Linear Heat Detection (LHD) (also known as Linear Detection Wire or Linear Heat Detection Cable or Linear Heat) is a very commonly used method of fire detection. It can detect a fire anywhere along the length of the cable, and can be of lengths in excess of a kilometer.
Linear Heat Detection (LHD) is a line-type form of fixed temperature heat detection used in common commercial and industrial environments. This linear cable can detect a fire anywhere along its entire length and is available in multiple temperatures.
Linear Heat Detection (LHD) cable is essentially a two-core cable terminated by an end-of-line resistor (resistance varies with application). The two cores are separated by a polymer plastic, that is designed to melt at a specific temperature (commonly 68 °C for building applications), and without which causes the two cores to short. This can be seen as a change in resistance in the wire.
Linear Heat Detection Cable

Digital linear heat detection (LHD) cable is a combination of advanced polymer and digital technologies that can detect heat anywhere along its entire length. LHD cable is also compatible with any listed addressable or conventional panel. For addressable panels use addressable contact monitor modules. At the core of SafeCable is a twisted pair of extremely low resistance trimetallic conductors, sheathed in new advanced thermal polymers. These polymers are chemically engineered to break down at specific fixed temperatures allowing the twisted conductors to make contact and initiate an alarm at the control panel without any calibration for changes in the ambient temperature. The distance locating module (DLM-Z2) has One or Two Zones, which can be cross-zoned, built-in. It also allows you to identify and display the location, in feet or meters from the panel, where heat was detected.

There are limited states the LHD cable can be in:
1. Open-circuit – Effectively an infinite resistance
2. Normal Operating Condition – Apparent resistance will be the same as the end-of-line resistor
3. Fire Detection – Resistance of the Linear Heat Cable to the short circuit

The linear heat detectors shall sense an overheat condition at any point along its length and pinpoint its location. The heat detection system shall comprise a heat sensing cable and a monitoring /control unit.
A change in temperature along the sensing cable shall cause a relative change in resistance of the cable. This change shall be detected by the monitoring /control unit which shall signal an alarm at the preset temperature.

The sensing cable may be multicore l. One end shall be connected to the monitoring unit. The other end shall be terminated so as to create a loop which shall be continuously monitored for open and short circuit fault, and alarm condition.
Selection Criteria for Linear Heat Detector.

Following are some minimum requirement applicable for linear heat detector, however requirements vary from industry to industry.
The outer jacket shall be made of material that resists corrosion, chemicals, moisture etc.

The linear heat detector cable and monitoring system shall be suitable for operation on a nominal 24V DC supply.
The alarm condition shall be latched at the control unit, with reset facility from the Fire and Gas panel, and locally on the control unit.
The unit shall provide outputs for fault and alarm conditions that are compatible with the main Fire and Gas panel.
Sensing cable and any termination units required shall be certified for use as part of an IS circuit when installed in hazardous area.
Sensing cable and any termination units required shall be certified for use as part of an IS circuit when installed in hazardous area.

Benefits of liner heat detection
There are many benefits to LHD. One of which is a continuous source of heat detection up to 10,000 feet. LHD cables are also very durable and long-lasting. Conversely, spot heat detectors do not offer the continuous field of detection of LHD cables, they don’t hold up very well, and can be easily damaged.

Fike, one of the many manufacturers of linear heat detectors, notes many benefits of LHD. Some of these benefits pertaining to their detector called Protectowire include:

Fewer false alarms and false suppressant discharge with Confirmed Temperature Intiation (CTI).
Detection device works with fire alarm system interface and modules that identify source and temperature of hazard
Easy installation and maintenance
Provides hazard coverage at every point on the cable for maximum protection
Available in a variety of lengths, cable coatings and alarm temperatures for maximum flexibility
Wide zone area, up to 10,000 feet of continuous detection
Common applications

LHD is ideal for areas where electronics may not be the best choice. These devices are particularly appropriate for areas where installation or maintenance access is in a physically demanding or hazardous area. LHD is also perfect for when fire detection is required in close proximity. For example, in closed-in areas where it’s easier to run a cable than place a thermostat.

Some of the most applications for LHD include:
APPLICATION
Freezers
Printing presses
Vehicle suppression systems
Warehouses
Oil and Gas
Coal Storage
High Temperature Vessels
Fuel Storage
Conveyor System
Cable Tray
Tunnels
High Speed Train
Transformers
Production machine
Critical facilities, etc.
Installation, testing, and maintenance

LHD cables should be installed by a licensed fire protection professional. Linear heat detectors are easy to maintain and require little to maintenance making them the perfect heat detection solution for many building owners.

There are many guidelines and parameters as set by NFPA regarding the installation, testing, and overall maintenance of LHD devices. A licensed professional will follow this protocol for installation which include testing the continuity of the linear heat detector with an ohm meter to ensure it is in proper working order.

Fire Systems Inc. has experienced fire protection technicians who are specifically trained in Linear Heat Detection. We will ensure the proper installation of your linear heat detector and keep you on track with scheduled testing and maintenance. Contact us today to find out if LHD is the best choice for your facility. Visit our website or call us at 770-333-7979 for more information.

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Fuel Storage Temperature Monitoring System

Petroleum storage tanks and cryogenic product storage facilities (liquid natural gas, LPG, ethylene, ammonia, etc.) require sensitive temperature monitoring systems to give ample warning of elevated temperatures prior to combustion. By providing an advanced notice of rising temperatures, appropriate steps can be taken to prevent a disaster from happening. Senkox TDS-FS Temperature Monitoring System is the ideal solution to fill this role. The TDS-FS system is composed of multiple Senkox HSD Linear Hot Spot Detectors and accessories; the HSD Linear Hot Spot Detector includes HSD linear heat sensors and DAQ modules.

The flexibility of the Senkox HSD Linear Heat Sensor cables, allows it to be mounted around the tank. The system provides real-time temperature monitoring and also detects the precise location of hot spots. As a result, safety personnel have real-time data of the thermal conditions of the storage tanks. This feature provides advanced warning and extra time for working personnel to deal with cases of overheating. It also clearly identifies the hot spot location.

Floating roof tanks are vulnerable to elevated temperatures due to the highly abrasive environment and presence of flammable gases. HSD Linear Hot Spot Detectors are most likely to occur near the secondary seal of a floating roof tank, as these are the areas that suffer most from high abrasion and the presence of flammable gases. The HSD sensors are installed along the secondary seal of the floating roof tank to provide real-time data regarding temperature changes.

Spherical storage tanks are commonly located in areas of high fire risk. HSD sensors are installed on the surface of the sphere, allowing continuous temperature monitoring. Detection of any hot spots will trigger location specific sprinkler systems.

Technical Advantages
Sensors are intrinsically safe, and can be installed in hazardous locations.
Continuous and flexible linear sensor provides superior coverage in tight spaces.
Continuous temperature monitoring and rapid response to changes in temperature.
Sensors are able to withstand high temperature and can be reused repeatedly.
Simple system layout with easy installation, low maintenance.
Detects the hot spot temperature in real-time.
Details the position and size of any hot spot.
Provides rate of temperature change (ROTC).


Specification
Sensor HSD Linear heat sensor
Sensor Type TLA, TLB, TLF, TPLA
Working Temperature -40 to 260 degrees C (Sensor)
Environmental
(Control Panel) Operating temperature range: -20 to 70 degrees C Relative humidity: 0 to 95%, non-condensing
Protection Degree Sensor: IP68; Control Panel: IP65.
Sensor Channels Up to 24
Communication Interface RS 485 Port, Modbus/RTU Protocol
Power Supply 12 to 35V DC, 10W max
Hazardous Location Sensor: Class I, Division 1
Control Panel: Class I, Division 2

Strictly international standards deployment

Senkox HSD™ Linear Hot Spot Detectors

Senkox HSD™ Linear Hot Spot Detectors are advanced multi-functional detectors that provide early detection of fire or conditions of overheating to protected areas or equipment.

Senkox HSD™ Linear Hot Spot Detectors can detect the real-time temperature, position and size of hot spots along the Senkox HSD™ Linear Heat Sensor cable. They can also provide the rate of temperature increase, and the temperature difference between hot spots and the ambient temperature. The detectors have various types of output interfaces, such as relay outputs, analog output (4~20 mA or 0~5V), and serial communication port (RS485 or RS232, Modbus/RTU protocol).

The detector consists of two major components: An HSD™ Linear Heat Sensor cable and an HSD™ DAQ Module.

System Features
Innovative HSD™ Linear Hot Spot Detection technology provides early detection of overheating
Linear sensing technology provides line coverage with superior sensitivity.
Real-time temperature measurement of temperatures ranging from -40°C to 600°C.
Detect early overheating temperature from -40°C to 80°C.
Rapid heat response time.
Rate of temperature change (ROTC) detection.

Enhanced alarm feature
Pre-alarm and alarm set point are software adjustable from -40°C to 600°C.
Full supervision for trouble alarms, include short and open circuit.
Rate of temperature change (ROTC) alarm.

Rugged and re-usable Linear Heat Sensor
Innovation sensor materials and process provide stable function and uniform sensitivity.
Sensors withstand high abrasion, high temperature and high pressure.
No damage to sensors after alarm, re-usable.

Enhanced, comprehensive hot spot detection solution
Real-time hot spot temperatures.
Hot spot position(s).
Hot spot size(s).
Rate of temperature change.
Temperature difference between hot spot and ambient temperature.

Easy installation and maintenance
Intrinsically safe.
Simple system layout, plug and play installation.
Modular system structure, easy to maintenance and replace.
Can be used as field alarm system.
Can be connected to user existing DCS or monitoring system.

System Structure
The Senkox HSD™ Linear Heat Sensor continuously detects hot spots along the sensor cable. The hot spot signals generated from the Senkox HSD™ Linear Heat Sensor cables are acquired and processed by the DAQ Module. The processed data is output through the analog output channels (4-20 mA or 0-5V) or the serial communication port (RS485 or RS232, Modbus/RTU protocol) to the user DCS system or fire alarm system.

Cable Tray Temperature Monitoring

Power plants and industrial buildings often have miles of cable trays that carry power, data, and communication cables. Accumulation of heat from overloading, short circuiting, and aging cable often presents a fire hazard that can ultimately lead to lengthy downtime and even a large monetary loss.

Cable trays are often stacked underground, above the ceiling, or through the walls. As a result, the trays often take tight turns and are frequently placed in contorted positions. Over time old trays need to be removed and new trays added. Therefore, any temperature monitoring system associated with the trays must be durable and flexible to accommodate these conditions.

Senkox HSD™ Linear Hot Spot Detectors provide an ideal solution for the temperature monitoring of cable trays.

The Senkox HSD™ Linear Heat Sensors are installed on top of power cables in the cable tray. HSD sensors are mounted in a sinusoidal wave configuration along the tray to maximize coverage. The HSD sensors can then detect the real-time temperature, location and size of any emerging hot spots.


Technical Advantages
Intrinsically safe sensors, can be installed in the hazardous location.
Continuous linear sensor provides superior coverage.
Sensors withstand high temperature, can be restored after alarm.
Rugged Sensors, resistance to bending.
Sensors are easy installation and replacement.
Simply system layout.
Detect the real-time temperature of the hot spot.
Detect the position, size of the hot spot.

The FyreLine Analogue Heat Detector
The FyreLine Analogue Heat Detector is a rugged, easy-to-install detection system, consisting of a control module and detection cable, that is designed to interface with a standard fire alarm panel or addressable monitor module.

Heat sensing cables are capable of detecting heat anywhere along their length and designed for use in a vast range of applications and environments from tunnels, cable trays, racking to sensing changes in temperature within escalators and other applications where many risks of fire are hidden from view. Linear heat detection is highly cost-effective and can be easily installed with, or in place of, conventional heat detectors where traditional style detection may be difficult to install or maintain or is too expensive.

FyreLine Analogue Heat Detectors automatically compensate for changes in ambient temperature to maintain the accuracy of the alarm temperature and offer up to 500 metres of continuous detection per control module. This flexibility makes FyreLine Analogue Heat detectors extremely flexible for use in a wide range of applications.

How Does Linear Heat Detection Work?
When the temperature around the cable reaches pre-alarm temperature the control module triggers a warning, giving the user time to investigate and take any necessary action. The control module will only trigger full alarm when the temperature reaches a specified alarm point.

After an alarm is triggered the system can simply be reset with little disruption. FyreLine Analogue Linear Heat Detection cable is ‘self-restorable’ so does not need to be replaced unless it has become severely damaged.

Fire Alarm System Integration
The analogue linear heat detection control module can be connected directly to a single zone of a conventional fire alarm control panel, or, easily interfaced to an addressable loop using an addressable zone/switch monitor.

Sensing Cable Construction
FyreLine Analogue Linear Heat Detection cable is constructed using a pair of copper conductors coated in a temperature sensitive polymer whose resistance changes as a function of temperature. A calibration resistance (white) and average ambient temperature sensor (red) core are twisted with the two original conductors. A foil shield, outer sheath and optional protective coating is extruded over the twisted cores.

Wiring Configurations
Conventional Fire Alarm Systems
FyreLine Analogue Linear Heat Detection Cable should be connected to a conventional fire alarm control panel via the initiating device circuit.

In the circumstance that the area to be protected is some distance away, leader cable may be used between the FyreLine control module and the fire alarm control panel.

Addressable Fire Alarm Systems
When using FyreLine Analogue Linear Heat Detection in conjunction with an addressable fire alarm system it should be connected onto the addressable loop using a switch or zone monitor. An external power supply is needed for the FyreLine control module.

BATTERY MONITORING SYSTEMS

Battery Storage Case Study

OVERVIEW
A Battery Energy Storage System (BESS) stores electric voltage energy inside of specially developed batteries. The energy is generated by solar panels, wind farms, and other green technologies. The stored energy can then be used later to power any
thing from residential homes to electric vehicles.

Battery Energy Storage Systems (BESSs) are a sub-set of Energy Storage Systems (ESSs). An ESS typically contains several primary components, including the battery/power, monitoring and control systems, and a power conversion system. The
development of ESSs has opened the doors to the integration of renewable energy. Solar and wind farms can use ESSs to store electric charge as well as optimize energy efficiency.

A fire outbreak in a BESS is far more extreme than the usual fire risk posed by batteries because of the size, complexity, energy, and density of the systems and the Lithium-ion (rechargeable) battery chemistry involved. These factors contribute to significant fire risks in battery farms, electric vehicles, electric vehicle charging stations, and more.

Possible fire hazards for battery storage include mechanical
abuse (crushed, punctured, submerged), thermal abuse (over-
heating) or electrical abuse (short-circuit, overcharge, rapid discharge). Aside from physical or electrical factors, overheating can also be triggered by external high temperature. The greatest concern for fire outbreak or even explosion is when overheating results in a process called thermal runaway. Thermal runaway is
a reaction within the battery causing internal temperature and pressure to rise at a quicker rate then can be dissipated.

During a short circuit inside the battery, flammable electrolyte gases will begin to discharge rapidly. Then the battery separator breaks down. From there, the battery undergoes a violent temperature rise which may lead to risk fire. Once one battery cell enters thermal runaway, it generates enough heat to cause adjacent battery cells to also enter thermal runaway. This produces a fire that repeatedly flares up as each battery separator ruptures in turn.

One of the most concerning issues surrounding a BESS fire is that it cannot be treated like a “normal” fire due to its burn characteristics and toxic byproduct. Should an outbreak occur, specific extinguishing interventions will be required to contain the fire. Thus, early-detection and prevention is best for this application.

APPROACH
In order to monitor the client's cabinets storing batteries, a linear heat monitoring system was needed. The most effective way to avoid fire outbreaks in BESSs is to detect the abnormal overheating, or hotspots, along the battery cells of BESSs.

Senkox HSD™ Linear Heat Sensors (LHS) is an ideal solution to continuously measure accurate temperature in real-time. The sensor is intrinsically safe because it neither creates nor stores energy, making it apt for battery cell monitoring. With proper fire detection and protection, battery storage explosions can be greatly minimized.

INSTALLATION

The Senkox HSD™ Linear Heat Sensors are installed on top of power cables in the cable tray. Should any unusual temperature increase occur, the user will know because Senkox
cable monitors the real-time temperature and rate-of-temperature-change (and some sensors also feature the detection of the hot spot’s location and size). The HSD sensors are mounted in a serpentine wave along the tray to maximize coverage.

Senkox HSD™ Linear Heat Sensor is able to be cut to fit the room’s layout, which is especially useful to avoid another tangled mess along the cable trays. For this case study, Senkox HSD™ Linear Heat Detection System was installed on 4 floors
with a DAQ on each floor.

Wireless Transmission: Each Senkox DAQ module can be easily integrated with any centralized control room, DCS/SCA- DA system or fire suppression system. The data from each module can be transmitted to other systems either serially or wirelessly. For this client’s project, wireless transmission was needed between the control room and the DAQ module.

Wireless Transmission

Control Room

Senkox DAQ
For wireless communication, a transmitter allows the DAQ module to transmit the data over 1 kilometer away. A receiver is placed to the control room in order to receive the wireless signal from the DAQ module. The receiver module can be connected to any control room system using an RS-485 to USB cable. A wireless transmission makes it effortlessly easy for the client to monitor the BESS cabinets from the control room.

CONCLUSION
Fire protection is of highest importance in BESSs due to the thermal runaway reaction that causes overheating to spread from battery to battery. Additionally, a fire outbreak among lithium-ion batteries is extremely difficult to extinguish once
the fire has begun. The Senkox HSD™ Linear Heat Sensor allows the client to monitor the four BESS cabinets for any hotspots in real time, and ensures that any rise in temperature will be addressed before overheating turns into an explosion.

The Senkox solution works to protect the cabinets from the ever prevalent dangers of thermal runaway, but more importantly, to keep the people near the BESS safe from fire.

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