Don't Forget to Check FA1D56-03-13 Stud Bolt When Booster Pump Casing Cover Leaks

Many power plant technicians have dealt with the frustration of breaking or stripping a stud bolt when disassembling the booster pump casing cover, only to have the cover start leaking fluid again soon after reassembly. The problem often lies with an unassuming component: the FA1D56-03-13 Booster Pump Casing Cover Double-End Stud Bolt. This long bolt, specifically designed for the FA1D56 pump, looks simple, but it is crucial for securely locking the casing cover to the pump body and preventing seal failure.

This article explains why this stud bolt is so important and how to handle it during maintenance.

I. Understanding the Role of This Stud Bolt

The FA1D56-03-13 is not a standard bolt; it is a custom-designed double-end stud for the FA1D56 booster pump. It has threads on both ends: one end screws into the pump body, and the other secures the casing cover with a nut. Its core functions are twofold:

1. "Secure Locking": It firmly connects the booster pump casing cover to the pump body. Regardless of the internal fluid pressure or rotation speed, the stud ensures the cover remains stable, preventing leakage through the gaps.
2. "Sealing Support": It provides the "framework" for internal sealing components (like the mechanical seal LTJ-8B1D-FA1D56). The seal can only function effectively if the stud bolt applies sufficient compression to the casing cover, allowing the seal components to adhere tightly to the sealing face.

Case Study: One power plant tried to save time by substituting a common carbon steel stud. Within three months of operation, the stud was "stretched and elongated" by the internal pump pressure, the casing cover loosened, and fluid leaked. Examination showed the common stud was slightly deformed. This highlights the importance of using the dedicated stud: it is engineered to withstand the specific pressure and vibration characteristics of the FA1D56 booster pump.

II. Why is This Stud So Robust? Three Key Design Points

The FA1D56-03-13 bolt's ability to "handle the job" in a power station relies on its technical design:

1. Optimal Material Selection: 40Cr Steel—Hardness Meets Toughness

This stud uses 40Cr alloy structural steel, not common steel. The steel undergoes quenching followed by high-temperature tempering (known as "quenched and tempered treatment" or Q&T), making it act like "steel-reinforced concrete"—both hard and tough. It is highly resistant to breaking under tension (tensile strength is over 50% higher than ordinary carbon steel) and resistant to bending. Even if internal pump pressure occasionally exceeds the limit, the stud won't snap.

Furthermore, it is high-temperature resistant. When the booster pump runs, the area around the casing cover gets hot. A standard bolt might soften and loosen, but the 40Cr steel remains stable, preventing thermal-induced failure.

2. Detailed Manufacturing Process: Rolled Threads for Durability and Anti-Rust

The threads of standard bolts are "cut" (machined), often creating tiny stress cracks at the root that can lead to failure over time. The threads on this stud are "rolled"—a process that presses the pattern into the metal, resulting in stronger, smoother threads that prevent galling during installation.

The surface is also treated with phosphating, providing a protective, anti-rust coating. In a power station environment with high humidity and oil contamination, this protection prevents rust, extending the stud's service life by 60% compared to untreated studs, closely matching the lifespan of the mechanical seal and reducing frequent replacements.

3. Strict Quality Control: Checking Every Step from Raw Steel to Finish

Reputable suppliers, such as DONGFANG SRI, maintain rigorous quality control starting with the raw steel—the material must have a qualification certificate, and its composition must be sampled and verified. Heat treatment is controlled by computer to ensure zero deviation. Finished studs are inspected for thread accuracy and cracks, and even test-fitted on a simulated pump to ensure a perfect match with the FA1D56 casing cover and nut, preventing installation issues or insufficient tightening.

III. How to Use During Maintenance: Three Scenarios

The FA1D56-03-13 stud is frequently involved in maintenance. Usage differs across scenarios, so technicians should note these points:

1. New Unit Installation: Torque Symmetrically, Don't Rush

Stud bolts must not be randomly tightened during new pump installation. First, clean the stud and the cover holes. Then, use the "symmetrical, multi-step tightening" method:

• First, lightly tighten all studs to 100 N·m (approximately hand-tight).
• Then, increase the torque in three stages to a final value of 400 N·m (using a torque wrench).
• After each step, visually check that the studs are straight and not warped.

The sequence is also important: The studs must only be tightened after the pump shaft sleeve FA1D56-01-06 is installed. If the shaft sleeve is not correctly positioned, tightening the studs might damage other components.

2. Routine Overhaul: Three Checks and One Replacement—No Shortcuts

The stud bolt must be thoroughly inspected every 12,000 hours of operation (roughly once a year):

• Check Threads: If the thread profile is worn down by more than one-third, or if the threads are visibly distorted, replace the stud immediately.
• Internal Inspection: Use ultrasonic flaw detection to check for internal cracks (even cracks as small as 2 mm can be detected).
• Measure Length: If the stud is 0.1% longer than a new one (e.g., 1 mm longer for a 1 meter stud), it has been stretched and must be replaced.

Additionally, if the Centrifugal Pump Bearing FA1D67-02-03 is worn out, causing excessive vibration, the stud must be carefully inspected to ensure it hasn't shaken loose.

3. Emergency Repair: Fast Replacement, Quick Torque—Time is Critical

If the casing cover is leaking, you must check the stud bolt in addition to replacing the mechanical seal: a stud that won't turn might be stripped; one that feels loose might be broken. Both require immediate replacement, ideally completed within two hours to minimize impact on power generation. When replacing, remember to clean the cover flange face—a deformed flange face will prevent the new stud from being tightened securely.

IV. Stud Bolt "Essential Partners" List: Do Not Use Alone

The FA1D56-03-13 stud cannot work alone; it must be paired with the following components. Technicians should stock these parts together:

Final Practical Advice

Do not underestimate the FA1D56-03-13 stud bolt. It is the "lock" of the booster pump; if it is not secure, the entire pump is vulnerable to failure. Always purchase from a reputable supplier, such as DONGFANG SRI, and avoid cheaper, non-specialized alternatives—saving a small amount of money can lead to a major incident. Follow the correct inspection and installation procedures during maintenance, and this stud will help you prevent many problems and ensure the booster pump runs smoothly.

HKCYT-2025-10-30