SUBJECT : CONDENSER TUBE CLEANING USING BULLET SHOT METHOD PROJECT : SIMHADRI UNIT 1 PROBLEM CONDENSER FOULING OF Cooling Water causes different tube fouling problem that affects the heat transfer and life expectancy of Condenser Tubing.

Bio fouling is organic debris that adheres to the inside diameter of the tube surface or blocks the intake flow at the tube sheet. All tube fouling will increase flow velocity, reduce heat transfer, increase back pressure and decrease efficiency of the condenser. Bio fouling will substantially increase fuel costs.

Slime/Algae is bacteria that adheres to the condenser tube surface. This bio fouling will reduce the usable tube surface area, will have a negative effect on heat transfer, will constrict cooling water flow and will significantly decrease plant performance. These biological organisms will aggravate and accelerate corrosion, erosion and cause pitting of the condenser tubes.

Foreign Material lodged downstream in the tubes causing flow deflection, will result in localized pitting, eventually leading to premature tube failure.

Scale is a hard deposit that adheres to the condenser tube surface. This scale will reduce heat transfer, decrease plant performance and will cause pitting of the condenser tubes.

BENEFITS OF CONDENSER CLEANING:

Reduce Operating Costs

Routinely scheduled condenser cleaning will increase the efficiency of the unit and decrease fuel consumption. In this economy, with today’s environmental concerns and with the current competitive market, it is imperative to minimize fuel usage. This makes regularly scheduled cleanings an absolute necessity.

Extend Tube Life

A thorough condenser tube cleaning using the proper method will prolong the useful long-range condenser tube life. Periodic cleaning will delay replacement of this existing equipment to assure future production. Regardless of the tube material, the primary way to keep condenser tubes from corroding, eroding or pitting is to keep them clean.

Prevent Tube Failure

Planned tube cleaning can avert repair or replacement of heat transfer equipment indefinitely. Emergency outages for repair of condenser tube failures and expenses associated with the repair or replacement of other equipment in the system after a tube failure could be costly. These emergency outages can be avoided by systematic and regular condenser cleaning.

Increase Unit Performance

Scheduled condenser cleaning will increase overall plant performance, return the unit to its intended heat transfer rates and increase the overall operating efficiency of the plant.

Hence it is extremely important to maintain the tubes of the condenser as clean as possible, using highly efficient and reliable equipment, for which the pay back period will be very short.

METHODS OF CONDENSER CLEANING :

Following are some of the popular methods /tools used for condenser tube cleaning globally:

Abrasive or Nonabrasive Balls For light to moderate soft deposits. Balls will also be used for u-bend sections.

Plastic Scrubbers For moderate to heavy soft deposits. Nylon Bristle Brushes For heavy soft deposits. Brushes are specifically sized for maximum cleaning. Nylon brushes flex slightly to maintain maximum contact and scrubbing action along the full length of the tube.

MECHANICAL SYSTEM

Rotating Flexible Shaft Nylon Brushes For all soft deposits. Rotating mechanical devices will be used to clean u-bend tubes and units with an un accessible exhaust end.

Metal Brushes/Cutters/Buffers For all hard deposits. Rotating Rigid Shaft.

Drill Bits For all extremely hard deposits.

WATER PRESSURE SYSTEM

Bronze Bladed Cleaners For hard scale. Bronze cleaners are specifically designed for removal of scale on soft tube materials

such as copper-nickel, brass, etc. Steel Bladed Cleaners For hard scale. Steel cleaners are specially designed for removal of scale on titanium or stainless steel tubing. All metal bladed cleaners are oversized for maximum contact to remove scale and deposits.

One of the recently evolved methods for Condenser Tube Cleaning is by using Bullets

How this technique works ? Spring loaded tube cleaners (Bullets ) are shot through fouled condenser tubes using specially designed water guns at 15-25 Kg/CM2 water pressure . The bullets moving through the tube one end to the other scrape off the deposits and corrosion scales. Water from the gun flushes out scraped deposits resulting in a clean inside surface of the tube. Tube cleaners exit at the end of the condensers hitting collection screen hung at the other end . these cleaners are collected, cleaned and used again . Normally a bullet can be used 10 to 15 times. The quick process ensures less down time. A 210 MW unit condenser can be cleaned in about 3 days time unlike chemical cleaning or hydro jetting which takes more than 10 days. Also on line cleaning with the unit in service and isolating only the condenser required for cleaning can be carried out in this method.

The above method of Condenser Cleaning using Bullets was carried out By M/s. Arudra Chemicals at Simhadri Unit –1 in March 2003 prior to conducting PG Test.After this bullet cleaning , condenser vacuum improved 3-4 mm of mercury column.

This activity was carried out under shut down condition and partly when the unit was under shutdown condition and partly when the unit was in service thus establishing the flexibility in the cleaning process.

Two jet pumps were used simultaneously for completing the operation. It is feasible to use even 4 jets simultaneously from the same pumps to complete the operation still faster. Proper counting and systematic cleaning ensured that no bullet was left inside.