Van giảm áp Model 218

Pilot Pressure Relief Valve Model No. 218 has been designed with great care and precision to provide full rated flow through the valve. The pilot mechanism utilizes dead weight loading and can be adjusted easily to any pressure setting required by the system. The stem assembly is stainless steel and the pallet and seats are aluminum alloy to withstand corrosion and assure long, efficient service.

These valves are designed to maintain constant upstream pressure, and also to provide positive shut-off when upstream pressure is reduced. It is basically a globe type valve with a dead weight loaded diaphragm type pilot.

Model No.218 valves should be installed in the waste gas line upstream from the waste gas burner. By maintaining pre-determined back pressure throughout the system only the surplus gas is burned in the waste gas burner. These valves are usually installed next to a Flame Trap Model 220 (see separate data sheet for the Flame Trap and the combined Pilot Pressure Relief Valve and Flame Trap Assembly).

The pressure adjustments on the Model 218 pilot pressure relief valve are made by adding or removing weights on the diaphragm (Item No. 14). The unit is designed to regulate pressure from 2 1/2" to 12" of water pressure by 1/4" increments. All working parts of the valve are protected from the weather and accidental damage, but are readily accessible for inspection and maintenance. If mounted outdoors, unit should be protected from freezing.

(See Drawing F-16015-A)

The pilot pressure relief valve, Model No. 218, is shipped as an integral fully assembled unit with the weight discs included in the shipment in a separate package. The valve is ready for installation in the waste gas line upon its receipt and should be installed as shown on drawing F-16015-A. The housing is provided with standard ASA 125 lb. flat face flanges and can be installed in the gas line with standard bolts and gaskets (furnished from purchaser's stores). An arrow on the body indicates the direction of flow through the valve. The valve must be installed with the arrow pointing in the direction of flow through the line.

After the valve has been installed in the waste gas line, the 3/8" NPT pipe plug (Item No. 21), used only during shipment, should be removed and discarded and, to insure proper operation of the valve, this 3/8" NPT outlet in the side of the diaphragm cover should be vented to the atmosphere.

The 1/2" NPT opening to the underside of the diaphragm should be connected with piping to the upstream side of the sediment and drip trap. A Model No. 315 Flame Check should be included in this line.

After installation of the piping has been completed the valve requires only the proper loading on the pilot diaphragm for the pressure under which the system is to operate. This should be determined after discussion with the consulting engineers working on the project.

The Pilot Relief Valve will operate at about 2 1/2" of water without any additional weights. Each additional thin weight added to the top of the diaphragm will ad 1/4" of water pressure to the setting.

For example: if 7" of waste gas pressure is required, 18 additional weights will be needed. After the proper pressure setting has been made the pilot cover plate (Item No. 20) should be replaced on the pilot housing. The unit is then ready to operate.

(See Drawing F-16012-D)

Model No. 218 Pilot Pressure Relief Valves require very little maintenance. Practically the only difficulty that could be encountered would be failure of the flexible diaphragm (Item No. 14F). If this should occur the valve would close, stopping the flow of gas through the line, and no gas would be available to the waste gas burner. Proceed as follows to make the valve operate again:

Close the valve in the main line ahead of the pilot relief valve.

Remove the bolts and take off the pilot cover plate (Item No. 20).

Remove the nut (Item No. 16) and all the weights (Item No. 19).

Remove the bolts and take off the pilot cover (Item No. 22).

Slide the spacer stem (Item No. 18) and the diaphragm disc (Item No. 15) off the main valve spindle (Item No. 5).

Remove the diaphragm (Item No. 14) and replace it with a new diaphragm.

Re-assemble the unit in reverse order.

Open the valve in the main line so flow of gas through the system can be resumed.

Drawings

1. Pilot Relief Valve
2. Front View