Head block valves

The head losses between the working reservoir and the exit of the reactor tank are due almost entirely to the velocity head and friction losses across the active and beryHium sections, with relatively small losses contributed by the conveying pipe line There are block valves and a flow control valve in the inlet line to the reactor, but there are no obstructions inthepipe line from the reactor to the seal tank. 

Pressure measurement for piping and vessels is achieved by the installation of dial indicators or by distributed control systems. The piping and vessels are tapped at the required location and furnished with a 3/4-in threaded or flanged conneaion and a block valve. Tbe dial indicator is screwed into the block ralve if a remote readout system is required, the valve becomes the sensing connection. Like the thermocouple, the dial can be either fixed or swivel-headed to fecilitate readout. A dual local indicator and transmitter s) em needs only one tapping point. Exhibit 14-9 depicts a typical pressure gauge and a dual-pressure system hookup. 

In the parison extrusion phase, the extruder die block valve is opened and the screw performs the action of a ram by moving forward in the axial direction without rotating. This forces the accumulated melt at the forward end of the screw through the parison head, where it is extruded at a relatively high flow rate. In practice, the flow rate is limited by the onset of shear phenomena such as sharkskin and melt fracture. 

Most line has pipe fittings, such as elbows, tees, reducers. It also has block valves, check valves, or instruments, such as control valve and oriflce flow meter. They will cause pressure drop in tine. In this section, we will discuss how to calculate pressure drop thru pipe fltting, block valve, check valve, and control valve using loss coefficient, K, since their pressure drops are required in hydraulic loop pressure profile calculation. Darby s 3-K. method will be used to calculate these pressure drops [ 12]. It is better than two K method or equivalent line length methods. Fittings and valves pressure drop (in terms of pressure head, H) is calculated by flillowing equation, ... 

A toluene surge drum has capacity 500 gal and is normally operated 60% full at 100°E under 300psig of hydrogen in the head space using a level-controlled outflow The normal flow rate into the vessel is 30,000 Ib/h. Determine the vessel dimensions if the vessel is vertically mounted. Evaluate the relief loads for the blocked outflow and external fire cases and hence determine the relief valve size. 

Lower pressure than anticipated is observed due to leaks, insufficient flow from the pump, air bubbles, and worn pump seals. Fluctuating pressure is attributed to air trapped in the pump, or leaking pump check valves or seals. Higher pressure than anticipated is due to blocked flow lines, particulate build up at the head of the column, or buffer salt precipitation. To locate blockage, components should be systematically disconnected. 

Blocked or leaky check valves can probably be fixed by sonicating them. Perhaps a number of solvents need to be tried, e.g. water with detergent, tetrahydrofuran or dichloromethane. Some valves fall apart when they are removed from the pump head (beware of loss of the ball ), some can be opened and some are a unit which should not be opened. With the first two designs the ball can be replaced, maybe also the seat, when these parts are scratched and do not seal well any longer. The other types of check valves must be replaced totally if they do not work properly and if a treatment with ultrasonics does not help. 

Here is an example. An ASP flood was initiated in the N-IDX block in Daqing on March 15, 1997. A pump malfunction occurred with a scale thickness of 1 cm over the wellbore by September 23, 1998. By the end of 1999, serious scale problems were observed in surface facilities, such as the oil-water separation system and the produced water disposal system. Scale usually occurred on pipe walls and in valves, pump heads, vane wheels, and flow meters. In another case, some scale samples from Well Zl-35 looked white, and the scale thickness was 0.5 to 1.0 cm. The scale in the delivery pipes of Zl-35 reached about 0.3 cm (Wang et al., 2004b). 

---