Simple. Intuitive. Straightforward.

A suite of tools to facilitate management of Safety
Instrumented Systems.

Request a free demo


Cloud Based

Our cloud based platform allows you access and maintain your system from any web-enabled device.

Lifecycle Engineering

SISSuiteTM covers the entire Safety Life Cycle from design to decommissioning.


Easily create SRS documents with our pre-built templates.

Location Management

Manage your SIFs using a familiar heirachy. Site - Plant - SIS - SIF.


Our Process Safety Time application allows a rigorous evaluation of PST in substantiation of the Safety Requirements Specification.

SIL Check

SILCheck uses the Reliability Block Diagram (RBD) approach for checking SIL verification.

Advanced LOPA Module

Our easy to use LOPA tool allows you to assign your calibrated tolerable risk targets and quickly dermine a required SIL level and RRF.

Periodic PFD Review

Through SIFED, element failures and population changes can be recorded and reviewed. Any change in failure rate will be automatically propagated into ‘downstream’ records.

Competency Register

Users can be assigned competence at one of four levels. Only users identified as 'Practioner' or 'Expert' are permitted to check or approve records.

Asset Management

Our SIFED (SIF Element Database) & Tag Management applications work together to manage your assets and allow you to reuse your element data throughout SISSuiteTM.

Version Control

Version control is built into to SISSuiteTM and provides each record with a version number which is automatically incremented whenever a user edits a record.

Document Management

Easily manage all your SIF SRS & Proof Test references from one place. Our 'Generic Document' feature is a great way to leverage our Version Control system on any document you wish to build.

Prior-Use Evaluation Tool

Facilitates evaluation of installed legacy devices or new devices procured on the basis of site experience,

Leading Indicator Analysis

Provides LI measures for each SIF in support of FSA4

HazOp Module

Provides tailored parameter and guideword listings, together with optional Hazan fields, action tracking and a full pdf report.

FS Management Planning Module

Provides a comprehensive template with full automatic version control.

Process Safety Models: Cheese, Chains or Cords?

The Swiss cheese model is often employed in representing process safety. The individual slices represent different defences or barriers, and the holes represent the potential for a barrier to fail. If the holes should align, all barriers will fail and the hazard consequence will be realised. Weaker barriers have bigger and/or more holes than stronger barriers. It usefully captures the idea of layers of protection, and of these being invoked in the order corresponding with the layer sequencing, but it relies upon the abstract notion of ‘dynamic’ holes that vary in size and location, and in illustration it requires a perspective drawing. It is an appealing illustration that immediately conveys the primary concern of multiple concurrent failures; it is perhaps less good at representing the integrated nature of process safety. Read More

PST & SIF Response

LOPA Considerations

Why SISSuite



Don’t make life harder than it needs to be!

SISSuiteTM is ‘right-sized’ for the job. It doesn’t overwhelm you with ‘bloatware’ calculation options and complications you simply don’t need. Data entry is straightforward and intuitive. (‘Refinements’ that use sparse data that is difficult to validate, or data that is highly uncertain, offer only the appearance of added value.)

There is more to compliance than PFD calculation!

SISSuiteTM performs a compliance check in terms of PFD, HFT and Systematic Capability against either IEC 61508 2nd Ed. OR IEC 61511 2nd Ed. Evaluations are straightforwardly implemented using the Reliability Block Diagram approach and the formulae described in IEC 61508 Part 6.

Functional safety is not just for Xmas; it’s for life!

SISSuiteTM facilitates monitoring of on-going performance and calculates prevailing PFD as assets age. Assets operating beyond their useful life are flagged. SIFs with a PFD that has grown significantly are also flagged. The toolset supports Functional Safety Assessment at Stage 4 (Operation & Maintenance), helping you demonstrate proper on-going management of your SIFs.

Functional safety records need to be controlled!

SISSuiteTM provides full automatic version control of all critical records. Originator, checker and approver are all tracked with date stamps. Records are automatically ‘revved up’ when edits are made and as they progress through draft-check-approval.

Functional safety competence is now mandatory!

SISSuiteTM has an integrated competency register; only personnel with appropriate competence levels are allowed to check/approve records.

Process Safety Time specification needs due diligence!

How do you determine the process safety time? SISSuiteTM has an integrated Process Safety Time calculator under full version control.

There is more to LOPA than identifying layers of protection!

SISSuiteTM offers an advanced LOPA tool which allows identification of a defence matrix, when the defences are invoked relative to the SIF, the conditional modifiers and the enabling conditions. Identifies target SIL, demand mode and PFD/PFH as appropriate.

Functional safety requires team collaboration!

SISSuiteTM allows remote collaboration. The originator may be on one site (or continent) and the checker or approver on another. All the account records are available to the authorised users from any web enabled device.

Who we are


SISSuite™ has been developed by combining the implementation skills of the HTS Engineering Group Ltd. with the consulting experience and the expertise of Time Domain Solutions Ltd. (The consulting engineering practice run by Harvey T. Dearden.)

SISSuite™ was specifically developed to provide a practicable tool set to help duty holders discharge their obligations in the management of functional safety. Both parties have been independently and collaboratively implementing and advising on IEC 61508/61511 compliant engineering solutions within the Process and Manufacturing industries.

SISSuite™ draws upon these experiences and was developed with a distinct focus on practicability to provide a ‘one stop shop’ for implementing and managing your safety instrumented systems.

Harvey T Dearden

  • InstMC Registered Functional Safety Engineer
  • IChemE Professional Process Safety Engineer


Harvey has worked in the process industry sector for over 35 years; he has operated his own consulting engineering practice since 2003. He is known to many through his involvement with the professional engineering institutions and his numerous papers and articles.

Harvey’s many articles, SISSuite™ itself and his book, ‘Functional Safety in Practice’ draw upon his experience in developing a ‘fit-for-purpose’ approach, with the focus on meeting the duty holder’s practical needs, rather than some theoretical ideal.

HTS Engineering Group Limited

HTS Engineering Group (HTS GRP) specialise in delivering Process Safety and Electrical, Control & Instrumentation (EC&I) systems. Their services are focused on Instrumented Control and Safety Instrumented systems. The group’s core skills are rooted within the engineering services sector from conception through to hand-over. They are a dynamic company delivering the highest level of engineering and expertise combined with efficiency.

HTS Engineers have been developing and implementing safety systems and the IEC 61508 & IEC 61511 standards for major Petrochemical, Oil & Gas and manufacturing organisations for consultancy, engineering & design, system build and construction.


How it works

SISSuiteTM uses a ‘per seat’ pricing model. This works by you, the account holder, creating an account which takes 1 seat. Once you have created a company account, you can add extra users with each user requiring a single seat to use SISSuiteTM.

For more detailed pricing information please email or call 01928 238 360.

Free demo

Please get in touch to book a free demonstration of SISSuite

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SISSuiteTM Limited

The Heath Business and Technical Park


01928 238 360