FluidFlow

Fire Protection System Design

© Flite Software NI Ltd

1  Introduction        2

2  Design Calculation 1: Fire Sprinkler System.        3

3  Design Example 1: Fire Sprinkler System.        5

4  Design Example 2: Fire Sprinkler System.        7

5  Design Example 3: Fire Hydrant System.        10

6  Conclusion        13

1. Introduction

FluidFlow lets you perform hydraulic analysis of fire protection systems and ensure you develop your design in compliance with the requirements of the NFPA guidelines. FluidFlow is therefore ideal for modelling of fluid behaviour within complex piping systems for applications such as petrochemical plants, power plants, refineries, ships, FPSO’s, airport facilities, and offshore platforms.

FluidFlow is provided with a database of sprinklers, hydrants, pipe materials, pumps, valves and you can also add new components to this database, a task which you only need to perform once as they will be stored for all your future design projects.

When determining pipe pressure losses, engineers can choose from either the Hazen Williams or Darcy-Weisbach friction loss models.

The unique features within FluidFlow allow engineers to automatically size pipes, pumps, control valves orifice plates and a range of other equipment items. This in turns helps speed up the design process saving you time and resources. Users have reported saving up to 40% time and capital expenditure per project by switching from other competitor software products to FluidFlow. Do you have a fire protection system to design or need to accelerate the design process ? Contact our team for a discussion support@fluidflowinfo.com. Further information is available at: www.fluidflowinfo.com.

Engineers use FluidFlow to design and develop sprinkler systems, deluge systems, foam solutions systems, firewater ringmain systems. This document will detail an example calculation vs a worked example of a fire sprinkler system and also outline a number of case studies as described by FluidFlow users.

FluidFlow is developed by Flite Software Ltd, an ISO9001:2008 registered company.

2. Design Calculation 1: Fire Sprinkler System.

Reference: Piping Calculations Manual, Example 2.17, Pg 128.

Description: A sprinkler system for a small warehouse has three branch pipes with four sprinkler heads, each spaced at 12ft apart. The branch lines are spaced 15ft apart and connect to a riser pipe 20ft high from the fire pump. The riser pipe is 2 inch schedule 40. The branch lines are 1 inch schedule 40 except for the section from the top of the riser to the first sprinkler on each branch line, which is 1.5 inch schedule 40. All sprinklers have a 0.5 inch orifice with K = 5.6. Use a Hazen Williams C factor of 100 for all pipes. Calculate the flow through each sprinkler.    

FluidFlow Model

Calculated Results

Result Comparison:

Commentary:

As we can see from the above table of results, the calculated FluidFlow results for this entire system compare very well with the hand calculation. This system is based on using the Hazen Williams friction loss approach.

3. Design Example 1: Fire Sprinkler System.

The main purpose of the project was to design and dimension a sprinkler system for chemical tanker propylene oxide piping. Propylene oxide is a volatile liquid which is why the propylene oxide cargo piping has to be cooled during the load and offload.

This system consists of 185 sprinkler nozzles, 923 M of pipework and associated ancillary fittings. A part-plan overview of the system is provided in Figure 3.1.

Figure 3.1: Propylene Oxide Sprinkler System (Part-Plan).

The cooling system had to comply with the US Coast Guard rules (46 CFR 153.530 - Special requirements for alkylene oxides). Propylene oxide cargo piping had to be covered with a uniform water spray of 0.175 l/m2 sec. The system was arranged with the sprinkler nozzles and total water flow in the system was defined by calculating the sprinkler nozzle protected area with required water spray. Calculated flow in each nozzle was 31.5 l/min.

The main challenges posed by this system were as follows;

1. The balancing of the flow between the sprinkler nozzles.
2. Arranging the system without pressure reducing valves.
3. Sizing of all pipes throughout the system.

Figure 3.2 provides an overview of the fire pump performance. We can clearly see the duty point where the system curve intersects the pump capacity curve.

Figure 3.2: Dedicated Fire Pump.

4. Design Example 2: Fire Sprinkler System.

The IRClass (Indian Register of Shipping), a leading Classification society and member of IACS, has just completed the new construction survey of the MV Indira Point which was completed two months ahead of schedule at a cost of approximately USD 25 million. This vessel is a high value, technologically sophisticated Buoy Tender cum multi-purpose vessel built by Cochin Shipyard Ltd (India) under single class. The new vessel MV Indira Point, 72 mts long, 1350 tons DWT, fitted with Heli-deck and a 35 tons capacity crane for handling buoys in deep seas was handed over to the Directorate General of Light Houses and Light Ships (DGLL India) in April 2015.

IRClass Chairman and Managing Director (CMD) Mr Arun Sharma said “This single class project and its successful completion represents a major step forward for IRClass”.

This project required the evaluation of the operating performance of an existing pumped sea water fire fighting system serving a heli-deck, determine the plant limitations based on a revised system layout, identify any changes required and potential plant optimisation opportunities.

As per the contract specification for the vessel, a helicopter deck with D-Value of 16 meters was to be arranged above the forecastle deck and helideck to meet the requirements of DNV (Class).

DNV Rules for classification of ships Pt.6 Ch.1 Sec.2 E301 states, a fixed foam application system consisting of either monitors or pop up nozzles with minimum capacity of at least 6 l/m2/min shall be provided. The system shall be able to cover the whole of the helicopter landing area, and with sufficient foam medium to enable the foam application rate to be maintained for at least 5 minutes.

A fixed foam application system consisting of pop-up nozzles and foam skid connects with a sea water supply assembly installed onboard the vessel as per the above CLASS requirements.

As per the foam system design, there was a minimum flow requirement of 90 m3/hr of sea water and the pressure required at the foam skid was 8 bar.

The vessel had an existing ballast pump which was capable of 150 m3/hr at 9 bar. The team at Cochin Shipyard Ltd checked the suitability of the existing pump for this upgraded application using FluidFlow. The re-worked pipes and fittings were modelled together with pump performance data which was provided by the pump manufacturer.

Figure 4.1 below provides a part-plan illustration of the overall system.

Figure 4.1: Fire Fighting System (Part-Plan).

The design was developed further and from the detailed analysis, it was observed from using FluidFlow that the existing pump was capable of meeting the requirements of the upgraded installation.

The final plant design is set out in Figure 4.2.

Figure 4.2: Fire Fighting System (Final Design).

Conclusion: By using FluidFlow, the team at Cochin Shipyard were able to predict the performance of the upgraded system whilst retaining the existing circulating pump. The engineers were able to establish that the existing pump could be successfully re-used, thus avoiding the need for an additional pump which was not anticipated project signing stage. This helped the team avoid further re-work to the existing plant which is installed in a plant space which is already a constrained area. This helped the design team achieve considerable cost savings which had not been anticipated at the project outset.

Testimonial: 

“We use the liquid, gas, and Dynamic Analysis and Scripting of FluidFlow and make extensive use of its simulation capabilities for engineering systems as cooling water, fuel oil, ventilation, etc., including for the development of new systems. Before we bought we carried out extensive product research and chose FluidFlow because of its completeness and value for money. We have been receiving excellent support from FluidFlow team. We have found Flite Software to be extremely knowledgeable and helpful, really excellent."

Arun Kumar V-Machinery Design

Cochin Shipyard

5. Design Example 3: Fire Hydrant System.

A notional fire hydrant layout has been developed for an industrial site based on maximum permissible distances between hydrants and from buildings etc. The notional design included 42 underground fire hydrants, diesel and electric (duty and standby) pump sets, tees, bends and interconnecting pipework. Figure 5.1 provides an illustration of this notional layout.

Figure 5.1 – Notional Fire Hydrant Layout.

The designer was required to establish flow distribution throughout the system, pressure losses, pressure available at outlet nozzles and review pipe velocity levels to ensure they were in compliance with the requirements of NFPA – Standard for the Installation of Sprinkler Systems.

A model of the system was quickly created in FluidFlow using the database of pipes and components included in the software. The model layout was based on the initial layout of that proposed on the site plan. Figure 5.2 provides an overview of the model.

Figure 5.2 – FluidFlow Fire Hydrant Model.

This model was developed using the 2.5 inch AVK fire hydrant. The hydrant pressure loss data was therefore added to the FluidFlow database which enabled this specific hydrant to be modelled in this system.

Consideration was also given to the resistance downstream of the hydrant, i.e. the resistance from the connected fire hose, in this case a 100ft long 2.5 inch hose. The associated roughness value for the hose was therefore included in the overall system modelling analysis.

Consideration was also given to the discharge nozzle diameter and different sizes were modelled based on the clients specific requirements. These subtle changes therefore had an effect on the calculated K value for the nozzle.

The system included 42 fire hydrants, diesel and electric (duty and standby) pump sets, tees, bends and a total pipe length of 3256 M.

Modeling this system using FluidFlow allowed the designer to develop a detailed insight into the operating performance of the plant and also quickly identify any pipe velocities which exceeded the design value of 20 ft/s as set out in the NFPA Guide. The pump operating speeds were also optimised to ensure the required flow rate and pressure requirement was maintained to the hydrants.

Figure 5.3 provides an overview of the pump performance. We can clearly see the duty point on the capacity curve and on the efficiency curve. The calculated results allow us to view the pump power requirement, NPSHr vs NPSHa, fluid density, duty pressure rise etc.

When developing this system, the designer had initially used PVC piping. However, the insurance provider requested that the piping material used was steel. The designer was able to quickly switch the pipe material selection from PVC to steel as both materials are available from the FluidFlow pipes database. Note, there are many other pipe materials available in the database such as PE, cast iron, copper etc.

The system was recalculated based on these changes being applied, updated results exported to Excel and submitted to the insurance providers. The project design was subsequently signed off, installed on site, tested and commissioned successfully.

Using FluidFlow for the development of this system helped the client accelerate project delivery with the added benefit of creating an efficient system design. Subsequent changes could also be applied to the model and the effect of these changes understood in an instant. 

Sidi A. Bakarr

6. Conclusion

FluidFlow’s powerful functionality, available pressure loss models and database of sprinklers allow you to design and model fire protection systems quickly and efficiently.

Engineers can expand the database by adding new sprinklers, hydrants, valves etc. All new data is stored in the database for your future modeling projects.

FluidFlow will automatically size pipes, pumps, control valves and orifice plates meaning the overall design approach applied to your fire protection systems is simplified and the design time required is reduced significantly.

If you have a specific design application and wish to use an intuitive user friendly program to speed up your design process, contact us at: support@fluidflowinfo.com.

Testimonial:

“FluidFlow is fast, easy to use, accurate and a reliable package. The software drastically cuts design time - these benefits apply not only to the designer but also to the peer review team. During operation of the built systems, the agreement between running plant pressure readings against design data was highly accurate. That bought my full trust in the package”.

Mat Landowski, Lead Process Engineer