Coastal and saline environments

Coastal and saline environments

Water source selection, corrosion control, equipment protection and calculations of a sample circuit

A fountain in a coastal city can be a part of the experience of being by the sea; From a city square with short fountains to a water show in the vicinity of the pier and tourist complex. The success of such a project depends on the coordination of the demonstration design with the actual beach conditions: wind, salt, humidity, sand, changing water levels and limited access for repairs.

The first engineering decision is the choice of water source. A water feature built by the sea does not necessarily have to work with sea water. This choice affects the type of equipment, treatment design, water consumption, maintenance cost and even the location of the spectators.

In this chapter, the principles of decision making and a computational example are reviewed. The example numbers are educational assumptions and are not considered product specifications or GSO's implemented projects.

53–1. Three different structures for a beach fountain

Before designing, it should be determined in which group the project falls.

In the first option, the inside of the pipe may be in contact with fresh water, but the outside surface of the same pipe is exposed to sea salt. Therefore, the internal and external conditions of the equipment must be recorded separately in the technical specifications.

The third option is not defined simply by removing the tank and connecting the pump to the sea; The catchment and the return path are themselves an engineering subsystem.

For a basic comparison, all three options should be evaluated based on the same display quality, operating hours, and maintenance service level.

53–2. environmental certificate; Necessary information before choosing equipment

The phrase "suitable for coastal areas" is not enough to buy equipment. The designer must prepare an environmental certificate that covers at least the following:

• Temperature and quality of water in different seasons;

• Salinity, chloride, pH and suspended matter;

• Chemicals used in purification and washing;

• Immersion period, blackout periods and the possibility of soaking;

• Wind direction and spray transfer path;

• Operating levels and storm conditions, if connected to the sea;

• Access position to remove pump, light and nozzle assembly.

Chloride and free chlorine are two different parameters. Chloride is one of the soluble ions in water; Free chlorine is an indicator related to disinfection. Measuring one does not replace the other.

The output of this step should be a table with "parameter", "measured value", "design scope", "measurement method" and "sampling date" columns. The data of a calm beach day alone does not represent annual conditions.

53–3. Knowing the corrosions affecting the fountain

Three mechanisms are particularly important for initial screening:

Pitting Corrosion: Localized damage that can lead to pitting despite a relatively healthy surface appearance.

Crevice corrosion: damage in crevices, sub-sediments and some connections where the local water conditions differ from the main flow.

Galvanic corrosion: Corrosion caused by the electrical connection of different metals in the presence of a conductive medium.

The Outokumpu guide introduces chloride, temperature increase and chemical conditions as factors affecting local corrosion of stainless steel. The choice of alloy should be adapted to the actual working environment. Stainless Steel Corrosion Resistance Guide ^[343]

In the project maintenance file, for each damage, the exact location, depth or extent, photo and connection status should be recorded. A phrase like "slight rust" is not enough to decide whether a part will continue to work under pressure.

53–4. Selection of materials at the level of the complete set

The material of the pump body or nozzle is only part of the required specifications. Shafts, screws, springs, seals, glands, and internal parts should also be checked.

Families such as high-alloy stainless steels and certain duplex grades may be considered as options; The final choice depends on the application conditions. The name of an alloy family is not an endorsement of all its grades for seawater. Outokumpu's review of materials for marine structures ^[344]

In the introduction of the GSO water screen nozzle, the use of 316 steel is suggested. For coastal application, this specification should be checked along with verification of water conditions and specifications of other assembly components. Introduction of GSO water screen nozzle ^[345]

53–5. Construction and installation details

The quality of construction can change the result of choosing materials. Clean surfaces, proper handling of welding effects and reduction of deposit accumulation areas are part of corrosion control. Construction and Surface Protection Recommendations in the Outokumpu Guide

In the executive map of the coastal project, these details should be specified:

• The method of draining the remaining water in the collectors;

• Location of openable joints;

• Necessary space for tools and part exit;

• Surface protection method after construction;

• The possibility of washing behind the bases and under the equipment;

• Washing water collection path.

For example, if opening a nozzle requires destroying the flooring, choosing a more expensive alloy alone will not solve the maintenance problem. Serviceability should be designed at the same time as the appearance of the fountain.

53–6. Cathodic protection and sacrificial anode

Some manufacturers offer sacrificial anodes for certain equipment. Otterbine has introduced a zinc anode kit for brackish water applications and emphasizes its periodic maintenance and replacement. This recommendation is related to the products and conditions declared by the same manufacturer. Otterbine protective equipment and kits ^[346]

In a project with such protection, the delivery documents should include anode type, installation location, inspection method and replacement criteria. Installing a zinc part on the body without checking the connection and protection scheme is not a reliable basis for verifying performance.

Coordination between corrosion design and electrical design is essential. The protective conductor or necessary connection should not be cut to remove the corrosion. Any electrical isolation solution must be compatible with electrical safety requirements and the protection plan of the complex.

53–7. computational example; The effect of salt water density on pump power

Consider a hypothetical demonstration circuit with the following data:

Conversion rate:

$Q=\frac{36}{3600}=0.010m^3/s$

Approximate input power:

$P=\frac{\rho gQH}{\eta }$

$P=\frac{1025\times 9.81\times 0.010\times 18}{0.60}=3017W$

Therefore:

$P\approx 3.02kW$

If we just change the density to 1000 kg/m3 and other assumptions remain the same:

$P_{\mathrm{آب\; شیرین}}\approx 2.94kW$

In this comparison, the power increase due to density is equal to 2.5%. This number does not reflect the total cost or actual consumption of a saltwater fountain; It only isolates the density effect under the assumed conditions.

Pressure equivalent to head of 18 meters for salt water, for example:

$\Delta p=\rho gH=180995Pa\approx 1.81bar$

This value is the equivalent head pressure of the entire circuit and should not be directly entered as the required pressure of the nozzle.

The final selection of the pump depends on the performance curve, actual efficiency, operating range, engine power and fluid compatibility. The above calculation alone is not the basis for ordering the engine.

53–8. Example of salt balance; Why is compensation water important?

Suppose the fountain tank has:

• Initial volume of 10 cubic meters;

• Hypothetical concentration of dissolved salts of 35 kg/m3;

• thorough mixing;

• No droplet discharge, discharge, sedimentation or chemical reaction within the calculation range.

This concentration is an educational volumetric assumption and should not be confused with the gram/kg salinity unit.

Initial mass of salt:

$m_s=10\times 35=350kg$

If a cubic meter of water evaporates and salt remains in the tank:

$C_1=\frac{350}{9}=38.89kg/m^3$

That means the concentration increases by 11.1%.

Now let's compare the two volume compensation methods:

In the second case, the water level has returned to its original value, but the salt concentration has increased by 10%.

So controlling the tank level is not a substitute for water quality control. In actual operation, evaporation, spraying, filter washing, discharge and compensation water quality must be included in the balance at the same time; The framework of this balance was presented in chapter 51.

53–9. Water catchment, sand and sea level change

In a fountain connected to the sea, the pump inlet conditions should be checked for several conditions: the lowest operating level, the highest water temperature, the allowable clogging of the catchment and adverse flow conditions.

The water intake check sheet must give clear answers to the following:

• How far is the suction opening from the bed and the water level?

• How are sand and floating materials controlled?

• How and with what access is the net or strainer cleaned?

• What stop command is issued in case of level loss or obstruction?

• How is the suction capacity of the pump controlled in the worst case?

The net positive suction head control available should be compared with the pump requirement and margin determined for the same project.

The levels affecting the operation should also be recorded separately from the levels and loads used for the design of the structure in hurricane conditions. Stopping the pump does not protect the structure against waves and flooding.

53–10. Electricity, lighting and sign installation place

In the electrical design of the coastal water feature, the exposure conditions of each piece of equipment must be specified on the map: submerged, exposed to splash, open coastal or equipment room.

In the purchase specifications, in addition to the degree of enclosure protection, the following items should be requested:

• Manufacturer approval for installation environment and method;

• Cable, gland and connection specifications;

• Method of controlling the humidity inside the chamber;

• Inspection program and electrical tests;

• Conditions for replacing or repairing damaged connections.

The term IP68 alone does not confirm the compatibility of all equipment components with salt water.

The location of the control panel and equipment should be selected according to the water level of the design, the spraying path and emergency access. The cable route must also be independent of the equipment's bracing task; The power cable should not take the role of the rope holding the floating assembly.

53–11. Wind and spray range

In a saltwater fountain, the splash range is part of the project's effect range. The path of droplets should be checked with respect to sidewalks, cars, green spaces, building facades and equipment air intakes.

To control the display, three states can be defined:

Threshold values should be determined by experiment and conditions of the same location. For some product lines, Otterbine also offers wind-based pitch-and-then-stop control; This capability is a useful principle for designing control logic. Wind control in Otterbine equipment

In the delivery of the project, only the number of the anemometer should not be recorded; At the same time, prepare a real map of the surrounding wetting.

53–12. Water quality and public exposure

The choice of sea water is not considered a health confirmation of the water fountain. The type of people's contact, the production of suspended droplets, the quality of the source and the method of maintenance should be considered in the project evaluation.

CDC guidelines for decorative fountains emphasize water management, cleaning, and disinfection and recommend cold potable make-up water. Therefore, this guide cannot be considered as a general approval for the use of sea water; The marine system needs special consideration. CDC Guidelines for Decorative Fountains ^[347]

In the sample circuit of this season, people are not expected to enter the water. Turning it into an interactive fountain will require a review of the design and water quality criteria.

For unloading, the place of receipt, salinity, chemicals and the conditions of the responsible authority must be specified. The return of water to the sea should not be assumed to be permitted solely on the basis that the water source is marine.

53–13. Washing and maintenance

The maintenance program should be applicable from the design stage. The path of washing water, the place of discharge and the possibility of separating the equipment are part of this program.

Aquatique Show considers it possible to use its water screen in sea water, but for long-term use, it suggests rinsing with fresh water and selecting materials suitable for salinity. This description is related to the same product family. Aquatique Show water screen technical questions ^[348]

For the project, prepare a program with this structure:

Service interval should be corrected with operating data. Logging "date done" without logging "observed status" is of limited value for failure prediction.

53–14. Test and delivery

Before delivery, four sets of documents are required:

Equipment documentation: list of components, type of parts, approval of use and maintenance instructions.

Performance results: flow rate, pressure, input power, display quality and water conditions during the test.

Control and Protection Results: Stop performance in level drop, pump faults, control disturbance and wind conditions as per design.

Operating documents: final drawings, evacuation route, spare parts list and service schedule.

A successful short test does not prove the corrosion life of the equipment. For the next monitoring, a base photo should be prepared from the selected points and their specifications should be included on the map.

The stop and warning test must also be done in a controlled manner; Deliberately creating destructive conditions to prove protection is not a good way to deliver.

53–15. Economic comparison of options

Comparison of fresh water and salt water should show common and different costs separately:

• Purchase and installation of equipment;

• compensation water and washing water;

• energy;

• Purification and monitoring;

• access, removal and re-installation of equipment;

Consumable parts and replacements;

• Display stop and maintenance force.

For each proposal, the annual consumption amount, the number of services and the basis of the estimated replacement of parts should be included. A cost that does not have sufficient data should be presented as a scope and scenario.

The cheapness of the water source alone does not determine the economic outcome of the project. The final decision is defensible when the display quality and service level are the same in the compared options.

53–16. Suggested images and documents for page layout

Figure note from the source manuscript

Figure 53–1: General view of a coastal fountain

Choose an image from the archive that shows the connection between the fountain and the sea, spectators and the sidewalk.

*Subtitle:* "The location of the coastal fountain according to the viewer's view, wind and splash area."

The type of water source should be mentioned in the subtitle only if there is documented information about the project.

Figure note from the source manuscript

Figure 2–53: Comparison of three water supply structures

Draw three schematics side by side: the fresh water circuit, the salt water recirculation circuit and the circuit connected to the sea. The path of compensating water, washing and draining should be marked with different colors.

*Subtitle:* "Water source selection determines facility structure and maintenance schedule."

Figure note from the source manuscript

Figure 53–3: Detail of a serviceable assembly

Actual photo of nozzle, connection, base and access path selected. Mark the place of opening and exit of the part on the image.

*Subtitle:* "Accessible parts allow inspection and replacement of parts."

Figure note from the source manuscript

Figure 4–53: Diagram of salt balance tutorial example

Three tanks are represented by the numbers of Section 8–53: initial condition, after evaporation and after compensation with salt water.

*Subtitle:* "Returning the water level to its original value does not necessarily return the salt concentration to its original value."

Put the words "educational example" on this image so that it is not confused with the data of a real project.

At the end of the design, the coastal fountain file should provide the client with the choice of water source, material approval, circuit calculations, sprinkler range, water management plan and maintenance method. These documents will be the basis of informed purchase and follow-up exploitation.