Troubleshooting pressure drop

Because of its small size and portabiHty, the hot-wire anemometer is ideally suited to measure gas velocities either continuously or on a troubleshooting basis in systems where excess pressure drop cannot be tolerated. Furnaces, smokestacks, electrostatic precipitators, and air ducts are typical areas of appHcation. Its fast response to velocity or temperature fluctuations in the surrounding gas makes it particularly useful in studying the turbulence characteristics and rapidity of mixing in gas streams. The constant current mode of operation has a wide frequency response and relatively lower noise level, provided a sufficiently small wire can be used. Where a more mgged wire is required, the constant temperature mode is employed because of its insensitivity to sensor heat capacity. In Hquids, hot-film sensors are employed instead of wires. The sensor consists of a thin metallic film mounted on the surface of a thermally and electrically insulated probe. 

Lieberman gives two rules of thumb for troubleshooting fractionators that could also be used as checks on a design. First, the pressure drops across a section of trays must not exceed 22% of the space between the tray decks, to avoid incipient flood. Mathematical , hold... 

For column analysis and troubleshooting it is important to have pressure drop measured with a DP cell. The differential pressure can also be used to control column traffic. A good way to do this would be to let the differential pressure control the heating medium to the reboiler. The largest application for differential pressure control is with packed columns where it is desirable to run at 80 to 100% of flood for best efficiency. 

This overview selectively describes only those principles of condensation that directly pertain to operation and troubleshooting of distillation condensers. This overview omits several considerations foremost for optimizing condenser pressure drop and heat transfer, and leaves their coverage to most standard heat transfer texts and review articles (e.g., 69, 187, 310, 319). Even the principles covered are discussed rather briefly the reader is referred to the cited references for in-depth treatment. 

Most of the troubleshooting assignments encountered in sulfur plants are related to pressur( pp. Plugged seal legs, disintegrated catalyst, carbon. deposits, and boiler leaks are the usual causes. Excessive pressure drop will result in an air deficiency or even blovyn seal legs. 

While X-ray pictures of tower internals easily detect most types of tray damage, this can be a cumbersome and expensive troubleshooting procedure. A simpler way to obtain almost the same information is by a pressure survey. Tower pressure drops of less than 1 in. of water per tray typically indicate tray damage, assuming a tray spacing of 24 in. 

The key tool in troubleshooting flash-zone pressure problems is a vacuum-tower pressure survey. The time to initiate this survey is just after start-up when the trays, demister, and ejector system are clean and in good condition. Pressures are best measured with a portable mercury-filled vacuum manometer. Using a vacuum pressure gauge will reduce the accuracy of observed pressure drops. Relying on permanently installed gauges for pressure drop data will not give reliable results. 

Normally reactors will be equipped with thermocouples within the catalyst bed and at the inlet and outlet. As a first step in troubleshooting, the temperature profiles should be plotted and checked for consistency with heat and material balance calculations. Likewise, pressure drop and pressure drop profiles should also be checked for consistency versus predictions for the actual conditions of the operation. Pretreatment of the catalyst such as sulfiding should be checked against normal or pilot plant procedures. 

Normalized salt passage is generally not used as the primary indicator of when to clean membranes. This is because normalized product flow and/or differential pressure drop (see below) will usually indicate problems with the membranes before product quality becomes an issue. However, normalized salt passage should be used in conjunction with NPF and pressure drop to diagnose and troubleshoot problems with the RO system. 

In the last few decades, since a successful introduction of fluidized bed technology, the instrumentation to monitor and quantify the fluidized bed operation has undergone several stages of development. In the most basic approach, the plant operation was controlled by measuring temperatures in selected places and the pressure drop along or simply across the bed. Clearly, these methods could only give superficial information, which could not be used in detailed flow analysis or plant troubleshooting. 

In this chapter we shall derive and present relationships or formulae that will allow us to predict a cyclone s cut-point diameter, grade-efficiency curve, overall or gross efficiency, and pressure drop on the basis of measurements taken on a geometrically similar cyclone. These formulae should also allow us to evaluate the performance of an operating cyclone and, if necessary, assist us in troubleshooting its design, mechanical condition, or mode of operation. 

The dispersed oil droplet size distribution may vary from point to point in a produced water system, and from one system to another. The size distribution is affected by interfacial tension, turbulence, temperature, system shearing (pumping, pressure drop across pipe fitting, etc.), and other factors. The droplet size distributions should be measured in the field when troubleshooting and/or upgrading systems, whenever possible. 

---