CEN/TC 54/WG 4 - Expansion vessels for thermal installations

This European Standard specifies requirements for the design, manufacture and testing of closed expansion vessels with built in diaphragm, which will hereinafter be called "vessels", and
a)   whose diaphragm serves to separate water on the one hand and air / nitrogen on the other hand in heating/cooling systems or fresh water systems;
b)   which are manufactured singly or in series;
c)   which may consist partly or entirely of (cold) deep-drawn parts;
d)   whose parts may be joined by welding, clenching or flanges;
e)   whose size is not limited;
f)   whose maximum allowable pressure is greater than 0,5 bar, yet not exceeding 30 bar;
g)   whose upper wall thickness is limited to 12 mm for austenitic steels and 15 mm for ferritic steels;
h)   whose minimum operating temperature is not below -10 °C, whose maximum operating temperature is not above 70 °C.
NOTE   The maximum operating temperature of 70 °C is determined by the characteristics of the diaphragm materials. It may be higher, if suitability of diaphragm material is proven.
Whatever the temperature in the heating system, for the vessel operation the decisive factor is the maximum operating temperature of the diaphragm. It is the system designer's responsibility to prescribe measures to protect the diaphragm from unsuitable temperatures (e.g. connection to the coldest part of the system in a heating system, to the warmest in a refrigeration circuit; thermostatic monitoring of connection to vessel or intermediate vessel).
For cases where operating temperatures above 70 °C cannot be avoided the suitability of the diaphragm material is to be proven (see Clause 8).
When reference is made in this European Standard to EN 13445-1, -2, -3, -4 and -5 respectively, all relevant provisions in the concerned clauses of these standards need to apply.