The accident occurred on Friday 6/14/2013 at around 6 p.m. in a section of the plant that had been shut for maintenance when a nitrogen vessel ruptured during off-loading. The blast killed one worker and sent seven others to the hospital. OSHA investigated and issued the following 5(a)(1) citation regarding the design of the process (not PSM) as it relates to pressure ratings and relief system design.
The employer did not furnish employment and a place of employment which were free from recognized hazards that were causing or likely to cause death or serious physical harm to employees in that employees in the Ammonia 3 Unit of the XX XXXXXXXXX Complex in XXXXXXXXXXX, Louisiana were exposed to struck-by hazards while operating the Nitrogen Supply Distribution system and its attached components.
Instance 1
The employer failed to ensure the adequacy of the relief system.
a) Gates Terminator 3202T hoses, rated for 500 psi were installed in a system that could see pressures up to 10,000 psi.
b) CETCO manifold rated for 6000 psi was installed in a system that could see pressures up to 10,000 psi.
c) Speed Catalyst manifold (Texas Pneumatics Tools Model #TX-2AMF) rated for 200 psi was installed in a system that could see pressures up to 10,000 psi.
d) Generant Model 4-GDR-1000-EP-C pressure regulator rated for maximum inlet pressure of 400 psi was installed in a system that could see pressures up to 10,000 psi.
e) A 1″ ball valve that is rated for 3600 psi was installed in a system that could see pressures up to 10,000 psi.
f) Mercer 91-17D51P56E1 pressure relief valve rated for 6000 scfm of relief at 3000 psi was set to open 5000 psi and undetermined relief rate was installed in a system that could see pressures up to 10,000 psi and flow rates up to 3000 scfm.
Feasible and acceptable methods of abatement of this hazard include, but are not limited to the following:
1) All pressure vessels other than unfired steam boilers shall be protected by a pressure relief device that prevents the pressure from rising more than 10% or 3 psi, whichever is greater above the maximum allowable working pressure (UG-125(c) of ASME BPVC Section VIII – Division 1).
2) The spring in a pressure relief valve shall not be set for any pressure more than 5% above or below that for which the valve is marked, unless the setting is within the spring design range established by the valve Manufacturer or is determined to be acceptable to the Manufacturer (UG-126(c) of ASME BPVC Section VIII – Division 1).
3) The aggregate capacity of the pressure relief devices connected to any vessel or system of vessels for release of a liquid, air, steam, or other vapor shall be sufficient to carry off the maximum quantity that can be generated or supplied to the attached equipment without permitting a rise in pressure within the vessel of more than 16% above the maximum allowable working pressure when the pressure relief devices are blowing (UG-133(a) of ASME BPVC Section VIII – Division 1).
4) Design the spring so that the full lift spring compression shall be no greater than 80% of the nominal solid deflection (UG-136(a)(2) of ASME BPVC Section VIII – Division 1).
5) A pressure relief device is not required if the pressure is self-limiting and less than or equal to the MAWP of the vessel at the coincident temperature. (UG-140(a) of ASME BPVC Section
VIII – Division 1).
6) The design pressure of each component in a piping system shall not be less than the pressure at the most severe condition of coincident internal or external pressure and temperature (minimum or maximum) expected during service (ASME B31.3-2006 Part 1 paragraph 301.2.1(a)).
7) Adhere to industry guidance, such as but not limited to the Center for Chemical Process Safety (CCPS) 1996 Guidelines for Writing Effective Operating and Maintenance Procedures. Examples of guidance in the CCPS guidelines include:
1) Section 3.10 Procedure Training.
2) Chapter 4 – Writing Operations and Maintenance Procedures.
3) Chapter 5 – Elements of Effective Procedures
Instance 2
The employer failed to ensure the adequacy of the relieving rate.
a) The employer did not ensure the relief device on the CETCO nitrogen distribution manifold was adequate to relieve the delivery rate of nitrogen supplied by the nitrogen pumper unit.
b) The employer did not ensure the relief device on the Speed Industrial Catalyst nitrogen distribution manifold was adequate to relieve the delivery rate of nitrogen supplied by the nitrogen pumper unit.
Feasible and acceptable methods of abatement of this hazard include, but are not limited to the following:
1) All pressure vessels other than unfired steam boilers shall be protected by a pressure relief device that prevents the pressure from rising more than 10% or 3 psi, whichever is greater above the maximum allowable working pressure (UG-125(c) of ASME BPVC Section VIII – Division 1).
2) The spring in a pressure relief valve shall not be set for any pressure more than 5% above or below that for which the valve is marked, unless the setting is within the spring design range established by the valve Manufacturer or is determined to be acceptable to the Manufacturer (UG-126(c) of ASME BPVC Section VIII – Division 1).
3) The aggregate capacity of the pressure relief devices connected to any vessel or system of vessels for release of a liquid, air, steam, or other vapor shall be sufficient to carry off the maximum quantity that can be generated or supplied to the attached equipment without permitting a rise in pressure within the vessel of more than 16% above the maximum allowable working pressure when the pressure relief devices are blowing (UG-133(a) of ASME BPVC Section VIII – Division 1).
4) Design the spring so that the full lift spring compression shall be no greater than 80% of the nominal solid deflection (UG-136(a)(2) of ASME BPVC Section VIII – Division 1).
5) A pressure relief device is not required if the pressure is self-limiting and less than or equal to the MAWP of the vessel at the coincident temperature. (UG-140(a) of ASME BPVC Section VIII – Division 1).
6) The design pressure of each component in a piping system shall not be less than the pressure at the most severe condition of coincident internal or external pressure and temperature (minimum or maximum) expected during service (ASME B31.3-2006 Part 1 paragraph 301.2.1(a)).
7) Adhere to industry guidance, such as but not limited to the Center for Chemical Process Safety (CCPS) 1996 Guidelines for Writing Effective Operating and Maintenance Procedures. Examples of guidance in the CCPS guidelines include:
1) Section 3.10 Procedure Training.
2) Chapter 4 – Writing Operations and Maintenance Procedures.
3) Chapter 5 – Elements of Effective Procedures
Instance 3
The employer failed to ensure adequate relief system control.
a) 1″ Ball valve between the CETCO nitrogen manifold and the Mercer pressure relief valve was not positively controlled to remain in the open position during operation. Among other methods, one feasible and acceptable method to correct this hazard is to ensure that there are no intervening stop valves between the vessel and its pressure relief device or devices, or between the pressure relief device and the point of discharge (ASME BPVC Section VIII, UG-135(d)).
Source: https://www.osha.gov/pls/imis/establishment.violation_detail?id=912440.015&citation_id=01001