Page 130 - PRESS-FIT SYSTEMS FOR DIVERSE APPLICATIONS

3.0 TECHNICAL DATA
SYSTEM DESIGN CONSIDERATIONS

AND TUBE EXPANSION

The water velocity required for flushing must be sufficient to pick up If the pipe system is to be left empty after the pressure test, then
and carry the majority of the dirt and debris from within the system. a pressure test with dry air and/or inert gas should be performed,
The hot and cold water pipelines should be flushed separately. (microbiological contamination through bacteria and corrosion of
carbon steel systems has to be avoided).
For details, please refer to the BSRIA Guide BG29-2012
’Pre-Commissioning Cleaning of Pipework Systems‘. The pressure test should consist of two steps;
Some contracts may still require that proprietary chemicals are used Leak test
to cleanse and flush pipework before full commissioning. XPress is Tightness test
compatible with a wide selection of products. To find out more contact The leak test involves inspecting the system for joint integrity
us. (tightness), the tightness test focuses on checking the system for
General Consideration strength.
All items that are sensitive to sediment must remain valved off and The tightness test with water is described in the B&ES Guide to Good
by-passed throughout the flushing procedure. Care should be taken to Practice TR/6, BS EN 806-4, BS6700.
ensure that pumps are not allowed to operate against a closed head for If pre-fabricated pipework or equipment has been hydraulically
long periods. This situation should be avoided whenever possible. pressure tested, off site prior to installation, this should be notified to
CHEMICAL CLEANING the cleaning/chemical treatment specialist as these may have already
Chemical cleaning should always be carried out immediately after developed an internal layer of corrosion, microbiological, biofilm build
flushing. up etc.
Chemical cleaning of the system should always be the responsibility of Due to the inherent dangers associated with pneumatic testing using
the appointed chemical cleaning specialist and should be preceded by inert gas or dry air a responsible person must be in charge of this
a properly executed clean water flushing as described in the previous operation at all times.
section. This is an essential pre-requisite to any effective chemical The following must be understood as a recommendation only.
cleaning programme. BASIC PROCEDURE
There are many proprietary cleaning chemicals available for preparing If the system is to be pressure tested (as recommended) then the
the pipework for subsequent service. Some of these are acidic, others following procedure applies to each section in turn.
are neutral but all must be capable of effectively removing any rust and
other debris that has formed in the pipework prior to commissioning, 1. Test Preparation
without damaging the various components in the system. a. Check that all high points have suitable vents to facilitate removal of
air during filling and that these are all closed.
Strong acid cleaners that do not contain inhibitor must be avoided as
severe internal wastage may occur, particularly at joints between tube b. Install suitable drainage facilities at all low points for drainage.
and fitting. c. Blank plug or seal any open ends and close all valves at the limits of
Irrespective of whatever cleaner is chosen, the manufacturer’s the test section of the piping
instructions must be followed exactly, taking particular care to ensure d. Remove, blank off all terminal units that may be damaged by the
that cleaning agents are completely flushed out of the system before test pressure.
adding any protective inhibitors to the water.
e. Open all valves within the enclosed test section.
Please refer to BSRIA BG29 2012 f. Check that the test gauge is working correctly and has been
‘Pre-Commission Cleaning of Pipework Systems’.
calibrated, and has the correct range.
As this is specialist work, it should only be entrusted to an organisation
that has the facilities, safety training and experience in dealing with the g. If the compressed dry air or inert gas is at a higher pressure than is
required for the test (maximum 0.5bar pressure) a pressure reducing

potentially hazardous chemicals involved. Suitably qualified personnel
will have the knowledge to be able to offer advice on the selection valve, pressure gauge and pressure relief valve set to open at the
test pressure should be fitted to the connecting pipework.
and use of appropriate chemicals, as well as the safe disposal of waste
material. h. If possible the compressed air supply should be outside the test
area
PRESSURE TESTING OF PIPEWORK SYSTEMS
i. Check that there is a suitable method for draining the system.
It is recommended that completed pipework systems are pressure
tested prior to being covered (insulation, or paint), and should be It is recommended that systems be tested with a nitrogen rich (90%)/
performed prior to commencing the cleaning procedure. air mixture. If air is to be used it should be clean, dry and free from oil,
the drying performance should conform to ‘purity class 3 under the ISO
The entire system should be pressure tested in accordance of BSRIA 8573’ for particulate contamination, water and oil content.
and B&ES.
Guidance should be sought from the relevant compressor manufacturer.
This pressure test can be both pneumatic and hydraulic and is
determined by the installed and planned commissioning regime.

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