Bacharach Hi Flow Sampler Manuel Du Propriétaire

Hi Flow Sampler 

Introduction 

Instruction 0055-9017 

1

 

 

The Hi Flow Sampler is portable, intrinsically safe, battery-powered 
instrument designed to determine the rate of gas leakage around various 

pipefittings, valve packings, and compressor seals found in natural gas 
transmission, storage, and compressor facilities.  

 
A component’s leak rate is measured by sampling at a high flow rate so 
as to capture all the gas leaking from the component along with a certain 

amount of surrounding air. By accurately measuring the flow rate of the 
sampling stream and the natural gas concentration within that stream, 
the gas leak rate can be calculated using Equation 1. The instrument 

automatically compensates for the different specific gravity values of air 
and natural gas, thus assuring accurate flow rate calculations. 
 

Leak = Flow x (Gas 

sample

 – Gas 

background

) x 10

–2

 

 

 

where: 
 

Leak = rate of gas leakage from source (cfm) 

 

Flow = sample flow rate (cfm) 

 Gas 

sample

 =  concentration of gas from leak source (%) 

 Gas 

background

 = background gas concentration (%) 

 

To ensure that the instrument is capturing all the gas that is escaping 
from the component, two measurements are performed at two different 
flow rates. The first measurement is taken at the highest possible flow 

rate, followed by a second measurement at a flow rate that is 
approximately 70–80% of the first. If the two calculated leak rates are 

within 10% of each other, then it can be assumed that all gas has been 
captured during the test.  
 

For those mathematicians who are wondering how both calculations can 
be the same with different flow rates, note that the measured CH

4

 level at 

the lower flow rate will be higher due to less air being drawn in with the 

sample, thus balancing out the lower flow rate.  
 
The instrument is packaged inside a backpack, thus leaving the 
operator’s hands free for climbing ladders or descending into manholes.  

 
The instrument is controlled by a handheld unit consisting of an LCD 

and a 4-key control pad, which is attached to the main unit via a 6 foot 
coiled cord.  
 

The gas sample is drawn into the unit through a flexible 1.5 inch I.D. 
hose. Various attachments connected to the end of the sampling hose 
provide the means of capturing all the gas that is leaking from the 

component under test.  
 
The main unit consists of an intrinsically safe, high-flow blower that 

pulls air from around the component being tested through a flexible hose 
and into a gas manifold located inside the unit. The sample is first 

passed through a venturi restrictor where the measured pressure 
differential is used to calculate the sample’s actual flow rate. Next, a 
portion of the sample is drawn from the manifold and directed to a 

combustibles sensor that measures the sample’s CH

4

 concentration in