Processing plants are built by investors in order to satisfy the identified market needs and create a positive return on investment within a reasonable time. Key-driver for business owners and operators is to achieve this with a minimum of investment costs and operational expenses. By smart consideration of the options for pressure safety devices considerable reductions of loss (due to cost or environmental/health issues) of media or capital investments cost for equipment can be achieved. This typically results in ongoing cost savings beneficial for the investors and operational organizations of industrial processing plants.
The Ongoing Search for Cost Controlling
The economic reality in running industrial processing plants is to maintain the operational cost within the budget, even when unplanned or unscheduled events take place. The total cost of ownership (COO) of the processing plant is therefor to be optimized continuously. A major cost driver will often be the quality of selected materials of construction of processing equipment. Where extensive corrosion issues need to be handled, often a selection of non-standard materials of construction may need to be considered to achieve the intended service life. The use of such preferred “exotic” materials, especially where adequate compliance to operating pressures is mandatory, may escalate the initial investment costs whilst affecting the ongoing cost of ownership (maintenance and repair, spare parts, etc.).
Where the processed media creates concerns with regards to human exposure (health issues), environmental issues (high risks for impact on the fauna or flora) or has high value for the market, minimized leakages of processing equipment may need to be considered and maintained.
With regards to overpressure protection needs often an initial choice will need to be made between the use of either reclosing or non-reclosing devices, whilst considering the specific features and issues related to these optional solutions. Reclosing devices, commonly referred to as pressure relief or safety relief valves, may be preferred due to the fact that they allow the process to continue after successful relief of the overpressure. In situations where an overpressure event is found to be rare, or where highly corrosive media are involved or where large relief capacity is required, non-reclosing pressure relief devices – commonly referred to as rupture or bursting discs – are often selected. Rupture disc devices provide rapid pressure relief, are available in a wide range of materials, sizes and set pressures. They are generally recognized, by industrial safety specialists, to offer the highest possible levels of reliability and safety available to the industry.
Where industry processes are required to have overpressure protection, the selection of pressure relief valves often may lead to specific challenges. Pressure or safety relief valves are generally available with “industry acceptable” leak rates, whilst the standard materials of construction are limited to carbon steel and stainless steel grade.
Where improved leak tightness is required, special executions may need to be considered whereas the process parameters such as material compatibility, temperature, etc. may be restrictive or affect the investment costs for these critical safety devices. Where non-standard materials of construction for the pressure relief devices are intended the reduced availability of such preferred materials may result in extensive investments and/or lead time issues.
Understanding the Total Picture
In the search for the best pressure safety solution the considerations are often limited to the initial cost of the investment of the pressure relief device. Additional or hidden costs are often overlooked in the initial selection phase. The total cost of ownership for equipment, including pressure safety devices, needs to include Capital Processing Equipment Expenses (CAPEX), installation and maintenance costs, cost of spare parts, downtime and costs related to personnel training and management of change. As legislation will require the pressure relief valve to be regularly calibrated and checked for proper performance, the related downtime and handling needs to be budgeted for. Where unanticipated or underestimated costs are surfacing, alternative system improvements can be made to reduce the relevant maintenance costs and operational impacts. Cost-optimization is indeed an ongoing exercise without jeopardizing quality and the level of required safety.
Where the initial investment cost may be reasonable, extensive maintenance efforts due to, for example corrosion of critical items such as pressure relief valves may be a shocking reality.
Furthermore, the loss of product/media through leaking pressure relief valves and resulting corrosion of critical downstream equipment may also dramatically increase production costs whilst stretching the running cost of the process as well as putting a continuous load on the emergency handling system (flare, scrubbers, etc.).
The Solution – Pressure Relief Valve Protection
The combination of rupture discs and pressure relief valves offers an ideal solution for many situations in the industry where cost of ownership is an issue. The upstream installation of rupture discs at the inlet of pressure relief valves provides a physical isolation where the corrosion of the valve internals whilst also eliminating any product leakage to the atmosphere.
Furthermore, through the presence of the upstream rupture disc, in-situ testing of the pressure relief valve can be applied. By introducing a small amount of pressurized media (nitrogen) into the interspace created between the rupture disc and the pressure relief valve seat, the correct lifting of the valve – and therefore its correct set pressure – can be verified. This will eliminate the need to shut down the process entirely, as well as allow for the intervention to be reduced to minutes instead of days.
The combination of a rupture disc with pressure (or safety) relief valve is a recognized industrial solution, described in the leading global engineering and safety standards such as API, ASME and European PED legislation. Hundreds of industry users have, over past decades applied this successfully, whereas renowned engineering houses have implemented this as a standard solution. A large amount of demanding applications has been successfully addressed by using this solution.
The total cost of ownership of many production plants can be controlled through the inventive use of rupture discs and pressure relief valves in combination. Not only can initial investments be reduced, without jeopardizing the system safety level, but maintenance costs, downtime and spare parts can also benefit from the smart use of these readily available standard products. Fike’s ValveGuard offers the widest array of benefits to the industry, helping conscientious stakeholders to keep their operating costs under control whilst improving the overall safety of their processing plants.