Closed drain header

Connections to the closed drain header may be justified for large volume light ends pumps. 

Refinery preference may exceed these requirements. In such cases, additional 25 mm connections from equipment to the closed drain header may be installed (20 mm connections are generally considered adequate for pumps). 

Vessels with liquid inventories > 0.1 m Closed drain header Closed drain header Sewer... 

Compressor casing, cylinder and knockout bottle drains Closed drain header -- -... 

Closed Drain Header Systems for Flammable Liquids... 

Closed drain headers are normally provided for safe drainage of equipment containing severely toxic, corrosive, pollutant or high cost chemicals (e.g., phenol, sulfuric acid, monoethanolamine, sulfur dioxide, catacarb) where there is an appreciable inventory in a number of processing vessels in a plant. The header should be at least 50 mm in diameter, and should be tied into the major vessels and equipment with 25 mm minimum size connections (20 mm is considered adequate for pumps). The header may be routed to a gravity drain drum (with recovery to the process by pump or gas pressurization), or to a pumpout pump returning to the process, or in the case of sulfuric acid, to an acid blowdown drum. 

Usually, the closed liquid drain header is run as a separate line to the drum and provided with a high level cut-off valve with local manual reset. In some cases the closed drain system is segregated into a number of subheaders, as described earlier. Hydrocarbon liquids may be bypassed around the drum through a connection from the closed drain header directly to the pumpout pump suction, provided that the liquid can be routed to a safe disposal location, considering its vapor pressure and temperature. Emergency liquid pulldown connections, if provided, are routed to the blowdown drum via the closed drain header. 

An LH(CO)A is provided at a low level, actuating a cut-off valve in the closed drain header. Holdup below this LH(CO)A is the closed drainage requirement. 

Liquid hydrocarbons accumulated in non-condensible blowdown drums, originating from safety valves, closed drain headers, knockout drum drainage, etc. Facilities are normally provided at the drum for weathering volatile liquids and cooling hot liquids before disposal. 

The shutter section of each beam port is drained to a common drain header. The header drains to the hold tank floor drain through a valve located in the pit beside the demineralizer. This valve is kept closed for Ar-41 control. The vent line from each beam port goes through a check valve and stop valve with bypass flow control and then to the BP TC vent system. Provision is made for leak checking of the beam ports to assure an air-tight seal. 

Leaky valves are also a cause of erosion. Most turbine erosion-corrosion problems come from damage that takes place when the unit is not running. A shght steam leak into the turbine will let the steam condense inside the turbine, and salt from the boiler water will settle on the inside surfaces and cause pitting, even of the stainless blading. There must be two valves with a drain between them, i.e., a block valve on the header and an open drain in the line before it reaches the closed trip-throttle valve. 

When hazardous chemicals are present, the column is often initially steamed to the disposal header (e.g., flare header). If steaming is suflicient to clear these chemicals, the vents and drains to the disposal header are then closed, and the atmospheric vents and drains are opened as steaming progresses. 

Isolation valves in the purification system inlet and outlet lines are provided for maintenance purposes. The valves also allow drainage of the HTS coolant to just above the elevation of the headers without the need to drain the purification system. These valves close automatically in the event of LOCA. 

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