## How is proof test coverage calculated?

Automatic diagnostics are poor and detect only 10 FITS. That means Lambda DD is 10 FITS and Lambda DU is 90 FITS. Imagine that a manual proof test can be done during operation that can detect 72 of these 90 FITS. The proof test coverage is 72/90 = 80%.

### What is the purpose of proof test and what is proof test coverage?

What is Proof Test Coverage? Proof Test Coverage (PTC) is the term given to the percentage of dangerous undetected failures that are exposed by a defined proof test procedure. For example, a PTC of 95% tells us that 95% of all possible undetected failures will be revealed during the proof test.

#### What is proof test interval?

Proof testing is defined in IEC 61508 as a ‘Periodic test performed to detect dangerous hidden failures in a safety-related system so that, if necessary, a repair can restore the system to an “as new” condition or as close as practical to this condition’.

**What is proof test of valve?**

A proof test is a periodic test per- formed on SIS sensors, logic solvers and final elements — such as automated valves — to discover hidden failures. These failures, if not corrected or removed, may impair the ability of the SIS to take the process to its safe state when an abnormal process condi- tion is detected.

**What is a proof round?**

A “proof round” is an ammunition assembly designed to be used in proof testing; this can use a fixed cartridge, a semi-fixed cartridge, or separately loaded projectile, charge and primer. A “proof shot” is a special projectile used in a proof round or other projectile weapons, electromagnetic guns for example.

## What is sis proof test?

The proof testing of SIS is an integral component of the management of functional safety. Its purpose is to confirm the continued operation of the required safety instrumented function and to contribute to the maintenance of the required safety integrity level of the safety function.

### What is a SIF test?

A safety instrumented system (SIS) can be one or more safety instrumented functions (SIF). A SIF is designed to prevent or mitigate a hazardous event by taking a process to a tolerable risk level. A SIF is composed of a combination of logic solver(s), sensor(s), and final element(s).

#### What is SIF safety?

Safety Instrumented Function – A set of equipment intended to reduce the risk due to a specific hazard (a safety loop). Its ability to detect, decide and act is designated by the safety integrity level (SIL) of the function. …

**What is a SIS proof?**

**What are the parameters of proof test coverage?**

This parameter is represented as PTC (“Proof Test Coverage”) or Cpt, and what it quantifies is the percentage of “Dangerous Undetected Failures” that we are able to detect during Proof Testing.

## What is the PTC of a proof test?

PTC (also called C PT) is defined as the percentage of dangerous undetected random failures that are revealed by regular manual proof testing (IEC 61508-6, B3.2.5). This number clearly depends on the type and extent of proof testing carried out.

### How many fits are left to detect by PTC?

So there are 10 FITs left to detect by PTC (if using the same analysis per previous example).

#### What kind of proof test is used in PSC?

The ExSILentia SILver module, used by PSC as a SIF design and verification tool, already allows for varying proof test intervals for each section of the safety loop.