2 Features:(Functions and applications)
FLLQ gas roots flow meter is a volumetric one which can measure how much air through put in the sealed duct. The volume of gas is showed by monitor directly.
Specified as follows:
a) Small width range; small flow tumor-initiating.
b) No need of straight pipe; small space usage
c) Low power dissipation: one 2# 3.6V DC Lithium battery can continue to use more than two years.
d) Multiple functional; full and accurate parameter
e) Used with IC card payment system
f) Connected with users by remote set copy system to collect and manage data.
g) Setting password; power-off protective function

2 The usage of environment conditions:
Environmental temperature: -30℃～+55℃
Relative humidity: 5%～95%
Atmospheric pressure: 86kPa～106kPa
Working conditions:
Medium temperature: -25℃～+55℃
Nominal pressure: 1.6MPa
Power source: conventional type a. internal power supply: 3.6VDC Lithium battery, average current＜80μA
b. external power supply: 24VDC (two-wire system), electric current:4～20mA
c. external power supply: 24VDC (three-wire system), electric current:<100mA
Intelligent type a. internal power supply: 3.6VDC Lithium battery, average current＜200μA
b. external power supply: 24VDC (two-wire system), electric current:4～20mA
c. external power supply: 24VDC (three-wire system), electric current:<100mA

2 The form and attended mode of products:
Component elements: It is made up of sensor, converter or mechanical head of form.
Functional form:
a. Intelligent type: regarded microprocessor, flow sensor, temperature and pressure sensor as one part. To survey the flow, temperature and pressure of gas, compensate flow automatically, revise compressibility factor. Reflecting the integrated flux and the temperature and pressure of gas.
b. Conventional type: showing the integrated flux and instantaneous delivery.
Attended mode: connected with process pipe by flange; the standard of flange GB/T9113.1-2000
Shape and dimension: as the form 1

2 Working Principle:
FLLQ gas roots flow meter is a volumetric meter. The differential pressure, which is produced by the working of entrance and exit when the gas through the flow meter, will be link to super accuracy gear to drive the roots wheel rotating. During this period, it forms a confined space between the inside shell and cover plate. This space can charge and exhaust. The revolution of roots is proportional to the passing gas volume of flow meter. The rotation of roots transferred to flow integrating instrument by pulse signal to deal with, meanwhile to show the gross of gas.

2 Technical performance:
Operative norm:
GB 3836.1-2000 in accordance with detonating gas consumption of the first part: general requirements
GB 3836.2-2000 in accordance with detonating gas consumption of the second part: Flame-proof type “d”
GB 3836.2-2000 in accordance with detonating gas consumption of the forth part: Intrinsic safety “i”
JB/T7385-94 gas roots flow meter; Q/FM05-2005 FLLQ gas roots flow meter
Technical parameters and performance index: see the parameters in form 2

2 Electrical performance index
a) Frequency signal: frequency range 0.2Hz～700Hz
Extent: low level<0.5V, high level VD-1V (VD is the power supply voltage)
b) Analog output: a set of two-wire system 4～20mA , two sets of three-wire system 4～20mA
Current output can match along with among pressure, temperature, operating mode flow or standard flow.
c) communication interface: RS485 interface signal
Enclosure protection grade: IP65
Explosive-proof grade:
Intrinsic safety: Exia‖CT4～T6; Flame-proof type: Exd‖BT4

Installation
Installation requirements: According to the rules, some safety requirements that users must obey to design, install, supply power or operate the flow meter to ensure the safety. Before installation, the flow meter, especially the new pipeline or repaired one, needs to be pipeline purging to eliminate welding slag and rust and so on.
a) The intensified external magnetic filed disturbance and strong mechanical vibration should not be existed around flow meter. Before installation, we should use it according to the usage of environment conditions.
b) Installing the flow meter correctly; the hoisting equipments’ load and protection should be fit to rule. To hoist meter by rope is not allowed.
c) Ways of installation
Vertical installation: The gas entrance is above, that is, the airflow is entering from above and exit from bottom. Our factory suggests that use this way to help it improve the ability of self-cleaning.
Horizontal installation: the entrance and exit rope should not below pipelines’ axis to defend the impurity. And we can connect flow meter flange and filter flange.
d) It is necessary to install a regular filter on the upstream flow meter. When it owns a straight pipe and elbow at very beginning, it needs to be connected with filter mantle. It has been found that to install a regular filter is an effective way to reduce error and prolong life. And in order to maintain, the filter is accompanied by differential manometer.
e) Being given it coverings is to protect one from weathering if we install it outside. Leave enough space to check and repair.
f) Installing a bypass pipeline is to ensure the normal deliver. To close the bypass pipeline is a must under the normal condition.
g) The flow meter should install with pipe coaxial to avoid the gasket seal and butter entering the lumen.
h) The flow meter has to meet the ground reliably when installed in the explosion place. However, it can not use the same grounding line with high voltage system.
It is not allowed to catch the electric welding system. Users should not change the type, standard, attended mode and interface in any conditions. And it must operate follow the GB3836.1、GB3836.2 or GB3836.4 direction for use strictly.
After cutting the external electric supply, you can open the preoperculum of converter.
i) When operating flow meter, we should open the valve slowly to increase flow rate gradually to avoid the intensified momentary airflow damaging the rotor of converter.