Level of measurement –Level datasheets.Instrumentation engineers need the guide for level of measurement written in plain English to do their daily job. I’m wring this article to help myself and in hope help you to understand some level of measurement techniques in order to specify the right level instrument in oil and gas industries. Yet I’m not a native English Engineer and haven’t confident to explain clearly enough in this complicated subject. It’s impossible to deliver or cover everything in this article but for sure this is the information I have been struggling with in my job daily tasks and I bet you too. This is my website I wrote down my experience I’ve learned throughout the years. Please comment below to point out what I’ve missed or provide additional information.
Process service Pipe line number or vessel number on which cage or body is installed. Material or chamber and mounting flange. Connection size and location upper or lower. For float specify top or side of vessel connection. For displacer in a chamber specify upper then lower connection, such as side-side, side-bottom, flange size and rating NPT size. Case mounting: refers to position of case when viewing the front of the case relative to the chamber, the case is either to the left, right or top. Rotatable head: On displacer instruments specify if case is to be rotatable with respect to the chamber. This only applies if there is one or more side connections. Orientation: Orientation of control with respect to displacer cage. Cooling extension Specify float diameter or displacer length. Note that the probe should not contact the nozzle. If the nozzle diameter is less than recommended, the measuring range may be reduced. Insertion depth applied to ball floats. It is the mounting flange to the center of the ball. The displacer extension is measured from the face of the mounting flange to the top of the displacer. This dimension is required only for top of vessel mounted instruments. Displacer or Float material: include rod. Displacer spring: refer to MFR’s standard materials or special materials. Function: transmitter, controller. Output: Air pressure or electrical signal output of transmitter or controller. The most common output is 4-20 mA signal. Differential if controller on/off must specify differential adj. or fixed. State adjustable range or fixed amount. Output action: increase (direct action) or decrease (reverse action) Mounting: remote or integral. The transmitter can be mounted in nozzles by using an appropriate flange Enclosure class and NEMA number. Explosion proof may be sufficient for many devices. Electrical power or air supply: air pressure or voltage. If electronic, state whether ac or dc. Most devices will run on 12-24VDC but some devices that run on 110 or 220V. Specific gravities at operating temperature Operating and max pressure or vacuum Connection on chamber, give size. The chamber is also known as bridle, side pipe or cage. Specify gauge glass, if required. Contact form: SPST, SPDT ,etc Contact rating: give Volts, Amps. Level of measurement product examples Guided wave radar: Good for interface application. Interface applications based on dielectric differences between two fluids. Example oil over water… Should the instrument to be mount in a chamber? Make sure the size of connections needs to be large enough and distance between tank and chamber should be minimized. When mounting the transmitter the following guidelines should be considered:
Do not mount close to agitators The probe should be anchored to the tank bottom Avoid mounting near heating coils Do not install the transmitter in the center of the tank. Mounting in chamber or stilling well is recommended. Level of measurement InstallationLevel transmitter installation
Displacer length
Side side and side bottom chambers
Pressure instruments datasheet |
