Heating systems – Water – Expansion tanks
Patent
1998-10-13
2000-09-19
Joyce, Harold
Heating systems
Water
Expansion tanks
137205, 137202, F24D 310
Patent
active
061199516
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for expansion control in a closed fluid circulation system with varying temperature, in which system air or another gas present is withdrawn from the circulating fluid through the formation of an air or gas head wherein air or gas to be withdrawn is collected and from which air or gas can be blown off, controlled by a valve, to the environment or a receiving space, whilst, further, measures are taken for taking up, when the temperature varies, an attendant expansion and shrinking of the fluid within the closed system, and measures for enabling adding fluid to the system, which fluid is withdrawn from an external stock of fluid under pressure. The invention also relates to a closed fluid circulation system for carrying out a method as referred to hereinabove.
Such a method is generally known from central heating engineering, and the measures for taking up the expansion and shrinking of the fluid at a varying temperature typically comprise an expansion tank subdivided by a diaphragm into two separate spaces, one space being in open communication with the network of pipes and the other space containing a gas capable of taking up variations in the volume of the fluid caused by a varying fluid temperature, through compression or expansion by means of a displacement of the diaphragm. For venting automatically, a float-controlled valve can be used, such as is for instance known from U.S. Pat. No. 4,027,691.
In such a fluid circulation system, fluid leakage will virtually always occur, although usually only to a very small extent, and often it cannot be established where that leakage occurs, because a small leaking amount of fluid, in the case of central heating systems virtually always water, evaporates almost directly. In this manner, the compensation capacity of the expansion tank may become exhausted and the pressure in the closed system may drop below a minimum pressure, resulting in failure of the heating system with all its unpleasant incidental circumstances, such as a cold living environment or even the freezing of conduits. The leaking of fluid may also entail the ingress of air, which air, in the presence of a float-controlled vent valve according to U.S. Pat. No. 4,027,691 is automatically discharged again, which also influences the pressure drop in the closed system. If the system is to remain operational, the pressure should be checked regularly and, if necessary, fluid should be replenished, which is usually a laborious and wet affair.
The object of the invention is to provide a method with which an expansion control in the closed fluid circulation system can be obtained such that, in fact, it continues functioning automatically and without regular supervision.
A further object of the invention is to realize the expansion control with means which are as simple and cheap as possible.
In accordance with the invention, an automatic, self-regulating expansion control with a method of the type described in the opening paragraph is realized in that the volume of the air or gas head is monitored and, when a predetermined value of that volume is exceeded, a fluid valve is opened through which fluid is introduced into the air or gas head until it is established that the volume of the air head is substantially equal to the predetermined value again and the fluid valve is closed again. Through these measures, fluid replenishment will automatically be provided for as soon as the fluid volume in the closed system drops below a predetermined minimum, so that system failure caused by too low a pressure is prevented.
Because the air or gas head is in direct communication with the fluid circulating in the circulation system, the drop of the fluid level below the predetermined minimum will virtually always occur when the temperature and, accordingly, the pressure of the circulating fluid is lowest. In that case, the pressure difference between the air or gas head and the make-up fluid is greatest, which has the further advantage that through the supply of the replenished fluid into t
REFERENCES:
patent: 3888274 (1975-06-01), Weston
patent: 4027691 (1977-06-01), Roffelsen
patent: 4823830 (1989-04-01), Bucker
patent: 4951701 (1990-08-01), Boehmer
patent: 5069243 (1991-12-01), Foreman
patent: 5456409 (1995-10-01), Roffelsen
Boles Derek S.
Joyce Harold
Spiro Research B.V.
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