VQ600 Series Combustible Gas Sensing Head FEATURES Designed for fixed gas detection systems Diffused gas sampling Accessories available Rugged construction LEL and % volume monitoring Three thread options available ATEX certified II 2G Ex d IIC T5 Gb (T = -20 to +60 C) a CSA certified - File 107498 DESCRIPTION The VQ600 Series is designed to detect and monitor various Although SGX Sensortech generally recommends that gases in the range 0 to 100% LEL for combustible gases pellistors should be run with a constant voltage supply to the and 0 to 100% volume in thermal conductivity mode when bridge, it is possible to use a constant current supply using the SGX Sensortech range of pellistor gas sensors. provided that the voltage across the bridge in clean air The VQ600 Series is designed for use as an integral part of remains within the recommended limits. a fixed gas detection system. The head comprises a The head must be mounted so that the cable is protected. stainless steel flameproof enclosure constructed with an This is normally achieved by mounting it into a port in a integral stainless steel sinter which allows the safe entry of suitable junction box. the atmosphere being tested. It is essential that the head be efficiently earthed There are three types of mounting thread available to allow (grounded). This may be achieved by mounting it either into easy fixing to the junction box of the fixed system and the an earthed metal junction box, or into a non-metallic junction facility to attach accessories to the sensor via an external box fitted with an earth continuity plate used in accordance M46 thread. with the box manufacturer s instructions. There are no Other benefits of the VQ600 Series are: internal connections to the sensing head body. No moving parts. No serviceable parts. CERTIFICATIONS No adjustments required. The VQ600 Series is certified by SIRA Certification No assembly or dismantling. Services, EU Notified Body No. 0518. The VQ600 Series operates from 0 to 100% non- Certificate number BAS01ATEX2110X certifies it as condensing relative humidity and in a temperature range of flameproof equipment to EN60079-0:2006 (including 20 to +60 C. amendments A1 and A2) and EN60079-1:2007 subject to Note that there are no serviceable or adjustable parts the Instructions specific to hazardous area installations (see within the sensor assembly and any attempt to page 2). dismantle the assembly or access the sensor will The VQ600 Series is certified by CSA International for Class invalidate the sensor approvals and manufacturer s 1, Groups B, C and D hazardous locations for both Canada guarantee. and the USA. Certification for Canada is as products in Class 4818 03 to OPERATION the requirements of CSA Standards C22.2 No. 30-M1986 and C22.2 No. 142-M1987 and is covered by File No. The pellistor used in the head should be operated in the LR107498. manner recommended in the appropriate data sheet. In general it is recommended that the detector and compensator be run in a Wheatstone Bridge circuit so that a difference signal may be obtained. A suitable circuit is shown in Fig. 1 overleaf. In use, the bridge supply voltage should not be allowed to vary by more than the specified +0.1 V, or the output in clean air may change in sympathy. SGX Sensortech (IS) Ltd Registered in England No. 08067077 A1A-VQ600 Ser Version 12, September 2010 Instructions Instructions specific to hazardous area installations (reference ATEX Directive 94/9/EC, Annex II, 1.0.6). 1. The head is classified as flameproof equipment and is marked: BAS01ATEX2110X II 2G Ex d IIC T5 Gb T = 20 C to +60 C a 2 W/5 V MAX The head should only be used within the limits imposed by this certification and by these conditions of use. 2. The head may be used in a hazardous area without further mechanical protection. However, the cable requires mechanical protection and must be terminated R = R = 500 to 5000 , R R /5 1 3 2 1 in a suitable enclosure. R provides zero adjustment and may be omitted if not 2 required. 3. The head must be efficiently earthed (grounded). This may be achieved by mounting it into an appropriate Fig. 1: Recommended circuit diagram earthed metal junction box or into a non-metallic junction box fitted with an earth continuity plate used in HEALTH AND SAFETY HAZARDS accordance with the box manufacturer s instructions. There are no internal connections to the sensing head This device contains PTFE. If it is subjected to temperatures above 350 C, there is a danger from the release of toxic body. fumes and breakdown products. Do not dispose of by 4. In the event that the head becomes embedded in a incineration. junction box by over-tightening or corrosion, it may be released by the use of a spanner or wrench on the two flat surfaces on the sides of the body. TABLE 1 5. There are no user serviceable parts inside the body of Typical operating characteristics at room temperature when the sensing head, and no attempt should be made to fitted with SGXs most widely used pellistors. open the body for any purpose. The unit is non- repairable. Pellistor Bridge Zero offset Minimum voltage range (mV) sensitivity in 6. The head has not been assessed as a safety device (V) methane (mV/%) (EHSR 1.5). VQ1 2.0 -25 to +35 14 VQ3 2.5 -25 to +25 17 7. When installed in outdoor locations where rain or spray 2.0 +35 to +55 9 could interfere with the safe working of the head, or in VQ10 and indoor locations where water jets, sprays, or hoses are VQ10S used routinely for cleaning purposes, the head should be VQ21T (poison 2.0 -15 to +30 10 fitted with the Weather Cap that is available as an resistant) accessory. VQ24 and 3.5 0 to +50 21 VQ24S 8. The end-user/installer should be aware that the certification of the head relies in its construction on the For more detailed performance specifications for the use of the following materials, which are suitable for VQ600, please refer to the corresponding SGX Sensortech most common applications: data sheet for the pellistor sensor fitted. Enclosure Stainless Steel Sinter Stainless Steel Bushing Epoxy resin ACCESSORIES (All dimensions in millimetres) In accordance with the Note in EN60079-0:2006 Clause 6.1(a), the end-user/installer shall inform the Three accessories are available to complement the VQ600 manufacturer of any adverse conditions that the head Series gas detection head. These accessories are shown on may encounter. This is to ensure that the head is not page 3, with the VQ600 in place. subject to conditions that may cause degradation of these materials. SGX Sensortech (IS) Ltd Registered in England No. 08067077 A1A-VQ600 Ser Version 12, page 2