Patol Limited

Patol Digital Linear Heat Detecting Cable (LHDC) may be employed for the detection of fire conditions related to various risks on petro-chemical storage sites. The LHDC system has a proven record of being an indispensable aspect of the protection regimes that prevent catastrophic events as shown in the above photograph.

Digital LHDC is unique in that it can be readily installed in close proximity to risks where flammable gases may ignite and will tolerate these arduous chemical and environmental rigors as a normal condition.

Rapid  detection of anomalies permits early application of containment measures such as foam extinguishing.

Some of the prime features of the system are as follows:-

¨ Floating Roof Tank Rim Seal protection - Including Retractable Cables

 

¨ Fixed Roof Tank protection - Vents, Gauging Points, Inspection Covers.

 

¨ Monitoring of Pipes, Manifold Systems and Product Pumps .

 

¨ Alarm and Process Control Interfaces - Distance / Location Metering .

 

¨ Intrinsically Safe operation using certified Barriers / Isolators.

 

¨ UL Listed.
TANK FARM FIRE DETECTION

PATOL LINEAR HEAT DETECTING CABLE

LHDC FIRE SYSTEM PRODUCT GUIDE

PETRO-CHEMICAL BULK STORAGE FACILITY
Text Box: The Digital Linear Heat Detector comprises a twisted pair core cable. Each core is of passivated steel and has a special heat reactive polymer insulation. The cable has an overall protective sheath. The primary mechanism of heat (fire) detection is that the inner core insulating polymer is specially formulated such that it plasticizes at a specific temperature. The cable is constructed such that the twisted steel cores are in tension, and at the polymer trigger temperature the conductors connect. This provides an alarm signal to any associated monitoring device. The LHDC is employed in the Hazardous Area by means of an Intrinsically Safe (IS) Barrier, and is monitored for open circuit fault conditions by inclusion of an End Of Line (EOL) device. The LHDC has a fixed core resistance per metre. Thus the alarm point may be ‘located’ by appropriately calibrated control equipment such as the Patol LDM-519-DDL interface module. Patol LHDC is available with a number of alternative fixed operating temperatures, together with ruggedised types that have additional mechanical armouring such as stainless steel braid. Text Box: PASSIVATED STEEL CONDUCTORS

TEMPERATURE

REACTIVE

POLYMER

INSULATION

Fig.1
Text Box: Principles Text Box: The LHDC is sited to monitor all points where there is a potential for liquid/vapour leakage and consequent ignition. These risks include vents, gauging points, access covers and valve flanges. Patol produces a wide range of standard LHDC mounting brackets, support spacers and fixing clips. See page eight for references. Text Box: Petrochemical Storage Tanks Text Box: Floating Roof Rim Seals

The protection of storage tanks with floating roofs requires special consideration of the monitoring of the ‘Rim Seal’ between the floating roof (pontoon) and the tank wall.

Various mechanisms are employed as the primary seal which include:- Mechanical Shoe, Scissor, Liquid Mount Foam & Vapour Mount.

Often a secondary (or weather) seal is located above the primary seal. The photograph to the left shows the external (top) view of such a compression plate secondary seal.

This design provides an integral extinguishing foam ‘gutter’. Other configurations employ a ‘Foam Dam’ welded to the pontoon edge.

The LHDC is mounted above the rim seal at a location where it will most readily detect any leaked vapour ignition that may occur.

Figure 2 shows a typical arrangement where the LHDC monitors a secondary seal of similar nature to that of the above photograph.

In this case the mounting brackets are fixed to the edge of the roof  pontoon and extend out to cover the secondary seal’s ‘motion point’ with the tank’s shell wall.

Various mechanisms are available for fixing the LHDC to brackets. See standard fixings for examples.

Figure 3 shows an installation arrangement where the LHDC is mounted via brackets to the shoe of a primary “scissors / pantograph’ seal.

There is a considerable variety of mechanical arrangements of rim seals. Each must be separately examined and the most practical mounting method determined.

In many cases fixings from Patol’s standard range may be utilised.

Some rim seal arrangements will require ‘special’ brackets to correctly locate the LHDC. Patol can both design and fabricate mountings on provision of rim seal mechanical data.

Petro-chemical Product Pumps

LHDC Terminator / EOL

Junction Box

Two Core Fire Proof Cable

To Safe Area

Patol Digital LHDC

Fig.8

Motor

Detector Cable Support Framework

Pump

Faults related to petro-chemical product pumps can in many cases cause a fire. Generally the failure of the pump motor or coupling causes a seal failure resulting in product leakage together with its associated fire potential.

The LHDC is secured to a support framework which is mounted directly above the pump bearing / seal area. This arrangement provides good coverage and early detection whilst  giving sufficient clearance to enable easy access for pump maintenance work.

A number of pumps may be monitored as a single zone as shown in figure 8 above.

Fig.9