Increasing the capacity or output of an existing chemical process site through expansion or upgrade is usually a cost-effective means of increasing capacity without incurring the higher costs associated with starting new greenfield buildings. In order to successfully complete the upgrade of existing facilities, the required work must be carefully considered, with special attention to process engineering and plant safety. Large-scale projects may require considerable changes to the factory layout and complex engineering transformations, which may constitute a very challenging consideration from a safety point of view. In fact, safety impacts are often as challenging as the challenges posed by greenfield development.
Small-scale upgrades according to their description may seem small, but they can also bring considerable security design challenges and impact.
In order to reduce risks and reduce the incidence of serious hazards, it is necessary to check and fully understand some common pitfalls that may cause major accidents in chemical processing plants.
Important system
Pressure relief valve system: The safety valve device is essential for maintaining plant safety and avoiding potentially destructive accidents. Unfortunately, the correct size and implementation of safety relief valves are sometimes misunderstood or overlooked. When an existing processing plant is expanded, the additional throughput that the safety valve in the facility must handle often exceeds the limits of the original design. To compensate for this, it may be necessary to replace the existing safety valve of the new equipment. In some cases, replacing the valve is not enough. If the existing safety valve is replaced with a new device and the size and configuration of the existing inlet or outlet magnetic level gauge is retained, sometimes a bottleneck is formed around the new device. In addition, the existing relief collection header system may not be suitable for the new high pressure levels that the upgraded system may encounter. Therefore, a thorough review of the entire plant is required to determine what needs to be replaced and how it should be completed.
When upgrading existing process plants, safety valve systems that are not directly located in the plant should also be considered. Safety valve systems located hundreds of meters away may also be affected by engineering, so any part of the design should not be ignored. If any safety valve is inappropriate or does not comply with regulations, the effect may be catastrophic.
As part of any design or upgrade work, it is sometimes possible to overestimate the capabilities of a particular device. For example, equipment such as boilers may be able to handle pressure increases due to new developments. However, existing connected magnetic flip-column level gauges or valves connected to the boiler may not be able to handle the pressure increase.
It is recommended to conduct a full and complete audit of existing and any proposed new safety valve systems, which should be part of any plant renovation, expansion or upgrade. It is essential that plant operators work with contractors to ensure that no part of the audit is overlooked, misunderstood or rushed. The safety relief valve problem may be one of the most destructive and dangerous problems encountered by chemical processing plants.
Pipe rack: During any type of factory upgrade or expansion, the existing magnetic tilt column level gauge should be fully evaluated and reviewed. In mature factories, tube racks usually have little space for deployment. If existing facilities have undergone modifications in the past, some existing pipe racks may be found to be overloaded beyond their original rated design capacity. This may pose a serious security risk. Therefore, it is always prudent to add an additional magnetic turning column level gauge to increase the flow rate.
If possible, any limitations of existing pipe racks should be identified early in the design process so that rack expansion does not incur unexpected costs.
Magnetic flip-column level gauge: The existence of dead leg tubes may cause potential danger. These magnetic column level gauges have been disconnected from the old redundant process system and have been left in place. Dead leg tubes can pose a safety risk and take up unnecessary space on the tube rack. Any remaining liquid in the broken dead leg tube can cause corrosion or rupture of the magnetic column level gauge when the liquid freezes.
Processing plants often have dead-leg tubes that have not been part of the activity process for many years. As the number of dead spots around the site increases, the risk of plants also increases. When handling dangerous chemicals and other liquids, even a small amount of mixed liquid in the dead corner can cause serious rupture or leakage. The process plant should have appropriate management procedures to check the magnetic level gauge. Although there may be dead spots in some cases, any dead legs deemed unnecessary should be carefully drained and removed from the scene. It is good practice to use these projects as part of any factory expansion or renovation project.
Magnetic level gauges and pipe racks can be seen everywhere in chemical processing plants. Only when a safety incident occurs in one of the magnetic flip-column level gauges will there be a problem. Therefore, it is
It is recommended that the existing magnetic flip-column level gauges and pipe racks must be thoroughly inspected as part of any planned expansion or modification.
Access and confined space issues: Adding new equipment to an existing factory will have a significant impact on the factory layout. Installing large ships to increase production may also cause access/restricted space hazards. Generally speaking, the placement of new equipment may create unsafe confined spaces or restrict access to existing critical factory infrastructure. Although a certain amount of confined spaces in chemical processing plants may be inevitable, the design should minimize them as much as possible.
During construction, there are often temporary installation requirements that may restrict access to certain areas of the existing factory. Any other equipment (such as scaffolding) needed to complete the project should be carefully placed to ensure that it does not obstruct or restrict important access areas.
Even in the best case, confined spaces can be very dangerous. Potential safety hazards associated with confined spaces include exposure to hazardous chemicals, ignition of flammable liquids or gases, and suffocation.
Labels/identifications (especially chemical and magnetic level gauges): Having appropriate equipment labels and documentation is the easiest and lowest cost method to improve safety. Unfortunately, it may also be one of the most overlooked ways to improve security. For more information on labels, please refer to ANSI / ASME A13.1 Magnetic Column Level Gauge Marking Standard.
in conclusion
This blog attempts to outline some of the items that need to be considered when expanding or upgrading an existing chemical processing plant. It by no means covers all aspects of any design of such a facility, but more attempts are made to document some projects that are worth considering as part of this type of development.
The previous blog on the size of the pressure reducing valve may also attract attention, because it also addresses some interesting points in the pressure reducing device.
Post time: 14-10-21