Palmer Lmic User manual

Acoustic Listening Systems
Lmic, Gmic and Rmic
Operating Manual
Palmer Environmental
Ty Coch House
Llantarnam Park Way
Cwmbran
NP44 3AW
United Kingdom
Tel: [phone]
Fax: [phone]
Email: [email protected]
Web: www.palmer.co.uk
Acoustics Manual Issue 1 January 2003

1
Contents
Introduction and Scope ........................................................................................... 2
Guidance to Effective Acoustic Leak Detection .................................................... 3
Battery Warning........................................................................................................ 5
Lmic Acoustic Leak Sounding System .................................................................. 6
Preparing the Lmic for use...................................................................................... 7
Using the Lmic ......................................................................................................... 8
Lmic Technical specification .................................................................................. 9
Gmic Acoustic Leak Sounding System................................................................ 10
Gmic Controls ........................................................................................................ 12
Preparing the Gmic for use ................................................................................... 13
Using the Gmic....................................................................................................... 14
Gmic Technical Specification ............................................................................... 16
Rmic Acoustic Leak Sounding System ................................................................ 18
Microphone foot warning ...................................................................................... 19
Using the Rmic ....................................................................................................... 21
Rmic Technical Specification................................................................................ 22
Warranty.................................................................................................................. 24

2
Introduction and Scope
This manual covers the principles in acoustic leak detection for the following
products produced by Palmer Environmental.
Lmic (pronounced El Mike) Low cost leak sounding system
Gmic (pronounced Gee Mike) Ground microphone - leak sounding system
Rmic (pronounced Are Mike) Road microphone - leak sounding system.
The basics in the general operation are the same but each system has its own
advantages.
Lmic is designed as a low cost lightweight system which is simple to use yet highly
effective in the detection the sources of leak noise in industrial, commercial and even
household situations and can be used as a tool as part of a plumbing tool kit.
Gmic is a more sophisticated piece of equipment containing filters and the option of
aviation headphones. This combination provides the operator with a highly effective
listening device with the ability to virtually eliminate unwanted or interfering ambient
noise.
Rmic has the features of the Gmic but has the additional capability of being able to
use an acoustically shielded ground microphone foot for use in all weathers
especially high wind. The Rmic foot virtually eliminates the noise produced in bad
weather conditions and is especially suited for use on hard road surfaces, tarmac,
concrete etc.
The following section provides an introduction to the methods of acoustic leak
detection.

3
Guidance to Effective Acoustic Leak Detection
All acoustic leak detection methods are based on the premise that normal water
passage through pipelines takes place noiselessly. When the water passage is
disturbed a noise is created. Causes can include partial pipe blockages, sudden
changes in pipe diameter, abrupt changes in pipe direction, pumps or meters
installed in the pipeline, consumer usage or pipeline damage. Pipeline damage can
include holes, cracks or splits, complete pipeline rupture, leaking joints or leaking
valves.
Careful application of leak detection techniques will enable the operator to eliminate
detected noises generated by poor pipeline design or consumer usage and to
identify leakage due to pipe system damage.
The strength and clarity of noise generated by leaks will be affected by the water
pressure, the size and shape of the orifice allowing leakage, the type of ground
material around the pipeline, the type of ground cover over the pipe, the diameter,
wall thickness and material of the pipeline and the quantity of water leaking.
A small orifice or hole and high water pressure generally produces a higher
frequency noise. Often the noise level increases around valves, pipe elbows, T
connections, pipe ends, etc. since the partial obstruction increases pressure and
creates some further disturbance in the water path.
Leak noise is transmitted along the pipeline both through the water and the pipe wall
as well as into the ground around the pipe. The noise travels much better through
"hard" materials so that the noise travels much further along metallic pipes than
asbestos cement pipes which themselves are better than plastic pipes. Ground
material generally provides a poorer travel path than the pipeline itself. Soft sandy
ground provides a worse travel path than well compacted ground with a hard paved
surface covering.
The leak noise can change in strength and pitch as it travels along the pipe or
through the ground. The deeper the pipe is buried and the softer the ground the
more the noise will be dampened.
When a leak is produced in a metallic pipe the leak noise will transmit well through
the pipe. It does not travel so well through a plastic pipe. This means that a leak
noise can be heard further away on metal than on plastic. Also bear in mind that the
further you go from a leak noise source the more difficult it is to pinpoint that leak
noise accurately.
Background noise can interfere with leak detection. Traffic and machinery noises can
travel for considerable distances through both air and ground material and often
occur in the same frequency bands as leak noise. Sometimes it is necessary to use
leak detection techniques at night when interfering noises are less.
It is very important to adopt a methodical approach when using any instrument for
acoustic leak detection. It is necessary to practice the technique in order to
distinguish between different sounds, recognising background or interfering noises,

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so that they can be eliminated. It is also essential that other (non-leakage) noise
sources such as consumer draw-off or partially closed valves are eliminated by
logical site inspection practices prior to any excavation taking place.
Hand probe
For normal soft ground surfaces the single pointed extension rod should be
connected - do not overtighten the screw thread. For direct contact with underground
fittings via access covers it may be necessary to use the second extension rod. To
do this remove the single rod and connect the extension rod - replacing the pointed
rod again. If the rods have been overtightened, spanner slots allow easy removal.
Surveying
The leak location can be narrowed down by listening at accessible contact points
such as meters, hydrants, valves and stop-taps, which provide points of good sound
pick-up particularly if the pipe is metallic. Use the hand-probe/extension rod to listen
at these points.
If there are no accessible contact points or if the pipe is of non-metallic material use
the microphone foot for listening, placing the foot over the pipe route in the area of
the suspected leak. Move along the pipe route listening at each accessible pipe-
fitting or at regular positions on the ground until you have identified the area of
maximum noise level.
Note: When you are listening on pipe-fittings the location of the point of maximum
noise will probably not indicate the leak position, only the fitting closest to the leak.
The noise level will also appear stronger where there is less thickness of ground or
other material for it to pass through. The leak noise will follow the path of least
resistance.
Pinpointing the leak position
Pinpointing the leak position involves a process of comparing a number of leak
noises. Select the most suitable sensor device; the microphone foot for hard ground
surfaces or the hand probe for soft ground.
Operate the ground microphone and adjust the headphone volume control to a
comfortable listening level. Once you have listened to the noise through the
headphones, switch off the amplifier (hand button on the Lmic or the headphones
button on Gmic/Rmic) and move the microphone foot or hand probe to the next test
position.
Repeat the sequence to listen to each of the test locations moving along the pipe
route in the direction where signal strength is increasing. If the leak noise level falls
you have passed the leak and should go back and reduce the distance that you
move between measurements. The loudest leak noise will then indicate the location
of the leak bearing in mind the ground conditions already mentioned.

5
Battery Warning
Gmic and Rmic
The batteries supplied and fitted to the Gmic and Rmic units are rechargeable lithium
ion. Do not short circuit or overcharge these batteries. Any misuse of these
batteries may result in explosion or fire. They must not be used in any other
application or used with any other equipment. Only batteries supplied by Palmer
Environmental must be used.
Lmic
The battery fitted to the Lmic is a rechargeable 9V PP3 Nickel Hydride battery. Any
replacement battery must be rechargeable and have the same specification.

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Lmic Acoustic Leak Sounding System
The Lmic (pronounced “el mike“) is an easy-to-use, low cost, electronic listening stick
and ground microphone combined. It is ideal for general leak sounding operations
and can be fitted with either a tripod foot (for use as a ground microphone) or probe
rods (for sounding at fittings or in soft ground).
The control unit is hand-held with a “trigger” operation and a volume/sensitivity rotary
control. An LED indicates operation and battery status. It can be used to confirm
the position of underground leaks audibly from ground level; sound pipe fittings;
penetrate soft ground to listen for leaks or carry out traditional acoustic surveys.
Equipment list
1 Lmic hand held control unit
2 Microphone unit with cable
3 Tripod unit
4 2 probe rods
5 AC adapter
6 Headphones
7 Carry bag
8 Instruction manual
The Lmic equipment is shown here.
(Note the battery charger and
manual are not shown).
Lmic Controls
LED Rotary volume/sensitivity
control
Headphones /battery
charger connection
Trigger
switch
Microphone
connection
1
3
6
4
2
7
Bottom view of the Lmic showing the
trigger switch and the electrical
connections for the headphones/battery
charger and microphone.
Top view of the Lmic showing the rotary
control for volume and sensitivity.

7
Preparing the Lmic for use
The rechargeable 9v PP3 battery for the Lmic is supplied installed within the hand
control unit and will normally have only a nominal charge.
The battery will need charging either overnight (for up to 7 hours) to achieve full
charge before being ready to use.
Charging the Lmic batteries
Connect the charger lead to the rear connector of the Lmic and connect the charger
power lead to the 240V AC supply. The Lmic can then be charged overnight. An
optional accessory is the car cigarette lighter adapter that can also be used to
charge the batteries.
Battery replacement
Although these batteries are rechargeable they may eventually need to be replaced.
To do this, undo the two screws underneath the hand-held unit and separate the two
halves of the Lmic unit. Gently pull out the battery holder and replace the batteries.
When refitting the batteries and battery holder make sure no wires become trapped.
The Lmic connected to the universal 110-
240V AC charger

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Using the Lmic
The Lmic is simple to operate. Select either the probe rods or the tripod unit and
screw into the microphone unit. (Use the tripod foot on hard ground and use the
probe rods on soft ground or when accessing water pipe fittings).
Connect the headphones to the rear connector and connect the microphone cable to
the forward connector. Put on the headphones and press the trigger button
underneath the hand-held unit to listen for leaks.
The volume/sensitivity can be adjusted using the rotary control.
LED indication
The green LED shows when the unit is operating and the red LED indicates low
battery power.
Care of the Lmic
The Lmic should be kept clean and dry and, where necessary, cleaned with a damp
cloth; abrasive materials must not be used.
The Lmic in use

9
Lmic Technical specification
Lmic hand held unit/sensor housing
Piezoelectric high sensitivity sensor mounted in PC-ABS (polycarbonate) housing
Single headphone/charger input socket with automatic sensing of device connected
Connectors
Amphenol military specification connectors for microphone and headphone/charger
connections
Charging
Universal 110-240V AC charger with 12V DC output
Car cigarette lighter adapter with 12V DC output (optional accessory)
Charge time: Overnight charge.
Microphone housing
High sensitivity piezo-electric sensor mounted in rubber housing with integral strain
relief
Low noise 0.75m cable (detachable)
Weight: 400g
Foot attachment
Cast metal tripod for ground contact
Hand probe attachment
2 stainless steel extension rods (each 400mm long)
Weight: 150g
Headphones
Lightweight high quality headphones
Impedance: 16 Ohms
LED
Green = normal operation
Red = low battery power
Optional accessories
•High specification aviation quality headphones
•Car cigarette lighter adapter with 12V DC output
•Acoustically shielded ground microphone foot, for use in all weather conditions