Showing posts with label steam. Show all posts
Showing posts with label steam. Show all posts

Thursday, May 14, 2020

Mitigate Hammer in Flashing Condensate Return Systems with Vertical Riser Piping


TLV Consulting and Engineering Services constructed a clear piping system to visualize the complex bi-phase flow within a steam condensate return system to determine if water hammer can be reduced or eliminated in certain less-than-ideal piping configurations.  Sometimes, condensate returns are incorrectly considered to be single-phase flow, but in reality the pipe volume can be primarily filled with flash steam. This creates a two-phase flow condition that presents challenges to the desired action of gravity drainage. Elevation changes in 2 phase condensate return lines are particularly prone to creating condensate backup which can lead to damaging water hammer. The damage can be particularly severe due to the magnitude of condensate mass present as the pipe size increases in diameter.

Two scenarios are examined. First is a commonly seen piping installation of flashing condensate with a vertical rise. Wave action can be seen in the top pipe. It is caused by high velocity steam moving over the surface of the liquid gradually forming waves within the pipe. When the wave grows large enough, it momentarily seals the cross section of the pipe, building a pressure wall behind it. This causes a slug of water to be sent down the line, potentially causing serious damage to piping, valves, gaskets or fittings.

Additionally, in a flashing condensate line, the vapor space is occupied by low energy flash steam which can collapse and generate hammer as condensate rushes into fill the void. In this video, the vapor is non-condensing air, so the violent back slam of condensate filling an instantaneous void is eliminated for safety purposes. The second video introduces a non-ideal method incorporating a drop down loop seal (or DDLS)to help mitigate some water hammer effects. The ideal solution is always to incorporate gravity drainage in the flashing condensate return system design. However, when gravity drainage was not accomplished during the original design, the DDLS may reduce hammer and can be evaluated on a case-by-case basis by a professional engineer for suitability and safe operation. Notice the less violent flow draining into the loop where the wave action was occurring in the upper pipe.

This piping configuration minimizes the length of pipe where surging can occur and reduces the mass of potential water slugs. The result can be smoother flow with lessened water hammer. Although the DDLS is demonstrated using a loop with horizontal piping to enable visualization of the vapor/liquid interface promoting upward flow, it is considered that joining two long radius elbows with no horizontal section between them could further reduce hammer.

For more information about proper steam or condensate system design, contact Swanson Flo. Call them at 800-288-7926 or visit their website at https://swansonflo.com.

Tuesday, February 19, 2019

A Visual Understanding of Steam Induced Water Hammer


When improperly drained of condensate in a high pressure steam main fills with condensate and completely surrounds the steam, an implosion takes place causing devastating water hammer.

Draining condensate and keeping it away from the steam by using proper steam trapping equipment will prevent this from happening.

The following video, courtesy of TLV, dramatically demonstrates the principle behind water hammer and its potentially devastating effects.

Swanson Flo
https://swansonflo.com
800-288-7926

Friday, September 29, 2017

Electric Power Generation Using Coal

Electric Power Generation Using Coal
Coal Fired Power Plant
Electricity is generated at most electric power plants by using mechanical energy to rotate the shaft of electromechanical generators. The mechanical energy needed to rotate the generator shaft can be produced from the conversion of chemical energy by burning fuels or from nuclear fission; from the conversion of kinetic energy from flowing water, wind, or tides; or from the conversion of thermal energy from geothermal wells or concentrated solar energy. Electricity also can be produced directly from sunlight using photovoltaic cells or by using a fuel cell to electrochemically convert chemical energy into an electric current.

The combustion of a fossil fuel to generate electricity can be either: 1) in a steam generating unit (also referred to simply as a “boiler”) to feed a steam turbine that, in turn, spins an electric generator: or 2) in a combustion turbine or a reciprocating internal combustion engine that directly drives the generator. Some modern power plants use a “combined cycle” electric power generation process, in which a gaseous or liquid fuel is burned in a combustion turbine that both drives electrical generators and provides heat to produce steam in a heat recovery steam generator (HRSG). The steam produced by the HRSG is then fed to a steam turbine that drives a second electric generator. The combination of using the energy released by burning a fuel to drive both a combustion turbine generator set and a stream turbine generator significantly increases the overall efficiency of the electric power generation process.

Coal is the most abundant fossil fuel in the United States and is predominately used for electric power generation. Historically, electric utilities have burned solid coal in steam generating units. However, coal can also be first gasified and then burned as a gaseous fuel. The integration of coal gasification technologies with the combined cycle electric generation process is called an integrated gasification combined cycle (IGCC) system or a “coal gasification facility”. For the remainder of this document, the term “electric generating unit” or “EGU” is used to mean a solid fuel-fired steam generating unit that serves a generator that produces electricity for sale to the electric grid.