How do I properly perform hydraulic calculations for a sprinkler system with two water sources?

The system we have is supplied by two independent street mains. Each service has a slightly different static and residual pressure. The calculations need to show both supplies. Thanks in advance.

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A high-rise building is to use a pressurized tank (half air-half water) to supply automatic sprinkler systems. If hydraulic calculations determine that 55 psi is required to supply the sprinkler system, what tank pressure is required?
a. 55 psi
b. 95 psi
c. 125 psi
d. 140 psi

We have a closed ammonia refrigeration system for a large cooler/freezer. The refrigeration equipment is located in a separate mechanical room. Total amount of ammonia is less than 10,000 lbs.

My question is explosion control per Section 911 of the International Fire Code required for the refrigeration mechanical room?

I am reading different interpretations on whether ammonia is considered a flammable gas, most say it is technically not a flammable gas but can burn and/or explode.

I'm interested in hearing everyone's take. Thanks.

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A stair is 59 inches wide, with a handrail on one side with a centerline of 1.5 inches from the edge of the stair. The other side of the stair is a wall. For the purposes of calculating a speci􀃎c 􀃏ow, what is the effective width of the stair?
a. 47 in.
b. 48 in.
c. 53 in.
d. 59 in.

Solution | Posted 09/25/20

I'm an AHJ and I know many plan reviewers and inspectors in my area are new to the trade. 

Does anyone have recommendation(s) for good plan review checklists or tools for plan review that would be helpful to rookie and intermediate-level plan reviewers?

Thanks in advance.

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​A continuous membrane with a fire protection rating constructed to limit the spread of fire is which of the following?
a. smoke partition
b. fire compartment
c. fire barrier
d. proscenium wall

Solution | Posted 09/24/20

What is the average life expectancy of a wet and dry fire sprinkler system?

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Fire sprinkler system design has been based upon all of the following except:
a. Empirical flow and pressure loss calculations
b. Application of experienced judgement and reasoning
c. Mathematical suppression modeling
d. Evolutionary changes based on fire loss

Solution | Posted 09/23/20

NFPA 22, 2018 Edition regarding filling requirement and duration - 

Section 4.2.1.4. states "The water supply shall be capable of filling the minimum required fire protection volume within the tank in a maximum of 8 hours" and at the same time Section 14.4.3 states "The tank shall be kept filled, and the water level shall never be more than 4 in. (102 mm) below the designated fire service level."

If I understand correctly, as soon as the water goes below 4-inches from the normal filled level in the tank (HHL), the makeup water supply should be starting to replenish and the pipe sizes should be provided in such a way that the tank can be filled within 8-hours.

In a fire, as the water is going down, the tank will always start full.

What is the case where the tank would be emptied out (except maintenance) and need to be refilled within 8-hours?

What if we store water in two tanks to allow maintenance - would we not need to meet this 8-hour requirement?

I'm unsure of how these two requirements work together. Appreciate any feedback.

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If, during a fire, a total occupant load of 185 people are exiting through a building's main entry (a 7-foot double door with an effective width of 6.5 ft) and the density near the main exit door results in about 0.25 persons/sqft, the time (in minutes) it would take for all of these occupants to exit the main doors is most
nearly:
a. 1.3 min
b. 1.4 min
c. 2.0 min
d. 5.7 min

Solution | Posted 09/22/20

I have a job where there are two existing diesel fire pumps that serve an existing warehouse (2 million sq. ft +).

The building is surrounded by an existing 12" underground fire supply loop. The two diesel pumps serve the space.

According to the property manager the system operate as follows:
(1) Pressure is maintained at 160-175 psi.
(2) Below 160 psi the jockey pump turns on to maintain 160-175 psi.
(3) Fire Pump #1 turns on when pressure drops below 150 psi to maintain 175 PSI. (Fire Pump - Static: 165 PSI ; Residual: 134 PSI @ 2000 gpm).
(4) Fire Pump #2 turns on when pressure drops below 140 psi to maintain 175 PSI (Fire Pump - Static: 190 PSI; Residual: 174 PSI @ 2000 gpm).

The pumps are provided by a municipal supply and a back-up private lake dedicated for the fire service.

The pumps are in parallel, so you would add the flows. And to my knowledge the higher pressure would overtake the smaller pressure.

My question is, how do you determine how to calculate the system hydraulically?

If I only use fire pump #1 for water supply, it will not be an accurate representation on how the system operates. In this case it also is very difficult to get the system to work hydraulically off of one fire pump.

I appreciate any input!

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The static discharge head is equal to the sum of all of the following except:
a. total static head
b. discharge system losses
c. suction system losses
​d. net suction head

Solution | Posted 09/21/20

We have scenario where we are using foam system under NFPA 11 for a floating roof tank with Crude Oil.

Based on our previous calculation for a prior tank the fire water demand is 1,926 gpm so we have existing 2,000 gpm pump to be able to supply the required flow. But an additional Crude Oil tank has been added and we have run our new hydraulic calculations and we come up with 4,496 gpm new flow requirement.

Is there a way we can still use the existing fire pump?

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Use Alpert's Correlation to determine the maximum temperature (in degrees Celsius) of a ceiling jet at a point 1.3 meters (horizontally) from a 1.8 MW fire which burns within a 2.2 m tall room. Assume an ambient temperature of 22 deg C.
a. 25 deg C
b. 78 deg C
c. 326 deg C
d. 384 deg C

Solution | Posted 09/18/20

We have an outdoor wooden canopy overhanging over a building entrance with the following dimensions: 45'-6" x 13'-0". The canopy has an existing wet pipe sprinkler system utilizing water/glycol mix. The building is in an area where winter temperatures can go below 0 deg F (-18 deg C).

Given the new NFPA requirement of reduced glycol mix ratio and hence the existing sprinkler system is no longer compliant with NFPA and requires to be replaced.

My question is, is it feasible and compliant to have the wooden canopy treated with fire retardant NFPA 703 approved coating/painting and hence the canopy can be considered non-combustible or at least limited-combustible eliminating the requirement to install a sprinkler system under NFPA 13 section 9.2.3?

I appreciate your feedback. Thanks

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The activation time (in seconds) of a standard response (RTI of 85 m^1/2s^1/2), Ordinary Temperature (65 deg C) heat detector within a room that has an initial temperature of 22 deg C and exposed to a ceiling plume at 78 deg C traveling at 2.3 m/s is most nearly what time?
a. 10 s
b. 36 s
c. 54 s
d. 82 s

Solution | Posted 09/17/20

Working with a 10,500 square foot building that is primarily a wood shop (as the AHJ, fire official). In this building they basically saw cut raw lumber on a large gasoline powered (vented) saw mill inside of the building (this is an issue I question as well). This is a two-part question, at the least!

The occupants claim they are a E occupancy (based on the 2012 IBC/IFC) and that they fall under the 12,000 square feet for automatic fire sprinkler requirements in chapter 9.

I look at this as a woodworking facility over 2,500 square feet per 903.2.4.1, that would require automatic fire sprinklers.

The organization is not a school, but rather consider themselves as a vocational school that serves students working on their G.E.D. along with troubled students needing extra guidance, and they pay these students. They teach life/work skills and help with job placement.

I feel this would either fall under a B-Occupancy for training and skill development not within a school or academic program, or an F-1.

Thoughts on this part?

Next, even if we would call this an E-Occupancy, would sprinklers be required since it is under the 12,000 square feet? I would think yes because of section 903.2.4.1, however the organization says no because they believe they are an E.

​I know where I am leaning on this issue, but would welcome any other input. ​I am all about helping this organization out, but also need to take safety and property preservation into account. This place keeps me up at night with all of the students and hazards present.

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What is the greatest allowed spacing among all pipe sizes between hangers for CPVC pipe in fire sprinkler systems?
a. 6'-0"
b. 9'-0"
c. 10'-0"
d. 12'-0"

Solution | Posted 09/16/20

NFPA 72 requires a battery test be run including removal of the main power supply, waiting the full-length standby time, then activating the fire alarm system for the full alarm time. After the alarm time, the battery voltage is required to be tested.

What is the pass/fail mark for the battery voltage?

In theory, if the battery output still has 20.4 V, then the last appliance on a NAC circuit would still get a minimum of 16 V and everything still functions correctly. I just can't seem to find a code reference whether 20.4 V is the correct voltage to use (where a voltage reading below 20.4 V fails the battery). 

Thanks in advance.

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A class III commodity is encapsulated and stored on shelves within a large walk-in cooler. A dry system is being designed to serve this hazard. If the storage is anticipated to be 13 ft. in height with a 17 ft. ceiling, determine the required design density with the smallest remote area for high temperature sprinkler protection using the Control Mode Density/Area approach.
a. 0.14 gpm/sqft / 2,000 sqft
b. 0.14 gpm/sqft / 2,600 sqft
c. 0.15 gpm/sqft / 2,600 sqft
d. 0.18 gpm/sqft / 2,600 sqft

Solution | Posted 09/15/20

In an existing building utilizing a “booster pump” or unlisted fire pump for a standpipe or sprinkler system, is there a suggested annual flow test procedure?

I realize there is no manufacturer’s data (0%,100%,150% rated capacity) to compare the results against.

Should it be excluded from the annual flow test requirements, and just flowed during the 5 year roof top flow?

I would appreciate input as well as, what others in the industry are doing to address this fairly common scenario.

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​Does anyone have experience with a specific fire extinguisher for fires involving platinum catalysts? I know this would generally fall under the Class D type of extinguishers but was wondering if there is a platinum specific extinguisher like there is for lithium fires (lith-x brand). Also, if you do have experience is there any difference in operation besides a regular extinguisher (for example how the agent is propelled)?

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In an NFPA 13R system does the FDC check valve need to be accessible?

In 13 it states it is required, but I can't find it in NFPA 13R. Section 6.11.4 talks about ball drip for check valve, but I do not see anything on accessible. I’m sure I’m missing some code path that references 13 possibly? Thanks.

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