Since 1980, G.S. has set up a laboratory where heating-system tests are performed. Such tests aim at periodically checking product characteristics and carrying out research and development. The first case involves random tests, meaning tests performed on a significant number of products - from the odd one or two up to a dozen - or on production batches, meaning tests performed on a statistically significant number of products belonging to a production batch. This latter type of test normally aims at checking valve seal for industrial use with special focus on valves for the gas market. In view of the versatility of the entire laboratory setup, all tests can be performed both in compliance with the procedures laid down by the different European and non-European standards, and with the different and more stringent requirements called for by research and development company programmes and complete production performance inspections. The laboratory consists of various hydraulic circuits, all interlinked, supplied by various pumps with characteristics that differ according to test requirements (flow capacity and pressure); adjustment valves supported by bypass systems and storage tanks ensure precise and stable flow and pressure adjustment in all test sections. The flow capacity measurements are taken using variable-section flow meters calibrated and periodically checked using a weighing method which produces measurement results affected by errors below 3%; for very precise measurements relating to fairly low water flow values, direct weighing can be done using a precision scale, with a few errors per thousand. The temperatures in the various points of the test circuits and sections are determined by J-type thermocouples (iron-costantan) and PT100 thermistors. The absolute and differential pressures are determined both by means of a group of different-density liquid pressure gauges (water r=1, acetylene tetrabromide r=2.96, double-distilled mercury r=13.55 ) and using precision metal pressure gauges (class 0.3) and absolute and differential pressure transducers (class 0.1) all with different full scales for correct use in relation to the test measurement range. The laboratory has a sample instrument for the periodical calibration of all the pressure gauging instruments and sample weights for the periodical calibration of the scale used for flow measurements.
The essential aspects of the types and procedures of the tests that can be performed are given below:

1 - Pressure drop tests - These can be performed both with water at a temperature between 15 and 90 °C and an absolute pressure between 1.1 and 10 bar, and with air at ambient temperature and absolute pressure between 1.01 and 6 bar.
The test section is made with brass pipes and unions, for the water circuit, and of plexiglas, for the air circuit, arranged horizontally with an axial length of over 23 diameters; the pressure points feature an annular chamber with three 120° holes arranged at different distances from the valve to be tested. At least six points are detected of the hydraulic characteristic of the valve being tested with rising flow capacities (upward points). These are then read again with falling flow capacities (downward points) with average determination of the pressure per point obtained with 30 readings of the transducers or after prolonged observation of the pressure gauge meniscus or needle. Three valves of each series and diameter are normally tested using this method and data such as the averages of the tested valves are shown in graph form (pressure drop-flow capacity diagrams) or on printouts; data are completed with indication of flow capacity factor and equation of single hydraulic characteristics obtained by interpolation of the test points. In the event of the pressure drop being read by means of the pressure points located away from the valve, the figure read is corrected by means of the hydraulic characteristic of the test section determined by experimentation and theoretically checked.

2 - Flow capacity tests - These are tests normally performed on tapware and envisage the use of water at a temperature between 15 and 90°C and with absolute pressures between 1.1 and 12 bar. The test section is made from stainless steel with suitable unions and toroidal three-hole pressure points positioned at 10 diameters from the singularities or in accordance with the requirements of specific and special standards. The test consists in detecting not less that six points of the component characteristic upwards and an identical number downwards with average pressure reading as described at para. 1 above. The test results are presented as the average of various tests repeated on at least three components and provided on flow capacity-pressure diagrams, if necessary complete with curve equations.

3 - Air-tightness test - These tests are normally performed on industrial component parts at temperatures between -40 and 250 °C and pressures between 1.05 and 80 bar. For temperatures between 20 and 250 °C especially, a suitably equipped thermostat-controlled oven is used, while for low temperatures a cryostatic bath is employed. The test section is mainly used for random inspections and studies and research into the characteristics of the valves, especially as regards the seal material, their shape and their coupling with the shutter and body. Test procedures are diversified according to the goals to be achieved and can essentially be performed with the valve closed or half open, if necessary performing a limited number of opening and closing operations. Inspections can be made by keeping the valve in test conditions or returning it to lower pressures and/or temperatures right down to ambient temperatures with various gradients. Display of the leak is conducted on site and, with respect to the shutter, it is indicated by means of bubbling in a special tank. The extent of the leak on body side and/or shutter side is also measured on site by reading the pressure drop over time by suitably intercepting the measurement circuit, its volume and temperature being known. The results are presented in various ways (graphs, printouts, histograms) according to specific requirements; such tests normally make it possible to define the pressure-temperature diagrams that determine the operating fields of the valves.

4 - Liquid seal tests - These tests are performed both on industrial and sanitary components and are conducted on various test benches distinguished by various operating capacities. In particular:
- in the case of industrial component parts, the tests are conducted using water or other liquids upstream of the valve at a temperature between 18 and 150 °C and maximum pressures of 70 bar. The main purpose of these tests is random inspection and study of the sealing characteristics with respect to ageing and deterioration of the seals due to chemical absorption or reactivity. Inspections can be performed by keeping the valve in test conditions or returning it to lower pressures and/or temperatures up to ambient temperature with various gradients. To display the seal, proceed visually and pinpoint even the smallest leaks.
- in the case of tapware, tests are performed using water at a temperature between 15 and 70°C and a pressure between 1.1 and 15 bar. Seal checks on the various parts (shutter, deviator, body) are made using the same method described above for industrial component parts.

5 - Air tightness tests with air at medium-low pressure - Such tests, performed on industrial valves, are carried out on a special equipped test bench in order to determine tightness both globally and separately on the one side and the other of the shutter, through the pin and the body. The main aim of such tests is to check the tightness of production batches and, by means of suitable software, quantification is automatically made of the various leaks by reading over a period of time the pressure in the various circuits, after these have been suitably sectioned and whose volume and temperature is known. The test pressure reaches a maximum of 7 bar and temperature is ambient temperature. The results are presented as printouts.

6 - Vacuum seal tests - This consists in the test components undergoing a limit pressure of 0.2 bar (relative pressure -0.8) at ambient temperature. Such tests make it possible to evaluate global seal (shutter and body) by measuring the changes in pressure over time inside the suitably sectioned measurement circuit.

7 - Cyclic and fatigue tests - These tests too are carried out on both industrial and sanitary component parts, on different test benches with various operating capacities. In particular:
- in the case of the industrial component parts, the tests aim at evaluating both the seal of the shutter and, separately, of the pin (or leg) after a certain number of shutter opening and closing operations performed automatically inside a broad range of test variables which amply cover the requirements of the various standards. These cycles, which have operating times between 1 and 20 seconds and stop times between 1 and over 200 seconds, can be performed in atmosphere without mass flow through the component part or by allowing various fluids to flow through such as air at ambient temperature with a pressure upstream of the shutter between 1 and 7 bar and differential pressure (upstream-downstream of the shutter in closing phase) between 0 and 6 bar, or different liquids (normally water) with temperatures between 18 and 120°C, pressure upstream of the shutter between 1 and 40 bar, differential pressure between 0 and 38 bar. Tests are performed both at random and on production batches and consist in checking the seal according to procedures identical to those described at para. 3 after pre-established and consecutive numbers of operating cycles. The results are shown in the form of histograms and refer to average values obtained on a significant number of units, periodically updated. Also indicated are the confidence intervals delimited by the average of k best tests and k worse tests comprised between 2 and 5 in relation to the number of tested samples.
- in the case of the sanitary components, as laid down on the one hand by the need to verify and develop the product and on the other by European and non-European standards, the cyclic tests are extended not only to shutter operation but also to other parts such as diverters and swivel spouts. A series of duly equipped stations supplied with water at a temperature between 15 and 70°C and a pressure between 1.1 and 7 bar permit on-site verification of the seal of the aforementioned parts in accordance with procedures identical to those described in para. 4.

8 - Mixing tests - Such tests make it possible to determine the thermo-hydraulic characteristics of the mixers by reading the temperature of the water coming out of the component part being tested in relation to the position of the mixing part. The hot and cold water conduction circuits at the test bench are set so as to maintain a constant pressure between 1.1 and 8 bar during the entire mixing process (from only hot to only cold and vice versa). The temperatures of the water, maintained constant during the test, can be, for the cold water, between 15 and 20 °C, while for the hot water, between 30 and 90°C. The rotation speed of the mixing part is kept constant within a range between 0.02 and 0.35 rad/s. The results, considered as average values of a suitable number of samples, are shown in the form of diagrams.

9 - Mechanical tests - In this case the tested component parts (normally industrial) undergo simple bending, torsion and bending-torsion stresses. During the application of state of stress or during rest state, any deformations and leaks are determined. The bending and torsion stress loads can vary continuously up to 5000 Nm. The test is performed with constant stress load and seal is checked on site by pressurising the component with air using a method identical to that indicated at para. 3. The test can be performed both under stress or at rest, without performing any operation on the shutter or after a limited number - a few dozen - of opening and closing operations. Another test bench permits checking shock resistance: for this purpose the component part being tested undergoes the impact of a calibrated knocker weight, part of a pendulum machine. After the test, a check is carried out to see whether any breakages or deformation have occurred and, after placing the component part on one of the seal test benches, this is then inspected.