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Armstrong Integrated Systems Ltd
Pressurisation & Boosting Selection
Armstrong - Pressurisation Unit & Expansion
Vessel Selection
In order to correctly size pressurisation
equipment in LTHW and Chilled Water Sealed Systems it is necessary
to establish certain information. The answers to the questions below
will ensure that the correct unit is selected when using Armstrong
PC selection program, (copies available on request), or when
requesting selection by the sales department. The information
required is as follows:-
1 Where will the pressurisation unit and expansion vessels be
installed? Will the location be a basement, or roof-top plantroom,
or somewhere else?
2 Is there a suitable water supply at this point?
3 What is the static head at the pressurisation unit? i.e. What is
the height from the pressurisation unit to the topmost radiator or
service point above it?
4 What is the boiler/chiller rating?
5 What are the flow and return temperatures?
6 What is the total water content of the system?
7 What size of pipe is being used and therefore what size of air
separator is required?
8 What is the proposed position of the circulating pump in relation
to the boiler/chiller?
9 What is the duty of the circulating pump?
10 What is the maximum allowable pressure, (pressure at which the
safety valve starts to open)?
11 What is the percentage of antifreeze to system volume?
Methods of Supplying the Maximum Probable
Simultaneous Demand (MPSD) with a Booster Set
In the majority of applications a booster unit
must provide for the MPSD. Since this is not normally a continuous
requirement, the following methods of sharing the demand may be
considered:-
1 Where the flow rate requirement is small, a two pump unit can have
each pump sized to cater for 100% of the MPSD, one pump acting as
the duty pump, the other as standby.
2 Alternatively, the two pumps can each be sized to handle 60% of
the MPSD, where the second pump is switched in to cater for the
occasions when peak demand occurs.
3 Where the flow requirement is high, it is more economical to
select a three-pump unit such that the duty of each pump is 50% of
the MPSD. Here the pumps function respectively as duty, support and
standby.
A jockey pump with a small capacity can also be added to any of the
above arrangements, which will save energy during low demand
periods. Alternatively, a larger pressure vessel can be supplied to
cater for long periods of low demand, from small draw-off points on
the rising main, e.g. vending machines.
Boosting Pump Selection Chart
(Click on chart for larger image)
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Armstrong Integrated Systems Ltd
Wenlock Way
Manchester
M12 5JL
Email this company
Tel: 0161 223 2223
Fax: 0161 220 9660
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