1、 STDOEEMUA PUB NO L55-fN6L 1788 E 57Lb73Y OOOO2LLi T30 THE ENGINEERING EQUIPMENT AND MATERIALS USERS ASSOCIATION STANDARD TEST METHOD FOR COMPARATIVE PERFORMANCE OF FLAMMABLE GAS DETECTORS AGAINST POISONING PUBLICATION No. 155 (1988) Copyright 0 1988 The Engineering Equipment and Materials Users Ass
2、ociation ISBN O 85931 059 3 14-15 BELGRAVE SQUARE LONDON SWIX 8PS Telephone O1 235 531617 EEMUA COPYRIGHT Engineering Equipment and Materials Users AssociationLicensed by Information Handling Services STD.EEMUA PUB NO 155-ENGL 1988 57bb734 0000215 977 m TH& ENQI“Q EQUIPbIENT AND MATEIALS USERS ASSOC
3、IATION. The Engineering Equipment and Materials Users Association -EWA - is an organisation of substantial purchasers and users of engineering products. EEMUA,members include leading representatives of both the private and public sectors, from the energy and process industries. EEMIJA is concerned w
4、ith the design, installation, operation and maintenance of the engineering plant used in members business operations. The Association aims to reduce members costs by providing the opportunity for them to share resources and expertise in influencing the environment within which their engineering acti
5、vities are carried out. EEMUA supports the British Standards Institution, works with other Institutions, Associations, Government departments, regulatory bodies and the Confederation of British Industry. EEMIJA is also actively involved with other standards making bodies, both national and internati
6、onal, such as the American Petroleum Institute. Work which is carried out in-house by members alone, or with the help of other organisations, may lead to the production of Association publications. These are prepared primarily for the use of members, but are sometimes offered for wider circulation.
7、Such publications may also be submitted to the British Standards Institution as the basis for a British Standard. (i) COPYRIGHT Engineering Equipment and Materials Users AssociationLicensed by Information Handling Services STD*EEMUA PUR NO L55-ENGL 1988 57bb73Li 000021b 803 = ABOUT THIS PUBLICATION.
8、 I In order to ensure that nothing in this publication can in any manner offend against, or be affected by the provisions of the 1 Restrictive Trade Practices Act 1976, the recommendations which it contains will not take effect until the day following the day on which its particulars are furnished t
9、o the Office of Fair Trading. Since the subject dealt with seems likely to be of wide interest, the publication is also being made available for sale to non-members of the Association. Any personwho encounters an inaccuracy or ambuiguity when making use of this publication is asked to notify EEMUA w
10、ithout delay so that the matter may be investigated and appropriate action taken. It has been assumed in the preparation of this publication that the user will ensure that the contents are relevant to the application selected and are correctly applied by appropriately qualified and experienced peopl
11、e for whose guidance it has been prepared. The Association does not, and indeed cannot, make any representation or give any warranty or guarantee in connection with material published in EEMUA publications and expressly disclaims any liability or responsibility for damage or loss resulting from thei
12、r use. Any recommendations contained herein are based on the most authoritative information available at the time of writing and on good engineering practice, but it is essential to take account of appropriate subsequent developments or legislation. All rights are reserved. No part of the publicatio
13、n may be reproduced, stored in as retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without prior permission of the copyright holder. A list of other EEMUA publications is given at the end of this publication. (iii) COPYRIGHT
14、Engineering Equipment and Materials Users AssociationLicensed by Information Handling Services1. FOREWORD. 2. RELEVANT STANDARDS. 3. OBJECTIVES . 4. TEST METHOD. 5. APPARATUS. 6. RESULTS. FIGURES. 1 2 Page Nos. 1. 3. 5. 7. 9. 11. Previous page is blank COPYRIGHT Engineering Equipment and Materials U
15、sers AssociationLicensed by Information Handling ServicesSTD-EEMUA PUB NO L55-ENGL 1988 m 1. FOREWORD. In the fast developing technology of pellistor manufacture, manufacturers have used many different methods of showing how their pellistor withstands the effects of poisoning by the many contaminant
16、s met with in industry today. Users have difficulty in making comparisons between the claims made by the different manufacturers for their products. The members of the EEMUA Instrument Committee decided that a standard test method to make such comparison was needed and this document is the result of
17、 that decision. It is hoped that the use of this method will assist users in deciding which pellistor best meets their requirements at the most reasonable cost while establishing a standard method of making comparisons. 1 COPYRIGHT Engineering Equipment and Materials Users AssociationLicensed by Inf
18、ormation Handling ServicesSTD-EEMUA PUB NO 155-ENGL 1988 57bb73Li 00002L9 5LZ 2. RELEVANT STANDARDS. British Standards. BS 4559 Methods for preparation of calibration gas mixtures. BS 6020 Instruments for the detection of combustible gases. international Stan-. IS0 6144 Gas analysis - Preparation of
19、 calibration gas mixtures - Static volumetric methods. IS0 6349 Gas analysis - Preparation of calibration gas mixtures - Permeation method. 3 Previous page is blank COPYRIGHT Engineering Equipment and Materials Users AssociationLicensed by Information Handling Services3. OBJECTIVES . The objective o
20、f this test is to provide a standardised procedure for assessment of the poison resistance of electrocatalytic combustible gas detectors. The test procedure is designed to quantify the change in sensitivity of such detectors as a result of exposure to certain substances which can cause poisoning of
21、the catalyst. It forms a supplement to existing test procedures (based for example on BS 6020), but provides results in the form of response curves with time rather than as a simpler go/no go decision. A simpler go/no go test may be appropriate in the future when the current rapid development of sen
22、sor poison resistance has ceased. All official comparative tests will be carried out to this method, by an independent Test House ( e.g. SIRA Ltd). However publication of the method is intended to enable other workers to duplicate their results if required. This test procedure is intended to be appl
23、ied to packaged detectors ( that is with the element mounted in a housing with sinter, as supplied for normal use). 5 Previous page is blank COPYRIGHT Engineering Equipment and Materials Users AssociationLicensed by Information Handling Services STD.EEHUA PUB NO 155-ENGL 1988 H 57bb73Li 0000221 170
24、H 4. TEST METHOD. The test method is to expose the sensor under test to specified poison concentrations in air, with regular sensitivity checking to monitor response degradation. The sensor should be powered, and adjusted and calibrated in accordance with the manufacturers recommendations. Sensivity
25、 checking should be carried out as follows:- (i) The sensor should be supplied with clean air ( that is air with no flammables or poisons present ) for two (2) minutes. (2) The sensor gas supply should then be switched to 50% LEL methane in air mixture for a further three (3) minutes. (3) The sensor
26、 supply is then switched to air doped with poison for a further fifty-five (55) minutes. This cycle of exposure to air, span gas and poison is then repeated hourly for a total of seventy-five (75) hours. The 75 test cycles must carried out consecutively, with no interruption to gas cycle or sensor p
27、ower. Three poisons may be used, namely hexamethyl disiloxane(HMDS), hydrogen disulphide (H2S), and tetraethyl lead (TEL). These poisons are intended to give a measure of sensor poison resistance in service where a range of poisons (such as these and others ) may be encountered. The poison concentra
28、tions to be employed are: H2S 100 ppm TEL 10 ppm (dispensed as a solution of 20% TEL 80% toluene by weight) . Only one poison should be used per test. 7 Previous page is blank COPYRIGHT Engineering Equipment and Materials Users AssociationLicensed by Information Handling ServicesSTD-EEMUA PUB NO 155
29、-ENGL 1988 H 57bb73q O000222 007 1 5. APPARATUS. 1 - The apparatus for the test consists of a gas supply, a poison dispenser and a manifold assembly for mounting the sensors. In addition sensor power supplies, signal conditioning, data collection and control instrumentation will be required. The sen
30、sors under test must be supplied with clean air, air doped with poison, and also with 50% LEL methane (2.5% v/v methane in air) for sensitivity checking. Each gas supply should provide gas at atmospheric pressure at a constant flow rate of nominally 200 ml per minute per sensor(normal1y 0.5 to 1.0 l
31、itre per minute for up to 5 sensors simultaneously). The recommended design for these gas supplies is to use pressurised gas bottles, pressure regulators, flow control valves and flow meters for each gas. These gas supplies feed a valve system which passes one or other gas stream to the subsequent a
32、pparatus. Other methods of providing the gas supply can be used provided the performance of the system, in terms of concentration, purity and flow rate is maintained. 5.2 Poison Dispenser. The poison dispenser will be fed with a constant flow-rate of gas from the appropriate gas supply, and is requi
33、red to add a constant dopant level of the chosen poison. Various methods of doing this exist, and are documented in BS 4559, and IS0 6154/6349. Two recommended methods are constant injection, and permeation tubes. Full details of these methods are given in the standards, however brief details are in
34、cluded here. Continuous injection is carried out using a motorised syringe, which injects at a predetermined rate into the gas stream. The rate of injection must be calculated on the basis of the known gas flow rate to give the required concentration in the final mixture. The syringe unit must be ma
35、intained at a constant temperature to ensure a constant rate of poison delivery. The injection takes place into a mixing vessel, to ensure that the resulting gas mixture is uniform. Syringes and drive units capable of functioning for 75 hours without replenishment are available. The use of permeatio
36、n tubes relies on the use of proprietary calibrated poison sources, which emit the poisoning species at a rate which is tabulated against temperature. The required rate of poison administration must be calculated on the basis of the known gas flow rate and the permeation tube temperature adjusted ac
37、cording to the instructions of the tube manufacturers. 9 Previous page is blank COPYRIGHT Engineering Equipment and Materials Users AssociationLicensed by Information Handling ServicesSTD-EEMUA PUB NO 155-ENGL 1988 M 57bb73q 0000223 T113 H S may be supplied from compressed gas cylinders, such as BOC
38、 Spectroseal , provided that the concentration is independently verified before use. 5.3 Manifold Assembly. The function of the manifold assembly is to channel the selected gas stream from the poison sensor to the sensors under test. Of prime importance are the requirements that the entire assembly
39、should be inert to the poison, so that processes such as adsorption or selective diffusion, which might change the poison concentration, are reduced to negligible levels. A recommended assembly employs a loop of PTFE tube, of 6 to 8 mm internal diameter and 1 meter in length, to conduct the selected
40、 gas stream from the poison dispenser to a sensor manifold. 5.4 Sensor Manifold. The sensor manifold comprises a shallow box, dimensions 250 x 100 x 15 mm, with short tubes for input and output at opposite ends, fabricated from type 316 stainless steel. Five holes of 25 mm diameter in the top face a
41、llow up to five sensors to be deployed in the gas stream using simple clamping devices and PTFE sealing washers. The exhaust stream must be vented to atmosphere in such a way as to avoid any backpressure and hazards to personnel. 5.5 instrumentation. Sensor power supplies must be used which drive th
42、e sensor according to the manufacturers recommendations. Generally these will be the manufacturers own unit, adjusted for sensor current, zero and span, and proividing analogue output for data acquisition purposes. 10 COPYRIGHT Engineering Equipment and Materials Users AssociationLicensed by Informa
43、tion Handling ServicesSTD-EEMUA PUB NO 155-ENGL 1988 57bb734 O000224 9BT D i 6. RESULTS. The results from the test will be, for each sensor and poison, graphs of percent sensitivity (referred to 100% at the start of the test ) and zero shift ( in percent LEL equivalent ) as a function of time throug
44、hout the test period. 11 COPYRIGHT Engineering Equipment and Materials Users AssociationLicensed by Information Handling Services STD-EEMUA PU5 NO 155-ENGL 1988 57bb734 0000225 81b M W J o - o I 1 d w -I o - o II H 4 7 ro =+LI) dZO n -HH rn z H x O CD rn z H O W CT 3 cr) H LL 13 Previous page is bla
45、nk COPYRIGHT Engineering Equipment and Materials Users AssociationLicensed by Information Handling ServicesSTDDEEMUA PUB NO L55-ENGL 1988 57bb73q 00U022b 752 CT O cn Z w rn n H O Z W _I O cn 7 n z d m W _I 6 U W O LL H 7 6 r d Q I cn Z OW U H e 4 W u Wd H s 4 z XH m Cu Cu W o= 1 cr) H LL 15 Previous
46、 page is blank COPYRIGHT Engineering Equipment and Materials Users AssociationLicensed by Information Handling ServicesSTD=EEMUA PUB NO 155-ENGL 1788 D 57bb734 0000227 b77 J3EMUA PUBLICATIONS. Publication No. DRILLING FLUIDS. 124 Drilling Fluid Materials. - Salt Water Clay (formerly OCMA Spec No DFC
47、P1.) 125 Drilling Fluid Materials. - Low Viscosity Carboxymethylcellulose. (formerly OCMA Spec No DFCP 2.) 126 Drilling Fluid Materials. - Barytes. (formerly OCMA Spec No DFCP 3.) 127 Drilling Fluid Materials. - Bentonite (formerly OCMA Spec No DFCP 4.) 128 Drilling Fluid Materials. - Starch (formal
48、ly OCMA Spec No DFCP 5.) 129 Drilling Fluid Materials. - High Viscosity Carboxymethylcellulose (formerly OCMA Spec No DFCP 7.) i30 Drilling Fluid Materials. - Tannin and Lignosulphonate Thinners (Deflocculants) (formerly OCMA Spec No DFCP 8.) 131 Drilling Fluid Materials. - The use of Iron Based Wei
49、ghting Agents in Drilling Fluids. (formerly OCMA Information Bulletin No 1.) ELECTRICAL. 132 Three-phase induction Motors. (formerly OCMA Spec ELEC 1.) 133 Underground Armoured Cable protected against Solvent penetration and Corrosive attack. (formerly OCMA Spec ELEC 4.) INSTRU?4E“ATION AND CONTROL. 119 The Selection of Automatic Control valves (1969) . (formerly EEUA Handbook No 32.) 120 Installation of Instrumentation and Process Control Systems (1973) . (1981 Reprint of EEUA Handbook No 34.) 4/88. Previous page is blank 17 ISBN No. 0 85931 097 3 O 859
