Troubleshoot Diaphragm Valves Used In Dust Collector Systems

Diaphragm Valves operated by a pilot solenoid valve are 2- way normally . These valves are designed for extremely fast opening / closing and high flow rates.

The body and cover are of die cast aluminum alloy with special anticorrosive coating. The solenoid valve is integrally mounted on the diaphragm valve and has encapsulated coil ( Class F insulation ) with a water proof ( IP - 65 ) plug - on connector.

Diaphragm Valve Operation:

The diaphragm divides the valve into an upper chamber and a lower chamber. The air inlet leads into lower chamber from where it passes into the outlet when the diaphragm, lifts. The diaphragm has bleed hole through which the high pressure inlet air bleeds into and fills up the upper chamber, crating the same pressure on both sides of the diaphragm. The pressure in the upper chamber acts on a lesser ( less outlet area ) area of the diaphragm. This keeps the diaphragm pressed down on the outlet port, closing it.

The upper chamber is connected to the atmosphere through the air passage in the pilot base. The plunger in "normal" conditions keeps the air passage closed, maintains the pressure in the upper chamber and hence the diaphragm valve closed. When electric supply is given to the solenoid coil, the plunger lifts within the core tube and the compressed air in the upper chamber exhausts quickly to the atmosphere. Because the exhaust air passage has a higher flow rate than the bleed hole on diaphragm, the pressure in the upper chamber falls suddenly. The pressure in the lower chamber then lifts the diaphragm, causing the compressed air to flow from inlet through outlet. When the solenoid is de-energised, the plunger closed the air passage resulting resulting in the diaphragm closing the valve outlet.

Disassembly And Reassembly of Diaphragm Valve:

Depressurise Valve, Turn Off Electric Supply and Proceed as Per Steps Below :

1).Loosen plug screw and remove PLUG CONNECTOR (1) from COIL (2).

2).Remove coil retaining NUT (4) and slip COIL (2) off CORE TUBE (5)

3).Loosen core sleeve and remove CORE TUBE (5) from PILOT BASE (10), The PLUNGER (7) AND SPRING (6) come loose.

4).Loosen screw holding PILOT BASE (9) to valve COVER (12) and remove PLOT BASE (9). The 2nd rubber O-RING (8) comes loose.

5).Loosen COVER SCREWS (13) and remove COVER (12) and DIAPHRAGM (15) from valve BODY (14). [The valves model 114 - 116 - 120 - 124 with larger capacity have two stages (two diaphragms (15-17) to allow a standard small pilot solenoid valve to control them.

6).Loosen and remove screws (13-19) both from the PILOT CAP (12) of the smaller SECOND STAGE DIAPHRAGM (17) and from the COVER (18) of the MAIN DIAPHRAGM (15)].

7).All parts are now accessible for cleaning or replacement, Clean the air passage in PILOT BASE (9) . Replace worn or damaged parts.

8).Reassemble in reverse order paying careful attention to exploded view.

9).Clean the bleed hole and replace diaphragm (15) with the steel plate up facing the cover.

10).Tighten the COVER SCREWS (13) to 10 + / - Nm. And the COVER SCREWS (19) of the MAIN DIAPHRAGM (15) to 18 + / - Nm. Tighten the PILOT BASE SCREWS criss-cross, Tighten the plug connector screw.

11).After reassembly, operate the valve a few times to be sure of proper opening and closing.