System Sensor FAAST Comprehensive - Manual (Page 30)

CApillArY TuBeS AnD SAmplinG poinTS
A capillary tube is a length of flexible tubing that is connected to the main
sampling pipe with a sampling point at the end. The purpose of these tubes
is to extend the placement of the area being sampled away from the main
pipe network. This may be necessary to reach into an enclosed space, such
as a cabinet, or for aesthetic and security reasons. This allows the core pipe
network to be hidden, while only a small sampling point is located in the
main space. Figure 5 shows the capillary tube extending down from the main
sampling pipe with a sampling point on the end. The sampling hole is located
in the sampling point. PipeIQ allows for capillary tubes and sampling points
to be added to the pipe network design and will calculate the appropriate air
flow through the system.
The maximum length for capillary flexible tubing is 26 ft. (8 m). When mul-
tiple capillary tubes are used in a network, the length of each capillary tube
should be approximately equal. A sampling hole is required at the end of each
capillary tube. PipeIQ will provide direction when designing capillary tubes
into the pipe network.
FiGure 5: CApillArY TuBeS WiTh SAmplinG poinTS
FiGure 6. TYpiCAl pipe mounTinG BrACKeTS
mounTinG BrACKeTS
The pipe network is mounted to the ceiling or other appropriate location us-
ing pipe mounting brackets. A large variety of brackets are available. Typical
brackets include clips, saddle clamps or tie wraps, as shown in Figure 6. The
mounting choice will depend upon the material being mounted to, environ-
mental conditions, as well as local codes and regulations. Mounting brackets
are usually centered 5 ft. (1.5 m) apart when using ¾ inch sch40 pipe at 70°F
(21°C). Open style mounting clips should not be used in an inverted position
with the open section facing downward such that the pipe could drop from
the clip.
lABelS
Labels are available to identify the pipe network as a fire detection system,
both at the sampling points and along the pipe itself. NFPA 72 states that the
pipe should be labeled:
1. At changes in direction or branches of piping
2. At each side of penetrations of walls, floors, or other barriers
3. At intervals on piping that provide visibility within the space, but no
greater than 20 ft. (6.1 m)
pipe neTWorK inSTAllATion
This section provides the basics to installing a pipe network. Keep in mind
that each system will have different characteristics, and will have variations
to accommodate. The most common issues are described in the following
sections.
Cutting pipe
Proper tools must be used when cutting pipe. Pipe shears or a wheel type
plastic tubing cutter can be used for PVC or CPVC pipe. Always keep the cut-
ting edge of the tools sharp. Ensure that cuts are made perpendicular to the
pipe length keeping the cuts square. Square cuts ensure maximum bonding
area and help provide a good seal when joining the components.
Remove all loose material and any burrs from the end of the pipe after a cut.
Debris and shavings from cuts must be removed in order to keep sampling
holes free of obstructions.
Joining Components
The pipe network must be permanently connected once the system has been
installed and tested. The method to accomplish a permanent connection de-
pends upon the material of the pipe and fittings.
NOTE: The immediate connections between the inlet pipe and exhaust pipe
and the FAAST detector SHOULD NOT be permanently connected.
When bonding components together, never place solvent on the inside of a
pipe or other component. Apply the solvent only to the outside of the pipe
that is being inserted into a coupling or other component. If solvent is ap-
plied to the inside of a pipe or other component, the solvent can build up.
This build-up can affect the air flow within the pipe network and may cause
abnormal behavior within the pipe network.
Make sure that pipes are inserted completely and butted against the lip of the
coupling or other component. If this is not done, turbulence can be created due to
the gaps, which can cause problems with system pressures and air flow.
mounting the pipe network
The following recommendations should be taken into consideration when
mounting the pipe network.
• Minimize flexing of the pipes by securing them at proper intervals with
appropriate mounting brackets.
Maximum support spacing
pipe DiAmeTer 60°F 100°F 140°F
½ in . (15mm) 4½ft . (1 .3m) 4ft . (1 .2m) 2½ft . (0 .7m)
¾ in . (20mm) 5ft . (1 .5m) 4ft . (1 .2m) 2½ft . (0 .7m)
• Typically, the pipe network should be mounted between one and four
inches (25 – 100 mm) below the ceiling, subject to local codes and
regulations.
• Allow for expansion and contraction of the pipe network in areas of ex-
treme temperature fluctuations, especially on long straight runs of pipe.
• In areas of extreme temperature fluctuations, never place mounting
brackets adjacent to couplings, unions or tees. This can lead to interfer-
ence with expansion or contraction of the pipe network.
• To minimize the effect of pressure differentials, the sampled air should
be returned to the protected environment wherever possible. This
eliminates any pressure differentials that might reduce the air flow in
the pipe network.
ASP-81
ASP-83
SS-400-007 31 E56-3621-003
The Pipe System