/ March 2021

Total Cost of Ownership in Isolation Valves

Per Paloma Melo and Alejandro Plazas

The total cost of ownership is a concept that has been talked about for a long time in the industrial sector, both for analyzing new projects and for evaluating the maintenance costs of different units. In valves, it has been increasingly used to compare different solutions and choose the one with the lowest total cost.

One of the great challenges of the analysis is how to apply it to different processes, industries and equipment in a specific way, that is as close as possible to reality and that its results allow evaluating different solutions to specific problems and reliably.

ValvTechnologies has been working alongside its customers to generate this type of analysis for isolation valve applications in different industries and provide recommendations for its implementation.

To start, it is important to define what are the failures of the isolation valves in the processes that will be part of the analysis:

Leaks through the rod: fugitive emissions into the environment.
Internal leaks from the seats when the valve is closed.
Valve blockage: this can be the most complex, because if the valve that is to isolate a process does not move, the consequences can be catastrophic. Mainly in ESDVs Emergency Shutdown Valves and BDVs (Blowdown Valves).

The main purpose of the TCO analysis is to assess all costs associated with a specific piece of equipment over a period of time. These costs will include: equipment acquisition cost, equipment maintenance, repair and replacement costs. In addition, the base parameters that will be part of this analysis must be defined, listed below.

Definition of analysis time interval: a time interval must be defined so that the economic effects of the valves can be fully analyzed. The recommendation is to use twice the time of the operational window, or the scheduled maintenance cycle, or plant shutdown. Time is a determining factor for the analysis result.

Definition of the quantity of analyzed valves: the recommendation is not to analyze more than 4 valves, as they can have very similar diagnoses and this makes it difficult to understand what the real effect is on the plant and the best way. Also, make sure the effects of the valves have some relationship to each other and are part of the same process.

Maintenance cost (purchase, repair, replacement, maintenance)

The idea is to calculate the initial cost of valves, preventive maintenance, replacement repair; as well as how often it is repaired, replaced, plus installation costs over the analysis time frame.

Installation costs may be insignificant, but it is always important to evaluate them, as additional elements will often be needed, contracting third-party companies, heat treatments, etc. For example, in offshore applications (FPSOs, platforms), the cost of installation and transportation can be so high that it approaches the cost of the valve.

The economic evaluation performed for the purchase of a valve generally considers maintenance costs, but there are also other costs related to valve failures such as:

Unscheduled downtime costs

It is very important to focus the analysis on stops made to change valves and that are not part of a scheduled stop to intervene in the unit or system. An example of an unscheduled shutdown caused by a valve is when its failure creates a high safety risk for the environment, people or equipment.

The first thing is to define whether the process should be stopped completely to change the valve, to reduce load and production, or if it is a process Batch, where the cycle time is extended to make the intervention.

After defining the type of stop, it's time to quantify the costs. The recommendation is to start with the cost per stop day. This is a cost that all companies have and values can change significantly from one process to another. From the daily cost, it is possible to calculate the stoppage value per hour and use this value for analysis, multiplying it by the number of hours needed to intervene in the valve.

Costs related to efficiency

This analysis is one of the most complex because it requires a high level of process knowledge to determine the effects of isolation valve failures on the system. There are several strategies that can be used to determine the cost of valve leaks. Here are some specific cases:

Increased fuel consumption: if boiler drain and vent valves leak in generation and cogeneration plants, the energy used to heat the water is lost, since steam does not reach the turbine. This will directly affect the plant's thermal efficiency and fuel costs. There are strategies to measure energy loss mbtu/hour, such as ValvPerformance Testing (ValvTechnologies leak measurement service).

Increased operating cycles in applications in Batch. In gas dehydration with a molecular sieve, the valves are used to change the operation of the drums to operate in the adsorption or regeneration process. In this process there are different fluids: wet gas (inlet), dry gas (outlet), hot gas (used for regeneration), hot wet gas (after regeneration) and the mixture of these fluids will affect the operation of the system:

Mixing wet gas with hot gas: it will reduce the temperature of the hot gas, affecting the regeneration process, which means an increase in the dehydration cycle.
Hot regeneration gas mixture in the adsorption process: will reduce the sieve's ability to dehydrate, increasing cycle time.

Increased stop time due to valve leakage. In a refinery in the bottom system of fractionation towers with two pumps, which must be changed periodically for maintenance, failure of the isolation valves will generate a considerable increase in downtime.

There are many other costs that can be associated with isolation valves, however, with those exposed above, a conclusive analysis can be reached.

ValvTechnologies has already developed several total cost of ownership studies in different processes and industries such as PIG Launchers and Receivers, Molecular Sieves, ESDVs and BDVs, Gas Injection (API 10,000), among others, with a specialized technical team to develop this type of analysis for your customers.

ValvTechnologies, an American company that has operated for over 30 years in the market, exclusively manufactures valves for severe service, with metal-metal seat, zero leakage according to ISO 5208 Rate A and offers up to 4 years of factory warranty.

Below is an example of the results of this type of analysis and how to interpret it

Practical example: total cost of ownership for molecular sieve dewatering system application

Solution A

Rising Stem Ball Valve;
Valve needs maintenance every year;
Operational window: 6 years;
Cost of stop $50K USD per day;
Stop time for valve change: 24 hours;
Valve starts to leak significantly after 6 months of operation;
1.5 minute increase in cycle due to valve leaks.

Solution B

ValvTechnologies zero-leak ball valve, supported by the seat;
Operational window: 6 years;
Stop cost $50K USD per day;
Valve replacement: every 8 years;
Downtime for changing valves 1 and 2: zero, as the replacement is performed during the unit's programmed stops;
No cycle increase per leak.

Analysis time: 12 years, equivalent to two operational windows.

In the graphics, you can compare the solutions considering the different costs. Figure 1 shows the comparison of initial costs of acquisition, maintenance and replacement of valves at the time of analysis. Figure 2 shows the comparison of acquisition, maintenance, replacement and unscheduled downtime costs for valve replacement. Figure 3 shows the costs of initial acquisition, maintenance, replacement, costs of unscheduled shutdowns, and, additionally, the cost of incrementing the cycle due to valve leaks.

Analysis result:

12-year total cost of ownership for Solution 2 is 3.5% of the total cost of ownership for Solution B (Fig 3), despite having a higher initial investment.
The reduction in the total cost of ownership with Solution B is because there is no added downtime costs or increased cycle times.

This analysis can be applied to other processes and industries, such as:

PIG launchers and receivers
Petroleum Coking Units
Molecular Sieve Dehydration
Instrumented safety systems
Fractionation tower funds
Catalytic Cracking Units
ESDVs and BDVs
Gas Injection (API 10,000).