Pre-Brew Calibration - Espresso Series

Pre-Brew Calibration - Espresso Series


Pre-Brew Flow Rate Calibration - Slayer V3 & Single Group


Slayer Espresso Series machines feature a precision Needle Valve which controls the flow rate of water during the Pre-Brew phase of an extraction. This flow rate control allows the barista to extract espresso that is unparalleled in flavor and mouthfeel.

However, in order to extract that perfect Slayer Shot you must first calibrate your flow rate! Outlined in this guide is the proper method to calibrate the flow of water through the Needle Valve.

Slayer Espresso V3 & Single Group machines require the barista to manually actuate group positions to enter each brewing phase.
  1. The right, OFF, position is off and does not activate the pump or allow water through the group.
  2. Whereas the center, Pre-Brew, position reduces the flowrate of water and gently saturates the coffee bed.
  3. By actuating to the left, Full-Brew, position. Water bypasses the Needle Valve and introduces the full flowrate of water to extract through the coffee.
In each brewing position. Water is moving through the hydraulic path at 9 bars of pressure. Pre-Brew is restricted FLOW RATE not pressure.
Illustrated brewing positions:



Purpose: 
Calibrate flow rates to be within Slayer's recommended parameters of 40 to 60 grams over 30 seconds. Flow rates outside of the recommended parameters reduce the efficacy of the Needle Valve's unique brewing feature.
Calculating flow rate through the Needle Valve without coffee as a variable allows for precise control over the calibration process. All steps in this guide must be performed with clear water since we are determining a mechanical process of water being forced through an adjustable valve.


Dispensing Full-Brew (Step 2) & Calibrating Flow Rate (Step 4)

Time:
  1. 10 minutes

Tools:
  1. Flathead Stubby Screwdriver
  2. 8oz Vessel
  3. Espresso Scale
  4. Timer (Slayer Single Group's feature a display Pre-Brew timer.)



Step 1:
  1. Remove dispersion screw and screen with flathead stubby screw driver.
This ensures no water is retained by the dispersion screen.



Step 2:
  1. Actuate group to Full-Brew for 5 seconds and allow water to dispense from group.
This clears the hydraulic path of any water which may effect calibration results.

Step 3:
  1. Prepare espresso scale, timer, and vessel.
Step 4:
  1. Start timer and actuate group to center, Pre-Brew, position.
  2. Once timer reaches 30 seconds. Actuate group to the right, OFF, position.


Step 5:
  1. Record clear water yield as observed on the scale. 
  2. Write this number down.
  3. Tare scale and repeat Step 4 two more times for a total of three clear water flow rate tests.



Step 6:
  1. Together, add all three recorded flow rate tests.
  2. Divide this sum by 3.
  3. This is the number Slayer uses to calculate the average yield of water which has passed through the Needle Valve. 
Since water passing through the Needle Valve is a mechanical process and actuating ON and OFF is human reflex. You may experience a variance of +/- 2g after each 30 second cycle. Averages are key to understanding flow rate control!

Step 7: 
Adjust Needle Valve

Needle Valves are precision instruments. It is important to consider the effect incremental adjustments have on the flow of water in addition to internal components.
  1. If flow rates are under the desired clear water yield.
    1. Loosen, left turn, blue knob to open valve.
  2. If flow rates are too high.
    1. Tighten, right turn, blue knob to restrict valve.
Repeat Steps 2 - 6 until desired flow rate is achieved. 

Do not tighten Needle Valves below the 40g/30s threshold.  Important: Over-tightening the valve may damage or break the needle inside. Only adjust the flow rate incrementally.



Additional Resources:

Once your flow rate has been calibrated and Needle Valves adjusted. It's time to brew espresso! 




Questions or concerns? Please contact support@slayerespresso.com

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