Practical Process Engineering

Now, you should be able to answer these questions readily. The solutions will be posted by tomorrow night.

Pressure drop is 0.2 bar less than expected. Pressure drop and velocity are mutually dependant and both are dependant on pipe diameter. Smaller diameter----> higher velocity----> higher pressure drop Larger diameter----> lower velocity----> lower pressure drop Because calculated pressure drop is smaller, it means pipe diameter is larger than what the process needs (pipe is oversized). Therefore, you can increase flowrate/ velocity to reach 0.4 bar pressure drop or reduce pipe diameter to increase velocity/ pressure drop. Right answer is part b. Part 'a' says steam velocity is higer than expected. If velocity is higher than expected, pressure drop MUST be larger not smaller. It is WRONG. Part 'c' is wrong as well. Because, higher resistance leads to hghier pressure drop. But actual pressure drop is lower than expected. part 'd' is wrong. Larger diameter leads to lower velocity/pressure drop.

Second homework. Solution will be posted by tomorrow night.

Solution: Pressure-Factor Method P1= 10 barg------> factor= 104.4 P2= 9.8 barg-----> factor= 100.75 Pipe Actual length= 1.2*110= 132 m F factor: F= (104.4-100.75)/132= 0.027 Acording to F-factor table for flowrate= 500 kg/h —----> pipe size = 65 mm Alternative solution: Using formula 1 for pressure drop: D= 52 mm Using formula 2 for pressure drop: D=51.58 mm and the standard pipe size to cover this diameter is 65 mm. The right answer is "d".

There are some homework for you. Solution will be posted by tomorrow night.

Also, Spirax Sarco recommends two emprical formulae. Both determines pressure drop, but the second one needs velocity as wells other information. Please note that velocity method is suitable for short runs but pressure drop method is good for long runs. The last recommendation: normal prssure drop= 0.1 bar/ 50 m

Pressure drop chart

Velocity Chart

This is the last part of velocity/pressure drop/sizing based on Spirax Sarco procedure. #Nomogram_Method There are two nomograms applicable to both saturate and superheated steam. a) Pressure drop chart What you have: Steam conditions, steam flowrate and inside pipe diameter What yoy find: Pressure loss bar/100 m so you don't need to know the steam velocity. Steam velocity should be validated to make sure it is in the allowable range. b) Velocity Chart What you have: Steam conditions, steam flowrate and steam velocity What you find: Pipe diameter 👇🏼👇🏼👇🏼👇🏼****STEAM PIPELINE SIZING CHART****👇🏼👇🏼👇🏼👇🏼

How to validate the result: Check the velocity to see whether it is in the range? If yes, enjoy it. Otherwise, the piping should be modified. Pressure factor method is good for the time that pressure drop is constant and maximum allowable pressure drop is already determined. So, the pipe length and diameter should be chosen such that velocity is in the allowable range.

Use F factor and actual flowrate to find suitable pipe inlet diameter from below table👇🏼👇🏼👇🏼

I post some information about a common method for both saturated and superheated steam to determine velocity/pressure drop/ pipe diameter. Before taking the next step for calculation, we should choose the calculation method and acceptable velocity range. 1- For short pipe up to 50 m, size the line based on velocity because the pressure drop is negligible. 2- For long runs, check the pressure drop as well as velocity. The velocity: 1- Should be between 25 to 40 m/s (4920-7872 fpm) for saturated steam. Low velocity as low as 20 m/s (~4000 fpm) is acceptable and, also, higher velocity than 40 m/s would be acceptable providing that the line is short and straight, horizontal and well insulated to make sure the steam is dry. 2- Can exceed above limits for superheated steam, because it is dry and there would be no chance for errosion due to water droplets. #Pressure_Factor_Method What required: 1- Pipe Length (including straight length plus the equivalent lenght because of all fittings, valves, etc.) Here, there are some shortcuts: a) If straight length< 50 m —---> Pipe Length= 1.05* straight run b) Longer than 50 m with a few fittings —---> Pipe length= 1.1 * straight run c) Longer than 50 m with more fittings —---> Pipe length= 1.2* straight run 2- Inlet and outlet pressure 3- Actual flowrate (process flowrate plus the condensate flowrate). Some of the steam gets condensed due to natural heat transfer. Convection and radiation heat transfer should be calculated to know the condensate load. But, choose 3.5% condesate load per 100 m as a rough estimation. Please note that total pipe length MUST be used to calculate actual flowrate not only the length of straight run. Example: How much is the actual flowrate when 100 t/hr steam flows through a 250 m straight run pipe with several bends to drive a turbine. 1.2* 250= 300 m every 100 m produces 3.5% condensate: (300/100)* 3.5%= 10.5% Actual flowrate= 1.105* 100= 110.5 t/hr It means although the turbine needs only 100 ton/hr to operate, boiler should supply to 110.5 t/hr. This is a rough estimation. Pressure factor method employed one formula and two tables to give us the pipe diameter (internal diameter). The tables should be used to find factors for inlet and outlet pressures. Then, calculate pressure factor: F= (P1-P2)/L Where : P1= factor for inlet pressure P2= factor for outlet pressure L= Actual Length

Good Reference👇🏼👇🏼👇🏼 http://www.whatispiping.com/pipe-schedule