is essential that

the inspector be thorough and observe all areas of the HRSG. A common mistake is to look for one thing; and

while one is looking for evidence of that, they will tend to miss something else. When training other inspectors,

we often sit quietly in the inlet duct for five minutes, leave the compartment and ask the Engineer in Training,

What did you see? We often end up going back in the duct to identify those items that were overlooked by the

novice inspector. Learning how to be observant takes practice, and you must be very focused or you will miss a

precursor to a failure.


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Not only can an inspection help to identify current problems, but they are also the best tools for planning for

repairs during the next outage. Six to nine months prior to a major outage is an excellent time to schedule aninspection. This provides sufficient time for budgeting, scheduling, writing and issuing purchase orders for spares

and other equipment. This process will increase your reliability by reducing unscheduled and costly emergency

outages.

Some of the actions performed during an inspection are provided below:

Identify areas/equipment in need of repair Identify areas to monitor Review and identify spare part requirements Identify safety issues Comment on operations Identify areas for performance improvement/enhancement Establish maintenance checklists Identify Performance Degradation Inspect the inlet duct, the interior and exterior of the ductwork, and the CT exhaust expansion joint will

be inspected for hot spots and damage.

Examine the burner, identify bent runners and/or burnt igniters. Structural steel will be visually checkedon the burner and the distribution grid

Access lanes will be investigated for HRSG module anomalies, such as bowed tubes, evidence of tubeleaks, condition of finning, and corrosion or deposit amounts on the finned tubes, headers, and insulation

lining of the HRSG.

Investigate the stack and breaching area for deposits and corrosion. An investigation of the drums will be made, including deposition, consistent/stable water level(s), and

evidence of steam leakage around baffles, drum penetrations, and inspection of the steam separating

equipment Examination of the outside casing will be performed, specifically the expansion joints, casing seals, pipe

hangers, spring cans, and condition of vent and drain piping, if accessible

Search for evidence of Dew Point Corrosion (Ammonia Salts, Sulfuric, Water) Inspect Structural foundations, casing penetrations, and pipe supports Examine susceptible areas of erosion, EC/FAC, stress corrosion cracking, etc.

With more units operating in cyclic service, it is more common to see that the HRSG is still warm from an

overnight shutdown when cold water is introduced during the morning startup. This scenario can result in water

formation (condensation) on the outside of the finned tubes and inside the liners resulting in corrosion of tubes and

casing. For example, acid corrosion can occur if ammonia from the SCR system combines with sulfur from the

exhaust gas to form deposits of salts, ammonia bisulfate, and ammonia bisulfate on finned tubes. If this type of

event occurs and is inevitable, then conditions can be assessed and recommendations will be made to minimize this

corrosion.

General Maintenance / Maintenance Checks

Areas that are often in need of repair are holes in expansion joints, casing penetrations, readjustment of piping

supports, safety valve certification and replacement of drum internal hardware. Having a complete list of repairs

allows the development of a repair schedule and a budget plan.


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Walking down the plant every day is the best maintenance check one can perform. One can identify the source ofdisconcerting noises (rattles, bearing noise, etc.) associated with an operating plant during a daily walk down.

Vogt Power Inspectors can also help assist the operators on creating maintenance checks lists.

Identify areas to monitor

Not all areas of inspection will need immediate attention. Some will need to be monitored to determine the best

time to repair or replace. An example would be pipe that is thinning due to the effects of erosion or corrosion.

Having a list of items to be monitored allows for cost and time estimates to be made so that these repairs can be

performed at the most convenient time.

Review and Identify Spare Part requirements

For repair activities, use of the current supply of spare parts or a new spare parts order will be required. An

inspector can review inventory and make necessary recommendations based upon the plants current and potential

future repair needs.

Not only will a spare parts review ensure that you have the needed spares in house when you need them, but this

exercise also provides an opportunity to see if there has been any revisions or improvements to the original design

that could be implemented, often this is the case.

Identify Safety Issues

For some plants, a safety review is required. Vogt Power s inspectors are qualified and certified Closed Space

Entry, Gas Detection & Air Monitoring, and Respirator trained. Each inspector is taught to identify those issues

that are known to be potential threats and instruct how to minimize or eliminate the exposure to such threats.

Comment on Operations

We have seen many plants that were designed originally for base load operation but have now decided to operate in

cyclic service. The cyclic service can create additional wear on the HRSG due to frequent heating and cooling

required and thermal/hydraulic stresses on the equipment for which it was not designed.

An inspection can provide suggestions on modifications to be made to minimize wear and tear on the unit. For

example, in some instances it is valuable to install a stack damper to keep heat inside the HRSG after shutdown so

that the restart time and cool down rates can be minimized while also keeping thermal stresses to a minimum.

Identify Areas for Performance Improvement/Enhancement - Plant Assessments

Given the current market conditions, plant personnel are focusing more on existing equipment. We are assisting

them in this endeavor by identifying ways we can decrease the Net Plant Heat Rate (NPHR), increase efficiency,

increase capacity, and lower emissions. We refer to these as Plant Assessments.


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One of the most valuable benefits during an inspection then is the identification of performance degradation and

performance improvements. Even small improvements can lower a plants cost due to the high cost of fuel.Subsequently, VPI can now provide the following:

Phase I- Inspection

Phase II- Plant Assessments

Phase III- Plant Improvements

Phase IV- Return on Investment (ROI)

Phase V- Product Specifications

Phase VI- Turn Key Implementation

Ask any Plant Manager what his NPHR is and he will immediately tell you, but what about the HRSG, and the

BOP equipment? This is where we can provide added value. Not only can we perform this analysis but we can

also help the plant determine whether they should upgrade the GT & HRSG, or the ST & HRSG.

Ask the Expert

Finally, the inspection is an opportunity to Ask the Expert. Part of the value added of being an inspector is

teaching and instructing the plant staff on technology improvements, enhancements and general questions on how

the HRSG was designed and intended to operate. It is an excellent opportunity forlearning from one another. We

have yet to inspect a HRSG where we did not learn or understand better our own product from those who actually

operate the equipment.


At Vogt Power, we not only design and manufacture new HRSG(s) but we also have an Aftermarket group that

provides assistance to plant owners and operators with inspections, consulting, plant assessments, feasibility

studies, outages, spare parts inventory, and retrofits.

As a plant engineer, one is faced with situations that one can not always control. Employing Vogt Power

International allows you a direct link with a manufacture and allows you the opportunity to resolve differing

opinions and ultimately increase availability and reliability of your unit(s). We are here to provide an honest

opinion and to share information. For more information, please contact our Aftermarket Department.

Jeff Daiber, Director for Aftermarket & Warranty

Vogt Power I nternational4000 Dupont Circle

Louisville, KY 40207

Mailto:aftermarket@VogtPower .com

Phone: 502.899.4500

Fax: 502.891.1960

Web: www.VogtPower .com

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