1. 1

2.  Introduction  Categories/Kinds of Pressure Sensing Accessories  Purpose  References 2

3.  Definition  To avoid excessive maintenance problems and damage of instruments, special accessories provide a safe and reliable working of instrument as well as the process  Working Principle 3

4.  Valve Manifolds  Bleed (Vent) Fittings  Pressure Pulsation Damping  Fill Fluid Mechanism  Remote and Chemical Seals 4

5. Three Valve Manifold A fourth valve called a “bleed” valve used to vent trapped fluid pressure to atmosphere 5

6. Two block valves are left open to allow process fluid pressure to reach the transmitter. The equalizing valve is left tightly shut so no fluid can pass between the “high” and “low” pressure sides 6

7.  For normal operation and maintenance  Never open while both block valves 7

8. Close-up views of a bleed fitting both assembled (left) and with the plug fully extracted from the fitting (right) Bleed fittings installed in two different ways 8

9. An oil-filled pressure gauge Snubber 9

10. 10

11.  Fill the pressure sensor mechanism with a clean liquid (called a fill fluid)  Transfer pressure from the process fluid to the fill fluid 11

12. 12

13. Thin metal isolating diaphragm Chemical Seal Diaphragm 13

14. Capillary tube with coiled metal (“armor”) sheath Close-up view of the sealing diaphragm with corrugated design 14

15. Pigtail Siphons Transmitter with Pigtail Siphons 15

16.  Singh S.K., “Industrial Instrumentation and Control”, Tata McGraw Hill Publishing Company Limited New Delhi, Edition Ist, Chapter 12, Page 393-397  Tony R. Kuphaldt, Jan11, 2009, lessons in industrial instrumentation, Creative Commons, page 397-425  http://iamechatronics.com/notes/general- engineering http://iamechatronics.com/notes/general- engineering  Dr. Shahid Naveed, Dr. Ing Naveed Ramzan & Ms. Sana Yousuf 2011, Industrial instrumentation, First Edition, Allied Book company, Pages 77-78 16