This article is about SAES-L-140 which is about Thermal Expansion Relief in Piping and download SAES-L-140 PDF for piping and mechanical engineers, supervisors and project managers. This is saudi aramco standard based on international codes and standards and useful for piping and mechanical engineering knowledge to get job as engineers, QC Supervisors and QC managers, Engineering managers and technicians.
SAES-L-140 PDF Download
SAES-L-140Thermal Expansion Relief in Piping SAES-L-140
This standard establishes the minimum necessary criteria for addressing the relief of thermal expansion in liquid piping systems when the liquid is confined due to temperature increases. It specifically focuses on the expansion of liquids and does not cover situations where thermal expansion occurs as a result of a fire.
When liquids in a piping system are subjected to temperature changes, they expand. If this expansion is restricted or blocked, it can create excessive pressure within the piping system, leading to potential hazards or damage. To prevent such risks, this standard outlines the requirements for providing relief mechanisms that allow for the controlled release of pressure caused by thermal expansion in liquid piping systems.
It is important to note that the scope of this standard is limited to addressing thermal expansion caused by temperature changes in liquids. It does not address the thermal expansion resulting from fire scenarios, which require separate considerations and specialized measures.
Relief Requirements
The relief requirements outlined in this standard ensure that each section of a liquid pipeline, which has the potential to be fully blocked, is equipped with a relief valve. This valve serves to release pressure when the temperature of the confined liquid rises to a level that exceeds the maximum allowable operating pressure.
To determine the need for a relief valve installation, an evaluation must be conducted for each situation. If it is determined that the resulting pressure from temperature rise could cause the piping to be overstressed, a relief valve must be installed. However, if a detailed analysis is performed using conservative assumptions, and it can be demonstrated and documented that the piping will not be subjected to excessive stress, then a relief valve may not be required.
When conducting thermal expansion calculations, conservative assumptions should be utilized, unless a more rigorous analysis is conducted. These conservative assumptions include:
The pipe section is assumed to be fully blocked in under the following conditions: a) At the ambient temperature or the normal operating temperature, whichever is lower. b) At the highest expected pressure.
Solar radiation of 950 W/m² (300 Btu/hr.ft²) is assumed for a duration of 10 hours on the projected area of the exposed pipe surface.
Any temperature rise of buried or insulated pipelines that typically operate at or above ambient temperature can be disregarded. For refrigerated liquids in buried or insulated lines, it is assumed that their temperature will rise to the ambient temperature after being fully blocked in at the normal operating temperature.
The heat loss from the exposed pipe surface to the ambient environment per unit length of the pipe is determined using equations (1) and (2). The heat loss is calculated considering both convection and radiation effects, taking into account factors such as pipe outside diameter, pipe temperature, and ambient temperature.
By following these guidelines, using conservative assumptions, and performing necessary calculations, the thermal expansion of liquids in piping systems can be adequately managed, ensuring the safety and integrity of the overall system.
- The temperature of insulated lines that utilize steam tracing or any other external heat source is assumed to reach the temperature of the heat source itself.
- The temperature of a liquid in piping connected to the colder side of a heat exchanger is assumed to reach the temperature of the hotter medium within the exchanger.
- The following parameters, at a minimum, should be taken into account when assessing the pressure rise in a pipe due to solar radiation: a) Thermal expansion of the liquid. b) Compressibility of the liquid. c) Pipe expansion resulting from pressure changes. d) Thermal expansion of the pipe.
- No allowance should be made for any leakage from valves intended to provide a tight shut-off, regardless of whether they have metal-to-metal seats, soft seats, or sealants.
A relief valve should be installed in the following situations:
On each section of a cross-country pipeline between main line block valves when the length above ground exceeds 10% of the total length of that particular section.
On each section of buried or insulated pipelines that transport refrigerated liquids.
On the piping within a heat exchanger where a liquid is heated between block valves.
On each section of liquid lines with steam tracing, jacketing, or any other form of external heat source.
By adhering to these additional requirements, the necessary relief measures can be implemented to manage the thermal expansion of liquids in piping, ensuring the safe and reliable operation of the system. SAES-L-140 PDF Download is aramco standard and used for installation of Thermal Expansion Relief in Piping.
Installation Requirements
The installation requirements for thermal relief valves are as follows:
The set pressure of a thermal relief valve should not exceed 110% of the maximum allowable operating pressure for the highest temperature experienced during shut-in conditions. This consideration takes into account pipe hoop stress, combined stress, flange rating, and any other component that may be the weakest link in the system.
The selection of relief valves should be carried out in accordance with the guidelines specified in SAES-J-600.
The placement of relief valves on sections of cross-country pipelines should be chosen to provide the maximum margin above the normal operating pressure, taking into account pipeline elevations and the hydraulic profile. However, the location may also be determined by accessibility requirements. Relief valves that are not situated within a fenced area should be equipped with a suitable cover to prevent tampering or damage, in compliance with Standard Drawing AA-036873.
For thermal relief valves that release flammable or toxic vapors within plant areas, the outlet should be connected to a closed piping system. In the case of oil and other liquids, they may be directed to an entry point of the gravity sewer.
By following these installation requirements, the thermal relief valves can be effectively positioned and connected, ensuring their proper functioning and mitigating potential risks associated with the release of vapors or liquids in a safe and controlled manner.
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