bn-dg-c01h plant layout - cooling water towers

8/13/2019 BN-DG-C01H Plant Layout - Cooling Water Towers

1/5

6/12 BN-DG-C01H Plant Layout - Cooling Water Towers

ww.red-bag.com/jcms/design-guides/352-bn-dg-c01h-plant-layout-cooling-water-towers.html

Home About News Products Tools Library Forum Contact

search...

06-Jun-2012

Main Menu

HomeAboutNewsProductsToolsLibraryForumContact

LibraryContentMenu

QA StandardsGeneralProceduresDepartmentProceduresWorkInstructionsGeneralGuidesDesignGuidesEngineeringGuidesGeneralStandardsDesignStandardsEngineeringStandardsSpecificationsRequisitionsFormsCost CodesPapers

PCC Softw are

Softw are for creation of pipe classesand mechanical calculation of pipingcomponents. Read mor e ...

VES Software

Softw are for the design and mechanicalcalculation of pressure vessels and heatexchangers. Read mor e ...

Home Design Guides BN-DG-C01H Plant

BN-DG-C01H Plant Layout - Cooling Water Towers

Table of Contents

1. General

2. Types of Cooling Towers

3. Cooling Tow er Location

4. Water Makeup

5. Trash Screen and Gate

6. The Pump Basin

7. Suction Piping

8. Pump Priming

9. Bypass

10. Chemical Dosing

11. Cooling Towe r Structure

12. Winterizing

1. General

Cooling water is an essential service in any chemical plant or refinery and control of temperature plays a criticalpart in any plant process . Therefore, any w ater used for cooling picks up heat from the medium being cooled, andmust itself be cooled before being recirculated.

The cooling tow er enables this w ater cooling to be carr ied out.

Regardless of type of tow er selected there is alw ays a reservoir of w ater at the base, from which w ater isdraw n and pumped around the plant. It is returned via a header pipe, back to the top of the tow er.

The w ater is then dispersed over the w hole area of the tow er by means of w ooden slats or sprinkler nozzles.This breaks the w ater up into fine droplets similar to rain, thus expos ing a greater surf ace area and enablingcooling to be much more eff ective. The cooled water is collected in the basin under the tower and is ready for reuse.

2. Types of Cooling Towe rs

There are tw o types of tow ers essentially used in ref ineries and chemical plants:

a. Natural draft (Venturi/Chimney type)

b. Induced draft (Box type)

2.1 Natural Draft Cooling Towe rs

The natural draf t type is not often used, and is normally only used w hen the contours of the ground provide a highposition on w hich they can be located. The higher position giving unimpeded w ind area.

2.2 Induced Draft Cooling Tow ers

Induced draft cooling tow ers are furnished in tw o types, based on the direction of air f low relative to the w ater tothe w ater through the tow er:

Gad e ts ower


2/5



a. Crossflow

b. Counterflow

In the crossf low cooling tower, the sides are entirely open, and air passed through the sides to a central plenumchamber, across the dow nw ard flow of w ater, and exhausted through the top of the structure by one or morefans. Some characteristics of cross flow tow ers, compared to counterflow tow ers, are:

a. Contact surface is less eff ective.

b. Air flow quantity is greater.

c. Icing is more of a problem in w inter months.

d. Fan horsepow er may be higher.

The counterflow tow er has str aight enclosed sides, except for an air entrance near the bottom. Air is taken in atthe bottom of the tow er, rises countercurrent to the downw ard flow of w ater, and is exhausted at the top bymeans of one or more fans.

Some characteristics of counterflow tow ers, compared to crossf low tow ers are:

a. Lower air flow quantity.

b. Fan horsepower may be lower.

c. Generally low er f ire protection cost.

d. Usually low er pumping height.

e. Frequently larger basin area.

3. Cooling Tow er Location

A cooling tow er is one of the larger items of equipment, in terms of ground area, that must be located on a siteplan. Factors af fecting the location of cooling tow ers, other than convenience to w ater supply and return are:

a. Prevailing w ind

b. Noise

c. Acc ess roads

3.1 Prevailing Winds

Cooling towers should be located w ith the small side tow ards the prevailing w ind. The gives both long sides anequal intake of fresh air.

Cooling tow ers s hould not be dow nw ind or adjacent to f ired heaters, f lare stacks or any heat producing items asthese raise the ambient air temperature and w ill reduce the tow ers cooling eff iciency.

3.2 Noise

Noise levels of larger cooling tow ers can be quite high and may become objectionable if the tow er is located tooclose to continually occupied w ork areas such as of fices and control buildings, etc.

3.3 Access Roads

Access is required for the essential maintenance of pumps, chemical dosing equipment and for handling of trashscreens.

Cooling tow ers lose w ater by evaporation and entrainment (w indage), resulting in a w ater spray and fog on thedow nw ind side of the tow er making any roads continually w et. This is a traf fic hazard and can cause icing inw inter.

In general, a minimum distance of 15 to 20 meters of clear area should be allocated for air movement about the

tower.

4. Water Make up

Water makeup to a cooling tow er is necessary to replace the mechanical carryout of w ater droplets (w indage),evaporation and the blowdow n required to maintain a controlled solids buildup. Makeup water is usually added tothe cooling tow er basin.

Control of w ater level in the cooling tow er basin is via a level instrument of some description. This should belocated in the relatively still waters of the pump basin. If the instrument is of the level displacer type it should behoused in a stillw ell located in the pump basin. This protects the instrument and dampens the turbulent w ater togive a smoothed water level for measurement.

Blow dow n rate is dependent on the solids entering in the makeup w ater and the solids level to be maintained inthe system. Blow dow n is measured by a f low indicator at any point in the cooling w ater circulation system thatmay be convenient for its disposal to a sew er.

by Goog


3/5


4/5



suff icient to give access to any doors or hatches in the fan stacks and floor on top of the structures.

12. Winterizing

In cold climates s team injection is sometimes employed in the tow er to prevent the pump basins f rom freez ing. Asteam header is run around the periphery of the tow er basin, above the basin w all, and steam ejected via holesdrilled into header, onto the w ater sur face in the basin. Steam is also introduced into the pump basin via asparger; this prev ent the water fr eezing prior to being pumped into the cooling water sys tem.


5/5



Figure 1.

'reliab ili ty is yet to become the most important characterstic of modern companies' home | privacy | legal 2001 - 2012 Red-Bag

bn-dg-c01h plant layout - cooling water towers

Documents