Page 131 - PRESS-FIT SYSTEMS FOR DIVERSE APPLICATIONS

Excessive oil carry over in compressed air may be detrimental to the c. Turn the pump on to allow the system water to circulate to help
EPDM seals as well as causing bacteriological issues. Pure Nitrogen is reduce the risk of trapped air, bleed the system if necessary. Turn off
also acceptable but consideration should be taken of HSE guidelines or the pump set when completed.
recommendations. d. Check the system contains the correct amount of inhibitors and
2. Pneumatic Pressure Testing biocides.
a. An initial low-pressure test at 0.5 bar is to be carried out, having put e. Using an independent pump set, progressively increase the pressure
the necessary safety measures in place, to enable any leaks to be until the system pressure achieves 1.5 times normal working
found. pressure, (verify that this pressure is within the capability of the
Significantly leaking, un-pressed or damaged joints shall be system components), record the test pressure.
replaced, but those with low leakage rates should be identified for f. Leave the system for 30 minutes minimum.
close inspection during the high-pressure test.
g. The test is passed if the pressure in the system is maintained for the
b. This test pressure is to be maintained / pumped for a period of 30 next one hour and there is no visible leakage throughout the test.
minutes minimum.
h. Leaking joints at this stage should be identified and marked for
c. The test is passed if the pressure in the system is maintained for one replacement.
hour and there is no visible leakage throughout the test.
i. The system pressure should then be reduced to 0.5 bar again to
d. If required, a signature should be obtained on a test certificate. confirm that no persistent low-pressure leaks are present.
e. After testing, safely release the pressure, if necessary ensure that all Further information can be found in;
vents on cylinder tanks and pressure vessels are opened to
atmosphere BEFORE draining down and refitting vulnerable items. Guides issued by BSRIA, B&ES, CIBSE, WRAS and the Copper
Development Association (CDA) Guideline document ‘Pressure Testing
These test times may vary according to the pipework system (plastic Piping Systems’.
pipe systems may take longer to achieve stable pressures). PRESSURE TEST FOR NATURAL GAS SYSTEMS
Water Regulation 12 requires ‘that the water system shall be capable
of withstanding an internal water pressure not less than 1.5 times the Important: The pressure test for natural gas and liquid gas systems
maximum pressure to which the installation or relevant part is designed must be performed in accordance with local regulations.
to be subjected to in operation’. PRESSURE TEST OF SPRINKLER SYSTEMS
When hydraulic testing is undertaken then the following should be The tubes of the sprinkler system must be subjected to a pressure test in
carried out. accordance with valid guidelines, such as CEA 4001, no. 17.1.1. (VdS) for at
least two hours. A pressure (measured at the alarm valves) corresponding
The test water should contain anti-corrosion inhibitors / long lasting
biocide chemicals with the intention that post testing the system shall to 1.5 times the permitted positive operating pressure – but of at least
be left completely full of the test water (suitable protection against 15 bars – must be maintained during the test. This pressure test is a
freezing and the onset of biological growth will also have to be check of both the strength and tightness of the system. The system
considered). Circulation of the system test is strongly recommended. must be monitored for 24 hours for any pressure drop due, for example,
to temperature changes. Dry sprinkler systems must also be tested
If leaving the system full of water is not practical then every effort shall pneumatically to a pressure of not less than 2.5 bars for at least 24 hours.
be made to fully drain and dry the pipe work by purging with dry air/ Any leakage, which occurs and results in a pressure drop of more than 0.15
nitrogen. If the system is to be left not in use for longer than 5 days, we bar over the 24 h, must be corrected.
recommend that the system be left charged with an inert gas to reduce
the risk of onset corrosion and /or bacterial growth. Any faults identified, such as permanent deformations, ruptures or
leakages must be corrected and the pressure test repeated.
Do not leave a Carbon Steel system empty without drying as oxygen
will begin to corrode the internal surface. TUBE BENDING
Portable bending machines are ideal for bending tubes up to 28mm.
Inspection of the internal condition to the pipework is recommended
so that the water treatment specialist understands the correct process Most machines bend the tube between matched formers and back
required when cleaning. guides that support the outside diameter (OD) of the tube. This
eliminates the risk of the tube wall collapsing.
3. Hydraulic Pressure Testing
The point at which the bending pressure is exerted must be maintained
a. Start to fill the system and ‘walk’ the route of the pipework being at the correct distance in front of the former’s point of support. It’s also
tested. Visually checking for leaks and listening for the sound of important to keep formers and guides well lubricated. Bending tubes
escaping air. correctly will avoid any wrinkling and flattening that can affect flow
b. Release air from all the high points systematically through the conditions.
system to ensure the system is completely filled with water. (The full Using adjustable bending machines (which allow the pressure on the
loading of the o rings often resolves small leaks identified during the back guide to be adjusted) will ensure perfect bends every time so long
0.5 bar test). as the root (inside) bending radius is 3.5 times the outside diameter of
the tube. Up to 28mm Carbon and Stainless and 54mm Copper.

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