General Monitors FL500 UV/IR Flame Detector

Overview

The General Monitors FL500 is a compact ultraviolet / infrared (UV/IR) flame detector from MSA for indoor and outdoor hazardous areas. It combines a UV phototube for fast response with an IR detector that watches for the flicker of a flame, and it raises an alarm only when both sensors see radiation in the correct combination and intensity. This dual confirmation gives quick detection of hydrocarbon fires with better immunity to arc welding, lightning, hot objects and other single-band radiation sources. A separate FL500-H2 model is optimised for hydrogen flames, and MSA notes that the two models are not interchangeable.

Seven Star LLC supplies the General Monitors FL500 to oil and gas, power and petrochemical customers in Oman and the GCC, with engineering support in Muscat. The detector is a practical choice for compressor shelters, pump skids, turbine enclosures, loading racks and chemical storage areas where a UV/IR detector with a stainless steel housing, a wide field of view and several output options fits both new projects and replacement of older flame detectors.

Detection Principle

The UV channel of the General Monitors FL500 responds to radiation between 185 and 260 nm, a band emitted strongly by flames but largely absent from sunlight at ground level. The IR channel is centred on 4.35 microns, the emission band of hot carbon dioxide produced by burning hydrocarbons. A flicker discrimination circuit in the IR path uses the natural modulation of a flame to activate the IR channel, which helps reject steady hot surfaces. If the detector sees only UV, for example from welding, or only IR, such as a large modulating hot object, no alarm is generated.

Signals from both detectors go to a microcomputer that runs the fire decision algorithm and drives the outputs: a 4-20 mA analog signal with distinct levels for ready, IR, UV, alarm low and alarm high, an immediate Alarm Low relay, a time-delayed Alarm High relay, RS-485 Modbus RTU and HART 7. Every two minutes the Continuous Optical Path Monitoring (COPM) self-check tests the optical path and the electronics, and reports a fault if the window is blocked or a circuit has failed.

Engineering Design of the General Monitors FL500

The General Monitors FL500 housing is 316 stainless steel with a powder coat finish, 114 mm in diameter and 140 mm long, and the detector weighs about 4.0 kg with its stainless steel mounting bracket. It is certified Ex db IIC T5 Gb and Ex tb IIIC T100 °C Db (II 2 G D) and rated IP66/IP67, with North American approval for Class I Division 1 Groups B, C, D (Group A for FM). Cable entry is 2 × 3/4 in NPT or 2 × M25, and wiring is simplified compared with earlier designs.

Three front LEDs show normal, fault and alarm status. DIP switches set the sensitivity (high, medium or low), the Alarm High time delay (2, 4, 8 or 10 seconds) and the relay modes (latching or non-latching, energised or de-energised). The detector runs on 20 to 36 V DC with a maximum of 3 W. MSA lists FM performance approval on seven fuels, compliance with EN54-10 under the Construction Products Regulation and suitability for SIL 3 applications, and the detector can be tested with the TL105 test lamp, which simulates the flicker of a fire.

Key Features

From the MSA data sheet and operating manual, the main features of the General Monitors FL500 are:

• UV/IR detection gives fast response with increased false alarm immunity for indoor and outdoor use.
• The field of view reaches up to 130 degrees, measured as a conical angle.
• n-heptane fires are detected at 90 ft (27 m) in 6 seconds, or at 60 ft (18 m) in under 3 seconds.
• The COPM self-check runs every two minutes to verify the optics and the electronics.
• 4-20 mA source or sink output, alarm and fault relays, Modbus RTU and HART 7 are standard on the base configuration.
• A 316 stainless steel housing with three status LEDs keeps the footprint small.
• FM performance approval covers heptane, hydrogen, methane, methanol, propane, ethane and butane.
• Field testing without an open flame is possible with the TL105 test lamp.

Industrial Applications

UV/IR flame detectors such as the General Monitors FL500 are used to protect gas compressor packages, turbine and generator enclosures, fuel and LPG loading facilities, pump rooms, tank farms, chemical process units and warehouses for flammable liquids. In Oman these hazards appear at upstream production stations, gas plants, power and desalination plants with gas turbines, and the refinery, petrochemical and storage terminals in Sohar, Duqm and Muscat. The wide operating range of -55 °C to +85 °C copes with the heat load of an outdoor skid in the Omani summer.

Seven Star LLC supplies the General Monitors FL500 as part of complete MSA fire and gas packages. For long-range or heavily contaminated areas where a multi-spectrum IR detector is preferred, the General Monitors FL5000 MSIR flame detector is an alternative, and gas detection on the same skid can use the General Monitors IR400 point IR gas detector or the MSA General Monitors S5000 gas monitor. We can help select the right General Monitors FL500 sensitivity and delay settings for your fire and gas cause and effect.

Technical Specifications

The General Monitors FL500 specifications below are taken from the MSA data sheet 1466-18-MC (06.2024) and the FL500 operating manual.

How to Order

To order the General Monitors FL500, send Seven Star LLC an RFQ with the model (FL500 or FL500-H2), output configuration, cable entry and quantity, and add TL105 test lamps if required. Our instrumentation division will confirm availability and lead time, and you can download the General Monitors FL500 data sheet and operating manual from this page. Seven Star LLC supplies MSA flame and gas detection products to operators and contractors in Oman and the GCC, with engineering support from Muscat.