TILI Automation

 Some differential pressure transmitters are equipped with 5 way valve manifolds. These valve networks allow for blocking, equalizing, and bleeding of the transmitter’s two pressure ports, the valves being arranged in this pattern: Differential Pressure Transmitter 5 Way Manifold Valve Shown using standard P&ID symbols – instrumentation equivalent of an electrical schematic diagram – the transmitter and manifold arrangement looks like this: Identify the normal, operating valve positions (open/closed) for a five-valve manifold. Describe the proper sequence of manifold valve operation to successfully prepare the transmitter for removal from the process.   Why do you think we have such things as 5-valve manifolds? What can be done with this manifold that cannot be done with a three-valve manifold? Answer: Normal valve positions: Both block valves open. Both equalizing valves closed. Vent valve closed. Removing differential pressure transmitter from service: Close one block valv...

 In connecting a pressure transmitter or other pressure-measuring instrument to a process pipe or vessel, there must be some means of “disconnecting” the instrument from the pressurized process so that it may be calibrated or removed safely without depressurizing the entire process. Usually, this feature is provided in the form of an instrument “manifold,” consisting of one or more valves between the instrument and the process pipe or vessel. Pressure Gauge with Block and Bleed Valves Take this pressure gauge installation, for example: Two small valves connect the process vessel to the pressure gauge through a tee fitting, one called the “block” and the other called the “bleed.” In normal operation, the “block” valve remains in the open position and the “bleed” valve remains in the closed position. Suppose you wished to remove this pressure gauge from the process vessel and take it to the instrument shop for re-calibration. In what sequence would you operate the “block” and “bleed”...

 On processes where the fluid in question is especially dangerous, “double block and bleed” valve manifolds are often used to isolate pressure measuring instruments (like pressure gauge, pressure transmitters, etc) from the process. Double Block and Bleed Valves Describe the proper procedure for block and bleed valve opening/closing when removing and replacing an instrument connected to a process through such a manifold. Answer: Removing the gauge from service: Close the “block” valve closest to the process. Open the “bleed” valve. Monitor the instrument’s pressure indication, to make sure it is changing to register atmospheric pressure. This tells you that the “bleeding” is successful. Close the “block” valve closest to the instrument. Close the “bleed” valve. Place lock-out tags on all three valve handles to notify operators and technicians of the instrument’s removal and pending return. Remove the gauge from the piping or tubing. Assuming the process fluid is especially dangerous...

 European standard EN 837 and American standard ASME B40.100 talk about pressure gauges. Here we are going to review the information written on dial pressure gauges according to EN 837. Pressure Gauge Dial In the picture below more than 11 pieces of information have been shown. Let’s look at them. Number 1: S circled sign shows that this gauge is “Safely designed” in order to protect it in case of overpressure. Blow-out device, Blow-out back, baffle wall and laminated safety glass are some designs that in some cases must be provided. Number 2: En 837 standard has 3 parts: Part one deals with Bourdon tube pressure gauges, Part two talks about Selection and installation, Part three is about Diaphragm and capsule pressure gauges. In this picture, it has been written EN 837-1. That means the measurement element of the gauge here is a Bourdon tube. Something that is accordant with the number 3. Number 3: symbols of the pressure sensing element based on the table below: Number 4: If the ...

 Here we shall see recommended practices for the protection of the instrument from harsh process conditions. In this article, we shall learn about Diaphragm seal and liquid seal methods to protect the instrument. A seal can be a mechanical isolator between process and instrument or it can be part of piping filled with fluid. These protection methods are generally used with pressure transmitters, DP transmitters, pressure gauges, and piping that connects these instruments to the process. Diaphragm Seal Diaphragm seals are used in the following cases. When process fluid must be isolated Slurry services Toxic/corrosive services High-temperature fluid. When fluid has the tendency to clog or freeze in ambient temperatures. Pressure-gauge and pressure-switch seals (see Figure below) usually consist of a diaphragm and a diaphragm holder into which the instrument is connected, a seal fluid is enclosed in the chamber between the diaphragm and the gauge. The holder, diaphragm, and gasket mat...

 The following are the Pressure Gauge Accessories: Snubber Pigtail Syphon U Syphon Gauge saver Gauge Adaptor Gauge Union Pressure Gauge Accessories Snubber The Snubber (Pulsation Dampener) protects the pressure instruments from pressure pulsations / rapid pressure fluctuation. Ideal for instruments which undergo severe pressure pulsations like those located at the pump discharge. Available in materials like CS, SS304, SS316, Monel, etc. The standard connection is 1/2” NPT(F) x 1/2” NPT(M) (other connection can be available as per requirement) Syphon The Syphons are used to protect pressure instruments from the high temperature of the process fluid. It helps to reduce the service temperature so that the pressure instrument is exposed to a lower temperature. Generally offered in 1/2” inch, 40 or 80 sizes (other sizes also can be available). The standard connection is ½” NPT(F) x 1/2” NPT(M). Plain end suitable for Butt-welding can also be offered. Available in material like CS (A106)...

Practical Questions Pressure Measurement Identify the Pressure Gauge Error An operator claims pressure gauge PG-108 is defective and needs to be replaced. This pressure gauge registers 50 PSI, while pressure controller PIC-33 and pressure recorder PR-33 both register the pressure as being equal to setpoint: 43 PSI. Before replacing this pressure gauge, however, you decide to do some diagnostic thinking to see if there might be other causes for the abnormally high reading at PG-108. The first thing you check is the position of control valve PV-33a, and you find its stem position to be at 35% open. Identify the Pressure Gauge Error Identify the likelihood of each specified fault in this process. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for all measurements and symptoms in this process. Identify the below faults are possible or impossible? PG-108 calibration error PT-33 calibration error PIC-33 left in ...

 Learn the testing procedure for the field instruments impulse line, pipe, or tubing pressure leak test. Test Pressure Equipment Test gauge, Hydro manual pump, Hose Guage used shall be calibrated +/- 1% accuracy and shall have valid calibrate stickers Test Medium Clean water Air Testing Pressure The test pressure equipment shall be 1.5 times of the max. working pressure Incase of pneumatic test, test pressure shall be 1.1 times Checks To Be Carried Out Before Starting Pressure Test Ensure that ferrules are correctly installed Impulse lines shall be supported and slope maintained properly Ensure that instrument connected is isolated Barricade the area for hydro test access shall restrict to authorized persons only Use all safety PPE’s ( Personal Protective Equipments) Impulse Line Testing Procedure After verifying the completeness of all above applicable records line shall be cleared for the pressure test Avoid air pocket for mention vents at high points shall be left open and not c...

 Many industrial pressure sensing elements, especially diaphragms and bellows, are equipped with stops to limit the physical travel of the sensing element: What important purpose is served by a stop in a pressure measuring instrument? Stop in Pressure Measuring Instrument A stop prevents the pressure element from being excessively strained by overpressure. Ultimately, it helps to prevent rupture of the element in the case of accidental overpressure. When a pressure element flexes so far that it comes to rest against a stop, the stop begins to provide the opposition force to the force generated by the applied pressure, so the element does not have to strain further. Ideally, the stop(s) in an instrument will be set up to limit the element’s travel enough so that its elastic limit is never exceeded. However, the presence of a stop does not guarantee that the instrument will remain within calibration specifications after exposure to an overpressure! Stops are important even in force-b...