8 replies to this topic

[mkhan]

[Dear gentlemen,

Can anybody suggest me, how to calculate condensate rate of medium steam for selecting steam trap , which is distributed through common header at given below condition.

Design temp- 425 C
Design press – 56.4 kg/cm
Line size - 18”
Back pressure app. – 1.5 kg/cm
pipe riser length – 1.5 m
Upsteam piping length – 33 m

With Regards
Mkhan

Edited by mkhan, 26 March 2010 - 09:29 AM.

[latexman]

mkhan,

Are you estimating the heat loss to ambient? If so, you should also specify the insulation. The method I have used in the past is a Q = UA(Delta T). U will depend on insulation and Delta T. What is your coldest ambient T?

[mkhan]

basically i have to select steam trap for above mentioned condition , for that i am calculating condensate rate(load) of medium steam ,in addition to above condition , insulation thickness is 75 mm calcium silicate and ambient temp is about 20 C.

[breizh]

Hi,
You may consider this resource from Spirax Sarco:
http://www.spiraxsar...charge-line.asp
Regards
Breizh

[DUmesh]

Hi,

Please use the following to calculate the warm up rate in a steam line

Mean rate of condensation = Ms = (60*W(Ts-T_amb)Cp/h_fgt
where,
Ms = mean warm up load, Kg/h
W = Total weight of pipe, kg
Ts = Steam temperature, ^oC
T_amb = Ambient temperature, ^oC
Cp = Specific heat of pipe material, KJ/kg-^oC
h_fg = Enthalpy of evaporation at operating pressure, KJ/kg
t = Time for warm up, h

Regards
Umesh

[saeed.s]

I think header design tem (425 c) is very high for Mp steam and also in steam trap selection you do n't need design tem , you need steam tem and usualy Mp steam pressure is about 15 - 17 bar
I presume mps with 15.5 bar and 200 c
We can use this equation :
Q = (A*U*(T1 - T2)*E)/H
Q : condensate rate (Lb/hr) per foot
A : pipe outer area per foot (sqft)
U : Heat transfer coefficent (Btu/sq/ft/hr)
T1 : Steam temprature (F)
T2 : Ambient temperature (F)
E : (1 - insulation effectiveness)( typically 75%)
H : latent heat(Btu/lb)
then : Q = (4.710*3.2*(392-70)*0.25)/828.5 => Q=1.464 (Lb/hr) per foot
with piping length – 33 m ==> Q = 1.464*1005.84 => Q = 1472.54(Lb/hr)
In steam trap selection for header line,safety factor is 2 in the middle and 3 if it sitin the end of line or befor valve. then we should select a steam trap from vendor list with 2* 1472.54=2945.0 (Lb/hr) capacity.For this circumstance ,IB steam trap is best choice ,second choice can be F&t.

[latexman]

That's a lot of super heat! About 150^o C.

I'd use U = 1.1 Btu/lb/^oF/ft²

[Zauberberg]

You can download 3E Plus software from: http://www.pipeinsul...4/download.html and try to calculate what is the heat loss for a given system, based on the input data you have. Calculated heat flow can then be re-expressed as the rate of steam condensation.

You can also do it the other way round i.e. limit the rate of condensation, interface temperature or heat flow by specifying different type/thickness of insulation.

One note: 3E Plus does not work on Vista OS (as stated on the website).

Edited by Zauberberg, 29 March 2010 - 10:11 AM.

[kkala]

I understand this is a steam trap at low end or pocket of main header in order to get it rid of condensate already formed.
Capacity of the trap has to consider both procedures previously presented.
1. Estimate heat losses of insulated header at steady state, then apply a safety factor of 2-3 (see post by behnam).
2. Estimate warm up condensate rate, occurring at start up (see post by umeshdesh).
It is noted that steam trap had better have a bypass line with a hand operated valve.
Is the condensate discharged to the ground or into a collection line? In former case oversizing the trap will not cause operating disturbance (but will increase steam losses, escaping out through the trap).

Edited by kkala, 18 April 2010 - 10:09 AM.