JBALB Exclusive : Moving Forward

What is Listening Bar?

Listening Stick/Bar uses mechanical amplification for detecting and pinpointing leakage and has an acoustic resonant chamber for noise amplification.

The two segment plated steel bar screws together to form a 1 metre length. Additionally, a three segment plated steel bar can be selected by the customer which extends the length to 1.5 metres.

The listening stick transmits the leak noise vibrations to a brass diaphragm within the resonant cavity. The radiated noise is mechanically amplified within the chamber to improve sensitivity.

Made from chromium plated mild steel, it is suitable for basic level leak detection and ideal for individuals who may experience difficulty in differentiating between static and leak noise on an electronic listening stick.

Preventive Maintenance of Single Air Valve

Valves must be accessible and maintained in good operating condition to be able to perform their function of isolation and/or control the flow of water in the pipeline. To facilitate this, it is necessary to know the exact location of each valve and be certain that the valve is in operating condition.

A site inspection should be carried out regularly for the following purpose:

(a)    To check that the location of the valve and surface box are recorded correctly on the locality plan;

(b)    To inspect the valve and surface box for evidence of leakage, damage or displacement.  Check the condition of valve packing or seal, stem, stem nut and gearing;

(c)    Operate the valve to its full open and closed positions, to prevent build-up of tuberculation or other deposits and ensure full valve travel.  A listening rod is useful for ascertaining that the valve is closed;

(d)    Valve chambers are cleaned out and drains freely;

(e)    Record all observations on the Valve Inspection/Maintenance Record on the reverse of the Valve Record card, noting particularly any follow-up maintenance required (e.g. replace packing, repaint, valve stiff, valve box shifted etc.).
Note:  The card is not to be removed from the office, but the information noted and entered on the card later.

(f)    It is desirable that all valves 300 mm diameter and larger, be inspected and exercised at least once a year and others at least once every 3 years.  However, the actual frequency may be varied depending on manpower availability and the relative importance of each valve.

(g)    A summary of inspection and maintenance should be recorded in the Monthly Reports of Water Supply.  (e.g. No. inspected, No. operable, No. not recorded, No. repaired).

(h)    Valves can be identified in the field by painting the number on the body or by attaching a metal or plastic tag.

(i)    Valves replaced or removed from the distribution system should be repaired, repainted, and kept in proper storage for future use.  Even valve requiring major repair, particularly large or expensive valves, can be considered for overhaul.

The following guidelines for flushing of distribution system may be followed:
(a)    Need to flush Distribution lines
The purpose of flushing is to remove sediments and stale water and to help maintain chlorine residuals throughout the distribution system.  It helps to reduce the occurrence of unsightly deposits in the water and eliminates unpleasant odour.

(b)   Rules of Flushing
(i) Prepare a map of the distribution system, showing the position of all valves and hydrants.
(ii) Always flush individual section of mains, by isolating valves at intersections during the flushing.  This allows a better velocity for given conditions.
(iii) Never flush a large main from a single smaller one - the volume will be insufficient to flush the larger main.  Trunk mains should be flushed prior to flushing branch lines.
(iv) Be careful not to shut down an area or mains inadvertently.  This can happen when working around mains already flushed and left isolated from unflushed mains.
(v) In most cases, a fully opened fire hydrant will provide adequate velocity to stir up the debris in a watermain.
(vi)Ensure that ‘slugs’ of discoloured water have been removed from junctures with mains previously flushed.
(vii)Avoid opening or shutting fire hydrant valves rapidly to avoid water hammer.
(viii) Never leave an area practically shut down overnight, as fire protection may be severely impaired.  Schedule work so that each zone can be completed by the end of the shift.
(ix) Avoid damage to streets or lawns.  Direct the flow from hydrants into the  wheel of a truck or drain, or devise on energy dissipater.
(x) Marked closed valves on a map and erase the marks when the gate valves are re-opened.
(xi) Watch out for construction projects or open manholes.
(xii) Ensure that all water contributing to a flow comes from cleared areas or from mains large enough to resist being stirred up by the flow.    
(xiii) Notify consumers in the area who might be affected by the flushing, such as the inconvenience caused by reduced pressure or dirty water.
(xiv) Keep lengths of main being flushed, as short as possible, especially on small diameter pipes.  Velocities must be kept high to be effective and the shorter the ‘run’, the higher the velocity attainable.
(xv) Do not hurry the flushing.  Make sure that all debris are eliminated.  In some areas if the water never really becomes clear, site judgement must be made by the supervisor on when to stop.
(xvi) As part of the flushing exercise, the team should take the opportunity to inspect all the valves, hydrants, air valves, pipelines, etc.
(xvii) Flushing should be carried out during the non-peak hours preferably at night to minimise supply disruption and for maximum effectiveness.

(c) Equipment and Manpower
A two-man team is generally sufficient for a flushing operation. The team should be equipped with a pick-up truck and the necessary valve keys, picks and other equipment.
(d) Records and Samples
(i) The flushing team must provide the engineer with the following information:
a.         Rate and time of flushing.
b.        Flushing points and location.
c.         Time required for water to run clear.
d.        Description and nature of the water. Presence of odour, discolouration and/or turbidity.
e.         Samples of the dirty water and final clear water.
f.         Reports on any defective valves, hydrants, air valves and leakages.
(ii) The volume of water used for flushing must be recorded and should be considered as accounted for water.  To measure the volume of water used, always install a hydrant standpipe and a standard 65mm diameter flow meter.