Pipe Line Warm-up Procedure

It's pretty certain that this item will be in the original equipment manufacturer's operation and maintenance manual for the equipment. If it isn't, the telephone number for their technical helpline certainly is.

ASME B31. 1 and ASME I

Normally, in start up conditions, you will open the drains (Main steam lead drains or other terminology for these valves determined by your plant) just ahead of your turbine to remove condensate from the line in order to avoid turbine water induction. Also, by doing this, it allows for a flow path from the superheater to bring temperatures up (hotter) in the steam piping and nearer to the first stage of the turbine. This also helps to begin some prewarming of the turbine which needs to warm up before rolling above a certain speed. These temperatures are monitored especially before latching the turbine (opening the Main Steam Stop Valves) in order to minimize turbine water induction which is detrimental to your turbine. (This temperature is one of your permissives for rolling your turbine.)

Once your unit is synchronized, some drain valves automatically close upon the closing of the generator breaker. Other designs require that you close the drains after a short period of being on-line. By this time, the steam line should be sufficiently heated and all risk of turbine water induction is past.

In case of the unit turbine trip, open drains several rounds to allow them to drain and leave open until back online.

If you are on a hot start up, the lead drains should be wide open. If warm start up or cold start up, they should be throttled somewhat. In all cases, follow your particular equipment's operating procedure. Refer to the Steam tables before admitting steam to turbine as generally 100 degree minimum superheat temperature is required (100 degree above saturation temperature for your steam's condition at the first stage of the turbine). [This allows the steam to pass through the HP turbine without returning to a liquid state.]

Is there any specific rules regarding maximum temperature increments/time ?

Is the temperature increments similar to Preweld heat treatment methods?

There should be design rules which change with each unit. Follow the recommended procedure for your unit. Your company should give you these recommendations in your training material.

As I am only a boiler operator myself and not an engineer, I suggest that you familiarize yourself with the Steam tables and Mollier diagram. Learn how temperature affects the properties of the condensate and steam. The questions that you are asking can be answered to some degree with the steam tables which are derived from the Mollier Diagram. You may also try to research properties of air conditioning systems as the first stage somewhat acts like the nozzle in an air conditioning system and the same formulae (formulas) are applicable.

If you are bringing up the unit, the guidelines for start up should be based on your particular unit. As I said in an earlier post, each system or unit design is different (or at least different from other designs). For more information from us on this, the members on the forum need more information. How big is the unit? How is the unit rated in KW or MW? How many Klbs/hr steam is it rated? Tell us more about the unit. Simply asking these generic questions can vary greatly in their answers... say from a small 30 KW system to a larger 150 MW unit to a 900 MW unit with HP, IP and dual LP turbines. How many turbines does this unit have? Does it use a reheater in the boiler?

Dear Boiler Trainee,

Your question is NOT CLEARLY expressed. You have mentioned "share their knowledge regarding a Superheater line warmup Procedure"

You referred SUPER HEATER and it is inside the Boiler. If you mean the SUPER HEATED STEAM LINE - then the answer is different.

Pl. clarify.

RAJESWARI.

Sorry Rajeswari.

It is a Superheated steam line as mentioned in the title.

I was just gathering knowledge about general procedures like this.

I was after the rules for maximum allowable temperature increments during startup in a superheated steam supply line as it is related with the life cycle of the pipe material.

Thanks