BS 6657:2002 pdf download – Assessment of inadvertent initiation of bridge wire electro-explosive devices by radio-frequency radiation — Guide

BS 6657:2002 pdf download – Assessment of inadvertent initiation of bridge wire electro-explosive devices by radio-frequency radiation — Guide
5.3 Responsibility for making the hazard assessment
The radio-frequency(RF) environment is becoming increasingly severe, with the proliferation oftransmitting sources and increased transmitter powers and the exploitation of new techniques.
NOTE1 UK legislation [l] requires that employers safeguard both their employees and others who may be placed at risk by theiractivities. Hence, both operators of RF transmitters and users of EED have a responsibility to ensure safe operation.
NOTE2 Particular locations such as mines and quarries may exist where additional responsibilities are placed on the owners andmanagers.
Operators of a proposed site in which EED are to be used should request details from the transmitter
operators about relevant transmitters in the locality of the site. The transmitter operators should includedetails of transmitters for broadcast, commercial, military, air traffic and emergency services such as
police, fire and ambulance.The site operator should then use the assessment procedures given in thisBritish Standard, if necessary in consultation with the transmitter operators concerned.
Similarly, an operator of a proposed new(or altered) transmitter should contact all operators of sites whereEED are used within the minimum distance of safe approach for the transmitter, and use the procedure
given in this British Standard to assess the potential hazard at each location.
Where both the site and the transmitter already exist but an assessment is required, the site operatorshould be held responsible for ensuring that the assessment is made. If for some reason relevant
information cannot be made available to the body responsible for the assessment, the responsibility forhaving the assessment carried out should be assumed by the body unable to release the necessary
information.
NOTEB As an aid to those who need to make a hazard assessment but do not have the necessary technical resources, a list of sourcesof information and specialist orzanizations capable of providing consultation or test facilities is given in Annex C.
5.4 Recommended practices for radio silence in offshore operations
‘The position adopted by many offshore operators has been to switch off all transmissions from theinstallation during the surface preparation of the explosive tool until its immersion in the well at 70 mbelow sea bed level.At this point services would be restored until the explosive tool was returned to a
similar depth on the upward journey when all services would again be cut of.Following its removal fromthe well and inspection to ensure its safe condition, services would be restored provided no further
explosive handling was to take place.
However, too great a reliance on all-embracing curtailment of services can itself present a potential hazardto structures which employ radio communication for safety reasons and as an integral part of producttransportation systems (pipelines).The identification of these difficulties has highlighted the need for thehazard to be more accurately quantified in order to minimize the disruption of other necessary operationsand to avoid the creation of further potential hazards.
6 Transmitters and transmitter output parameters6.1 Types of transmitters
This clause provides information on various types of transmitter and transmitting systems. This
information is necessarily rather brief for certain types of radar and other military equipment but basicdetails are given and further information may be sought from the specialist organizations listed in
Annex C.Typical types of antenna installations are shown in Figure D.1.
6.2 Frequency range
The main frequency range covered is 9 kHz to 60 GHz.The types of transmitter considered include thefollowing:
a) radio and television broadcast transmitters in specific bands in the range 0,15 MHz to 1 000MHz;b) fixed and mobile transmitters for communication purposes, private, commercial and amateur, inspecific bands above 0,4 MHz and for military use above 0,15 MHz;
c) radar, in specific bands at 220 MHz,600 MHz and above 1 GHz;
d) navigational equipment, non-directional beacons, etc., from 9 kHz upwards.
6.3 Transmitter output power Transmitter output power from several watts up to megawatts may be encountered depending on the frequency range and the application. The method of specifying the power varies, which is significant for the hazard assessment when highly directional antennas are in use and when considering different modulation systems. In general, values are specified in the technical documentation for either the carrier or peak power output from the transmitter together with the antenna gain, although the product of the two is often quoted in the technical documentation to give the equivalent isotropically radiated power (EIRP). 6.4 Antenna gain The reference antenna is often an isotropic antenna that radiates uniformly in all directions. Although this is a purely hypothetical concept it is nevertheless very useful for reference purposes. When the gain of an antenna relative to an isotropic reference antenna is stated in decibels it is denoted by dBi. In practice, the gain of an antenna is often expressed relative to a half-wave dipole which itself has a gain of 1,64 (or 2 dB) relative to an isotropic antenna. In special circumstances other reference antennas may be used, for example a short monopole. It is therefore important that the reference antenna is correctly specified. The maximum gains for typical antennas are included in Table D.1, Table D.2 and Table D.3.