Friday, February 27, 2015

Diesel Engine Cooling Loops

Photo of Clarke Fire cooling loop name plate
Make sure you are in compliance with FM Global's requirements for cooling loops on diesel engines. FM Global Approval Standard 1333 was updated in 30 Nov 2013, but compliance was not required until 1 April 2015.

Clarke Fire has an excellent write-up on their web page that you can find here. But, we wanted to summarize the key requirements.


    Photo of new Clarke Fire cooling loop sensor locations
  • FM Approval - Cooling loops are now required to be approved and therefore they will have the FM logo on a nameplate.
  • Low Raw Water Flow Alarm - This switch is set to activate at 75% of the required flow rate.
  • High Raw Water Temperature Alarm - This switch is set at 105F (40C).

Wednesday, January 15, 2014

Installation of Diesel Fuel Tanks for Fire Pumps

After you have determined the size of fuel tank you need for a diesel fire pump, what are the general requirements for installation?  Assuming that you are under under the International Building/Fire Codes, you would go through the following chain of code references:

  1. IFC (2009 edition) 3401.2 Nonapplicability. This chapter shall not apply to liquids as otherwise provided in other laws or regulations or chapters of this code, including: ... (3) Storage and use of fuel oil in tanks and containers connected to oil-burning equipment. Such storage and use shall be in accordance with Section 603. For abandonment of fuel oil tanks, this chapter applies.
  2. IFC (2009 edition) 603.1 Installation. The installation of nonportable fuel gas appliances and systems shall comply the International Fuel Gas Code. The installation of all other fuel-fired appliances, other than internal combustion engines, oil lamps and portable devices such as blow torches, melting pots and weed burners, shall comply with this section and the International Mechanical Code.
  3. IMC (2009 edition) I915.1 General. The installation of liquid-fueled stationary internal combustion engines and gas turbines, including exhaust, fuel storage and piping, shall meet the requirements of NFPA 37.

So Fuel tanks need to comply with the following standards at minimum:
  1. UL 142 - Containment Products for Flammable and Combustible Liquids, Fixed and Stationary Storage Tanks, Special-purpose Tanks
  2. NFPA 20 - Standard for the Installation of Stationary Pumps for Fire Protection
  3. NFPA 37 - Standard for the Installation and Use of Stationary Combustion Engines and Gas Turbines
You will note that NFPA 30 (Flammable and Combustible Liquids Code) is not included on the list.  NFPA 20 appendix section A.11.4.3 clarifies that the intent is to apply NFPA 37 as the tanks is part of the "internal combustion engine system".  The specific explanation from the appendix language of NFPA 20 (A.11.4.3) is as follows:

Research has identified nothing in NFPA 30, Flammable and Combustible Liquids Code, or NFPA 37, Standard for the Installation and Use of Stationary Combustion Engines and Gas Turbines, that prohibits the outlet connection to the engine from the diesel tank from being in the location required by NFPA 20.
The applicable code is NFPA37, not NFPA30. The scope of NFPA 30 clearly states that if the installation meets the criteria in NFPA 37, then it satisfies the requirements of NFPA 30.
Therefore, NFPA 37 applies for the fuel tank for the fire pump, as it is considered to be part of the installation of the internal combustion engine. Subsection 6.3.2 of NFPA 37 deals with fuel tanks inside structures for fuels other than Class I liquids. Sections 6.6, 6.7, and 6.8 of NFPA 37 deal with filling, venting, and connections between the engine and the fuel tank, and these sections send the reader back to NFPA 30 for the requirements. A review of the tank chapter in NFPA 30 for fixed tanks with capacity of 119 gallons or more finds no requirement stating that the connection to the engine has to be from the top of the tank, if the tank is on the floor on legs, or otherwise above ground.

There are numerous requirements for the construction of a diesel fuel tank. However as long as you are buying a listed fuel tank, they will be integrated into the design.  So make sure that your fuel tank bears a permanent nameplate or marking the standard it was built to. It is not our intent to discuss how to build a tank.  This article is intended to address field installation issues.  In our opinion, there are four key items to consider:
  1. Location
  2. Venting 
  3. Fill Line 
  4. Containment  

Location

For most of the continental United States, fuel tanks should not be located outside due to temperature.  Diesel is a mix of hydrocarbons, and the components have different freezing points. For Number 2 diesel, as the ambient temperatures drop toward 32°F, it begins to cloud, due to the paraffin in the fuel solidifying. As the temperatures drop below 32°F, the molecules combine into solids, large enough to be stopped by the filter. This is known as the gel point, and generally occurs about 15 degrees F below the cloud point. 
11.4.3* Fuel Tank Supply Location.
...
11.4.3.2 In zones where freezing temperatures [32°F (0°C)] are possible, the fuel supply tanks shall be located in the pump room.
...
A.11.4.5 The pour point and cloud point should be at least 10°F (5.6°C) below the lowest expected fuel temperature.
Appendix section A.11.4.5 of NFPA 20 (2010 edition) states "The pour point and cloud point should be at least 10°F (5.6°C) below the lowest expected fuel temperature."  So per code if the temperature at your project site is ever expected to drop below 42-degrees you should not install the tank outside.  In practice we would not recommend tanks outside areas where the temperature drops below 50-degrees.


Venting

Tanks need to be vented for two reasons.  First, a "normal" or atmospheric vent to allow air into the tank while being filled and emptied.  It also allows equalization of pressure due to normal atmospheric temperature and pressure changes.  Second, an "emergency" vent to help prevent the tank from becoming over-pressurized and rupturing if exposed to fire. For double wall tanks require a second set of normal and emergency vent lines.  Termination of these vents shall be:
  1. Terminated at least 5-feet from any building openings (NFPA 20 section 11.4.1.2.8.2) [Note this is more stringent that the 2-foot requirement of NFPA 37 section 6.7]
  2. Vented so that vapors will not be trapped by eaves or other obstructions  (NFPA 20 section 11.4.1.2.8.2)
A code section that is commonly enforced, but not technically applicable is NFPA 30 section 27.8.1 which which applies to Class I liquids.  Diesel fuel is typically a Class II liquid (Flash Point equal to or greater than 100°F, but less than 140°F).  The exact wording is provided for reference below.
27.8.1 Vent Piping for Aboveground Storage Tanks.
27.8.1.1 Where the outlets of vent pipes for tanks storing Class I liquids are adjacent to buildings or public ways, they shall be located so that vapors are released at a safe point outside of buildings and not less than 12 ft (3.6 m) above the adjacent ground level.
You will note that appendix figure A.11.4.4 from NFPA 20 has a diagram indicating a 10-foot minimum distance from the "screened weather vent" to the fill cap.  To the best of our knowledge, there is no specific code requirement for this distance since the appendix is for guidance only.



Sizing of these vents is the per the name-plate on the tanks.  For the normal venting, NFPA 20 (2010 edition) section 11.4.1.2.8 directs you back to ANSI/UL 142 with the additional guidance that the vent shall be at least as large as the fill connection, but not less than 1.25-inch nominal inside diameter.  UL 142 Table 8.2 has the same guidance of a 1.25-inch nominal pipe diameter for tanks under 2,500 gallons in volume.  In practice, most tanks have at least a 2-inch vent connection (2.067 I.D. for Sch-40) as they utilize a 2-inch fill line and cap.

For emergency venting, NFPA 37 is strangely silent. However UL142 section 8.1 states that the tank "... shall have provisions for both normal and emergency venting" and provides the minimum nominal pipe vent diameters based on the wetted surface area in feet.  The key catch is that UL142 is written to only contemplate a maximum nipple length of one foot, so if a longer nipple is attached to the tank (which it always is) it should be calculated.

Fairbanks offers a time saving option of a single combined normal/emergency vent line from the tank (see figure below) which is not prohibited by the codes and standards.  The emergency vent is terminated with a separate weighted emergency vent cap (Item 19), while the normal vent is terminated with a standard screened vent cap (Item 2).  Combining the vents saves labor in the field and penetrations in the owner's walls.

Fill Line

Obviously we need a way to fill the tank.  NFPA 20 does not provide much limitations on the arrangement.  However, we recommend that you check with your local AHJ as one can interpret the code differently. For example, some AHJ's enforce Chapter 34 of the International Fire Code (IFC). Chapter 34 is entitled "Flammable and Combustible Liquids" and if applied to this "above-ground storage tank" would require: An overfill prevention system that would automatically shut off the flow of fuel to the tank (3404.2.9.7.6,1,1.2); Automatic reduced flow rate (3404.2.9.7.6,2); Spill containers having a capacity of not less than 5-gallons at each fill connection (3404.2.9.7.8). 

It is our opinion that NFPA 20 is a more specific code, and therefore the requirements of NFPA 20 override those of the IFC. This is further clarified by IFC section 102.10 which states "Where there is a conflict between a general requirement and a specific requirement, the specific requirement shall be applicable."  This is similar the application of NFPA 30 as noted at beginning of this article.

Remember do not use galvanized or copper pipe for vent or fill connection pipes on diesel tanks.  The sulfur in the diesel fuel can dissolve the zinc in the galvanized plating.  This "sludge" can then clog the fuel pump or injectors over time.

Containment

Per NFPA 20 section 11.4.1.2.4, "Fuel tanks shall be enclosed with a wall, curb, or dike sufficient to hold the entire capacity of the tank".  However, most of the time a double-wall fuel tank with leak detection is acceptable.  This is further clarified by appendix section A.11.4.1.2.1 which states "Dikes are generally not necessary due to the requirement for double-wall tanks with monitoring."  Just don't forget to provide the leak detection for the the interstitial space between the shells of the diesel fuel storage tank.  This signal is to be annunciated by the fire pump controller.

This language also appears to comply with secondary containment requirements of the Environmental Protection Agency (EPA) through the Resource Conservation and Recovery Act (RCRA) contained in title 40 of the Code of Federal Regulations (CFR) part 264.  Diesel fuel is considered a hazardous waste per EPA as they contains heavy metals per Title 40 § 261.3(v) (Definition of hazardous waste).   Per Title 40 CFR 264.175, the worst case of the following conditions shall be contained 1) 150% of the volume of the largest container or 2) 10% of the aggregate volume of all containers.

NEC Classifications of Locations

Do we need to assign any special electrical classification (e.g. Class I, Div 1) due to the presence of diesel fuel?  No.  Generally, diesel has a flash point of 125°F or higher.  As such it is considered a "combustible" rather than flammable per NFPA 30 (Flammable and Combustible Liquids Code). That means it has a flash point above 100°F and, unless you have reason to believe it will be routinely stored or handled at or above its flash-point, it may be ignored as a potential cause for Classifying a location. Note: routinely doesn't necessarily mean commonly or regularly, but simply that it wouldn't be an unusual event. Occasionally, it may be in a blend of fuels that has flammable properties; so it is still a good idea to review the Material Safety Data Sheets (MSDS) for the fuel.

Thursday, April 25, 2013

Fire Pump Sensor Recall

Gem Sensor 3100 Recall Notice

Gem Sensor - Old 3100 model
Gem Sensor - Model 3300 (new)
On April 24, 2012 the Consumer Product Safety Commission (CPSC) issued a press release, CPSC #12‐156, for the voluntary recall of Gems 3100 Pressure Detectors/Transducers because the transducer can fail to accurately detect water pressure in a fire suppression sprinkler system. This could cause the sprinkler system to fail to activate and pump water to the sprinklers in the event of a fire. The failure associated with the Transducer is not a sudden loss of function but rather a slow degradation of performance over many hours of continuous use with constant water pressure. The use of the transducer in non‐water and/or fluctuating pressure applications has not shown the same potential problem.

The sensors are basically failing in a "high" pressure rating (e.g. will read 100 PSI higher than actual pressure).  So it is easy to spot, but does require good on-going maintenance.  One should install a calibrated gauge and compare the pressures.

The transducer has "Gems Sensors & Controls," as well as the 18- digit part number, printed on a label affixed to the center of the transducer. Part numbers beginning with "3100" are included in this recall.

Gems sold the recalled 3100 Pressure Transducers directly to end-users and through distributors from January 2006 through February 2012.

The 3100 has been replaced with the new 3300 series model.  Replacement transducers are avaliable at no cost from Gem.

The newer 3300 model has a green sticker as shown in the figure to the right.  The older 3100 model has a white sticker.



_________________________________________________________________________________

NEWS from CPSC

U.S. Consumer Product Safety Commission

Office of CommunicationsWashington, D.C.


FOR IMMEDIATE RELEASE
April 24, 2012
Release #12-156
Firm's Recall Hotline: (855) 877-9666
CPSC Recall Hotline: (800) 638-2772
CPSC Media Contact: (301) 504-7908

Gems Sensors Recalls Pressure Transducers Used in Fire Pump Controllers Due to Risk of Failure in a Fire

WASHINGTON, D.C. - The U.S. Consumer Product Safety Commission, in cooperation with the firm named below, today announced a voluntary recall of the following consumer product. Consumers should stop using recalled products immediately unless otherwise instructed. It is illegal to resell or attempt to resell a recalled consumer product.

Name of Product: Gems 3100 Pressure Detectors/Transducers

Units: About 25,000

Importer: Gems Sensors Inc., of Plainville, Conn.

Hazard: The transducer can fail to accurately detect water pressure in a fire suppression sprinkler system. This could cause the sprinkler system to fail to activate and pump water to the sprinklers in the event of a fire.

Incidents/Injuries: None.

Description: The Gems 3100 Pressure Transducer is used to detect pressure in a range of applications, including the detection of water pressure as part of a fire pump controller in a fire suppression sprinkler system. The transducer has "Gems Sensors & Controls," as well as the 18- digit part number, printed on a label affixed to the center of the transducer. Part numbers beginning with "3100" are included in this recall.
Sold by: Gems sold the recalled 3100 Pressure Transducers directly to end-users and through distributors from January 2006 through February 2012 for about $250.

Manufactured in: England

Remedy: Contact Gems to receive enhanced twice monthly inspection instructions and information about a free replacement transducer, when warranted. End-users who use the 3100 Pressure Transducer in other applications in which water pressure is measured should contact Gems to determine if their units are affected.

Consumer Contact: For additional information, call the company toll-free at (855) 877-9666, between 8 a.m. and 4:30 p.m. ET, Monday through Friday, or visit the firm's website at http://www.gemssensors.com

Gems 3100 Pressure Transducer

Gem Sensor - Old 3100 model

---
The U.S. Consumer Product Safety Commission (CPSC) is still interested in receiving incident or injury reports that are either directly related to this product recall or involve a different hazard with the same product. Please tell us about your experience with the product on SaferProducts.gov

CPSC is charged with protecting the public from unreasonable risks of injury or death associated with the use of the thousands of consumer products under the agency's jurisdiction. Deaths, injuries, and property damage from consumer product incidents cost the nation more than $900 billion annually. CPSC is committed to protecting consumers and families from products that pose a fire, electrical, chemical, or mechanical hazard. CPSC's work to ensure the safety of consumer products - such as toys, cribs, power tools, cigarette lighters, and household chemicals - contributed to a decline in the rate of deaths and injuries associated with consumer products over the past 30 years.


Under federal law, it is illegal to attempt to sell or resell this or any other recalled product.

Thursday, March 15, 2012

Pressure Relief Valves with Diesel Engines



Photo of Circulation Relief Valve
Circulation Relief Valve
When is a pressure relief valve (PRV) required on a fire pump system?  For a standard 175 PSI rated system, the simple answer is check and make sure that your expected churn pressure plus maximum static suction pressure will not exceed 144.6 PSI (or 206.6 PSI for a 250 PSI rated system).  The sizing of the relief valve comes from NFPA 20 (2010 edition) table 5.25(a) which is summarized in our fire pump sizing app.  For those of you that like to know the details read on.

First let's clarify that we are taking about a main pressure relief valve and not a circulation relief valve.  A circulation relief valve is generally 3/4-inch in size if less than 3,000 gpm and intended to provide a little fresh water into the pump casing for cooling purposes.

photo of main pressure relief valve for fire pumps
Pressure Relief Valve
When we say pressure relief valve in "fire pump" terminology, we are referencing a PRV that is only provided on diesel fire pumps to accommodate possible engine over-speed conditions.  The regulators on diesel engines are good, but not perfect.  When the load on the diesel engine changes,there is a natural delay in response and overshoot while the engine tries to maintain speed.  Our goal is prevent the system from exceeding maximum rated system-pressures when this slight change in RPM occurs.  By code diesel fire pumps have a kill switch should the RPM exceed ten-percent of the design speed.  In practice, we have rarely seen a well maintained engine exceed 1.5% of the required speed when adjusting for loads.

So how does this 10% maximum permitted over-speed RPM relate to the output pressure?  The speed (RPM) of a fire pump and the pressure developed do not increase linearly.  That is if you double the RPM you do not double the pressure.  When you double the speed you actually get four times the pressure.  The formula is written as follows:

Pump Speed vs. Pressure Affinity Formula
Pump Speed vs. Pressure Affinity Formula - Rearranged

If we square the 10% increase in speed, we get a 21% increase in pressure as shown below.  If we take 144.6 psi * 121%, we get 175 PSI.  In practice, we do not recommend running your system this close to the rated system pressure unless you know there will never be any change to your suction pressure (i.e. a vertical turbine fire pump).  For diesel fire pumps we recommend that you call and talk to one of our sales engineers.
The NFPA 20 fire pump committee did this exact same exercise and came up with the following language for the code:
NFPA 20 – 2010 Edition
4.18.1* General.
4.18.1.1 Where a diesel engine fire pump is installed and where a total of 121 percent of the net rated shutoff (churn) pressure plus the maximum static suction pressure, adjusted for elevation, exceeds the pressure for which the system components are rated, a pressure relief valve shall be installed.

FM Global Standard 3-7 (Fire Protection Pumps – May 2010)
2.3.3 Pressure Relief Valves

2.3.3.4 Provided a main relief valve on all diesel engine-driven fire pumps when 121% of the net rated shutoff (churn) pressure plus the maximum pump static suction pressure exceeds any system component rated pressure.
FYI - Remember that utilizing a Pressure Relief Valve to reduce discharge pressures is not permitted by NFPA 20 section 4.7.7.2. Designing system to discharge large amounts of water every time it runs is not considered good design practice and code recognizes this fact.

Friday, February 17, 2012

Reliable Electrical Power for Fire Pumps and Backup Power

When do you need backup power for an electric fire pump?  The simple answer is when the power is "reliable".  Of course the word reliable means a lot of different things to different people.  Interestingly, NFPA 20 did not define reliable power until the 2007.  Thankfully the committee did agree on the following language:
NFPA 20-2010
A.9.3.2 A reliable power source possesses the following characteristics:
(1) The source power plant has not experienced any shutdowns longer than 4 continuous hours in the year prior to plan submittal. NFPA 25, Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems, requires special undertakings (i.e., fire watches) when a water-based fire protection system is taken out of service for longer than 4 hours. If the normal source power plant has been intentionally shut down for longer than 4 hours in the past, it is reasonable to require a backup source of power.
(2) No power outages have been experienced in the area of the protected facility caused by failures in the power grid that were not due to natural disasters or electric grid management failure. The standard does not require that the normal source of power is infallible. NFPA 20 does not intend to require a back-up source of power for every installation using an electric motor–driven fire pump. Should the normal source of power fail due to a natural disaster (hurricane) or due to a problem with electric grid management (regional blackout), the fire protection system could be supplied through the fire department connection. However, if the power grid is known to have had problems in the past (i.e., switch failures or animals shorting a substation), it is reasonable to require a back-up source of power.
(3) The normal source of power is not supplied by overhead conductors outside the protected facility. Fire departments responding to an incident at the protected facility will not operate aerial apparatus near live overhead power lines, without exception. A back-up source of power is required in case this scenario occurs and the normal source of power must be shut off. Additionally, many utility providers will remove power to the protected facility by physically cutting the overhead conductors. If the normal source of power is provided by overhead conductors, which will not be identified, the utility provider could mistakenly cut the overhead conductor supplying the fire pump.
(4) Only the disconnect switches and overcurrent protection devices permitted by 9.2.3 are installed in the normal source of power. Power disconnection and activated overcurrent protection should only occur in the fire pump controller. The provisions of 9.2.2 for the disconnect switch and overcurrent protection essentially require disconnection and overcurrent protection to occur in the fire pump controller. If unanticipated disconnect switches or overcurrent protection devices are installed in the normal source of power that do not meet the requirements of 9.2.2, the normal source of power must be considered not reliable and a back-up source of power is necessary.

Interestingly for those of you who are insured by FM Global, the requirements are actually less stringent.
FM 3-7 (May 2010)
2.7.1.2 Supplement unreliable power sources with a second, independent source of power, such as an emergency generator or alternate utility connection, or provide a diesel engine-driven pump.
A reliable power source has infrequent power disruptions from environmental or man-made conditions. An electric power source that has disruptions lasting longer than 8 hours three or more times in a 12-month period is considered unreliable. More frequent short-term outages would also be considered unreliable.
The backup power can be from either an emergency generator or from a separate power system (unlikely).  So don't forget to select or a transfer switch or else change to a diesel engine driven fire pump.


Thursday, January 26, 2012

Pump Rotation

For a horizontal split-case fire pump the rotation is defined by looking at the drive side of the pump unit. This means that if you were sitting on the motor and looking at the pump, a right-hand (clockwise) rotation has suction on the right and a left-hand (counter-clockwise) has the suction on the left. Make sure that you verify your orientation when looking at the pump.

LH Counter Clockwise    |     RH Clockwise

Also don't forget there are no UL/FM listed "left hand rotation" diesel engines available on the market.

Tuesday, January 10, 2012

Diesel Fuel Tank Size for Fire Pumps

Guidance for the sizing diesel fuel tanks is quite straight forward due to the prescriptive requirements of the code.  Just take your engine HP x 1.10 and the result in gallons is the minimum required diesel fuel storage tank size.  The exact code reference from NFPA 20 (2010 edition) is provided below:
11.4.2* Fuel Supply Tank and Capacity.
11.4.2.1* Fuel supply tank(s) shall have a capacity at least
equal to 1 gal per hp (5.07 L per kW), plus 5 percent volume
for expansion and 5 percent volume for sump.
A.11.4.2 The quantity 1 gal per hp (5.07 L per kW) is equivalent
to 1 pint per hp (0.634 L per kW) per hour for 8 hours.
Where prompt replenishment of fuel supply is unlikely, a reserve
supply should be provided along with facilities for transfer
to the main tanks.
How the committee arrived at these simplified guidelines is as follows.  First, lets look at the conditions for when we expect the fire pump to run:

  • Quarterly Refilling of the Fuel Tank (approx 12-weeks)
  • A weekly test run for 30 Minutes
  • A minimum run time of 2-hour (or 4-hours during a fire depending upon your needs)
Multiply this out and you get basically 8-hours of continuous run time depending upon your run time during a fire.  Take the NFPA 20 appendix guidance of 1 pint/hr/HP (0.125 gallons/hr/HP) x 8 hours and you get 1 Gallon per horse-power.

Lets compare this to the actual published data for a specific diesel engine.  Take the smallest diesel engine Cummins makes a CFP5E-F10 which produces 95HP at 1760 RPM.  The published fuel rate is 4.9 Gal/hr (18.5 L/hr).  4.9 Gallons/hr x 8 hours x 1.10 (sump/expansion) = 43 gallons minimum.  If we use NFPA 20 guidance we would get 95 HP x 1 Gal/HP x 1.10 = 104.5 gallons minimum.  As you can see the for this specific example NFPA 20 is much more conservative.

The other item you need to verify is that the fuel tank complies with UL 142  as required by NFPA 20 (2010 edition) paragraph 11.4.1.2.1.  Fuel tank sizes are limited to 1320 gallons and the standard sizes available are as follows:



Nominal Tank Sizes (Gallons) Usable Volume (Gallons)
119 105
187 165
300 270
359 320
572 515
849 766
1100 993