In regards to the Darcy-Weisbach equation and Moody Diagram - why does laminar flow (Reynolds number less than 2,000) correlate to a higher friction factor than turbulent flow?
Should turbulent flow correlate to a higher friction factor and therefore a higher pressure loss per foot of pipe? I'm designing a system using a newly listed antifreeze with a viscosity of over 300 cP at -25 deg F. This causes a very low Reynolds number (around 250) since viscosity is in the denominator of the Reynolds equation. With a low Reynolds number, the Friction Factor is high (64 / Re) which makes sense because I'm calculating for antifreeze, but I don't understand how laminar flow correlates to a higher Friction Factor. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe
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Do fire pumps typically come balanced from the factory for the desired flow and pressure?
I know they are supposed to, but (just like any other pump) is their balancing done similar to a regular pump to get the desired pressure so that the pump operates at its rated duty point? I am aware that many factors affect final pressure discharges (such as friction loss, etc.). Have you ever seen pump manufacturers calibrate pumps to the desired flow/pressure in the field? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe How close can hanging baffles be spaced together before sprinklers are required below (and possibly above) them to provide full sprinkler coverage?
I have a situation where about 20 acoustical baffles will be hanging 6-12 inches below the ceiling. The baffles are 18-inches by 10-feet long, spaced 8-inches apart. I've looked at providing sprinklers above them at the ceiling level, and it isn't clear cut; each individual obstruction is less than 4-feet wide, so I can see NFPA 13 (2019) Section 10.2.7.1.2(2) applying as long as you can sprinkler between them. But I think the baffles are located too close together to be considered non-continuous obstructions and their proximity would obstruct the sprinkler spray pattern development. I've looked at Section 9.5.5.2, where continuous or non-continuous obstructions less than 18-inches below the sprinkler deflector prevent the sprinkler pattern from fully developing, but that section states that as long as no additional floor area is created then no additional sprinklers are required. Having a tough time believing that only sprinklering above the baffles will fully protect beneath them. Any help is appreciated! Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe We have a client that is looking at building a fireworks retail store on the edge of town. The county is requiring the store to be sprinklered, but no one can give any direction on how to protect it and NFPA does not call out coverage for this type of business.
It is an H-3 occupancy, covering roughly 10,000 sqft. Is there a standard that offers guidance on how to go about protecting a facility like this? Thanks in advance. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe We have a project where we are trying to distinguish between frame and girder construction versus panel construction.
If we have steel frame and girder construction, beams are less than or equal to 7'-6" apart, but there is a corrugated deck that allows for heat flow above the girder (and wouldn't trap all heat), does this qualify as frame and girder? Will the maximum deflector distance be 22-inches if there is a corrugated deck? My assumption is "no" since heat is not capable of being trapped and a sprinkler needs to be placed in each bay within 12-inches of the deck. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe I'm working on a a high-end hotel which will have a vertical turbine fire pump above a water storage tank.
Can we waive a minimum pump submerge depth by installing an anti-vortex plate between the pump's bell and the strainer? The fire pump is a 1,500 gpm vertical-turbine type, located directly above the water tank. The tank depth is 6'-3" from the overflow bottom down to the tank floor. The water tank area is 2,408 sqft. The selected pump recommends 51.63-inches as a minimum submerge depth. This is in addition to a 12-inch clearance between the bottom of the strainer and the tank floor. The water level to be maintained inside the tank then must be 63.63-inches (95,511 gallons). The remaining active volume in the tank after extracting the required volume will be 112,582 - 95,511 = 17,071 gallons. This is not enough to run the pump set for the required time under NFPA 13 2019 (Table 19.3.2.1 and 19.3.3.1.2). Can adding an anti-vortex plate between the pump's bell and the strainer waive this minimum submerge depth? If not, what might be a recommended solution for this? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe I'm having trouble finding a definitive code section (in IFC or NFPA 101) about prohibiting open flames in biosafety (BSC) cabinets.
I have a position paper from the Institutional Biosafety Committee which references a lot of well-known organizations (such as WHO, NIH, CDC, etc.) and some manufacturers who strongly discourage the use of open flames in biosafety cabinets saying there are better alternatives to sanitize biological samples. I've also seen many college ESH references saying the same thing. The hazard is catching the HEPA filter on fire and in general I've read that an open flame is not good for maintaining the laminar air flow through the cabinet. However, finding something in code or selwhere prohibiting the use has proven elusive. Anyone have any thoughts or references that would help here? Unfortunately, it may take something directly from code to get the practice prohibited at my place of work. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe My question is more based on principle rather than design.
I have been in the industry for over years and keep coming to the same question lately; who is responsible for the end product on design and install? I've had several projects in the last year where a "mechanical engineer (plumbing/HVAC)" are doing the layout for the schematic and bid drawings and don't have the complete knowledge of fire protection. I've had to deal with issues ranging from head spacing to pump specifications... and none of them have been close to code. Specifically, I have a 3-story building with the 3rd floor at 30'-0" above apparatus / grade so there should be no need for standpipes. The plan/specs require an automatic-wet standpipe with a 125 psi @ 500 pump. I sent an RFI on why the need for the automatic-wet standpipes, where we can do away with standpipes or go to manual/wet and I was rejected. Ultimately, we were told to follow the prints....but we are "delegated" design. Eliminating the pump and standpipes, we could have saved the county $110,000+ (electric included). I now have a church with 36-ft throw sidewalls and the engineer would like to stay with sidewalls and not have any pipe crossing the room; it's not possible with the supply. In the end, who is responsible for the design and performance of the system? If the contractor follows the plan/spec, is he liable because he is the "delegated" designer? But if the delegated design needs to change and is rejected, who is liable? How do you bid plan and spec project if there are multiple issues with the bid plans? Do you redesign and bid it correct? No, you won't get the job. Or, do you bid per prints and then not be allowed change orders because you are the delegated designer? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe I have two large ducts 20-inches below sprinklers. One duct is 32-inches wide, the other is 42-inches wide. There is maybe 4- to 7-inches between them, only a couple inch gap on each side, running the length of a hallway.
The only rule for a continuous obstruction I can find says no coverage is needed below if the obstruction is under 4-feet. Individually these ducts aren't over 4-feet, but how does NFPA 13 address multiple obstructions like this? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe If a building has an NFPA 13R system and the building is now being converted to a commercial building and does not require a sprinkler system for new construction, can you remove the system?
Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe Can Permatex Form-A-Gasket No. 1 Sealant be used in a fire sprinkler system to seal the pipes and threaded fittings instead of PTFE tape?
Also, if the installer added jute (fiber), is this acceptable? I do not believe that NFPA 13 or UFC Criteria prohibits this practice, but wanted to ask. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe I am a Fire Protection Engineer in Victoria working in a sugar refinery where we are proposing to protect existing raw sugar and white packaging storage. The raw sugar storage has piles of unrefined sugar in the warehouse which often clogs the sprinklers (like all other equipment in the area).
My advice to the client was more strict inspections and maintenance in this area, as well as to place metal guards to try and minimize buildup around the sprinklers. The white packaging storage, although not as dirty as the raw sugar storage, has fine dust particles throughout. I'm not as concerned about this area. We are not trying to re-invent the wheel here, and I'm sure there has been many acceptable solutions to minimize building on sprinklers. What would you recommend to the client here to minimize the buildup? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe NFPA 13 states that for hydraulically calculated sprinkler systems the fire department connection (FDC) pipe can be less than 4-inch diameter, but not less than the system riser.
What size should the fire department connection feed pipe be for a 6-inch riser, or an 8-inch riser? Can the FDC pipe still be 4-inch for these larger risers? I have some clients believe that 4-inch is the maximum no matter what, and some say if the riser is 6-inch or 8-inch that the FDC pipe needs to match the larger riser size. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe When 20 or fewer sprinklers are involved in a modification, codes and standards suggest new hydraulic calculations are not required.
What is the scientific or engineering basis for the "20-sprinkler" number? Is there some study or analysis that found this to be a reasonable breakpoint? I'm researching whether we should require full plans for less than 20 sprinklers. Thanks! Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe We are currently working on a project with a building height of 36-feet that currently has K16.8 ESFR sprinklers installed to protect open rack storage of Class I-IV commodities at 12-feet in height.
The hydraulic calculations are based on Ordinary Hazard Group 2, with a 0.20 gpm/sqft density over 1,500 sqft with a starting pressure of 7 psi. The design area is based on 18 ESFR sprinklers flowing at 100 sqft per sprinkler. The total sprinkler demand is 834 gpm. They are calling this an "ESFR-Ready" sprinkler system. It seems to me that the building height would drive the starting pressure for this scenario and the calculation should actually be 12 sprinklers with a minimum starting pressure of 52 psi when using K16.8 ESFR sprinklers. This comes after examining Chapters 12-20. What would the lowest starting pressure be for K16.8 ESFR sprinklers protecting open rack storage of Class I-IV commodities to 12-feet in height with a building height of 36-feet? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe Hi, all! I came across this forum by accident at the perfect time. I am having a dilemma with the building department.
I am conducting an annual flow test on a 500 gpm (at 100 psi) fire pump from the test header off the pump discharge with the valve closed as to not disturb the system. I achieved 100% and 150% with no issues and the curve was almost identical to the pump's design curve. The Department of Buildings is rejecting the test because the test was conducted from the discharge manifold. I was trying to avoid flowing from the roof because it's a very high end building and did not want to risk anything. Now, this system has been recently installed and the jockey pump panel is reading 100 psi on the system. When I tested my pump, it pushed out 168 psi on discharge and 48 psi on suction for a net of 120 psi (the pump is rated at 124 PSI for churn). I can conduct the test from the roof with no issue as long as the building feels comfortable with their storm drain's ability to handle the flow, but I am worried about over-pressurizing the system. Am I permitted by code to test off the header and not from the roof? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe I have a question with regards to the ESFR dry pendent 'box-in-a-box' freezer installation.
How do you handle the large ceiling-hung condensing units that are present in basically every large cold storage freezer/cooler? Do you provide some kind of a supplemental system below the units? I see that the new antifreeze solutions are listed for storage occupancies, but specifically exclude ESFR systems. We have a large cold storage freezer where the mechanical consultant has specified ESFR dry pendents, but provided no direction on how to address the condensing units. I'm sure I'm not the first to run into this issue, and I am curious how others have dealt with it. Thanks in advance. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe What factors do you consider when deciding whether to specify brass or chrome valves, fittings, FDCs, sprinklers, etc?
Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe I'm looking at requirements for hose valves (FHV) at exit passageways and I'm a little confused.
The code states that a hose connection is required: "in every exit passageway at the entrance from the exit passageway to the other areas of a building. Exception: Where floor areas adjacent to an exit passageway are reachable from exit stairway hose connections by a 30-foot (9144 mm) hose stream from a nozzle attached to 100 feet (30 480 mm) of hose, a hose connection shall not be required at the entrance from the exit passageway to other areas of the building." What is the rationale behind locating a hose valve at the entry of the exit passageway? Is this for fighting fires outside? I have been told it is so that the fire department can quickly locate the hose valve, but I can't imagine they would want to run their hose 130-feet in the passageway just to then have another connection in the stairwell. My passageway is about 100-feet long and it connects to a stairwell that does have a fire hose valve located at the main landing. Why would I need a fire hose valve at the entry of the exit passageway also, which is 100-ft away? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe I have a fire hydrant in a planter curb, and we will have some trash enclosures nearby.
What is the required minimum clearance for a trash enclosure wall from the hydrant itself? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe I have a project with 90 apartments, and each unit has a recessed telecom (fiber-optic) panel in a closet that would normally not require a sprinkler. The project is under NFPA 13R.
The Authority Having Jurisdiction is requesting sprinklers in these closets, feeling that these are now combustible after the telecom panel is installed. Is anyone else running into this? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe We have a project with a comment from the AHJ stating that the dryer vent cannot terminate to the exterior condominium wall, which is the egress wall for the condominium exit exterior breezeway on that floor.
We're under NFPA 101 (regarding Section 30-3.6.3 for Unprotected Openings). Is a duct penetration considered an unprotected opening? Dry vents cannot have fire/smoke dampers, so can it just be a metal duct? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe I have a project that is under NFPA 13R (2019) and NFPA 14 (2019). In section 7.10.1.3.1.1 of NFPA 14, it states that in cases where NFPA 13R system demand is higher than the standpipe demand, the system demand applies.
Is it ever possible to have a residential sprinkler system with a higher demand than a standpipe? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe We have a project with a limited water supply that makes it impossible to automatically replace the required fire water in 8-hours.
Could a larger (1.5 x the required fire flow) water storage tank be an option? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe Are sprinklers required beneath a McDonald's play structure?
On past projects I have designed roof-level sprinkler protection for the play area additions, but we are becoming involved in a government project where there is ceiling level protection and they are requiring protection beneath what are apparently several areas of the play structure that are greater than 4-feet in width. I guess I can't argue that it is not "fixed-in-place." I'm sure most of these planes are higher than 24-inches above the ground, so that exception doesn't apply. Sent in anonymously for discussion. Discuss This | Submit Your Question | Subscribe |
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