Estimating the loss of steam via passing valves

[Razif]

Hi,

I am trying to come up with an estimate for the steam losses in my plant through the numerous passing steam trap bypass valves and some leaking (corroded)steam tracing lines. Is there a quick formula that can be used based on the pressure of steam, the size of the opening/hole/bypass line size and the length of the emergent steam jet?

Any ideas/guidance would be appreciated. Thanks.

RR

RR

 

[hacksaw]

you should repair all traps and leaking valves not analyze them.

 

[25362]

Hacksaw is right. With the skyrocketing cost of a barrel of crude oil these days, the potential for improvements in the energy consuming field has increased markedly.

The two areas where the managing of energy is involved are:

1. energy production and distribution.
2. energy usage within processes, generally the most important of both.

The ultimate objective of a good energy management is to reduce operating costs through the efficient use of energy of which, no doubt, repairing leaks is an obligatory housekeeping measure. This objective is more important than simply to reduce energy consumption.

The various fields where one can start improving economies in energy consumption by good housekeeping are:

1. Steam systems.
2. Insulation.
3. Heat exchangers and heaters.
4. Pumping and compression.
5. Electrical systems.
6. Compressed air systems.
7. Cooling water systems.
8. Vacuum systems.

For the estimation of steam leaks visit table 4 of

http://www.ceere.org/iac/assessment tool/ARC2213.html

I'm sure a Google search would render more useful results.

 

[davefitz]

As long as the upstream steam pressure is more than 15 psig and you a re discharging to ambient pressure , there will be choked flow in the leakage hole, so the downstream jet length is not relevant. However, for choked flow through a square edged orifice, the thickness of the square edged device ( t/d) has an effect on the Cd used to calculate the flow. For a t/d less than 4, use a Cd= 0.82

 

[Razif]

Hi,

Thank you for all your replies. I agree that good housekeeping is mandatory. However, I need to put together some concrete figures to convince management that the outstanding 'little' jobs go a long way in saving us energy.

Thanks for the link 25362, its very helpful.



RR

 

[Razif]

I have one more query........

Is it even possible to replace the steam trap bypass valves on the run? There is no way of isolating the steam to the traps in question without isolating the steam header it serves, and isolation of the header is not a possible option. FYI, the steam header is used for steam tracing and tank heating in a tank farm of a refinery.

RR

 

[katmar]

Razif,

This is not really answering your question, but it may be worth considering as you replace your trap bypass valves.

I always try to convince clients to have the downstream side of the trap "bypass" valve discharging to grade. This allows it to perform the function of a bypass, while giving two advantages.

Firstly, you can see what is being discharged so that you can judge how wide to open it while the trap is out for maintenance. And secondly, if it is leaking or is being used for an extended period while Maintenance drag their heals repairing the trap the losses are very visible.

The condensate is of course lost with this arrangement, but overall I believe the losses are much less because it is obvious when maintenace is required, or when a bypass has been left open.

 

[kdt]

Razif

Some steam trap companies will come and do a steam trap audit for you for a minimal cost (sometimes free).

You will be provided with a breakdown of where the losses are located, quanity of steam at each location, cost, and more likely than not the model number and cost for their valve/trap which will correct your problem (along with fancy payback curves, etc).

Your job is then to determine what is correct for your company.

This may or maynot be an option depending on your location.

 

[khan101]

Do you have a flow meter on this line which measures normal steam flow? If not then try an ultrasonic meter.

 

[Razif]

Thanks once again for all your ideas.

I will check to see if the steam trap supplier is able to do a steam trap audit, kdt. It would be great if they can.

khan101, there isn't a flowmeter installed, and there currently is'nt an ultrasonic flowmeter available in-house, but I'll keep in mind if required.



RR