Abstract
Pigging Operation is high risk activity in-terms of process safety. Pigging can be safely initiated only when safe operating conditions are maintained at both ends of pipeline. Pigging involves human intervention and thus increasing personnel risk. Deploying smart, keyless system solutions on this fully manual operation for control and safety will definitely enhance safety level. NPCC presents their design and implementation experiences of smart keyless system for pigging on a recent offshore project.
Pigging involves sequential steps and imposes safety risks due to possibility of manual errors; since, significant number of steps and checks involved. High pressure, flammable/toxic gas release may leads to Catastrophic Personal, Asset and Environmental damages. Traditionally, mechanical key interlocking mechanism or similar mechanical safety interlocks deployed, which has inherent deficiencies like mechanical failures, key loss, minimum intelligence/ operator guidance. Ultimate aim is to ensure no pressure/ toxic gas inside pig-trap when opened for inserting/removal of pig-tool. Implementing smart keyless system with safety interlocks overcomes the shortfall of existing system with reliability. Safe methodology ensured through Risk based Assessment.
Pipeline pigging is required mainly to maintain pipeline efficiency, avoids potential flow-assurance issues and helps in corrosion control/integrity. The key design parameters are:
MOV configuration:
As the operation involves a number of MOVs (around 13 MOVs per Scrapper), a 2-wire digital loop was considered with hardwired permissive signal at suitable steps.
Control System configuration:
Entire operation is guided by Graphics in local field-mounted HMI involving sequential logic check as well as operator acknowledgement before proceeding to next predefined step. The position status of MOVs and Pressure conditions are used in the system logic for authorization to proceed to next step.
Safety Interlock configuration:
Safety critical checks implemented as hardwired permissive signals for MOV operation. Interlock prevents operation of MOVs, both from Local and Remote unless the safety conditions are met.
Although Pigging is a safety critical sequential process, this smart, keyless, system based sequential Pigging not only resulted in significantly safer operation, provides operator guidance and eliminates error/ negligence. This smart keyless system successfully designed, implemented and tested (FAT, IFAT & SAT) and currently in operation with Client's satisfaction. Automatic logging of pigging operation and reporting are available.
Smart keyless system based interlocks is the integral part of this novel solution and allows the high-risk pigging process to be performed safely with added convenience and security of an electronically integrated system. This paper intends to present a case study based on actual project, highlighting design challenges and experience gained during execution as well as providing HSE benefits to all stakeholders in the upstream hydrocarbon industry.
