Introduction to Steam

  1. Steam Trap Maintenance and Management

     
    1. Maintenance and Management Guidelines

    1.  

      Maintenance and management of steam traps (hereinafter referred to as "trap management" simply) is essential for improving the management of plant facilities (or all steam systems). It is necessary to understand that steam trap management not only reduces economic loss caused by the deterioration of the steam trap itself, but also prevents the equipment around the steam trap from being affected by the steam trap failure. In this section, we focus on steam traps and describe guidelines for their management.

       
      1. Basic implementation procedure

         

        In order to effectively promote the management of steam traps, it is necessary to clarify the specific management responsible person in charge, and set clear management goals in accordance with the following procedures.

         
        1. 1)Understanding the number of steam traps to manage

           

          Firstly, it is necessary to survey all the steam traps installed in the factory, and perform the following tasks:

           

          ①Attachment of identification tags

          In order to manage the steam traps, it is necessary to clarify the information for each steam trap and trap numbers (Trap No.) are also one of the most important items of information. Thus, an identification tag with trap No. information should be attached to all steam traps.

          Figure 6.1 shows that identification tag made by MIYAWAKI Inc. is made from stainless steel, and lists the management area and trap No.

          image

           

          Figure 6.1 Identification tag

           

          ②Creation of steam trap survey list

          Create a list on which all steam traps to be surveyed are contained. This list is called the steam trap control ledger, or simply the control ledger, and serves as the basis tool for aggregate analysis, etc. (See "Steam Trap Control Ledger" for the required information in the control ledger.) (Please refer to “steam trap survey list” for more detail).

           

          ③Creation of an allocation diagram

          To diagnose steam traps, it is necessary to visit various parts of the plant, but a layout diagram is essential to perform diagnostic work in an orderly and efficient manner and to maintain defective traps.


           
        2. 2)Steam trap diagnosis and record

           

          A diagnosis period is set to diagnose each steam trap, and the results are recorded. In many factories, the diagnosis period is set once a year in the winter when the steam usage increases. Diagnosis is performed by taking the control ledger to the site, diagnosing each steam trap, and writing down the results one by one. Nowadays, however, convenient diagnosis management tools have been developed to automatically diagnose and record the results


           
        3. 3)Aggregate and Analytical Processing

           

          Aggregate analysis is performed based on the diagnosis results obtained in the field. The team trap failure rate and steam loss rate are calculated, and the efficiency of trap management and preset goals are evaluated.

          For example, by comparing with the results for the past two years, it can be evaluated whether the steam trap failure rate is decreasing and whether targets are likely to be met.

          It is also wise to extract those items that have become defective in a relatively short time after new installation, as well as locations and equipment items with relatively high defect rates, including the conditions of use.


           
        4. 4)Actions after result analysis

         

        At least the following tasks need to be performed after aggregate analysis, perform the following actions based on the results and data.

         

        ○ Review and reset the objectives of steam trap management for the next diagnosis

        The objectives for the next steam trap diagnosis should be set based on the assessment of steam trap management from this survey, or reviewed as needed if the objectives have already been set. In addition, the standard of steam trap replacement and maintenance frequency should be reviewed.

         

        ○ Replacement or maintenance of failure steam traps

        Basically, all the failed steam traps found through the diagnosis should be maintained or replaced. However, practically speaking, it is necessary to identify target steam traps based on maintenance and replacement standards, as well as budgetary concerns. What is important in repair and replacement is to disassemble not only the trap to be repaired but also the trap to be replaced to conduct an internal investigation, identify (or estimate) the cause of failure, and record it.

         

        ○ Operation status diagnosis

        It is better to consider the equipment around steam traps too. The discharged pressure (that is, the primary side pressure of steam traps) may be unexpectedly low depending on the equipment. In addition, steam traps and other equipment may not perform well and may be easy to cause malfunction or break down because of incorrect piping. By investigating these conditions, improvements can be made such as replacing with more appropriate steam traps or changing the system of piping. (Please refer to“Precautions when installing steam traps” about piping problems).

         

        ○ Feedback to control ledger

        Through the above actions, the following information are all recorded in the control ledger to be used for future analysis and evaluation, such as the details of the repaired and replaced traps, the name and installation date of the replaced and installed traps, the causes of defects, and the points noticed in the investigation of operation status, etc...

        In addition, it is very important that routine inspections are performed after one or several months without waiting for next regular survey in order to confirm the effects of steam trap replacement and the modification of piping.

      2. Steam trap control ledger

 

The steam trap control ledger is the basic list for maintaining the information necessary for steam trap management such as analysis of diagnosis results and understanding the cost savings of steam trap investigations.

 

Register and create the information necessary for steam trap maintenance and management for each trap. Recording information may differ depending on the method of management or target factories, but it is necessary to record the following information. If it is not recorded, this may cause serious problems for management.

 

① Steam trap No.:this number is set for each steam trap. It consists of digits or combination of digits and alphabetical characters.

 

② Model name of steam trap:this is the model of steam trap

③ Installation location

④ Steam pressure used

⑤ Nominal diameter

⑥ Connections: screwed, flanged and so on

⑦ Set temperature: this is only needed for temperature control trap

⑧ Operation result: May be “good”, “leaking steam”, “blocked”, “shut-down” and so on.

Since the degree of "steam leakage" varies greatly from small to large amounts, it is desirable to further classify it into four or more levels: "small leak," "medium leak," "large leak," and "blowout.

 

In addition, other partially essential items include the application (steam main, trace, equipment installation, etc.), condensate treatment (recovery, release to atmosphere), and the name of the compartment (area name), including the installation location, since large plants can be managed in compartmental units. See Figure 6.4 for an example of a control ledger.