Every six months or after a system actuation,
a system maintenance technician services the wet chemical extinguishing system that protects kitchen
appliances, hoods, and the exhaust ducts. The work is conducted in accordance with the
manufacturer’s service manuals. Some components and parts are routinely replaced, while others that might
cause impairment or failure of the system are also replaced at that time. Knowledge of system
parts/components and their
purpose is essential in order to ensure the system will function as intended. Here is a description of some
of those essential components and parts along with things to keep in mind while performing the semi-annual
maintenance
of restaurant systems.
NFPA requires that all discharge nozzles be
provided with caps or other suitable devices [17A: 4.3.2.1]. As part of the 6-month maintenance service,
these components need to be examined. Missing or loose caps and damaged foil seals need to be replaced.
Additionally, silicone grease should be applied to caps every 6 months. Here are the most common types of
nozzle protection devices in use today.
Rubber Blow-Off Caps
A rubber blow-off cap keeps the orifice of a
nozzle free of grease and contaminants, which can interfere with proper agent distribution. An integral part of
the blow-off cap is the retaining strap, which attaches to the nozzle. The strap keeps
the cap attached to the nozzle after system discharge.
Metal Blow-Off Caps
Metal blow-off caps are sometimes used as
substitutes for rubber blow-off caps. A metal blow-off cap is attached to the nozzle with the integral stainless
steel wire. The wire keeps the cap attached to the nozzle during discharge and prevents
it from falling into or onto an appliance.
Nozzle Caps and Seals
For some system nozzles, a cap and foil seal is
used to keep grease and contaminants from accumulating in the nozzle orifice. The foil seal ruptures when agent
discharge occurs and must be replaced before the system is put back into service.
The foil is held in place by the nozzle cap.
Blow-off Cap Grease
Dow Corning® Silicone Grease No. 111 (P/N SL111) is the recommended grease for both rubber and
metal blow-off caps. Grease is applied at the 6-month maintenance interval.NFPA allows penetrations in
hoods to be sealed
by devices that are listed for such use [96: 5.1.5]. Also, any penetrations that result from the removal
of conduit or piping are required to be sealed with liquid-tight sealing devices [96: 10.2.7.2].
NFPA allows penetrations in hoods to be sealed
by devices that are listed for such use [96: 5.1.5]. Also, any penetrations that result from the removal of
conduit or piping are required to be sealed with liquid-tight sealing devices [96: 10.2.7.2].
“Grease-Tite” Adaptors
Jiffy “Grease-Tite” adaptors are UL listed
mechanical fittings that form a liquid-tight seal around distribution piping or detection cable conduit. These
adapters are installed wherever there is a need to penetrate a restaurant hood
or duct.
Corner Pulley “Grease-Tite” Adaptors
These Jiffy adaptors’ intended use are with
a high-temperature corner pulley. Adaptors create liquid-tight seals around 1/2 inch EMT conduit. Typically,
these adaptors are needed where a corner pulley is needed to make the 90° change
in direction from a detector bracket through the top of a hood.
Seals for Holes in Hoods
Whenever pipe or conduit is removed from a hood,
the remaining hole in the hood must be plugged and form a grease-tight seal. UL listed Jiffy Patch
“Grease-Tite” Seals are installed to cover un-wanted holes without welding.
Restaurant systems are mechanical, and
stainless steel cable is used for actuation of the system, including connections to fusible links and pull
stations. Cable is also used to trip mechanical gas valves. To work properly, and with little friction,
pulleys with ball bearing rollers are installed to provide a 90° change in direction. Here are some of the
most common pulleys used in the industry.
High-Temperature Corner Pulleys
There are two types of high-temperature corner
pulley elbows that are installed, whenever a 90° change in direction of conduit is needed within a hood. P/N
CP8 has socket connections and set screws for connecting to 1/2 inch conduit.
P/N CP5 has compression fittings for connecting to 1/2 inch conduit.
Corner Pulleys with Swing-Covers
All swing-cover corner pulleys are intended
for low temperature installations (outside restaurant hoods). P/N CP6 has socket connections and set screws.
P/N CP7 has 1/2 inch threaded (NPT) connections.
Tee Pulleys
Tee pulleys are installed where two cables from a
mechanical release module each need to make a 90° change in direction. Typically the application is a cable for
mechanical gas valve shutdown and cable for connection to a pull station. Tee
pulleys are never installed for detection cable applications.
Stainless Steel Cable
FireTech™ aircraft type (7x7) stainless steel cable is used for all restaurant system applications,
including connections to fusible links, pull stations, and mechanical gas valve trips. Make sure to have
an adequate
supply of metal crimps and S-hooks for connections to the stainless steel cable. The tools to use with
stainless steel cable are P/N CC093 cable cutters and P/N ST116 crimping tool.
Upon activation of any restaurant system, NFPA
requires that the fuel and electrical power that produces heat to the appliances, requiring protection, be
shut off [96: 10.4.1]. Shutoff devices require a manual reset [96: 10.4.4].
Mechanical Gas Valves
Upon actuation of a restaurant system, the
mechanical gas valve automatically shuts off. The most common type of gas valve is the Trip-to-Close
ASCO™ mechanical gas valve (P/N GVB). These valves are available to connect from 3/4 to
3 inch pipes.
Electrical Gas Valves
ASCO™ electrical gas valves (P/N GVC)
are the industry standard and come in sizes 3/4 to 3 inch. They are normally closed without power, so the
valve is held open when the solenoid is energized. Valves must be installed so the
solenoid is vertical and upright.
Manual Reset Relays
A manual reset relay (P/N SRR) is a safety
feature and is required where an electrical gas valve is employed. When an electrical gas valve closes, due
to system actuation or a power outage, the valve cannot be opened until the reset
relay button is pressed.
Micro-Switches
There are many electrical devices that must
either be turned off or turned on when a restaurant system actuates. These devices include, but are not
limited to, building fire alarms, electrical gas valves, contactors, lights, and
electrical power shutoffs. P/N MIC1 is a single-pole, double-throw and P/N MIC2 is double-pole, double
throw. Other switches specific to system manufacturer are also available.
NFPA requires the wet chemical that is used in
the system to be listed for the particular system [17A: 4.6.1]. After any discharge, the piping must be
flushed and blown out with dry air or nitrogen [17A: 7.4.3]. The supply of wet chemical for recharging the
system needs to be stored in the original closed shipping container [17A: 7.4.4].
Wet Chemical Recharge Agent
Wet chemical extinguishing agent is a solution of
water and potassium acetate, potassium carbonate, potassium citrate, or a combination of these chemicals. When
the extinguishing agent is discharged onto a cooking appliance fire, soap-type
foam is created on the surface of a cooking oil fire (excluding air), extinguishing the fire. Wet chemical
recharge agent must match the system manufacturer.
Servicing wet chemical extinguishing systems every
6 months helps ensure the system will work as designed. Your knowledge of how system parts play a role in system
operation is critical. Also routinely placing parts, according to the manuals,
and replacing potential problematic components and parts is essential to keep the system operational. The system
owner can rest assured that your knowledge and compliance with the national standards and the manufacturers’
service manuals
will ensure safety and maximizes the ability of the system to extinguish a fire, should one ever occur.
Mark Conroy is an engineer in
our Boston office and a member of the NFPA Technical Committee on Venting Systems for Cooking Appliances.