FORM
CONDENSERS AND COOLERS
GENERAL
Maintenance of condenser and cooler shells is impor- tant to provide trouble free operation of the chiller. The water side of the tubes in the shell must be kept clean and free from scale. Proper maintenance such as tube cleaning, and testing for leaks, is covered on the fol- lowing pages.
CHEMICAL WATER TREATMENT
Since the mineral content of the water circulated through coolers and condensers varies with almost every source of supply, it is possible that the water being used may corrode the tubes or deposit heat re- sistant scale in them. Reliable water treatment compa- nies are available in most larger cities to supply a wa- ter treating process which will greatly reduce the cor- rosive and scale forming properties of almost any type of water.
As a preventive measure against scale and corrosion and to prolong the life of cooler and condenser tubes, a chemical analysis of the water should be made prefer- ably before the system is installed. A reliable water treatment company can be consulted to determine whether water treatment is necessary, and if so, to furnish the proper treatment for the particular water condition.
CLEANING COOLER AND CONDENSER TUBES
COOLER
It is difficult to determine by any particular test whether possible lack of performance of the water cooler is due to fouled tubes alone or due to a combination of troubles. Trouble which may be due to fouled tubes is indicated when, over a period of time, the cooling ca- pacity decreases and the split (temperature difference between water leaving the cooler and the refrigerant temperature in the cooler) increases. A gradual drop- off in cooling capacity can also be caused by a gradual leak of refrigerant from the system or by a combina- tion of fouled tubes and shortage of refrigerant charge. An excessive quantity of oil in the cooler can also con- tribute to erratic performance.
CONDENSER
In a condenser, trouble due to fouled tubes is usually indicated by a steady rise in head pressure, over a period of time, accompanied by a steady rise in con- densing temperature, and noisy operation.These symp- toms may also be due to foul gas buildup. Purging will remove the foul gas revealing the effect of fouling.
TUBE FOULING
Fouling of the tubes can be due to deposits of two types as follows:
1.Rust or sludge – which finds its way into the tubes and accumulates there. This material usually does not build up on the inner tube surfaces as scale, but does interfere with the heat transfer. Rust or sludge can generally be removed from the tubes by a thorough brushing process.
2.Scale – due to mineral deposits. These deposits, even though very thin and scarcely detectable upon physical inspection, are highly resistant to heat transfer. They can be removed most effectively by circulating an acid solution through the tubes.
TUBE CLEANING PROCEDURES
BRUSH CLEANING OF TUBES
If the tube consists of dirt and sludge, it can usually be removed by means of the brushing process. Drain the water sides of the circuit to be cleaned (cooling water or chilled water) remove the heads and thoroughly clean each tube with a soft bristle bronze brush. DO NOT USE A STEEL BRISTLE BRUSH. A steel brush may damage the tubes.
Improved results can be obtained by admitting water into the tube during the cleaning process. This can be done by mounting the brush on a suitable length of 1/8" pipe with a few small holes at the brush end and con- necting the other end by means of a hose to the water supply.
The tubes should always be brush cleaned before acid cleaning.
ACID CLEANING OF TUBES
If the tubes are fouled with a hard scale deposit, they must be acid cleaned. It is important that before acid cleaning, the tubes be cleaned by the brushing pro- cess described above. If the relatively loose foreign material is removed before the acid cleaning, the acid solution will have less material to dissolve and flush from the tubes with the result that a more satisfactory cleaning job will be accomplished with a probable sav- ing of time.
COMMERCIAL ACID CLEANING
In many major cities, commercial organizations now offer a specialized service of acid cleaning coolers and condensers. If acid cleaning is required, YORK
YORK INTERNATIONAL | 55 |
