Consultation regarding steam loss issues
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Our company’s steam supply is provided by a third-party heating service provider, with steam being delivered from the boiler room’s steam distribution cylinders to various consumption areas. At the boiler outlet, orifice plate flow meters are installed (used for measuring flow amounts for billing purposes; two meters are used in this system). Flow meters are also installed in each consumption area, either of the orifice plate type or vortex flow meter type. However, the total amount of steam consumed in all these areas amounts to only about 85% of the flow rate measured at the boiler outlet. The loss is abnormally high, and I have a few questions for the experts here: 1. If the pressure at the boiler outlet is saturated steam at 8 bar (gauge pressure), and if the throttle valve in the steam distribution cylinder is opened partially, then the steam delivered to each workshop will have a pressure of 5 bar (gauge pressure) – assuming it remains saturated steam, as the pressure required in the workshops isn’t very high. Will the volume of this steam increase as a result? If the volume does not increase, the saturated vapor densities at these two points differ significantly, and this loss can thus be explained. Does all the lost portion turn into condensate water? Actually, I also thought of another issue: if the volume does not expand after steam pressure is reduced, then when a flow meter is installed after the pressure reduction, won’t the measurement be inaccurate? 2. Besides inaccurate meter readings, what other situations can cause high steam losses? Since I’m definitely a complete beginner, please don’t laugh at me – just give gentle feedback. I am extremely grateful.
I don’t use steam; I think it has nothing to do with pressure. The units of measurement for steam are cubic meters or tons. Have all the flow meters been calibrated? Condensate water is generated during steam transmission, and it is drained at regular intervals along the pipes at lower positions, which is the cause of losses. If the pipeline is long, the amount of steam used is low, and the insulation is poor, there will be significant steam losses. I don’t use steam, and I’m not sure about the number of times it needs to be done; I’m also unsure whether 85% is a reasonable figure
First, standardize the measurement tables, and then standardize their verification. The internal pipe loss of yours is abnormally high.
The level of insulation, the length of the pipeline, whether there are sections buried underground, whether 15% refers to all four seasons or just winter, whether your facility is located in the south or north, whether the pipeline is used continuously or intermittently, whether the pipeline has changes in diameter or many bends, and whether the meter has been verified by a metrology institute – there are too many factors to consider.
Yes, as a settlement table. All third parties have been calibrated at the metrology center. However, there is still a significant difference between their meter and the measuring devices in our own sub-works, so this remains a doubt that cannot be completely ruled out. Can you answer the first question? Does the volume change after this pressure reduction? If nothing changes, the difference in saturation steam density between 5 bar and 8 bar is significant, which also results in a large difference in the calculated steam mass.
The length of each sub-plant does not exceed 200 meters at most, while the shorter ones are around 50 to 60 meters. We are in the south, and it doesn’t only occur in winter. The heat retention is pretty average; it’s not that bad either. We also checked the steam traps on the pipelines; there was no air leakage, and no visible leak points were found. Can you answer the first question? Because, if the steam at the boiler outlet is saturated steam at 8 bar, and it reaches 5 bar in the sub-shop, then according to the law of conservation of mass (with no significant amount of condensate being released in between), its volume should increase. But I just can’t find any relevant theoretical basis for it, because I haven’t studied thermodynamics before; I only have a fragmented understanding of it that I acquired on the fly.
Found it randomly online; the density difference is quite significant
The problem lies in the contractual agreement with the supplier. The installation of measuring equipment at the exit was done under a contract signed with your consent. When it comes to losses, the most obvious ones are the heat loss in the delivery pipeline behind the flow meter, as well as the efficiency during use. All are problems that occur on the side of the user; it would not be appropriate to hold the supplier accountable for these, for reference only.
There’s already a 15% loss allowance specified in the contract; that’s how our company’s contracts are drafted
During steam transmission, there are temperature drops and pressure drops; as the temperature decreases, saturated steam becomes unsaturated, but at the same time, secondary flashing occurs as a result of the pressure drop. So whether condensation appears or not is the result of both insulation and magnetic resistance effects.
P1*V1/T1=P2*V2/T2