--- title: Tri-Sen Blog | PFD average description: PFD average | Topics related to turbomachinery controls --- [![26TRIS065-Tri-Sen 50 years logo-R2](https://blog.tri-sen.com/hs-fs/hubfs/Assets/26TRIS065-Tri-Sen%2050%20years%20logo-R2.png?width=1476&height=573&name=26TRIS065-Tri-Sen%2050%20years%20logo-R2.png "26TRIS065-Tri-Sen 50 years logo-R2")](https://tri-sen.com/) # Tri-Sen Blog [![](https://blog.tri-sen.com/hs-fs/hubfs/red%20alligator%20with%20text.png?width=690&name=red%20alligator%20with%20text.png) ](https://blog.tri-sen.com/proof_test_intervals) ## [Proof Test Intervals (PTI) as Proxy for Reliability](https://blog.tri-sen.com/proof_test_intervals) Posted by [Harry L. Cheddie, P.Eng.,CRE, CQE, CFSE](https://blog.tri-sen.com/author/harry-cheddie) on Nov 4, 2025 2:56:55 PM - [Tweet](https://twitter.com/share) It's been a minute, so to get back in the swing of things, we've asked  guest blogger, [Mr. Harry Cheddie, ](https://blog.tri-sen.com/author/harry-cheddie)P.Eng. CRE, CQE, CFSE; an industry-recognized expert in industrial safety, to comment on the [...] [Read More](https://blog.tri-sen.com/proof_test_intervals) 0 Comments [Click here to read/write comments](https://blog.tri-sen.com/proof_test_intervals#comments-listing) [ turbine safety ](https://blog.tri-sen.com/topic/turbine-safety) , [ safety systems ](https://blog.tri-sen.com/topic/safety-systems) , [ PFD average ](https://blog.tri-sen.com/topic/pfd-average) , [ proof test interval ](https://blog.tri-sen.com/topic/proof-test-interval) , [ PTI ](https://blog.tri-sen.com/topic/pti) , [ TSODS ](https://blog.tri-sen.com/topic/tsods) , [ overspeed detection ](https://blog.tri-sen.com/topic/overspeed-detection) [![](https://blog.tri-sen.com/hs-fs/hubfs/blog/trip%20block%20architecture/TetraSentry%20for%20blog%20r2.png?width=690&name=TetraSentry%20for%20blog%20r2.png) ](https://blog.tri-sen.com/hydraulic_trip_architecture) ## [Hydraulic trip Interface failure probabilities and spurious trip rates](https://blog.tri-sen.com/hydraulic_trip_architecture) Posted by [Harry L. Cheddie, P.Eng.,CRE, CQE, CFSE](https://blog.tri-sen.com/author/harry-cheddie) on Sep 1, 2020 9:30:00 AM - [Tweet](https://twitter.com/share) We're going to change it up a little this post with a guest blogger, [Mr. Harry Cheddie, ](https://blog.tri-sen.com/author/harry-cheddie)P.Eng. CRE, CQE, CFSE; an industry-recognized expert in industrial safety. [Read More](https://blog.tri-sen.com/hydraulic_trip_architecture) 1 Comment [Click here to read/write comments](https://blog.tri-sen.com/hydraulic_trip_architecture#comments-listing) [ turbine safety ](https://blog.tri-sen.com/topic/turbine-safety) , [ hydraulic trip ](https://blog.tri-sen.com/topic/hydraulic-trip) , [ MTTF ](https://blog.tri-sen.com/topic/mttf) , [ trip block ](https://blog.tri-sen.com/topic/trip-block) , [ safety systems ](https://blog.tri-sen.com/topic/safety-systems) , [ PFD average ](https://blog.tri-sen.com/topic/pfd-average) , [ API612 ](https://blog.tri-sen.com/topic/api612) [All posts](https://blog.tri-sen.com/all) ## The Tri-Sen Blog... About once every two weeks we'll discuss a turbomachinery controls topic that; we were either asked about recently, or a topic that we think you might be interested in learning more about.  Topics that are included or that will be: - Compressor Controls - Turbine Controls - Turbine Safety - Relevant API directives - General Industry Happenings ### Subscribe Here! ### Recent Posts ### Posts by Tag - [compressor control (10)](https://blog.tri-sen.com/tag/compressor-control) - [surge (9)](https://blog.tri-sen.com/tag/surge) - [recycle (4)](https://blog.tri-sen.com/tag/recycle) - [process protection (3)](https://blog.tri-sen.com/tag/process-protection) - [quench (3)](https://blog.tri-sen.com/tag/quench) - [refrigeration (3)](https://blog.tri-sen.com/tag/refrigeration) - ["Jim Jacoby (2)](https://blog.tri-sen.com/tag/jim-jacoby) - [PFD average (2)](https://blog.tri-sen.com/tag/pfd-average) - [PID (2)](https://blog.tri-sen.com/tag/pid) - [PID control (2)](https://blog.tri-sen.com/tag/pid-control) - [TMC (2)](https://blog.tri-sen.com/tag/tmc) - [process control (2)](https://blog.tri-sen.com/tag/process-control) - [safety systems (2)](https://blog.tri-sen.com/tag/safety-systems) - [turbine safety (2)](https://blog.tri-sen.com/tag/turbine-safety) - [turbomachinery controls (2)](https://blog.tri-sen.com/tag/turbomachinery-controls) - [API612 (1)](https://blog.tri-sen.com/tag/api612) - [API670 (1)](https://blog.tri-sen.com/tag/api670) - [MTTF (1)](https://blog.tri-sen.com/tag/mttf) - [PTI (1)](https://blog.tri-sen.com/tag/pti) - [TSODS (1)](https://blog.tri-sen.com/tag/tsods) - [axial compressor (1)](https://blog.tri-sen.com/tag/axial-compressor) - [compressor efficiency (1)](https://blog.tri-sen.com/tag/compressor-efficiency) - [hydraulic trip (1)](https://blog.tri-sen.com/tag/hydraulic-trip) - [incipient surge (1)](https://blog.tri-sen.com/tag/incipient-surge) - [overspeed detection (1)](https://blog.tri-sen.com/tag/overspeed-detection) - [polytropic (1)](https://blog.tri-sen.com/tag/polytropic) - [proof test interval (1)](https://blog.tri-sen.com/tag/proof-test-interval) - [stonewall (1)](https://blog.tri-sen.com/tag/stonewall) - [surge curve (1)](https://blog.tri-sen.com/tag/surge-curve) - [surge detection (1)](https://blog.tri-sen.com/tag/surge-detection) - [surge margin (1)](https://blog.tri-sen.com/tag/surge-margin) - [temperature control (1)](https://blog.tri-sen.com/tag/temperature-control) - [trip block (1)](https://blog.tri-sen.com/tag/trip-block) [See all](https://blog.tri-sen.com/tag/pfd-average#) ** HELP ###### HeadQuarters - North America  Engineering 109 Magellan Circle Webster, TX 77598 Tel:  +1-832-632-1211 Fax: +1 281-724-1226 ###### Netherlands Verlengde Zuiderloswal 4 Hilversum, NH 1216 BX Tel: [+31 88 011 9292](tel://+31%2088%20011%209292) ###### Singapore 56 Kallang Pudding Road #06-10 HH@Kallang  Singapore 349328 Tel: +65 6381 9188 Fax: +65 6381 9199 ### Search ** ### Stay in Touch - [** ** ](https://www.linkedin.com/company/tri-sen-systems-corporation/) [Privacy Policy](https://tri-sen.com/privacy) | [Terms and Conditions](https://tri-sen.com/terms) Copyright © 2019. Tri-Sen All rights reserved. Contact Us