● GENERAL

Underground slab gate valve is used to cut off medium in buried pipelines transportation, it can be buried in underground directly only required to build a small valve room on the valve cover (see drawing 5), in order to operate and maintain conveniently in all directions above ground. 

● FEATURES OF UNDERGROUND SLAB GATE VALVE

▲  Reliable sealing, lower flow resistance coefficient, good anti-rust performance.

▲  It can be installed with professional parts and special design construction in order to install or unload the parts on line and convenient to keep the maintenance.

▲  Separation between inner cavity of body and medium bore, keeps clean without deposits.

▲  With indicating position device.

▲  Optional the relief device.

▲  Optional actuators: Handwheel, gear box, electrical actuator.

It’s widely used to connect the buried pipelines in city coal gas, natural gas and liquefied petroleum gas (LPG), above ground station and long-distance transportation of pipelines after installed connection flange and handwheel.

● PERFORMANCE

● STANDARDS (EXCEPT FOR RELATED INTERNATIONAL STANDARDS)

JB/T5298      Steel slab gate valve in pipeline

Q/35X21       Non-rising slab gate valve in buried pipeline

GB/T12234    Bolted cover steel gate valve in Oil & Gas

GB/T12221    Metal valve/face to face length                 

GB/T12229    General valve/casting steel technical condition

GB/T13927    General valve/pressure test

GB/T12224    General steel gate valve

JB/T79.1～94  Casting steel pipe flange 

● MATERIALS OF MAIN COMPONENTS 

● VALVE SEALINGS

 1.    Non-rising stem gate valve with single slab and guiding hole is double floating seats construction, and the sealings are soft sealing, metal sealing and sealing injection sealant.

2.    Extending seat keeps the separation between the bore and cavity during opening or closing status, the deposits of the bore will not enter into the cavity, the slab can move in the cavity freely even using for long time.

 ● ANTI-CORROSION IN OUTER AND INNER SURFACE

Non-machining sections are under shot blast, inner surface is painted with varnish like epoxy resin in 2~3 layers of coatings. Except the welding ends, outer surface is painted with epoxy anti-rust red primer and then with insulated heavy corrosion coating. At Present, XHDAC series heavy corrosion coating was used in our factory, and also we use Chlorosulfonated Polyethylene Rubber (CPR) which is recognized by anti-corrosion field to change the performance of the epoxy resin, CPR owns much advantage, such as firm adhesion, good flexibility, impact resistance and well insulation, and waterproof, oilproof, anti-acid, alkali and salt, as well with good stability of freezing and thawing, and wide temperature from -60℃ to120℃.

         Note: Underground slab gate valves made by our company are Chinese patent products.Patent No.: 95242080.5.

 ● POSITION INDICATING DEVICE

In order to observe the opening or closing status of the valve, the position indicating device is designed on the top of the valve with stainless steel parts. 

● SEALANT INJECTION

Sealant is injected from outside of body to seat ring to strengthen the auxiliary sealing of the valve, it can be sure the zero leakage even if the valve is used for long time.

● RELIEF DEVICE

In order to test the pressure of the medium and obviate the excess pressure in the pipe, the relief device (See drawing 3) can be installed; there is a small ball valve in the top of the relief pipe.

Exception for the special requirement from customers, the size of the relief pipe is 1/2” when valve size is DN＜200, and the screw thread size of the pipe is Rc1/2; The size of the relief pipe is 3/4” when the valve size is DN≥200, and the screw thread size of the pipe is Rc1/2.

● DRAIN HOLE

From the design of Holy valve, there is a good device to prevent the stagnant water, namely there are two balanced drainage holes (hole screw thread in Rc1/2) in the cover. When working, you need to unscrew the two drain plugs, put a pipeline in the hole and draw out the stagnant water with a pump. Meanwhile you may put a pipeline at the bottom of the water in one hole, and in another hole with gas pressure to draw out the water. 

● ON-LINE MAINTENANCE

Using the special professional tools, customers can dis-assemble, assemble, and change the defective inner parts on line conveniently, keep the maintenance for the valves.